Clinical Health Updates

Cancer risk reduced with vitamin D/calcium supplementation

Clinical Question:
Does supplementation with calcium and vitamin D reduce cancer incidence in postmenopausal women?

Bottom Line:
Women receiving calcium and vitamin D, but not calcium alone, were less likely to develop a non-skin cancer over 4 years of supplementation. This is good news, though the study is too small to be definitive — despite enrolling more than 1000 women — since no single cancer incidence was reduced. The dose of vitamin D (1000 IU) was higher than what is typically used in research but can be found in several calcium/vitamin D products.

Reference:
Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr 2007;85:1586-1591.

Study Design:
Randomized controlled trial (double-blinded)

Synopsis:
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. The authors determined the efficacy of calcium alone and calcium plus vitamin D in reducing incident cancer risk of all types. 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. 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.