Cancer and vitamin D supplementation: a systematic review and meta-analysis

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ABSTRACT

Background

Low 25-hydroxyvitamin D status has been associated with a higher risk of cancer in epidemiologic studies.

Objective

The aim of this study was to undertake a systematic review and meta-analysis of randomized clinical trials (RCTs) investigating the effect of vitamin D supplementation alone on cancer incidence and mortality.

Design

A systematic review was undertaken. MEDLINE, Embase, CENTRAL, conference abstracts, and clinical trial registries were searched (last search March 2017) for RCTs investigating vitamin D supplementation alone. RCTs with ≥12 mo of follow-up and in participants with a mean or median age ≥60 y were eligible. During-study events were used as the main analysis, but after-study events were included in a secondary analysis. Subgroup analyses concerning different forms of vitamin D supplementation, 25-hydroxyvitamin D status at baseline, vitamin D dose, and exclusion of open-label trials were undertaken.

Results

Thirty studies in 18,808 participants were included in the systematic review, with a median follow-up ranging from 1 to 6.2 y. The results of the meta-analysis for during-study events showed no evidence of an effect of vitamin D supplementation for cancer incidence (RR: 1.03; 95% CI: 0.91, 1.15) and cancer-related deaths (RR: 0.88; 95% CI: 0.70, 1.09). Including after-study events, the RRs were 1.02 (95% CI: 0.92, 1.13) and 0.86 (95% CI: 0.72, 1.03) respectively. These results did not appear to be affected by baseline 25-hydroxyvitamin D status, vitamin D dose, or the exclusion of open-label trials.

Conclusion

We did not find evidence to suggest that vitamin D supplementation alone reduces the incidence of cancer or cancer mortality, even after including long-term follow-up results.

Key Words

vitamin D
cancer
mortality
systematic review
meta-analysis

Cited by (0)

No funding was provided for this systematic review. The Health Services Research Unit is funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. No funding source had any role in design, data collection, interpretation, or reporting of the trial or these analyses.