"Our research reveals that vitamin D, at doses equivalent to 2,000 IU a day, is not only safe for adolescents, but it is actually necessary for achieving desirable vitamin D levels," study leader Ghada El-Hajj Fuleihan, MD, of the American University of Beirut Medical Center in Lebanon, says in a news release.
Kids are advised to get a daily vitamin D dose of 200 IU. That suggestion came from an Institute of Medicine panel that based its recommendation on the amount of vitamin D needed to prevent rickets in infants.
However, more and more vitamin D experts have begun to suggest that children and adults need much more vitamin D than previously recognized.
New evidence strongly supports this opinion. El-Hajj Fuleihan and colleagues enrolled 340 schoolchildren in a one-year study. These 10- to 17-year-old kids attended schools in Beirut, Lebanon.
A third of the kids received an inactive, sham treatment. Another third got the recommended 200 IU/day dose of vitamin D3 (as a weekly dose of 1,400 IU). And, after an earlier safety study showed it would not be toxic, the remaining third of the kids got 2,000 IU/day of vitamin D3 (as a weekly dose of 14,000 IU) -- 10 times the recommended dose for adequate daily intake.
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. None of the kids showed signs of vitamin D toxicity.
"Supplementation of children and adolescents with 2,000 IU a day of vitamin D3 is well tolerated and safe," El-Hajj Fuleihan says. "This is particularly relevant in light of the increasingly recognized health benefits of vitamin D for adults and children."
The researchers strongly suggest that many children are getting far too little vitamin D, especially those who do not get plenty of sun exposure throughout the year. The skin makes vitamin D when exposed to direct sunlight.
El-Hajj Fuleihan and colleagues note that every 100 IU of oral vitamin D3 raises levels by about 1 ng/mL. Thus, children with levels below 20 ng/mL -- the average for untreated children in this study -- would benefit from daily supplementation with 2,000 IU of vitamin D3.
"The high prevalence of [too-low vitamin D levels] worldwide across all age groups, the fact that many diseases of adulthood are rooted in the pediatric age group, and the safety data available to date render it quite compelling to modify the current recommendations regarding adequate vitamin D intake not only for adults but also for children," the researchers conclude.
This study was supported by grants from Nestle, which makes vitamin-D-fortified milk products, and from Merck, which makes a vitamin D supplement popular in Europe.
El-Hajj Fuleihan and colleagues report their findings in the advance online edition of the July issue of the Journal of Clinical Endocrinology & Metabolism.