title: Antioxidants and breast cancer risk- a population-based case-control study in Canada.
abstract: BACKGROUND
  The effect of antioxidants on breast cancer is still controversial. Our objective was to assess the association between antioxidants and breast cancer risk in a large population-based case-control study.
  
  
  METHODS
  The study population included 2,362 cases with pathologically confirmed incident breast cancer (866 premenopausal and 1,496 postmenopausal) and 2,462 controls in Canada. Intakes of antioxidants from diet and from supplementation as well as other potential risk factors for breast cancer were collected by a self-reported questionnaire.
  
  
  RESULTS
  Compared with subjects with no supplementation, 10 years or longer supplementation of zinc had multivariable-adjusted odds ratios (OR) and 95% confidence intervals (CI) of 0.46 (0.25-0.85) for premenopausal women, while supplementation of 10 years or longer of multiple vitamin, beta-carotene, vitamin C, vitamin E and zinc had multivariable-adjusted ORs (95% CIs) of 0.74 (0.59, 0.92), 0.58 (0.36, 0.95), 0.79 (0.63-0.99), 0.75 (0.58, 0.97), and 0.47 (0.28-0.78), respectively, for postmenopausal women. No significant effect of antioxidants from dietary sources (including beta-carotene, alpha-carotene, lycopene, lutein and zeaxanthin, vitamin C, vitamin E, selenium and zinc) or from supplementation less than 10 years was observed.
  
  
  CONCLUSIONS
  This study suggests that supplementation of zinc in premenopausal women, and supplementation of multiple vitamin, beta-carotene, vitamin C, vitamin E and zinc in postmenopausal women for 10 or more years may protect women from developing breast cancer. However, we were unable to determine the overall effect of total dose or intake from both diet and supplement.
authors.affiliation: Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada, Ottawa, Ontario, Canada. sai.yi.pan@phac-aspc.gc.ca
authors.forename: Sai Yi
authors.initials: SY
authors.lastname: Pan
authors.forename: Jia
authors.initials: J
authors.lastname: Zhou
authors.forename: Laurie
authors.initials: L
authors.lastname: Gibbons
authors.forename: Howard
authors.initials: H
authors.lastname: Morrison
authors.forename: Shi Wu
authors.initials: SW
authors.lastname: Wen
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D016017:Odds Ratio; D017698:Postmenopause; D017697:Premenopause; D012307:Risk Factors
chemical_list: D000975:Antioxidants