Whole-grain diets may help reduce blood pressure

Diets with increases whole-grain foods, high in soluble or insoluble fiber, are associated with a reduction in blood pressure in individuals with slightly elevated cholesterol, according to researchers in Maryland.

Dr. Kay M. Behall and colleagues from the U.S. Department of Agriculture, Beltsville, examined the effects on blood pressure of whole-grain diets containing insoluble fiber (whole wheat and brown rice) and soluble fiber (barley).

Seven men, nine premenopausal women, and nine postmenopausal women, all with mildly high cholesterol, were put on the controlled Step I American Heart Association diet for 2 weeks.

After that, refined carbohydrates in the Step I diet were replaced with whole-grain foods. Two types of whole-grain diets - whole wheat/brown rice, barley, or half wheat-rice/half barley) were each consumed for 5 weeks.

Blood pressure was measured weekly and weight was measured daily before breakfast. Results of the study are published in the September issue of the Journal of the American Dietetic Association.

Blood pressure decreased significantly during the all whole-grain diets. Systolic blood pressure, the top reading, declined by 2.2 mm Hg when the subjects consumed the Step I diet and declined by an additional 1.4 to 6.7 mm Hg while subjects consumed the whole-grain diets, Dr. Behall's team reports.

Diastolic blood pressure, the lower reading, declined by 2 mm Hg on the Step I diet and was reduced an additional 2.9 to 3.7 mm Hg when whole-grains were added.

Among the men, the greatest reduction in arterial pressure was observed during the half-and-half diet, while the greatest reduction in arterial pressure for women occurred during the diet with barley. Postmenopausal women were the least responsive.

Subjects lost about 1 kg during the course of the study, a significant difference. Compared to the Step I diet, calorie levels were significantly higher during all whole-grain diets.

"Increasing whole-grain foods, whether high in soluble or insoluble fiber, can reduce blood pressure and may help control weight," the researchers conclude.

SOURCE: Journal of the American Dietetic Association, September 2006.