FOODS
Nutrition and Digestion

KNOW THYSELF SERIES

Second Edition

The author, in giving remedial exercises and diet prescribed to suit the individual need, has for ten years realized the necessity of a book which shall give to the homemaker a clear idea of the uses of foods, that she may be able to compile her own diets for various blood conditions. Since the blood is made from food elements, its conditions can be largely controlled by a knowledge and regulation of these elements.

Acknowledgment is here made of the valuable assistance of Winfield S. Hall, Ph. D., M. D., Professor of Physiology of Northwestern Medical School, Lecturer and Author of Nutrition and Dietetics; of Alida Frances Pattee, late instructor of Dietetics Bellevue Training School for Nurses, Bellevue Hospital, New York City, author of “Practical Dietetics with reference to Diet in Disease,” and of D. Appleton & Co., for their kindness in allowing the use of Dr. Hall’s tables of food values, in the preparation of this book.

The tables of Food Values and the classifications of foods are kindly furnished by Dr. Hall and used by the courtesy of his publishers, while a few of the receipts are generously furnished by Miss Pattee.

Recognition is also made of the good work of Miss Helen Hammel, former dietitian in Wesley Hospital, Chicago, in the preparation of some of the receipts in the Appendix.

FOODS
Nutrition and Digestion

BY
Susanna Cocroft
AUTHOR OF
Growth in Silence
Self Sufficiency
The Vital Organs
Habits: The Nerves
Poise and Symmetry of Figure
Character as Expressed in the Body
Ideals and Privileges of Woman
Etc., Etc.
ORIGINATOR OF THE
Physical Culture Extension Society

First Edition 1906
Second Edition 1912
Published by the
Physical Culture Extension Society
624 S. Michigan Ave., Chicago, Ill.

Copyright, 1906-1912
by Susanna Cocroft

FOODS
Nutrition and Digestion

BY
Susanna Cocroft

The problem of proper nutrition for the body is as vital as any study affecting the morals, health, and consequent power of a nation, since upon the quality and quantity of food assimilated, depend the sustenance, health, and strength of its citizens.

The study of life is the most vital interest in nature. The human race spends more time in providing nourishment for the body than in any other line of activity. Next to nourishment comes self-preservation. It is intuitive, the infant’s first instinct is the preservation of life; almost at once he seeks for nourishment. His body is ever an awakening wonder to him. He begins his education by a study of his hands, his legs, and his flesh.

“The physical satisfactions of life, the joys of mental development, the inspiration of soul, the sense of growth, of expansion, and of largest happiness, the self-satisfaction of greatest usefulness, and the glorifying results of this usefulness, come in largest measure only to the person whose nutriment is proper in quantity, quality, and form and is taken properly, as to time, mastication, swallowing, and digestion, with sufficient exercise to give the body activity to convert it into use. This enjoyment of vibrant life is far beyond the joys of the intemperate or the æsthetic.” That ones energies of thought may not be constantly engaged in deciding what is best, it is important that proper habits be formed. Habit calls for no conscious energy.

Scientific research along the lines of electricity, psychology, metaphysics, medicine, and art has been tenaciously pursued for centuries; yet scientific study of the natural means of keeping the body in health, that the individual may be in physical, mental, and moral condition to enjoy and to profit by researches made in other lines, has been neglected. The result is, that man does not enjoy life to the full, nor make his physical nor mental efforts yield the best returns.

It is necessary to know the comparative values of foods as nutrient agents, in order to maintain our bodies in health and strength, and with economy of digestive effort, as well as efficiency. The entire body,—bone, muscle, blood, brain, nerve, heat and energy,—is formed from the food and drink taken into the stomach and from the oxygen breathed into the lungs; the mental and physical activity also depends upon the food. There is no study, therefore, more important than that of bodily nutrition and the preparation of food and drink in right proportions to yield the best returns under varying conditions,—age, employment, health, and sickness.

Nutrition is a broad subject. It means not only that the foods be supplied which contain elements required to rebuild body substance and to create heat and energy, but it embraces, also, the ability of the body to appropriate the foods to its needs. The study of nutrition in its full sense, therefore, must embrace foods, anatomy and physiology (particularly of the digestive system), and chemistry, in order to know the changes foods must undergo in being converted into tissue, heat and energy[1]. This study, reduced to a science, is known as Dietetics. There is no more important study for public schools, or for woman’s clubs.

Nutrition must be solved largely through chemistry. The health and efficiency of the individual and of the Nation depend upon careful study of the chemical components of foods and the control of the foods placed upon the market. The “pound of cure” in the study of materia medica has been given much thought,—the “ounce of prevention,” little.

The former custom of employing a physician as a retainer had its distinct advantage, his duty being to instruct in right living so as to avoid disease rather than to cure it. To-day scientific instruction in food and hygiene is within the reach of all, and every mother and teacher is a retainer, or guard of the health of those in her charge.

Happily, the United States Government, realizing that its power as a nation depends upon the strength and health of its citizens, has established experimental and analytical food departments. As a result of the findings of the governmental chemists, there was enacted in 1906, the Food and Drug Act, which aims to raise the standard of food purity, by prescribing the conditions under which foods may be manufactured and sold. The law compels the maker of artificially colored or preserved food products to correctly label his goods. The national law was the instigation of state laws, which have further helped to insure a supply of pure food products.

Every particle of body substance is constantly changing. The new material for cells and tissues, the substance to supply the energy needed in the metabolic work of tearing down and rebuilding, the energy used in the digestive process of converting the food into condition to be assimilated, and the energy used in muscular, brain, and nerve movement, must all be supplied by food. Every brain effort in the process of thinking, every motion, and every muscular movement requires energy which the food must supply.

Brain workers, or habitual worriers, use up force and become thin quite as quickly as those whose work is muscular. The term “brain workers” is commonly applied to professional men or women,—to authors, editors, teachers, or to those engaged in business, but the woman who manages her household judiciously, or the woman who spends her life fretting over existing conditions, or worrying over things which never happen, uses quite as much brain force. The difference is that the former accomplish results outside of themselves, while the latter simply stirs up disagreeable conditions within, resulting in physical ills.

The whole problem of perfect health and efficient activity is in keeping the supply assimilated food equal to the demand, in keeping a forceful circulation that the nourishment may freely reach all tissues and the waste be eliminated, and in full breathing habits that sufficient oxygen be supplied to put the waste in condition for elimination.

The body is certainly a marvelous machine! It is self-building, self-repairing, and, to a degree, self-regulating.

It appropriates to its use foodstuffs for growth and for repair.

It eliminates its waste.

It supplies the energy for rebuilding, and eliminating this waste.

It directs its own emotions.

It supplies the energy for these emotions.

It discriminates in the selection of food and casts out refuse and food not needed.

It forms brain cells and creates mental force with which to control the organism.

It keeps in repair the nerves, which are the telegraph wires connecting the brain with all parts of the body.

It converts the potential energy in the food into heat with which to keep itself warm.

Withal it is not left free to do its work automatically. It has within it a higher intelligence, a spiritual force, which may definitely hamper its workings by getting a wrong control of the telegraph wires, thus interfering with the digestion, the heart action, the lungs and all metabolic changes. The right exercise of this higher intelligence, in turn, depends upon the condition of the body, because when the mechanism of the body is out of repair it hampers mental and spiritual control. Surely man is marvelously made!

