Effects of dietary sodium on body and muscle potassium content during heat acclimation

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Abstract
It has been suggested that renal conversion of sodium (Na+) during training in hot environments results in potassium (K+) deficiencies. This investigation examined the influence of two levels of dietary Na+ intake (399 vs 98 mmol · d−1) on intramuscular, urinary, sweat, and whole body K+ homeostasis. Nine unacclimated, untrained males underwent heat acclimation during two 8 day dietary-exercise regimens (40.1±0.1‡ C, 23.5±0.4%RH). Both diets resulted in depressed urinary K+ excretion. Sweat K+ and muscle K+ concentrations were not altered by diets or acclimation. The whole body stores of Na+ increased 31.1% (+ 916.8 mmol) during the high Na+ diet and decreased 7.8% (−230.4 mmol) during the low Na+ diet; whole body stores of K+ increased 4.1% (+ 137.6 mmol) during the high Na+ diet and increased 3.4% (+ 113.6 mmol) during the low Na+ diet. This dietary-acclimation protocol did not result in whole-body or intramuscular K+ deficits and offers no evidence to support previous claims that dietary sodium levels affect K+ balance.