The Importance of the Various Foodstuffs, and the Quantities which Should be Used.
IF man and beast are to live and thrive, they must take unto themselves the same substances as those of which they are composed. Here, as so often in the study of dietetics, we see the rule proven, that like consists of like, at least in so far as the fundamental constituents are concerned. I might say that man is what he eats, or that he eats that which he is. The most important basic substances of which man and beast are composed are nitrogen, carbohydrates, and fats, and it must be our chief concern to take in these, together with the two other important constituents, the drinking-water and the nutritive salts. The same is true of plants, for they are fully as much living creatures as animals and mankind; they live in accordance with physiological laws very similar to ours, and suffer, in a general way, from the same pathological processes. They have, however, an advantage in their mode of nourishment in the fact that they can acquire the greater part of their food without any help from the outside. Mother Nature gives to them the nitrogen from the air, which they take up with their roots, through the aid of bacteria; the carbohydrates they also obtain from the air with the help of the sun’s rays; the nutritive salts they draw out from the earth through the assistance of the rain. In order, however, that the most useful of these plants which contain the greatest amount of nourishing sub-stances, and which are best adapted for our food, should rightly flourish, we lend a hand, and give them, in accordance. with the suggestion of the great Justus v. Liebig, nitrogen and nutrient salts in the form of fertilizing agents.
These, then, exert a powerful influence : the nitrogen greatly furthers the growth of the plants. Indeed, it acts in the same way upon man, and when we wish to activate the growth of children we must give them food containing plenty or, at all events, sufficient nitrogen.
It appears that nitrogen stands in such relation to growth that, as we have already made clear, a plentiful intake thereof acts upon those organs which influence the growth, viz., the thyroid and the sexual glands. Man keeps on growing until these organs are fully developed and ready for work, but then growth ceases.
All of the albumin which we have taken up to this time has been useful in promoting our growth. This is also the period in which we should not deal too sparingly with the albumin, since it is required for the formation of new tissues. When, however, the full sexual development has been attained, so generous a supply of albumin is no longer needed. Except in certain conditions the adult man cannot store up albumin. On the other hand, a plentiful intake of albumin greatly stimulates the metabolic processes, for, according to Rubner, albumin particularly enhances the oxidation processes; the expenditure of energy is also increased.
Albumin thus exerts a powerful action upon the fire that burns within us; for it is no doubt permissible to compare our bodies with a furnace, in which burns an everlasting fire like that upon the altar of the goddess Vesta, and when this fire is quenched it means death for us, just as it did for the vestal virgin who allowed the fire to die out upon the altar of the goddess. Without this continuous process of combustion life is impossible. And when a machine, as represented by our bodies, is constantly fired, it must work. In the coals which we lay upon the fire the burning power of the sun is stored up which millions of years ago streamed down perennially upon the vegetation, and the same is true of the carbohydrate contents of the plants which we consume. The stored-up motive power is now transformed into work. The heat engendered in this furnace by the combustion of the food can be measured in units, which we designate as calories. By a calorie we mean the amount of heat needed to heat 1 liter of water 1 ° C. According to Rubner, the process of combustion yields with
1 gram of albumin 4.1 calories. 1 gram of carbohydrate 4.1 calories. 1 gram of fat 9.3 calories.
For his adequate nutrition a man requires, according to von Noorden, per kilo of body weight
30 to 34 calories, in repose. 34 to 40 calories, performing light work. 40 to 45 calories, performing moderate work. 45 to 60 calories, performing hard work.
Now, although, according to Rubner, the various foods containing the same number of calories have the same nutritive value, yet their action in our economy is such that an albuminous food cannot be replaced by the same amount of calories of carbohydrates. Upon albumin alone a man could live, providing he could digest, for a greater length of time, the enormous quantity of albumin necessary to cover the colorie demands of the system, but not upon carbohydrates and fats without any albumin, even when they are taken in large quantities. This has been demonstrated by the experiments of Munk, Rosenheim, and Laegerroos, who gave their experimental animals the enormous quantity of 89 to 110 calories per kilo of body weight, and, yet, could not keep them alive. Albumin is absolutely indispensable for our nourishment, as our most important fluids, blood, lymph, digestive fluids etc. contain large amounts of it. Even in the adult, compounds of this sort are lost during every hour and every minute of the life process in carrying out the various functions, and it is impossible to replace them in any other way than by the ingestion of albumin. This may be supplied in the form of albumin either of vegetable or animal origin. The preference, however, should, in certain proportions, be accorded to the animal albumin, for reasons which we shall set forth later. It might here be mentioned, though, that the animal albumin is much more easily digested and assimilated in the form in which it occurs in meat, eggs, cheese, and milk than that contained in plants, which, owing to the presence of an indigestible woody covering, often resists the action of the digestive fluids. Very often the stomach and intestines have a difficult task to perform in supplying us with the same quantity of albumin from vegetable foods. For an adult, too great an amount of albumin is certainly not indicated, since it greatly increases the processes of metabolism. The growing individual is able to assimliate the albumin, but the adult can only do so in exceptional circumstances, such as starvation, sickness, loss of blood in women after pregnancy, etc. Otherwise, he can do nothing with it, and must burn it up, thus overloading his metabolism with the ensuing residue, and possibly injuring his most important detoxicating and secreting organs. Carbohydrats and fat can be stored up by adults, but, as has just been said, albumin, in general cannot. This would indicate the necessity of avoiding too great an amount of albuminous food, i.e., more than is required in ordinary daily life. That nature has not intended us for such food is perhaps shown by the fact that woman’s milk is comparatively poor in albumin. It contains only 2 per cent. of it, together with 6.4 per cent. of sugar and 4 per cent. of fat.
