title: Vitamin C and survival among women with breast cancer: a meta-analysis.
abstract: BACKGROUND
  The association between dietary vitamin C intake and breast cancer survival is inconsistent and few studies have specifically examined vitamin C supplement use among women with breast cancer. The purpose of this study was to summarise results from prospective studies on the association between vitamin C supplement use and dietary vitamin C intake and breast cancer-specific mortality and total mortality.
  
  
  METHODS
  Studies were identified using the PubMed database through February 6, 2014 and by examining the references of retrieved articles. Prospective studies were included if they reported relative risks (RR) with 95% confidence intervals (95% CIs) for at least two categories or as a continuous exposure. Random-effects models were used to combine study-specific results.
  
  
  RESULTS
  The ten identified studies examined vitamin C supplement use (n=6) and dietary vitamin C intake (n=7) and included 17,696 breast cancer cases, 2791 total deaths, and 1558 breast cancer-specific deaths. The summary RR (95% CI) for post-diagnosis vitamin C supplement use was 0.81 (95% CI 0.72-0.91) for total mortality and 0.85 (95% CI 0.74-0.99) for breast cancer-specific mortality. The summary RR for a 100mg per day increase in dietary vitamin C intake was 0.73 (95% CI 0.59-0.89) for total mortality and 0.78 (95% CI 0.64-0.94) for breast cancer-specific mortality.
  
  
  CONCLUSIONS
  Results from this meta-analysis suggest that post-diagnosis vitamin C supplement use may be associated with a reduced risk of mortality. Dietary vitamin C intake was also statistically significantly associated with a reduced risk of total mortality and breast cancer-specific mortality.
authors.affiliation: Unit of Nutritional Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Box 210, 171 77 Stockholm, Sweden; Obstetrics and Gynecology Epidemiology Center, Brigham and Women's Hospital, 221 Longwood Avenue, Boston, MA 02115, USA. Electronic address: holly.harris@ki.se.
authors.forename: Holly R
authors.initials: HR
authors.lastname: Harris
authors.affiliation: Unit of Nutritional Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Box 210, 171 77 Stockholm, Sweden.
authors.forename: Nicola
authors.initials: N
authors.lastname: Orsini
authors.affiliation: Unit of Nutritional Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Box 210, 171 77 Stockholm, Sweden.
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage*; D001205:Ascorbic Acid / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000401:mortality* / Q000517:prevention & control; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D011446:Prospective Studies; D016019:Survival Analysis; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D000975:Antioxidants; D014815:Vitamins; D001205:Ascorbic Acid
keywords: Breast cancer; Meta-analysis; Mortality; Supplement use; Vitamin C