FOOTNOTES:
[4] Charles D. Woods, Dr. Sc., in Cereal Breakfast Foods.
CHAPTER IV
BEVERAGES
Beverages are used primarily to relieve thirst; they may also contain food elements; they may be used for their effect in heat and cold, for their flavor, which helps to increase the appetite, or for their stimulating properties.
They are used to aid digestion and the elimination of waste, to promote sweating, to soothe inflamed air passages or digestive membranes. They furnish extra nutrition, stimulate nerve action, quench thirst in fevers, warm the body when it is cold or cool it when it is hot. They are used in health or disease, from the snows of the arctics to the palms of the tropics. They may be alkaline or acid, mineral, medicated or mucilaginous, effervescing or plain. The question of their utility and preparation is important in any discussion of foods and food products, though in themselves they are not foods.
The people of all races seemingly crave a stimulant, after bodily or mental exertion, in fatigue, as a “bracer” in prolonged effort, as a promoter of sociability, or as an offering of hospitality. These stimulants are either alcoholic or non-alcoholic.
It is a notable fact that no tribe is so remote that it does not possess some form of beverage which may be offered to friends or used to promote feelings of conviviality; or it may be used to stir up rage if onslaughts against neighboring tribes are contemplated. The craving is universal and as old as the race.
Those who decry this craving when it takes the form of alcohol are often themselves addicted to excessive drinking of non-alcoholic stimulants.
Tea
Tea is not a food—it is a stimulant. It is made by steeping the leaves of a shrub, called Thea, which grows in the tropical regions of Asia and adjacent islands.
Green tea differs from black in the mode of its preparation. In green tea the leaves are steamed before they are dried.
The amount of tannin in green tea is greater than in black, hence green tea is regarded as not so wholesome a drink as black tea.
The young tender leaves are more delicate of flavor.
Varieties of plants differ both in the amount of tannin and the delicacy of flavor.
Tea should never be boiled or allowed to stand longer than a few minutes; standing causes the tannin to be extracted from the leaves, and this tannin disturbs digestion. It is the tannin extracted from the bark of trees which toughens animal skins into leather.
The best way to make tea is to pour on boiling water and serve within five minutes.
Because of the uncertainty as to the length of time tea may be allowed to steep in hotel kitchens or restaurants, it is a wise custom to have a ball of tea and a pot of hot water served that the guest may make the tea at the table.
Tea is diuretic, stimulating the action of the kidneys. Through its stimulant action it relieves fatigue and has been found especially useful in Arctic explorations and for soldiers on long marches.
When taken hot it will often relieve sick headache. When taken on an empty stomach, after a long fatiguing tramp or a prolonged “shopping” excursion, its refreshing effect may be felt for an hour or two.
The ease of its preparation and the quickness of its effect tends to produce the “tea habit.” When drunk to excess with meals, it causes the precipitation of the ferments in the digestive juices, retards digestion, and may cause constipation, particularly if taken after long infusion.
Strong tea has an overstimulating effect on the nervous system which reacts, producing depression and restlessness; this may lead to insomnia, muscular twitchings, and palpitation of the heart.
Habitual users often take from ten to twenty cups of strong tea daily; in these the evil effects of the tea habit are easily noted.
Americans, or any people whose nerves are highly stimulated, from the stress of life, or from habitual nerve tension, should particularly avoid all stimulating beverages.
Poor tea, because of the greater amount of tannin it contains, produces its ill effects more quickly. From overstimulation of the nervous system, poor tea, long stewed, has been held to be a contributing factor in insanity.
Tea should be avoided by the dyspeptic, by those of constipated and flatulent habit, or by the anemic.
Tannin coagulates the albumin in milk or cream and the addition of these to tea renders it more indigestible; plain or with lemon juice it may be well borne by those with whom it disagrees when used with cream or sugar.
Thein, the active principle in tea, is chemically identical with caffein in coffee.
Coffee
Coffee is prepared from the seeds of the coffee tree. The best known brands come from the Island of Java, Mocha, Rio de Janeiro, and Mexico.
Coffee, like tea, is not a food, it is a stimulant.
The active principle is caffein. This is an alkaloid and is a strong stimulant to the central nervous system. It quickens the heart action, and the stimulating effect is so apparent with many, that they cannot sleep for several hours after drinking it. Others drink coffee to quicken mental activity and to keep them awake.
It must be borne in mind, however, that there is a reactionary effect from all stimulants, and while coffee is not intoxicating, as alcohol, it has a similar effect on the nerves and heart.
Coffee has the redeeming feature of having a pleasing aroma, which, because of the effect on the mind, may incite the flow of gastric juice. Despite the fact that no morning beverage has quite the same pleasing aroma, or pungency, ordinarily one is much better without it.
Coffee stimulates the action of the heart and for this reason it is used in collapse to restore heart action.
It removes the sense of fatigue and is thus beneficial in some cases, as in the army, when long marches are necessary.
It is valuable as an antidote in opium poisoning or in cases of alcoholism.
It is given to those addicted to liquor, as a milder stimulant when they are recovering from a spell of intoxication.
The only use of coffee as a food is that its pleasant aroma stimulates the flow of gastric juice.
Strong coffee, particularly that which has been boiled for a long time, retards digestion, and, if much is drunk, it will produce the same symptoms of over stimulation of the nervous system as are manifest in the tea habit. Heartburn, constipation, dyspepsia, and insomnia may result.
Sometimes the habit is manifested by excessive eating of the coffee bean. Such users show marked symptoms of nervousness; they are usually thin and their faces are drawn and anxious.
Each person must decide for himself whether or not coffee or tea is injurious to him and cease the habit if he finds it is interfering with the proper functioning of the system, remembering always that the purpose of food is to resupply body waste and produce heat and energy.
One who knows that coffee disturbs his digestion, and yet cannot break himself from the habit of drinking it, should have sympathy for the one who is addicted to liquor and finds it difficult to break the habit of depending on this so-called stimulant.
Cereal Coffee has been discussed under the heading “Cereals.”
“Crust” coffee is made by pouring boiling water on “caramelized” bread or bread deeply toasted, allowing it to stand ten minutes, then pouring off the liquid, which may be sweetened to taste or mixed with cream or milk. It is also made by using crusts of bread which have been dried in the oven without being allowed to brown.
Cocoa and Chocolate
Cocoa and Chocolate are prepared from the cocoa bean.
Cocoa is from the shell of the bean and chocolate from the kernel. As shown by Table [VII], they are more nutritious than the other beverages.
Cocoa butter is the fat of the cocoa bean. It has a pleasant odor and does not easily become rancid. Its nutritive value depends on its fat.
Most of the fat has been removed from the cocoa made for the use of invalids, hence the nutritive value of this cocoa is lessened. The milk and sugar used in its preparation constitute the most of its nourishment; the cocoa simply gives a flavor.
Part of the value of chocolate is in the sugar used with it. If well prepared it is digested with ease and forms a nutritious article of diet. The habit of using large amounts of chocolate in candy, or as a beverage, disorders the system because of the gastric disturbances produced by the excess of sugar.
When food is not easily obtained, compressed cakes of chocolate may be carried, as in traveling, for a temporary food supply.
Chocolate, as sugar, in moderation, constitutes a good food for the growing child.
The active principle in cocoa and chocolate is theobromin and, though milder, is similar to caffein in its stimulating effect on the nervous system.
