LESSON V
CHEMISTRY OF DIGESTION
Alternation of digestive juices
The digestive juices of the human body are five in number, namely: Saliva, gastric juice, bile, pancreatic juice, and the several intestinal juices. Beginning with the saliva these juices alternate, first an alkali, then an acid. It is the opinion of the writer that this alternating plan is carried on throughout the entire intestinal tract, as the final dissolution of food matter takes place in the intestinal canal. These five juices are secreted from the blood by special cells or glands. Each of these juices contain one or more enzyms or digestive principles. These enzyms are highly organized chemical compounds which have the property of changing other chemical compounds without being destroyed or used up themselves except in minute quantities.
Malt and yeast-cells
Malt, which was studied in the last lesson, and which is produced by the sprouting of barley, is a true digestive enzym of the barley. Yeast-cells are minute plants which secrete an enzym that causes the fermentation of bread. It was formerly thought that the fermentation of yeast could not take place except in the presence of a living cell. This has now been disproved, as a German scientist has succeeded in grinding up yeast-cells and filtering off the chemical compound or true enzym which causes the fermentation of sugar.
Fermentation due to enzyms
It is now recognized by scientists that all processes of fermentation and digestion found in plant and animal life are due to definite chemical compounds known as enzyms. The action of digestion is truly a chemical one, and could take place without the body as well as within, if we could manufacture the proper enzym and could produce the exact conditions of temperature, moisture, etc., that are found in the human digestive economy.
Predigested foods
The manufacture of predigested foods depends upon various processes of fermentation, or upon the digestion that may be carried on by inorganic chemical agents, such as acids, or by the ferments of bacteria, or other forms of life. The following are illustrations of these processes of predigestion:
1 The manufacture of glucose from starch by the action of sulfuric acid
2 The malting of starch for the production of malt-sugar or of fermented liquors
3 The making of cheese by the action of the enzym rennet which has been extracted from the stomach of a calf
A great amount of discussion, pro and con, has been raised over the subject of predigested food. The foregoing examples will show that the subject of predigested food, taken in its broadest sense, cannot be dismissed summarily with either approbation or disapproval. We must consider the particular chemical process involved in each case and the final chemical products, as well as its mechanical condition. These things must be taken into consideration when we pass an opinion upon the wholesomeness of a so-called predigested food.
With this diversion to illustrate the breadth and the importance of the action of enzyms, I will now return to the consideration of the chemical action of the human digestive organs.
SALIVA
The saliva is the digestive juice of the mouth. It is secreted by three pairs of salivary glands. The secretions from these three glands are slightly different in Starch digestion in the mouth composition, but for our purpose may be considered as one secretion. The saliva is an alkaline fluid, and the principal enzym that it contains is a starch-digesting enzym known as ptyalin, which can act only in an alkaline solution. As the gastric juice is strongly acid, the digestive action of the saliva is stopped soon after the food has entered the stomach, and the enzym is of no further use. The action of the saliva is very weak, and the amount of starch digestion which is accomplished in the mouth is comparatively insignificant.
Saliva and mastication
The chief function of the saliva is to moisten food and to facilitate swallowing. From these statements one might first infer that the emphasis given to thorough mastication is unwarranted. In fact, the mastication of food has a much more important function than the digestion of starch by saliva. This subject will be referred to again when the physical condition of food as a factor in digestion, and the nervous control or co-ordination of the various functions of the digestive system are considered. (See "Composition of Gastric Juice," p. [147.])
GASTRIC JUICE
Chief function of the stomach
The importance of the stomach as an organ of digestion has been overestimated in modern times. From the discussions in the average text-book and physiology, one would be led to believe that the stomach is the only organ of digestion, when, as a matter of fact, the chief purpose of the stomach is that of a receptacle for the storage of food for digestion further on. I do not mean by this statement that there is no digestive action in the stomach, but I do mean to say that there are no digestive processes completed in the stomach, and that all foods which are acted on by the gastric juice can also be acted on by the digestive juices in the intestines. This has been proved by the fact that surgeons have successfully removed the entire stomach from both animals and men without seriously interfering with the nutrition of the body. They merely had to eat more often, as the depot or storage receptacle had been removed.
Inaccuracy of digestive tables
The stomach should be considered as a preliminary organ of digestion. The tables published in the physiologies giving the digestibility of various foods as so many hours, refer entirely to the length of time it takes for the food to pass out of the stomach. According to these tables boiled rice is given as one of the most digestible of foods. As a matter of fact, the chief reason why rice passes out of the stomach more quickly than other grains, is because it contains practically nothing but starch, and as starch is not digested in the stomach, the rice is passed on to the next station where it can be acted on by an alkali.
Comparison of predigested and uncooked cereals
In this connection it becomes necessary to refer to the interpretation of the experimental results obtained by investigators at the Battle Creek Sanitarium. In these experiments cereal products which had been put through various processes of predigestion were compared with uncooked whole wheat, the contents being removed from the stomach after a given period. The results of this experiment showed a greater amount of starch digestion in the case of the dextrinized or super-cooked foods. These results were published as proof that starchy foods should be put through a process of super-cooking, dextrinization or predigestion. To those who are not familiar with food chemistry, such results would appear very convincing, but to a well-informed food scientist they only illustrate how misinterpretation of scientific facts may indicate conclusions opposed to the truth.
Starchy foods are not intended by Nature to be digested in the stomach, but in the intestines, and the processes of partial digestion of these foods, by artificial means, before entering the stomach, serve only to interfere with Nature's plan, and to deprive both the stomach and the intestines of their natural functions.
COMPOSITION OF THE GASTRIC JUICE
Action of pepsin on proteids
The gastric juice contains three principal enzyms or digestive principles. These are hydrochloric acid, pepsin, and rennet. The hydrochloric acid and the pepsin are secreted by different cells, and could be considered as separate digestive juices, but as the action of one is dependent upon the other, I will consider these actions as one. Pepsin, in the presence of hydrochloric acid, acts on proteids, and changes them into proteoses Peptone and proteoses and peptone. Comparatively little food is completely peptonized in gastric digestion. Proteoses are intermediate products between food proteids and peptone, being the principal product of the action of the gastric juice. Thus it is seen that this stomach-action is only preparatory for the digestive processes of the intestines.
Action of gastric juice on fat
The gastric juice does not act on fat, but in the case of animal food, in which the membranes or connective tissues that enclose the fat-cells are formed of proteid material, the gastric juice sets the fat-globules free by dissolving these enclosing membranes.
Purpose of hydrochloric acid
The chief action of hydrochloric acid in the stomach is to aid the action of the pepsin. Pepsin alone has no digestive power. There are no other acids produced by the secretive glands of the stomach. If other acids are found in the contents of the stomach, it is because they have been taken in with the food, or produced by abnormal fermentation.
How hydrochloric acid is formed
The source of hydrochloric acid is from the sodium chlorid or common salt of the blood. The secreting cells of the stomach-glands are thought to have the power to form hydrochloric acid by uniting the chlorin of the salt with the hydrogen of the water. This is a very unusual chemical process, and has not yet been successfully produced in a laboratory.
Hydrochloric acid as an antiseptic
One of the chief functions of hydrochloric acid in the stomach is that of an antiseptic. In other words, hydrochloric acid kills bacteria. This is not true of all bacteria, for some germs can live in an acid medium, while others may live best in an alkaline solution. The alternation of the digestive juices from alkali to acid is a provision of Nature which has a dual purpose:
1 To reduce food to the finest possible solution; that is, to subdivide or to digest food elements into a form that will admit of assimilation and use
2 To destroy bacteria and enzyms of plant and animal origin that are taken into the digestive tract with food
(These two facts constitute additional reasons for the thorough mastication of food)
Object of alternating digestive juices
By such plan Nature provides for the digestion of food only by such enzyms and ferments as will produce a finished product wholly suited to the particular requirements of the body. When we attempt by artificial processes to digest our food with other enzyms than those of our own digestive organs, or take into the stomach large quantities of food without proper mastication, which causes fermentation, we may expect that the nutritive material supplied to our tissues will not be perfectly adapted to the needs of human cell-growth, and, as a natural result, consequent derangement of the body-functions will take place.
Rennet
The rennet of the gastric juice is primarily for the purpose of digestion. Other than this it has no particular function that has yet been discovered.
Why stomach does not digest itself
The problem as to why the stomach does not digest itself has puzzled scientists for many years. Investigations of the twentieth century have at last solved this fascinating question. The walls of the human stomach are composed of proteid material, and should be dissolved by the gastric juice according to all known chemical laws. The explanation formerly given was that the stomach did not digest itself because it was alive. This answer did not satisfy scientists.
Antipepsin in the blood
There has recently been discovered an enzym, known as antipepsin, which is secreted by the cells in the stomach-walls. This antipepsin destroys the action of the pepsin, thus in turn preventing its action on the stomach-wall itself. Were antipepsin secreted in sufficiently large quantities to mix with the food in the stomach-cavity, no digestion could take place. The presence of this antipepsin in the stomach-walls has been proved in the following manner: The arteries leading to a portion of the stomach-wall of a dog was severed. This portion, receiving no blood supply, did not form the usual amount of antipepsin. The secretion of pepsin went on in the remainder of the animal's stomach, but digested that portion of the stomach-wall which was receiving no blood supply; that is, secreting no antipepsin.
BILE
Function of bile
The bile is a juice secreted by the liver and is alkaline in character. It is collected by the biliary ducts to be conveyed into the duodenum. The most important constituents of bile are bile salts and sodium glycocholate. The chief purposes of bile are to emulsify fats, thus aiding them to pass through the intestinal walls, and to stimulate intestinal peristalsis.
PANCREATIC JUICE
Function of the pancreas
The pancreas is a secretive gland located entirely outside of the intestinal walls, and produces a juice which is poured into the small intestines at the point where the bile enters. Pancreatic juice is acidulous, and also strongly alkaline. As soon as the food, passing from the stomach, comes in contact with the pancreatic juice and the bile, the acid is neutralized, and the mass becomes alkaline.
The pancreatic juice contains three important enzyms:
1 Amylopsin—acts on starch
2 Trypsin—acts on proteids
3 Steapsin—a fat-splitting enzym
Pancreatic juice also has the power of coagulating milk, and is believed to contain some rennet.
Power of amylopsin
Amylopsin, the starch-digesting enzym, appears to be very similar to ptyalin in its power to digest carbohydrates. Amylopsin completes the digestion of starch that was begun by the saliva. It acts on starch with great activity. One part of amylopsin can change forty thousand times its bulk of starch to glucose. This can act only in an alkaline solution, and if any abnormal fermentation takes place in the digestive tract, producing a large quantity of acids, the digestion of starch is stopped. It is interesting to note that this enzym is entirely absent from the pancreatic juice of infants. This explains why infants cannot digest starch.
Comparison of trypsin and pepsin
The second enzym to be considered in the pancreatic juice is trypsin. This is a substance distinct from pepsin, but its action is the same. The chief distinction is that trypsin acts in an alkaline solution, while pepsin acts in an acid solution. Trypsin is much more energetic in its digestive power than the pepsin of the gastric juice. It completes the digestion of proteids that is begun in the stomach, and converts all proteids into soluble forms. A number of forms of proteid that are not acted on at all by the gastric juice are readily digested by the trypsin of the pancreatic juice.
Fat digestion and absorption
The fat-digesting enzym of the pancreatic juice is steapsin. This is the principal fat-digesting enzym of the body. This substance has power to split fats; that is, to convert them into fatty acids and glycerin of which they were originally composed. This fatty acid then combines with the alkalis of the bile and of the pancreatic juice to form soap. Soap is soluble, and passes through the walls of the small intestines in this form. Having passed through the walls of the intestines, soap is again changed into fat. The probable reason for which Nature adopts such a complex process for the absorption of fat, is because fat is insoluble. If the intestinal walls were so constructed that fat-globules could be taken directly through them, they would also be open for the entrance of germs and other foreign substances.
