High Folate Intake Is Associated With Reduced Risk of Hypertension in Women
A study showing that high folate intake in women is associated with a decreased risk of hypertension, especially in younger women, which was first presented at the 58th Annual Fall Conference of the High Blood Pressure Council of the American Heart Association in Chicago last year, has now been published in the January 19 issue of JAMA . Researchers from Brigham and Women's Hospital and Harvard School of Public Health (Boston, Massachusetts), who carried out the study, recommend that clinical studies of folic acid supplementation as a means of lowering blood pressure and reducing risk be carried out in young women. Such studies may have important public health implications, they believe. In the United States, it is recommended that all women of childbearing age (15-45 years) take 400 mcg/day of synthetic folic acid to prevent birth defects.
The Boston researchers used data from 2 prospective cohort studies: Nurses' Health Study II (NHS II), carried out between 1991 and 1999 in 93,803 women aged 27-44 years, and Nurses' Health Study I (NHS I) carried out between 1990 and 1998 in 62,260 women aged 43-70 years. At the start of each study, all participants provided information on dietary folate and supplemental folic acid intake using a semiquantitative food frequency questionnaire. This information was updated every 4 years.
None of the participants included in either study had a history of hypertension. On biennial questionnaires, a total of 7373 younger women (NHS II) and 12,347 older women (NHS I) reported having hypertension (diagnosed by a clinician). Among the younger women, those who consumed ≥ 1000 mcg/day folate had a 46% lower risk of hypertension than those who consumed < 200 mcg/day ( P < .001). Among the older women, the reduction in the risk of hypertension was 18% in those taking ≥ 1000 mcg/day of folate compared with those who took < 200 mcg/day. The women with a folate intake of > 1000 mcg/day had a 40% reduction in the risk of hypertension compared with women who were taking less than the US daily recommended dose of 400 mcg.
All of the results remained essentially unchanged after adjustment for potential confounding factors such as age; ethnicity; family history; BMI; physical activity; smoking; intakes of alcohol, caffeine, sodium, potassium, calcium, magnesium, fiber, methionine, and vitamins B6, B12, C, and D, cholesterol, and fat; and drugs such as nonsteroidal anti-inflammatory drugs (NSAIDs).
Compared with women with a low dietary folate intake (< 200 mcg/day), younger and older women with total folate intake ≥ 800 mcg/day had a 45% and 39% reduction, respectively, in the risk of hypertension. Among the total 98,828 women who did not take any folic acid-containing supplements at all, however, those with a dietary folate intake of ≥ 400 mcg/day had no significant reduction in hypertension risk compared with those whose intake was < 200 mcg/day. The researchers suggest several possible reasons for these results: few participants in the study had a high dietary intake of folate; folic acid supplements have a higher bioavailability than naturally occurring folate; and, during the study period in the United States, fortification of various foods was being introduced, which may have led to some misreporting of folate intake.
This is the first study to show that higher folate intake could lower the risk of developing hypertension, according to lead researcher John P. Forman, MD (Brigham and Women's Hospital). He and his co-investigators do not suggest a mechanism for this effect, but note that many studies have shown that supplemental folic acid improves endothelial function in vivo.
The Boston study was published a few days before a "National Folic Acid Awareness Week" was launched in the United States. Running from January 24-30, 2005 and organized by the National Council on Folic Acid, its aim was to encourage all women of childbearing age to take the recommended daily dose of folate (400 mcg). It is estimated that two thirds of women in this age group do not consume enough folic acid.
Medscape Cardiology. 2005;9(1) © 2005 Medscape
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