“Vitamin D and Calcium Supplementation Reduces Cancer Risk: Results of a Randomized Trial”, 2007-06-01 (; backlinks):
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.
Design: 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 1,179 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°N. Subjects were randomly assigned to receive 1,400–1,500 mg supplemental calcium/d alone (Ca-only), supplemental calcium plus 1,100 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 statistically-significantly for the Ca-only group. In multiple logistic regression models, both treatment and serum 25-hydroxyvitamin D concentrations were statistically-significant, independent predictors of cancer risk.
Conclusion: Improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women. This trial was registered at ClinicalTrials.gov as NCT00352170.
[Keywords: serum 25-hydroxyvitamin D, cancer, women, calcium and vitamin D3 supplementation]