The intelligent care of the body,—the temple through which the soul communicates with material conditions,—is a Christian duty. “The priest with liver trouble and the parishioner with indigestion, do not evidence that skilled Christian living so essential to the higher life.”

Certain it is that improper foods affect the disposition, retard the spiritual growth and change the drift of one’s life and of the lives about one.

Man has become so engrossed and hedged about with the complex demands of social, civic, and domestic life, all of which call for undue energy and annoyance and lead him into careless or extravagant habits of eating and living, that he forgets to apply the intelligence which he puts into his business to the care of the machine which does the work. Yet the simple laws of nature in the care of the body, are plainer and easier to follow than the complex habits which he forms. The “simple life” embraces the habits of eating as well as the habits of doing and of thinking.

FOOTNOTES:

[1] It is impossible in this book to go into the anatomy and physiology of digestion exhaustively.—The reader is respectfully referred to Miss Cocroft’s book upon “The Vital Organs: their Use and Abuse.” This traces the food through the digestive canal, indicating the juices which act upon it, putting it into a necessary state to be absorbed by the body and appropriated to its various uses.

PURPOSES OF FOOD

The purposes of food are:

To supply the material of which the body is made.

To rebuild tissue, which is constantly being torn down and eliminated.

To produce heat, and to supply muscular and mental energy.

Let us discuss these purposes in above order.

Food Supply

By food supply is meant not only that the proper foods in kind and quantity be eaten, but that the body be in condition to digest, absorb, and assimilate the foods, and to eliminate the waste, otherwise the foods fail to supply the body needs. It is the nourishment which the body assimilates and appropriates to its needs which counts in food economy.

Of the fifteen to twenty substances contained in foods and comprising the body, the most abundant are oxygen, hydrogen, carbon, nitrogen, chlorin, sodium, potassium, magnesium, iron, calcium, phosphorus, and sulphur. All living matter, plant or animal, contains oxygen, hydrogen, carbon and nitrogen; the difference in the form and use of the matter is in the proportions of these elements.

Carbon combined with oxygen forms carbon dioxid. Hydrogen, nitrogen, and carbon dioxid form the air. Oxygen and hydrogen form water. Calcium, iron, magnesium, sodium, and potassium form the majority of rocks.

The substances contained in living organisms are the same as those in inorganic matter, only in different complexities as appropriated to each need. This difference in complexity of combinations of the same elements in a body is the physical difference between a living and a non-living plant or animal.

By far the most important change which the food must undergo to convert it from raw material into a state for conversion into body needs is the chemical change. While the body needs carbon, it cannot use coal; it needs nitrogen, yet it cannot appropriate it to rebuilding bone and muscle until, by chemical action with other elements within, it has been converted into complex substances called proteins; again, the chemical action of oxygen breaks down the proteins.

The muscles, ligaments, and labor-performing structures contain the largest amount of proteins; the fats and the carbohydrates contain the largest amount of carbonaceous compounds; the brain, the nerves, and the bones contain the largest portion of phosphorous compounds; yet, while the brain contains phosphorus, and the muscles nitrogen, the brain cannot be built up by eating elementary phosphorus, nor the muscles by pure nitrogen, but compounds rich in phosphorus or nitrogen may be utilized. It has been demonstrated by scientific investigation that no unorganized element is assimilated by the system and converted into its various structures.

The gluten of wheat is built up by the chemical union of nitrogen in the air and nitrogen in the soil with other substances. Plants are able to use the simple compounds of the earth, air, and soil, and, within their own cells, build them up into such complex substances as starch, sugar, protein, fat, and salt, which are appropriated by the animal kingdom for further growth and change.

In its conversion into tissue, heat, energy, and waste, the importance of the chemical exceeds the mechanical action, such as digestion, absorption, assimilation, and elimination; yet the chemical changes are aided by the mechanical.

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 be 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.

Each meal, or each day’s food, may not contain just the amounts of protein or of fuel ingredients necessary for that day’s work and re-supply, but the body is continually storing material, and this reserve is constantly being drawn upon 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 over-supply be not continued for too long.

Many domestic animals take their food elements from air and water, as well as from the compounds which the plants have formed; while others make use of meat, a compound formed by another animal. The digestive forces of the animal has converted these elements into flesh, a compound easily assimilated by another.

The greater part of the muscles, nerves, and glands of the animal kingdom is protein. The skeleton is composed largely of deposited salts, while the elements which supply heat and keep up muscular activity are starches, fats, and sugars.

The proteins are appropriated by man from plants, but they are furnished to him in more easily digested form in lean meat and eggs, the lower animals having done much of the work of digestion, converting the proteins from plant life into more condensed form. On the other hand, by access to this concentrated form of easily digested protein, man is in danger of taking in too much of this condensed food, if he eats a large quantity of meat and eggs.

It must be apparent to every thoughtful person, since the nerves, muscles, and glands are composed largely of protein and the skeleton largely of salt, that, in order to furnish the body with the elements necessary for growth and repair, these elements must be provided, as also the substances producing the energy for the working body. Each individual should make a self-study to know how much re-supply is required to renew the daily waste.

About one-third of the food eaten goes to maintain the life of the body in doing its incessant work of repairing and rebuilding, the remaining two-thirds is the reserve for usefulness outside of itself.

One of the most remarkable, and the least understood of any of the assimilative and absorptive functions, is that any one part of the body has the power to appropriate from the foods the elements necessary for its own rebuilding, while these same elements pass through other organs untouched. The body has the power, also, to not only make use of the foods, but to use up the blood tissue itself. Just how this is done is also a mystery.

There is surely a great lesson in industry here, and one of the most profound studies in economics, physics, and chemistry.

Heat and Energy

The second use of foods, as mentioned before, is to create heat and energy for the work of the body. This includes the action of the heart; the movement of the lungs in breathing; the digestion, absorption, and assimilation of food elements; the tearing down and elimination of waste; and the muscular activity of body movements.

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 the engine consists of coal, wood, or oil. As these are rapidly 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 exactly equals 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, not liberated, going off in the smoke, while some may remain in the cinders.

Just so in the body,—the amount of heat and energy given off from the body exactly equals the amount of latent energy released by material burned during oxidation. It is estimated that about one-sixth of the heat liberated evaporates through the skin, the lungs, and through 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 cooked, some of the food is not made perfectly soluble for absorption. 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 in food.

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.

As mentioned before, the fuel for the body consists of fats, starches, and sugar, which, in combination with oxygen, create force. The combination of oxygen with other elements in the body is known as oxidation. This oxidation liberates heat and at the same instant produces energy, either in muscle, gland or nerve. The muscular energy expresses itself in muscular motion, the glandular in chemical action, and the nervous in nervous energy. The nervous energy is closely allied to electrical force.

The starches come largely from cereals and root vegetables; the sugars largely from cane, from certain trees, and from vegetables, fruit, and milk; the fats come from vegetable oils, from animal fat, as fat, and some from milk and butter. Some fats are also formed from proteins.

From the above, it follows that the fuel value of food depends upon the amount of fats, starches, and sugars contained.

