Objective: Several studies have confirmed the remarkable observation that cumulative urinary potassium (K+) excretion is less in African–Americans than White Americans even when identical amounts of potassium are provided in the diet. This study was designed to examine whether this decrease in urinary potassium could be compensatory to an increase in gastrointestinal excretion of potassium in African–Americans.
Methods: Twenty-three young, healthy, normotensive participants of both sexes and races were placed on a fixed diet of 100 mEq per day of K+ and 180 mEq per day of sodium (Na+) for 9 days. All urine and stool were collected daily and analyzed for electrolytes. Blood was obtained for determination of electrolytes, blood urea nitrogen (BUN), creatinine, glucose, insulin, renin, and aldosterone at the beginning and at the end of the study period.
Results: Cumulative urinary excretion of K+ was significantly less in African–Americans (609 ± 31 mEq) compared with White Americans (713 ± 22 mEq, P = 0.015). There was no significant racial difference, however, in the cumulative gastrointestinal excretion of K+ (105 ± 11 versus 95 ± 9 mEq, P = 0.28) in African–Americans versus White Americans, respectively.
Conclusion: The racial difference in urinary K+ handling manifested by decreased excretion of K+ in African–Americans cannot be attributed to an increase in net gastrointestinal excretion of this cation.
aDivisions of Nephrology/Hypertension, Department of Medicine
bDivisions of Endocrinology, Metabolism and Molecular Medicine
cDivision of Gastroenterology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
Correspondence to Robert M. Rosa, MD, Feinberg School of Medicine, Arthur J. Rubloff Building, 420 East Superior St., Chicago, IL 60611-3008, USA. Tel: +1 312 908 5502; fax: +1 312 503 7654; e-mail: firstname.lastname@example.org
Abbreviations: K+, Potassium, Na+, Sodium
Received 26 March, 2012
Revised 27 July, 2012
Accepted 6 September, 2012