Harvard Medical School researchers who followed the dietary intake of almost 30,000 women for 10 years have found that consuming calcium and Vitamin D can reduce the risk of high blood pressure.

The study, which was published this month in the American Heart Association’s Hypertension Journal, showed that middle-aged women who regularly drank low-fat milk have a significantly lower chance of having hypertension risks than women who didn’t drink milk on a daily basis.

JoAnn E. Manson ’75, a Medical School professor and the chair of preventive medicine at Brigham and Women’s Hospital, said that she and her colleagues started working on the study in 1992 with the hope of understanding the role of diet and other factors in health problems such as cardiovascular diseases.

“High blood pressure is a highly prevalent health problem in the U.S.,” Manson said. “Even a small reduction in risk through lifestyle modifications is important.”

The American Heart Association’s Web site estimates that 73 million people in the U.S. over the age of 20 have high blood pressure.

According to Lu Wang, who is also part of Brigham and Women’s preventive medicine division, a total of 39,310 female health professionals over the age of 45 completed a detailed diet and food questionnaire, 28,886 of which were used in the study.

The questionnaire consisted of 131 items and assessed dairy products including skim milk, cream cheese, low-fat yogurt, and ice cream.

“This was a large-scale epidemiologic study,” Manson said. “We were particularly interested in low-fat dairy products, specifically the role of calcium and vitamin D in the development of hypertension.”

Both Manson and Wang said that the findings did not show a strong correlation between high-fat dairy products or dietary supplements and reduced hypertension.

“The benefit may be related to the complex mixture in dairy products,” Manson said. “Taking calcium or Vitamin D supplements will not necessarily lower blood pressure.”

Although the study was primarily focused on middle-aged women, both Manson and Wang suggested that low-fat dairy products may lower the risk of hypertension in both younger women and men as well.

“Our study is in support of the U.S. Department of Agriculture recommendations that the majority of Americans should increase their intake of milk products to three servings per day,” Wang said.

—Staff writer June Q. Wu can be reached at junewu@fas.harvard.edu.