Vitamin D3 supplementation appears to reduce cancer-related mortality. It is a little hard to tell whether it works regardless of initial 25OH VitD levels as this analysis suggests. James W. Mold, MD, MPH

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Abstract

OBJECTIVE:

To investigate whether vitamin D supplementation is associated with lower mortality in adults.

DESIGN:

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES:

Medline, Embase, and the Cochrane Central Register from their inception to 26 December 2018.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES:

Randomised controlled trials comparing vitamin D supplementation with a placebo or no treatment for mortality were included. Independent data extraction was conducted and study quality assessed. A meta-analysis was carried out by using fixed effects and random effects models to calculate risk ratio of death in the group receiving vitamin D supplementation and the control group.

MAIN OUTCOME MEASURES:

All cause mortality.

RESULTS:

52 trials with a total of 75 454 participants were identified. Vitamin D supplementation was not associated with all cause mortality (risk ratio 0.98, 95% confidence interval 0.95 to 1.02, I2=0%), cardiovascular mortality (0.98, 0.88 to 1.08, 0%), or non-cancer, non-cardiovascular mortality (1.05, 0.93 to 1.18, 0%). Vitamin D supplementation statistically significantly reduced the risk of cancer death (0.84, 0.74 to 0.95, 0%). In subgroup analyses, all cause mortality was significantly lower in trials with vitamin D3 supplementation than in trials with vitamin D2 supplementation (P for interaction=0.04); neither vitamin D3 nor vitamin D2 was associated with a statistically significant reduction in all cause mortality.

CONCLUSIONS:

Vitamin D supplementation alone was not associated with all cause mortality in adults compared with placebo or no treatment. Vitamin D supplementation reduced the risk of cancer death by 16%. Additional large clinical studies are needed to determine whether vitamin D3 supplementation is associated with lower all cause mortality.

STUDY REGISTRATION:

PROSPERO registration number CRD42018117823.

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Author/s:

Zhang, Y., Fang, F., Tang, J., Jia, L., Feng, Y., Xu, P., Faramand, A.