The proposed study is a double-blind, two period cross-over clinical trial comparing the effects of two levels of dietary sodium on blood pressure in Black men and women, aged 30-55 with diastolic blood pressure 75-89 mmHg and systolic blood pressure < 150 mmhg. All participants will be given 6 weeks of intensive nutritional counseling to lower 24-hour urine sodium output from an estimated 165 mEq/24 hours at baseline to < 100 mEq/24 hours. Only those participants who excrete < 100 mEq/24 hours after 6 weeks of intensive dietary sodium intervention and have greater than 70% adherence to study capsules, in the lead in period will be eligible to be randomized. Participants will be assigned to one to two treatment sequences: (1) 100 mEq of sodium chloride capsules per day during period 1 followed by placebo capsules during period 2; (2) placebo capsules during period 1 followed by 100 mEq of sodium chloride capsules per day during period 2. The sodium and placebo capsules will be identical in appearance and participants will take nine capsules per day. The major endpoint is change in diastolic and systolic blood pressure on sodium. A number of other measures will be carried out including blood chemistries, glucose tolerance (glucose and insulin), insulin resistance, urinary kallikrein, serum renin, and plasma norepinephrine. Other major aims include: 1) testing general new diagnostic criteria for sodium sensitivity, 2) examine predictors of sodium sensitivity and 3) examine how changes in sodium intake influences change in specific metabolic parameters. The design incorporates careful control of the dietary changes and strict standardization of blood pressure measurement with a random-zero device. This study permits a more precise estimate of the effects of sodium chloride on blood pressure in Blacks and a systematic examination of sodium sensitivity defined by various methods. The results will have significance in answering questions about risk factors for blood pressure in Blacks and for defining sodium sensitivity.
| Flack, John M; Grimm Jr, Richard H; Staffileno, Beth A et al. (2002) New salt-sensitivity metrics: variability-adjusted blood pressure change and the urinary sodium-to-creatinine ratio. Ethn Dis 12:10-9 |
| Flack, J M; Neaton, J; Grimm Jr, R et al. (1995) Blood pressure and mortality among men with prior myocardial infarction. Multiple Risk Factor Intervention Trial Research Group. Circulation 92:2437-45 |