The exact process of the conversion of the potential energy latent in food into heat and energy is not known. It is partly released during the digestive process, as the elements of the food come into contact with the oxygen swallowed and with the digestive juices. This combustion gives to the digestive organs the necessary warmth for their effective work. Digestive juices will not flow freely when the body is cold. The heat liberated during the digestive process is necessary, also, to put the elements of the food into condition for absorption, a certain amount of heat being required for the chemical changes. This liberated energy is expressed, not alone in the chemical formation of the compounds, but in the peristaltic movements of the digestive organs.

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. 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. So many people cover up the body with more clothing to reserve the body heat and forget to generate more heat by arousing the fires within. This is like covering up a dying fire to reserve the heat, instead of turning on the draught to create more combustion.

Nature provides for a reserve of heat and energy, above the immediate needs, by storing up a supply which is called into use whenever the daily supply is inadequate. Many hibernating animals store up sufficient fat in summer to provide heat for the entire winter. This fat would not last the winter, however, were the animal active. Many individuals store up excess of fat sufficient to last them for months, even though all fat building elements be omitted from the diet.

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 of heat liberated. During exercise, a large amount of fat, protein, and dextrose (sugar) are released by the movements and oxidized; the liberated heat is carried to all parts of the system and the temperature is raised. Mental work, for the same reason, tends to raise the body temperature, though to a much less degree. Food in the alimentary canal causes an activity in the glands of the digestive organs and also increases the temperature.

Of course, while digestion and mental and muscular activity are at their height, the body temperature is highest. These activities usually reach a maximum in the afternoon and the temperature is then highest, while, as a rule, it decreases from about six at night until four or five in the morning, when it is usually at its lowest ebb. This is a point of importance to physicians. Even five degrees above the average human temperature, if recorded about six at night, is not considered abnormal.

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.

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. 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 with a tepid shower or a tepid sponge. The tepid water is not so extreme as to create a strong reaction and it will cause a marked decrease in temperature. Thus, for fever patients or for 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 is desirable. Where the vitality is low, so that there is not sufficient reaction, the bath must be tempered.

Heat generation is also increased by solid foods that require more than normal activity on the part of the glands for digestion. For this reason the food for fever patients should be that most easily digested and should be reduced to the minimum to keep up the strength.

Diuretic foods and beverages, which increase the activity of the skin and the kidneys, also tend to lower the body temperature.

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.

The young child’s blood circulates freely, his breathing is unrestricted, the waste of the system is fully burned up, potential energy is released, and the result is, he must be active. The effort of the teacher, or of those having the care of children should be, not to restrain the child, but rather to direct his activity in advantageous and effective use of his energy.

Scientists have a means of measuring 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 to four degrees Fahrenheit, or will lift one ton one and fifty-four hundredths.

Truly the body is a busy work-shop. Think of the billions upon 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, it 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 required.

If strong mental work is required, attention should be given to exercise and deep breathing the while, 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 re-supply the oxygen required to carry on his work and to carry away the waste liberated by brain energy. The supply for the body work has been called upon for the undue brain work, and this lack of oxygen has produced a state of body designated as “tired.” Until the necessary oxygen has been supplied, the brain and body are not balanced, not “rested.”

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 it is the effort of every man and woman 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.

Repair and Elimination of Waste (Metabolism)

Every part of the body is constantly changing. Its work never stops. If kept in thorough repair it must be torn down and rebuilt incessantly. 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 catabolism. While the process of oxidation in catabolism is going on, heat and energy are set free. Most of the chemical changes in the body are catabolic in character. This work of tearing down and rebuilding body tissues 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; nearly every one eats more than necessary for the body needs.

By assimilation is meant the digestive 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.

Nature provides for an incomplete knowledge of the amount of re-supply necessary, by enabling the system to carry off a limited amount of surplus food above the bodily requirements.

The distinct steps in anabolism are discussed in the following chapter describing the work of different organs and the chemical changes of foods as they come in contact with the elements in the digestive juices.

CLASSIFICATION
OF FOOD ELEMENTS

By foodstuff is meant the chemical elements, appropriated by the animal for the use of the body, as described above. By foods is meant those articles of diet found in the market which contain the chemical elements used by the body in various combinations. Bread, for example, contains all of the foodstuffs and has been called the staff of life, because it sustains life. Foods may contain elements, not foodstuffs, and not used by the body, but cast out as waste, while certain foods, such as sugar, cornstarch, olive oil, and egg albumen, contain only one foodstuff, as will be noted in the following classification of foods and foodstuffs—grouped according to the body uses.

There are many classifications but the following tables, as compiled by a leading dietitian[2] for his practical work in classes, are clear and concise.

The above classifications are made because of the preponderance of certain elements in them, not because they do not contain other substances; e.g. vegetables are mixtures of sugars and starches; fruits are mixtures of sugars, vegetable acids, and salts; milk, legumes, cereals, and nuts contain a more equal division of sugars, fats and proteins and are therefore represented as carbo-nitrogenous; lean meats, with the exception of shell fish, contain no starch, but all meats contain fat, protein, and water, and all, except liver, contain ash.

In the table below, examples are given of foodstuffs in which the chemical elements are almost pure representatives of their classes. Cornstarch, sago, and tapioca are almost pure starch, containing very little of any other element; glucose, cane sugar, syrups, and honey are almost pure sugar; butter, lard, and olive oil are nearly all pure fat; egg albumen, gluten, and lean meat are almost pure protein.

The proteins contain nitrogen, sulphur, and phosphates. The predominance of nitrogen has given the proteins the name nitrogenous. The carbonaceous foods contain none of these elements, but are rich in carbon, hence the name carbonaceous.

As previously stated, no food contains but one element of foodstuffs and all elements are formed into compounds of plant life from the elements in the soil, air and water by the action of the sun’s rays. The rays of heat and light seem to store something of their power in latent heat and energy within the combinations of these compounds. The end of plant life is the completion of its compounds,—it first generates the compounds, then matures them, and then dies.

All organic matter is thus formed by the action of the sun’s rays upon inorganic matter. All meats are first in the form of plant life and are converted into other compounds by the chemical processes of the animal. This chemical action of the animal converts the energy latent in the foods into more concentrated form. The animal thus performs a part of the chemical work for man.

The classification of foods, as previously stated, is based upon the principal organic foodstuffs contained. Proteins contain carbon and salts, and carbonaceous foods contain salts and nitrogen, but these are not in appreciable quantity. The preponderance of these elements determines the use of the foodstuffs in the body. It will be remembered that the chief uses are the production of heat and energy, the building of new tissue of the growing child, and the repair of the waste in the child and the adult.

Water

No one element of food is more important for the needs of the body than water. It comprises about two-thirds of the body weight and is a component part of all foods. It is composed of oxygen and hydrogen.

In order that the body may do efficient work in digestion and in the distribution of the nutrient elements of the foods, and that the evaporations from the body may be re-supplied, the water in the foods, together with the beverages drunk, should consist of about seventy-five per cent liquid to twenty-five per cent nutrient elements, or about three times as much in weight as proteins, fats, and carbohydrates combined. If undue evaporation or perspiration is occasioned, a larger proportion is required.

Water passes directly into the circulation without chemical change. It is being constantly evaporated through the lungs and the skin, and every forty-five seconds it passes from the kidneys into the bladder.

