Sodium retention in black and white female adolescents in response to salt intake

Abstract

Increased sodium (Na+) retention in blacks could be related to the high prevalence of hypertension in adult blacks. Na+ retention in response to controlled dietary Na+ has not been rigorously compared in the different race groups. The present study assessed Na+ retention in 22 black and 14 white girls, 11-15 yr old, during 3 wk on a low (1.3 g, 57 mmol)- and during 3 wk on a high (4 g, 172 mmol)-Na+ diet in a randomized order, crossover design. Subjects were matched by postmenarcheal age and weight. After a 1-wk equilibration period, the mean daily Na + retention was 357 ± 69 mg (15.5 ± 3.0 mmol) in blacks and 239 ± 37 mg (10.4 ± 1.6 mmol) in whites on the low-Na + diet and 991 ± 138 mg (43.1 ± 6.0 mmol) in blacks vs. 334 ± 90 mg (14.5 ± 3.9 mmol) in whites (P < 0.001) on the high-Na+ diet. The greater Na+ retention in blacks was not accompanied by an increase in fecal or sweat Na+ excretion. Blood pressure and weight did not increase despite the Na+ retention, and thus, the retained Na+ appeared to reside in a nonextracellular compartment that we speculate to be bone. In summary, black girls showed greater Na+ retention compared with white girls. The difference in Na + handling may contribute to underlying racial differences in susceptibility to hypertension.