The use of folic acid supplements does not appear to be associated with reduced rates of cardiovascular events, cancer or death over a five-year period, a new meta-analysis has shown.
High rates of cardiovascular disease in children with homocystinuria-a rare genetic condition causing extreme elevations in homocysteine levels-led researchers to hypothesize that moderate increases in blood homocysteine levels may increase cardiovascular disease risk in the general population.
Supplementation with B vitamins, and in particular folic acid, lowers blood homocysteine levels and reduces cardiovascular disease risk among individuals with homocystinuria.
Robert Clarke, F.R.C.P., University of Oxford, England, and colleagues conducted a study of 37,485 participants, out of which 18,723 were assigned to take folic acid in doses ranging from 0.8 milligrams per day to 40 milligrams per day.
The other 18,762 took placebo or an equivalently small dose of folic acid. Trials continued for a median (midpoint) of five years.
9,326 had a major vascular event during the treatment period, 3,010 developed cancer and 5,125 died. Overall, there was a 25 percent reduction in homocysteine levels associated with active folic acid supplementation. However, those who took folic acid were no less likely to have a major heart or blood vessel event than those who took placebo.
"The randomized trials in the present meta-analysis found no evidence of benefit with treatment continued for more than five years. Although some benefit might emerge with even longer treatment and follow-up, the trial results give no reason to expect this (particularly because cardiovascular benefits tend to emerge within just a few years with other cardioprotective treatments, such as antihypertensives or statins)," the authors wrote.
The study appears in the October 11 issue of Archives of Internal Medicine.