title: Retinol, vitamins A, C, and E and breast cancer risk: a meta-analysis and meta-regression.
abstract: OBJECTIVE
  To comprehensively summarize the associations between retinol, vitamins A, C, and E and breast cancer, and quantitatively estimate their dose-response relationships.
  
  
  METHODS
  We searched PubMed, Embase, and Cochrane databases (from January 1982 to 15 March 2011) and the references of the relevant articles in English with sufficient information to estimate relative risk or odds ratio and the 95% confidence intervals, and comparable categories of vitamins. Two reviewers independently extracted data using a standardized form, with any discrepancy adjudicated by the third reviewer.
  
  
  RESULTS
  Overall, 51 studies met the inclusion criteria. Comparing the highest with the lowest intake, total vitamin A intake reduced the breast cancer risk by 17% (pooled OR = 0.83, 95% CI: 0.78-0.88). Further subgroup analysis based on study design did not change the significant reduction. Although the dietary vitamin A, dietary vitamin E, and total vitamin E intake all reduced breast cancer risk significantly when data from all studies were pooled, the results became nonsignificant when data from cohort studies were pooled. The significant association between total retinol intake and breast cancer in all studies became nonsignificant in case-control studies but remain significant in cohort studies. No significant dose-response relationship was observed in the higher intake of these vitamins with reduced breast cancer risk.
  
  
  CONCLUSIONS
  Our results indicate that both the total intake of vitamin A and retinol could reduce breast cancer risk. However, associations between other vitamins and breast cancer seem to be limited.
authors.affiliation: Department of Epidemiology, Public Health College, Harbin Medical University, 157, Baojian Street, Nangang District, Harbin, Heilongjiang, People's Republic of China.
authors.forename: Hu
authors.initials: H
authors.lastname: Fulan
authors.forename: Jiang
authors.initials: J
authors.lastname: Changxing
authors.forename: Wang Yi
authors.initials: WY
authors.lastname: Baina
authors.forename: Zhang
authors.initials: Z
authors.lastname: Wencui
authors.forename: Lin
authors.initials: L
authors.lastname: Chunqing
authors.forename: Wang
authors.initials: W
authors.lastname: Fan
authors.forename: Li
authors.initials: L
authors.lastname: Dandan
authors.forename: Sun
authors.initials: S
authors.lastname: Dianjun
authors.forename: Wang
authors.initials: W
authors.lastname: Tong
authors.forename: Pang
authors.initials: P
authors.lastname: Da
authors.forename: Zhao
authors.initials: Z
authors.lastname: Yashuang
mesh_terms: D001205:Ascorbic Acid / Q000008:administration & dosage; D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D016017:Odds Ratio; D012044:Regression Analysis; D012307:Risk Factors; D014801:Vitamin A / Q000008:administration & dosage; D014810:Vitamin E / Q000008:administration & dosage; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D014815:Vitamins; D014801:Vitamin A; D014810:Vitamin E; D001205:Ascorbic Acid