After a year of treatment, vitamin D levels went up slightly in the placebo group, and went up slightly more in the normal-dose vitamin D group -- to 16 ng/mL
for girls and to 20 ng/mL
for boys. That's well below the 30 ng/mL level the U.S. National Institutes of Health states may be desirable for overall health and disease prevention.
But kids who got 2,000 IU/day vitamin D3 saw their vitamin D levels soar -- to 38 ng/mL for girls and to 35 ng/mL for boys.