Folic acid occurs naturally in substances such as orange
juice and leafy green vegetables and is added to some products,
but only high-dose supplements seem to affect blood pressure,
the report said.
"This is the first major study to show an association
between folate intake and prevention of high blood pressure,"
said John Forman, a physician and researcher at Brigham and
Women's Hospital in Boston who led the study.
"While the findings are encouraging, we are not yet ready
to recommend that women start increasing their folate intake
until more research is conducted," he added.
The study, published in this week's Journal of the American
Medical Association (news - web sites), was based on data from thousands of nurses
whose health histories were tracked for years.
Among 93,803 women aged 27 to 44, those who consumed at
least 1,000 micrograms a day of total folate -- in foods and
supplements -- had a 46 percent decreased risk of hypertension
compared with those who consumed less than 200 micrograms a
day, the study found.
In a second group of 62,260 women aged 43 to 70, those with
a high total folate intake had an 18 percent reduced risk of
hypertension, it added.
None of those studied had a history of high blood pressure
when the study started. It also was not known if the supplement
would help men.
For women in the study who did not use any folic acid
supplements, getting the substance from foods alone failed to
lower the risk of high blood pressure, the study found.
Folic acid supplements of at least 400 micrograms per day
are recommended for women before and during pregnancy to
prevent neural tube defects, severe fetal growth problems
afflicting the brain and spinal cord that often result in
stillbirths.
Forman said the substance may help women reduce their risk
of developing high blood pressure because of it relaxes blood
vessels and eases blood flow.
"The prospect that folate has the potential to protect
against high blood pressure is exciting given that the vitamin
is both readily available and safe," he said. "The next step
will be a randomized controlled trial comparing women given
either folic acid supplements or placebo."