The average individual at normal exercise, requires about seventy-one and one-half ounces of water daily, which equals about nine glasses (one glass of water weighs one-half pound); a part of this is consumed in the food. By reference to the following tables it will be noted that water forms a large percentage of all food, particularly of green vegetables and fruits.

The importance of water for children must not be overlooked. It is the heat regulator of the body, and the more energy used, either in work or in play, which results in more heat and evaporation, the more water is required. An animal, if warm, immediately seeks water.

The body will subsist for weeks upon the food stored about its tissues; it will even consume the tissues themselves, but it would burn itself up without water, and the thirst after a few days without water almost drives one insane. It should be furnished freely, in small quantities at a time, to fever patients.

Few people, give much thought to its re-supply; yet they suffer from the loss of it, in imperfect digestion and assimilation, and with kidney and intestinal difficulties, ignorant of the cause.

Water softens and dissolves the food and aids in its absorption; it is one chief agent in increasing the peristaltic action of both the stomach and intestines, thus aiding in mixing the food with the digestive juices and aiding the movement along the alimentary canal; it increases the flow of saliva and of digestive juices and aids these juices in reaching every particle of food more promptly; it aids in the distribution of food materials throughout the body, carrying them in the blood and the lymph from the digestive organs to the tissues, where they are assimilated; it forms a large part of blood and lymph.

The theory has long been held that water drinking at meals is injurious, the objection being that the food is not so thoroughly masticated if washed down with water, and that it dilutes the digestive juices. But this theory is not so strongly held as formerly—in fact, it is now rightly disputed by the best authorities.

When water drinking at meals is allowed to interfere with mastication and is used to wash down the food, the objection is well taken, but one rarely drinks while food is in the mouth, the water being taken at rest periods between mouthfuls. Thorough mastication and a consequent free mixing of the food with saliva is one of the most essential steps in digestion, and the flow of gastric juice, as the flow of saliva, is stimulated by the water.

If, on the other hand, the food is not thoroughly masticated, water is most essential to furnish that which the saliva would otherwise supply to soak up and dissolve the food, in order that the gastric juice may more readily reach all parts of it.

It is singular that the use of water at meals has long been considered unwise when the free use of milk, which is about seven-eighths water has been recommended.

The copious drinking of cool water from a half hour to an hour before a meal will cleanse the stomach and incite the flow of saliva and gastric juice. Moreover, the digestive cells secrete their juices more freely and the sucking villi absorb more readily when the stomach and intestines are moderately full, either of food or water, and to fill the stomach with food requires too much digestion. The water passes through the stomach before the food.

In building up about seven thousand thin women, results show that the free drinking of liquid at meals has a tendency to put on flesh. Probably one reason for this is because of the cleanliness and greater freedom given to the absorbing and secreting cells of the mucous lining of the digestive tract, as well as to the stronger peristalsis.

It will be noted that water drinking at meals has many more arguments in its favor than against it.

One important use to which water is put is to cleanse the digestive tract and the kidneys. This cleansing within is more necessary than the cleansing of the surface of the body. One cannot form a better habit than that of drinking two to three glasses of water upon first arising and then working the stomach and intestines by a series of exercises which alternately relax and contract their walls, causing a thorough cleansing of these organs.

In case of gastritis, or a catarrhal condition of the stomach, often a pint of slimy mucus will collect in the stomach over night and the cleansing of the mucous lining of the digestive tract is then most important.

The drinking of warm (not too hot) or cold water in the morning depends upon the condition of the individual. If in good condition, two to three glasses of cold water, the vigorous exercises for the vital organs, and deep breathing of pure air, followed by a cold bath, will do more to keep the health, vigor, clear skin, and sparkling eye than fortunes spent upon seeking new climates, mineral waters, or tonics. There is no tonic like water, exercise, and fresh air, as above prescribed.

Soft water, that is water containing no lime or other mineral matter, is best for cooking purposes; hard water, which causes any degree of curdling of soap, or a lime crust in the bottom of a tea kettle, is hard on digestion. Bacterial germs are killed and much of the mineral matter deposited by boiling the water. For drinking purposes it should be aerated that it may regain its original, fresh taste, otherwise boiled water tastes flat or insipid. It may be aerated by filling a jar half full of water, leaving the other half for air, and then shaking the water in the jar so that the air passes through it.

Many claim that one’s thirst, as in the desire for food, is the only safe guide, as to the amount and time of drinking, but these desires are largely matters of habit, and tastes are often perverted. Unless the condition is abnormal or the mind becomes so intensely active that one fails to listen to the call of nature, the system calls for what it has been in the habit of receiving and at the stated times it has been in the habit of receiving it. The safe method is to form the habit of eating and drinking a stipulated amount at regular periods and not allowing this regular habit to be broken, unless, for some cause, the system be out of order, and then the habit should only be broken for a time.

Salt

Milk furnishes salt in proper proportion for the baby, and later, when the child is through nursing, eggs should be added to the diet of cow’s milk. It is especially essential that growing children be furnished milk and eggs that they may be assured of the proper proportion and quantity of calcium salts, as these form the substances of bones and teeth, which constitute about one-sixth of the body weight.

All vegetables, fruits, cereals, legumes, and nuts furnish both calcium salts and sodium, potassium, and magnesium, which are the salts used in the blood and lymph. Minerals are abundant in dried legumes, (beans and peas). A diet consisting largely of vegetables needs the addition of sodium chlorid (common table salt) to supply sufficient salts for foods; likewise more salt than is contained in grass and fodder is needed for animals, particularly for those producing milk. The scientific farmer salts his cattle regularly, while wild animals travel miles and form beaten paths to springs containing salt.

In rectal feeding, it is known that food absorbs more readily through the large intestine if salted. It is probable that salt, in normal proportions, also aids absorption in the stomach and small intestine.

Salt should not, however, be used immoderately.

The minerals of the food, or of the body, form the ashes in burning.

Iron

Iron is an inorganic substance and is necessary in making red blood corpuscles.

If, by some disturbance in the digestion, absorption, or assimilation of food, more iron is excreted from the body than is made use of from the food, the blood making organs do not receive sufficient iron and the blood is lacking in red corpuscles. It becomes poor in hemoglobin and the individual becomes pale. This condition is known as Anaemia.

Where there are not sufficient red blood corpuscles, it is of vital importance that one keep up a good circulation; the stomach, intestines, liver, and spleen must be strengthened through exercise and one must breathe deeply of pure air, for the red blood corpuscles are oxygen carriers, and the insufficient supply must do double duty or the waste of the system will not be oxidized and eliminated.

A diet rich in iron must be supplied. It will most often be found that one whose blood is lacking in hemoglobin and in the proper proportion of red blood corpuscles, has had a dislike for the foods rich in iron, or, perhaps, has not been able to get the right kind of food.

The yolks of eggs, the red meats (such as steak, mutton or the breast of wild game), and the deep colored greens, (such as spinach, chard, dandelions, etc.) contain a goodly proportion of iron. The dark color of greens and of the dark meats is given to them by the iron which they contain. The dark leaves of lettuce, celery, and cabbage contain iron, but these vegetables are apt to be bleached before being put upon the market.

The yolks of two eggs are better than one whole egg, as the iron is in the yolk. A good way to take the yolk of eggs is in egg lemonade or in eggnog, with a little nutmeg for spice.

