Should we prescribe folic acid in MI?
Q Should MI patients be prescribed folic acid supplements?
AThe reason folic acid is thought to be of benefit is because it lowers plasma levels of the amino acid homocysteine.
Growing evidence suggests high plasma homocysteine is associated with a higher incidence of cardiovascular disease, possibly because hyperhomocysteinaemia is known to be toxic to the vascular endothelium, which leads to loss of vasodilator tone and enhanced pro-thrombotic activity.
Administration of folic acid, either alone or in combination with other B vitamins, effectively lowers plasma homocysteine concentrations, and so supplementation of coronary heart disease patients with folic acid has been proposed, particularly when plasma homocysteine exceeds 15µmol/l.
Concerning the dose of folate and other B vitamins to be administered, the debate is still open, as some individuals might need more than the currently recommended 400µg folate per day.
A recent Italian study showed supplementation of young patients who had recently suffered a myocardial infarction with high-dose folic acid (15mg per day for one month, followed by 15mg every two days for two months) reduced plasma homocysteine by 41 per cent and was associated with a significant improvement of endothelial function.
Definitive randomised controlled trials of folic acid supplementation are under way to establish whether the improvements in surrogate measures (plasma homocysteine, endothelial function) translate into clinical outcome benefits in patients with CHD and those who have suffered myocardial infarction.
Until the results are published all we can say is
that folic acid in this situation is unproven in terms of clinical benefit, but nevertheless is safe as long as vitamin B12 levels are checked first, since folic acid can cause complications in those patients deficient in vitamin B12.
Dr Albert Ferro, consultant in clinical pharmacology,
Guy's Hospital, London