2 B Vitamins Found to Cut Women’s Heart Disease
Women who consume more than the recommended dietary allowances of folic acid and vitamin B-6 appear to cut their heart disease risk nearly in half, according to a 14-year Harvard study of 80,000 healthy middle-age women.
The difference in heart disease risk between the highest and lowest intakes of the vitamins was comparable to that between smokers and nonsmokers, said the lead author, epidemiologist Eric Rimm of the Harvard School of Public Health. Put another way, he said, the heart disease risk of women with the lowest intake of the vitamins was equivalent to being 40 to 50 pounds overweight.
The researchers classified the women into five groups based on their intake of folic acid, a type of B vitamin, estimated from multiple dietary questionnaires. Among women with the highest intakes of the two vitamins, heart disease was 45% less common than among women with the lowest intakes.
Unpublished data from a large, separate study of men by the Harvard group found similar results, Rimm said. Heart disease is the No. 1 killer of men and women in the United States.
“This is potentially very significant in terms of public health,” said Sonia Skarlatos, a nutrient expert at the National Heart, Lung and Blood Institute.
The American Heart Assn. said the findings were “intriguing,” but in a statement urged “caution before we consider the results of this study conclusive.”
The new study, released today in the Journal of the American Medical Assn., adds the two vitamins to a list of nutrients, such as vitamin E and dietary fiber, that have been shown to prevent or delay heart disease in some people.
In fact, the protection offered by the relatively high folic acid and vitamin B-6 levels documented in this study is greater than the heart benefit attributed to any single nutrient, Rimm and other researchers said.
It also lends support to the emerging theory that elevated levels of an amino acid called homocysteine plays a role in heart disease. Because both folic acid and vitamin B-6 help break down homocysteine, that may be the reason for the vitamins’ benefit, the researchers said. Still, as others pointed out, the study falls short of proving that, because the women’s homocysteine levels were not measured.
Moreover, the folic acid and vitamin B-6 levels that conferred the greatest heart benefit were at least three times higher than the federal government’s current RDAs, which were set in 1989.
The women on high-vitamin diets got an average of 700 micrograms a day of folic acid, or folate, whereas the RDA is 180. And they took in an average of 4.6 milligrams of B-6 a day, nearly three times the recommended allowance of 1.6 milligrams.
The researchers suggest that the RDAs for folic acid and vitamin B-6 should perhaps be raised to provide maximum protection. The federal government is expected to review RDAs for those vitamins in April, Rimm said.
The study is expected to fuel the scientific debate over the wisdom of taking vitamin supplements. Many health researchers have argued strongly against doing so, saying the evidence for benefits is scanty and people can get all the vitamins they need in food, along with other healthful ingredients such as fiber.
However, in the new study, 94% of women in the group with the lowest heart disease risk took a multiple vitamin supplement four to seven times a week, compared to 8% of the women in the higher risk group. But there also appeared to be too much of a good thing, the researchers found: Women who took two or more multiple vitamins achieved no heart benefit.
The findings represent another triumph of sorts for folic acid. Pregnant women are now urged to take at least 400 micrograms daily to help prevent severe birth defects such as spina bifida. This year, the Food and Drug Administration began requiring that flour be enriched with 100 micrograms of folic acid per 100 grams of grain products to reduce the incidence of such birth defects.
“Even after fortification,” the researchers wrote, “only 25% of adult women will have dietary folate intakes above 400 micrograms per day.”
“It’s not easy to get the kinds of levels of folic acid [seen in the study] from food sources alone,” said Shirley Beresford, an epidemiologist at the University of Washington School of Public Health who has analyzed data on folic acid and homocysteine. Some researchers have suggested raising the folic acid RDA to 400 micrograms a day. “The easiest way to achieve that is to take one multivitamin supplement a day containing some folic acid.”
In the body, folic acid is essential to the manufacture of red blood cells and the maintenance of DNA and cell division. Foods rich in the vitamin include green leafy vegetables such as spinach, legumes, citrus fruits, poultry and liver. Excessive consumption of the vitamin can, however, trigger convulsions in epileptics.
Vitamin B-6 also maintains red blood cells, facilitates breakdown of carbohydrates and promotes nerve function. Good sources are spinach, meats, fish, poultry, potatoes, bananas and prunes. But excess intake can lead to sensory nerve damage.
Intriguingly, Rimm said, the lowest heart disease rate was among women who regularly drank moderate amounts of alcohol in addition to consuming high vitamin levels. Their risk was reduced 80%, compared to women who consumed the least vitamins and did not drink, he said.
