Taking B vitamins is unlikely to prevent heart attack and stroke in people who have heart disease or risk factors for heart disease, a new research review suggests.

The findings, based on eight clinical trials of more than 24,000 people, give added weight to current recommendations against using B vitamins as a way to prevent heart trouble.

The idea that B vitamins like folic acid, B-6 and B-12 might help prevent heart complications stems from the fact that they lower blood levels of an amino acid called homocysteine. Homocysteine levels are often elevated in people with atherosclerosis, a buildup of plaque in the arteries that can lead to heart attack and stroke.

However, researchers have not been sure whether high homocysteine levels actually contribute to atherosclerosis progression, or are merely a marker of heart risks. Suggesting the latter may be true, no clinical trial has proven that B-vitamin supplements prevent heart attack and stroke.

To help strengthen the evidence, the new review pulled together data from eight clinical trials testing the effects of folic acid, vitamin B-6, B-12 or some combination of the these supplements.

The trials involved 24,210 people with either established heart and blood vessel disease - atherosclerosis or a history of stroke, heart attack or other heart complications - or major risk factors for it, like diabetes, high blood pressure or High cholesterol.

Researchers found that adding the supplements to standard medical care did nothing to lower study participants’ risks of heart attack, stroke or death for up to seven years of follow-up.

The findings appear in the Cochrane Library, which is published by the Cochrane Collaboration, an international organization that evaluates medical research.

The review provides “strong evidence” that these B vitamins do not prevent heart problems and strokes, lead researcher Dr. Arturo J. Marti-Carvajal, of the Iberoamerican Cochrane Network in Valencia, Venezuela, told Reuters Health in an email.

His advice to people trying to protect their heart health is to forgo B vitamins in favor of proven tactics: stop smoking, exercise regularly, get regular tests of blood pressure, cholesterol and blood sugar, and eat a balanced diet rich in fruits and vegetables and low in fast food and other less-than-healthy fare.

SOURCE: Cochrane Library, online October 7, 2009.