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Hat Vitamin D eine schützende Funktion gegen COVID-19?

von NFI Redaktion

In a recent study published in Nutrients, researchers investigated whether vitamin D supplementation could provide benefits before the onset of Coronavirus Disease 2019 (COVID-19).

Study: Preventive Vitamin D Supplementation and Risk of COVID-19 Infection: A Systematic Review and Meta-Analysis. Image Credit: FotoHelin/Shutterstock.comStudy: Preventive Vitamin D Supplementation and Risk of COVID-19 Infection: A Systematic Review and Meta-Analysis. Image Credit: FotoHelin/Shutterstock.com

Background

Vitamin D is fat-soluble and synthesized in the epidermis; metabolic processes are required for its activation. 1,25-hydroxyvitamin D is the primary end product of these processes.

It binds to the Vitamin D receptor (VDR), which mediates much of the vitamin’s effects and promotes the expression of genes with specific sequences.

The interplay between VDR, Vitamin D, and repressor/promoter proteins has a crucial impact on bone mineral density.

Approximately 3% of the human genome is controlled by 1,25-dihydroxyvitamin D; hence, it is believed that Vitamin D regulates muscle function, metabolism, immune response, and oncogenesis, among other functions. The effects of Vitamin D on diseases, including COVID-19, are under investigation.

Available data suggest that adequate serum levels of Vitamin D may protect against the incidence and mortality of COVID-19; however, this has not been validated.

About the Study

The present study examined whether prophylactic Vitamin D supplementation before COVID-19 could lead to positive outcomes.

The researchers searched databases such as MEDLINE/PubMed, Scopus, Google Scholar, and Cochrane for randomized controlled trials (RCTs) as well as quasi-experimental, case-control, cross-sectional, and cohort studies with relevant quantitative data on Vitamin D supplementation before COVID-19 diagnosis and its role in combating the disease.

The study population included patients or healthcare workers (HCWs). The primary endpoint was COVID-19 incidence; secondary endpoints were COVID-19-related ICU admissions and mortality.

The researchers excluded studies with insufficient data and those that did not meet the Population, Intervention, Comparison, Outcome, and Study Design (PICOS) criteria. There were no restrictions based on language or publication year.

Two authors screened the literature and studies were included after a full-text review. Data on relevant parameters were extracted. The team calculated Odds Ratios and corresponding 95% confidence intervals as effect measures.

The quality and bias of the study were assessed using specific evaluation tools tailored to the type of study. Statistical heterogeneity was evaluated using χ2 and I2 statistics. Publication bias was assessed using funnel plots and linear Egger regression.

Results

The team selected a total of 16 publications for analysis. Seven studies were RCTs and eight were analytical studies. Five RCTs included HCWs and two included patients. RCTs compared Vitamin D supplementation to no treatment or high-dose versus low-dose therapies.

COVID-19 incidence was evaluated in 13 studies, ICU admission in three, and mortality in 11 studies. The frequency of supplementation varied across the studies.

Fifteen studies reported the exact dose of Vitamin D. Control subjects received a placebo, low-dose Vitamin D, or none. In RCTs, Vitamin D supplementation was associated with a lower infection risk despite significant heterogeneity.

In RCTs involving HCWs, supplementation reduced the risk by approximately 80% with negligible heterogeneity. The prevalence of Vitamin D deficiency and insufficiency was consistent in these studies.

In RCTs in non-HCW populations, Vitamin D supplementation did not impact the COVID-19 infection rate. It is noteworthy that the treatment group received a lower dose compared to other studies.

The researchers speculate that the low dose and low prevalence of Vitamin D deficiency may have contributed to the lack of effect. Analytical studies indicated a protective role of supplementation, although heterogeneity was high.

Only one RCT investigated COVID-19 mortality and reported a significant reduction in mortality among Vitamin D recipients.

Furthermore, no association between Vitamin D supplementation and COVID-19 mortality was observed in analytical studies. Additionally, Vitamin D supplementation protected against COVID-19-related ICU admission.

Conclusions

The study examined the protective effects of Vitamin D supplementation supplemented before the onset of COVID-19 on disease incidence, ICU admission, and mortality.

RCTs and analytical studies reported a decrease in COVID-19 among Vitamin D recipients, especially in populations with a higher incidence of Vitamin D deficiency. It is noteworthy that the number of studies analyzed was lower than in previous meta-analyses.

However, unlike the current study, they focused on other aspects, namely supplementation during COVID-19. Furthermore, several studies in this analysis lacked data on the prevalence of Vitamin D deficiency, the Vitamin D formulation, i.e., Calcitriol, Cholecalciferol, etc.

Overall, the results support the use of Vitamin D for the prevention of COVID-19 and associated complications, particularly in individuals with Vitamin D deficiency.

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