Lemonade
Lemonade and other fruit drinks, particularly those made from the citrus fruits, slake the thirst more quickly than most drinks.
All fruit drinks are diuretic, and, whenever the action of the kidneys is sluggish, they are especially desirable.
Effervescing Waters
These are made by forcing carbon dioxid, under pressure, into the bottle. As soon as the cork is removed the escape of the gas causes effervescence. These drinks are of no special advantage, other than that they slake the thirst, because the amount of salts of various minerals they contain is usually small.
When taken in excess they cause flatulence and may lead to gastric disturbances. The indiscriminate habit of young people drinking effervescing waters at soda fountains should be discouraged.
These waters added to milk render it more easily digested.
Water
There is no beverage nor concoction devised by man equal to water. It is to be deplored that it is not used as freely as Nature demands—from eight to ten glasses a day.
The value of water as a food and as an aid to digestion is discussed on page [26].
CONDIMENTS
Condiments are not foods. They have no nutrition in themselves, but by their flavor they stimulate the nerves of taste, rendering the food more appetizing and help to make the diet more varied.
They are relishes and are to be employed in this manner judiciously, and not used generally in the diet.
Some strong condiments, as cayenne pepper, are of use in dyspeptic conditions to stimulate the gastric mucous membrane.
They are of value in the dietary of the invalid whose appetite must be stimulated and careful variations in flavoring will aid in varying a diet which otherwise would be monotonous, but the excessive use of condiments, particularly the various peppers, salt, horseradish, ginger, vinegar, and spices, as indulged by many, so overstimulates the gastric and intestinal membranes, as to cause catarrhal disease and dyspepsia. They tend to weaken digestion by calling for an undue secretion of digestive juices, which, if prolonged, tires out the glands.
The use of salts is discussed on pages [34-37].
A reasonable amount of condiments such as pepper, salt, nutmeg, cloves, allspice, sage, thyme, ginger, mustard, cinnamon, mace, horseradish, vanilla, dill, etc., may be used as appetizers, because the pleasing thought of them may incite the flow of gastric juice; but they should not be used to excess.
The taste is undoubtedly a cultivated one, and should not be encouraged in children. The child rarely cares for condiments and it is better that he continue to relish his food in its natural flavor.
If beef tea, which so soon becomes distasteful to the sick, is flavored with different savory or aromatic substances, as parsley, sage, or mint, it is taken with greater relish.
Mustard, so commonly used with cold ham or other meat and in salad dressing, is sometimes of benefit in stimulating the appetite, but when used in large quantities, or continuously, it may irritate the stomach. This irritant quality may be used to advantage, when it is deemed necessary, as a counter-irritant on the skin, as in the well-known mustard plaster. A teaspoonful of mustard to a pint of lukewarm water is an effectual emetic in cases in which it is necessary or advisable to empty the stomach.
Capers, the flower buds of a bush grown in the East, are put up in vinegar and used in sauces for mutton.
Cinnamon, nutmeg, and cloves are useful in flavoring foods; they take the flat taste from hot water and impart a pleasant spiciness. Many can take milk when flavored, and the slight amount necessary is in no way injurious.
Preserved ginger is of value for flavoring cereal foods and gruels for invalids.
Vinegar, used in excess, reduces the alkalinity of the blood and aids in the destruction of red blood corpuscles. It may thus produce anemia when used in excess.
The acetic acid contained in cider vinegar aids the softening of the muscle fiber of meat and thus facilitates its digestion. Because of its preservative qualities it is used in pickling vegetables and various kinds of fish.
Vinegars made from grapes or other fruits are wholesome. Flavored vinegars, as tarragon, from the herb of the same name, are useful as appetizers.
Vinegars artificially made from commercial acids are sometimes injurious.
Tomato Catsup, Worcestershire, and Tabasco sauces are not harmful if used moderately and with due regard to enhancing not destroying the flavor of the food with which they are used.
PRESERVATION OF FOODS
This subject is of ever-growing importance. The study of the preservation of foods has added much to the store of human knowledge. By this means it is possible for those living in districts remote from the supply, those who cannot afford to buy them fresh, and those who have no cellars in which to store them, to have vegetables and fruits at all seasons of the year.
Nutritious foods can be prepared in such small bulk and of such excellent keeping quality that explorers, whether to the arctics or the tropics, can be kept in first-class physical condition, enabled to withstand fatigue, and be removed to long distances from the base of supplies without great hardship.
The decomposition of food is occasioned by bacterial action. Air is necessary to the growth of bacteria. If the air is excluded the ordinary bacteria are prevented from exerting their deleterious action.
Heat, as in canning, prevents the formation of bacterial products.
Cold, in refrigeration, by inhibiting bacterial activity is also an excellent preservative.
Other methods in use are smoking, salting, drying, sterilizing, various antiseptics, and the exclusion of the air, as in coating eggs or meat for transportation to other countries.
Eggs are preserved for a long period by excluding the air, which otherwise penetrates the shell. A solution of water glass (silicate of sodium), dry oats or salt are used for this purpose.
All food intended for preservation should be kept in a clean, cool, dry, dark place.
Drying, cooking, and sealing from the air will preserve some meats and fruits, while others require such preservatives as sugar, vinegar, and salt. The preservative in cider vinegar is acetic acid, in wine vinegar tartaric acid.
All preservatives which are actual foods, such as sugar, salt, and vinegar, are to be recommended, but the use of antiseptic preservatives, such as salicylic acid, formaldehyd, boracic acid, alum, sulphur, and benzoate of soda, all of which have been used by many canning merchants, is fraught with danger. By the efforts of the United States Department of Agriculture the use of such preservatives has been largely done away with by the most reliable packers and canners. However, unscrupulous dealers may use this means of disguising fruits and vegetables not in good condition.
There can be no doubt, that, whenever possible, the best method is for the housewife to preserve her own food by drying, canning, preserving, and pickling, with fruits and vegetables which she knows are fresh. This, however, is not always practicable.
Since economy in food lies in obtaining the greatest amount of nutriment for the least money, the preparation of simple foods in the home, with care that no more is furnished for consumption than the system requires, is the truest economy.
More brands of prepared food are not so much needed as purity of elements in their natural state.
In the effort to emphasize the importance of pure food in amount and quality, pure air and pure water must not be overlooked. Much infection is carried by these two elements.
POISONING FROM FOOD
Owing to the careful inspection given to various preparations of foods and the education of the people on the dangers attending the eating of underripe, overripe, or fermenting fruits and vegetables, or decomposing canned meats or other foods, cases of poisoning from food are not so numerous as formerly.
One still reads, however, of illnesses and even fatalities in those who have, at some gathering, partaken of potted or canned meats, or ice-cream made from impure milk.
Imperfect sterilization allows the micro-organisms, everywhere present in the atmosphere, to multiply and produce their toxins.
Any food contained in a can which shows a suspicious bulging in top or sides (not a dent caused by handling) should be unhesitatingly rejected, for fermentation has developed gases, which, in trying to escape, have caused the bulging. Though the practice is less common than formerly, some grocers offer these bulging cans for sale at less prices and they are thus purchased by those who look for bargains in foods instead of for quality.
Sometimes the foods have not advanced to a stage in which the poisonous products are manifested; but in the intestinal canal the germs contained in these foods manufacture toxins which are readily absorbed and produce the severe disturbances noted in cases of ptomain poisoning.
