Person:

Moore, Thomas Burton

BACKGROUND: It is known that obesity, sodium intake, and alcohol consumption factors influence blood pressure. In this clinical trial, Dietary Approaches to Stop Hypertension, we assessed the effects of dietary patterns on blood pressure. METHODS: We enrolled 459 adults with systolic blood pressures of less than 160 mm Hg and diastolic blood pressures of 80 to 95 mm Hg. For three weeks, the subjects were fed a control diet that was low in fruits, vegetables, and dairy products, with a fat content typical of the average diet in the United States. They were then randomly assigned to receive for eight weeks the control diet, a diet rich in fruits and vegetables, or a "combination" diet rich in fruits, vegetables, and low-fat dairy products and with reduced saturated and total fat. Sodium intake and body weight were maintained at constant levels. RESULTS: At base line, the mean (+/-SD) systolic and diastolic blood pressures were 131.3+/-10.8 mm Hg and 84.7+/-4.7 mm Hg, respectively. The combination diet reduced systolic and diastolic blood pressure by 5.5 and 3.0 mm Hg more, respectively, than the control diet (P<0.001 for each); the fruits-and-vegetables diet reduced systolic blood pressure by 2.8 mm Hg more (P<0.001) and diastolic blood pressure by 1.1 mm Hg more than the control diet (P=0.07). Among the 133 subjects with hypertension (systolic pressure, > or =140 mm Hg; diastolic pressure, > or =90 mm Hg; or both), the combination diet reduced systolic and diastolic blood pressure by 11.4 and 5.5 mm Hg more, respectively, than the control diet (P<0.001 for each); among the 326 subjects without hypertension, the corresponding reductions were 3.5 mm Hg (P<0.001) and 2.1 mm Hg (P=0.003). CONCLUSIONS: A diet rich in fruits, vegetables, and low-fat dairy foods and with reduced saturated and total fat can substantially lower blood pressure. This diet offers an additional nutritional approach to preventing and treating hypertension.

Dietary studies designed to decrease the urinary albumin excretion rate (AER) typically reduce protein by increasing lower protein plant foods and decreasing higher protein animal products. STUDY DESIGN: We evaluated AER while increasing protein intake in the Dietary Approaches to Stop Hypertension (DASH) Trial (randomized, parallel group, 8 week controlled feeding). SETTING & PARTICIPANTS: 378 individuals without diabetes with prehypertension or stage I hypertension. INTERVENTION: The DASH diet, 18% energy from protein, emphasizes, among other features, low-fat dairy products; and the fruit/vegetable (FV) and control diets, each with 15% energy from protein. OUTCOME: AER. MEASUREMENTS: We measured AER by using immunoassay and covariates at baseline and after 8 weeks. RESULTS: Baseline AER had a geometric mean value of 4.0 +/- 0.2 (SE) mg/24 h. In 285 participants with baseline AER less than 7 mg/24 h, AER was unchanged by diet treatment (geometric mean, 2.5 +/- 0.2 mg/24 h in the control diet, 3.0 +/- 0.2 mg/24 h in the FV diet, and 2.8 +/- 0.2 mg/24 h in the DASH diet). Conversely, in 93 participants with baseline AER of 7 mg/24 h or greater, end-of-feeding AER was lower in the FV diet (6.6 +/- 1.0 mg/24 h) than in the control (11.4 +/- 1.8 mg/24 h; P = 0.01) or DASH diets (11.7 +/- 1.6 mg/24 h; P = 0.005). The DASH and control diets were not different (P = 0.9). LIMITATIONS: Long-term AER change not studied. CONCLUSIONS: The decrease in AER after 8 weeks occurred in only those with high-normal baseline AER in the FV diet, in a pattern distinct from the blood pressure decrease. The DASH diet did not increase AER despite a 3% increase in energy from protein.

In populations, dietary intakes of potassium, calcium, and magnesium each have been inversely associated with blood pressure. However, most clinical trials in normotensive populations have not found that dietary supplements of these minerals lowered blood pressure. We tested the hypothesis that normotensive persons who have low habitual intake of these minerals would be particularly responsive to supplementation. Three hundred normotensive women in the Nurses Health Study II (mean age, 39 years), whose reported intakes of potassium, calcium, and magnesium were between the 10th and 15th percentiles, received for 16 weeks’ duration daily supplements of either potassium 40 mmol, calcium 30 mmol (1200 mg), magnesium 14 mmol (336 mg), all three minerals together or placebos. At baseline, mean (±SD) 24-hour ambulatory blood pressures were 116±8 and 73±6 mm Hg systolic and diastolic, respectively, and mean dietary intakes of potassium, calcium, and magnesium were 62±20 mmol/d, 638±265 mg/d, and 239±79 mg/d, respectively. The mean differences (with 95% confidence intervals) of the changes in systolic and diastolic blood pressures between the treatment and placebo groups were significant for potassium, −2.0 (−3.7 to −0.3) and −1.7 (−3.0 to −0.4), but not for calcium, −0.6 (−2.2 to 1.0) and −0.7 (−2.0 to 0.6), or for magnesium, −0.9 (−2.6 to 0.8) and −0.7 (−2.2 to 0.8). The administration of calcium and magnesium with potassium did not enhance the effect of potassium alone; and the changes in blood pressure were not significant −1.3 (−3.0 to 0.4) and −0.9 (−2.2 to 0.4). In conclusion, potassium, but not calcium or magnesium supplements, has a modest blood pressure–lowering effect in normotensive persons with low dietary intake. This study strengthens evidence for the importance of potassium for blood pressure regulation in the general population.

Dietary potassium, calcium, and magnesium have each been inversely associated with blood pressure in populations.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Since these cations exist together in commonly eaten foods such as fruits, nuts, vegetables, cereals, and dairy products, their intakes are highly correlated. This collinearity makes it difficult in epidemiological studies to distinguish which among these dietary cations has a causal role in blood pressure regulation.1 Meta-analysis of clinical trials found a significant blood pressure–lowering effect (−5.9/−3.4 mm Hg) for potassium supplementation in hypertensive but not in normotensive persons.10 16 Meta-analysis suggested that calcium supplementation has a small effect (−1.7 mm) on systolic blood pressure in hypertensive but not normotensive patients.17 18 Magnesium produced inconsistent results in trials of hypertensives,19 20 21 22 23 24 25 26 27 28 and no effect in normotensives.29 30 The lack of effect of mineral supplements in clinical trials of normotensives is inconsistent with the significant associations in epidemiological studies, since normotensive persons comprise the vast majority of the population samples.

One possible explanation for the divergence in findings between the observational epidemiologic studies and the clinical trials in normotensive persons is that a subset of the population that is relatively deficient from low intake of minerals may be particularly responsive to supplementation. Epidemiological studies tend to compare those in the lowest category of intake, which serves as a point of reference, with persons having average or high intake. In contrast, most trials have tested the effect of raising an average intake to a high intake. An alternative explanation is that these minerals work in concert to reduce blood pressure and that they would be more effective when given together. To explore both possibilities, we conducted a clinical trial of potassium, magnesium, and calcium supplements, given singly and together, to participants in the Nurses Health Study II who reported habitually low intakes of these minerals.