Vitamin D supplementation and breast cancer prevention: a systematic review and meta-analysis of randomized clinical trials

PLoS One. 2013 Jul 22;8(7):e69269. doi: 10.1371/journal.pone.0069269. Print 2013.

Abstract

In recent years, the scientific evidence linking vitamin D status or supplementation to breast cancer has grown notably. To investigate the role of vitamin D supplementation on breast cancer incidence, we conducted a systematic review and meta-analysis of randomized controlled trials comparing vitamin D with placebo or no treatment. We used OVID to search MEDLINE (R), EMBASE and CENTRAL until April 2012. We screened the reference lists of included studies and used the "Related Article" feature in PubMed to identify additional articles. No language restrictions were applied. Two reviewers independently extracted data on methodological quality, participants, intervention, comparison and outcomes. Risk Ratios and 95% Confident Intervals for breast cancer were pooled using a random-effects model. Heterogeneity was assessed using the I(2) test. In sensitivity analysis, we assessed the impact of vitamin D dosage and mode of administration on treatment effects. Only two randomized controlled trials fulfilled the pre-set inclusion criteria. The pooled analysis included 5372 postmenopausal women. Overall, Risk Ratios and 95% Confident Intervals were 1.11 and 0.74-1.68. We found no evidence of heterogeneity. Neither vitamin D dosage nor mode of administration significantly affected breast cancer risk. However, treatment efficacy was somewhat greater when vitamin D was administered at the highest dosage and in combination with calcium (Risk Ratio 0.58, 95% Confident Interval 0.23-1.47 and Risk Ratio 0.93, 95% Confident Interval 0.54-1.60, respectively). In conclusions, vitamin D use seems not to be associated with a reduced risk of breast cancer development in postmenopausal women. However, the available evidence is still limited and inadequate to draw firm conclusions. Study protocol code: FARM8L2B5L.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Breast Neoplasms / epidemiology
  • Breast Neoplasms / mortality
  • Breast Neoplasms / prevention & control*
  • Dietary Supplements*
  • Humans
  • Incidence
  • Randomized Controlled Trials as Topic*
  • Vitamin D / pharmacology*

Substances

  • Vitamin D

Grant support

This project was supported by grant code FARM8L2B5L from the Italian Medicines Agency (AIFA). The content is solely the responsibility of the authors and does not necessarily represent the official views of the financing institution. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.