"There is no evidence to support the use of B-vitamins as supplements for reducing the risk of heart attack, stroke or death associated with cardiovascular disease," says Arturo Martí-Carvajal, of the Iberoamerican Cochrane Network in Valencia, Venezuela.
"And it is important to point out that although we may have not found a positive effect, these kinds of studies are vitally important for determining the factors that influence the risk of developing and dying from this disease, which is the number one cause of death in the world today," adds the lead researcher.
According to background information in the review, certain B-vitamins-specifically B12, B9 (folic acid) and B6-influence levels of an amino acid in the blood called homocysteine.
The report further states that high levels of this molecule are associated with an increased risk of heart disease.
The Cochrane researchers say that B-vitamin supplements have been considered to be helpful in regulating levels of homocysteine, and, thereby, in reducing the risk of cardiovascular disease and death.
However, they insist, there is no scientific basis for this claim.
The team's review included eight trials involving a total of 24,210 people, none of which individually supported the idea that giving B-vitamin supplements could prevent cardiovascular disease.
Together, the data showed that B-vitamin supplements, whether compared with placebos or standard care, had no effect on the incidence of heart attack, stroke or death associated with heart disease.
"Prescription of these supplements cannot be justified, unless new evidence from large high quality trials alters our conclusions. There are currently three ongoing trials that will help to consolidate or challenge these findings," says Marti-Carvajal.