title: The association of vitamin D supplementation with the risk of cancer in postmenopausal women.
abstract: OBJECTIVE
  There is inconclusive evidence on whether vitamin D therapy reduces cancer risk. We investigated the effect of vitamin D (±calcium) supplementation on the risk of breast, ovarian, uterine, colorectal, and lung cancer in women.
  
  
  METHODS
  We conducted a case-control study using the UK Clinical Practice Research Datalink (CPRD); cases were women aged ≥55 years with a first diagnosis of either breast, colorectal, lung, ovarian, or uterine cancer between 2002 and 2009, with at least 5 years of CPRD follow-up prior to the date of diagnosis, and controls were women without cancer, frequency-matched to cases by year of birth, date of study entry, length of follow-up, and general practice. The association of vitamin D supplementation with the odds of developing each cancer was determined using multivariable logistic regression, controlling for body mass index, smoking, alcohol, and deprivation.
  
  
  RESULTS
  Ninety-seven percent of women took vitamin D with a calcium supplement. Exposure to three or more prescriptions of vitamin D was associated with a 17 % reduced odds (95 % CI 0.71-0.97) of breast cancer versus 1-2 prescriptions, but this effect disappeared when omitting women first exposed within a year of diagnosis (OR 1.0, 95 % CI 0.82-1.23). Having more than 10 prescriptions of vitamin D was associated with a 17 % lower odds (95 % CI 0.65-1.06) of colorectal cancer, but the estimates are imprecise. There was little evidence of associations of supplements with lung or gynecological cancers.
  
  
  CONCLUSIONS
  We found little evidence that vitamin D (largely with calcium) supplementation is associated with decreased breast, lung, ovarian, and uterine cancer risk. There is a possible protective association between having more than 10 prescriptions of vitamin D supplements and colorectal cancer, but it requires further investigation.
authors: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK, theresa.redaniel@bristol.ac.uk.
authors: Maria Theresa
authors: MT
authors: Redaniel
authors: Michael P
authors: MP
authors: Gardner
authors: Richard M
authors: RM
authors: Martin
authors: Mona
authors: M
authors: Jeffreys
mesh_terms: D002118:Calcium / Q000008:administration & dosage; D016022:Case-Control Studies; D015331:Cohort Studies; D019587:Dietary Supplements / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D017698:Postmenopause; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology; D014807:Vitamin D / Q000008:administration & dosage*
chemical_list: D014807:Vitamin D; D002118:Calcium