FOOTNOTES:

[2] Winfield S. Hall, Ph. D., M. D., Prof. of Physiology, Northwestern University Medical School, Chicago.

Carbonaceous Foodstuffs

The carbonaceous foods are those used by the body for heat and energy and are so named because they contain a large proportion of carbon,—heat producing element. It is the carbon in wood, which, uniting with oxygen, produces heat and light.

The carbonaceous foods are all composed of carbon, hydrogen, and oxygen, the difference being in the different proportions in which these elements are combined.

They are divided into two classes, Fats and Carbohydrates. The carbohydrates embrace the sugars and starches and include such substances as the starches of vegetables and grains (notably corn, rice, wheat, and the root vegetables), and the sugar of milk, of fruits, vegetables, and the sap of trees. Their chief office is to create energy. They are almost entirely absent from meat and eggs, the animal having converted them into fats.

Carbohydrates are easily digested.

Fat

Fat is the most concentrated form of fuel and is readily oxidized. It is almost pure carbon, hence less chemical work is required to convert it into fuel, but more oxygen is needed. A pound of fat has about three times as much fuel value as a pound of wheat flour, which consists largely of starch.

Fat forms about fifteen per cent of the weight of the normal body, and it has about twice the fuel value of carbohydrates.

Carbohydrates and fats are each composed of carbon, hydrogen, and oxygen, the difference being that there is less oxygen in fat, hence, more oxygen from the air is required for combustion of fat than for carbohydrates. One pound of starch requires one and one-fifth pounds of oxygen for perfect combustion, while one pound of suet requires three pounds of oxygen. For this reason the Eskimo, who depends largely upon the fats for body heat and energy, must have plenty of fresh air. One ounce of fat yields two and one-half times as much energy as an ounce of sugar or starch.

If sufficient fat is not consumed, or is not formed from the carbohydrates (starches and sugars), a certain portion of the protein of the body is converted into fat and used in energy. When the food supply is short, or much energy is called for, the surplus supply of carbohydrates is first used, and, if the carbohydrates are not sufficient, the proteins are used. Of the proteins, the gelatinoids are used first, and next the albuminoids, or tissue builders. If the demand, either in mental or physical energy, exceeds the daily supply for a length of time, the body becomes lean.

In warm weather little fat is needed for fuel and nature provides fresh, green vegetables to replace the root vegetables of the winter, 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 in winter.

Those who store up an abundance of fat suffer most from a rise in temperature, because combustion not only creates heat, but heat also aids combustion.

Fats are not digested in the stomach. The connective tissue about the fat is digested here, and the fat is passed on into the small intestine, where it is acted upon by the carbonates and by lipase, one of the enzymes of the intestinal juices. These first change the fat into an emulsion and then into a form of soap and glycerine. In this saponified form, it is in condition to be absorbed into the circulation and carried out to the tissues, where it is assimilated and used in energy; a similar chemical change is produced in the conversion of oil into soap.

Common examples of fats are butter, cream, the fat of meats and of nuts, and the oil of grains and seeds,—notably the cocoanut, olive, and, of the grains, oatmeal.

The fact that more oxygen is required for combustion of fat than of starches and sugars is an important item for those who wish to call upon 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 food to supply the daily heat and energy released by exercise, the body calls upon the sugars and starches temporarily stored up and, when these have been consumed, upon the reserve of fat. If much fat is consumed in the daily food this fat in the blood will be oxidized before the fat stored about the muscular tissue. The scientific reduction of weight, therefore, lies in the regulation of the supply of starches, sugars, and fats consumed, 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.

Manual laborers require more fat for energy than do people whose habits are sedentary. School children, or children who play hard, should have sufficient fat, and where fats are withheld, sugar should be freely supplied.

The supply of fat stored in the body depends upon the quantity consumed with the food, upon the quantity used up in heat and energy, in muscular exercise, or in mental force. The quantity thus consumed depends somewhat upon the condition of the nerves. If the nerves are weak, they do not properly direct digestion and assimilation and less fat is consumed in the digestive and assimilative processes.

Butter and Cream. The fat present in milk depends, of course, upon the quality of the milk. There is as much butter fat in a glass of fresh Jersey milk as in a glass of cream, which has been separated, by machinery, from the milk of some other cows. The cream from some Jersey cows is almost all butter. Skimmed milk contains very little fat. If milk is drunk by the adult, as a means of storing up more fat within the body, the cream should be stirred into it.

The Fat of Meat should be thoroughly cooked and cooked with moisture. All meats in the process of baking or frying should be covered, in order to retain the moisture. To make fat easily digestible it should be well masticated.

Bacon, if fully immersed in its own grease, in the process of frying, is a common source of fat and is easily digested.

Cod Liver Oil from the liver of the codfish, is more easily absorbed and assimilated than any other fat. The odor is not pleasant and a little lemon juice, salt, baking soda, or any substance for pungency and flavor, may be added to make it palatable. The pure oil taken in this way is perhaps preferable to the prepared emulsions. One has the advantage, at least, of knowing what he is taking.

Olive Oil is crushed from ripe olives. It is often used where cod liver oil is prescribed, because more palatable. Cotton seed oil is often substituted or mixed with the cheaper grades of olive oil. It is wholesome, if fresh, but has not the pleasing flavor of the olive.

Many take olive oil for the purpose of rounding out the figure with fat. If the system will assimilate fat, taken in quantities, the fat may be stored up, but, as a rule, one is underweight because of a failure to assimilate the regular diet and the overloading with fat would not cause a better assimilation.

Olive oil in moderation is a good food where much heat and energy are expended, but if ones occupation is sedentary, much fat is not required.

Nut Oils are good, but, with the exception of peanut butter, are not often used.

Sugar

The sugars are cane and beet sugar, maple sugar, and glucose.

All sugars are carbohydrates,—carbon, hydrogen, and oxygen,—the oxygen and hydrogen being in the same proportions as in water, (two atoms of hydrogen and one of oxygen), the difference is that the carbon is missing from the water.

Sugar is said to consist of about ninety-five per cent nutritive value.

Glucose is made by converting the starch in corn into sugar. It is pure, wholesome, and cheap, and, for this reason, it is often used to dilute other sugars. It is not as sweet as other sugars, and it ferments more readily. Many of the syrups on the market are made from it.

The common, granulated sugars are made from sugar cane or beets; beet sugar is becoming more generally used.

Brown sugar is granulated sugar in the early stages of refinement.

Maple sugar is obtained by boiling down the sap of the maple tree. It is often adulterated with other sugars or with glucose, because they are cheaper. This adulteration does not make it unwholesome, but when mixed with these it loses its distinct, maple taste and is more mild.

Before sugar can be used by the human system, it is changed into grape sugar, or dextrose, (another form of sugar) by a ferment in the small intestine called lactose. Milk sugar needs less chemical change than other sugars and is taken almost at once into the circulation.

When an excess of sugar is consumed, it is stored within the body as glycogen, until required.

Sugar is perhaps a better food than starch, because less force is required for its digestion and it is easily assimilated, being more readily converted into dextrose than are starches. Moreover it furnishes the needed heat and energy to organisms that have no power to digest starch. Milk sugar is a part of the natural food for the infant, because the infant has not developed the ferment necessary for starch digestion.

