title: Intakes of heme iron and zinc and colorectal cancer incidence: a meta-analysis of prospective studies.
abstract: BACKGROUND
  Epidemiologic findings concerning the associations between intakes of heme iron and zinc and colorectal cancer (CRC) incidence yielded conflicting results. We aimed to investigate the associations by performing a meta-analysis of prospective studies.
  
  
  METHODS
  We conducted a literature search on PubMed and EMBASE databases up to December 2012 to identify the prospective studies that investigated the relationships between heme iron or zinc intake and risk of CRC. We also reviewed the bibliographies of the retrieved articles to identify additional studies. We used a random-effects model to calculate the summary relative risks (RRs) with 95 % confidence intervals (CIs).
  
  
  RESULTS
  Eight studies on heme iron intake and six studies on zinc intake met the inclusion criteria. The summary RR of CRC for the highest versus the lowest intake was 1.14 (95 % CI = 1.04-1.24) for heme iron and 0.83 (95 % CI = 0.72-0.94) for zinc, respectively. The observed associations were not significantly modified by subsites within the colorectum, sex, geographic area, study duration, the number of cases, or the range of intakes. In the dose-response analyses, the summary RR of CRC was 1.11 (95 % CI = 1.03-1.18) for heme iron intake of 1 mg/day, and 0.86 (95 % CI = 0.78-0.96) for zinc intake of 5 mg/day, respectively. There was little evidence of publication bias.
  
  
  CONCLUSIONS
  This meta-analysis suggests a significant positive dose-response association of heme iron intake and a significant inverse dose-response association of zinc intake with risk of CRC.
authors.affiliation: Department of Colorectal Surgery and Oncology, Shengjing Hospital of China Medical University, Shenyang, 110004, Liaoning, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Qiao
authors.forename: Yong
authors.initials: Y
authors.lastname: Feng
mesh_terms: D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000097:blood / Q000453:epidemiology*; D005260:Female; D006418:Heme / Q000378:metabolism*; D006801:Humans; D015994:Incidence; D019266:Iron, Dietary / Q000008:administration & dosage*; D008297:Male; D008460:Meat; D011446:Prospective Studies; D012307:Risk Factors; D015032:Zinc / Q000008:administration & dosage*
chemical_list: D019266:Iron, Dietary; D006418:Heme; D015032:Zinc