Objectives Our purpose is to conduct an updated meta-analysis of relevant randomised controlled trials (RCTs) to estimate the effect of folic acid supplementation alone on endothelial function and plasma homocysteine concentration in patients with CAD.

Methods An extensive search of PubMed was used to identify RCTs comparing folic acid and placebo therapy. Mean difference (MD) with 95% confidence interval (CI) was performed as a measure of the association between folic acid supplementation and endothelial function/plasma homocysteine concentration.

Results Of 377 patients included, 191 underwent folic acid supplementation and 186 underwent placebo treatment. Compared with placebo group, folic acid supplementation alone had a significant efficacy on increasing flow-mediated dilation (FMD) (MD57.72 μm, 95%CI 50.14 to 65.31; P < 0.05) and lowering plasma homocysteine concentration (MD -3.66 μmol/l, 95%CI -5.44 to -1.87; P < 0.05; I² = 87%). There was no significant change in the response to end diastolic diameter (EDD), glyceryl-trinitrate (GTN) diameter change, heart rate, baseline and peak hyperaemic flow, systolic and diastolic blood pressure (BP) between folic acid and placebo groups (P > 0.05).

Conclusions This meta-analysis suggests that folic acid supplementation 5 mg daily for greater than 4 weeks significantly improve FMD and lower plasma homocysteine concentration in patients with CAD. However, RCTs are still needed to confirm current findings.