May 6, 2008 -- Folic acid and B vitamin supplements continue to prove that they can significantly lower blood levels of homocysteine, a major risk factor for cardiovascular disease, but when it comes to actually reducing heart disease and stroke, the combo appears to have no impact.
A study of more than 5,000 women at high risk for cardiovascular disease showed that daily folic acid (vitamin B-9) and vitamin B-6 and B-12 supplementation did not reduce the rate of cardiovascular events, despite lowering levels of the amino acid homocysteine. High levels of the amino acid have been linked to a higher risk of heart disease, stroke, and fatty deposits in the arteries.
The results, published in the May 7 issue of The Journal of the American Medical Association, uphold findings from previous studies.
For the study, Christine M. Albert, MD, MPH, of Brigham and Women's Hospital and Harvard Medical School, and colleagues randomly assigned female health professionals to either a placebo or a combination pill containing 2.5 milligrams of folic acid, 50 milligrams of vitamin B-6, and 1 milligram of vitamin B-12. The women were 42 years old or older with a history of cardiovascular disease or three or more heart disease risk factors.
Researchers followed the women for about seven years. Blood tests performed in a small subset of the women showed that women who received the supplements had an average 18.5% lower level of homocysteine than those who took the placebo.
However, the lower homocysteine level did not appear to sway the number of cardiovascular events. During the seven-year follow-up, 796 women had some type of cardiovascular event, including a heart attack, stroke, or death due to cardiovascular disease. Some women had more than one event.
There was no significant difference in the number of events between the two groups. Cardiovascular events occurred among 14.9% of those who received the folic acid/vitamin B supplements and in 14.3% of those who received the fake pill.
Researchers say the risk of death from any cause was also similar between the two groups.
"Our results are consistent with prior randomized trials performed primarily among men with established vascular disease and do not support the use of folic acid and B vitamin supplements as preventive interventions for [cardiovascular disease] in these high-risk fortified populations," the researchers write.
Folic Acid, B Vitamins Not Recommended for Heart
The American Heart Association does not recommend widespread use of folic acid and B vitamin supplements to reduce the risk of cardiovascular disease.
Because homocysteine levels were measured in only a small number of women, this study was not able to evaluate whether women with high homocysteine levels may have benefited to a greater extent.
In an accompanying editorial, Eva Lonn, MD, MSc, FRCPC, of McMaster University in Hamilton, Ontario, says folic acid and B vitamin supplements cannot be recommended for preventing heart disease and strokes, except in the case of rare genetic disorders.
"However, ongoing clinical research should provide further evidence on whether there may be any role for homocysteine-lowering B vitamin supplements in [cardiovascular disease] prevention and for the overall importance of homocysteine as a cardiovascular risk factor," she writes.