Nutrition and Resistance to Infection

Abstract

Summary The influence of diets, quantitatively or qualitatively deficient in protein, on the bactericidal and phagocytic properties of the peritoneal fluid of rats was studied. The effects of various degrees of quantitative protein deficiency were tested on rats which were kept for 4 weeks on diets containing 18, 9, 6 and 3 per cent casein, respectively. In states of moderate protein deficiency (9 per cent and 6 per cent casein) a marked diminution of the bactericidal power of the peritoneal fluid was demonstrated. In states of severe protein deficiency (3 per cent casein) a significant decrease of phagocytic activity was observed as well. For testing the quality of protein from different sources, diets containing 9 per cent of protein, derived from egg, meat, processed soybean, peanut and maize, were employed. Diets containing 9 per cent egg and meat proteins elicited bactericidal and phagocytic activity roughly equal to that elicited by a diet containing 18 per cent casein; 9 per cent soybean protein had an effect similar to that of 9 per cent casein, and 9 per cent maize protein similar to 3 per cent casein. The results obtained, however, from a diet containing peanut protein were different. Rats, which were fed a diet containing 9 per cent of this protein showed an almost complete breakdown of phagocytic activity, whereas their bactericidal power was similar to that of rats fed a 6 per cent casein diet. It is concluded: It is concluded: a) the humoral defense mechanism appears to be more sensitive to protein deficiency than the cellular defense mechanism; b) different food proteins elicit different bactericidic and phagocytic powers. This quality of promoting antibacterial defense corresponds roughly to the growth promoting quality of the respective proteins.