Research part-funded by the British Heart Foundation (BHF) has revealed that folic acid supplements do not prevent heart disease.
The supplements have been linked with lowering the levels of the homocysteine amino acid, but there is no evidence that this relationship can reduce heart and circulatory events such as heart attacks or strokes.
Ellen Mason, senior cardiac nurse for the BHF, said: "Folic acid remains a must for women trying to conceive and in their first trimester because it reduces the chance of a neural tube defect such as spina bifida. But this study concludes the supplement does not protect against heart and circulatory disease.
"Although folic acid supplements can reduce levels of homocysteine, researchers found this did not translate into a significant reduction in heart and circulatory events such as heart attack or stroke. In fact, it didn't reduce death rates from any cause.
"Adding folic acid to bread in the US to reduce neural tube defects has not shown a significant reduction in heart attacks, strokes, or deaths from heart and circulatory disease, but it hasn't caused any adverse increases in these conditions either, which is reassuring for the public.
"People should continue to get vitamins and minerals from a healthy balanced diet unless they're advised to take supplements by their doctor or registered dietitian."
The research has been published in the Archives of Internal Medicine.