title: Association between vitamin D and risk of colorectal cancer: a systematic review of prospective studies.
abstract: OBJECTIVE
  To conduct a systematic review of prospective studies assessing the association of vitamin D intake or blood levels of 25-hydroxyvitamin D [25(OH)D] with the risk of colorectal cancer using meta-analysis.
  
  
  METHODS
  Relevant studies were identified by a search of MEDLINE and EMBASE databases before October 2010 with no restrictions. We included prospective studies that reported relative risk (RR) estimates with 95% CIs for the association between vitamin D intake or blood 25(OH)D levels and the risk of colorectal, colon, or rectal cancer. Approximately 1,000,000 participants from several countries were included in this analysis.
  
  
  RESULTS
  Nine studies on vitamin D intake and nine studies on blood 25(OH)D levels were included in the meta-analysis. The pooled RRs of colorectal cancer for the highest versus lowest categories of vitamin D intake and blood 25(OH)D levels were 0.88 (95% CI, 0.80 to 0.96) and 0.67 (95% CI, 0.54 to 0.80), respectively. There was no heterogeneity among studies of vitamin D intake (P = .19) or among studies of blood 25(OH)D levels (P = .96). A 10 ng/mL increment in blood 25(OH)D level conferred an RR of 0.74 (95% CI, 0.63 to 0.89).
  
  
  CONCLUSIONS
  Vitamin D intake and blood 25(OH)D levels were inversely associated with the risk of colorectal cancer in this meta-analysis.
authors.affiliation: The Sixth People's Hospital affiliated with Shanghai Jiao Tong University, 600 Yishan Rd, Shanghai 200233, People's Republic of China.
authors.forename: Yanlei
authors.initials: Y
authors.lastname: Ma
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Jianjun
authors.initials: J
authors.lastname: Yang
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Liu
authors.forename: Huanlong
authors.initials: H
authors.lastname: Qin
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000097:blood* / Q000453:epidemiology* / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D