Folic acid and prevention of colorectal adenomas: a combined analysis of randomized clinical trials

Int J Cancer. 2011 Jul 1;129(1):192-203. doi: 10.1002/ijc.25872. Epub 2011 Apr 1.


Observational data suggest that lower folate status is associated with an increased risk of colorectal neoplasia, implying that folate may be useful as a chemopreventive agent. We conducted a combined analysis of three large randomized trials of folic acid supplementation for the prevention of metachronous adenomas in patients with an adenoma history. Participants included 2,632 men and women who had a history of adenomas randomized to either 0.5 or 1.0 mg/day of folic acid or placebo and who had a follow-up endoscopy 6 to 42 months after randomization [mean = 30.6 (standard deviation = 8.1) months]. We used random-effects meta-analysis to estimate risk ratios (RRs) and 95% confidence intervals (CIs). The RR comparing folic acid versus placebo was 0.98 (95% CI = 0.82-1.17) for all adenomas and 1.06 (95% CI = 0.81-1.39) for advanced lesions. Folic acid was associated with a nonsignificant decreased risk of any adenoma among subjects in the lowest quartile of baseline plasma folate (≤ 11 nmol/L) and no effect among individuals in the highest quartile (> 29 nmol/L, p for trend = 0.17). There was a nonsignificant trend of decreasing risk of any adenoma associated with folic acid supplements with increasing alcohol intake. During the early follow-up reported here, more deaths occurred in the placebo group than in the folic acid group (1.7% vs. 0.5%, p = 0.002). In conclusion, after up to 3.5 years of folic acid use, there is no clear decrease or increase in the occurrence of new adenomas in patients with a history of adenoma.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenoma / drug therapy*
  • Aged
  • Colorectal Neoplasms / drug therapy*
  • Female
  • Folic Acid / adverse effects
  • Folic Acid / blood
  • Folic Acid / therapeutic use*
  • Humans
  • Male
  • Middle Aged
  • Placebos
  • Randomized Controlled Trials as Topic*


  • Placebos
  • Folic Acid