200. Protein And Health

The arguments in favor of a restricted consumption of protein are based chiefly on the benefits to health. It is urged that as all protein wastes, of whatever kind, must be eliminated through the kidneys, a generous protein consumption places a heavy burden upon these organs at which they are said to rebel, and there occurs an accumulation of nitrogen wastes in the organism that is dangerous to health. Rheumatism and gout have been regarded as related to uric acid accumulation, and nitrogenous bodies are believed to often cause "auto-intoxication," bringing on biliousness and low forms of fever. Unquestionably much physical suffering and disability arises in these and other ways from the excessive consumption of protein foods, especially meats. The question turns on what is excessive. Are the dietary standards excessive? Dr. Chittenden claims for himself and the other subjects with whom he experimented that a material reduction of the protein intake resulted in a betterment of condition both physical and mental. There is also much popular testimony to the same effect, although the most of this relates to the total food consumption rather than to the mere diminution of the protein intake.

201. Arguments Against Minimum Protein Supply

But students of human nutrition do not all agree that so radical a diminution of protein in the food is desirable. In the first place, there is some reason for believing that protein serves the mature animal organism in other ways than merely repairing tissue waste, and that the physi-ologioal needs are less efficiently served when the protein supply is held down to the minimum that just makes good the unavoidable protein destruction. General facts of observation and experience are cited. It is held to be significant that the communities holding leading positions in the world consume a liberal quantity of protein, or, conversely, that communities with an inferior physical and mental status use a low proportion of protein in the diet. We certainly cannot ignore the facts of long continued experience. It is asserted with great force, that we do not know what would be the effect of a low protein diet if continued through many generations. We do know that people of great physical strength have developed and lived in whose diet animal foods occupied a prominent place. If we argue from analogies in feeding farm animals, - and physically man is an animal, - generous protein feeding is desirable for the growth and maintenance of vigorous organisms and a satisfactory rate of production. It is regarded as significant by one critic of Dr. Chittenden that all the athletes used in his tests returned to practically their former diet, which they would hardly have been allowed to do if the low protein diet had been found to be so greatly superior. The question is a complex one, and is by no means settled. Certainly no facts appear which show with any conclusiveness that the dietary standard of 118 grams of protein per day for a moderately active person of average size may not be followed with safety and advantage to health and vigor.

Note.

It is probable that the source of protein has much to do with the efficiency of a given quantity, especially when the purposes of growth must be served. Since paragraph 159, p. 152, Chap. VII, was written Osborne and Mendel have published the results of extensive studies on the efficiency of individual proteins. The experimental animals used were albino rats, the technique and control being such as to inspire confidence in the data secured. The authors call attention to the fact that gelatin has lone been known as a protein inadequate of itself for sustaining life. Other individual proteins can now be studied. Observations were made with rations containing the following proteins: casein, lactalbumin, glycinin, excelsin, legumin, edestin, glutenin, gliadin, zein, hordein, and perhaps others. It was concluded that in the earlier experiments the failure to produce growth or even to permanently maintain life, where the artificial food mixture contained only a single protein, was due to the inadequacy of the mixture of non-protein compounds and inorganic salts accompanying the protein. Later experiments where the single proteins were fed with protein-free milk (casein and lactalbumin removed) showed that adequate growth was secured with casein, lactalbumin, egg albumin, edestin, glutenin, and glycinin. Growth was not secured but life was maintained when the following proteins were fed with protein-free milk: gliadin of wheat, and hordein of barley, while zein from corn proved to be insufficient for the maintenance requirement. It is hardly to be expected that these results would have any significance as related to ordinary dietaries that are made up of a mixture of animal and vegetable foods. It seems possible, however, that the development of the human body may be modified when the diet is largely of one material such as rice or corn. As a side issue, the authors point to the fact that the synthesis of conjugated proteins (nucleo proteins, haemoglobin) from simple proteins and inorganic salts must have taken place.

1Science, 1911, pp. 722-732.