There has been more focus on the properties of vitamin D of late. Not to do with mushrooms, but to do with the coronavirus.
Studies from several prominent universities seem to point to evidence that vitamin D is protective against coronavirus and that people with chronically low levels may be at greater risk.
Vitamin D modulates the response of white blood cells, preventing them from releasing too many inflammatory cells which may stop the body overreacting to the virus.
A study by Trinity College Dublin and The University of Liverpool also apparently shows that vitamin D appears to help reduce serious complications in coronavirus patients. Whether the evidence stacks up fully behind these studies - Stalker would contend that making sure you get your vitamin D is probably a good idea anyway.