BOSTON — Men who consume whole grain and bran may be increasing their chances of fighting off hypertension, according to a new study from researchers at Harvard that appeared in the September issue of the American Journal of Clinical Nutrition.
As part of the study, "Whole grains and incident hypertension in men," lead researcher Alan J. Flint, project director at the Harvard School of Public Health, analyzed data on 31,684 men who participated in the Health Professionals Follow-Up Study.
At the beginning of the study in 1986, none of the men had hypertension, cancer, stroke or coronary heart disease. During the 18 years of follow-up from 1986 to 2004, researchers found a total of 9,227 cases of hypertension.
Men in the highest quintile of whole grain intake (46 grams per day) accounted for 1,648 of the 9,227 hypertension cases and were deemed to be 19% less likely to develop high blood pressure compared with those men in the lowest quintile (3.3 grams per day), which accounted for 1,826 of the 9,227 cases. Meanwhile, the men in the highest quintile of bran intake (12 grams per day) were found to be 15% less likely to develop high blood pressure compared with those in the lowest quintile (0.3 grams per day).
The intakes of whole grains, bran and germ were calculated by determining the whole grain content of each grain food according to the dry weight of its whole grain ingredients. Nutrient profiles of the various grains were derived by using composite recipes, nutrient data from the U.S. Department of Agriculture, and product labels. For home prepared bakery items, cookbooks were used to estimate whole grain content.
The reasons for whole grain’s influence on hypertension are wide ranging, the researchers noted, including its ability to improve insulin sensitivity, reduce food intake and lower blood sugar.
"The current study is in a unique position to add to and expand the existing knowledge base on the relation between intake of whole grains and the risk of incident hypertension," the researchers said. "The true magnitude of the inverse association may be stronger than we estimated because of attenuation as a consequence of measurement error.
"There is a growing body of evidence from both observational epidemiologic studies and randomized clinical trials that diet influences blood pressure, particularly intakes of potassium and fiber, both of which are constituent compounds of whole grains."
The researchers said the inverse association between whole grain intake and hypertension was independent of other healthy lifestyle and diet factors, such as intake of sodium, alcohol, fruit and vegetables, as well as adjustment for physical activity, multivitamin use and cholesterol screening.