The vitamins quite effectively lowered homocysteine levels, the researchers reported at the American College of Cardiology meeting. It's just that lowering the levels did nothing to prevent myocardial infarction, death from cardiovascular causes, or other major outcomes, results showed in the HOPE-2 trial.

The HOPE-2 (Heart Outcomes Project Evaluation) study evaluated a combination of folic acid and vitamins B6 and B12 versus. placebo in more than 5,000 patients and found that there was no difference in the risk of death from cardiovascular causes, reported Eva Lonn, M.D., of Hamilton General Hospital in Hamilton, Ontario, and colleagues.

The results echoed those of a separate study conducted by Norwegian researchers and reported at the 2005 European Society of Cardiology conference in Stockholm.

The Norwegian Vitamin (NORVIT) trial compared various combinations of B vitamins and folic acid with placebo in nearly 3,800 patients, and found that treatment with B vitamins did not lower the risk of recurrent cardiovascular disease after acute myocardial infarction, and that there might even be a harmful effect from combined B vitamin treatment, reported Kaare Harald Bønaa, M.D., Ph.D., of the University of Tromso and NORVIT colleagues.

Results of the HOPE-2 and NORVIT studies were published simultaneously in the online edition of the New England Journal of Medicine.

"We have been often derailed in our efforts to implement secondary prevention adequately, and the focus should instead be on what has been proven to work," Dr. Lonn said, "namely a healthy lifestyle, including fruits and vegetables, exercise, and for those who already have an event, certain drugs such as aspirin, statins, beta blockers and ACE-inhibitors which have proven benefit."

In the HOPE-2 study, researchers from Canada, the United States, and Sweden randomly assigned 5,522 patients 55 and older who had vascular disease or diabetes, to daily treatment for an average of five years with either a vitamin combination or placebo. The combination consisted of 2.5 mg of folic acid, 50 mg of vitamin B6, and 1 mg of vitamin B12. The primary study outcome was a composite of death from cardiovascular causes, myocardial infarction, and stroke.

The authors concluded that B vitamins don't lower the risk of recurrent cardiovascular disease after acute myocardial infarction, and that the combined B vitamins could be harmful.

"What, then, can we conclude from the results of these trials?" asked Joseph Loscalzo, M.D., Ph.D., of Brigham and Women's Hospital and Harvard Medical School, in an accompanying NEJM editorial.

"Clearly, folic acid, vitamin B12, and vitamin B6 are not the therapeutic solution expected, and they do not provide a preventive benefit in patients with mild hyperhomocysteinemia.