Frying fat unwholesome
Fat is not acted on by the gastric juice. This explains why the process of frying is so unwholesome. Frying causes a thin film of melted fat to spread over the surface of the starch and of the proteid atoms, with the result that these atoms cannot then be properly acted on by the saliva and the gastric juice, and therefore cannot undergo the preliminary changes necessary to normal digestion. Fat, taken in its natural form, does not interfere with other digestive processes.
INTESTINAL JUICES
In addition to the digestive juices that are poured into the small intestines from the pancreas and the liver, there is a juice which is secreted from the walls of the intestinal cells. This is called intestinal juice or succus entericus. It is a light yellow fluid with a strong alkaline reaction, due to the presence of sodium carbonate.
One action of the intestinal juice is to change sugar and maltose into glucose, which is then absorbed directly into the blood.
THE SECRETION OF DIGESTIVE JUICES
Recent discoveries concerning digestive juices
Within the past few years many remarkable discoveries have been made in regard to the secretion of the various digestive juices. Until some ten or fifteen years ago it was believed that the secretion of the digestive juices depended wholly upon the presence of food in the alimentary canal. The recent discoveries in this branch of physiology are to be accredited chiefly to Professor Palloff, a Russian scientist, and his co-workers. The facts that are now known regarding this part of Nature's work are essentially as follows:
The secretion of the various substances which make up the digestive fluids of the body depend upon two kinds of stimuli:
1 Direct nerve stimulus from the central nervous system
2 The chemical stimulus on the walls of the digestive organs
Depending upon either or both of these sources of stimulation, the digestive juices of the body are regulated in quantity, and what is much more worthy of note, in their actual chemical composition. Thus it will be readily seen how far-reaching in its effect upon scientific dietetic treatment is the knowledge of the influence of various foods, quantities, and combinations.
Comparative digestibility of foods
Professor Palloff's discoveries throw some very important light on the comparative digestibility of foods. The former method of estimating the digestibility of food was first to analyze the food, and then to analyze the intestinal residue, and subtract the undigested remnant of each particular class of food from the amount originally eaten. By such means it was possible to show that certain foods were, say 80 or 90 per cent digestible, as the case might be. By this method no allowance was made for the amount of nutrition or material that was consumed by the body in the digestion of these particular foods. According to these investigations, milk and meat were about equally digestible. It was not known that the digestion of milk requires only a small fraction of the energy that is necessary to digest meat, or proteids from vegetable sources. Thus it is obvious that when it is desirable to get a large amount of available nitrogen into the system, with as little expenditure of energy as possible, milk is a food par excellence. This is very logical inasmuch as the sole purpose of milk is food for animal life.
Comparative acidity and energy required in digestion
The amount of acidity in gastric juice that must be secreted for the digestion of meat is much in excess of that required for a given amount of vegetable food. The amount of acidity required is greatest for milk, second for meat, and least for bread. The digestive energy required is greatest for bread, second for meat, and least for milk. From this we learn that starchy foods are unsuitable for those who are afflicted with hyperchlorhydria or supersecretion of hydrochloric acid, as the excess of acid prevents their digestion by neutralizing the alkali of the intestines.
Insalivation of starchy foods and meats
The saliva secreted when nitrogenous food is eaten does not contain as much ptyalin as that secreted when starchy food is consumed; for this reason the thorough insalivation of starchy foods is much more important than that of meat, milk, and eggs. Some authorities have recently advised that people should not chew meat at all, but should swallow it as do carnivorous animals. This advice, however, is not altogether sound. In the first place, man is not a carnivorous animal, and the gastric juice of the human stomach does not act as rapidly on flesh foods as does the gastric juice of meat-eating animals, but if meat be taken into the human stomach, either in large or in small quantities, decomposition may take place before digestion has proceeded far enough to prevent the action of micro-organisms.
Mental influence upon digestive fluids
The mental influence upon the secretion of digestive fluids may originate from thought, or may be brought about reflexively by the sight, or by the smell of food. All are familiar with the experience of having one's mouth water at the sight of a particularly appetizing dish. Many of us have undergone the same experience by merely thinking of some particular food of which we are fond.
Digestive juices vary with different foods
Scientific investigation has shown that the secretion of saliva is only an example of what takes place in the other digestive organs. The experiments of the ingenious Russian scientist, heretofore mentioned, prove that the act of tasting and of swallowing food was the chief factor in determining the secretion of the juices from the stomach-walls. In a series of operations upon dogs, performed by skilled surgeons, certain interesting facts were observed. The esophagus was severed and made to open externally so that the food swallowed did not pass into the stomach. The secretion of gastric juice was then determined in the case of different foods which were taken into the dog's mouth and swallowed, but which did not reach the stomach. Not only did this act of pretended feeding start a flow of gastric juice, but the juice secreted in the case of different foods was especially adapted to the particular food, according to the general principle which we have already discussed.
These facts emphasize several important considerations regarding our diet:
1 We should eat slowly and get the whole taste out of food by thorough mastication, because taste largely controls the secretion of the digestive fluid
2 We should not disguise our food by high seasoning
3 Foods that do not require the same digestive principles should not be taken at the same meal
"Fermentation" and "Putrefaction" compared
Fermentation is the term generally applied to changes that take place in such food substances as carbohydrates, due to the growth of bacteria, while the term putrefaction is applied in a similar way to the changes taking place in nitrogenous or proteid materials. Both of these chemical changes are exceedingly harmful.
ABNORMAL CHEMICAL CHANGES IN THE DIGESTIVE ORGANS
Bacteria chief causes of abnormal changes
Under this heading we will consider the chemical changes which take place in the human alimentary canal, which are not beneficial or necessary to normal digestion. The cause of the most important abnormal changes in the contents of the stomach and the intestines is the presence of living micro-organisms called bacteria.
In the lesson entitled "Evolution of Man," a general survey of the history of man's development from lower forms of life is given. In this general work I do not elaborate extensively upon the method by which evolution proceeds, but those who are acquainted with the writings of Darwin, and other evolutionists, are familiar with the phrases "the survival of the fittest," and "the struggle for existence."
"Survival of the fittest" among bacteria
As we commonly think of "the survival of the fittest" in animal life, we picture the death-struggle of the captured animal, or the fight for food in times of scarcity, or, if it be in the case of plants, the crowding or the struggling for soil and sunlight. We can apply the same principle to bacteria and to other microscopic forms of life.
Bacteria, while minute masses of unconscious protoplasm, are, by the laws of growth and reproduction, struggling for existence just as truly as are the more conspicuous forms of life.
Because of the invariable presence of greater or less quantities of bacteria within the intestines of all ordinary animals, some scientists insist that their presence is in some way necessarily related to the life of the animal, and is probably beneficial.
Experiments proving accumulation of bacteria
New-born animals, however, are free from bacteria, and the bacterial germs found in the more matured animal must, therefore, have been taken into the alimentary canal with food. Ingenious scientists have taken new-born guinea pigs, and have kept them in sterile or germ-proof compartments, giving them filtered air to breathe, and absolutely sterile food. These pigs lived and thrived through the experiment as did their fellows outside the bacterial-proof dwelling. This is considered good evidence that bacteria accumulate in the digestive organs of all animals, not for a purpose connected with animal physiology, but because in order to digest and to assimilate food, conditions are established which are so nearly like those required for bacterial growth, that bacteria are produced, or take advantage of the favorable conditions, just as weeds, if given a chance, thrive in a cultivated field.
Not all bacterial growth is harmful
I have already referred to the antiseptic or germ-destroying properties of the gastric juice, and to other secretions of the digestive organs. This would suggest that the growth of bacteria is undesirable from the standpoint of man's welfare. There are many species of bacteria growing in the human intestines, hence we cannot say with certainty that all this bacterial growth is harmful, as, in order to determine this, the resulting waste-products of each particular species of bacteria would need to be considered separately. We can, however, make the general statement that bacteria are abnormal, or foreign to the human digestive canal, and that their presence is detrimental to human welfare.
Micro-organisms give off various substances as waste-products of their growth, dependent upon the species of bacteria, and the material in which they are growing. Thus the waste-products of the yeast-plant are carbon dioxid and alcohol.
Waste-products of bacterial fermentation
In the alimentary canal there exists an abundance of carbohydrate and proteid substances which form excellent food material for numerous species of bacteria. The substances produced by the growth of these various kinds of bacteria are numerous. They include the gases, carbon dioxid, hydrogen, hydrogen sulfid, marsh-gas or methane, and ammonia. Butyric, lactic, and other acids, together with alcohol, are also produced as a product of bacterial fermentation in the intestines. Perhaps the most detrimental of all are the substances produced by the bacterial putrefaction of proteids, of which indol and skatol are the two most important.
Under ordinary conditions the bacteria themselves do not penetrate the intestinal walls, and their evil influence would be confined to mechanical disturbance of gas in the digestive organs, and to the destruction of a portion of the Solubility and distribution of bacterial waste-products nutritive material of food, were it not for the fact that these harmful and poisonous waste-products I have mentioned, are soluble, and hence pass through the intestinal walls with the digested food material, into the blood, and are thus distributed throughout the body.
It has been observed in the presence of intestinal congestion, where the food lies in the intestines for an abnormally long period, that the amount of these harmful nitrogenous decomposition products excreted by the kidneys, is considerably increased, proving that these products have circulated throughout the body.
Causes of hardening of the arteries
Arterio-sclerosis, or the hardening of the walls of the arteries, which has for many years been recognized by scientists as one of the principal causes of old age, comes from two causes:
(1) The over-consumption of starchy foods, especially of the cereal group; and (2) by the continued presence, in the blood, of small quantities of poisonous material which gradually destroys the protoplasm of the arterial walls, and causes them to be replaced by a degenerate form of tissue.
For example, alcohol and the poison of syphilis are prolific causes of the hardening of the arteries. If the diet were balanced so as to avoid excesses of starch and these toxic substances, the hardening of the arteries would not take place.
Overeating an ultimate cause of old age
The poisons produced in the intestines by bacterial decomposition, superinduced largely by overeating, are absorbed into the blood, and undoubtedly their action is similar to the other poisons herein mentioned. Thus they become a most potent factor in the cause of old age and premature death, being practically universal among all civilized tribes.
Numerous other disorders or dis-eases can be traced to this same general cause, and the subject of the poisonous products of fermentation and decomposition in the intestines will therefore be constantly referred to throughout this work.
The growth of bacteria decreased by scientific eating
From the deductions that have been made it is clearly evident that any system of feeding which will reduce the amount of bacterial growth in the intestines, would be desirable and beneficial to mankind, while foods and habits of life that increase the amount of such poisons are to be guarded against as detrimental to both health and life.
Overeating primary cause of fermentation
Overeating is perhaps the greatest of all dietetic errors in bringing about a condition which favors excessive intestinal fermentation. Overeating causes stomach prolapsus, thus reducing its mixing or peristaltic activity. This retards the process of emptying, called digestion, which is the primary cause of fermentation. Under this condition the antiseptic properties of the stomach-juices are reduced, and the bacteria from the fermenting food is vastly increased. The food, passing from the stomach in a fermenting state, produces gas in the intestines, with the resultant ills that follow, such as vertigo, dizziness, irregular heart action, and usually intestinal congestion or constipation.
THE DECOMPOSITION OF FOOD
Sugar destroys putrefying bacteria
The putrefaction of proteids in the intestines may be reduced by the liberal consumption of fresh sweet fruits. The preserving qualities of sugar depend upon the fact that putrefying bacteria cannot live where sugar is abundant. The beneficial effect of sweet fruits in reducing bacterial decomposition in the intestines, is due to the presence of relatively large quantities of sugar and of organic acids. Sour milk is known to have a prohibitive influence upon putrefaction in the alimentary canal. This is due to the Sour milk a preventive of intestinal putrefaction milk-sugar, which has been changed to lactic acid. This explains why clabbered milk, which contains a considerable portion of sugar changed into lactic acid by the action of souring bacteria, is especially beneficial in preventing intestinal putrefaction. Professor Metchnikoff, of the Pasteur Institute of Paris, became so enthusiastic upon this discovery that he proclaimed sour milk to be a remedy for old age. While Metchnikoff's enthusiasm is perhaps somewhat premature, yet the idea is worthy of much consideration.
