title: Efficacy of Vitamin C Supplements in Prevention of Cancer: A Meta-Analysis of Randomized Controlled Trials.
abstract: BACKGROUND
  Previous randomized controlled trials (RCTs) have reported inconsistent findings regarding the association between vitamin C supplementation and the risk of cancer.
  
  
  METHODS
  We performed a meta-analysis of RCTs to investigate the efficacy of vitamin C supplements for prevention of cancer. We searched the PubMed, EMBASE, and Cochrane Library databases in November 2014 using common keywords related to vitamin C supplements and cancer.
  
  
  RESULTS
  Among 785 articles, a total of seven trials were identified, which included 62,619 participants; 31,326 and 31,293 were randomized to vitamin C supplementation and control or placebo groups, respectively, which were included in the final analysis. A fixed-effects meta-analysis of all seven RCTs revealed no significant association between vitamin C supplementation and cancer (relative risk, 1.00; 95% confidence intervals, 0.95-1.05). Similarly, subgroup meta-analysis by dose of vitamin C administered singly or in combination with other supplements, follow-up period, methodological quality, cancer mortality, gender, smoking status, country, and type of cancer also showed no efficacy of vitamin C supplementation for cancer prevention.
  
  
  CONCLUSIONS
  This meta-analysis shows that there is no evidence to support the use of vitamin C supplements for prevention of cancer.
authors.affiliation: Huntington University, Huntington, USA. ; Loma Linda University School of Medicine, Loma Linda, CA, USA (Present).
authors.forename: Bobae
authors.initials: B
authors.lastname: Lee
authors.affiliation: Department of Family Medicine, Healthcare System Gangnam Center, Seoul National University Hospital, Seoul, Korea.
authors.forename: Seung-Won
authors.initials: SW
authors.lastname: Oh
authors.affiliation: Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, Goyang, Korea. ; Department of Family Medicine and Center for Cancer Prevention and Detection, National Cancer Center, Goyang, Korea.
authors.forename: Seung-Kwon
authors.initials: SK
authors.lastname: Myung
keywords: Ascorbic Acid; Cancer; Meta-Analysis; Randomized Controlled Trials; Vitamin C