OBJECTIVE: The objectives of the present study were to evaluate the effects of oral potassium supplementation, associated with a hypocaloric diet and aerobic exercises, on plasma potassium levels, blood pressure and insulin resistance, in centrally obese, not well controlled hypertensive patients on diuretic therapy; waist to hip ratio >0.85 in women, and >0.95 in men; systolic blood pressure >140mmHg and <160mmHg and/or diastolic blood pressure >90mmHg and <105mmHg. METHODS: This was a prospective double-blind randomized study including 22 patients divided in 2 groups: sodium chloride n=10, and potassium chloride n=12. For 12 weeks, each group received cooking salt containing, either 100% sodium chloride, or 50% sodium chloride and 50% potassium chloride. All patients were submitted to a hypocaloric diet and advised to increase their physical activity; a 40-minute walk three times a week. Before and after the study period, all patients were submitted to determinations of body mass index, body composition, waist circumference, sodium and potassium urinary excretions, sodium and potassium serum levels, 24h ambulatory blood pressure monitoring, oral glucose tolerance test with serum insulin measurements at fasting and 120 minutes after glucose load, and serum lipid profile. RESULTS: In both groups, no changes were observed in serum sodium and potassium levels, in blood glucose and insulin levels, insulin resistance indexes and serum lipid profile. The body mass index decreased similarly in both groups; 3.5±2.0% in sodium Chloride, and 2.7±3.2% in Potassium Chloride, as well as 24 h systolic ambulatory blood pressure monitoring mean; from 134.7 ±14.8 to 130.2±12.6mmHg (p<0.05) in group sodium chloride, and from 128.2±7.4 to 122.9±5.7mmHg (p<0.05) in potassium, and 24h diastolic ambulatory blood pressure monitoring from 84.4±10.2 to 81.4 ± 8.9mmHg in sodium chloride, and from 84.0±5.7 to 79.5±3.9mmHg (p<0.05) in group potassium (p<0.05). Changes in 24h systolic ambulatory blood pressure monitoring correlated with changes in the waist circumference, but not with changes in bory mass index when all patients were analyzed together. Serum lipid profile, blood glucose levels and insulin resistance indexes did not differ between groups and did not change during the study. CONCLUSION: Weight reduction induced by life style changes, promotes reductions in blood pressure, which are proportional to reductions in abdominal fat. Potassium supplementation through cooking salt was insufficient to avoid serum potassium falling during diuretic therapy and did not show any additional beneficial effect on blood pressure or insulin resistance in hypertensive patients with central obesity.
potassium chloride; diuretics; obesity; arterial blood pressure; insulin resistance
