DIETARY PATTERNS AND BLOOD PRESSURE

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The purpose of this collaborative study is to develop strategies for reducing blood pressure in individuals with mildly elevated or high-normal blood pressure using diets high in potassium and/or calcium. Epidemiological data clearly demonstrate an inverse relationship between intake of these nutrients and blood pressure. Numerous clinical trials suggest that both potassium and calcium decrease blood pressure when they are provided as supplements. Clinical trials, however, have been inconsistent and little data are available concerning the efficacy of increased potassium or calcium in the diet. Study subjects will be adult men and women with high normal or mildly elevated blood pressure. Subjects will be eligible if systolic blood pressure is 130-159 mmHg and/or diastolic blood pressure is 80-99 mmHg. Subjects will be excluded, however, if they have clear evidence of hypertension (i.e., systolic blood pressure greater than or equal to 160 mmHg or diastolic blood pressure greater than or equal to 100 mmHg). In order to ensure that the results of this trial are applicable to the general public, we will include approximately 50% minorities (African and Asian Americans). After a 4-week baseline period during which all participants will eat a "Control" diet, designed to be representative of local dietary patterns, subjects will be randomly assigned to one of four dietary patterns: Control (2400 mg/d potassium, 625 mg/d calcium); High Potassium (5500 mg/d potassium, 625 mg/d calcium); High Calcium (2400 mg/d potassium; 1200 mg/d calcium); or High Potassium/High Calcium (5500 mg/d potassium; 1200 mg/d calcium). All diets will contain 30% of calories as fat and 3000 mg/d of sodium. Diets will be isocaloric to assure that changes in body weight will not affect blood pressure. Treatment will continue for 12 weeks. Food will be prepared in the metabolic kitchen unit of the Sarah W. Stedman Center for Nutritional Studies at Duke University. Meals will be consumed in the Stedman Center cafeteria, under the observation and supervision of a registered dietitian. The dietary patterns will be compared to changes in blood pressure.