TUESDAY, Jan. 18, 2005 (HealthDayNews) -- Women who take folic acid supplements during their childbearing years to prevent certain birth defects could also be doing themselves a favor by lowering their risk for high blood pressure.

Researchers from Brigham and Women's Hospital in Boston found that women who consumed high levels of the B vitamin from food and supplements significantly reduced their risk of developing hypertension.

"This is the first major study to demonstrate that higher folate intake may be able to lower the risk of developing high blood pressure," said Dr. John P. Forman, a Brigham and Women's researcher.

"This is especially exciting, given the safety and ready availability of folic acid supplements," added Forman, who is the lead author of the study appearing in the Jan. 19 issue of the Journal of the American Medical Association.

Preliminary results were presented last October at the American Heart Association's annual high blood pressure research conference in Chicago.

Forman cautioned that more research is needed to confirm the findings: "It is important to emphasize that our study, although providing evidence of the link between folate and blood pressure, is not proof that folate can be used clinically to lower blood pressure." A large randomized, controlled trial involving women treated with folic acid supplements or a placebo is needed to confirm the findings before any recommendations could be made, he said.

Dr. Norman M. Kaplan, a clinical professor in the hypertension division at the University of Texas Southwestern Medical Center in Dallas, agreed. It's a good study. The problem is that it is observational, as opposed to a more rigorous prospective study comparing outcomes of people taking folate with a control group, he said.

"They clearly took more folate, but we have no idea what else they did," Kaplan noted.

Hypertension affects an estimated 65 million Americans and many more individuals worldwide. Because it typically strikes without symptoms, it is often called the "silent killer." But treatment is critical because elevated blood pressure puts people at increased risk of cardiovascular disease and renal failure.

Folate, also known as folic acid, is necessary for proper cell growth and is thought to lower blood pressure by improving blood vessel function. Folic acid supplements are widely recommended to women who are pregnant or trying to become pregnant. Studies show folate can decrease the risk for neural tube birth defects such as spina bifida. In addition to supplements, good dietary sources of folate include leafy green vegetables, such as spinach and turnip greens, fruits, dried beans and peas.

To see whether there was a link between folate intake and blood pressure, the authors evaluated detailed dietary and health information for more than 150,000 women over eight years. One group included 62,260 women aged 43 to 70 from the Nurses' Health Study, a prospective study of the risk factors for major chronic disease in women. The other group included 93,803 women, aged 27 to 44, from the Nurses' Health Study II, which involves younger women.

Among younger women who consumed at least 1,000 micrograms per day of folate from dietary and supplemental sources, there was a 46 percent reduction in risk of hypertension compared to women whose folate intake was less than 200 micrograms per day. Older women had an 18 percent reduction in risk of hypertension.

Women who consumed a low amount of folate from foods -- less than 200 micrograms per day -- but still managed to achieve a total daily folate intake of more than 800 micrograms through supplementation also lowered their risk of developing hypertension. Younger women reduced their risk by 45 percent; older women cut their risk by 39 percent.

Among women who did not use supplements, folate from foods alone did not lower their risk of high blood pressure, the study found.

Why younger women achieved a greater benefit isn't clear. It's possible that a young woman develops high blood pressure for a very different reason than an older woman and that folate may be more important for one reason or another, Forman explained.

But the authors stopped short of recommending that women boost their folate intake. So what dietary change can they make to avoid high blood pressure?

"The bottom line is people should eat a good diet. They should eat lots of fruits and vegetables, just like their grandmother told them," Kaplan advised.

More information

The Office of Dietary Supplements at the National Institutes of Health can tell you more about folate.

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