Sugar may be oxidized within a few minutes after eating, and, for this reason, it is eaten by those who require to use an undue amount of muscular strength. It yields heat and energy within thirty minutes after eating and, in times of great exertion or exhausting labor, the rapidity with which it is assimilated gives it advantage over starch. Used in limited quantities, therefore, according to the muscular or brain power exercised, sugar is one of the best foods for the production of energy. Where much sugar is eaten less starch is required.

It is also said to prevent fatigue, a man being able to do seventy-five per cent more muscular work with less fatigue after consuming about seventeen and one-half ounces of sugar dissolved in pure water.

It might be inferred from the above, that starches could be discarded and replaced by sugars, but a small quantity of sugar soon surfeits the appetite and if the foods were confined to those with a surplus of sugars, sufficient food would not be eaten for the needs of the body. This lack of appetite, occasioned by an excess of sugars, is due, partly, to the fact that the gastric juice is not secreted as freely when there is much sugar in the stomach.

Because of the slower secretion of gastric juice and the surfeit of the appetite, sweetened foods are not used at the beginning of a meal, and, while a moderate amount of sugar is desirable, a surfeit is to be deplored.

While sugar is not converted into fat, it is so readily oxidized and thus supplies heat and energy so promptly that the starches and fats are not called upon until the latent energy in the sugar is used. Those who wish to reduce in flesh should eat it sparingly that the starches and fats may be called upon to furnish energy, but sugar should be as freely used as the system can handle it, by those who wish to build up in flesh.

Broadly speaking, about one-fourth of a pound of sugar, daily, in connection with other foods, is well utilized by the system, the quantity depending upon whether one leads an active or a sedentary life.

Candy is often made from glucose instead of molasses or cane sugar, and while glucose is wholesome, it undergoes fermentation readily. Much candy, unless one is actively exercising, tends to indigestion.

The desire of the child for sweets is a natural one, because it uses so much energy, and sugar supplies this energy with less effort of the digestive system. When the child begins to eat more solid foods, if sugar is used in abundance for sweetening, it is no longer attracted by the mild sweetness of fresh milk, and it is well to cut down the allowance of sugar, when the child turns against milk, in the hope of restoring the taste for this valuable food. Many of the best authorities state that the child, up to its third year, should never be allowed to taste sweets, in order that the appetite may not be perverted from the natural sweets of milk.

Sugar is better supplied the child in a lump or in home-made candy, rather than in the sweetening of porridge, oatmeal, or bread and milk, etc.

Sweet fruits, fully ripened, contain much sugar and should be freely given to the child. The natural flavor of fruits and grains is very largely destroyed by sugar, which is used too freely on many articles of diet.

Most vegetables and fruits contain sugar,—indeed sugar is the only nutriment in many fruits. The sweet taste in all fruits and vegetables is due to its presence. Sweet potatoes, beets, carrots, parsnips, turnips, grapes, figs, and dates are especially rich in sugar and when these are furnished with a meal, in any appreciable quantity, the starches should be restricted—notably bread, potatoes and rice.

Harvesters, road-makers and others, who do hard work in the open air, can consume large quantities of sugar in pie, pastry, etc., which are difficult to digest, while one who lives an indoor life, should refrain from an undue indulgence in these.

For one who is undernourished, sugar is a desirable food, if the starch be diminished in proportion as the amount of sugar is increased; but the inclination in sweetening foods is to take more starch than the system requires, since it is the carbohydrate foods which are ordinarily sweetened,—not the proteins.

On account of the latent heat and energy, sugars are more desirable in cold weather than in warm. Nature supplies them more abundantly in root vegetables for this season. More puddings and heavier desserts are eaten in winter.

Starch

Starch is one of the most important carbohydrates used for nutrition. It is formed by the chemical action produced by the sun’s rays upon the cells of living plants, from the carbon-dioxid and water in the air and in the soil.

Corn starch, sago, tapioca, and arrowroot are practically pure starch. Cornstarch is from young maturing corn; tapioca is from the meal of a tropical plant, cassava; sago is from the pith of the sago palm; arrowroot is from a plant of the same name, a native of the West Indies. Rice is almost pure starch, while wheat and other cereals contain from sixty to seventy per cent.

Starch lacks flavor and for this reason all starchy foods are seasoned.

All starches must undergo much chemical change by action of the saliva, the intestinal juice and by the liver, before they can be used by the body. They are first converted into dextrine and then into maltose (animal sugar). The digestion is begun by the saliva in the mouth and continued in the stomach by the saliva swallowed with the food. If the saliva fails to digest all of the starch, either in the mouth or the stomach, it passes unchanged into the intestines, where it is converted by the amylase of the intestinal juice, first into dextrine and then into maltose, or sugar. It is absorbed into the blood as sugar. After the digested starch (maltose) passes into the blood it is spoken of as sugar. Before it is converted into energy it is again changed in the liver into animal starch (glycogen) and stored for a time in the liver. When the system is ready for it, it is again broken down into sugar, because in the form of glycogen it cannot be absorbed into the blood.

The chemical process used in the formation of glucose, from the starch in corn, is allied to the change in the liver, from starch into sugar.

The starches and sugars are really the “reserves” or “go-betweens” of the body, being stored until needed.

If starches are consumed in unduly large quantities, without sufficient exercise to burn them up, they overload the liver and clog the system.

Starchy foods should not be given to children before the starch converting ferments are formed, nor to one in disease where these ferments are interrupted.

Nitrogenous Foodstuffs or Proteins

The proteins form heat and energy when the supply of sugars, starches, and fat are exhausted, but proteins, alone form muscle, bone and sinew. They are, in this sense, the most important of foods,—they are, also, the most costly.

The foods most rich in proteins are meat and eggs. These have undergone chemical changes from the vegetable kingdom being built up into more complex compounds in the animal kingdom.

Meat and eggs are the tissue builders. In this connection it may be well to state that blood is tissue; thus meat and eggs build the blood, as well as muscle and sinew.

Nitrogenous foods, or proteins, are so called because of the large proportion of nitrogen which they contain. All nitrogenous foods contain considerable carbon—mostly in the form of fat in the meat elements—but the carbonaceous foods contain so little of the proteins that they do not appreciably enter into the nutrition,—the carbon and nitrogen in the carbo-nitrogenous foods are more equally divided.

The nitrogenous or protein elements in the body constitute about one-fifth of its weight. They make the framework, forming the basis of blood, lymph, muscle, sinew, bone, skin, cartilage, and other tissues.

Worn out body tissues is constantly being torn down and eliminated and the protein in the foods must daily furnish material for repair, as well as for building new tissue in the growing child.

A young animal’s first need is for growth, not having learned to exercise sufficiently to use much energy, and the first food given is an animal product—milk to babes and other mammals, while the young of other animals are first fed upon eggs.

The nitrogenous foods are required in smaller bulk than vegetables and fruits; they are more concentrated and contain less waste. According to recent experiments, the average adult requires from two to four ounces a day of nitrogenous foods, to repair the waste, according to the proportion of nitrogen contained. Happily, where more is consumed, the system has the power, up to a certain limit (depending upon the physical condition and the daily activity), to eliminate an excess. It is needless to say that if the daily waste is not re-supplied, the digestion and bodily nutrition suffer. The system must have the two to four ounces to supply the nitrogen daily excreted, or the tissues themselves will be consumed.

