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.
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 cannotappropriate 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 adeficiency 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 isprotein. The skeleton is composed largely of deposited salts, while the elements which supply heat and keep up muscular activity arestarches, fats, and sugars.
Theproteinsare 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 proteinand 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-sixthof 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 offats, 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 chemicalaction, and the nervous in nervous energy. The nervous energy is closely allied to electrical force.
Thestarchescome largely from cereals and root vegetables; thesugarslargely from cane, from certain trees, and from vegetables, fruit, and milk; thefatscome 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 thetissues, 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 skinare 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 thebath. 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 waterto 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 frequentlybent 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 collectivelymetabolism. They are divided into two groups: the chemical process of building up complex substances from simple ones is known asanabolism; the chemical process of oxidizing and breaking down the complex substances into simple ones, so that they are in a state to be excreted, iscatabolism. 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 toassimilatethe 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.
Byassimilationis meant the digestive process by which foodstuffs are made soluble and diffusible, so that they can passinto 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.