EFFECT ON BLOOD-PRESSURE OF POTASSIUM, CALCIUM, AND MAGNESIUM IN WOMEN WITH LOW HABITUAL INTAKE

In populations, dietary intakes of potassium, calcium, and magnesium e ach have been inversely associated with blood pressure. However, most clinical trials in normotensive populations have not found that dietar y supplements of these minerals lowered blood pressure. We tested the hypothesis that normotensive persons who have low habitual intake of t hese minerals would be particularly responsive to supplementation. Thr ee hundred normotensive women in the Nurses Health Study II (mean age, 39 years), whose reported intakes of potassium, calcium, and magnesiu m were between the 10th and 15th percentiles, received for 16 weeks' d uration 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 pressure s 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 systoli c and diastolic blood pressures between the treatment and placebo grou ps 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 a dministration 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 conclusi on, potassium, but not calcium or magnesium supplements, has a modest blood pressure-lowering effect in normotensive persons with low dietar y intake. This study strengthens evidence for the importance of potass ium for blood pressure regulation in the general population.