Relation of Salt Deficient Diets to Resistance to Infection.

Abstract

Recent experiments, notably those reported by Webster and Prit-chett, 1 have shown that diet has a decided influence on susceptibility to infection. These investigations d alt with the vitamine fraction of the diet. It seemed to us of importance to ascertain the part played by salts in the metabolic process and in host resistance to disease.

Rats were used as experimental animals and trypanosomes as the infectious agent. Rats from the same stock were kept on a synthetic diet∗ from which one or another cation was eliminated. After a certain period equal numbers of rats of approximately the same age or weight were infected with Tr. evansi, each rat receiving the same number of trypanosomes intraperitoneally. The duration of the infection was used as an index of individual resistance.

The results indicate a decreased resistance in the rats on a salt deficient diet as compared with those maintained on a full or standard diet. A summary of the results obtained is shown in Table I.

It is evident that elimination of any of the important salts causes a reduction in resistance, the average survival time being 20-30% less than on a full diet. The rats fed diets poor in salt remain dwarfed, with the exception of Mg., but the general adequacy of the diet is indicated by the fact that the animals grew to maturity, reproduced normally, and weaned their young in the usual time. The Mg. deficient rats grow quite as rapidly as those kept on the full diet; nevertheless, like the others, they manifest a lower resistance to infection.

Parallel with the determination of the effect of salt deficient diets on resistance, it seemed important to ascertain the physiological effect of the elimination of various cations from the diet.