A preliminary, unpublished study speculates that vitamin D deficiency may have something to do with poor COVID-19 outcomes. Its authors suggest people may benefit from ensuring they are getting enough vitamin D.
However, there are serious concerns about the research. Vitamin D is one of the nutrients that are crucial to human health, on the whole.
The human body naturally synthesizes this vitamin — in fact, a group of substances — through adequate exposure to sunlight. Only a few foods, such as egg yolks, can be a source of vitamin D, which means that people who have little access to sunlight may experience vitamin D insufficiency or deficiency.