The liver, which has been styled the “watchdog of the body,” has a special power to destroy many of the toxins contained in the food material passing through it, and it is due to this fact that many deleterious substances, taken with the food, are neutralized and their poisons rendered harmless to the system. When the liver is disordered, this important function may be hindered, or cease to be active. Therefore, the importance may be readily seen of keeping the liver in a vigorous condition by means of exercises which will send an active circulation through it and keep the nerves controlling it in perfect functioning order.
Ptomain poisoning results most often from tainted meat, milk, and fish. Putrefactive processes may have begun in meat, which is thus rendered “high,” but if it is thoroughly cooked the poisons may be made inert. Many enjoy the flavor of such meat. The Eskimos, as is well known, will cache a seal or other animal against a time when food is less plentiful and after months, perhaps, will eat it with relish and without harm, though it cannot be touched by people with less hearty appetites. Old eggs, eaten as a luxury by the Chinese, and the fermented fish used by other races are familiar examples of tainted foods.
The sale of “bob” veal, or the flesh of very young calves, has been prohibited because in many people its ready decomposition causes active diarrhea.
The process of smoking various meats affects materially only the outside portion, the inner may furnish a suitable bed for the development of germs. Great care should be exercised and thorough inspection made of any meat which is eaten raw, as dried beef, or any pork product.
Ice-cream, as made in the home, is usually innocuous, but when it is made in factories, unless care is exercised to keep containers clean and sterilized, the cream or milk may become infected from careless handling, either before or after it reaches the factory—particularly in warm weather. Toxins which cause serious and often fatal poisoning develop. Many such cases have resulted from the free eating of infected ice-cream at picnics or other social gatherings.
One should guard against overripe cheese, though cheese of any kind acts as a poison with some people. Cases of severe intestinal disturbance may occur in those who are unable to eat certain articles of food, as strawberries, lobsters, or oysters; these attacks should be carefully distinguished from cases of true poisoning.
Sometimes, however, particularly in the case of fish or oysters which have been frozen, unless they are eaten immediately after they have been thawed, toxins develop which cause severe constitutional disturbance, particularly of the nervous system. These toxins do not seem to affect the gastro-intestinal tract so markedly. Infected shellfish, particularly mussels, have caused death in two hours by their effect on the nervous system.
Many fish after being smoked are eaten raw, and if the ptomains have begun to develop, poisoning follows.
Care must be taken in purchasing fish for the table that the flesh is firm and the odor absolutely without taint.
Meat or fish may become toxic to the system through substances eaten by the animal or by its own physical condition at the time it is killed. Fish and oysters, therefore, are not eaten during the spawning season.
Cow’s milk may be made obnoxious by substances on which the cow feeds. Wild garlic when eaten by the cow imparts a nauseous taste to the milk.
The flesh from diseased animals slaughtered and sold for food has occasioned violent sickness. Government inspection, however, has greatly lessened the dangers from this source.
Unripe or overripe vegetables and fruit may occasion severe vomiting and diarrhea.
Moldy flour contains a substance which may cause poisoning.
Rye may have a parasite fungus called ergot and if flour is made from rye contaminated with this growth, a form of poisoning called “ergotism” may result. It takes some time and a prolonged use of the flour to cause untoward symptoms.
Pellagra, which has been giving the southern states so much trouble, was thought to be caused by the use of spoiled corn meal. It is now thought to be due to the disturbed nutrition following too monotonous and unbalanced a diet. The excessive use of corn-meal breads with their heating qualities and the irritation of the intestinal canal may be an accessory factor.
A food which is so universally used as milk should be surrounded with every safeguard possible by rigid inspection from producer to consumer, as many infective epidemics have been traced directly to a careless or infected handler of this product. Tuberculosis and typhoid fever germs, diphtheria and scarlet fever may all be communicated by this means. Live typhoid bacilli have been found in acid buttermilk. Infected water used in washing the cans will infect the milk.
Other poisoning may occur by the tin or lead in the inside of cans being dissolved off by the acids in fruits or vegetables. This is more likely to occur when the cans of fruit have been kept for a long time. Housekeepers, who use tin cans, should not put up more fruit than will supply the family for the season.
Tomatoes, asparagus, strawberries, and apricots are especially liable to dissolve the tin from the can.
Food should be emptied from the can as soon as it is opened, as the action of the air hastens deterioration. No cooked fruit should be allowed to stand in a tin saucepan or other vessel. It should be emptied as soon as the cooking process is complete.
When a can of fruit, vegetables, or meat is opened, if the interior of the can is even partially black, it is safe to reject the contents. The tin in the food will be absorbed in the intestinal tract and may cause severe disturbance.
Large canners of fruit and vegetables, of the better quality, are now coating the inside of the can with an insoluble varnish which prevents the acids from acting on the tin.
The best canners are exceedingly careful and everything in their factories is scrupulously clean.
THE ADULTERATION OF FOOD
Laws against food adulteration have been enacted, but unscrupulous manufacturers find ways to evade them. On account of these laws, however, the practice is less general and manufacturers are beginning to take pride in putting up goods that pass the strictest inspection. The people, also, are being aroused, through the efforts of the pure-food propagandists, to the ill effects of adulterated foods both on the body and the pocketbook and are increasingly demanding that the foods they buy shall be pure and wholesome.
To lessen the cost of production, many foods are mixed with various substances before being marketed in order to increase the profits of the manufacturer or dealer. The contained substance may not be deleterious to health, but it may lessen the value of the article as a food.
Among foods which may be so adulterated are jellies, jams and marmalades, catsups and pickles of all varieties, baking powder, butter, spices, coffee, corn-starch, mincemeat, vinegar, syrups, sugar, honey, lard, and flour.
Various adulterants which are used are: wood alcohol (a poison) in flavoring extracts; vinegar made from various acids and colored to imitate cider vinegar; rice flour and wheat flour used in ground spices; kaolin and coloring matter used in candies; paraffin in gum drops; glucose artificially flavored as maple syrup; cotton-seed oil sold as olive oil; starch and sugar in powdered cocoa and in chocolate; chicory, sugar, and pea meal in ground coffee; artificial coffee beans made of starch, molasses, and chicory; alum and ammonia in baking powders; artificial coloring of canned peas, beans, and catsups, butter, cheese, milk, and cream.
It must be said, in justice, however, that housewives are responsible for many of these productions. Dealers who would be glad to sell only pure articles say that “the trade won’t have them.”
Many insist on a highly colored cheese, thinking that the color denotes greater richness, whereas a little reasoning would show them that the richest old cheeses are pale in color, the deeper color of the cheese being due to the addition of coloring matter to the curd. While the coloring matter is not deleterious, the color is no evidence of richness.
Highly colored green pickles, beans, and peas, should not be used. Pickles which are hard and crisp are usually made so by alum.
Brilliant red catsup is in demand, though the pure variety is known by its darker and not so attractive hue.
High coloring in any canned fruit or vegetable is usually an indication that dye stuffs have been used to produce it.
Fruit jams which are of nondescript color or pale when pure are colored artificially because the ordinary purchaser demands a pretty product.
Through the vigilance of the food inspectors of the boards of health, and because of some vigorous prosecutions, the adulteration of the people’s food is, however, not so easy and profitable an occupation as formerly.
