title: Vitamin supplement use and risk for breast cancer: the Shanghai Breast Cancer Study.
abstract: OBJECTIVE
  The influence of vitamin supplements on breast cancer risk is unclear and the interactive effects of dietary and supplemental sources are unknown. This study investigated (1) the association between self-reported vitamin supplement use (multivitamin, A, B, C, and E) and breast cancer and (2) the combined effect of vitamin supplements in relation to dietary vitamin intakes on breast cancer risk.
  
  
  METHODS
  The Shanghai Breast Cancer Study was a population-based case-control study conducted in Shanghai in 1996-1998 (Phase I) and 2002-2004 (Phase II). Participants were aged 25-64 (Phase I) and 20-70 years (Phase II). The analyses included 3,454 incident breast cancer cases and 3,474 controls. Unconditional logistic regression models were used to determine adjusted odds ratios (ORs) for breast cancer risk associated with vitamin supplement use.
  
  
  RESULTS
  Overall, breast cancer risk was not related to any vitamin supplement intake. However, a 20% reduction in breast cancer risk was observed with vitamin E supplement use among women with low-dietary vitamin E intake (OR = 0.8; 95% confidence interval (CI), 0.6-1.0). A non-significant 20% risk reduction was observed among vitamin B supplement users with low B dietary intake (OR = 0.8; 95% CI, 0.6-1.1). Frequent use of a vitamin B supplement was adversely associated with breast cancer risk among those with high dietary vitamin B intake (OR = 1.4; 95% CI: 0.9-2.1; P for interaction = 0.07).
  
  
  CONCLUSIONS
  This study suggests that vitamins E and B supplements may confer protection against breast cancer among women who have low dietary intake of those vitamins.
authors.affiliation: Department of Medicine, Vanderbilt Epidemiology Center, School of Medicine, Vanderbilt University, Nashville, TN, USA.
authors.forename: Tsogzolmaa
authors.initials: T
authors.lastname: Dorjgochoo
authors.forename: Martha J
authors.initials: MJ
authors.lastname: Shrubsole
authors.forename: Xiao Ou
authors.initials: XO
authors.lastname: Shu
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Zhixian
authors.initials: Z
authors.lastname: Ruan
authors.forename: Ying
authors.initials: Y
authors.lastname: Zheng
authors.forename: Hui
authors.initials: H
authors.lastname: Cai
authors.forename: Qi
authors.initials: Q
authors.lastname: Dai
authors.forename: Kai
authors.initials: K
authors.lastname: Gu
authors.forename: Yu-Tang
authors.initials: YT
authors.lastname: Gao
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
mesh_terms: D000328:Adult; D000368:Aged; D001205:Ascorbic Acid / Q000008:administration & dosage; D001943:Breast Neoplasms / Q000209:etiology / Q000517:prevention & control*; D016022:Case-Control Studies; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008875:Middle Aged; D012306:Risk; D014801:Vitamin A / Q000008:administration & dosage; D014803:Vitamin B Complex / Q000008:administration & dosage; D014810:Vitamin E / Q000008:administration & dosage; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D014815:Vitamins; D014801:Vitamin A; D014803:Vitamin B Complex; D014810:Vitamin E; D001205:Ascorbic Acid