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Association between vitamin D supplementation and mortality: systematic review and meta-analysis

Author/s: 
Zhang, Y., Fang, F., Tang, J., Jia, L., Feng, Y., Xu, P., Faramand, A.

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.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Keywords 
cancer cancer mortality vitamin D Vitamin D3 supplimentation

Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis.

Author/s: 
Martineau, Adrian R., Jolliffe, David A., Greenberg, Lauren, Aloia, John F., Bergman, Peter, Dubnov-Rax, Gal, Esposito, Susanna, Ganmaa, Davaasambuu, Ginde, Adit A., Goodall, Emma C., Grant, Cameron C., Janssens, Wim, Jensen, Megan E., Kerley, Conor P., Laaksi, Ilkka, Manaseki-Holland, Semira, Mauger, David, Murdoch, David R., Neale, Rachel, Rees, Judy R., Simpson, Steve Jr., Stelmach, Iwona, Kumar, Geeta Trilok, Mitsuyoshi, Urashima, Camargo, Carlos A. Jr., Griffiths, Christopher J., Hooper, Richard L.

BACKGROUND:

Randomised controlled trials (RCTs) exploring the potential of vitamin D to prevent acuterespiratory infections have yielded mixed results. Individual participant data (IPD) meta-analysis has the potential to identify factors that may explain this heterogeneity.

OBJECTIVES:

To assess the overall effect of vitamin D supplementation on the risk of acute respiratory infections (ARIs) and to identify factors modifying this effect.

DATA SOURCES:

MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, ClinicalTrials.gov and the International Standard Randomised Controlled Trials Number (ISRCTN) registry.

STUDY SELECTION:

Randomised, double-blind, placebo-controlled trials of supplementation with vitamin D3 or vitamin D2 of any duration having incidence of acute respiratory infection as a prespecified efficacy outcome were selected.

STUDY APPRAISAL:

Study quality was assessed using the Cochrane Collaboration Risk of Bias tool to assess sequence generation, allocation concealment, blinding of participants, personnel and outcome assessors, completeness of outcome data, evidence of selective outcome reporting and other potential threats to validity.

RESULTS:

We identified 25 eligible RCTs (a total of 11,321 participants, aged from 0 to 95 years). IPD were obtained for 10,933 out of 11,321 (96.6%) participants. Vitamin D supplementation reduced the risk of ARI among all participants [adjusted odds ratio (aOR) 0.88, 95% confidence interval (CI) 0.81 to 0.96; heterogeneity p < 0.001]. Subgroup analysis revealed that protective effects were seen in individuals receiving daily or weekly vitamin D without additional bolus doses (aOR 0.81, 95% CI 0.72 to 0.91), but not in those receiving one or more bolus doses (aOR 0.97, 95% CI 0.86 to 1.10; p = 0.05). Among those receiving daily or weekly vitamin D, protective effects of vitamin D were stronger in individuals with a baseline 25-hydroxyvitamin D [25(OH)D] concentration of < 25 nmol/l (aOR 0.30, 95% CI 0.17 to 0.53) than in those with a baseline 25(OH)D concentration of ≥ 25 nmol/l (aOR 0.75, 95% CI 0.60 to 0.95; p = 0.006). Vitamin D did not influence the proportion of participants experiencing at least one serious adverse event (aOR 0.98, 95% CI 0.80 to 1.20; p = 0.83). The body of evidence contributing to these analyses was assessed as being of high quality.

LIMITATIONS:

Our study had limited power to detect the effects of vitamin D supplementation on the risk of upper versus lower respiratory infection, analysed separately.

CONCLUSIONS:

Vitamin D supplementation was safe, and it protected against ARIs overall. Very deficient individuals and those not receiving bolus doses experienced the benefit. Incorporation of additional IPD from ongoing trials in the field has the potential to increase statistical power for analyses of secondary outcomes.

Keywords 
vitamin D dietary supplements respiratory infections
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