That's the conclusion of a new study that could influence whether the nation's leading heart doctors recommend taking it to ward off cardiovascular disease.
A two-decade study of nearly 10,000 American adults finds people whose diet included at least 300 micrograms of the B vitamin daily had a 20 percent lower risk of stroke than those consuming less than 136 micrograms a day, says a report in tomorrow's issue of Stroke."Our study supports the recommendation to consume at least 400 micrograms of folate a day," says study author Lydia A. Bazzano, a research fellow at the Tulane School of Public Health in New Orleans.
The report solidifies the evidence that dietary folate, also known as folic acid, can reduce the risk of stroke, says Dr. Scott Kasner, director of the stroke center at the University of Pennsylvania Medical Center and author of an accompanying editorial.
"This is confirmatory evidence of what was found in earlier studies," Kasner says. "The thing that is new here is that it is a larger study that is more representative of the population of the United States."
The study is based on reports by participants in the long-running National Health and Nutrition Examination Survey. Data on their dietary intake of folate has been collected since 1982, and detailed records have been kept of their general health and the incidence of heart attack and stroke.
After adjusting for a large number of factors that could affect the risk of stroke -- diabetes, blood pressure, physical activity, smoking -- the researchers report that dietary intake of folate was related to the risk of both heart attacks and stroke. A higher intake of folate was associated with a lower risk of stroke for men and women, regardless of their level of physical activity and smoking habits.
"People should be aware of the amount of folate in their diet," Bazzano says.
Foods rich in folate include citrus fruits, tomatoes, leafy vegetables, beans and grain products. Also, wheat flour has been fortified with folate by order of the U.S. Food and Drug Administration since 1998 because a low-folate diet is linked to an increased risk of birth defects of the spinal cord. A daily intake of 600 micrograms is advised during pregnancy.
The link between folate and cardiovascular disease is homocysteine, an amino acid that has been linked to a higher risk of atherosclerosis, the hardening of the arteries that leads to heart attack and stroke. Folate has been found to reduce blood levels of homocysteine.
The American Heart Association is considering whether to add homocysteine to the list of risk factors for cardiovascular disease, alongside such things as LDL cholesterol.
The association doesn't recommend the widespread use of folate to prevent strokes and heart disease, partly because doctors aren't yet convinced that your risk is reduced because of a high folic acid intake. However, a study of this size could tip the scales.
Studies are under way to determine whether higher doses of folate than are now recommended would be even more beneficial, Kasner says. "The studies that are looking at it include patients who have had heart attacks and strokes," he says.
So far, no side effects linked to excess intake of folate have been detected, Kasner adds.
"There seems to be no downside," he says. "Any excess should be cleared easily from the body."
What To Do
"This study suggests that doctors screen patients' dietary folate levels, and promote the recommended intake," Bazzano says.
You can learn more about the homocysteine/folate connection from the American Heart Association. The Arizona Department of Nutrition Services also has information on folic acid, including a list of foods rich in the vitamin.