The American Academy of Pediatrics has recently doubled the recommended daily vitamin D intake for children from 200 to 400 IU per day—A nice step in the right direction, but terribly inadequate. Children who play outside in summer sunlight will make that much vitamin D in a few minutes, provided their parents do not slather them with sunscreen, which prevents 99% of all vitamin D production by skin.
In winter in northern latitudes, no vitamin D is produced by the skin. In that case, either food sources or supplementation are necessary to produce adequate levels of vitamin D. Food contains very little vitamin D. If supplementation is the only source of vitamin D, then recommending a change from 200 IU to 400 IU is akin to going from ridiculously low to just really bad; it is not going to do the job.
Dr. John Cannell of the Vitamin D Council recommends a minimum of 1,000 IU daily for children in the absence of sunlight exposure. He and other scientists also recommend 1,000 IU per 25 pounds of bodyweight in order to bring blood vitamin D to the optimal levels of 50 ng/ml.
It is unfortunate that government organizations usually recommend vitamin D intake that ranges from about 10-25% of the amount needed for optimal health. Those recommendations, coupled with the “sunscare movement” that has frightened the people away from natural, non-burning sunlight exposure, has been a disaster for children and adults alike and has led to an epidemic of autism, type one diabetes and weak bones in children. Hopefully, sanity will soon be restored and our children’s mental and physical health recovered.
 Cannell, J. et al. Cod Liver Oil, Vitamin A Toxicity, Frequent Respiratory Infections, and the Vitamin D Deficiency Epidemic. Ann Otol Rhinol Laryngol 2008;117:864-870.)