Dietary sodium restriction alters postprandial ghrelin: implications for race differences in obesity.

OBJECTIVES To examine the effect of sodium restriction on the appetite-stimulating hormone, ghrelin, as a function of race, salt sensitivity, and obesity. DESIGN PARTICIPANTS completed two 4-day outpatient dietary interventions (moderate vs low sodium), and blood samples were drawn two hours after a controlled test meal under both conditions. SETTING A university research laboratory and affiliated General Clinical Research Center. PARTICIPANTS 37 women (18 Black, 19 White) and 18 men (9 Black, 9 White), aged 36-63 years. MEASURES Cardiovascular function (blood pressure, heart rate, impedance-derived indices of cardiac output and peripheral resistance) was measured after a 20-minute rest before each test meal. Blood was drawn by intravenous forearm catheter two hours after each test meal and later assayed for ghrelin, leptin, and norepinephrine. RESULTS After four days of sodium restriction, postprandial ghrelin increased in White men and women and Black men but decreased in Black women. Salt sensitivity, but not obesity, was also related to ghrelin response during sodium restriction; postprandial ghrelin tended to increase among salt-sensitive subjects during salt restriction but decrease among salt-resistant subjects during salt restriction. CONCLUSIONS Satiety hormone dysregulation may play a role in: 1) the heightened obesity-related morbidity among Black women, in particular; 2) adherence to sodium-restricted diets; and 3) race differences in behavioral weight-loss interventions that include sodium restriction.