Interactions of dietary sodium and potassium and their influence on energy metabolism

¹ Department of Animal Husbandry, University of California, Davis, California

A factorial design consisting of sodium (0.23 and 0.004%) superimposed on three levels of dietary potassium (0.002, 0.02, and 0.44%) was used. Energy utilization, body composition, activity, basal metabolism, body water compartments, and concentrations of sodium and potassium therein were studied in rats fed these rations. A large number of interactions between dietary Na and K were shown; the effect of either Na or K deficiency is dependent on the level of the other in the diet. Efficiency of energy utilization was lowered by a deficiency of either mineral. A slight reduction of basal energy metabolism was found in rats fed the low-sodium rations, whereas low-potassium rations had no significant effect. The decreased efficiency of energy utilization with low-sodium rations were attributed, at least partly, to increased activity. The multiple regression of basal metabolic rate on the concentrations of plasma Na, plasma K, intracellular Na, and intracellular K was found to be highly significant but no causative relationship is inferred.