Effects of sodium and potassium supplementation on endothelial function: a fully controlled dietary intervention study

High Na and low K intakes have adverse effects on blood pressure, which increases the risk for CVD. The role of endothelial dysfunction and inflammation in this pathophysiological process is not yet clear. In a randomised placebo-controlled cross-over study in untreated (pre) hypertensives, we examined the effects of Na and K supplementation on endothelial function and inflammation. During the study period, subjects were provided with a diet that contained 2.4 g/d of Na and 2.3 g/d of K for a 10 460 kJ (2500 kcal) intake. After 1-week run-in, subjects received capsules with supplemental Na (3.0 g/d), supplemental K (2.8 g/d) or placebo, for 4 weeks each, in random order. After each intervention, circulating biomarkers of endothelial function and inflammation were measured. Brachial artery flow-mediated dilation (FMD) and skin microvascular vasomotion were assessed in sub-groups of twenty-two to twenty-four subjects. Of thirty-seven randomised subjects, thirty-six completed the study. Following Na supplementation, serum endothelin-1 was increased by 0.24 pg/ml (95 % CI 0.03, 0.45), but no change was seen in other endothelial or inflammatory biomarkers. FMD and microvascular vasomotion were unaffected by Na supplementation. K supplementation reduced IL-8 levels by 0.28 pg/ml (95 % CI 0.03, 0.53), without affecting other circulating biomarkers. FMD was 1.16 % (95 % CI 0.37, 1.96) higher after K supplementation than after placebo. Microvascular vasomotion was unaffected. In conclusion, a 4-week increase in Na intake increased endothelin-1, but had no effect on other endothelial or inflammatory markers. Increased K intake had a beneficial effect on FMD and possibly IL-8, without affecting other circulating endothelial or inflammatory biomarkers.