The mechanism underlying blood pressure reduction in the high fruits and vegetables arm of the Dietary Approaches to Stop Hypertension (DASH) Study is unknown but may include potassium, magnesium and fiber. This study was designed to separate minerals and fiber from other components of DASH on blood pressure in abdominally obese metabolic syndrome subjects with prehypertension to Stage 1 hypertension (obese hypertensives). Fifteen obese hypertensives and 15 lean normotensives were studied on a standardized usual diet, randomized to DASH or usual diet supplemented with potassium, magnesium and fiber to match DASH, then crossed over to the complementary diet. All diets were three weeks long, isocaloric and matched for sodium and calcium. In obese hypertensives, blood pressure was lower after 3 weeks on DASH than usual diet (-7.6±1.4/-5.3±1.4 mmHg, p<0.001/0.02 and usual diet supplemented (-6.2±1.4/-3.7±1.4 p<0.005/0.06), whereas blood pressure was not significantly different on usual and supplemented diets. Blood pressure values were not different among the three diets in lean normotensives. Small artery elasticity was lower in obese hypertensives than lean normotensives on the usual and supplemented diets (p<0.02). This index of endothelial function improved in obese hypertensives (p<0.02) but not lean normotensives on DASH and was no longer different from values in lean normotensives (p>0.50). DASH is more effective than potassium, magnesium, and fiber supplements for lowering blood pressure in obese hypertensives, which suggest that high fruits and vegetables DASH lowers blood pressure and improves endothelial function in this group by nutritional factors in addition to potassium, magnesium and fiber.

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According to results from this review of current practice in US hospitals, fluid optimization would likely lead to decreased variability and improved outcomes.