The Bulletins of the Department of Agriculture furnish a mine of wealth in the gaining of knowledge of various foods and their preparation, and may be had free on application to this Department at Washington.
HEAT AND ENERGY
The second use of foods, as mentioned before, is to furnish heat and energy for the work of the body. Heat and energy are produced automatically by the action of the heart, the movement of the lungs in breathing, and by muscular activity through the digestion, absorption, and assimilation of food elements, and through the activity in tearing down and eliminating waste. They are produced consciously by muscular activity in exercise.
Just as any engine requires fuel, water, and air to create the force necessary to run the machinery, so does the human engine require fuel, air, and water.
The fuel for an engine consists of coal, wood, or oil. As these are brought in combination with oxygen, combustion or oxidation takes place, liberating heat and setting the engine in motion.
The amount of energy or force given off by an engine should exactly equal the amount of latent energy provided in the fuel. Much of this energy is commercially lost, since much of the latent force in fuel is not fully liberated, some passing off in the smoke, while some may remain in the cinders.
The amount of heat and energy generated by the body equals the amount of latent energy released by the burning of food material during oxidation.
The carbohydrates and fats constitute the most of the fuel.
The body cells are constantly surrounded by the lymph which contains the food material—the protein, the carbohydrate, and the fat.
The lymph carries all of the food elements, therefore the protein, the fat, and the carbohydrate reach the tissues at the same time. If the fat and carbohydrate predominate, their excess serves to keep a portion of the protein away from the cells. The cells can use carbohydrate more easily than fat, so the surplus amount of carbohydrate is first used to produce energy. This spares the protein which is held in reserve for tissue repair, and the fat, being least readily used, is stored.
When the carbohydrates and fats are not supplied, or when the system fails for any reason to appropriate those eaten to its use, the protein is used for heat and energy instead of being used for tissue building. If the demand, either in mental or physical energy, exceeds the daily supply for long, the body becomes lean.
In order, therefore, to maintain a perfect equilibrium the supply of protein, carbohydrate, and fat should bear the proper relation, any excess at one time being equalized at another. If an overhearty meal is eaten the next should be light.
Fat is harder to burn than the starches and sugars so that they are acted on first as an economy of effort, and the fat is held in reserve until the carbohydrates are exhausted.
If one is cold, the quickest way to get warm is to generate more heat within by “turning on the draught,” or, in other words, by breathing in more oxygen. If cold, one should depend more on the oxygen within than on extra clothing. So many people put on more clothing to conserve the body heat and forget to generate more heat by arousing the fires within. This is like covering a dying fire, instead of turning on the draught to create more combustion.
The carbon in the body is burned by being brought into contact with oxygen in the blood through exercise and full breathing, just as a fire is fanned to flame by bringing oxygen in contact with the fuel, by means of a draught of air. Keep all air away from a fire and it “dies out,” it has exhausted the oxygen and no heat is produced; keep all air from within the body, by cessation of breathing, and it also dies.
A room is heated with difficulty if the air in it does not contain sufficient oxygen. Just so the body which is not constantly supplied with pure air generates very little heat. The effect of oxygen in the creation of heat is practically demonstrated by voluntary, rapid, deep breathing, completely filling the lungs with air, while out in the cold. The body will become quickly warmed on the coldest day by this practice.
Ten to twelve deep breaths in succession “turn on the draught” inside and create combustion (heat), just as opening the draught to a stove by causing more air to circulate within it increases combustion or heat.
Remember that heat is the result of combustion—the more rapid the combustion in the body, caused by oxygen breathed in through the lungs, the greater the heat.
Just as much heat is created when fat is burned in the body as when it is burned outside of the body.
The heat from “burning” wood is produced by the union of the oxygen from the air with hydrogen and carbon, forming carbon dioxid and water.
The light in the burning of wood is caused by the rapid combustion. Combustion occurs within the body more slowly, hence no light is produced.
The exact process by which the potential energy latent in food is converted into heat and energy is not known. It is partly released during the digestive process, through the chemical action produced when the elements of the food come into contact with oxygen and with the digestive juices. This combustion gives to the digestive organs the necessary warmth to enable them to do effective work. A certain amount of heat is necessary for the chemical changes, and digestive juices flow more freely when the body is warm. Heat is necessary, also, to aid the peristaltic movements of the digestive organs.
It has been estimated that about one-sixth of the heat liberated evaporates through the skin, the lungs, and the excreta, while five-sixths is required to maintain the body heat.
If the digestive forces are not working perfectly and if the food is not properly prepared, some of the fuel is not utilized. But, in normal conditions, if the food is supplied in proportion to the energy required, the heat and energy given off should exactly equal the latent heat and energy consumed. If more food is taken than is necessary to produce heat and energy, the excess of material is stored and if the excess continues the bodily machinery may be clogged. The relief lies in consuming the excess through exercise. More oxygen is required to put the excess in condition for use, and the extra amount of oxygen is gained by means of the deep breathing occasioned by exercise.
It is to be noted, also, that no force within the body is lost. In the very process of the removal of waste, heat and energy are created, so that the parts no longer needed are utilized by the system, while they are being removed from it. Here is a lesson in economy of force.
A small portion of the heat of the body is gained from the sun or from artificial heat, but by far the greater part is generated within the body.
As mentioned before, the fuel for the body consists of fats, starches, and sugars, which, in combination with oxygen, create force.
From the foregoing, it follows that the fuel value of any food depends on the amount of fats, starches, and sugars it contains.
The chemical combination of oxygen with food elements and with the body tissue is known as oxidation. It is this chemical action of the oxygen on the food and on the tissues which produces heat and energy, either in muscle, gland, or nerve. This energy, in the muscle, expresses itself in movement; in the gland, in chemical action, and in the nervous system, by activity of brain or nerve centers. The nervous energy is closely allied to electrical force.
Nature provides for a reserve of heat and energy, above the immediate needs, by storing a supply of heat-producing material which is utilized whenever the daily supply is insufficient or is lacking. Many hibernating animals store up sufficient fat in summer to provide heat for the entire winter. This fat would not last throughout the winter, however, were the animal active. Many individuals carry sufficient fat to supply all of their needs for months, even though all fat-building elements were omitted from the diet.
The fact that more oxygen is required for combustion of fat than of starches and sugars is important for those who wish to call on the fats stored within the body for daily heat and energy and thus reduce in weight.
If sufficient starches, sugars, and fats are not consumed in the body to supply the daily heat and energy released by exercise, the body calls on the reserve store in the tissues. If much fat or carbohydrates are consumed in the daily food this will be oxidized before the fat stored in the muscular tissue is called on.
The scientific reduction of weight, therefore, lies in the regulation of the daily consumption of starches, sugars, and fats, and the oxidation of more of these substances through an increase in the daily exercise.
Deep breathing of pure air should accompany all exercises to supply sufficient oxygen for combustion or oxidation.
In warm weather little fat is needed for fuel, and Nature provides fresh green vegetables to replace the root vegetables of the cold weather, which, consisting largely of starches and sugars, are readily converted into heat.
In cold weather, especially in high altitudes or latitudes, more fuel foods are required to keep the body warm and more fat is eaten.
