Critical Aspects

Whilst the facts I have just detailed are incontrovertible, and form in themselves a powerful argument for moderation in eating and drinking, there are not wanting critics who assert that the experiment was not continued for a sufficient length of time, and who even place quite a different interpretation upon the results. It should be noted that in every case without exception there was an initial fall of body weight to a fixed point, at which it remained stationary, and it is pointed out that if one is satisfied with such a diminution of the weight and with a lessened heat production, economy is quite possible in the diet. This, of course, admits that the standard diet based upon custom is really in excess of the bodily requirements. But now that food supplies and clothing are so easily obtained, fat is not so necessary as a reserve store for the production of heat and energy. It is also asserted that protein may be diminished greatly if taken along with carbohydrates and fat, because the last two act as "protein sparers." Although at all times the tissue cells seize upon protein in preference to any other nutrient, this statement is diametrically opposed to the views held by Folin, who contends that the greater part of the protein is metabolised with the sole object of obtaining its carbonaceous molecule. It is also pointed out that a vegetarian diet with protein and carbohydrates intimately mixed, so that they reach the tissues at the same time, is one that lends itself to the maintenance of nitrogen equilibrium on a relatively small amount of protein.

On the plea that in such matters Nature is far and away the best guide, attempts have been made by instituting a comparison between the diet at a time before artificial dietetic habits have been formed and there has been any stimulation of the appetite, viz., the proportionate ingredients of a suckling infant's food and those of the food when the full period of growth had been attained, i.e., presumably after fixed dietetic habits had been established, and by this means establishing a fixed standard for guidance throughout life. It has been computed, for example, by one method of calculation, that as an infant of six months old only consumes 14 grams of protein daily, on the same basis an adult should only require about 70 grams, which is practically what Chittenden contends. Comparisons of this nature, however, lack impressiveness, because an infant seven days old and weighing 8 1/2 pounds consumes 400 grams of breast-milk daily, yielding 8 grams of protein. This is equal to 2 07 grams per kilo of body-weight, an amount hopelessly in excess of Chittenden's standard. Without making any effort to reconcile those figures, it is obvious that the protein requirements of the infant and growing child must be proportionately greater than those of the adult, because the latter only needs protein to supply the natural waste of tissue and losses by the secretions, while the former demands in addition an extra quantity to build up the developing tissues. As if to make confusion worse confounded, Rubner, strange as it may appear, has in recent years entered the lists as a champion of the doctrine of a low-protein diet for infants. He states that "in the maintenance diet of suckling infants only 5 per cent. of the calories are derived from protein, 95 per cent. being furnished by fat and carbohydrates," and that if a food equally as suitable as milk were available for adults it would be quite possible for them to live comfortably on equally small quantities of protein, suggesting 31.4 grams as the limit. I do not pretend to explain doctrines apparently so irreconcilable, but consider them worthy of mention as betokening the remarkable interest which has been aroused on the subject.

Benedict's Views

The most critical examination of the low-protein theory is that published by Dr. Francis G. Benedict. He categorises Chittenden's dietetic study on himself as the most remarkable on record, and declares that "nowhere in the literature of nutrition do we find an experiment so painstaking and accurate, covering so long a period," viz., two years - and I can personally vouch for the fact that he subsists on a similar diet to-day - " and with a diet of so low a protein-content following a normal diet." It has been justly cited as a "monument of fidelity." Whilst, however, agreeing with the accuracy of his data, and praising him in no unstinted terms as a faithful student of nutrition, he is inclined to doubt his deductions, and hints that mental suggestion may have had much to do with the good results obtained. He considers also that much of the benefit to the health was due to the regular life and unique form of social communion in vogue, and asserts that the daily supervision of Dr. W. G. Anderson, the well-known Director of the Yale Gymnasium, could not fail to be an important factor in the experiment.

He wonders whether the abnormally low protein did not occasion some disturbance of the alimentary tract, affecting its power of absorbing either the protein of the food or the nitrogenous materials from which the so-called metabolic products are derived, such as is said to occur in animals under similar circumstances, although this is hardly in agreement with his own statement previously referred to, that protein in common with the other alimentary principles is absorbed in proportion to the amount which has been ingested. His speculation on this point has been in great measure answered by Chittenden's most recent lengthy observations on six men varying in age from 21 to 29 years, and in weight from 51 to 70 kilograms. These subjects had absolute freedom of choice in their diet, except as regards meat, which was somewhat restricted, and were found to have an average daily intake of 75 grams protein, as contrasted with the Voit standard daily intake of 118 grams, and a daily consumption of 8-9 grains of metabolised nitrogen in place of the 16 grams in Voit's scale. The most careful examination was made to discover whether the lowered intake of protein food had produced any recognisable metabolic changes, but the results were entirely negative in character. As a relatively large amount of fat was consumed, the conditions were favourable for showing even a slight impairment of the digestive functions, but even although the diet necessarily contained a large proportion of vegetable matter, the utilisation both of nitrogen and fat was quite up to the standard in healthy individuals. Not only so, but as the experiment progressed the utilisation of nitrogen and fat showed a tendency to increase rather than decrease. The observations were continued for 130 days, and during this time the utilisation of nitrogen varied from 88 to 90, that of fat 97-98 per cent., while all the subjects showed continuously a plus nitrogen balance, irrefutable evidence that the daily protein consumption was quite adequate to meet the needs of the body. Besides this, a gain of weight, varying between a quarter of a pound and 6 pounds, was displayed by all the subjects, and the men were noted to be in better general condition at the conclusion of the test than they were at the beginning.