The proteins, of which meat is the principal one, are classified as

Albuminoids:—albumin (white of eggs), casein (curd of milk), myosin (the basis of lean meat and gluten of wheat),

Gelatinoids, (connective tissue of meat),

Extractives (appetizing and flavoring elements).

DIGESTION

Any discussion in regard to 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; therefore, before one passes upon the adaptability of a food to the individual, it should be known that this food agrees or disagrees with him under varying conditions.

The digestibility of food depends largely upon 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 into the blood. Digestion is practically synonymous with solution,—all solid foods must be reduced to a liquid state, through digestive juices and water, before they can pass through the walls of the stomach and intestines.

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. The question of likes and of dislikes in regard to foods, is largely habit, and one can learn to like almost any food one wishes.

Where one forms the habit of discriminating too much in the food, or 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 as a more or less pessimistic censor 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. There are kinds of foods, however, which, to certain individuals, according to the chemical composition of the body, act as actual poisons, e. g., strawberries, cheese, or coffee.

It may be well to here trace, briefly, the progress of the food through the digestive tract and the action of the juices and the ferments upon it.[3]

Salivary Digestion

The food in the mouth is mixed with saliva, which dissolves the starches, converting them into sugar. The starches are the only foods whose chemical digestion is begun in the mouth. They are first broken up into dextrin and then into the more simple sugar, known as animal starch, or maltose. Hereafter, in speaking of sugar, after it has been absorbed into the blood, the reader will bear in mind that the term refers not only to digested sugar, consumed as such, but also to digested starches (maltose), as shown on page [63].

It is important that sufficient saliva be mixed with the food, through mastication, that it may enter the stomach and there continue the chemical process of digestion of starch. If starches are not thoroughly masticated, sufficient saliva will not enter the stomach to convert the starch into sugar; the food will pass into the small intestine, which must then do more than its normal work of digestion.

The saliva consists of about ninety-nine and one-half per cent water and one-half per cent solids. The solids consist of ptyalin, sodium chlorid, sodium carbonate (baking soda), mucus, and epithelium. Ptyalin, the most important of these, is an active digestive agent; the mucus lubricates the masticated food; the sodium carbonate insures the alkalinity of the food; the salt is present in all secretions; and the water dissolves the food that the juices may more readily reach and act upon each particle.

The saliva flows into the mouth, more or less, at all times, but more copiously during mastication. Its evident purpose, when food is not present, is to keep the lining of the mouth moist.

The flow of saliva is controlled, to a great degree, by nerves which have their centers in the medulla oblongata. The sight of food, pleasingly served, or even the thought of food which one likes, will increase the salivary flow. This is one instance of the control of thought materially affecting 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 perfect will be the first step in digestion. This first step of thorough mastication is all important, not only because the chemical action upon the starch molecules is facilitated by the thorough softening and mixing with the saliva, but thorough mastication also tends to prevent overeating.

Water encourages the flow of saliva and for this reason should be drunk copiously before meals, particularly where digestion is weak. It may also be taken at rest periods during the meal. (See page [44]).

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. It consists of ninety-nine and one-half per cent water and one-half per cent solids, as does the saliva. The solids of the gastric juice are composed of pepsin, rennin, hydrochloric acid, and mucus. The mucus serves to lubricate the food as in the saliva. It also prevents the digestion of the mucous lining of the stomach itself.

The hydrochloric acid and the pepsin cause the principal chemical changes in the food while in the stomach, acting alone upon the proteins. The only digestion of starches in the stomach is that continued by the saliva. The salivary digestion proceeds until the gastric juice is secreted in sufficient quantity to cause a marked acidity of the stomach contents, when the starches are passed into the intestines.

Gastric juice begins to flow into the stomach soon after eating, but 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 proteosis 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 the gastric digestion will be completed in one and one-half to three hours. If not properly cooked and masticated, the stomach digestion may continue one to two hours longer. It should, however, be completed in three hours.

The most readily digested animal foods remain less time in the stomach. Meat, as a rule, is easily digested, because the action of the digestive juices of the animal has converted the starches and sugars. The white meat of chicken, being soft, is digested in a shorter time than the red or the dark meat.

Fluids leave the stomach more rapidly than solids. Seven ounces of water leave the stomach in one and one-half hours, seven ounces of boiled milk in about two hours.

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, regulates its flow.

After the food has extensively accumulated, during the progress of a meal, the stomach begins a series of wave-like movements called peristaltic waves.[4] These waves work downward through the length of the stomach towards its lower opening, known as the pyloric orifice. As the food is moved down the stomach by these motions, it is thoroughly mixed with the gastric juice.

During the early stages of digestion, the sphincter muscles of the pylorus keep the lower end 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 upon by the gastric juice,—the solid mass is not allowed to pass until dissolved.

If the individual continues to abuse the stomach and to cause 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 demand for a rest is termed Indigestion.

To sum up,—digested sugar is dextrose; digested starch is first dextrin, then maltose (animal, sugar); digested protein is peptone; and, digested fat is saponified fat.

Intestinal Digestion

The food passes from the stomach, through the pylorus into the small intestine. The first twelve inches of the small intestine is known as the duodenum. In the duodenum it is acted upon by the pancreatic juice from the pancreas, the bile from the liver, and the intestinal juices. These juices act upon proteins, fats, and carbohydrates. The bile acts upon the fats, while the pancreatic and intestinal juices act chiefly upon the carbohydrates.

As the food enters the intestine, it is changed, by the sodium carbonate, from the acid condition produced in the stomach, to alkaline reaction.

The bile exercises an important influence upon digestion, any disturbance in the flow of this greenish-brown secretion being very quickly shown both in stomach and intestinal digestion. It emulsonizes and saponifies the fats, it aids in their absorption, and it 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.

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 from the liver. For this reason, if the liver is sluggish, fatty foods are desirable. Olive oil is prescribed for gall stones to stimulate the action of the bile ducts.

Before the fat molecules can be absorbed, they must first be broken up into glycerin and fatty acids and further changed to a fine emulsion, which gives the contents of the small intestine a milky appearance. After they are broken up into these fatty acids and thus brought to the finest state of emulsion, they are readily saponified, being then soluble in water and in a state to be absorbed by the walls of the intestines. The fats are absorbed almost entirely in the small intestine,—mostly in the duodenum.

As a rule, the starches, or dextrin, will not be fully digested by the saliva and those which have failed of salivary digestion are acted upon by amylase (one of the solids of the intestinal juice) and changed to maltose, while the trypsin from the pancreas, together with the intestinal juice, acts upon any protein which has failed to be fully digested in the stomach, changing it into peptone. In the form or peptone it is absorbed through the “sucking” villi of the intestinal walls.

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 sub-mucous lining. (See page [78]).

It is now believed that a larger proportion of food is digested and absorbed than was heretofore realized, and that 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 the sub-mucous 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.

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 intestines.

The small intestine is particularly fitted for absorption. Every inch or so along its course the mucous lining is thrown up into folds, as if to catch the food as it passes toward the large intestine, and to hold it there until the villi have the opportunity to absorb it. These transverse folds of the intestinal walls are called valvulæ conniventes. The villi are fingerlike projections of the mucous lining of the intestines, which stand out upon 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 a dissoluble state ready for absorption, they are very promptly absorbed by the villi. If, for any reason, they remain unabsorbed, they are liable to ferment by the action of the trypsin, or to be attacked by the bacteria always present in the intestines.

