Dinner.—Vegetable soup 100 grams, potato croquette 198 grams, bread 73 grams, bacon 7 grams, string beans 120 grams, water ice 77 grams, banana 270 grams, coffee 100 grams, cream 30 grams, sugar 14 grams.
Total nitrogen content of the day’s food = 9.726 grams.
While the critic might justly say that these dietaries lack variety and would not appeal to a fastidious taste, there is force in the illustration which they afford of a simple diet being quite adequate to meet the wants of the body. Further, it should be emphasized that there is no special virtue in any of these dietaries, aside from their simplicity and low content of nitrogen. They represent individual taste and selection. Any other form of diet would answer as well, provided there was not too large an intake of proteid, and provided further the fuel value of the day’s ration was sufficient to meet the requirements for heat and work. Again, it might be said that with this latter subject the daily consumption of proteid food was considerably larger than with the first subject. This is indeed true, but it must be remembered that the second subject had a body-weight of 70 kilos during the last seven months, while the first subject weighed only 57 kilos. Obviously, with this marked difference in the weight of living tissue there must be a corresponding difference in the extent of proteid katabolism, and consequently a difference in the demand for proteid food.
As we have seen, the smaller subject for a period of many months showed a proteid katabolism equal to 0.1 gram of nitrogen, per kilo of body-weight, daily. The second and larger subject, on a totally different diet, for seven months and a half, metabolized daily, on an average, 6.53 grams of nitrogen. Taking the weight of the body at 70 kilos, it is readily seen that the nitrogen metabolized daily per kilo of body-weight was 0.093 gram, almost identical with the rate of nitrogen exchange found with the first subject. It is certainly very suggestive that these two individuals with their marked difference in body-weight, under different degrees of physical activity, and living on different forms of diet, with only the one point in common of voluntary restriction in the amount of proteid food, until a new habit had been acquired and a new level of proteid metabolism attained, should have quite independently reached exactly the same level of nitrogen exchange per kilo of body-weight. And when it is remembered that this was attained by the daily consumption of not more than one-third to one-half the minimal amount of proteid food called for by the dietetic customs of mankind, and with maintenance of all the characteristics of good health through this comparatively long period of time, there certainly seems to be justification for the opinion that the consumption of proteid food, as practised by the people of the present generation, is far in excess of the needs of the body. Referring for a moment to the calorific value of the food used by the second subject, in the last balance period, it is to be noted that the heat value per day averaged 2448 calories, as estimated on the basis of the chemical composition of the food. This would amount to 34 calories per kilo. Whether this figure is strictly correct is immaterial; it is certainly sufficiently so to warrant the statement that the needs of the body were fully met by an intake of food below the standards set by usage, and that maintenance of nitrogen equilibrium on a greatly diminished consumption of proteid food is possible without increasing the intake of non-nitrogenous matter.
Finally, as affording additional evidence, we may refer to a third subject in this group, a man of 65 kilos body-weight, 26 years of age, who for a period of six consecutive months maintained body-weight, nitrogen equilibrium, and a general condition of good health, with a proteid metabolism equal to 7.81 grams of nitrogen per day. During the last two months of the experiment, the average excretion of nitrogen per day amounted to 6.68 grams, corresponding to a metabolism of 0.102 gram of nitrogen per kilo of body-weight. This figure, it will be noted, is practically identical with the values obtained with the preceding subjects, calculated to the same unit of weight. Further, this third subject did not reduce his nitrogen intake by an exclusion of meat, but made use of his ordinary diet gradually reduced in amount. His daily consumption of proteid food averaged 55 grams, or 8.83 grams of nitrogen, and on this amount of proteid, without increasing the intake of fats and carbohydrates, he was quite able to do his work with preservation of physiological equilibrium.
