Review of meta-analyses of non-skeletal benefits of vitamin D (Mortality, RTI, etc)

Created November 2017

Non-skeletal health effects of vitamin D supplementation: A systematic review on findings from meta-analyses summarizing trial data

PLOS x, July 7, 2017https://doi.org/10.1371/journal.pone.0180512

Lars Rejnmark , Lise Sofie Bislev, Kevin D. Cashman , Gudny Eiríksdottir, Martin Gaksch, Martin Grübler, Guri Grimnes, Vilmundur Gudnason, Paul Lips, Stefan Pilz, Natasja M. van Schoor, Mairead Kiely, Rolf Jorde

* * Meta-analysis of Vitamin D category listing has items along with related searches** 1. # The Meta-analysis of Mortality and Vitamin D {category} 1. # The Meta-analysis of Hypertension and Vitamin D {category}

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Background

A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D (25OHD) levels on non-skeletal outcomes. We performed a systematic quantitative review on characteristics of randomized clinical trials (RCTs) included in meta-analyses (MAs) on non-skeletal effects of vitamin D supplementation.

Methods and findings

We identified systematic reviews (SR) reporting summary data in terms of MAs of RCTs on selected non-skeletal outcomes. For each outcome, we summarized the results from available SRs and scrutinized included RCTs for a number of predefined characteristics. We identified 54 SRs including data from 210 RCTs. Most MAs as well as the individual RCTs reported null-findings on risk of cardiovascular diseases, type 2 diabetes, weight-loss, and malignant diseases.

Beneficial effects of vitamin D supplementation was reported in

  • 1 of 4 MAs on depression,

  • 2 of 9 MAs on blood pressure,

  • 3 of 7 MAs on respiratory tract infections, and

  • 8 of 12 MAs on mortality.

    Most RCTs have primarily been performed to determine skeletal outcomes, whereas non-skeletal effects have been assessed as secondary outcomes .

Only one-third of the RCTs had low level of 25OHD as a criterion for inclusion and a mean baseline 25OHD level below 50 nmol/L was only present in less than half of the analyses .

Conclusions

Published RCTs have mostly been performed in populations without low 25OHD levels. The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels.

Tags: Meta-analysis Mortality