Abstract
PURPOSE OF REVIEW Old age, obesity and vitamin D deficiency are considered as independent risk factors for severe courses of COVID-19. The aim of the review is to discuss common features of these risk factors and the impact of vitamin D. RECENT FINDINGS The recently discovered relationship between vitamin D and the infection pathway of the virus via the renin--angiotensin system (RAS) and the adipokines leptin and adiponectin play an important role. The frequency of studies showing a relationship between a low vitamin D status in comorbidities and severe COVID-19 courses makes an impact of vitamin D effects likely. SUMMARY There is a direct relationship between vitamin D, body fat and age in COVID-19 courses. With age, the ability of the skin to synthesize vitamin D decreases, and leads to vitamin D-deficits. If the skin is insufficiently exposed to sunlight, severe deficits can develop. As vitamin D plays an important role not only in the immune system but also in the RAS, and thus at the point where the virus attacks, a good vitamin D supply is an important basis for reducing the risk of severe COVID-19 processes. Treatment with vitamin D supplements should be based on severity of the vitamin D deficiency.
