The quantity of food to be taken varies with the demands of the individual appetite and the individual powers of absorption. In general, one who is engaged in physical labor needs more, because of increased appetite and increased waste of tissues. So a farm-hand needs more food than a college student, whose work is mostly indoors and sedentary. Much has been said recently about the ills of overeating. One of the most enthusiastic defenders of a decreased diet is Mr. Horace Fletcher, who, by the practice of protracted mastication, "contrives to satisfy the appetite while taking an exceptionally small amount of food. Salivary digestion is favored and the mechanical subdivision of the food is carried to an extreme point. Remarkably complete digestion and absorption follow. By faithfully pursuing this system Mr. Fletcher has vastly bettered his general health, and is a rare example of muscular and mental power for a man above sixty years of age. He is a vigorous pedestrian and mountain-climber and holds surprising records for endurance tests in the gymnasium.
"The chief gain observed in his case, as in others which are more or less parallel, is the acquiring of immunity to fatigue, both muscular and central. It is not claimed that the sparing diet confers great strength for momentary efforts—'explosive strength,' as the term goes—but that moderate muscular contractions may be repeated many times with far less discomfort than before. The inference appears to be that the subject who eats more than is best has in his circulation and his tissues by-products which act like the muscular waste which is normally responsible for fatigue. According to this conception he is never really fresh for his task, but is obliged to start with a handicap. When he reduces his diet the cells and fluids of his body free themselves of these by-products and he realizes a capacity quite unguessed in the past.
"The same assumption explains the fact mentioned by Mr. Fletcher, that the hours of sleep can be reduced decidedly when the diet is cut down. It would seem as though a part of our sleep might often be due to avoidable auto-intoxication. If one can shorten his nightly sleep without feeling the worse for it this is an important gain."
But the amount of food is probably not so important as the kind. Foods containing much starch, as potatoes and rice, may ordinarily be taken in greater quantities than foods containing much protein, such as meats and nuts. So our problem is not so much concerned with quantity as with the choice of kinds of food. Probably the most favorable distribution of foods for students is a predominance of fruits, coarse cereals, starch and sugar and less prominence to meats. Do not begin the day's study on a breakfast of cakes. They are a heavy tax upon the digestive powers and their nutritive value is low. The mid-day meal is also a crucial factor in determining the efficiency of afternoon study, and many students almost completely incapacitate themselves for afternoon work by a too-heavy noon meal. Frequently an afternoon course is rendered quite valueless because the student drowses through the lecture soddened by a heavy lunch. One way of overcoming this difficulty is by dispensing with the mid-day meal; another way is to drink a small amount of coffee, which frequently keeps people awake; but these devices are not to be universally recommended.
The heavy meal of a student may well come at evening. It should consist of a varied assortment of foods with some liquids, preferably clear soup, milk and water. Meat also forms a substantial part of this meal, though ordinarily it should not be taken more than once a day. Much is heard nowadays about the dangers of excessive meat-eating and the objections are well-founded in the case of brain-workers. The undesirable effects are "an unprofitable spurring of the metabolism— more particularly objectionable in warm weather—and the menace of auto-intoxication." Too much protein, found in meat, lays a burden upon the liver and kidneys and when the burden is too great, wastes, which cannot be taken care of, gather and poison the blood, giving rise to that feeling of being "tired all over" which is so inimical to mental and physical exertion. When meat is eaten, care should be taken to choose right kinds. "Some kinds of meat are well known to occasion indigestion. Pork and veal are particularly feared. While we may not know the reason why these foods so often disagree with people, it seems probable that texture is an important consideration. In both these meats the fibre is fine, and fat is intimately mingled with the lean. A close blending of fat with nitrogenous matter appears to give a fabric which is hard to digest. The same principle is illustrated by fat-soaked fried foods. Under the cover of the fat, thorough-going bacterial decomposition of the proteins may be accomplished with the final release of highly poisonous products. Attacks of acute indigestion resulting from this cause are much like the so-called ptomaine poisoning."
Much of the benefit of meat may be secured from other foods. Fat, for example, may be obtained from milk and butter freed from the objectionable qualities of the meat-fibre. In this connection it is important to call attention to the use of fried fat. Avoid fat that is mixed with starch particles in such foods as fried potatoes and pie-crust.
The conditions during meals should always be as pleasant as possible. This refers both to physical surroundings and mental condition. "The processes occurring in the alimentary canal are greatly subject to influences radiating from the brain. It is especially striking that both the movements of the stomach and the secretion of the gastric juice may be inhibited as a result of disturbing circumstances. Intestinal movements may be modified in similar fashion."
"Cannon has collected various instances of the suspension of digestion in consequence of disagreeable experiences, and it would be easy for almost anyone to add to his list. He tells us, for example, of the case of a woman whose stomach was emptied under the direction of a specialist in order to ascertain the degree of digestion undergone by a prescribed breakfast. The dinner of the night before was recovered and was found almost unaltered. Inquiry led to the fact that the woman had passed a night of intense agitation as the result of misconduct on the part of her husband. People who are seasick some hours after a meal vomit undigested food. Apprehension of being sick has probably inhibited the gastric activities.
"Just as a single occasion of painful emotion may lead to a passing digestive disturbance, so continued mental depression, worry, or grief may permanently impair the working of the (alimentary) tract and undermine the vigor and capacity of the sufferer. Homesickness is not to be regarded lightly as a cause of malnutrition. Companionship is a powerful promoter of assimilation. The attractive serving of food, a pleasant room, and good ventilation are of high importance. The lack of these, so commonly faced by the lonely student or the young man making a start in a strange city, may be to some extent counteracted by the cultivation of optimism and the mental discipline which makes it possible to detach one's self from sordid surroundings."
Almost as important as eating is drinking, for liquids constitute the "largest item in the income" of the body. Free drinking is recommended by physiologists, the beneficial results being, "the avoidance of constipation, and the promotion of the elimination of dissolved waste by the kidneys and possibly the liver." In regard to the use of water with meals, a point upon which emphatic cautions were formerly offered, recent experiments have failed to show any bad effects from this, and the advice is now given to drink "all the water that one chooses with meals." Caution should be observed, however, about introducing hot and cold liquids into the stomach in quick succession.