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PHILADELPHIA, July 9 -- Many otherwise healthy children and adolescents have low vitamin D levels, which may put them at risk for bone diseases such as rickets. African American children, children above age nine and with low dietary vitamin D intake were the most likely to have low levels of vitamin D in their blood, according to researchers from The Children's Hospital of Philadelphia.

A study in the current issue of the American Journal of Clinical Nutrition measured blood levels of vitamin D in 382 healthy children between six years and 21 years of age living in the northeastern U.S. Researchers assessed dietary and supplemental vitamin D intake, as well as body mass, and found that more than half of the children had low blood levels of vitamin D. Of the subjects, 55 percent of the children had inadequate vitamin D blood levels and 68 percent overall had low blood levels of the vitamin in the wintertime.

"The best indicator of a person's vitamin D status is the blood level of a vitamin D compound called 25-hydroxyvitamin D," said Babette Zemel, Ph.D., a nutritional anthropologist at Children's Hospital and primary investigator of this study. "Vitamin D deficiency remains an under-recognized problem overall, and is not well studied in children." Vitamin D is crucial for musculoskeletal health. The primary dietary source of the vitamin is fortified milk, but the best way to increase vitamin D levels is from exposure to sunshine. Severe deficits in vitamin D may lead to muscle weakness, defective bone mineralization and rickets. In addition to musculoskeletal effects, vitamin D is important for immune function, and low blood levels of the vitamin may contribute to diseases such as hypertension, cancer, multiple sclerosis and type 1 diabetes. Decreased blood levels of vitamin D have also been linked to obesity. Further study is needed to determine the appropriate blood levels of vitamin D in children, said Dr. Zemel, who added that a review of the current recommendations for vitamin D intake is needed. Grants from the National Institutes of Health and several private sources supported this study.

Dr. Zemel's co-authors were Mary B. Leonard, M.D. and Virginia A. Stallings, M.D., of The Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine, as well as Francis L. Weng and Justine Shults, also of the University of Pennsylvania School of Medicine. About The Children's Hospital of Philadelphia: The Children's Hospital of Philadelphia was founded in 1855 as the nation's first pediatric hospital. Through its long-standing commitment to providing exceptional patient care, training new generations of pediatric healthcare professionals and pioneering major research initiatives, Children's Hospital has fostered many discoveries that have benefited children worldwide. Its pediatric research program is among the largest in the country, ranking third in National Institutes of Health funding. In addition, its unique family-centered care and public service programs have brought the 430-bed hospital recognition as a leading advocate for children and adolescents.

www.chop.edu