Proper feeding chief factor in reducing bacterial growth
We do not need, however, to seek for any one specific remedy against intestinal decomposition, but should study the selections, combinations, and proportions of our food at each meal with the view of reducing to the minimum the growth in the alimentary tract.
DIGESTIVE EXPERIMENTS
It is well known that only a portion of the food taken into the alimentary canal is digested and absorbed into the circulation. It is obvious that the undigested food plays no part in the process of metabolism, therefore it is necessary to know the amount of the various food elements that are digested. For this reason we will notice briefly the method used in making digestive experiments.
Determination of the amount of food the body uses
The food eaten for a certain period of time is analyzed and weighed, and the intestinal excreta, corresponding to the quantity of food under study, is also weighed and chemically analyzed. The difference should show the amount of food actually digested.
There are several serious difficulties in the way of making accurate digestive experiments:
Quantity of feces and time consumed in passing food through the body
1. It is very difficult to determine the quantity of feces (intestinal excreta) that corresponds to a given quantity of food. A digestive experiment is usually conducted for a period of about one week, the man or animal being given a spoonful of lampblack at the beginning and at the close of the experiment. The lampblack being a finely powdered form of pure carbon, is insoluble in the digestive juices, hence passes through the body without change, thus blackening or marking the feces at the beginning and at the end of the test period. The subject under experiment should be given the same diet for a few days before and after the experiment, so that the error due to the inability to accurately separate the feces will be reduced to a minimum.
Measuring the digestible portion of food
2. The digestive juices, and especially the bile, pour considerable material into the alimentary canal which cannot be distinguished from the undigested elements of food. However, it is fair to assume that when large quantities of body-proteids are poured into the alimentary canal, and passed out with the feces, this amount of matter is wasted by the body, hence should be charged against the food which stimulated the secretion. For example: If grain causes a large secretion of digestive enzyms, it is no more than fair to say that grain is less digestible than milk, which wastes less body-matter in its digestion.
Certain foods may either aid or hinder digestion
3. A further difficulty with the accuracy of digestive experiments, and one to which in the past too little attention has been paid, is the influence upon the digestibility of one food by the presence of others. Some foods, such as fruits, aid the digestion of other foods, while in many cases the presence of a certain article seriously hinders the digestive process of all. This emphasizes the great necessity The mono-diet system for observing the laws of chemical harmony in combining our food at meals, and it also emphasizes the importance of limiting the diet to the fewest number of things possible, which in the opinion of the writer will lead inevitably to the mono-diet system, especially in curative or remedial feeding.
Difficulty of determining amount of undigested food
From the standpoint of the above difficulties, all digestive experiments thus far made are only approximately correct, and we are forced back to the conclusion that if we obey the laws of nutrition, Nature will give us her highest result expressed in endurance. If a single article of diet is taken by a man who is accustomed to large quantities of a highly varied bill of fare, the digestive process will not act in the usual way. On the other hand, if several articles such as nuts, grains, and milk are taken at one time, it will be impossible to determine what percentage of the proteid or of the fat from the three various sources remains undigested in the intestinal residue, hence no accurate results can be shown regarding the digestibility of each particular food.
MECHANICS OF DIGESTION
Condition of food influences chemical action
Chemistry is not the only factor in the digestive function that is to be taken into consideration. The mechanical condition of food, when it is taken into the digestive organs, very greatly influences the chemical process that takes place.
This involves the question of masticating or subdividing the food into small particles. The greater the dissolving surface, the more rapidly will solution take place. If the substance being dissolved is Necessity for thorough mastication a firm particle, the digestion or solution will take place only on the exterior surface, and the interior of the particle, however small, will remain practically unchanged. This is what occurs when food materials such as grains and nuts are taken in an uncooked state, as mastication does not dissolve them, but only divides them into small, distinct particles.
Action of enzyms during digestion
If, however, the grain be subjected to prolonged heating with water, partial solution takes place. The entire mass becomes mushy and permeated with moisture. When such a mass is brought in contact with the digestive fluids, it mixes or disintegrates with the fluid, just as molasses would mix with water. The result is that the whole mass of material is subjected to the action of the digestive fluids at once, with the result that the mass is passed from the stomach too quickly, causing congestion in the small intestines, or the whole is arrested, and fermentation and decomposition take place. In normal digestion, the enzyms are continuously secreted for a period of several hours. They begin work on the outside of the food particles, dissolving the substances gradually. Thus the enzyms are continuously used up, and the digestion proceeds slowly, but naturally, yet as fresh enzyms are continuously being secreted to act on the newly exposed surfaces, active and complete digestion is constantly taking place.
Predigested "breakfast foods"
The alleged predigestion of certain proprietary foods has neither scientific basis nor virtue. That the juices of some fruits which are already in the form of glucose, can be immediately absorbed into the tissues without any digestive process, does not prove that the mushy cooking, malting, and other forms of so-called predigestion are beneficial. The so-called "predigested breakfast foods" are not and cannot be prepared by any process for final digestion, but are in an intermediate state between starch and glucose. They are composed of a semi-soluble starch, gummy dextrin, and perhaps a little maltose which has a tendency to disturb and to interfere with the normal process of digestion.
Comparative digestibility of cooked and uncooked starch
I do not advocate the use of uncooked grain, but I wish to correct a popular error in regard to the digestibility of uncooked cereal starch. Nearly all works on physiology and diet make the statement without reserve that raw starch is indigestible. This theory has been established by putting samples of cooked and uncooked starch into two test tubes, and treating them with some digestive enzym. The cooked starch, being soluble, is all exposed to the digestive enzyms at one time, and started on its way through the numerous changes in the complex chemical process of changing starch into glucose, while in the sample of uncooked starch, the digestive enzym attacks the particles from the outside, and slowly digests or eats off the exterior of the starch grains. After a given length of time the chemist adds iodin to the two test tubes. With starch, iodin gives a blue color. In the test tube containing the cooked starch, all of which has undergone a certain amount of digestion, no blue color is discerned, for no pure starch is left, while in the other tube, in which some of the particles remain unchanged, owing to the fact that Nature does all her work slowly, a blue reaction is of course obtained, and the chemist proclaims that uncooked starch is indigestible.
At one of the United States Experiment Stations in the state of Kansas, a comparison of two diets, consisting chiefly of several varieties of grains, was recently made. The diets were alike in every respect with the exception that in one Government experiments with cooked and uncooked grains instance all the grains were boiled for two hours, while in the other case they were taken in an uncooked state. In the case of the uncooked grains, no starch whatever passed through the body in an undigested form. In the case of the cooked grains, the same results were found; that is, no starch was found in the intestinal residue. Other substances, however, remaining undigested in the cooked diet, were much in excess of that in the uncooked, yet no starch was present. In the case of cooked grains, the digestive processes may start with more rapidity than in uncooked grains, yet they are not thoroughly completed, and various decomposition products occur, as well as undigested proteid, which is not likely to occur with foods taken in their natural state.
Uncooked starch harmless
Moreover, if uncooked starch be taken in excess of the digestive capacity, and passed through the body wholly unchanged, no harm results. The starch grain, in its unchanged state, is a fine, white glistening granule, and its presence in the digestive tract would have no harmful effect upon the body functions. Without solution, no material can have any effect upon the physiological processes, except by irritating the mucous surfaces of the digestive organs; in the latter respect, starch granules are harmless.
Condition in which food should enter digestive organs
With the exception of articles that are in solution, the condition in which all foods should enter the digestive organs is in finely divided, yet distinct particles, and not in pasty or gummy masses. In this latter form "bolting" is encouraged, and mastication greatly discouraged.
THE MUSCULAR MOVEMENT OF DIGESTIVE ORGANS
Peristaltic movement in alimentary canal
Another point to be considered in digestion, and which may well be classed under the mechanics of digestion, is the muscular action or peristalsis of the alimentary tract. The best example is the swallowing action observed in the throat of a horse, or of a cow, when drinking. At each swallow, what appears to be a lump goes down the throat. This is a wave-like relaxation of the muscular walls of the esophagus, followed closely by a muscular contraction. This is the action that takes place in the intestinal tract, and that which Nature employs to move the contents along toward the final point of excretion.
X-ray examination of peristalsis
A very fascinating and scientific demonstration may be performed in the following manner: A cat may be given food mixed with some such substance as bismuth subnitrate, which is opaque to X-rays. Upon placing the animal under an X-ray during digestion, this peculiar peristaltic motion can be observed, one "swallow" passing rapidly after another down the alimentary tract.
This method of investigation has also shown that peristaltic action stops immediately in the case of fright, or anger, but is shown to proceed with regularity during sleep, contrary to the antiquated idea that digestion ceases when sleep begins.
Milk for relieving constipation
Peristaltic action in the lower parts of the alimentary canal is stimulated by taking food into the stomach. This explains the laxative action of such foods as fruits, or, sometimes, milk, taken at frequent intervals. When all other methods fail, constipation can oftentimes be relieved by taking a glass of milk every thirty minutes until four glasses have been consumed.
Moisture and peristaltic action
The longer food remains in the intestines, the more completely is the water absorbed from the residue. The object to be obtained in relieving constipation is to increase the moisture and the peristaltic action. Whatever will accomplish these things will relieve and perhaps cure intestinal congestion.
The subject of intestinal congestion and purgative medicines will be discussed at length in Lessons IX and XI, Vol. II, p. 375 and p. 436, respectively.
[LESSON VI]
CHEMISTRY OF METABOLISM
Meaning of metabolism
Metabolism is a word used to describe all processes that take place within the body from the time food is absorbed from the digestive organs until it is passed out of the body through some of the excretory channels. To be more accurate, it means the sum of both the anabolic, or constructive, and the catabolic, or destructive, processes that continually go on in the animal body.
Distinction between anabolism and catabolism
The process of metabolism is chiefly one of tearing apart, or of breaking down, complex chemical substances into simpler forms of matter. Formerly, all processes in animal life were considered to be those of tearing down, or of simplifying, chemical compounds; while plant life was considered to be chiefly the process of building up complex substances from simpler forms of matter. This distinction, however, is rather general with many exceptions. The two terms, "anabolism" and "catabolism" are sometimes used to distinguish between the processes of building up complex chemical compounds, and the oxidizing or tearing down of such compounds by effort or activity. Thus, the formation of muscular tissue from the digested proteid materials would be a process of anabolism, or construction, while the conversion of glucose in the muscle-cells, into carbon dioxid and water would be an example of catabolism, or destruction.
Catabolism a process of oxidation
The process of catabolism is, in general, one of oxidation; that is, oxygen is added to the chemical compounds taken from the food we eat, forming simpler substances which are excreted from the body as waste-products. Oxidized carbon in the body forms carbon dioxid; hydrogen is oxidized into the form of water, while nitrogen leaves the body in the more complex and incompletely oxidized substance known as urea, the chemical formula of which is COH4N2. A small portion of nitrogen leaves the body in the form of uric acid, C5H4N4O3.
Why muscular work produces warmth
The process of anabolism usually absorbs energy or heat from the surrounding material, while catabolism produces heat as a result of oxidation, as do ordinary fuels. This explains why muscular work warms the body.
We may study metabolism best by considering the two purposes food serves in the animal body, as follows:
FIRST—THE BUILDING OF ACTUAL BODY-TISSUE
Every atom composing the human body is constructed from food. The number and the proportion of the various chemical elements composing the body are well known, and were it not for the fact that the body is constantly casting out old cells and waste-products, the problem of nutrition would resolve itself into the simple process of supplying the body with the materials needed for growth.
