Trials using a combination of vitamins B6, B12 and B9 (folic acid) were not helpful in reducing the risk of cardiovascular events, a new scientific review reports.
The review, which has been criticized by experts, included eight randomized controlled trials (equivalent to 24,210 subjects) investigating the use of B-vitamins as supplements for reducing the risk of heart attack, stroke or death associated with cardiovascular disease by lowering homocysteine levels (1).
Certain B vitamins, specifically B12, B9 (folic acid) and B6, influence levels of an amino acid in the blood called homocysteine. High levels of this molecule (above 15 micromoles/liter) are associated with an increased risk of heart disease. It has been suggested that giving B vitamin supplements could help regulate levels of homocysteine, thereby reducing the risk of cardiovascular disease and death. To date, there is significant body of scientific literature to demonstrate that there is a link between B vitamins and a reduced risk of cardiovascular mortality.
The review showed that the B vitamin supplements did not reduce the risk of developing or dying from heart disease. However, experts criticized that among the studies in the review that measured the blood homocysteine levels only at the beginning of the study and after B vitamins intake (only five of the eight studies), there was only moderate elevation in homocysteine level (mean of 12.4 micromoles/liter), which has not been associated with an increased risk of heart disease (2).
Furthermore, experts commented that the subjects were not homogenous in their health status. Their cardiovascular risk conditions were different: some had already established cardiovascular disease (CVD), others were only at risk of CVD. In addition, varying doses of vitamin B9 (folic acid), B6 and B12 were administered across the different studies.
A further study which could add value to the body of scientific knowledge would be a primary prevention study on people without pre-existing cardiovascular disease.