Dietary Calcium May Lower Blood Pressure
Eating a diet rich in calcium is associated with significant blood pressure reduction in women, but not in men, according to a recent study published in the Journal of Human Hypertension.1
In this new study, researchers surveyed the dietary habits of almost 500 Japanese men and women. The amount of calcium in each person’s diet was then correlated with his or her blood pressure. There was a significant relationship between higher dietary calcium intake and lower blood pressure among the women in the study. After correcting for other factors known to affect blood pressure (including age, weight, alcohol consumption, and salt intake), the researchers found that with each increase of 100 mg per day in dietary calcium, both systolic and diastolic blood pressure dropped by roughly two-thirds of a point (i.e., 0.7 mm Hg). Although men eating more calcium also tended to have a lower blood pressure, the effect was not statistically significant.
The average woman in this study was eating 600 mg of calcium per day. According to this research, therefore, increasing calcium intake to 1,200 mg per day (the recommended dietary allowance for women over age 50) would potentially reduce blood pressure by about four points. This degree of blood pressure reduction could have a profound effect on the incidence of heart disease and stroke nationwide.
High blood pressure, or hypertension, is a major risk factor for heart attack and stroke. It is also extremely common, and often undiagnosed. Another study, published this week in the Journal of the American Medical Association, estimates that nine in ten Americans will develop high blood pressure at some point in their lives.2
While the new research provides indirect evidence that eating foods high in calcium may help reduce blood pressure in some people, much more is known about the effect of calcium pills. Supplementation with calcium has been shown to produce a small but statistically significant reduction in blood pressure in a number of clinical trials.3 Most of these studies used an intake of between 800 and 1,000 mg of supplemental calcium per day.
Foods high in calcium include dairy products, canned fish, green leafy vegetables, and tofu that has been curdled with calcium salts. Two glasses of milk and 8 ounces of calcium-curdled tofu each contain about 600 mg of calcium.
It appears likely from the results of this and other studies that women can now expect extra calcium may help prevent high blood pressure in addition to the well-known effect of protecting against osteoporosis.
1. Morikawa Y, Nakagawa H, Okayama A, et al. A cross-sectional study on association of calcium intake with blood pressure in Japanese population. J Hum Hypertens 2002;16:105-10.
2. Vasan RS, Beiser A, Seshadri S, et al. Residual lifetime risk for developing hypertension in middle-aged women and men. The Framingham Heart Study. JAMA 2002;287:1003-10.
3. Griffith LE, Guyatt GH, Cook RJ, et al. The influence of dietary and nondietary calcium supplementation on blood pressure: an updated metaanalysis of randomized controlled trials. Am J Hypertens 1999;12:84–92.
Matt Brignall, ND, is in practice at the Seattle Cancer Treatment and Wellness Center and at the Evergreen Integrative Medicine Clinic in Kirkland, WA. He specializes in integrative treatment of cancer. He is a contributor to Healthnotes and Healthnotes Newswire.
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