title: Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial.
abstract: BACKGROUND
  Numerous observational studies have found supplemental calcium and vitamin D to be associated with reduced risk of common cancers. However, interventional studies to test this effect are lacking.
  
  
  OBJECTIVE
  The purpose of this analysis was to determine the efficacy of calcium alone and calcium plus vitamin D in reducing incident cancer risk of all types.
  
  
  METHODS
  This was a 4-y, population-based, double-blind, randomized placebo-controlled trial. The primary outcome was fracture incidence, and the principal secondary outcome was cancer incidence. The subjects were 1179 community-dwelling women randomly selected from the population of healthy postmenopausal women aged >55 y in a 9-county rural area of Nebraska centered at latitude 41.4 degrees N. Subjects were randomly assigned to receive 1400-1500 mg supplemental calcium/d alone (Ca-only), supplemental calcium plus 1100 IU vitamin D3/d (Ca + D), or placebo.
  
  
  RESULTS
  When analyzed by intention to treat, cancer incidence was lower in the Ca + D women than in the placebo control subjects (P < 0.03). With the use of logistic regression, the unadjusted relative risks (RR) of incident cancer in the Ca + D and Ca-only groups were 0.402 (P = 0.01) and 0.532 (P = 0.06), respectively. When analysis was confined to cancers diagnosed after the first 12 mo, RR for the Ca + D group fell to 0.232 (CI: 0.09, 0.60; P < 0.005) but did not change significantly for the Ca-only group. In multiple logistic regression models, both treatment and serum 25-hydroxyvitamin D concentrations were significant, independent predictors of cancer risk.
  
  
  CONCLUSIONS
  Improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00352170.
authors.affiliation: Osteoporosis Research Center, Creighton University, Omaha, NE 68131, USA. jmlappe@creighton.edu
authors.forename: Joan M
authors.initials: JM
authors.lastname: Lappe
authors.forename: Dianne
authors.initials: D
authors.lastname: Travers-Gustafson
authors.forename: K Michael
authors.initials: KM
authors.lastname: Davies
authors.forename: Robert R
authors.initials: RR
authors.lastname: Recker
authors.forename: Robert P
authors.initials: RP
authors.lastname: Heaney
mesh_terms: D002112:Calcifediol / Q000097:blood; D002118:Calcium / Q000627:therapeutic use*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D050723:Fractures, Bone / Q000517:prevention & control; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D016015:Logistic Models; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D014807:Vitamin D / Q000627:therapeutic use*
chemical_list: D014807:Vitamin D; D002112:Calcifediol; D002118:Calcium