Abstracts of the Joint International Symposia “Vitamin D in Prevention and Therapy” and “Biologic Effects of Light”

Background/Aim: There is accumulating evidence that vitamin D may beneficially affect several extra-skeletal diseases, including respiratory tract infections.The present work aimed to update the findings of an umbrella review published in 2019.Materials and Methods: We identified published systematic reviews (SRs) and meta-analyses (MAs) of cohort studies and randomized controlled trials (RCTs) on the impact of vitamin D on acute respiratory tract infections (ARI).Also, the available evidence on vitamin D status or supplementation of vitamin D and the risk of SARS-CoV-2 infections and the severity of COVID-19 was summarized.New SRs and MAs published between 2019 and 2023 were searched in PubMed and Cochrane reviews library.Results: Observational data on primary prevention suggest an inverse association between vitamin D status and the risk of ARI in adults.SRs of RCTs support the observational findings in the case of ARI in adults but did not clearly show an effect on the course of the infection.In children, studies do not clearly support a beneficial effect of vitamin D supplementation on ARI susceptibility.Concerning the susceptibility of SARS-CoV-2 infection, there is hardly any influence of the vitamin D status.However, a better vitamin D status or supplementation with vitamin D seems to be inversely associated with the severity of COVID-19.These effects were largely restricted to patients with deficient or insufficient vitamin D status.Conclusion: At least in adults, beneficial effects of a sufficient vitamin D status on the risk and severity of ARI and COVID-19 underpin the public health relevance of combatting insufficient vitamin D status.Best effects were seen with regular low-dose oral vitamin D supplements.