"Abstract
To assess the evidence on SARS-CoV2 infection and Covid-19 in relation to deficiency and supplementation of vitamin D, we conducted a systematic review up to April 2021. We summarised data from 38 eligible studies, which presented risk estimates for at least one endpoint, including two RCT and 27 cohort-studies: 205565 patients with information on 25OHD status and 2022 taking vitamin D supplementation with a total of 1197 admitted to the ICU or who needed invasive mechanical ventilation or intubation and hospital stay, and more than 910 Covid-19 deaths...
Statistical analysis
Depending on the studies, we used odds ratios (ORs), hazard ratios (HRs) and relative risk (RRs) as comparable estimates of the RR. Random effect models were used to calculate summary relative risk (SRRs) and 95% CIs to evaluate the association between lowest versus highest level of serum VD [vitamin D], or vitamin D supplementation versus no supplementation, and SARS-CoV2 infection or Covid-9 severity or Covid-19 mortality. In total, five meta-analyses were performed, according to combinations of the different outcomes and exposure of interest...
Association between baseline serum vitamin D levels and mortality in patients with Covid-19
When the meta-analysis was restricted to cohort studies only (N = 15), results suggested an even higher risk of death for subjects with low 25(OH)D levels (SRR = 2.79, 95% CI: 1.63–4.79). Considering only prospective studies (N = 10) led to similar results (SRR = 2.71, 95% CI: 1.34–5.46) with a stronger association compared to the one obtained considering only the retrospective studies (N = 9, SRR = 2.05, 95% CI: 1.05–4.01)...
Discussion
... From our meta-analysis, Covid-19 patients who supplemented their diet with VD had a 73% reduced risk of mortality, taking into account age, sex, comorbidities and other adjustments. Our findings corroborate the results of a recent meta-analysis of pooled data from RCTs showing that VD supplementation may reduce the risk of acute respiratory infections (ARI). Interestingly, in the studies in which VD was administered daily, a significant protective effect of VD supplementation was observed on the risk of having one or more ARI (OR = 0.78, 95% CI: 0.65–0.94)...
Conclusions
... [O]ur meta-analysis of both observational and interventional studies suggests that people with Covid-19 taking Vitamin D supplementation, may have a reduced risk of both severity and mortality compared to subjects who do not take Vitamin D supplementation, although further RCT are necessary to draw a definitive conclusion on the causal link."
Funding: Grant Regione Lombardia. (DECRETO N. 7082 Del 17/06/2020. Identificativo Atto n. 366: COVitaminD Trial: prevenzione di complicanze da COVID-19 in pazienti oncologici). The European Institute of Oncology, Milan, Italy is partially supported by the Italian Ministry of Health with Ricerca Corrente and 5×1,000 funds.Federica Bellerba is a Ph.D. student within the European School of Molecular Medicine (SEMM). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Copyright: © 2022 D’Ecclesiis et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.