Only in work requiring a great expenditure of energy is a large amount of albumin necessary, a fact we shall dwell upon later at greater length.
Authors differ as to the quantity of albumin which we should take daily. It was Voit who taught, as the result of his famous metabolism experiments, that 118 grams of albumin were necessary in twenty-four hours. However, in 1887 Voit published the result of some observations upon the diet of a vegetarian whose twenty-four-hour albumin ration amounted to but 52 grams, yet Voit failed to mention that these observations did not harmonize with his dictum in reference to the necessity of 118 grams of albumin. Then followed independently experiments by Hirschfeld, a second contribution by Voit, and one each by Kumagawa, Klemperer, and P.eschel, all of which tended to show that one might considerably deviate from the figures of Voit. Unfortunately, however, these experiments extended only over a few days of time. The work of the aforementioned men was now followed by the experiments of Breisacher which were the first to prove conclusively that for a greater length of time, thirty-three days, the albumin ration could be materially reduced below the Voit figures without producing any deleterious effects upon the general nutrition. A number of years later Chittenden took up this subject and, upon numerous individuals, duplicated the experimental results achieved by Breisacher in his thirty-three days’ experiment made upon himself. Chittenden found, in experimenting with a number of students in American universities, that they did well and remained perfectly healthy for several months with 45 grams and were able to achieve good results in athletic sports of various sorts. Notwithstanding these facts, I would not advise the use of such a minimal quantity of albumin, for these figures prove merely that these otherwise healthy young men, stimulated by enthusiasm, were well and able to work for a certain length of time with quite a limited amount of calorie-supplying material. They show also to what an extreme point the absence of albumin can be carried when necessity demands it, without at once causing illness. When, however, I look at the pictures of these young men in Chittenden’s report, and see that, in the majority of instances, their ribs appear to stand out much too prominently, I cannot recommend such a method of diet as a rational one. From the English and American standpoint of beauty, to be sure, any tendency to fat is unesthetic and ugly, and many consider it an evidence of unsound health ; a thoroughbred race horse is thin and is able to run wellit is also healthy. But personally I prefer a little lard in animals and a little fat in man, for it forms a sort of “savings fund” for the body in times of need. What is a man subjected to such a “minimum” of food intake to do when he falls ill, and has no fat to offer to a devastating fever, while at the same time he is not able to take any nourishment? When a State has in its coffers only that amount of money which is barely sufficient to meet the current expenses, it will soon become bankrupt; for our bodies such a long-continued deficit in régime also means certain bankruptcy, an eventuality which we must try to forestall by all the means at our disposal. The figures of Voit and Chittenden may be regarded as the two extremes, and, taking into consideration the influence of individual circumstances, the nervous system, the temperament, the climate, race, established habits, etc., it would be really impossible to specify any definite amount. It would be best to accept the figure intermediate between the two extremessay, 75 gramsas an average ration of albumin. If Chittenden’s men held out with so much less, it was because of training. Our tissues have a wonderful capacity for adaptation, which must be made good use of daily; otherwise, we would soon come to grief in the strife for our existence. The fact that the digestive fluids, as Pawlow has so beautifully demonstrated, are differently secreted according to the kinds of food we are taking is an example of this adaptability. I can, with training, manage with very little food; at first I would lose in weight, but this would soon cease. That it is possible to train one’s self to go hungry has been shown by Succi and others, who at the same time remained quite well. Chittenden’s subjects also at first lost all that they could bear in weight, but then the loss came to a standstill ; when I see their photographs, however, I notice that they were by no means “fleshy.” As I have stated in my book on “Old Age Deferred,” I found, in experimenting upon myself, that for two months I felt very well and did not lose in weight while taking 70 grams of albumin and 2300 calories per day. I drank a great deal of milk. When but little albumin is taken in with the food it is necessary to ingest all the more carbohydrates and fat.
Gelatin, a substance closely related to albumin, is nevertheless not a substitute for the latter. It serves as a “sparer,” however, as do also the carbohydrates. It is obtained by the boiling of connective tissues or of cellulose.
The carbohydrates play an important part in our food as economizers of the albumin, and as such they are of much greater importance than the fats. The experiments of Pettenkofer and Voit, Fik, and Wislicenus have shown that the carbohydrates are the first in importance among the food substances for the furtherance of muscular work. We shall have more to say upon this subject in the chapter upon the increase of muscular force by specially adapted food. Fat, on the other hand, is of great importance in the formation of body heat. When it is very cold, much more fat is used up, as was shown by the labors of Voit and Duke Karl Theodor of Bavaria. With fatty food more combustion units are also, introduced. We shall speak of the fats later. Both the carbohydrates and fats must be taken in larger quantities when the supply of albumin furnished is small, especially if extra work is to be performed and in a cold climate or in winter weather.