The Influence of Sodium and Potassium Intake and Insulin Resistance on Blood Pressure in Normotensive Individuals Is More Evident in Women

BACKGROUND: Considering sex differences, salt sensitivity, and insulin resistance (IR), the effect of sodium restriction and increased potassium intake on blood pressure remains unclear in normotensive Asian individuals, compared to that in hypertensive patients. METHODS: To assess the influence of sodium and potassium intake in normotensive individuals, we evaluated the estimated 24-hour urinary sodium and potassium excretion rate in 3,392 drug-naive normotensive Japanese individuals (average age: 48.4 years) and analyzed its relation to blood pressure using multivariate regression analysis. RESULTS: Multivariate regression analysis revealed that a 10-mmol/day increment in urinary sodium excretion related to an elevation in systolic blood pressure of 0.16 mm Hg in men and 0.37 mm Hg in women, after adjusting for known risk factors to salt sensitivity, including age, body mass index, serum creatinine, homeostasis model assessment of IR, and urinary potassium excretion. For urinary potassium excretion, a 10-mmol/day increment was associated with a decrease in systolic blood pressure, -0.54 mm Hg in men and -1.49 mm Hg in women, respectively. Furthermore, involvement of IR on blood pressure was observed only in women. CONCLUSIONS: In drug-naive normotensive individuals, the effects of a lower-salt and higher-potassium diet, and IR on blood pressure, were more evident in women. These results suggest that to prevent the new onset of hypertension and its complications, the balances of a sodium restriction and an increased potassium intake are important even in normotensive individuals, independent of known risk factors for salt sensitivity, especially in women.