Sodium versus potassium: effects on postprandial blood pressure and measures of blood vessel function

Background Extensive research indicates excessive sodium intake leads to an increased risk of hypertension. Postprandial studies suggest endothelial dysfunction occurs in response to a meal high in sodium compared to a low sodium meal. Dietary intervention studies suggest a reduction in blood pressure (BP) and improvements in pulse wave analysis measures in hypertensive populations, following replacement of sodium with potassium. Objective The present study aimed to investigate and compare the effects of moderately high sodium (54 mM Na+; 11 mM K+), moderately potassium rich (14 mM Na+; 36 mM K+) and low sodium meals (14 mM Na+; 11 mM K+) on postprandial (up to 3 hr) blood pressure and blood vessel function as measured by pulse wave analysis. Design A double-blind cross-over study was conducted in 41 normotensive adults (mean age 57.5±11.6 years; 12 males). For 48 hr prior to testing subjects avoided food items high in sodium or potassium. Fasting subjects consumed one of three test meals; brachial BP and measures of blood vessel function, including augmentation pressure/index, were performed at 15 min intervals over 3 hr. There was a minimum of 72 hr washout between test sessions. Outcomes All three meals led to reductions in postprandial brachial and central BP (~6 mmHg; all p<0.001). Overall there was no significant difference between the three meals in their postprandial effects on brachial or central BP, or augmentation pressure/index. When postprandial data was separated into first and second 90 min periods, the low sodium meal provided the greatest reduction in both brachial and central diastolic pressure and values were significantly lower compared to the high potassium meal during the first 90 min of postprandial period (-2.20 mmHg; 95% CI -4.02 to -0.36; p=0.03) Conclusion Various meals reduced blood pressure, but there was a greater early reduction in diastolic pressure after the low sodium meal compared to the high potassium meal. Source of funding Clifford Craig Medical Research Trust, Launceston, TAS