Formation of new tissue and destruction of old
We could analyze an adult man and a new-born infant, and know that the infant, in order to reach maturity, would need to add to its body so many pounds of oxygen, carbon, sulfur, iron, etc. The problem of nutrition, however, is more complex. Not only must we consider the formation of new tissue, but we must also allow for the rebuilding of the old, and for all those processes of vital activity that involve the consumption of food material and the destruction of body-tissue. Nor can this allowance be accurately proportioned from the analysis of the body, because the various elements composing it do not change with equal rapidity. Thus, a man in a harvest field might pass through his blood in one day ten or fifteen pounds of oxygen (in the form of water and carbon dioxid), which would amount to ten per cent of the oxygen contained in his body, but if he should take calcium or fluorin to the extent of ten per cent of that contained in the body, death from poisoning would speedily ensue.
We can better understand the use of foods and the process they undergo in building the body by considering separately each class of food material from the time it is absorbed from the alimentary tract until it is excreted from the bowels, or from the lungs and the kidneys, or deposited in the body as bone, fat, or tissue.
SECOND—THE GENERATION OF HEAT AND ENERGY
The second function, or rather group of functions to be considered in the study of metabolism is the generation of heat and energy. If the reader will recall what was said in Lesson II, regarding the production of heat by the process of oxidation, he can more clearly comprehend the method by which heat is produced in the animal body. However, as heat is only one form or expression of energy, these two subjects—heat and energy—should be considered together.
Heat and energy produced by oxidation
The production of heat and energy in the body occurs almost entirely through the oxidation of food. All three classes of foods, namely proteids, carbohydrates, and fats can be oxidized to produce heat.
Heat, a measure of energy
Energy may be mechanical, chemical, electrical, or thermal. The conservation of energy, which is one of the fundamental laws of science, teaches that no energy can be lost, but can only be changed into other forms. This being true, and because all energy can be changed into heat, we use heat as a measure of energy.
The "calory," a unit of heat
The unit of heat, and consequently of energy, that is used by scientists is the "calory," which is the amount of heat required to raise the temperature of one thousand grams of water one degree on the centigrade thermometer scale. The energy in food is measured in calories, as will be learned from the explanation given in the lesson entitled "Vieno System of Food Measurement."
Liberation of energy through metabolism
The Vieno is merely a unit especially convenient in measuring the energy in food. In order that this energy may be drawn upon or liberated in the body, it is necessary for the food to pass through the process of metabolism, as heretofore described.
THE MEASURE OF HUMAN ENERGY
Food may be considered as a store-house of latent or potential energy.
Intake and outgo of energy accurately determined
Because of the law, the conservation of energy, which shows that no energy in the universe can be lost, it is possible to study, with great accuracy, the energy produced in, and given off by, the human body.
The method by which energy is measured in accurate scientific experiments is by means of a device called the respiratory calorimeter.
How energy is measured
This device is a small room, the walls of which are impervious to the transmission of both heat and air. In this room a man or an animal may be kept for a period of several days. The air breathed, the food eaten, the body-heat given off, the waste-products excreted, and the mechanical work done, are all measured with the greatest scientific accuracy. Many interesting results have been obtained from the investigations conducted with this wonderful scientific device. These experiments will not be given in detail in this work, but it might be remarked that experiments within the respiratory calorimeter have proved absolutely that the law of "the conservation of energy" works in the human body in the same manner as in the scientist's laboratory. Moreover, such experiments have confirmed the results of the oxidation of various foods in the laboratory, and have given us data from which to compute the stored energy in various food substances. It has thus been Energy yielded from one gram each of proteids, carbohydrates and fats found that the amount of energy yielded to the body from one gram of proteid is 4.1 calories, and from one gram of carbohydrates 4.1 calories, while one gram of fat oxidized in the body yields 9.3 calories, which is more than twice that yielded by the proteids and the carbohydrates.
Since it has been proved that the laws established in the laboratory also apply to the human body, it is not necessary to conduct expensive experiments upon Simple method of finding number of calories in any food the human subject in order to ascertain the amount of energy in some new food. The food may be analyzed chemically, and the energy computed according to the above figures, or a sample of the food may be burned with an oxidizing agent in the laboratory, and the heat measured. This latter process consists simply of oxidizing a gram of the food in a closed steel cylinder which is immersed in a known amount of water at a known temperature. The increase in the temperature of the water, multiplied by the weight of the water in grams, gives the number of calories contained in the substance tested.
METABOLISM OF CARBOHYDRATES
Products formed in the body from digested carbohydrates
The products produced by the digestion of carbohydrates are absorbed from the alimentary canal in the form of glucose and smaller quantities of levulose, and acetic, butyric and lactic acids. This glucose passes into the blood-vessels of the intestines. These blood-vessels unite to form the portal vein which supplies blood to the liver.
Conversion of glucose into glycogen
The chief function of the liver is to regulate the sugar contained in the blood. The liver converts this glucose into glycogen and also acts as a reservoir in which carbohydrates are stored in the form of glycogen until needed by the body. From this glycogen, glucose, or blood-sugar, is again produced when the consumption from the circulation is greater than the supply. Moreover, the liver possesses the power to produce glucose when no carbohydrates are eaten, as glucose can be produced from proteids. The percentage of glucose in the blood remains, or should remain about level, averaging .15 of 1 per cent. It may seem odd at first that the quantity Percentage of glucose in blood of glucose in the blood remains so nearly level, when the quantity absorbed from the digestive organs, and that utilized in work, is so variable. The control of sugar in the blood is of very great importance in the body-metabolism or life-processes.
Uses of glucose in the body
The chief use of glucose, and of other forms of digested carbohydrates is in the formation of heat and energy. Glucose is oxidized chiefly in the muscles, producing carbon dioxid, water, and some lactic acid. Another function of glucose in the blood is to build up or form fat. Fat is a form of stored food which is not so readily available for use as are glycogen and glucose.
To use a homely figure of comparison, the energy-producing substances of the human body—glucose, glycogen, and fat—may be compared to the movement of merchandise in ordinary commerce. We could say that the glucose of the blood is as merchandise in the hands of the people, ready to be consumed. The glycogen of the liver would represent goods in the hands of the retailer, while the fat which is stored in larger quantities would be represented by merchandise in warehouses.
Fat produced from carbohydrates
Many interesting experiments have been conducted to prove that fat can be produced from carbohydrates. For instance, during a given period of time a pig was fed daily upon food containing half a pound of fat, and gained during the period nine pounds of fat. Such facts prove beyond all possibility of doubt that carbohydrates are converted into fat in the animal body.
METABOLISM OF FAT
Fat, when absorbed from the digestive tract, is in the form of fatty acids and glycerin, but immediately recombines into its original form after it has passed through the intestinal walls. This fat then enters the lacteals, which unite to form the thoracic duct. This duct or tube empties its contents into one of the large veins near the heart, whence it is distributed throughout the body. The fat of the blood is not regulated to a definite amount, like the sugar content. After a meal, very heavy in fat, the blood for a time is whitish in appearance, due to the numerous minute globules of fat taken into the circulation.
Body-fat may be absorbed directly from food
The fat of the body may be deposited directly from food-fat. This can be verified if an animal that has been starved until its own body has been greatly reduced, be fed upon some particular form of fat. The fat immediately deposited will then have the peculiar characteristics of the fat taken with the food. Thus a starved dog that has been given a heavy diet of tallow will deposit fat which will contain a large quantity of stearin and palmitin, and consequently have a higher melting point than normal dog fat. Ordinary animal fat, as has been shown in Lesson IV, is composed of various fats, each of which is a distinct chemical compound.
Human fat not identical with food-fat
The distinction between tallow, lard, olive-oil, and human fat, is chiefly due to the various portions of stearin, and olein, which composes the mixed fat. In normal cases, where fat is deposited at the usual rate, the body-fat is of uniform composition regardless of the food-fats. The reason human fat is not identical with food-fat is because the body has selective power in depositing these fats. Thus, if the sole source of fat which a man takes in his food is tallow, the fat-depositing cells in the human body would refuse a certain proportion of the stearin, depositing a larger percentage of olein, thus giving a softer or more liquid fat than that which was supplied in the food. The excess of stearin would be consumed in the production of heat and muscular energy.
Why exercise reduces obesity
When the consumption of glucose in the muscles becomes greater than the supply available in the blood, and from the glycogen of the liver, body-fat must be consumed. This explains why exercise reduces obesity.
The method of preventing, or of curing, obesity, is a double process:
1 The diet is selected and proportioned so as to reduce the amount of ingested fat
2 Exercises are prescribed to consume the fat that has accumulated
Fat, the chief source of energy
Of all food materials, fat is the least changed by digestion, and has no particular function in the life-processes except the storing of energy. More body-energy can be stored in a pound of body-fat than in any other form.
From these deductions it is evident that carbohydrates and fats perform very similar functions within the body, and can, in a large measure, replace each other as a source of heat and muscular energy.
METABOLISM OF PROTEIDS
Importance of proteid or nitrogenous foods
Owing to the fact that the tissues of the normal body are constructed chiefly from proteids, the metabolism of proteids or nitrogenous foods is of very great importance. When we realize the fact that muscle, blood, brain, nerves, cartilage, tendons, the various internal organs and the tougher material of the skeleton are only various forms of proteid material, and must contain their proportions of available or organic nitrogen, we can understand why nitrogenous foods form a distinct class that must be considered by themselves. Only the mineral deposits of the bones and the teeth, and the globules of fat that are deposited as a source of stored energy represent the nitrogen-free class of substances within the animal body.
THE USE OF PROTEIDS IN THE BODY
Proteids as tissue-builders
The first use Nature makes of proteids in the body is in the actual adding to or increasing of body-tissue. When an emaciated young man from the city goes to work on a farm and gains twenty pounds, the cells of his muscles have actually increased in size and number. This requires proteids, which can be obtained only from the nitrogenous material in food. The growth during early life is due to an actual increase in the size of all the organs of the body, and is merely an accumulation of proteid substance.
Proteids form the nitrogenous part of the body
The second use of proteids, and the one which, in matured life, is of more importance than those already referred to, is in the formation of the various nitrogenous products which are produced in connection with the different processes of the body and which are destroyed by the function of life. For example, the pepsin of the gastric juice is a nitrogenous substance which can be formed only from proteids. All digestive enzyms and other substances in the muscles, nerves, and in the various organs throughout the body are of a nitrogenous nature, and in their formation and use a certain amount of proteid material is consumed. When the digestive enzyms are formed from proteids, they consume more than their own weight of proteid material.
Proteids replace worn-out cells
The third form in which proteids may be consumed in the body is in the actual replacement of worn-out cells. The skin, the hair, and the mucous or lining membranes of the body-cavities are constantly being cast off on the external surface, new cells being formed underneath. When cells within the interior of the body have become injured, or have passed their usefulness, they are removed by the phagocytes or white blood-corpuscles, and must be replaced by other cells. In the case of bacterial infections, as tumors, boils, or contagious dis-eases, the bacteria feed upon the proteids of the blood. The white blood corpuscles are destroyed in the conflict, or effort to remove the intruders, and all these substances must be replaced by proteids from food.
THE ACTION AND THE COMPOSITION OF PROTEIDS
Determination of income and outgo of nitrogen
The gain or loss of body-proteids is indicated by the gain or loss of nitrogen. The income of nitrogen can be ascertained by analyzing the food. The outgo of nitrogen is computed by analyzing the products excreted from the body. If the body at the beginning and at the end of an experimental period is carefully watched, and the income and the outgo of nitrogen determined, we can compute the amount of gain in the body that is nitrogenous tissue. The other gain or loss of body-weight must be fat. These calculations cannot be made exact, owing to the amount of food and water that may be in the digestive organs at the time the various weighings are made.
Why proteids are converted into peptones
We have learned that in the digestive tract foods are converted into a soluble form of proteid known as peptone. The purpose of this conversion and the fine subdivisions of food produced by the various digestive juices are to reduce it to a form which will readily pass through the walls of the alimentary canal.
Nitrogen and urea
This is all that was known about proteid metabolism until within very recent years. The older scientists followed proteid digestion until the soluble peptone stage was reached, at which point all track was lost of the chemical changes and processes until the nitrogen was again excreted by the kidneys in the form of urea.