Views so radically different from those commonly accepted can be made to carry weight, only by the accumulation of supporting evidence obtained under widely different conditions of life, and by methods which will defy criticism. It might be argued, and with perhaps some justification, that while professional men, with freedom from muscular work, may be able to live without detriment on a relatively small amount of proteid food, such a conclusion would not be warranted for the great majority of mankind with their necessarily greater muscular activity. We are confronted at once with the oft-heard statement that the laboring man requires more proteid food; he has a more vigorous appetite, and he must take an abundance of meat and other foods rich in proteid, if he is to maintain his ability as a worker. Note the statements already made in other connections regarding the food consumption of Maine lumbermen, of men on the football team, of trained athletes in general. These men consume large amounts of proteid daily, because their work demands it. If the demand did not really exist, they would not so agree in the use of high proteid standards, so runs the argument. The custom certainly does exist and is almost universally followed; men in training for athletic events deem it necessary to consume large amounts of proteid food. Custom and long experience sanction a high proteid diet, rich in nitrogen, for the development and maintenance of that strength and vigor that help to make the accomplished athlete. It is common knowledge to-day, however, that the energy of muscle work does not have its origin in the breaking down of proteid material, certainly not when there is an adequate amount of fat and carbohydrate in the diet. A high proteid intake must therefore be called for because of some subtle quality, not at present fully understood. It must not be subjected to criticism, however, because it is sanctioned by custom, habit, and common usage.
Still, I have ventured to experiment somewhat with a group of eight university athletes, all trained men, and with some surprising results. We have not space for details, but it may be mentioned that the men were young, from 22 to 27 years of age, and were experts in some field of athletic work. By a preliminary study of their ordinary dietetic habits, it was found that they were all large consumers of proteid food, with a corresponding high rate of proteid katabolism. One subject of 92 kilos body-weight, during ten days, showed an average daily excretion through the kidneys of 22.79 grams of nitrogen, implying a metabolism of 142 grams of proteid matter per day. On one of these days, the nitrogen excretion reached the high figure of 31.99 grams, corresponding to a metabolism of about 200 grams of proteid matter. Calculated per kilo of body-weight, this means a metabolism of 0.35 gram of nitrogen, or three and a half times the amount needed by the three professional men for the maintenance of nitrogen equilibrium. These subjects, with an intelligent comprehension of the point at issue, and with full freedom in the choice of food, gradually diminished their daily consumption of proteid material, at the same time cutting down very markedly the total consumption of food. The experiment extended through five months, and during the last two months, the average daily excretion of metabolized nitrogen of the eight men amounted to 8.81 grams per man. This corresponds to a metabolism of 55 grams of proteid matter.
Further, the average daily output of nitrogen through the kidneys during the preceding two months was in many cases nearly, if not quite, as low as during the last two months of the experiment. If we contrast this average daily exchange of 8.81 grams of nitrogen with the average output prior to the change in diet, it is easy to see that the men were living on about one-half the amount of proteid food they were formerly accustomed to take. Moreover, if the metabolized nitrogen for each individual, with one exception, is calculated per kilo of body-weight, it is seen to vary from 0.108 gram to 0.134 gram; somewhat higher than was observed with the older professional men, but not conspicuously so. Again, it is to be emphasized that the lowered intake of proteid food with these men was quite adequate to maintain their bodies in nitrogen equilibrium. We may cite a single case by way of illustration:
Output. | |||
Nitrogen in | Nitrogen through | Weight of Excre- | |
May 18 | 8.119 grams. | 5.75 grams. | . . grams. |
19 | 9.482 | 6.64 | 15 |
20 | 10.560 | 8.45 | . . |
21 | 8.992 | 8.64 | . . |
22 | 9.025 | 8.53 | . . |
23 | 8.393 | 7.69 | 89 |
24 | 7.284 | 7.34 | 24 |
| ──── | ─── | ── | |
| 128 grams contain 6.40% N. | |||
| 61.855 | 53.04 + | 8.192 grams nitrogen. | |
| ───── | ────────── | ──── | |
| 61.855 grams nitrogen. 61.232 grams nitrogen. | |||
Nitrogen balance for seven days = +0.623 gram. | |||
Nitrogen balance per day = +0.089 gram. | |||
Output. | |||
Nitrogen in | Nitrogen through | Weight of Excre- | |
May 18 | 8.119 grams. | 5.75 grams. | . . grams. |
19 | 9.482 | 6.64 | 15 |
20 | 10.560 | 8.45 | . . |
21 | 8.992 | 8.64 | . . |
22 | 9.025 | 8.53 | . . |
23 | 8.393 | 7.69 | 89 |
24 | 7.284 | 7.34 | 24 |
| ——— | —— | — | |
| 128 grams contain 6.40% N. | |||
| 61.855 | 53.04 + | 8.192 grams nitrogen. | |
| ——— | ——————— | ——— | |
| 61.855 grams nitrogen. 61.232 grams nitrogen. | |||
Nitrogen balance for seven days = +0.623 gram. | |||
Nitrogen balance per day = +0.089 gram. | |||