Racial Differences in Urinary Potassium Excretion

Abstract

Racial differences in potassium (K) intake and urinary K excretion may contribute to the higher BP observed in black compared with white individuals. Although black individuals typically consume less dietary K than white individuals, the lower urinary K excretion observed in black individuals may reflect more than differences in intake. In this study, data from the Dietary Approaches to Stop Hypertension (DASH) trial (413 white and black participants) were used to evaluate urinary K excretion in black and white individuals with similar K intake. At screening, mean urinary K excretion was higher in white than black individuals (mean Delta = 645 mg/d for white minus black individuals, adjusted for age, gender, and weight; P < 0.001). After a 3-wk run-in period during which all participants received a low-K control diet, a significant racial difference remained (mean Delta = 201 mg/d, adjusted for age, gender, and caloric intake; P < 0.001). Participants were then randomly assigned to continue the control diet or switch to a high-K diet (either a high fruit/vegetable diet or the DASH diet) for 8 wk. At the end of intervention, the mean difference in urinary K in white compared with black individuals after adjustment for age, gender, and caloric intake was -6 mg/d (P = 0.95) in the control group, 163 mg/d in the fruits/vegetables group (P = 0.39), and 903 mg/d in the DASH group (P < 0.001). Racial differences in urinary K excretion seem to reflect more than intake differences; further studies are needed to understand their potential impact on clinical outcomes.