No scientist attempted to explain how the radically different proteids, such as egg-albumin, milk-casein, and wheat-glutin could appear in the body as blood-globulin, brain-lecithin, or as a myosis of the muscles.
The history of all these investigations cannot be fully explained here, but the discussion must be confined to that which actually takes place in the metabolism of proteids.
Composition of proteids
Proteids, as the student will remember, contain carbon, hydrogen, oxygen, and nitrogen, and sometimes small quantities of sulfur, phosphorus, or iron. These forms of proteids are now known to be chemically changed, by the digestive enzyms of the intestines, into simpler compounds containing these same elements.
How proteids may form body-fats
These simple nitrogenous substances pass into the liver. Just as the liver regulates the supply of blood sugar, so it regulates the supply of nitrogenous compounds in the blood. A certain amount of proteid-forming material is passed through the liver, and goes on to perform the various functions for which proteid is utilized in the body. All nitrogenous material in excess of the amount required by the body is secreted by the liver, and the nitrogen, together with a portion of the carbon, hydrogen, and oxygen, is split off, forming urea, which is excreted by the kidneys. The remainder of the proteid substance, having been robbed of its nitrogen, is now essentially the same as carbohydrates, and goes to form glucose or blood-sugar, which may in turn form body-fats.
Excess of proteids harmful
In the light of this explanation, we can understand several things already mentioned. It has been stated that proteid is the most essential food material of the body because it alone contains the nitrogenous compounds from which the body-tissues, and the chemical enzyms which control all living processes, can be constructed. But we now see that as important as is a supply of proteid materials, any excess above the body-needs is immediately turned into glucose and urea. The glucose, though useful to the body, could be taken in a simpler and less expensive form, while the urea is a waste-product, harmful to life, and must be immediately excreted by the kidneys.
The nitrogen that is actually used in the body serves a different purpose from that which is split off from the excessive proteid taken as food. The food proteid is simply split by the chemical addition of water, much the same as starch and other carbohydrates are changed into glucose. The proteid that is really used by the body is oxidized, and is excreted by the kidneys chiefly in the form of creatinin and uric acid.
FOOD STANDARDS
Incorrect interpretation of scientific data
The term "dietary standard," as it has been applied in the past, means the quantity of the several nutrients that should be taken by the human body under its varying conditions. During the past twenty-five years, many investigations have been made in this country, Europe, and Japan, regarding the amount of foods consumed by various groups of people. All the facts gathered, which include more or less accurate records of the foods eaten by many thousands of individuals under all circumstances and conditions of life, are invaluable scientific data, but the interpretation that has been placed upon these interesting observations is one of the most conspicuous blunders made by the scientific world. Whether this criticism should fall wholly upon the men of science, who made these investigations, or upon the people who misinterpreted their meaning, is perhaps an open question; but the fact remains that from the general teachings in physiologies, and from popular bulletins published by the National Government, very incorrect ideas have been widely spread respecting the amount of food required to maintain life and health.
Data of foods consumed daily by various people
In order to give the reader some idea of the results obtained, when data is kept each twenty-four hours, of the amount of food consumed by various people on the conventional diets of civilization, I will select at random some of the results that have been recorded in these investigations, and will give in the Vieno System the approximate results. (See "Vieno System of Food Measurement," Vol. III, p. 639):
| Decigrams | ||
| Nitrogen | ||
| Vienos | Consumed | |
| California Football Team | 66 | 375 |
| New England Rowing Club | 40 | 255 |
| Wealthy Class in American Cities | 30 | 250 |
| U. S. Army Rations. | 37 | 200 |
| Farmers, Eastern U. S. | 34 | 160 |
| Skilled laborers, U. S. Cities. | 40 | 220 |
| Alabama Negroes | 34 | 145 |
| Japanese Peasants | 20 | 100 |
Atwater's Government Standards
From such records Government standards have been roughly approximated. The standards published by the Government, computed by Prof. Atwater, and commonly known as the Atwater standards, are as follows, expressed in vienos:
| Decigrams | ||
| Nitrogen | ||
| Vienos | Consumed | |
| Man at hard muscular work | 55 | 280 |
| Man at hard work | 41½ | 240 |
| Man at moderate work | 34 | 200 |
| Man at light muscular work | 30½ | 180 |
| Man of sedentary habits | 27 | 160 |
The Atwater standard for women is estimated to be four-fifths of the amount of food required for a man under similar conditions.
It is generally recognized by investigators that these so-called standards are faulty, but by mutual agreement it seems that they have been accepted as the best that could be given. Faulty standards due to inexperience They lack accuracy because the men who prepared them lacked experience. Accuracy can come only from experience gained in the practical work; that is, in prescribing food, and combinations of food, for people under all the varying conditions of age, climate, and activity, and having these people report, at stated periods, the results of their dietetic prescriptions.
Importance of correct dietary standards
The average person eats what is set before him and asks no question about nitrogen and energy; nevertheless, advice so universally distributed as the Government Dietary Standards must exert much influence and have a considerable effect upon the habits of the people. Obviously the correctness of these standards is of vital importance to the health and the welfare of the nation.
What a dietary standard should contain
A dietary standard should tell the quantity and the proportion of food required to keep the human body in its very best working state. The great error committed by the man who planned the above-named standards has been that he assumed that an average of what a man does eat is a criterion of what he should eat in order to maintain the best mental and physical condition. A greater error could not have been made. Our feeding instincts have been lost in the chaos of civilization. Both our appetite and our food have been perverted. We have been trained to want or to crave intoxicants, stimulants and sedatives; we have learned to relish things that have no food value, and we have grown to dislike the best food that nature produces, and to accept many of her worst. Dietary standards, therefore, made up from the conventional eating habits of the people, merely endorse their errors and pass them on to future generations. The work, therefore, of the true scientist is to point out these errors and to prescribe a remedy.
We are creatures of many (bad) habits
Man is a creature of habits, and civilized man is a creature of a great many bad habits. The argument that the average amount of food eaten is the amount that should be eaten falls under suspicion at once when we consider the fact that by a similar line of reasoning we could prove that the use of tobacco is necessary because the majority of men use it, or that slender waists are necessary to good social standing because a few million women so consider them.
American prosperity not due to rich diet
The idea has been spread far and wide that the diet of the American working man, which is the richest in proteid of any race in the world, is responsible for the greater economic thrift of the American people. It is a matter of history that rich diet is always associated with prosperity, but the theory that the diet is the cause of the prosperity is an egregious error. Meat and rich foods gain a hold upon the appetite as do alcohol and narcotics. When nations or cities become wealthy, intemperance in eating is the usual result, but this in nowise indicates that a heavy consumption of food is the cause of a nation's greatness. History recites many instances of the rise and growth of a people to power and prosperity, together with the consequent adoption of excessive and luxurious habits of eating and drinking, only to be followed by physical deterioration.
Excessive food a waste of energy
It is not the quantity of food that is eaten, but the quantity of food that will give the greatest vitality and capacity to do things, that should determine our dietary standards. It is reasonable to assume that this amount would be the least quantity that would maintain activity without using up the food material stored in the body. All food taken in excess of the amount actually required must be cast from the body at a tremendous expense of energy. To do a given amount of work, or to add one pound of muscular tissue to the body, requires a definite quantity of energy-yielding or tissue-building material, but if more food is taken than the body can use, the excess ferments in the stomach and in the alimentary tract, producing poisonous products which are absorbed into the blood. These poisonous products cause a great number of human ills. The process of eliminating these poisons we call "dis-ease."
Former dietary standards cut in half
The assumption that the correct amount of food that should be taken by the body is the least quantity that will maintain normal body-functions, has been amply proved by recent scientific investigations to be correct. Many years of experience on the part of the writer have shown that to make food remedial and curative, the old dietary standards must be, roughly speaking, cut in half.
TRUE FOOD REQUIREMENTS
Quantity of food required for various occupations
The degree of energy required by the body depends very largely upon the amount of work or activity it undergoes, hence the amount of food required to supply this activity cannot be accurately prescribed when the degree of required energy is unknown. However, there is a certain amount of work performed by the beating of the heart and in the maintenance of body-heat which can be fairly well estimated. The quantity of energy-yielding food required, each twenty-four hours, for the maintenance of the activities of life is about one vieno for every ten pounds of body-weight. For a man at steady muscular work, such as a carpenter or a farmer, this quantity should be about doubled. The quantity required by a man of sedentary habits, but who takes regular exercise for an hour or two each day, is about half way between these two amounts. Thus, a man weighing one hundred forty pounds would require one and one-half vienos for each ten pounds, or twenty-one vienos of food each day. These weights apply only to people of normal flesh, who desire neither to gain nor to lose.
The fact that either fat or carbohydrates can be used as a source of muscular energy may be taken advantage of in prescribing dietaries for persons whose digestive organs are so impaired that they cannot digest a normal quantity of either of these nutrients, but who could digest a small quantity of either. This does not mean, however, that the proportion of fat and of carbohydrates in the food can be disregarded. The digestive processes involved are radically different, hence a suitable proportion of carbohydrates and fats should always be maintained.
Proportion of fat required under ordinary conditions
With a view to guiding in a general way those who wish to adopt a standard of diet for ordinary use, and who consult tables in which fats and carbohydrates are listed separately, I might state that the fat should form about one-eighth the total source of energy, or one-sixteenth the weight of all water-free (solid) food eaten.
Fallacy of lean meat producing muscle
Until forty years ago the idea was held by scientists, and is still a matter of popular belief, that nitrogenous foods are the sole source of all muscular energy. This is quite a natural assumption. Lean meat is muscle. If a man eats the muscle of another animal, by the primitive process of reasoning, he should acquire muscle. This belief among people who are not acquainted with physiological chemistry is almost universal, while the facts are, the man who eats the muscle of an ox for the purpose of adding strength to his own biceps is acting no more wisely than the college boy who takes calf's brain for breakfast the day before examination.
Nitrogenous foods not a source of muscular energy
The fact that nitrogenous foods are not a source of muscular energy has been repeatedly proved by experiments on man and animals too numerous to relate here. The sugar and the fat in the blood are taken into the muscle-cells, and there unite with the oxygen brought from the lungs, producing energy. When the body is fed upon proteids lacking a sufficient quantity of other food elements, a portion of this proteid is converted into glucose or sugar, which maintains body-heat and energy. This is what happens in the case of carnivorous animals that have excretory organs especially adapted to the converting and the eliminating of useless or surplus products.
Small amount of proteid matter required by animals
It has been proved that dogs are capable of living for an indefinite period of time upon a diet containing only a small proportion of proteid matter, while maintaining health and increasing in weight. Thus we see that even carnivorous animals require, for the maintenance of the body-functions, a comparatively small amount of nitrogenous material. Their strength and heat-forming elements can be secured from carbohydrates and fats, probably to their actual benefit. It is interesting to note, however, that dogs as a general rule cannot live and thrive on a vegetable diet; a certain amount of animal proteids seems indispensable. The same principle applies to other carnivorous animals. Even ducks and chickens need a small percentage of animal proteids in order to properly thrive and develop.
Conditions governing quantity of nitrogen
In order to maintain good health, every person requires a certain amount of nitrogen, the quantity being governed by activity, exposure, age, and temperature of environment. The growing youth needs nitrogen to supply material for the tissue growth of his body; an emaciated person who wishes to increase weight, a person recovering from illness, or a man who is constantly performing strenuous work, would all require a generous quantity of nitrogenous food.
Lowest daily amount of nitrogen required
The lowest possible nitrogen requirement for one of normal weight has been determined by various methods to be from 40 to 60 decigrams per day. This quantity, however, is the actual amount that is used in the body-processes, and should be increased according to activity or exposure to the open air.
