Urinary Sodium/Potassium Ratio Index Estimates Ionic Balance in Humans

This study measured the urinary sodium/potassium (U-Na/K) ratio using a compact ion meter to verify whether the U-Na/K ratio can estimate human blood pressure (BP) and ionic balance. The U-Na/K ratio and BP were measured in five healthy participants (including one female) after urination for at least two days per person, and lifestyle information, such as exercise and diet, were recorded at the time of measurement. Analysis of the measured data at 57 points revealed no significant difference in the U-Na/K ratio and BP, but a significant decrease in the U-Na/K ratio was observed after exercise accompanied by sweating (P = 0.01). Although previous studies have demonstrated that sodium is released by sweating, its measurement is difficult. Measuring sodium/potassium ratio is useful for preventing heatstroke and may serve as an explanatory variable for sweating and exercise intensity.