The scientific evidence is strong enough to justify using folic acid as a cheap and simple way of reducing heart disease and strokes, according to researchers.
That advice followed an analysis of the debate over whether raised homocysteine levels in the blood causes heart disease and stroke, and whether folic acid, which lowers homocysteine, will help reduce the risk of these disorders.
To clarify the analysis, UK cardiologists examined all the available evidence from different studies to see whether raised homocysteine is a cause of cardiovascular disease. Some studies looked at homocysteine and the occurrence of heart attacks and strokes in cohort studies, some focused on people with a common genetic variant which increases homocysteine levels in genetic studies, while others tested the effects of lowering homocysteine levels in randomised controlled trials.
The cohort studies and genetic studies yielded similar results, indicating a protective effect from lower homocysteine levels, even though they did not share the same sources of possible error. The randomised trials were too small to be conclusive although their results were consistent with the expected protective effects of folic acid.
The conclusion that homocysteine is a cause of cardiovascular disease explains the observations from all the different types of study, even if the results from one type of study are, on their own, insufficient to reach that conclusion, the cardiologists concluded. Since folic acid reduces homocysteine concentrations, it follows that increasing folic acid consumption will reduce the risk of heart attack and stroke.
They therefore take the view that the evidence is now sufficient to justify action on lowering homocysteine concentrations, although the position should be reviewed as evidence from ongoing clinical trials emerges.