I. EXPERIMENTS WITH PROFESSIONAL MEN.
Before proceeding with a detailed account of the experimental work, it may be well again to emphasize that what is especially desired is to ascertain how far, if any, the intake of proteid food can be diminished without detriment to the body,i. e., with maintenance of nitrogen and body equilibrium and without impairment of bodily and mental vigor. Further, if a lower proteid standard than that generally adopted can be established, it is desirable to ascertain whether it can be maintained indefinitely, or for a long period of time, without loss of strength and vigor. Obviously, it is of primary importance that we should know quite definitely what the minimal proteid requirement of the healthy man per kilo of body-weight really is, and the experimental work about to be detailed has aimed especially to determine whether it is possible to materially lower the amount of daily proteid food, without detriment to the bodily health and with maintenance of physical and mental vigor.
The writer, fully impressed with his responsibility in the conduct of an experiment of this kind, began with himself in November, 1902. At that time he weighed 65 kilos, was nearly 47 years of age, and accustomed to eating daily an amount of food approximately equal to the so-called dietary standards. Recognizing that the habits of a lifetime should not be too suddenly changed, a gradual reduction was made in the amount of proteid or albuminous food taken each day. In the writer’s case, this resulted in the course of a month or two in the complete abolition of breakfast, except for a small cup of coffee. A light lunch was taken at 1.30P. M., followed by a heavier dinner at 6.30P. M.Occasionally, however, the heartier meal was taken at noontime, as the appetite suggested. It should be added that the total intake of food was gradually diminished, as well as the proteid constituents. There was no change, however, to a vegetable diet, but a simple introduction of physiological economy. Still, there was and is now a distinct tendency toward the exclusion of meat in some measure,the appetite not calling for this form of food in the same degree as formerly. At first, this change to a smaller amount of food daily was attended with some discomfort, but this soon passed away, and the writer’s interest in the subject was augmented by the discovery that he was unquestionably in improved physical condition. A rheumatic trouble in the knee joint, which had persisted for a year and a half and which only partially responded to treatment, entirely disappeared (and has never recurred since). Minor troubles, such as “sick headaches” and bilious attacks, no longer appeared periodically as before. There was greater appreciation of such food as was eaten; a keener appetite and a more acute taste seemed to be developed, with a more thorough liking for simple foods. By June, 1903, the body-weight had fallen to 58 kilos.
During the summer the same simple diet was persisted in—a small cup of coffee for breakfast, a fairly substantial dinner at midday and a light supper at night. Two months were spent in Maine at an inland fishing resort, and during a part of this time a guide was dispensed with and the boat rowed by the writer frequently six to ten miles in a forenoon, sometimes against head winds (without breakfast), and with much greater freedom from fatigue and muscular soreness than in previous years on a fuller dietary. The test of endurance and fitness for physical work which the writer thus carried out “on an empty stomach” tended to strengthen the opinion that it is a mistake to assume the necessity for a hearty meal because heavy work is about to be done. It is certainly far more rational from a physiological standpoint to leave the hearty meal until the day’s work is accomplished. We seemingly forget that the energy of muscular contraction comes not from the food-stuffs present at the time in the stomach and intestinal tract, but rather from the absorbed material stored up in the muscles and which was digested and absorbed a day or two before. Further, it is to be remembered that the very process of digestion draws to the gastro-intestinal tract a large supply of blood, and that a large amount of energy is needed for the processes of secretion, digestion, absorption, andperistalsis, which are of necessity incited by the presence of food in the stomach and intestine, thereby actually diminishing the amount of energy available at the place where it is most needed. Why, then, draw upon the resources of the body just at a time, or slightly prior to the time, when the work we desire to perform, either muscular or mental, calls for a copious blood supply in muscle or brain, and when all available energy is needed for the task that is to be accomplished?
We are too wont to compare the working body with a machine, the boiler, engine, etc., overlooking the fact that the animal mechanism differs from the machine in at least one important respect. When we desire to set machinery in operation we must get up steam, and so a fire is started under the boiler and steam is generated in proportion as fuel is burned. The source of the energy made use of in moving the machinery is the extraneous combustible material introduced into the fire-box, but the energy of muscular contraction, for example, comes not from the oxidizable food material in the stomach, but from the material of the muscle itself. In other words, in the animal body it is a part of the tissue framework, or material that is closely incorporated with the framework, that is burned up, and the ability to endure continued muscular strain depends upon the nutritive condition of the muscles involved, and not upon the amount of food contained in, or introduced into, the stomach. All physiologists will, I think, acknowledge the soundness of this reasoning, but how few of us apply the principle in practice. It is perfectly logical to begin the work of the day with a comparatively empty stomach,—after we have once freed ourselves from the habit of a hearty breakfast,—and in the writer’s experience both mental and physical work have become the easier from this change of habit. The muscle and the brain are given opportunity to repair the waste they have undergone, by the taking of food at times when the digestive processes will not draw upon the energy that in activity is needed elsewhere.
