Growth on diets containing more than ninety per cent. of protein

Although it has been demonstrated that a carnivorous animal can be kept alive and maintained in activity for considerable periods on an exclusive diet of meat it is not known whether growth as well as maintenance can proceed on a regimen entirely free from both fats and carbohydrates. Hammarsten has stated that omnivora and herbivora cannot survive on such a ration. The few experiments on record in relation to this problem have without exception been conducted on a wrong plan, the food mixtures being inadequare in respect to one or more essential factors. Our successful experiences in growing rats on foods extremely poor in fats 1 and in carbohydrates 2 respectively encouraged us to test diets containing only minimal quantities of both. The mixtures included protein 95 per cent., inorganic salts 5 per cent., along with a supply of vitamins A and B in the form of tablets of alfalfa (0.4 gm.) and dried brewery yeast (0.2 gm.) daily. On such diets, when casein furnished the protein component, animals have already grown to three times their weight at the beginning of the trial. The vitamin-bearing substances were the only noteworthy sources of either fat or carbohydrate, and supplied 4-8 per cent. of the food eaten. Whether rats will attain adult size and normal function on such diets, furnishing protein as the almost exclusive source of energy and tissue substance, remains to be determined further. If future experiments prove as successful as those here described various problems of nutrition and physiological function can be approached from new experimental standpoints.