Pleiotropic effects of vitamin D including aspects of COVID-19

ABSTRACT

Vitamin D is provided by nutritional sources or by skin synthesis under the influence of UV light. In the liver, vitamin D is converted to 25(OH)-vitamin D and finally in the kidney to 1,25(OH)2-vitamin D, which is a hormone regulating bone andmineralmetabolism. Besides the kidneys, other organs are also capable of making 1,25(OH)2-vitamin D, which exerts autocrine and paracrine effects. For these pleiotropic effects, a continuous vitamin D supply (daily supplements) with moderate doses is more effective than high-dose bolus applications. Beside the classical effects of 1,25(OH)2-vitamin D on the musculoskeletal system, there is good evidence for extraskeletal effects on the immune system. A good vitamin D supply can reduce the risk of respiratory infections. At the present time, the preventive and therapeutic use of vitamin D regarding COVID-19 (coronavirus disease 19) is of great interest.