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 ileo-cecal valve into the large intestine.

That the large intestine is also adapted to the absorption of fats is shown by clinical experiments with patients who cannot retain food in the stomach, the food in such cases being given through rectal injections.

In the large intestine, the mass passes up the ascending colon, across the transverse colon, and down the descending colon, losing, by absorption, foodstuffs not absorbed in the stomach and small intestine.

While water and salt are absorbed both in the stomach and in the small intestine, the evident purpose in leaving the larger part of the water to be absorbed in the large intestine is that it may assist the intestinal contents in passing along. The water also stimulates the peristaltic movement.

As the food is absorbed through the walls of the alimentary canal, it is picked up by the rootlets of the mesenteric veins[5] 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, meaning “whitish.”

Nearly all of the proteins and sugars pass through the mesenteric veins and the portal veins into the liver. Here the sugars are at once attacked by the liver cells and built up into glycogen as described on page [81] and the proteins are passed through the liver into the arterial blood stream. 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.

To sum up,—the larger part of the absorption of sugars, starches, proteins, and fats is through the small intestine, though some are 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.

FOOTNOTES:

[3] A knowledge of the mucous lining of the stomach and intestines, and of the tributary glands, such as the liver and pancreas, is important to a thorough understanding of digestion, and the reader is referred to “The Vital Organs: Their Use and Abuse” of this series. This takes up the study of the secretion of digestive juices, the conditions favoring normal secretions, etc.

[4] See “The Vital Organs; Their Use and Abuse” by Susanna Cocroft.

[5] For illustration see the frontispiece of “The Circulation, Lungs, Heart,” of this series.

The Work of Various Organs Affecting Digestion

The purpose of this chapter is to show the work of other organs than the digestive organs in converting the digested food to use in the body, in tearing down waste, and in eliminating waste and an excess of material above the body needs.

Work of the Liver

The liver is commonly called the chemical work-shop of the body. The proteins and sugars are carried through the blood (portal veins) to the liver directly they are absorbed from the alimentary canal. As the food materials filter through the blood capillaries, between the liver cells, several substances are absorbed, particularly sugar, which is here changed into animal starch called glycogen. It is held in the liver for a few hours in the form of glycogen and then redigested by the action of an amylolitic ferment and again gradually given out into the blood in the form of sugar; hence sugar is subject first to the anabolic change of being built up into glycogen, and then to the catabolic change of oxidation and breaking down.

While the conversion of the sugar is one chief office of the liver, it also acts upon the proteins,—not as they are first passed through the liver in the blood, but as they are returned to the liver from the muscle tissue, partly oxidized and broken up into simpler products. The liver cells absorb and further oxidize and combine them into nitrogenous waste, which the kidneys throw off in urea.

The liver and the spleen also break up the pigment or coloring matter of the red blood corpuscles. As they become worn out, they are retired in the liver and the spleen from the circulation. The iron is retained by the liver cells and the remainder is thrown off from the liver, in the bile.

The liver is often called the watch dog of the body, because it is on guard for all poisons which pass through it in the blood. The large part of these toxic substances are absorbed through the alimentary canal with other foodstuffs. Many of them are the result of the fermentation of foods which are not digested as promptly as they should be, on account of an insufficient secretion of digestive juices, or a failure to secrete them in normal proportions, or due to inactivity of the stomach and intestines.

It surely is a wise provision of nature to supply a guard to oxidize, or break down these poisons and make them harmless, so that they do not pass to all parts of the body as poisons, thus affecting the nerves and the blood stream, and, through these, the entire system.

The necessity of correct habits of deep breathing will be readily seen, because oxygen is required to break down the poisons as well as to oxidize the waste of the system.

One example of the action of the liver in rendering substances harmless, is its oxidation of alcohol. From one to three ounces of alcohol a day are oxidized and made harmless in the liver, varying according to the individual and to the condition, at different times, in the same person. If the limit of one to three ounces is exceeded, the excess is not oxidized and intoxication results. These evidences of intoxication are in the nature of narcosis; alcohol is now regarded as a narcotic along with ether and chloroform.

It was formerly held by physiologists that alcohol was a food, because its oxidation liberates body heat and it was assumed that this liberation of heat, was the same as that freed by the combustion of fats, starches, and sugar uniting with oxygen. More recent knowledge, however, has unquestionably determined that heat, resulting from oxidation of alcohol, does not keep up body temperature; the pores of the skin are opened and there is a greater loss of heat through the skin. This really makes the system less able to resist cold. Large doses of alcohol actually cause a fall in body temperature and every force of the body is decreased in efficiency, while if alcohol were an actual food the efficiency would be increased. We are forced to the conclusion, therefore, that alcohol is a pseudo-food as it is a pseudo-stimulant.

Work of the Muscles

The muscles play an important part in the use of foods. Most of the heat is generated in them, by the sugar and fats coming in contact with the oxygen in the blood. This heat is liberated during every moment of the twenty-four hours, asleep or awake. Of course, more is liberated during exercise, since the movement of the muscles sets all tissues into activity and the blood circulates more strongly, bringing a greater supply of oxygen to them. It is always well during active exercise to stop frequently and fully inflate the lungs. The effort should always be made to breathe fully and deeply—otherwise the pressure of the liberated carbon dioxid will cause a pressure throughout the blood stream, particularly about the heart and in the head. This pressure is relieved when the excess of carbonic acid gas liberated has been thrown off by the lungs. Nature makes the effort to throw off the excess of carbonic acid gas by forcing one to breathe more rapidly while running or taking unusual exercise.

The oxidation changes are simply a combustion of sugars and fats, liberating latent heat as they are brought into contact with the oxygen. Exercise and a regulation of the amount of carbohydrates and fats consumed in the foods is the natural, scientific method for the reduction of an excess of fat.

A certain amount of protein is constantly oxidized in the muscles, also, being broken down into carbon dioxid, water and a number of nitrogenous mid-products. The carbonic acid gas and water are thrown off by the lungs and the partially oxidized, nitrogenous waste is carried to the liver, where it is further oxidized and prepared for excretion, through the kidneys, lungs, skin and intestines.

When sugar is carried to the muscles in larger quantities than can be utilized by them, it is often built up into animal starch and stored in the form of glycogen, similar to its chemical change and storage in the liver.

This storage of glycogen in the muscles and in the liver is a wise provision of Nature. It is a reserve to be called upon whenever the expenditure of heat and energy exceeds the amount supplied in any day’s rations.

Work of the Nerves

The nerves oxidize food materials, but not to any great extent, excepting during nervous activity. During periods of rest, food materials are stored in the nerve cells in grandular form. They represent concentrated nerve foods and are the result of anabolic processes. During nervous activity they are oxidized and carried away through the blood and the lymph. This oxidation of the food, stored in the nerves, creates nervous energy and heat.

The energy liberated by the nerves resembles electrical energy.

Where one subjects himself continuously to an excess of nervous activity, all reserve food material, stored in the nerve cells, is used and the result is a trying nerve tension. Such individuals need plenty of easily digested food.