They measure obesity and find it 0.02 vs 0.01 for vitamin d, which seems a decent enough proxy for lifestyle for this kind of study so your underlying point is

They measure obesity and find it 0.02 vs 0.01 for vitamin d, which seems a decent enough proxy for lifestyle for this kind of study so your underlying point is valid here. Actually i think the biggest missing control is race. I went in skeptical even though intuitively being deficient in vitamin d makes sense, this isn’t convincing but I agree with with their conclusion that it’s worth a bigger study. If someone reading is wondering whether to maintain a healthy level of vitamin D to help if you get covid, yes you should. Should have done that before this study ofc.