Vitamin D: Should you take vitamin D as a supplement?

I have drawn vitamin D levels on thousands of children when I was in practice. Almost all were in the 10 - 30 ng/ml range (normal 30 - 100). Clinically many with levels below 20 have bone or muscle pains. Ongoing supplementation with 1000 IU/d for infants and toddlers, 2000 IU for preschool ages, 3000 IU for school ages and 5000 IU for adult sized teens…