From the results of numerous experiments under normal activity, the quantity of nitrogenous food estimated to maintain the best bodily condition is about three-fourths of a decigram for each pound of body-weight; less than Amount of nitrogen required by the body one-half of a decigram per pound of body-weight would cause nitrogen starvation, while more than one decigram per pound, except in the cases just mentioned, would result only in thrusting needless work upon the liver and the kidneys, whose duties are to guard the body against the results of incorrect eating. There are certain conditions under which this amount of nitrogen may be exceeded in order to gain definite and specific purposes, but in such cases the nature of the proteid is of great importance. In certain occupations, for instance sedative labor, the most soluble proteids, such as egg albumin (white of eggs), milk, and green peas and beans should be selected; while in cases of heavy manual labor, the heavier proteids, such as nuts, cheese, dried legumes, fish and fowl should be selected.
[LESSON VII]
FOODS OF ANIMAL ORIGIN
An intelligent discussion of this lesson leads us directly into a subject commonly known as "vegetarianism." The question whether man should eat the flesh of animals is especially fascinating for those who give attention to the food they eat. There are many standpoints, however, from which the subject of vegetarianism may be discussed.
Influence of religion on man's food
In the first place, nearly all religious teachings that have wielded such a powerful influence over the civilization and destiny of men, have laid some restrictions upon the flesh-eating habit. Some religions require man to refrain from all animal products, while others interdict only the flesh of certain animals. Coupled with man's world-wide search for food, these religious teachings have played a conspicuous part in the question of human nutrition.
Vegetarianism from animal's standpoint
The second phase of the question that merits attention is the moral side, or vegetarianism from the animal's standpoint; in other words, the cruelty involved in the slaughter of our dumb friends and helpers, for whose presence here we are largely responsible. That the practises and customs which train humanity in cruelty toward animal life, are to be discouraged, cannot well be disputed, but this phase of vegetarianism is one which is somewhat without the realm of applied food chemistry, hence is mentioned only as a factor in the general discussion.
I will now consider vegetarianism from the standpoint of true food science, or the welfare of the physical man. It will be observed that in the lesson entitled "Evolution of Man," one of the first considerations taken up is the scientific Vegetarianism from standpoint of scientific living discussion of man's natural adaptation to the use of flesh foods. By natural adaptation I mean Nature's evolutionary plan of fitting the physiological organism to the food man is able to procure. The organism of man will, to a certain extent, adapt itself to a given diet within the brief period of one generation, just as, in the long ages of evolution, the digestive organs of any species of animal become adapted to such diet as may be procured. Thus it is of especial importance for us to know the diet of primitive man at a time before his intellectual resourcefulness made it possible for him to gather his bill of fare from the four corners of the earth.
The diet of our related anthropoid apes, of every primitive savage tribe, and of our ancestors, indications of which have been found in fossils and caves—all three throw light upon the subject. The consensus of these various studies indicates Primitive diet of man that the original or natural diet of man was one drawn chiefly from the vegetable kingdom, but not entirely so. Fruits, nuts, green vegetables, edible foliage, tubers or roots were all included in man's primitive diet. The foods of animal origin were varied, and consisted of such articles as birds, eggs, shell-fish, many insects, and other forms of lower animal life, of which our modern habit of eating frogs' legs, eels, escargots (snails), etc., is merely an inheritance.
Why flesh-eating is unnecessary
Since the digestive, the assimilative, and the excretory organs of man have been constructed from, and adapted to, the use of vegetables, it is obvious that the flesh of animals is unnecessary, especially in view of the fact that there is nothing in flesh that cannot be secured from the vegetable world in its best and purest form. Man's primitive diet does not prove that he is by nature a vegetarian, as is the cow, and therefore entirely unsuited to digest any material of animal origin. The anatomy of man's teeth and of his digestive organs, however, indicates that he is by nature a vegetarian, and that his digestive organs are prepared to dissolve and to assimilate a diet that is somewhat more bulky than that of carnivorous animals, but, on the other hand, less bulky than the diet of animals which subsist wholly upon succulent plants, as do the purely herbivorous species.
Food problem of the Aryan races
Man is by nature a tropical animal, and so long as his habitat was confined to that section, he could live from the prodigality of Nature, but when he began his early migration northward, his food was the greatest problem he had to solve. He was often forced to choose between eating the flesh of animals and death from starvation. It was this fierce struggle for food, not the character of his food, which exercised both the physical and the mental powers, and caused the Aryan or northern races to think, and therefore to develop into people so much superior to their tropical brothers.
Forced to think and to work, man became civilized
The defenders of flesh food often point to the fact that flesh-eating people have achieved the highest civilization. Man's superior achievement in northern countries can no more be credited to flesh-eating than to the wearing of fur caps or leather boots. To meet the exigencies of his environment, he was forced to think and to work, and thinking and working developed the brain and laid the foundation for his present stage of civilization.
Another reason for the early habit of flesh-eating is found in the fact that in order to sustain the required amount of body-heat in cold climates, a liberal consumption of fat was necessary. Vegetable fats not being available, his only source of supply was from the body-fat of animals.
Use of meat unscientific
Aside from fat, protein is the only nutritive element meat contains. With the variety of vegetable and butter-fats, and vegetable proteids available in this age, supplemented by our knowledge of chemistry as a guide in their use, the consumption of flesh as an article of human food is entirely unscientific and wholly without reason.
Life MAY BE maintained by meat
A diet composed exclusively of flesh contains fat and nitrogenous compounds only. These two classes of foods can, of course, maintain life, as was explained in our sixth lesson, as proteid is capable of forming blood, sugar, and body-fat. The fact, however, that the proteid or the fat of meat can be made to fill, in the physiological economy, the place naturally supplied by the carbohydrate materials of vegetable food, does not prove that such a diet is without its harmful effects. The living body has many wonderful provisions whereby life is maintained under unfavorable influences. Just as a blind person develops a sense of touch which in a way acts as a substitute for sight, so the ability of the body to convert either proteids or fats into sugar, may be utilized in cases of emergency, but the using of this emergency or substitute function of the body cannot develop and energize the human machine as well or as perfectly as can a naturally balanced diet. The fact that some people exist largely upon a meat diet does not prove that this is without its handicapping and evil influences, any more than the use of alcohol and tobacco proves that man is benefited by indulging in intoxicants and sedative poisons.
That flesh-eating is largely responsible for the universal desire among civilized people for some form of stimulant has ceased to be questioned by those who have been placed in a position to make experiments—the source from Flesh-eating produces appetite for stimulants which all real knowledge is obtained. These conclusions were first forced upon the writer by noticing the gradual decline of appetite for coffee and tobacco in his own case, when he began to subsist upon natural foods. With this hint no opportunity was lost, among the thousands of patients he treated, to observe the effects and get at the truth. If only one or two people had completely lost their appetite for all forms of stimulation, after following a natural food regimen, it might have revealed only an idiosyncrasy. When a dozen undergo the same treatment, with the same results, it leaves but little doubt that the theory may be true, but when many hundreds give the same testimony, through a period of a dozen years' practise, it reveals a truth that cannot be consistently doubted. Such experience proves beyond doubt that flesh-eating supports and perpetuates the habit of taking distilled and ardent liquors, tobacco, tea, and coffee, and the numerous drugs which, altogether, have done the human race more harm; dethroned more intelligence; sapped from the human economy more vitality; ruined more homes; made more widows and orphans; changed more natural virtue into vice, and caused more sorrow and tears, more failure and fears, than all other agencies of destruction combined.
Since fats and proteids are the only nutrients supplied by flesh foods, we may well ask, "Is meat the best source from which these elements may be secured?"
Flesh food contains unexcreted waste matter
The proteid substance of meat includes all the edible portion of a carcass except the fat. The proteid of meat is more easily and more rapidly digested than the proteid of vegetables. Notwithstanding this fact, there are serious objections to the use of meat as a source of nitrogen. All flesh food contains the unexcreted waste matter of the slaughtered animal. When the process of metabolism that is continually going on during life is suddenly arrested by death, the effete and decomposing cells, and the partly oxidized waste-products which are still held in the muscle-tissues, are left in the flesh of the dead animal, hence these poisons must be consumed by the flesh-eater in order to secure the meat proteids and fats.
Body-poisons generated by fear
It is now a matter of common knowledge among scientists, and among the more advanced school of pathologists, that the usual conditions under which animals are slain change the chemical constituents of the blood-serum, charging it with a form of poison that to the chemist is as yet unknown, but the presence and the potency of which is attested by its effect.
The method of slaughtering animals in the great abattoirs is especially conducive to the generation of these poisons. The condemned herd is driven to the place of slaughter and killed, one at a time, in plain view of their fellows. These animals are very intelligent and possess remarkable senses of danger. They are as conscious of approaching death as the creature who takes their lives, hence the amount of poisons generated in their bodies is measured by the time they are kept in waiting. Most animals when killed labor under these conditions, and that these mental states render their flesh entirely unfit for human nutrition can no longer be questioned.
Mother's milk poisoned by fear or anger
We find fragments of evidence supporting this theory in the fact that Nature's perfect food—the milk of a nursing animal, or of a nursing mother—can be changed in an instant into a poison by sudden fright, anger, or fear.
Meat a source of autointoxication
Thus we see that in eating meat, we are eating animal waste-material similar to that thrown off through our own body-cells. The waste material in meat being soluble, passes through the walls of our digestive organs, and enters the circulation, where it is added to similar poisons which are constantly being produced within our own bodies. It is the universal law of animal cell-growth that the waste matter of the cell acts as its own poison. When bacteria, growing in a solution of sugar, have excreted alcohol until it forms a certain percentage of the total contents, their activity ceases—they die from poisons thrown off from their own bodies. This is the reason that liquids containing a high percentage of alcohol must be distilled, and cannot be brewed. It is obvious, therefore, that in the consumption of flesh, we are adding to our bodies the poisons that are residual in the body of other animals, and are, therefore, approaching the conditions under which bacteria kill themselves by autointoxication or self-poisoning.
Plants utilize the carbon dioxid excreted by the animal, and the excrement of animals is in turn used to fertilize our fields. Although one form of life may utilize what is excreted by another form of life, the living thing that cannot get away from the excreted matter of its own activity is poisoned thereby.
Flesh food burdens the excretory organs
The flesh of animals whose physiological processes are almost identical with our own, containing as it does waste-products that have not yet been excreted, must, when taken into the human body, add extra burdens to our excretory organs which are usually burdened with all they can do. Carnivorous animals are especially provided with an excretory system capable of taking care of such matter, but it is unreasonable to expect the excretory organs of man, which are not adapted to such a purpose, to throw off, in addition to the regular body-poisons, similar decomposing products of other animals.
Flesh-eating will disappear as science advances
It is true that flesh will support, and has supported what is commonly regarded as a high form of anthropoid life (man), but not having the natural standard from which to measure, we do not know how much better the opposite course would have been, or just how much longer one would live under a perfectly natural regimen. The effects of flesh-eating have not been definitely known until recent years, but is now acknowledged by the most advanced authorities to be one of the greatest errors of civilized people, and will, within a few years, disappear from the catalog of human habits, when the great masses of people are made familiar with the chemistry of food, and how to secure vegetable instead of animal proteids and fats.
MEAT
Meat, in the sense the word is here used, includes beef, mutton, pork, and an occasional allowance of wild game. Chemically considered, meat may be divided into two classes, namely (1) flesh or lean meat, and (2) animal fats. The former will be first considered.
1 FLESH OR LEAN MEAT
Composition of lean meat
Lean meat is composed of the muscles of the animal. Approximately it is 70 per cent water, 20 per cent protein, and 10 per cent fat. The protein is composed of connective tissue, which is a tough, fibrous substance that forms tendons, and holds the muscle-cells in place. Chemically, connective tissue is formed of albuminoids, which were discussed in Lesson IV. These substances are somewhat difficult to digest, and are not of very great importance in the human body, as they cannot take the place of true proteid in tissue-formation.
The percentage of connective tissue in flesh depends upon the cut of the meat. As every housewife knows, the cheapest cuts of meat contain a larger amount of this material.
The gelatin of commerce is a manufactured product derived from the connective tissue of animals.
Other forms of protein are globulin and myosin, which form the actual muscle-substance. These elements form perhaps three-fourths of the entire proteid of the animal, and are the most valuable substances of flesh food. A very small portion of meat proteids is formed by the free albumins of the blood, which are mechanically retained in the muscle-cells, the purpose of which is the nourishment of the animal, and therefore are not unwholesome as food.