Further, it is easy to understand why on a restricted diet, especially of proteid foods, there should be a diminished senseof fatigue in connection with vigorous or continued muscular work, and why at the same time there should be an increased power of endurance, with actual increase of strength. With a diminished intake of proteid food there is a decreased formation of crystalline nitrogenous waste products, such as uric acid and the purin bases, to say nothing of other bodies less fully known, which circulating through the system are undoubtedly responsible, in part at least, for what we term fatigue. We need not consider here whether the sense of fatigue is due to an action of these substances upon the muscles themselves, upon the motor nerves or their end-plates, or upon the central nervous system; it is enough for the present purpose to emphasize the probable results of their presence in undue amount. Lastly, we may emphasize what is pretty clearly evident to-day, viz., that the energy of muscular contraction comes preferably from the oxidation, not of the nitrogenous or proteid constituents of the muscles, but of the non-nitrogenous components of the tissue; another reason why excess of proteid food may be advantageously avoided. Moreover, proteid food stimulates body metabolism in general, and hence undue amounts of proteid in the diet augment unnecessarily the metabolism or combustion of the non-nitrogenous material of the muscle, thereby destroying what would otherwise be preserved as a source of energy in muscular contraction, when the muscles are called upon for the performance of their daily functions.
On the writer’s return to New Haven in the fall of 1903, he was surprised to find that his body-weight was practically the same as early in July. In the period between November, 1902, and July, 1903, the body had lost 8 kilos under the gradual change of diet, but from July to October, 1903, the weight had apparently remained stationary, from which it might fairly be assumed that the body had finally adjusted itself to the new conditions.
What now was the condition of the body as regards nitrogen metabolism? To answer this question the entire twenty-four hours’ urine was collected practically every day, fromOctober 13, 1903, to June 28, 1904, representing a period of nearly nine months. This daily output through the kidneys was analyzed each day with special reference to the total nitrogen,[31]as a measure of the amount of proteid material metabolized. Total volume of the urine, specific gravity, uric acid, phosphoric acid, indican, and other points were also considered, the more important results being indicated in the following tables.
Scrutiny of the tables shows that during this period of nine months the body-weight was practically constant. The daily volume of urine was exceptionally small and fairly regular in amount, the average daily output for the nine months being 468 c.c. It is a noticeable fact that with a diminished intake of proteid food there is far less thirst, and consequently a greatly decreased demand for water or other fluids. Further, in view of the small nitrogenous waste there is no need on the part of the body for any large amount of fluid to flush out the kidneys. The writer has not had a turbid urine during the nine months’ period. With heavier eating of nitrogenous foods, an abundant water supply is a necessity to prevent the kidneys from becoming clogged, thereby explaining the frequent beneficial results of the copious libations of mineralwaters, spring waters, etc., frequently called for after, or with, heavy eating. Obviously, a small volume of urine each day means so much less wear and tear of the delicate mechanism of the kidneys. Somewhat noticeable, in a general way, is the apparent relationship between the volume of the urine and the nitrogen output, in harmony with the well-known diuretic action of urea. The specific gravity of the urine shows variation only within narrow limits, the daily average for the nine months being 1027.
Uric acid is noticeably small in quantity, the average daily output for the nine months’ period, based upon the determinations made, being only 0.392 gram.
Chief interest, however, centres around the figures for total nitrogen, since these figures give for each day the extent of the proteid metabolism;i. e., the amount of proteid material broken down in the body each day in connection with the wear and tear of the bodily machinery. To fully grasp the significance of these data, it should be remembered that the prevalent dietary standards are based upon the assumption that the average adult must metabolize each day at least 16 grams of nitrogen. Indeed, that is what actual analysis of the urine indicates in most cases. If now we look carefully through the figures shown in the above tables, covering a period from October 13, 1903, to June 28, 1904, it is seen that the daily nitrogen excretion is far different from 16 grams. Indeed, the figures for nitrogen are exceedingly low, and, moreover, they vary little from day to day. The average daily output of nitrogen through the urine for the entire period of nearly nine months is only 5.699 grams.