It must be remembered that anything which creates a greater activity of the tissues, such as muscular exercise, liberates a greater amount of heat. The reverse is also true. A decrease in the amount of muscular movement means a decrease in the liberation of heat. During exercise, a large amount of carbohydrates and fats are released by the movements and oxidized; the liberated heat is carried to all parts of the system and the temperature is raised.
Food in the alimentary canal causes an activity in the glands of the digestive organs maintaining their temperature.
Of course, while digestion and muscular activity are at their height, the body temperature is highest. The temperature, as a rule, decreases from about six at night until four or five in the morning, when it is usually at its ebb. This is a point of importance. A degree or two of increase in temperature, above normal, if recorded about six at night, is not, in most conditions, considered alarming by the physician.
Anything which causes an increase in heat radiation, as perspiration, lowers the temperature, and the open pores of the skin are valuable aids in equalizing the body heat. A person who perspires freely does not suffer with heat during excessive exercise, as does one whose pores are closed.
Diuretic foods and beverages, such as water and fruits (melons, lemons, oranges, grapefruit, etc.), which increase the activity of the skin and the kidneys, also tend to lower the body temperature.
One ready means of regulating the body heat is the bath. If one takes a hot bath, the temperature is materially raised by the artificial heat, but there is a recompense in the increase of heat radiation from the skin and the reaction is cooling. If one takes a cold bath, the immediate effect is cooling, but the activity set up within, to create a reaction, soon heats the body to a greater degree than before the bath.
The best way to increase the evaporation and thus decrease the temperature of the body is by a tepid shower or a tepid sponge. The tepid water will not create a strong reaction, and it will cause a decrease in temperature. Thus, for fever patients or on a warm day, the tepid shower or sponge is commended; for a cold day, or for the individual whose circulation is sluggish, the cold bath, followed by friction, is desirable. When the vitality is low, so that reaction is slow or chilly feelings persist, the bath must be tempered and greater friction used.
The generation of heat is also increased by solid foods that require more than normal activity on the part of the digestive organs. For this reason the food given fever patients should be that most easily digested and should be reduced in quantity. Liquid or semiliquid foods are best.
While the elements of the food are being oxidized, the latent (potential) energy released by the oxygen creates mental and physical force and keeps active the metabolic changing of food into tissues and cells, also the changing of cells and tissues into waste.
Scientists have measured the energy latent in food material, also the amount of heat given off in the oxidation of a given quantity of waste. The unit of measurement is the calorie—the amount of heat which will raise one pound of water 4 degrees Fahrenheit.
The fuel value of any food denotes the total number of calories which may be derived from a pound of that food if it be completely oxidized in the body.
C. F. Langworthy gives the fuel value of proteins, fats, and carbohydrates as follows:
| 1 pound of protein yields | 1860 calories |
| 1 ” ” fats ” | 4220 ” |
| 1 ” ” carbohydrates yields | 1860 ” |
That is, according to fuel value—the capacity of the nutrients for yielding heat and mechanical power—a pound of the protein of lean meat or egg albumen just about equals a pound of starch or sugar, and about two pounds of these would about equal a pound of the fat of meat or of the body fat.
The calculation has been made, based on experiments, that one who does no muscular work needs only an amount of food which will produce 2700 calories. One doing light muscular work needs 3000 calories. An individual doing moderately heavy work should take 3500 calories, while heavy muscular work takes 4500 calories.
One hundred grams of protein food, however, gives only fifteen per cent. of the amount of energy required. About 500 grams of carbohydrate and 50 grams of fat are needed to make up the 3000 calories which must be furnished by the daily supply of food for one doing light muscular work.
The brain worker, who is using brain tissue more rapidly than the day laborer, should have a diet equally as rich in protein, though less fat and carbohydrates are needed.
It has been estimated that an ordinary man on full diet excretes about twenty grams (about five-eighths of an ounce) of nitrogen a day. As protein material contains about sixteen per cent. of nitrogen, such an individual needs to take about 120 grams of protein a day to supply the nitrogen needs of the body. Because of its need for protein, the body does not store it.
A day laborer needs 0.28 of a pound of protein a day with enough fat and carbohydrate to give a fuel value of 3500 calories. A professional man requires 0.25 (1/4) of a pound of protein a day. Much more than this is usually taken. This means from 1/3 to 1/2 a pound of lean meat.
Nothing is lost in Nature’s distribution of force and energy. Everything accomplished in life, either in the physical handling of material, the brain work in planning the constructions, the mental movements of thought in art, literature, or science, are all representatives of the heat and energy released from the body, and every man and woman should endeavor to make the body yield as large an income as possible in the expression of this energy. In order that it may do so, it must be used with intelligence, just as any other great machine must be used intelligently; it must be fed, exercised, and rested judiciously.
CHAPTER V
REPAIR AND ELIMINATION OF WASTE (METABOLISM)
The work of the body never stops. If it is to be kept in thorough working order its tissues must be rebuilt as incessantly as they are torn down in the process of producing heat and energy. These chemical changes are called collectively metabolism.
They are divided into two groups: the chemical process of building up complex substances from simple ones is known as anabolism; the chemical process of oxidizing and breaking down the complex substances into simple ones, so that they are in a state to be excreted, is called catabolism. While the process of oxidation in catabolism is going on, heat and energy are set free. Many of the chemical changes in the body are catabolic in character. This work never ceases—even in sleep.
It is not enough that the proper foods be furnished the body in kind and quantity. The essential thing is that the system be kept in condition to assimilate the foods to its needs and to promptly eliminate the waste. Few people assimilate all of the foods eaten.
By assimilation is meant the process by which foodstuffs are made soluble and diffusible, so that they can pass into the blood; also, the metabolic activity by which the food is converted into cells and tissues.
Truly the body is a busy workshop. Think of the billions on billions of cells being formed and destroyed every instant in the liberation of heat and force! Think, also, of the necessity of perfect circulation to bring sufficient blood to the lungs, that it may gather the oxygen and carry it, without pausing for rest, to every tissue of the body! Even in sleep this stream continues incessantly.
There is also a great lesson here in the law of supply and demand. When the body is at mental or muscular work, the potential energy liberated leaves through muscle or brain, as energy, and is expressed in the result of the work. When the body is at rest, energy leaves it as heat (excepting such part as is necessary to carry on metabolism, circulation, etc.).
If much muscular energy is called for, a deep, full breath is instinctively drawn to supply the oxygen necessary for the added force.
If strong mental work is required, attention should be given to exercise and deep breathing, that the blood may carry off the waste liberated by brain activity. The difficulty is that in doing close mental work, the body is too frequently bent over a desk in such a manner as to restrict the action of the lungs; thus, the brain worker, in order to continue strong mental work, must often go into the open air, as he says, “to rest his brain,” but in reality to obtain the oxygen needed to put the waste, liberated by brain energy, in condition to be carried away. The supply of blood has been called on for the brain work; the poor circulation through the body has allowed an excess of carbon dioxid to accumulate and the condition of the body designated as “tired” has resulted. Until the necessary oxygen has been supplied, the brain and body are not balanced, not “rested.”
In its conversion into tissue, heat, energy, and waste, the importance of the chemical exceeds that of the mechanical action of digestion, absorption, assimilation, and elimination; yet the chemical changes are aided by the mechanical.
Nature provides against ignorance of the amount of supply necessary, by enabling the system to carry off a limited amount of surplus food above the bodily requirements. Her capacity in this regard is limited and varies with each individual. Therefore common sense is required in deciding for oneself the amount of food which will aid, and not hinder Nature in her processes.
