In other words, our food supplies the elements which build, sustain, repair, and renew corresponding elements in our bodies. We eat oxygen, hydrogen, nitrogen, carbon, iron, arsenic, lime, magnesia, potash, soda, silica, etc., to replace similar elements in our bodies. These we find most abundantly in vegetables, fruits, cereals, meats, eggs, fish, milk, etc., and we eat them in sufficient quantities to renew our bodies’ waste, to replace the material which has been burned or consumed by the day’s run of our human mechanism. Whatever we eat which is not like the materials of our bodies will do us no good, because it will find no affinity, no response in any of our tissues, and hence will have to be excluded as poison or waste. The tissues cannot use it, since they can only absorb things like themselves, things which have the same constituent parts. Only brain materials, for instance,—that is, the things that make our brains,—can build, repair, or renew brains. Only the materials which produce bone can be utilized in our skeletons; only foods which contain the materials that the. nerves are made of can build nerves; so that, literally, we are ever eating and reabsorbing the elements of our bodies. Nothing else can be absorbed by our tissues when in health except to our injury.
There are three classes of food that are imperative for the building and maintenance of all the different parts of the body. Albuminous foods, which come mainly from meat, eggs, milk, and the legumes, are good, everyday working foods. Sugars, starches, and fats, called carbohydrates, and vegetables produce various energies in the body, as illustrated in muscular activity, and the different fats which come from both animal and vegetable foods produce heat. We must also have mineral foods, such as iron, lime, phosphorus, magnesia, etc., which purify the blood, give firmness to the tissues, and help to maintain proper electrical tension.
The absence of any of these different forms of food, the tissue builders, the body warmers, the energy producers, or the blood purifiers, would cause starvation in certain tissues, and ultimate death. If the body were fed wholly on the materials which build tissues, the digestive processes and other functions would stop. On the other hand, if we should partake only of the materials which furnish energy alone, the energy of force-forming foods, we should soon die from over activity and the starvation and gradual wasting away of the solid tissues. No matter how much of the starches or sugars or fats you might eat, they would maintain only the energies or the activities of the body, while if you lack tissue builders the structure of your body would begin to deteriorate. The white men who first went to visit South America pined away one by one from tissue starvation, because, while they could get plenty of food, they could not get a sufficient variety to feed all of the tissues. That is, they could not get sufficient flesh formers and flesh warmers in the right proportion to sustain life.
In order, therefore, to maintain perfect health, there must be a balance, a poise, of the different kinds of foods, the tissue builders and renewers and the foods which furnish the heat and support the various energies of the body, as well as certain minerals which are purifiers and regulators of the blood and other secretions, and water, which liquefies and facilitates the carrying of nutrition to the various tissues. Of course, without water the blood circulation would be impossible; for though the water itself does not form tissues or furnish energy, its presence in large amounts is absolutely imperative for carrying on a multitude of life processes. Without it the various chemical changes, the circulation and the secretion of various organic fluids would also be impossible.
An ordinary adult needs from ten to twenty ounces of body warmers, according to activity and climate; that is, of carbonaceous foods, such as sugars, starches, fats, etc.; and five ounces of flesh formers, of nitrogenous foods which contain albumen, etc., or practically at least a pound of body warmers and flesh formers a day from animal or vegetable food.
It is supposed that about seven out of ten ounces of carbonaceous food would be burned in the bodily combustion, making heat and supplying the forces which are used up in the various activities of the body. The remaining three ounces should be used for padding between the muscles and for covering the bones to make the body more comely. When we are working very hard, or in the summer time, we burn up more of our fat and usually get thinner; but it is not safe to burn up all of the heat and energy food each day, because one would then not have a reserve of energy and in an emergency would lack resisting power.
This, of course, is a rough general estimate, and could not be laid down as a hard and fast rule, for all to follow. If the food of each individual were properly balanced and each of the glands and tissues found just the right kind and the right amount of nutriment in the blood stream to maintain the integrity and perfect balance of the entire body, there is no doubt that the level of human efficiency would be raised very much higher than it is to-day. But no physician, no physiologist living, could possibly make out a bill of fare that would meet the needs of all alike.
No common diet could be prescribed for everybody. Each individual, according to his age, his physical condition, and his temperament would have to make exceptions and study his own requirements. But we know by experience that people living under different conditions, doing different kinds of work, are very materially helped by foods especially rich in the elements which enter into the structure and maintenance of the tissues which are most active in that sort of life or vocation. The kind and amount of food required by different people depend a great deal upon the degree of rapidity with which the cell life of any particular tissue or organ is broken down by its activity. The brain and nerve cells, for example, are broken down very rapidly in intense mental exercise or mental application, whereas destruction would be comparatively light if the brain were used very little, as in the case of persons whose activity is chiefly muscular.
It is well known that animals should be fed according to the work they do and their mode of living. A hunting dog requires a different food from a house dog. A driving and trotting horse, a race horse, requires a very different food from a dray horse, that carries a heavy load. Speed requires food like oats, which gives up a quick energy. Corn is too heavy for the speed horse. On the other hand, oats do not have the same staying power as corn.
The human animal must also be fed to fit him for his particular work. What would you think of a trainer who would constantly stuff a young athlete with all sorts of food he could get regardless of its properties, whether it made fat or muscle? You would certainly think the man did not know his business. Even those who have not studied the matter know that an athlete must be trained for speed, endurance, or muscular strength, according to the nature of the contest. Every bit of food that does not help toward this end is excluded from the diet. All foods that tend to produce fat instead of sustaining prolonged muscular effort are cut off. Every bit of material that will burden,—all overeating, is forbidden. Every mouthful which is unnecessary for sustenance and strength building, which would be an additional tax upon the digestive organs and the nervous tissues, in order to get rid of its injurious effects, must be excluded. The problem is to produce the maximum of muscular strength and endurance, to take only the foods which can sustain the heart in its stupendous strain, in running, leaping, wrestling, etc. The great object is to build up perfect muscle fiber and to eliminate everything which would tend to produce fat cells in the muscles, especially in the heart muscles, which would tend to weaken the vigor of its stroke.
The first consideration in the food question is to supply the physiological requirements of the body without a lack or scantiness anywhere which would cause deterioration in any tissue, or a surplus which would clog the organs and result in poisoning the body through the decomposition of half-digested foods.
For example, a person engaged in an athletic contest, like bicycle racing, carried on for a week or more, would need a great deal of energy-producing material to supply the rapid waste of broken-down tissues in the muscular system. This need must be quickly supplied by foods which are combustible in the body and which yield a large amount of energy and comparatively little of what we might call the tissue-building elements, because the principal loss of persons in such a contest is in the energy and heat producing products which come from rapid combustion. If a contestant took too much