Part 3 (2/2)
Each individual must decide for himself what is the right amount of food to eat. In general, that amount is right which will maintain the most favorable condition of weight. If the weight, endurance, and general feeling of well-being are maintained, one may a.s.sume that sufficient food is taken.
[Sidenote: Brainwork and Eating]
It is physical, not mental work, which uses up the greater part of our food. The common impression that brain-work or expenditure of mental energy creates a special need for food is erroneous. The sedentary brain-worker often gains weight without eating very much. What he really needs is exercise, to use up the food, but if he will not take exercise, then he should reduce his food even below the small amount on which he gains weight.
[Sidenote: Eating When Fatigued]
Which meal in the day should be heavy and which light depends largely on one's daily program of work, the aim being to avoid heavy meals just before heavy work. When very tired it is sometimes advisable to skip a meal or to eat only lightly, as of fruits and salads. A man who eats heartily when he is very tired is likely to be troubled afterward with indigestion.
(See SUPPLEMENTARY NOTES for specific directions regarding diet for underweight and overweight.)
Section II--Protein Foods
[Sidenote: Protein, Fat, and Carbohydrate]
In the last section it was stated that food is fuel. But there is one const.i.tuent of food which, while it _can_ be used as fuel, is especially fitted for an entirely different purpose, namely, to build tissue, that is, to serve for the growth and repair of the body. This tissue-building const.i.tuent in food is called protein. The two other chief const.i.tuents in food are fat and carbohydrate, the last term embracing what are familiarly known as starch and sugar. Fats and carbohydrates are only for fuel and contain carbon as the essential element. Protein contains nitrogen as the essential element in tissue-building. The white of egg and the lean of meat afford the most familiar examples of protein. They consist entirely of protein and water. But meat and eggs are not the only foods high in protein. In fact, most ordinary foods contain more or less protein. The chief exceptions are b.u.t.ter, oleomargarine, oil, lard, and cream--which consist of fat (and water)--and sugar, sirups, and starch, which consist of carbohydrate (and water).
[Sidenote: Proportion of Protein]
Foods should be so selected as to give to the ration the right amount of protein, or repair-foods, on the one hand, and of fats and carbohydrates, or fuel-foods, on the other. A certain amount of protein is absolutely essential. While, for a few days, protein may be reduced to little or nothing without harm, if the body be long deprived of the needed protein it will waste away and ultimately death will result.
Therefore, too little protein would be a worse mistake than too much.
The right proportion of protein has been the subject of much controversy. According to what are regarded as the best investigations, it is generally about 10 per cent. of the total number of heat-units consumed. This does not, of course, mean 10 per cent. of the total weight nor 10 per cent. of the total bulk, but 10 per cent. of the total nutriment, that is, 10 calories of protein out of every 100 calories of food.
[Sidenote: Human Milk]
Most persons in America eat much more protein than this. But that 10 calories out of 100 is not too small an allowance is evidenced by the a.n.a.lysis of human milk. The growing infant needs the maximum proportion of protein. In the dietary of the domestic animals, the infant's food, the mother's milk, is richer in protein than the food of the grown animal. Consequently an a.n.a.lysis of human mother's milk affords a clue to the maximum protein suitable for human beings. Of this milk 7 calories out of every 100 calories are protein. If all protein were as thoroughly utilized as milk-protein or meat-protein, 7 calories out of 100 would be ample, but all vegetable proteins are not so completely available. Making proper allowance for this fact, we reach the conclusion that 10 calories out of every 100 are sufficient.
[Sidenote: Excessive Use of High-Protein Foods]
A chief and common error of diet consists, then, in using too much protein. Instead of 10 calories out of every 100, many people in America use something like 20 to 30. That is, they use more than double what is known to be ample. This excessive proportion of protein is usually due to the extensive use of meat and eggs, although precisely the same dietetic error is sometimes committed by the excessive use of other high-protein foods such as fish, sh.e.l.l-fish, fowl, cheese, peas and beans, or even, in exceptional cases, by the use of foods less high in protein when combined with the absence of any foods very low in protein.
The idea of reducing the protein in our diet is still new to most people.
[Sidenote: Injuries From Over-abundance of Protein]
Prof. Rubner of Berlin, one of the world's foremost students of hygiene, said, in a paper on ”The Nutrition of the People,” read before the recent International Congress on Hygiene and Demography:
”It is a fact that the diet of the well-to-do is not in itself physiologically justified; it is not even healthful. For, on account of false notions of the strengthening effect of meat, too much meat is used by young and old, and by children, and this is harmful. But this meat is publicly sanctioned; it is found in all hotels; it has become international and has supplanted, almost everywhere, the characteristic local culinary art. It has also been adopted in countries where the European culinary art was unknown. Long ago the medical profession started an opposition to the exaggerated meat diet, long before the vegetarian propaganda was started. It was maintained that flour foods, vegetables, and fruits should be eaten in place of the overlarge quant.i.ties of meat.”
When protein is taken in great excess of the body's needs, as is usually the case in the diet of Americans, added work is given the liver and kidneys, and their ”factor of safety” may be exceeded.
[Sidenote: Animal Proteins]
Flesh food--fish, sh.e.l.l-fish, meat, fowl--when used in great abundance, are subject to additional objections. They tend to produce an excess of acids, are very p.r.o.ne to putrefaction, and contain ”purins” which lead to the production of uric acid. This is especially true of sweetbreads, liver and kidney. The well-known deficiency in flesh foods of lime often needs to be taken into consideration in the dietary. Some of the vegetable foods, such as peas and beans, rich in protein, are likewise not free from objection. Their protein is not always easily digested and is, therefore, likewise liable to putrefaction. Unlike most vegetable foods, they contain some purins. These foods are, however, rich in iron, which renders them a more valuable source of protein for children and anemic people than meat. Also, an excess of protein is not so likely to be derived from such bulky foods as from meat, which is a concentrated form of protein.
We have spoken thus far only of the needed proportion of protein. The remainder of the diet, say 90 per cent. of the calories, may be divided according to personal preference between fats and carbohydrates in almost any proportion, provided some amount of each is used. A good proportion is 30 per cent. fat and 60 per cent. carbohydrate.
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