Without doubt many eat more food than the system requires, and when it is overloaded they do not take the pains to burn up and eliminate the excess through exercise and oxygen.
On the other hand, this theory of overeating has been so long discussed that many have not eaten sufficient food and their bodies are undernourished. Many, also, from lack of exercise, hence lack of demand of the body for food, have supposed this lack of appetite to be Nature’s call “Enough”; inertia has resulted and waste remains in the body. They have failed to exercise sufficiently to create a demand for food. It is thus undernourished because sufficient new building material has not been supplied. The relief from this condition is exercise and deep breathing so that Nature removes the waste and calls for fresh building material.
Many others, through mental and physical activity, burn up much fuel and the result is the body does not store up sufficient fat for a reserve, or for beauty and comfort. The nerves require a certain amount of fat for their protection. People of this type should take a more full and sometimes a more varied diet, particularly more liquid, and should not fail in daily exercise and deep breathing.
Each individual should know, approximately, the chemical constituents and the proportion of these constituents in normal blood, because from the elements in the blood, the tissues are constructed. If certain elements are lacking, the foods containing these elements in largest proportions should be supplied until the blood no longer shows the deficiency. This is Nature’s method of correction. The variations in the blood can be known only by chemical analyses and until physicians have access to chemical laboratories the giving of drugs cannot be a science.
Each meal, or each day’s food, may not contain the amount of protein or of fuel ingredients necessary for that day’s work and resupply, but the body is continually storing material, and this reserve is constantly being drawn on to provide any element which may be lacking in that day’s supply. Thus, an excess or a deficiency one day may be adjusted the next. Healthful nourishment requires that the balance, as a whole, be kept and that a deficiency or oversupply be not continued for too long.
The distinct steps in anabolism and the effect of oxygen on assimilation are discussed in the following pages.
DIGESTION
Any discussion of the digestibility of foods must be general, because food which agrees with one may disagree with another, and a food which disagrees with one at a particular time may entirely agree with him at some other time according to the condition of his system. Therefore, before one passes on the adaptability of a food to his system, he should know that this food agrees or disagrees with him under various conditions.
The chances are that the food is right but that the attitude of mind and the condition of the body are abnormal.
The digestibility of food depends largely on the physical condition of the individual, because the amount of digestive juices poured into the alimentary canal is influenced by this condition, particularly by the condition of the nerves. If sufficient juices, in proper proportions, are not poured into the digestive tract, the foodstuffs are not made soluble for absorption.
Digestion is practically synonymous with solution—all solid foods must be reduced to a liquid state by means of the digestive juices and water before they can pass through the walls of the stomach and intestines and enter the blood.
Each individual should learn to like the foods containing the nutrient elements which experience and blood tests have shown to be lacking in his case.
Yet while it is true that in most cases the aversion to a particular food is largely mental, there are kinds of food which, to certain individuals, according to the chemical composition of the body, act as actual poisons, e. g., strawberries, cheese, or coffee.
The question of likes and of dislikes in foods, is largely habit, and one can learn to like almost any food, if one really has the desire to do so.
When the habit has been formed of discriminating too much in the food, of discarding this food or that, because at some time it has disagreed, due to the particular condition at the time, the mind approaches the table in a pessimistic attitude and the saliva and the gastric juices are retarded in their flow.
When one is exercising freely, so that the muscular and mucous coats of the digestive system are strong, the body will handle foods which, during sedentary habits, it would not digest.
Much indigestion is due to mental apathy. The mind often needs arousing to an interest in something.
Such an individual needs to know that one of the hardest things for the members of his family is to live day by day with one who maintains an attitude of mental depression, and he should stir himself for “his stomach’s sake,” as well as for the sake of his family, to a cheerful interest in something. He should let go his grudge and ride a hobby, if it is a cheerful one, and ride it hard.
It may be well, here, to trace, briefly, the progress of the food through the digestive tract and the action of the juices and the ferments on it.[5]
Salivary Digestion
The food in the mouth is mixed with saliva, which begins the dissolution of the starches.
The saliva consists of about 99.5 per cent. water and 0.5 per cent. solids. The solids consist of ptyalin, sodium chlorid, sodium carbonate, mucus, and epithelium. Ptyalin, the most important of these, is the active digestive agent; the mucus lubricates the masticated food; the sodium carbonate insures the alkalinity of the food, and the water dissolves the food that the juices may more readily reach and act on each particle.
The starches are the only foods whose chemical digestion is begun in the mouth. They are first broken up by the ptyalin into dextrin and then into the more simple sugar, known as maltose.[6]
It is important that sufficient saliva be mixed with the food through mastication, because unless the digestion of the starches is begun by the saliva, either in the mouth or after it is swallowed, they are not acted on until they reach the small intestine, consequently their digestion is unduly delayed. The pancreatic juice must then do more than its normal work of digestion.
The saliva flows into the mouth, more or less, at all times, but more copiously during mastication.
The movement of the jaws in chewing incites its flow and when starches are not well digested, gum chewing, in moderation, though not a refined habit, is beneficial.
The evident purpose of the saliva when food is not present is to keep the lining of the mouth moist.
Salivary digestion is carried on in the stomach until the food becomes thoroughly mixed with the gastric juice, which, being acid, inhibits the action of the ptyalin.
The thorough and regular cleansing of the teeth is an important aid to digestion. Food products allowed to remain about the teeth ferment, rendering the mouth acid. When the mouth is acid, the alkaline saliva does not secrete in sufficient amount and the mouth is more or less dry.
The mouth is acid in rheumatism and allied conditions and the saliva may be thick and ropy so that it does not moisten the food properly. On the other hand the flow of saliva may be too free, the ptyalin is then too much diluted to promptly act on the food. This may result from overstimulation of the salivary glands occasioned by the excessive chewing of gum, or tobacco. These excesses also carry too much air into the stomach, resulting in flatulence.
The flow of saliva is controlled, largely, by nerves centering in the medulla oblongata. The sight of food, pleasingly served, or even the thought of food which one likes, will increase the flow. This is one instance of the control of thought over digestion, and the importance of forming the habit of cultivating a taste for all kinds of food is apparent. The stronger the relish for the food, and the more thoroughly it is masticated and mixed with the saliva, the more perfectly will the first step in digestion be accomplished.
Thorough mastication is important, not only because the chemical action on the starch molecules is facilitated by the softening and mixing with the saliva, but also because thorough mastication tends to prevent overeating—the appetite is more quickly satisfied when the food is well masticated.
Cool water encourages the flow of saliva and for this reason should be drunk before meals, particularly when digestion is weak. It may be taken at rest periods during the meal. (See page [31].)
The Mouth and Nasal Passages
The relation of the mouth and nasal passages to the digestive processes is seldom considered by the average individual. Their importance to the growing child is being recognized by the examination of school children which is now being made a part of the health program in many of our cities. Their importance to the adult is no less.
Food particles allowed to remain around the teeth, or in the cavities of decayed teeth, incite bacterial action. With the next meal these bacteria are swallowed and cause fermentation of the food, occasioning indigestion, and possibly, dyspepsia.
Decayed or missing teeth, swollen gums, or pyorrhea, interfere with proper mastication of food, hence it does not receive the thorough salivary moistening necessary; the starches pass practically unchanged into the stomach and small intestine, overburdening these organs.
