There was a recent thread suggesting that it was radiation, rather than vitamin D, that led to better Covid outcomes. Not sure I’m convinced, but food for thought.
Isn't natural vitamin D from the sun via ultra-violet radiation? That's the best kind.
FWIW - vitamin D deficiency and a negative outcome with Covid is well studied and well established. While our bodies produce vitamin D in sunlight you can easily replace it by taking cheap vitamin D in supplements.
I would be interested in reading the thread you referenced if you can find it. FRegards