There are huge segments of the country that are always low Vit D. They cite Vit D correlations with everything. Its low hanging fruit - easy correlation to make because a large segment of the population is always low.
To graduate students with nothing to publish: Correlate vit D definciency with something. Anything. You will get a positive result. Publish a study correlating vit D deficiency with aquarium ownership. Correlate vit D deficiency with owning a chevelle. Note: A positive result is not always a meaningful result.
Vitamin D & Heart Problems: https://www.sciencedaily.com/releases/2015/11/151109160556.htm
Vitamin D & amputations: journals.sagepub.com/doi/abs/10.1177/1534734619876779
Vit D & Breast cancer: https://www.breastcancer.org/risk/factors/low_vit_d
Vit D & psychiatric illness: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6455075/
You can google anything and there will be a study showing correlation with Vitamin D. I hate it when researchers show vit D correlations. Its my pet peeve. Sorry, Terry.
Yes, I take Vitamin D, along with everyone else in my region of the country. It snows here for a large portion of the year. It snowed 2 days ago. We were all inside, hence the deficinency.
But, we do not all have the same skin color. Nor do we have higher incidence or severity of Covid. If we did, it would be due to the fact that we are all confined inside poorly ventilated buildings with other people to keep warm, not vit d deficiency.
I beg you to find one condition for which a study has not been published, relating it to vitamin D deficiency.
Sorry, again, for the rant.