Cancer risk with folic acid supplements: a systematic review and meta-analysis

Study answer

What this study found

Overall, folic acid supplementation showed a borderline increase in cancer incidence in randomized trials and no clear reduction in cancer risk. Total cancer incidence was RR 1.07 (95% CI 1.00 to 1.14) across 10 RCTs, and prostate cancer incidence was significantly higher at RR 1.24 (1.03 to 1.49) across 6 RCTs. Cancer mortality was not significantly increased overall: RR 1.09 (0.92 to 1.30) across 6 RCTs. Observational studies did not show an overall difference in cancer incidence, but subgroup sensitivity analyses suggested higher mortality in studies with >30% smokers, higher folic acid…

Study & population

Systematic review and meta-analysis of randomized controlled trials and controlled observational studies in adults taking folic acid supplements.

Intervention

Oral folic acid supplementation, generally as tablets, at doses of at least 0.4 mg/day across the included trials.

Key limitation

Evidence came largely from highly selected trial populations, limiting generalizability to broader groups such as women of childbearing age.

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Original abstract