Meat extractives and their composition
Another class of nitrogenous substances found in flesh foods is called meat extractives. Though they exist only in quantities of from one to two per cent of the weight of the flesh, they are the most interesting from the standpoint of chemistry, because they are found only in flesh foods, and are products only of cell life, hence not wholesome as food. They are composed of urea, uric acid, creatin, etc., and are similar or identical to the waste-products of human cell metabolism. The amount of these substances contained in flesh depends upon the condition of the animal at the time of slaughter, being much greater in animals slain after the chase, or laboring under fear or abuse.
The chemical composition of the different cuts of meat does not vary greatly, except in a greater or less per cent of fat, and no chemical calculation can compute this accurately, as the fat in every cut of meat varies widely.
Prejudice against the hog
Beef and mutton are comparatively the same in both nutritive value and popularity, but the use of pork has been generally condemned the world over. The reason for this is probably explained by prejudices of tradition and religion, rather than by scientific or hygienic knowledge. The prejudice against swine because of the filthy habits of the animal is more a matter of sentiment than of science. It is sometimes the custom among farmers to confine hogs in a pen, and to feed them upon swill and garbage. This makes of the animal a filthy creature. However, when left in the open fields or woods, they are as cleanly in their habits as any of their brother animals. Corn and alfalfa-fed pork is equally as wholesome as beef or mutton, when prepared in a similar manner, and eaten in temperate quantities, while the hog fattened upon acorns and herbs, in his native habitat (the woods), is much more healthy, and his flesh really superior to most of his brother animals.
2 ANIMAL FATS
Animal fats not a necessity
The use of animal fats as food is a very ancient custom, especially among the northern tribes. This custom was once justified owing to the necessity for the consumption of a liberal amount of fats in cold countries, but in this country where our marvelous system of international transportation places at the door of every northern home the delicious fats from the olive orchards of Italy, France, and Spain, the refined oil from the cottonseed, and more than a dozen varieties of nuts, including the humble peanut, there is but little necessity for the use of animal fats except in the form of butter and cream.
Chemical change in frying fats
Perhaps the most injurious way in which animal fats are used is in the process of frying, which is much practised in southern countries in the preparation of other food. The chemical change which takes place in fats, when treated in this manner, renders them exceedingly indigestible, and almost wholly unfit for food.
That per cent of animal fats contained in the ordinary meat diet is quite as wholesome as any other element of nutrition secured from animal sources. However, with the splendid supply of vegetable fats civilized people have to draw upon, the use of animal fats cannot be recommended in any form except that of cream and butter, and when we consider the expense of these by comparison with many pure vegetable fats, our sense of ordinary economy would bid us discard them.
Chemical difference between animal and vegetable fats
The chief distinction between animal and vegetable fats is in the proportion of olein compared with stearin and palmitin. The proportion of the two latter fats is much greater in fats of domestic animals than it is in the human body; this is especially so of tallow. For this reason vegetable fats, which are of a more liquid nature, are more desirable than those of animal origin, especially where we wish to add fatty tissue to the body.
COLD STORAGE OF MEAT
A very small amount of the meat produced in this country at the present time is consumed near its place of slaughter. Cold storage plants and refrigerator cars have been constructed for the purpose of preserving meats until they can reach their destination, and to hold them awaiting market advances for the benefit of packers and tradesmen.
Decomposition of cold storage meat
Meat in cold storage is slowly undergoing a form of decomposition which is evidenced by the fact that cold storage meat decays much more rapidly upon its removal from storage than do the same cuts of fresh meat.
The process of ripening meat in rooms of varying temperatures depends upon this form of decomposition. The natural enzyms of the meat, and the bacteria contained therein, digest a portion of the proteids, forming nitrogenous decomposition products, similar to the above-mentioned meat extractives. Ripened or storage meats contain a much larger per cent of this group of compounds than does fresh meat.
"Ripened meat" a step toward decay
The high flavor and "peculiar rich taste" of ripened meats is produced by these decomposition products, while the decay of the gelatinoid or connective tissue is the primary reason for its tenderness. There are certain species of bacteria that produce more poisonous waste-products than others, and this occasionally causes the development of ptomains in storage meat.
A choice between two evils
The use of flesh as an article of food is fraught with many serious and scientific objections, but the use of cold storage or ripened animal products is to be condemned from every standpoint of hygiene. Nevertheless, if people insist upon using flesh foods, and economical conditions make it profitable to produce them far from their place of consumption, cold storage methods seem inevitable. The choice between storage meats and home-killed is, in its last analysis, a matter of selecting the lesser of two evils.
CONTAGIOUS DIS-EASES AND ANIMAL FOOD
Rare beef unfit for food
Much has been written as to how, from dis-eased animals, human beings have contracted contagious dis-eases, especially tuberculosis. The risk of such contagion has in all probability been much exaggerated. Flesh foods are seldom taken in an uncooked form, and dis-ease germs are usually destroyed by the sterilizing process involved in cooking. The cooking process, however, must be very thorough in order to destroy dis-ease germs; that is, the heat must be sufficient to coagulate the proteids. The interior of a rare beefsteak, such as popularly demanded by the flesh-eater, has not reached this temperature, hence this form of meat should be condemned on this ground if for no other.
Trichinosis
Perhaps the worst form of dis-ease contamination from fresh flesh food is that of trichinosis. Trichinae are worm-like creatures which have the first stage of their growth in the flesh of swine, and then become encased in a cyst or egg-like structure, which, when taken into the human digestive organs are revived, and the trichinae then bore their way through the walls of the digestive organs, completing their growth in the human muscle-tissue. Trichinosis is one of the most fatal of diseases, but fortunately is not common. Tapeworms owe their origin to a similar source. There are several species of tapeworms; some have their origin in pork, and some in beef.
FISH
Under this heading I will consider fish and other sea-creatures.
Nutrients in fish
The flesh of most fish is quite free from fat, and consists almost entirely of water and proteids. It is less concentrated than the flesh of warm-blooded animals, averaging about 18 to 20 per cent proteids, and 60 to 70 per cent water. The percentage of ash in fish is also somewhat greater than in any other flesh food. The popular idea that fish is good food for the brain originated in the fact that analysis of some fish shows a considerable percentage of phosphorus, which substance Fish as brain food is also found in the brain. There is no reason to believe, however, that the liberal use of fish would develop or produce an excess of brain-tissue. Any well-balanced diet contains ample phosphorus to nourish the brain.
The true science of human nutrition lies in the knowledge of selecting, combining, and proportioning food according to age, climate, and work. When this is done, the tendency of the body is to eliminate dis-ease and to assume normal action; this accomplished, every part of the anatomy shares in the general improvement.
Fish superior to flesh of mammals
My theory advanced against the use of meat because of nitrogenous decomposition products, holds true with fish, though in a somewhat limited degree. The decomposition products of cold-blooded animals are not identical with those of mammals, hence their consumption as food does not add to the percentage of human waste-products so directly as do other meats.
Oysters and clams unfit for food
Oysters and clams, which are generally eaten uncooked, are recommended by many authorities as valuable sources of proteid. The serious objection to their use, and especially uncooked, is the fact that they are grown in the sea-water around harbor entrances which are flooded with sewage, and hence they are likely to be contaminated with typhoid, or similar germs. The actual food value in shell-fish is quite small. They contain only about ten per cent of proteids, and are scarcely worth considering as a source of nutrition.
POULTRY AS AN ARTICLE OF FOOD
The objections that I have made against the use of the flesh of fish and mammals as an article of food may also be assessed against the use of domestic and wild fowls. There are a few special points, however, in favor of poultry as food that are worth special consideration.
The production of chickens and other domestic poultry is one of the most prolific industries in America, and is of great importance to the general public because it is capable of being carried on in communities too thickly settled for the economic production of beef and other meats.
Poultry superior to the flesh of mammals
Another point to be observed in the use of poultry as food is that, because of the ease with which every farmer and villager can keep a flock of chickens, it is possible for him to have fresh meat produced under the most sanitary and hygienic conditions, while if he uses meat as food, he will be compelled to depend upon the various meat products of unknown age and origin, secured from the general market.
Another reason why the use of poultry, from a hygienic standpoint, is less objectionable than the use of pork and beef is that the quantity consumed is usually much smaller than the amount eaten of these heavy-blooded meats.
For example: When five pounds of beefsteak is purchased in the market, the amount consumed would be almost the full weight of the purchase. If the money were invested in a five-pound chicken, a goodly portion of this weight would be lost in preparing the fowl for the table, while a still further loss would occur in the bones and in the inedible portions, so that the actual amount of flesh consumed would not be more than perhaps two pounds.
According to the old idea of economy and diet, this would be a serious argument against the use of poultry products, but as has been clearly proved in this course of lessons, the most serious criticism that can be urged against the modern bill of fare is quantity, and especially the use of meat in large quantities, so common among the American people.
Custom vs. hygiene
The chief reason for which meat is kept upon the bill of fare of most civilized people is that of conformity to custom, surely not to that of hygiene. That form of meat, therefore, which is pleasing to the taste, and which has a tendency to reduce the quantity of flesh consumed, is a step in the right direction of true food reform.
EFFECTS OF FEEDING POULTRY
Fattening poultry
The methods of fattening poultry by shutting them in small coops or compartments, and feeding them upon soft mushy foods, is condemned by some writers on the ground that it is unnatural and harmful to the health of the fowls, and therefore the meat cannot be wholesome. In truth, this process, if not carried too far, will produce a quality of meat less harmful than that of the barnyard and ill-fed poultry. One of the greatest objections to the use of animal food, as already explained, is the presence of the unexcreted waste-products of animal metabolism. The flesh of fowls, fed and fattened in coops, contains the smallest possible quantity of waste or decomposition products, because of the limited amount of motion or exercise they are permitted to undergo. For this reason, when poultry is to be eaten, the whiter the meat the less objectionable it is as an article of food.
Marketing poultry undrawn
The marketing of poultry in an undrawn condition (without the removal of the internal organs), has been much condemned by the public, and the legislatures of some states have passed laws against this practise. This, however, is to some extent a misapplication of good intentions. When poultry is to be killed for the market by those who thoroughly understand the business, the fowls are left without food for a period of twenty-four hours. Since the digestive processes of these small animals are very rapid, this results in emptying the intestines of most of the fecal matter, which removes the principal objection to the practise. On the other hand, if the fowls are drawn at the time of killing, and several days elapse before their consumption, bacteria gain access to the interior of the carcass and cause very rapid decomposition.
"Hanging" poultry
It is the practise in some oriental and European countries to "hang" poultry for a few days before they are eaten. This process, as in the case of ripened meats, is simply one of partial decay. The enzymotic action taking place in the meat is arrested only by the process of cold storage. Decomposition proceeds slowly until it reaches that point when it is pronounced high-flavored and "ripened." This is very largely practised in this country at the present time. It is a custom that is instinctively condemned by everyone from the standpoint of both hygiene and aestheticism. The people should demand and force Congress to pass a law labeling all cold storage meats with the date of slaughter, and all canned meats with the date of packing.
Slaughter of game as sport, a step backward
What is true of domestic poultry is also true of all wild game. The amount of actual food contributed to the world by the slaughter of game is exceedingly small. A similar quantity of domestic food could be produced at one-tenth the cost of time and labor, without slaughtering the wild creatures of our forests. The popularity of hunting as a sport, and the idea that the flesh of all wild animals is a rare and dainty article of diet, is merely an illustration of anthropoid inheritance. It is a step backward toward savagery instead of forward toward a higher civilization.
EGGS
Eggs and milk occupy a unique place in the catalog of foods. The purpose for which they were produced in nature throws much light upon their value as food.
