Abstract Body: Dietary high sodium intake is a modifiable risk factors for cardiovascular (CV) diseases including vascular dysfunction and subsequently arteriosclerosis. A partial sodium substitution by potassium is associated with a lower risk of CV events and death. Our aim was to investigate the acute impact of sodium and potassium on retinal microvascular function, an established biomarker for systemic CV risk stratification.
Eighteen male and 27 female healthy individuals (mean age 31years) were randomized to eat a salty soup containing either 9g sodium chloride (high salt group), 6g sodium chloride (intermediate salt group) or 6g sodium chloride plus 3g potassium chloride (substitution group). Microvascular measurements were performed before (t0) as well as four (t4) and 24 hours (t24) after soup intake. Microvascular health was measured by investigating retinal vessel diameters. A higher arteriolar-to-venular diameter ratio (AVR) is associated with improved vascular health. Microvascular endothelial function was quantified by flickerlight-induced retinal arteriolar dilation.
The 9g (139±2mmol/l vs. 141±2mmol/l, p<0.001) and 6g salt group (140±1mmol/l vs. 141±2 mmol/l, p=0.028) had higher serum sodium concentrations at t4 compared to baseline. Serum sodium concentrations of the substitution group showed no significant difference between time points, but a significant increase in serum potassium (3.7±0.3mmol/l vs. 3.9±0.2mmol/l, p=0.019). Microvascular endothelial function was significantly decreased in the high salt group from baseline to t4 (4.5±2.2% vs. 3.7±2.2%, p=0.041), without significant changes in the other groups. In the sodium groups, there was a strong correlation between the increase in serum sodium concentration from t0 to t4 and an impaired endothelial function after t4 (R²=0,255, p=0,005). The substitution group showed improved microvascular health, quantified by higher AVR at t4 compared to t0 (0,83±0,07 vs. 0,86±0,07, p<0,001). An increase in serum sodium was negatively associated with AVR (R²=0,14, p=0,013) whereas an increase in serum potassium was positively correlated with AVR (R²=0,19, p=0,003).
An acute increase in serum sodium is associated with impaired microvascular endothelial function. Replacement of sodium by potassium seems to improve microvascular function already after a single potassium intake. These results might explain the beneficial effects of potassium on CV outcomes as well as the harmful effects of sodium on vascular function.