title: Effect of vitamin B supplementation on cancer incidence, death due to cancer, and total mortality: A PRISMA-compliant cumulative meta-analysis of randomized controlled trials.
abstract: BACKGROUND
  Observational studies have suggested that vitamin B supplementation is associated with cancer risk, but this association remains controversial. A pooled data-based meta-analysis was conducted to summarize the evidence from randomized controlled trials (RCTs) investigating the effects of vitamin B supplementation on cancer incidence, death due to cancer, and total mortality.
  
  
  METHODS
  PubMed, EmBase, and the Cochrane Library databases were searched to identify trials to fit our analysis through August 2015. Relative risk (RR) was used to measure the effect of vitamin B supplementation on the risk of cancer incidence, death due to cancer, and total mortality using a random-effect model. Cumulative meta-analysis, sensitivity analysis, subgroup analysis, heterogeneity tests, and tests for publication bias were also conducted.
  
  
  RESULTS
  Eighteen RCTs reporting the data on 74,498 individuals were included in the meta-analysis. Sixteen of these trials included 4103 cases of cancer; in 6 trials, 731 cancer-related deaths occurred; and in 15 trials, 7046 deaths occurred. Vitamin B supplementation had little or no effect on the incidence of cancer (RR: 1.04; 95% confidence interval [CI]: 0.98-1.10; P = 0.216), death due to cancer (RR, 1.05; 95% CI: 0.90-1.22; P = 0.521), and total mortality (RR, 1.00; 95% CI: 0.94-1.06; P = 0.952). Upon performing a cumulative meta-analysis for cancer incidence, death due to cancer, and total mortality, the nonsignificance of the effect of vitamin B persisted. With respect to specific types of cancer, vitamin B supplementation significantly reduced the risk of skin melanoma (RR, 0.47; 95% CI: 0.23-0.94; P = 0.032).
  
  
  CONCLUSIONS
  Vitamin B supplementation does not have an effect on cancer incidence, death due to cancer, or total mortality. It is associated with a lower risk of skin melanoma, but has no effect on other cancers.
authors: Department of Invasive Technology, Shanghai Seventh People's Hospital Department of Traditional Chinese and Western Medicine, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University Department of Medical Laboratory, Shanghai Seventh People's Hospital Department of Traditional Chinese Medicine, Changhai Hospital, Second Military Medical University Department of Rehabilitation Institute, Shanghai Seventh People's Hospital, Shanghai, China.
authors: Sui-Liang
authors: SL
authors: Zhang
authors: Ting-Song
authors: TS
authors: Chen
authors: Chen-Yun
authors: CY
authors: Ma
authors: Yong-Bin
authors: YB
authors: Meng
authors: Yu-Fei
authors: YF
authors: Zhang
authors: Yi-Wei
authors: YW
authors: Chen
authors: Yu-Hao
authors: YH
authors: Zhou
mesh_terms: D002423:Cause of Death; D019587:Dietary Supplements; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009369:Neoplasms / Q000188:drug therapy* / Q000453:epidemiology* / Q000473:pathology; D064887:Observational Studies as Topic; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D016019:Survival Analysis; D014803:Vitamin B Complex / Q000008:administration & dosage*
chemical_list: D014803:Vitamin B Complex