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The Role of Vitamin D

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The Role of Vitamin D

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April 3, 2009

A University of Georgia nutrition researcher has been awarded a $2.2 million grant to explore the role vitamin D plays in children's health and the appropriate dose children should take as daily supplements in order to maintain healthy levels of vitamin D in their bloodstream.

The grant, awarded by the National Institutes of Health Eunice Kennedy Shriver National Institute of Child Health and Human Development, comes on the heels of an Aug. 3 report in the journal Pediatrics showing 60 percent of children and adolescents had insufficient levels of vitamin D.

"The findings in Pediatrics confirmed what we have been seeing in our research," said Rick Lewis, professor of foods and nutrition in the UGA College of Family and Consumer Sciences. "In prior research we've conducted with female children and adolescents over the course of seven years, we've consistently found that they have lower levels of vitamin D than are recommended and that those levels drop as they grow older."

Although vitamin D has long been considered essential for bone health in individuals of all ages, research on the vitamin has primarily focused on its impact in older adults, Lewis said. Research on older adults also has shown links between vitamin D deficiencies and cancer, diabetes and obesity.

Although it's recommended that adults maintain a level of vitamin D in their blood stream that equates to 80 nanomoles per liter, the needs of children haven't been fully established. Currently, the Food and Nutrition Board at the Institute of Medicine recommends children under the age of 13 receive 200 international units daily, while the American Academy of Pediatrics recommends children receive 400 international units.

The sun has always been considered a primary source of vitamin D because it causes the vitamin to be synthesized in the skin. However, for those with darker skin, those living in areas where the sun doesn't shine as frequently, and those who either wear sunblock or don't get out in the sun for other reasons, supplements have long been considered important in ensuring individuals have enough vitamin D.

During the two-year study, Lewis and fellow UGA researchers Emma Laing, Dorothy Hausman and Dan Hall will team with Connie Weaver of Purdue University in providing varying doses of vitamin D supplements to boys and girls ranging in age from 9-13, ages deemed as being on the cusp of rapid growth periods. The group also will be evenly divided racially because research has consistently shown that African-American children tend to have lower levels of vitamin D than white children. One goal of the new study is to determine if African-American children and white children respond differently to oral supplements of vitamin D. Another collaborator on the project is Michael Kimlin of Queensland University of Technology in Australia, who will help in collecting sun exposure data for the study.

During the study, researchers will look at several biochemical measures of bone health, including calcium absorption, to determine the appropriate dose of vitamin D supplements children need to ensure that they grow up with strong, healthy bones.