NEW YORK (Reuters Health) - Women who get plenty of whole grains in their diet may lower their risk of developing high blood pressure, a large study suggests.

Researchers found that middle-aged and older women who ate the most whole grains were less likely than those with the lowest intakes to develop high blood pressure over the next 10 years.

The benefit was modest. Women who consumed the most whole grains had an 11-percent lower risk of high blood pressure than those with the lowest intakes.

But the findings add to evidence of the cardiovascular benefits of whole grains such as oatmeal, bran and brown rice. Past studies have tied diets rich in these foods to lower risks of heart disease and stroke.

The fiber and other nutrients in whole grains may help lower cholesterol, blood sugar and insulin levels, as well as improve blood vessel functioning and reduce inflammation in the circulatory system. Whether whole grains benefit blood pressure has been unclear, however.

For the current study, researchers at Harvard University in Boston used data from the Women's Health Study, which has followed nearly 40,000 U.S. female health professionals since 1992. Upon entering the study, the women completed detailed questionnaires on their diet habits, including their usual intake of whole-grain foods like dark bread, popcorn, oatmeal and whole-grain breakfast cereals.

Of the nearly 30,000 women who were free of high blood pressure at the outset, those who ate the most whole grains had a lower risk of developing the condition. The apparent protective effect held when the researchers considered other factors, like weight, smoking and exercise habits.

In contrast, refined grains -- like pasta, white bread and other foods made from white flour -- were unrelated to high blood pressure risk, according to the researchers, led by Dr. Lu Wang.

Unlike whole grains, refined grains are largely stripped of the fiber- and nutrient-rich bran and germ components of the plant. This difference may explain why only whole grains were related to lower blood pressure, according to Wang's team.

The findings, the researchers conclude, suggest that people may do their blood pressure and heart health some good by replacing refined-grain foods with whole grains.