Young women who consume more than 800 micrograms of folate per day can reduce their risk of developing high blood pressure by almost a third compared to those who consume less than 200 mcg/day, according to new research presented at the American Heart Association’s 58th Annual High Blood Pressure Research Conference.

Folate also reduced the risk in older women to a lesser degree.

Folic acid is the synthetic form of folate. Since January 1998, wheat flour has been fortified with folic acid to add an estimated 100 mcg/day to the average diet.

Researchers studied more than 150,000 women to determine if there was a link between risk of high blood pressure and their level of folate intake, including supplements. Folate intake was examined in quintiles. They studied women in two age groups -- 26-46 years old, and 43-70 -- and found the most dramatic effects among the younger group.

Younger women in the highest folate intake quintile who consumed more than 800 mcg/day) of total folate (dietary intake plus supplements) had a 29 percent lower risk for high blood pressure than those in the lowest quintile (consuming less than 200 mcg/day). Older women who had total folate intake of 800 mcg/day had a 13 percent lower risk.

Folate has been shown to reduce levels of homocysteine, a blood component that can damage blood vessels. Folate also may help blood vessels relax, improving blood flow, said John P. Forman, M.D., lead author of the study and a research and clinical fellow at Brigham and Women’s Hospital in Boston.

The benefit of folate was independent of such other factors as exercise, salt intake and diet, which are known to influence risk of high blood pressure.

Forman and colleagues based their finding on data collected in two large studies of women -- the Nurses’ Health Study I, which includes 62,260 women, ages 43-70, and the Nurses’ Health Study II, which includes 93,034 women, ages 26-46. None of the women had a history of high blood pressure when the study started.

Using questionnaires, the researchers gathered information about dietary and supplemental folate intake prior to the study, then followed up with additional questionnaires every four years. Information about physician-diagnosed high blood pressure was self-reported on health status questionnaires every two years during eight years of follow-up.

The researchers collected data on body mass index; exercise; smoking; family history of hypertension; salt; calcium, magnesium and potassium intake; fiber intake; methionine intake; caffeine and alcohol consumption; and use of vitamins B6, B12 and D.

The Food and Drug Administration began requiring folate supplementation of several foods, including cereals and bread, in 1998. But, fortification began in 1996, spanning the last two years of the NHS I and the last three years of the NHS II.

Researchers also looked at the independent effect of supplemental folic acid by analyzing the subset of women with very low dietary intake of folate. Women in NHS II who consumed 800 mcg/day or more of folate (comprised primarily of supplemental folic acid) had a 48 percent reduction in hypertension risk compared to those whose folate intake was less than 200 mcg/day (and who did not take supplements). Women in NHS I had a 40 percent reduction.

The co-authors of the study are Eric B. Rimm, Sc.D.; Meir J. Stampfer, M.D., Dr. P.H.; and Gary C. Curhan, M.D., Sc.D.