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

Abstract

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.

• Authors: 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
• Journal: PloS one (PLoS One) Vol. 12 Issue 7 Pg. e0180512 ( 2017) ISSN: 1932-6203 [Electronic] United States
• PMID: 28686645 (Publication Type: Journal Article, Meta-Analysis, Review, Systematic Review)

Chemical References

• Vitamin D
• 25-hydroxyvitamin D

Topics

• Cardiovascular Diseases (diet therapy, epidemiology, pathology)
• Diabetes Mellitus, Type 2 (diet therapy, epidemiology, pathology)
• Dietary Supplements (adverse effects)
• Humans
• Neoplasms (diet therapy, epidemiology, pathology)
• Nutrition Therapy
• Randomized Controlled Trials as Topic
• Risk Factors
• Vitamin D (adverse effects, analogs & derivatives, therapeutic use)
• Weight Loss (drug effects)