For the first six months the average daily excretion amounted to 5.82 grams of nitrogen, while from April 12 to June 28 the average daily excretion of nitrogen was 5.40 grams, thus showing a slight tendency downward. On the whole, however, there is shown a somewhat remarkable uniformity in the daily excretion. Thus, the average daily excretion for the month of November was 5.79 grams of nitrogen, for the month of March 5.66 grams, thus showing very littledifference in the output of nitrogen through the kidneys in these two periods, three months apart. In other words, the extent of proteid katabolism was essentially the same throughout the entire nine months, implying that the amount of proteid food eaten must have been fairly constant, and that the body had adapted itself to this new level of nutrition from which there was no tendency to deviate. There was no weighing out of food and no attempt to follow any specified diet. The greatest possible variety of simple foods was indulged in, and the dictates of the appetite were followed with the single precaution that excess was avoided. In other words, it was temperance in diet, and not prohibition. Yet it is equally true, in the writer’s case at least, that the appetite itself unconsciously served as a regulator, since there was, as a rule, no necessity to hold the appetite in check to avoid excess. Doubtless, the writer’s knowledge of the general composition of food-stuffs has had some influence in the choice of foods, and thereby aided in bringing about this somewhat remarkable uniformity in the daily output of nitrogen for such a long period of time on an unrestricted diet.
What now do the nitrogen figures show regarding the amount of proteid material metabolized each day? It will be remembered that the Voit standard calls for 118 grams of proteid or albuminous food daily, of which 105 grams should be absorbable, in order to maintain the body in a condition of nitrogen equilibrium, and in a state of physical vigor and general tone. This would mean a daily excretion through the urine of at least 16 grams of nitrogen. The daily output of nitrogen in the case under discussion, however, was 5.699 grams for a period of nearly nine months. This amount of nitrogen excreted through the urine means only 35.6 grams of proteid metabolized, or about one-third the amount called for by the Voit standard, or the standards generally adopted as expressing man’s daily requirement of proteid food. But was the body in nitrogenous equilibrium on this small amount of proteid food? Naturally, this question might be answered in the affirmative, on the basis of the constancy in body-weightfor the period from October to June, but more decisive proof is needed. The question was therefore settled by a careful comparison of the income and output, in which all the food eaten was carefully weighed and analyzed, while the nitrogen of the urine and fæces was determined with equal accuracy. The first experiment of this character to be quoted is for the week commencing March 20, a period of six days.
Following are the diets made use of each day, the weights of the various food-stuffs being given in grams. Likewise is shown the nitrogen content of the several food-stuffs for each day, and also a comparison of the nitrogen intake with the output of nitrogen through the urine:
Sunday, March 20, 1904.
Breakfast, 7.45A. M.—One cup coffee,i. e., coffee 137.5 grams, cream 30.5 grams, sugar 9 grams.
Dinner, 1.30P. M.—Stewed chicken 50 grams, mashed potato 131 grams, biscuit 49 grams, butter 13 grams, chocolate pudding 106 grams, one small cup coffee,i. e., coffee 64 grams, sugar 12 grams, cheese crackers 29 grams.
Supper, 6.30P. M.—Lettuce sandwiches 56 grams, biscuit 35 grams, butter 6 grams, one cup tea,i. e., tea 170 grams, sugar 7 grams, sponge cake 47 grams, sliced oranges 82 grams.
Monday, March 21, 1904.
Breakfast, 7.45A. M.—Coffee 119 grams, cream 30 grams, sugar 9 grams.
Lunch, 1.30P. M.—One shredded wheat biscuit 31 grams, cream 116 grams, wheat gems 33 grams, butter 7 grams, tea 185 grams, sugar 10 grams, cream cake 53 grams.
Dinner, 6.30P. M.—Pea soup 114 grams, lamb chop 24 grams, boiled sweet potato 47 grams, wheat gems 76 grams, butter 13 grams, cream cake 52 grams, coffee 61 grams, sugar 10 grams, cheese crackers 16 grams.
Tuesday, March 22, 1904.
Breakfast, 7.45A. M.—Coffee 97 grams, cream 26 grams, sugar 9 grams.
Lunch, 1.30P. M.—Baked potato 83 grams, fried sausage 36 grams, soda biscuit 39 grams, butter 12 grams, tea 137 grams, sugar 10 grams, cream meringue 59 grams.
Dinner, 6.30P. M.—Chicken broth 146 grams, bread 52 grams, butter 15 grams, creamed potato 76 grams, custard 76 grams, coffee 50 grams, sugar 11 grams, cheese crackers 10 grams.
Wednesday, March 23, 1904.
Breakfast, 7.45A. M.—Coffee 103 grams, cream 30 grams, sugar 10 grams.
Lunch, 1.30P. M.—Creamed codfish 64 grams, potato balls 54 grams, biscuit 44 grams, butter 22 grams, tea 120 grams, sugar 10 grams, wheat griddle cakes 133 grams, maple syrup 108 grams.
Dinner, 6.30P. M.—Creamed potato 85 grams, biscuit 53 grams, butter 15 grams, apple-celery-lettuce salad 50 grams, apple pie 127 grams, coffee 67 grams, sugar 8 grams, cheese crackers 17 grams.