Young women who consumed more than 800 micrograms of folate per day reduced their risk of developing high blood pressure by almost a third compared to those who consumed less than 200 ug/day, said researchers at a special conference on high blood pressure in the US.
Most of those in the highest category of folate were boosting their intake with folic acid supplements, demonstrating the additional value of supplementing with the vitamin.
About two thirds of strokes and half the incidence of heart disease are attributable to raised blood pressure, according to the World Health Organisation. Worldwide, high blood pressure is estimated to cause 7.1 million deaths, about 13 per cent of the total and about 4.4 per cent of the total chronic disease burden.
The researchers used data from more than 95,000 women collected during the Nurses Health Study to compare quintiles of folate intake with blood pressure in two age groups -- women from 26-46 years old, and 43-70 years old. None of the women had a history of high blood pressure when the study started.
The most dramatic effects were seen among the younger group, where those with the highest intake of folate, (more than 800 ug/day, including that from supplements), showed a 29 per cent lower risk for high blood pressure than those in the lowest quintile (consuming less than 200 ug/day of folate).
Older women who had total folate intake of 800 ug/day had a 13 per cent lower risk.
Folate is found in citrus fruits, tomatoes, leafy green vegetables, kidney beans and grain products. It has been shown to reduce levels of homocysteine, a blood component that can damage blood vessels, and it may also help blood vessels relax, improving blood flow, said John P. Forman, 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 other factors such as exercise, salt intake and diet, which are known to influence risk of high blood pressure.
Researchers also looked at the independent effect of supplemental folic acid by analyzing the subset of women with very low dietary intake of folate. The younger women who consumed 800 ug/day or more of folate (comprised primarily of supplemental folic acid) had a 48 per cent reduction in hypertension risk compared to those whose folate intake was less than 200 ug/day (and who did not take supplements).
"It is very hard to get (800 micrograms folate daily) from diet alone," Forman told a Reuters Health report. "Essentially all the women in the highest category took supplements."
In the US, wheat flour has been fortified with folic acid since 1998 but Europe has been reluctant to follow the example, despite increasing evidence of the benefits not only to newborns but also the heart health of adults.