44. Rations. Recent experiments indicate that the needs of an average man would be fully met by a daily ration of 300 grams of carbohydrate, 50 grams of fat, and 50 grams of proteid.1

1 More or less variation from the above figures would of course be required to meet the needs of different ages, sexes, constitutions, and occupations. A discussion of such details cannot well be undertaken in this place. It should be said, however, that physiologists of the highest standing now admit that former estimates of the body's needs based upon records of the amount commonly consumed are too high for maximum efficiency. The standard which has been most generally adopted by American writers on nutrition calls for 125 grams of proteid, with sufficient fat and carbohydrate to yield a total of 3,500 Calories as the daily ration for a man at moderate muscular work. These figures were derived mainly from" observation of what many healthy Americans actually eat, and are admittedly but rough approximations erring rather on the side of excess than deficiency. Good health is undoubtedly maintained on such an allowance, but this, of course, is no proof that eating somewhat less would not conduce to even better health and greater vigor. A very liberal allowance would be 400 grams of carbohydrate, and 100 grams each of fat and proteid for an average man.

This gives of nitrogenous material sufficient to cover an average daily loss of about 8 grams of nitrogen, and of carbonaceous fuel enough to yield about 1,900 Calories or 805,600 kilogrammeters of energy, which has been found to be approximately the amount expended in 24 hours. If at first sight this seems to be an exaggerated estimate of the energy given out, it should be borne in mind that a very large share goes to keep up the warmth of the body; while of the remainder which is transformed into mechanical activity, a considerable proportion is used up in the muscular movements of the digestive organs, in breathing some 23,000 times, and in making more than 600,000 heart-beats, thus leaving only about one third of the whole available for locomotion and external work.

The main point which here concerns us regarding the make-up of a proper daily ration is the relative proportion of nutrients rather than their absolute amount. On the basis of the figures given, it may be stated roughly and in a general way that 1 part proteid, 1 part fat, and 6 parts carbohydrate, would ordinarily meet the daily needs of an average person, or in other words that one's food should be about 1/8 proteid, 1/8 fat and 3/4 carbohydrate. In the rations recommended it is assumed that the foods chosen are easily digestible; for it is not what we eat but what we digest that nourishes us. For students and other brain-workers digestibility is of especial importance since their largely sedentary life leaves them but little surplus energy to spare for unnecessary digestive work.

A glance at the chemical chart (Fig. 120) will show that many vegetable foods do not have their nutritive constituents in anything like the standard proportion. This means that if a man were to obtain all his nourishment from such foods, he would have to eat too much of one ingredient (generally a carbohydrate) in order to get enough of another. When it is remembered that the dry substance of meats, fish, eggs, and other such foods of animal origin, consists almost entirely of proteids and fats, we see that here also there is a similar disproportion, although in another direction. Since, however, the constituents which are deficient on the one side, are in excess on the other, a mixed diet combining animal with vegetable foods, is most likely to be well-balanced.

From this, point of view it is interesting to notice how generally the instincts of mankind have led them to prefer combinations of food wherein the components supplement each other, and thus approximate to the chemical ideal. The appropriateness of combining bread and butter we have already had occasion to notice. Similarly in "crackers and cheese," "mush and milk," "eggs on toast," "meat and potatoes," and many other favorite combinations which will readily occur to the reader, we have the animal part poor in carbohydrate and rich in fat and proteid, supplemented by a vegetable food comparatively poor in these latter ingredients, but rich in sugar or starch. Sometimes, indeed, as in "pork and beans" we may have a highly valued combination in which not only the carbohydrate but also nearly all the proteid is furnished by the vegetable part, the animal portion being little else than fat; or, as in certain salads, we may have the fat represented almost entirely by olive-oil.

Those who prefer for any reason to abstain entirely from meat or other animal food may find adequate substitutes in various seed foods of highly nitrogenous composition, as the table clearly shows, provided the greater difficulty of digesting them does not offset their advantages, as is often the case with persons of sedentary habit. The recent military triumphs of the Japanese show in a striking way what hard physical work can be done on a diet consisting in very large part of rice. In most cases, however, it will be found that the vegetable foods are of value to us chiefly as contributing carbohydrates, and thereby supplying the most marked deficiency of foods derived from animals.

We have now an answer to our question regarding the special nutritive value of vegetable as opposed to animal foods. Both, as we know, yield us building material and fuel; and either the one or the other sort of food is used almost or quite exclusively by certain races of mankind, just as by herbivorous or carnivorous animals; and, furthermore, we have seen that whatever nourishes the animal kingdom, including ourselves, must be derived ultimately from plants. Nevertheless, the teachings of chemistry and the practice of the best-fed and most vigorous peoples agree in showing that while it may be desirable for us to depend mainly upon animal food for our nitrogenous materials and carbonaceous reserve, it is to vegetable foods that we must look to supply us with energy which shall be immediately available at any moment for the work of life.