A wonderful drug, almost the only drug that can artificially provide the body with vitamin D. Most importantly: check everything with your doctor and do not get carried away. Prolonged uncontrolled use at high dosages can lead to very bad consequences (especially in children).
It helped me when after a protracted viral infection there was vitamin deficiency.
After the course (along with magnesium), the muscles ceased to constrict, hair and nails became stronger. So I think the point to drink is to eat.