Every form of life exists for itself alone
As will be learned from the lesson, "Evolution of Man," no living creature exists for the sole benefit of other creatures, but because once created, the inherent struggle of all living matter to survive and to reproduce itself has evolved wonderful and various adaptations. Every organic substance is primarily produced in nature for a specific purpose in the life of its species. The lumber in our houses owes its existence to the plant's struggle for sunlight, which made it necessary for the tree to possess a strong storm-withstanding stem to hold aloft its leaves above the shade of other foliage.
The leaves and the stems of grass are primarily an essential part of the life of the plant, and not food for animals. The greater part of the human food of plant origin represents in nature the nutrient material supplied by the parent plant for the early life of the seedling. All grains, nuts, fruits and roots, and tubers are merely modified forms of food material adapted to the rapid nourishment of the young plant.
The starch and the oil of seeds, the sugar of fruit, and the lesser quantities of nitrogen contained in all seeds, are in a more available form for cell-nourishment than would be the original mature portions of plant life.
Milk and eggs in the animal world occupy a position identical to that of seeds and fruit in the plant world; that is, they are created for the first nourishment of the offspring.
In the process of evolution, a fundamental distinction between birds and mammals is in the manner in which the young are nourished. The egg of the bird supplies sufficient nourishment to develop the young bird to a point where it can exist upon the ordinary food of the adult bird.
The hen's egg must contain all food material necessary to form all portions of the body of the chick, and to supply it for a time with heat and energy.
Composition of eggs
An average egg weighs two ounces; of this weight about 10 per cent is shell, 30 per cent yolk, and the remainder white. The white of the egg is composed of albumin and water. The yolk consists of globulin, egg-fat, and lecithin; this latter substance contains a considerable proportion of phosphorus, and is one of the essential contingents of brain and nerves. The egg-shell contains 13 per cent protein, 10 per cent fat, and one per cent ash.
The younger the animal, the more rapid is the growth of the animal body compared with the amount of energy expended. Milk and eggs not a balanced adult diet For this reason the percentage of nitrogen in milk and in eggs is much too great to form a balanced adult diet, and should be supplemented by articles containing larger proportions of heat-producing materials, preferably carbohydrates.
Eggs for emaciation and convalescents
The proteid material of eggs is in a form especially adapted to the construction of new cells. For this reason it is one of the best known foods for use in cases of emaciation, where new tissue is to be added rapidly to the body. An egg contains about fourteen decigrams of nitrogen. Ten eggs, therefore, would supply an ample amount of nitrogen for the daily needs of the average body, were no nitrogen taken from other sources. In feeding patients who are convalescing from fevers or other wasting dis-eases, it is sometimes necessary to prescribe a diet of from ten to twelve eggs daily for a limited time.
The consumption of five eggs a day, when we rely wholly upon this article for animal proteids, is quite sufficient for one performing ordinary labor, when supplemented by one succulent and one tuber vegetable.
MILK
Milk the best animal food
Milk and the various products made therefrom constitute one of the most important groups of food in the modern bill of fare. Milk and eggs are interdicted by some vegetarians, but aside from the sentimental feeling against the taking of any food of animal origin, there are no scientific reasons for such exclusion. Dairy products are free from many of the objections assessed against the use of flesh, and they supply a number of readily soluble, digestible, and assimilable nutrients that, in many respects (curative and remedial feeding), excel anything that can be secured from the vegetable kingdom.
Results of special feeding
The composition of cow's milk varies widely. Dairy cows, by long domestication, breeding and feeding, have been brought to a high state of specialization. Some breeds have been so trained, fed, and bred as to produce large quantities of milk. Some Holsteins have been known to produce one hundred pounds of milk per day each, which of course is many times the quantity required for the nourishment of their young. Some Jersey stock have been so bred, raised, and fed as to produce large quantities of butter; in some cases the butter-fat of especially fed Jerseys has been known to run as high as 8 or 10 per cent, whereas the normal fat content of milk is not more than 3.5 or 4 per cent.
The average composition of mixed milk from many cows runs about as follows: Water, 87 per cent; lactose or milk-sugar, 4.5 per cent; butter-fat, 3.5 per cent; ash, .7 per cent; proteids, 3.3 per cent, of which about 2.5 per cent are casein, and .8 per cent albumin.
Value of milk depends upon its nitrogenous content
The commercial value of milk is measured almost entirely by its content of butter-fat. This is because the public knows practically nothing about the food value, or the chemistry of milk, therefore its value is estimated upon that which can be seen, and upon that which tastes best. The chief value of milk as a food lies in the nitrogenous element it contains. Fat can be secured from many other sources.
The nutritive elements of milk from various animals vary according to the natural requirements of the young of various species.
Cow's milk contains too large a proportion of casein, and not enough milk-sugar to meet the natural requirements of the human infant. This subject, however, will be discussed at length in Lesson XVI on "Infant Feeding," Vol. V, p. 1154.
Coagulation of casein in milk
The casein in cow's milk is coagulated by the hydrochloric acid of the stomach, which forms into lumps or curds, rather difficult to digest. This can be overcome or counteracted in several ways. First, if milk is allowed to sour or clabber, the casein is coagulated by nature, which is really the first process of digestion. In this form it neither burdens the digestion nor causes the supersecretion of hydrochloric acid, which is likely to occur when sweet milk is too liberally used. Second, the sipping and thorough insalivation of milk, by taking it into the mouth with something that requires thorough mastication, insures better digestion and assimilation, and less liability to produce intestinal gas.
Milk will harmonize chemically with all non-acid fruits, cereals and nuts. Milk is in chemical harmony with meat and eggs, but all of these articles being highly nitrogenous, when taken at the same meal, the portions should be limited to the minimum.
Milk should not be combined with acid fruits, especially those of a highly acidulous character, such as lemons, limes, grapefruit, pineapples, etc. (See Lesson VIII, Vol. II, p. 314.) Neither should it be taken at the same meals with succulent plants, such as lettuce, watercress, romaine, parsley, etc.
Milk for sour or acid stomach
When the stomach has long been over-burdened with food, and made the receptacle in which acid fermentation has taken place until the mucous membrane has become irritated or probably ulcerated, there is no food so acceptable as milk. For the common disorder of hyperchlorhydria, which is a term used to describe a condition of chronic sour stomach or supersecretion of hydrochloric acid, milk is one of Nature's best counteractive food nutrients. (See "Superacidity," Vol. II, p. 418.)
In cases of severe constipation or alimentary congestion, milk should be given as follows:
Milk diet for constipation
Omit breakfast. Begin about 9:30 taking an ordinary glassful of fresh, cool milk every twenty or thirty minutes, until about one and one-half quarts have been consumed. After two or three hours, repeat the same process until about two quarts more have been taken. With each quart of milk, from three to four heaping dessert-spoonfuls of clean, wheat bran should be taken, in thin cream or rich milk. At noon and at evening a few tablespoonfuls of coarse cereal (wheat or rye flakes), might be eaten. They should be masticated thoroughly, and eaten with nuts and a limited quantity of cream. Under this regimen I have known the most severe cases of constipation to yield readily, and the patient to make a gain in weight of half a pound daily for a period of from twenty to thirty days. If the appetite should rebel against taking milk in this quantity, the amount should be reduced, and a cupful of soaked evaporated apricots taken at night just before retiring, and in the morning, just after rising.
When milk is taken for the purpose of counteracting a congested condition of the bowels, or an irritated condition of the mucous membrane of the stomach, it should be combined with the fewest possible things—one coarse cereal only will give the best results. A large quantity of milk, three and one-half to four quarts taken daily, as above directed, will act as a laxative, while a small quantity will have a tendency toward constipation.
THE ADULTERATION OF MILK
The old method of adulterating milk with water has very largely gone out of practise, owing to the surveillance of city authorities, and the passing of laws that fix legal standards, which require milk to contain a certain percentage of fats and total solids.
Evil of milk preservatives
The chief form of criminal tampering with milk has been the use of preservatives to prevent souring. Formaldehyde has been used very extensively for this purpose. Formaldehyde is a poison, destructive to all cell life, and has probably been the cause of more actual deaths than any other form of food adulteration.
MILK PASTEURIZATION
Pasteurization, which takes its name from Pasteur, the French bacteriologist, is merely a process of heating milk to about 170 degrees Fahrenheit for the purpose of destroying possible dis-ease germs, and the bacteria that produce fermentation. In this process the milk is not allowed to come to a boil for the reason that boiled milk is rather "dead" or distasteful, and would readily be detected by the public. It is quite evident that any method of Pasteurization, which would kill bacteria, would also cause coagulation of the protoplasm and the albumin of the milk, and render it much less nutritious, and much more difficult to digest.
Virtue of naturally soured milk
If milk producers and dairymen understood the superior food and remedial value of naturally soured milk, and would exert some effort to educate the public in its use, they would soon establish a new and profitable industry, and would give the dairy business of the whole country a new commercial impetus. The souring of milk can be prevented by cleanliness, which renders Pasteurizing unnecessary. At the time of the Paris Exposition, a dairy farm in Illinois sent pure unpasteurized milk to Paris, which arrived in an unsoured condition. This was achieved by absolute cleanliness, with the cows, dairy utensils, etc.
CHEESE
Cheese consists of the coagulated casein of milk, together with the fat globules that may be mechanically retained. Cheese is made by coagulating the milk with rennet, which has been extracted from the stomach of a calf, the sugar of the milk being passed off in the whey, and lost.
Schmier Käse or cottage cheese is formed by allowing the milk to sour, and to coagulate by gradual warming. This cheese is usually made from skimmed milk, hence contains practically no fat.
The several processes of making cheese
The cheese of commerce is ripened in various ways. The process of ripening is due to the action of enzyms present in the milk, or to those formed by bacterial growth. Ripened cheese is considered to be more easily digested than the unripened product. The best that can be said of this process is that the ripening of cheese is perhaps the least objectionable of all processes of decomposition taking place in food proteids. The only benefit that can be claimed is one of flavor, and, in matters of flavor, the appetite for Limburger, and similar cheeses, is at least a cultivated taste that furnishes evidence neither of merit nor of nutrition.
In the manufacture of cheese, the milk, sugar, and a part of the albumin and fat are wasted, and as there are no advantages in taking the milk in this changed form, there exists no scientific reason for the use of cheese when fresh milk can be obtained.
BUTTER
Butter constitutes one of the most wholesome and palatable of all animal fats, and is probably one of the most extensively used articles of food of animal origin.
When the pure butter-fat has been separated from the casein of milk it can be kept sweet and wholesome for a length of time sufficient to transport it, and to pass it through the various links in the chain of commerce, so that it can reach the family table a long distance from its source of production. This, in addition to man's instinctive relish for dairy products, makes butter the most popular fat in the diet of civilized man.
Fresh butter made in the home
In prescribing butter-fat, however, it is advisable to nominate fresh, unsalted, or what is commonly termed "sweet" butter. It is also advisable for the practitioner to suggest that this can be made daily, merely by whipping either sweet or soured cream with an ordinary rotary egg beater until the fat globules have separated from the whey.
Pure butter contains about 3,600 heat-calories to the pound, and therefore constitutes one of the most important and readily convertible of all winter foods.
If no other fat is used, about two ounces of butter each twenty-four hours is sufficient to give the ordinary body, under a temperature ranging from forty to sixty degrees above zero, the required amount of heat.
OLEOMARGARIN
Oleomargarin is a general term that includes all manufactured preparations of fats which imitate dairy butter.
Oleomargarin is manufactured by combining beef-fat with cottonseed-oil until a product is formed which has a melting point similar to that of butter. Lard is also used in some oleomargarin products. This combination of fats is then churned with either cream or milk and dairy butter is frequently added so as to give to the artificial product the pleasant flavor or odor of dairy butter. There is much popular prejudice against the use of oleomargarin, but when made under hygienic conditions, and by cleanly methods, it is practically as digestible, and quite as wholesome as the dairy product.
Transcriber's notes:
P.64. 'NaCL' changed to 'NaCl'.
P.236. 'vegetarianisn' changed to 'vegetarianism'.
P.238. 'escargoes' changed to 'escargots'.
Both dis-ease and disease are found in this book, leaving as it is.
Fixed various punctuation.