Catarrh of the nasal passages, with the constant swallowing of germ-filled secretions, carries morbid products into the stomach, coating the glands with mucus, often infecting them; it may also occasion a catarrhal condition of that organ.
If, from any cause, the saliva becomes acid, dryness of the mouth results and desire for food is lessened or absent. Diseases of the salivary glands may render these necessary secretions unfit to perform their work.
In illness the mouth often drops open from weakness, producing the same condition of dryness. The mouth, in illness, is too often neglected by those in charge of the invalid.
Adenoids and enlarged turbinates in child or adult, narrowing the nasal passages and preventing the ingress of air, cause mouth breathing. The air dries the membranes and the tongue becomes swollen and cracks, interfering with proper mastication.
Adenoids should be removed, and any other condition which interferes with the proper function of the mouth should be remedied as soon as possible.
The mouth should be properly cleansed, the gums massaged, the teeth thoroughly brushed, back as well as front, defective teeth repaired or removed, abnormal growths eliminated, and the secretions kept abundant and healthy. Food well prepared in the mouth by thorough mastication satisfies hunger, renders more easy the work of the stomach and intestines, and aids in the general welfare of the system.
Gum-chewing
This too prevalent habit may aggravate the condition which it is supposed to cure. A slight indigestion appearing, gum is often chewed to cause a fuller flow of saliva to aid digestion. If gum-chewing is indulged in to excess, however, the muscular movements overstimulate the salivary glands, eventually weakening them. Overuse of the chewing muscles and overexcitation of the nerves fatigue them and cause them to weaken. The sticky gum, adhering to fillings in the teeth, loosens them and furnishes a lodging place for food particles and bacteria.
The excess of saliva may render the gastric juice alkaline, inhibiting its action. Excess of air swallowed with the saliva may cause flatulence or accumulation of gas in the stomach.
Lack of poise and nerve tension is increased by excessive gum-chewing, resulting in fatigue of the entire body. This lack of poise may be noted in any public assembly, as the “movies,” frequented by gum-chewers.
The habit, as generally practiced, is not an inspiring sight and should be discouraged.
Gum-chewing in moderation, for a few minutes after a meal, may not do harm, but its indiscriminate use is to be deplored. Thorough mastication of food will serve to supply the necessary saliva.
Exercise directed to the stomach and a more thorough circulation and elimination will do more for any digestive derangement than the excessive practice of chewing gum.
Stomach Digestion
As the food enters the stomach, the gastric juice pours out from the mucous lining, very much as the saliva pours into the mouth. Like the saliva, it consists of 99.5 per cent. water and 0.5 per cent. solids. The solids of the gastric juice are pepsin, rennin, hydrochloric acid, and mucus.
The mucus serves to lubricate the food as in the saliva. It perhaps also aids to prevent the digestion of the mucous lining of the stomach.
The hydrochloric acid and the pepsin cause the principal chemical changes in the food while in the stomach. They act only on the proteins. The hydrochloric acid must be present before the pepsin can act, as only in an acid medium can pepsin dissolve the proteins. It is also of an antiseptic nature and hinders or prevents the decomposition of food.
The rennin ferment precipitates the casein.
The only digestion of starches in the stomach is that continued by the saliva.
Gastric juice begins to flow into the stomach soon after eating, but normally it is not secreted in sufficient quantity to supersede salivary digestion for from twenty to forty-five minutes.
The result of gastric digestion of proteins is their conversion, first, into albumin, then into proteoses, and, lastly, into peptone, which is protein in a more simple, soluble, and diffusible form. In the form of peptone, the proteins are in condition to be absorbed.
If the food has been properly cooked and masticated, gastric digestion will be completed in from one and one-half to three hours. If not properly cooked and masticated, the stomach digestion may continue from one to two hours longer. It should, however, be completed in three hours.
It will be seen that the evening meal is ordinarily digested before sleep, as one does not retire for from three to five hours after eating.
If, through imperfect mastication, or a disordered condition of the stomach, the digestion is not completed in about three hours, the food is likely to be retained in the stomach and by its weight may cause prolapsus of that organ if the supporting tissues are weak. Fermentation may ensue and give rise to gases which may cause acute distress.
Animal foods, which are readily digested, remain in the stomach for a shorter time. Meat, as a rule, is easily digested, because the digestive juices of the animal have converted the starches and sugars. The white meat of chicken is digested in a shorter time than the red or the dark meat.
Corn, beets, peas, beans, etc., take about three and a half hours to digest; baked potatoes about two and a half hours.
Raw vegetables and fruits remain about the same length of time as potatoes.
Sugar is usually absorbed within an hour.
The cereals, if well cooked, take but two hours.
Coarse or badly masticated food, tough meats, unripe fruits, and much fat hinder digestion.
Undigested food passing into the intestine may fail to be acted on there and will sometimes produce diarrhea.
Fluids leave the stomach more rapidly than solids. Seven ounces of water entirely leaves the stomach in one and one-half hours, seven ounces of boiled milk in about two hours. Water and buttermilk almost immediately begin to pass out of the stomach; milk begins to pass out in about fifteen minutes.
The flow of gastric juice, as the flow of saliva, is governed by the nerves; the sight, taste, and smell of food, and the attitude of mind toward it, to a certain extent, regulate its flow.
After the food has accumulated, during the progress of a meal, the stomach begins a series of wave-like movements called peristaltic waves.[7] These waves propel the food through the length of the stomach towards its lower opening, known as the pyloric orifice. During this process the food is thoroughly mixed with the gastric juice.
During the early stages of digestion of solids, the sphincter muscles of the pylorus keep the lower opening of the stomach closed, but, as digestion progresses, the pylorus gradually relaxes to let the digested, soluble portion of the food pass into the intestine. If the food still remains in a solid form, by reason of being improperly cooked or poorly masticated, as it touches the pylorus, these sphincter muscles, almost as if they were endowed with reasoning faculties, close, forcing the undigested mass back to be further acted on by the gastric juice—the solid mass is not allowed to pass until dissolved.
If the individual abuses the stomach and causes it to work overtime, it becomes exhausted and demands rest; it refuses to discharge the gastric juice in proper proportion; the peristaltic movements are weak; and food is not promptly or forcefully moved along the stomach and mixed with the gastric juice. This condition is termed indigestion.
Intestinal Digestion
The food passes from the stomach, through the pylorus into the small intestine. In this condition of partial digestion it is called chyme.
The first twelve inches of the small intestine is known as the duodenum. In the duodenum the food is acted on by the pancreatic juice, the bile, and the intestinal juices. These juices act on proteins, fats, and carbohydrates. The bile acts on the fats, while the pancreatic and intestinal juices act on the proteins and the carbohydrates. The starches, or dextrin, not fully digested by the saliva, are changed to maltose and glucose, while the trypsin from the pancreatic juice, together with the intestinal juices, change into peptone the protein not fully digested in the stomach. The pancreatic juice also digests the starch found in raw fruits and in such raw vegetables as radishes and lettuce.
Fats are almost entirely digested in the small intestine. The presence of fat stimulates the flow of pancreatic juice, which, in turn, stimulates the flow of bile. For this reason, in some conditions, if the liver is sluggish, fatty foods in moderation are desirable. When bile is not present in sufficient amount the fatty foods ferment and cause gases and foul odors.
