title: N-3 polyunsaturated fatty acids intake and risk of colorectal cancer: meta-analysis of prospective studies.
abstract: BACKGROUND
  Growing body of laboratory evidence supports the beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) on colorectal cancer (CRC) prevention. Epidemiologic studies investigating the relationship between n-3 PUFAs intake and risk of CRC, however, have been inconsistent. We aimed to clarify the relation by conducting a meta-analysis of prospective studies.
  
  
  METHODS
  Eligible studies were identified by searching PubMed database and by carefully reviewing bibliographies of retrieved publications. Summary relative risks (RRs) with their 95 % confidence intervals (CIs) were computed with a random-effects model. Subgroup, meta-regression, and dose-response analyses were performed to explore potential sources of heterogeneity.
  
  
  RESULTS
  A total of 14 prospective studies involving 8,775 cancer cases were included in the final analysis. Overall, total n-3 or marine PUFAs intake was not associated with risk of CRC (RR 0.99 and 1.00). However, there was a trend toward reduced risk of proximal colon cancer (total n-3 PUFAs: RR 0.83, 95 % CI 0.66-1.05; marine PUFAs: RR 0.81, 95 % CI 0.59-1.10) and a significant increased risk of distal colon cancer (total n-3 PUFAs: RR 1.26, 95 % CI 1.06-1.50; marine PUFAs: RR 1.38, 95 % CI 1.11-1.71). Furthermore, marine PUFAs intake accessed longer before diagnosis was associated 21 % reduced risk of CRC (RR 0.79, 95 % CI 0.63-1.00).
  
  
  CONCLUSIONS
  Overall, this meta-analysis finds no relation between n-3 PUFAs intake and risk of CRC. The observed subsite heterogeneity within colon cancer and the possible effect modification by latency time merit further studies.
authors.affiliation: Ningbo Municipal Center for Disease Control and Prevention, 237 Yongfeng Road, Ningbo, 315010, China.
authors.forename: Guo-Chong
authors.initials: GC
authors.lastname: Chen
authors.forename: Li-Qiang
authors.initials: LQ
authors.lastname: Qin
authors.forename: Da-Bing
authors.initials: DB
authors.lastname: Lu
authors.forename: Tie-Mei
authors.initials: TM
authors.lastname: Han
authors.forename: Yan
authors.initials: Y
authors.lastname: Zheng
authors.forename: Guo-Zhang
authors.initials: GZ
authors.lastname: Xu
authors.forename: Xiao-Huai
authors.initials: XH
authors.lastname: Wang
mesh_terms: D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D004041:Dietary Fats / Q000008:administration & dosage*; D015525:Fatty Acids, Omega-3 / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D004041:Dietary Fats; D015525:Fatty Acids, Omega-3