title: Vitamin C intake and breast cancer mortality in a cohort of Swedish women.
abstract: BACKGROUND
  Vitamin C may influence cancer progression through its antioxidant properties. However, the evidence from observational epidemiologic studies on vitamin C intake and survival following breast cancer diagnosis is not consistent, and the safety of vitamin C supplements following breast cancer diagnosis has not been extensively studied.
  
  
  METHODS
  Using a food-frequency questionnaire we investigated whether vitamin C intake was associated with survival among 3405 women diagnosed with invasive breast cancer in the Swedish Mammography Cohort.
  
  
  RESULTS
  From 1987-2010, there were 1055 total deaths with 416 deaths from breast cancer. Women in the highest quartile of pre-diagnosis vitamin C intake had an adjusted HR (95% CI) of breast cancer death of 0.75 (0.57-0.99) compared with those in the lowest quartile (Ptrend=0.03). There was a borderline significant association between vitamin C intake and total mortality (HR=0.84; 95% CI=0.71-1.00; Ptrend=0.08). Among 717 breast cancer cases for whom post-diagnosis supplement use was available, there was no association between vitamin C supplement use (≈1000 mg) and breast cancer-specific mortality (HR=1.06; 95% CI=0.52-2.17).
  
  
  CONCLUSIONS
  Our findings suggest that dietary vitamin C intake before breast cancer diagnosis may be associated with breast cancer survival. In addition, post-diagnosis vitamin C supplementation at the level observed in our population was not associated with survival.
authors.affiliation: Division of Nutritional Epidemiology, The National Institute for Environmental Medicine, Karolinska Institutet, Box 210, 171 77 Stockholm, Sweden. holly.harris@ki.se
authors.forename: H R
authors.initials: HR
authors.lastname: Harris
authors.forename: L
authors.initials: L
authors.lastname: Bergkvist
authors.forename: A
authors.initials: A
authors.lastname: Wolk
mesh_terms: D000975:Antioxidants; D001205:Ascorbic Acid / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000453:epidemiology / Q000401:mortality* / Q000517:prevention & control; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D005518:Food Preferences; D006801:Humans; D008875:Middle Aged; D011795:Surveys and Questionnaires; D016019:Survival Analysis; D013548:Sweden / Q000453:epidemiology
chemical_list: D000975:Antioxidants; D001205:Ascorbic Acid