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NEW YORK (Reuters Health) - Giving school children very high doses of vitamin D is safe, and may be necessary to bring their blood levels of the nutrient up to the amount necessary for optimum bone growth and health, a new study shows.
Insufficiency in vitamin D is common in children around the world, but there is little data on how much supplementation kids need, or even how much vitamin D they should have in their blood, Dr. Ghada E.-Hajj Fuleihan of the American University of Beirut in Lebanon told Reuters Health. "In the pediatric literature, we don't have a lot to guide us," she said.
In a previous study, Fuleihan and colleagues found that giving 10- to 17-year-olds relatively high doses of vitamin D3 increased their bone mass and bone area, as well as lean mass. In the current study, they report on both the short- and long-term safety of high-dose supplementation.
The short-term study included 25 school children randomly assigned to receive a placebo or 14,000 international units (IU) of vitamin D3 per week for eight weeks. In the long-term study, 340 study participants took placebo, 1,400 IU weekly, or 14,000 IU a week, and were followed up at six and 12 months.
Currently, the Institute of Medicine recommends a daily vitamin D3 intake of 200 IU for children. The high dosage used in the current study was 2,000 IU daily, or 10 times that amount.
No signs of vitamin D intoxication were seen in any of the children, while levels of the vitamin in children treated short-term rose from 44 to 54 nanograms per milliliter (ng/mL).
In the long-term study, levels rose from 15 to 19 ng/mL in children given 1,400 IU weekly and from 15 to 36 ng/mL in the higher-dose group. Levels were initially higher in the short-term study because it was conducted among children in a higher socioeconomic group, and took place in the summer, when kids are likely to get ample sunshine and thus have adequate blood levels of the vitamin, Fuleihan and her team explain in the Journal of Clinical Endocrinology and Metabolism.
Based on studies in adults, Fuleihan said, blood levels of vitamin D below 5 ng/mL are agreed to represent deficiency, while levels above 20 ng/mL are considered adequate and most experts say 30 ng/mL is ideal.
Because every additional 100 IU of vitamin D3 consumed produces a roughly 1 ng/mL increase in blood levels, high doses may be needed for children with vitamin D insufficiency, the researcher said.
Nevertheless, she added, more research is needed to understand how much vitamin D children should be getting, and whether there are health effects of vitamin D insufficiency beyond bone and muscle, as studies in adults suggest.
"The pediatric literature is lagging maybe 10 to 15 years behind the adult literature in understanding the impact of low vitamin D on health," the researcher said.
SOURCE: Journal of Clinical Endocrinology and Metabolism, July 2008.