The fats are absorbed almost entirely in the small intestine—mostly in the duodenum. Some of the fat may be absorbed directly without undergoing the process of emulsification. Some oils, as paraffin oil, are not absorbed at all but act only as a lubricant of the intestines.
When the food enters the intestine its reaction is acid. Mixed with the bile, pancreatic and intestinal juices, which are alkaline, its reaction becomes alkaline.
The pancreatic juice splits up the fats into glycerin and fatty acids and enables the bile to exert its important emulsifying power. The bile markedly aids this action of the pancreatic juice though it has no fat-splitting power in itself.
Steapsin, another ferment of the pancreatic juice, acts on both fats and carbohydrates in either an acid or alkaline medium.
The sodium in the bile unites with the fatty acid, forming a soap which coats the tiny particles of fat and emulsifies them. The bile thus aids in the absorption of the fats. It also lubricates the intestinal mass, facilitating its passage through the entire length of the intestines. Thus it is a very potent agent in regulating the bowel movements.
A diminution in the flow of bile quickly expresses itself in constipation.
Fat and protein stimulate the activity of the liver, while starches, if taken in excess, incline to overload it.
The food is forced along the intestinal tract by peristaltic or muscular relaxation and contraction waves, as in the stomach. As it is so forced, the nutrient elements, after being put into condition for absorption, are taken up through the villi of the intestinal walls by the portal veins and the lacteals of the submucous lining.
A larger proportion of food is digested and absorbed than was formerly supposed, and the excretions from the intestines are, in many cases, made up almost entirely of refuse, and of the catabolic waste of the system. In an ordinary mixed diet, it is stated that about ninety-two per cent. of the proteins, ninety-five per cent. of the fats, and ninety-seven per cent. of the carbohydrates are retained by the body.
In digestion, it is of the utmost importance that the muscular, mucous, and submucous coats, and the secreting glands of the stomach and intestines be kept thoroughly strong and active, that the digestive juices may be freely poured out, the nutriment be freely absorbed, and the food be moved along the digestive tract. The strength of any organ is gained through the nutriment in the blood; therefore, daily exercise, which calls the blood freely to these organs is imperative. Daily exercise should be directed to the vital organs. A walk for exercise is not sufficient.
Absorption of Food
The greater part of the food is absorbed through the intestines, yet some proteins which have been fully digested by the gastric juice, and certain fats, particularly the fats in milk, which are in a natural state of emulsion, may be absorbed through the walls of the stomach. However, the absorption through the stomach is small compared to that through the small intestine.
Diagrammatic Representation of Villus.
a, 1, cylindrical or “sucking” cells; 2, goblet cell; 3, capillaries; 4, food particles ready for absorption by the cells; b, cylindrical and goblet cells seen from above.—Adapted from Landois.
The small intestine is peculiarly fitted for absorption. Its mucous lining is thrown up into folds to furnish a larger surface for this purpose. The folds hold the food as it passes toward the large intestine, until the villi have the opportunity to absorb it.
These transverse folds of the intestinal walls are called valvulæ conniventes.
The villi are tiny finger-like projections of the mucous lining of the intestines, which stand out of the lining somewhat as the nap on plush. They have been called “sucking” villi, because during the movements of the intestines they seem to suck in the liquid food.
As soon as the foodstuffs—proteins, carbohydrates, and fats—are put in an absorbable state called chyle, they are very promptly taken up by the villi.
If for any reason the chyle remains unabsorbed, it is liable to be attacked by the bacteria always present in the intestines, and gases form.
The peptones, sugars, and saponified fats are rapidly absorbed, while the undigested portion, together with the unabsorbed water, the bile, mucus, and bacterial products, are passed through the ileocecal valve into the large intestine.
The mass passes up the ascending colon, on the right side of the abdomen, across the transverse, and down the descending colon, on the left side, losing, by absorption, the small amount of foodstuffs not absorbed in the stomach and small intestine. That the large intestine is to some extent adapted to absorption is shown by clinical experiments with patients who cannot retain food in the stomach, the food in such cases being given through rectal injections.
While water and salt are absorbed in both the stomach and small intestine, the larger part of the water passes into the large intestine, that it may assist the passage of the intestinal contents.
Water also stimulates peristaltic movements.
As the food is absorbed through the walls of the alimentary canal, it is picked up by the rootlets of the mesenteric veins and by the lymph channels—the latter through the abdominal cavity are called lacteals. Nearly all of the fats are absorbed through the lacteals. The whitish color given to the contents of the lacteals, by the saponified fats, gives rise to the term “lacteal.”
Nearly all of the proteins and sugars pass through the mesenteric veins and the portal veins to the liver. Here the sugars are at once attacked by the liver cells and built up into glycogen as described on pages 151 and 159. A small portion of the proteins, however, do not go to the liver, but are passed directly into the lymphatics and thus into the blood stream, where they are again carried to the liver, and the urea is separated.
To sum up, the larger part of the sugars, starches, proteins, and fats is absorbed through the small intestine, a small amount being absorbed in the stomach and a very little through the large intestine. While some water and salts are absorbed in the stomach and small intestine, these are largely absorbed in the large intestine.
Economy in Food
It is economy to keep the digestive organs and the circulation and tissues strong, in order that all foods eaten may yield returns, instead of hampering the activity of the body.
The food which furnishes the most tissue-building substance and yields the most heat and energy, with the least refuse, is the economical food, provided it is varied enough to meet the psychical needs as well as the physical.
Whether or not a food is economical depends on the degree to which it stimulates the activity of the mind as well as the body. Preparation and serving here are as important as the material to be served.
Economy in food is a question into which many factors should enter. A cheap food is not always an economical food. Amount and keeping qualities, palatability, ripeness or unripeness, the age, habit, and occupation of the partakers, all have their share in the problem.
In the selection of food for any individual, the result to be gained from the food must be borne in mind. If one is doing heavy muscular work, more protein to rebuild tissue, as well as more carbohydrates and fats to produce energy, are required than if one’s habits of work are sedentary.
In mental work, in which the brain is continually active, proteins are required to resupply the brain tissue, but the fats and carbohydrates may be lessened. If the brain is sufficiently active to use all of the fuel in brain energy one does not accumulate fat.
In sedentary occupations, which do not call for hard and continuous mental activity, the carbohydrates and fats, if taken in excess, are stored within the system, clogging it and producing torpid liver, constipation, and obesity.
In a study of tables of food values, in making up a dietary, the question should be to provide the largest quantity of nutriment at the lowest cost, with due attention to palatability and variety.
In the selection of meats, for instance, while beef steak may cost twice as much as beef stew, it must be borne in mind that beefsteak contains very little waste, and that it contains a large proportion of albuminoids, or the tissue-building proteins, while, in beef stew, bone and connective tissue predominate. A large proportion of the proteins obtained from the beef stew are gelatinoids and extractives—not the tissue-building albuminoids. (See page [56].)
In comparing the cheaper and the more expensive cuts in the same kind of beefsteak, however, the cheaper cuts often yield quite as much nutriment as the more expensive ones. Round steak is just as nourishing as porterhouse and cheaper, if one considers the greater number of helpings derived from a pound of round steak than from a pound of porterhouse.
For the aged or the invalid, however, the question of preparation will determine the relative economy.