TUESDAY, May 6, 2008 (HealthDay News) -- Folic acid and vitamin B supplements aimed at reducing blood levels of the amino acid homocysteine did not protect women against heart disease and stroke, a long-term study found.
It's the latest of several trials to douse the hope that lowering homocysteine levels could reduce the incidence of cardiovascular disease, said study lead author Dr. JoAnn Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital in Boston.
"To our knowledge, this is the trial with the longest follow-up," Manson said. "And to date, it is the largest study of women."
The trial also included a large number of women without cardiovascular disease, she said. Most earlier studies concentrated on people who already had had a heart attack, stroke or other cardiovascular problem.
The new findings were published in the May 7 issue of the Journal of the American Medical Association.
The trial included more than 5,400 U.S. women who were health professionals. Some had a history of cardiovascular disease, and others had three or more coronary risk factors, such as high blood pressure, obesity or diabetes. Half of the women took a daily combination pill containing 2.5 milligrams of folic acid, 50 milligrams of vitamin B6, and 1 milligram of vitamin B12, while the other half took a placebo.
Over the next 7.3 years, 14.9 percent of the women taking the active pill had a cardiovascular event, such as a heart attack or stroke. The incidence of such events in the women taking the inactive pill was almost the same -- 14.3 percent.
There still are ongoing trials, all stimulated by past studies suggesting an association between high blood levels of homocysteine and cardiovascular disease. But the latest results "cast further doubt on the hypothesis that lowering homocysteine prevents cardiovascular events," Manson said. "Folic acid supplements should not be used for the express purpose of preventing cardiovascular events."
The supplements do have their uses, Manson was quick to add. Folic acid is known to prevent birth defects that affect a baby's brain and spine. "We strongly recommend that women who might become pregnant take additional folic acid supplements," she said.
Manson used the word "additional," because bread and other grain products in the United States and other developed countries are fortified with folic acid. Natural sources of folic acid include green leafy green vegetables and citrus fruits.
Supplements could be recommended routinely for people in countries where no such fortification is done, said Dr. Eva Lonn, professor of medicine at McMaster University in Hamilton, Ontario, Canada, who wrote an accompanying editorial in the journal.
"But what we have learned from the trials in North America, where folic acid is added to flour products, is that there is no role for homocysteine screening or treatment in cardiovascular disease," Lonn said.
Some studies have indicated that folic acid supplements might protect against Alzheimer's disease, she said. "But they aren't conclusive," she added. "We need randomized trials with hard endpoints."
A woman's guide to folic acid is offered by the U.S. National Women's Health Information Center.