Women who drink fat-free milk -- or who get calcium and vitamin D from their food -- have a lower risk of high blood pressure, according to a new study.

Harvard University researchers examined the diets of 30,000 middle-aged and older women. They found that women who drank two or more servings of fat-free milk each day reduced their risk for high blood pressure by up to 10 percent compared to those who drank fat-free milk less than once a month.

The same was not found for higher fat milk or those who took calcium and vitamin D supplements.

One in three American adults has high blood pressure, and an increasing number of women are living with undiagnosed hypertension, according to a second study published in the journal Circulation.

High blood pressure puts people at risk for heart disease, stroke and even kidney failure.

Previous research has linked a diet of low-fat dairy, fruits and vegetables to blood pressure benefits, which is one reason the U.S. Dietary Guidelines for Americans recommend drinking three glasses of lowfat or fat-free milk each day.