July 9, 2007 -- Hours of playing video games and drinking sodas instead of milk may be putting children's bones at risk from low vitamin D levels.
Vitamin D-fortified milk is the main source of vitamin D in the diet, but the vitamin is also produced within the body as a result of sunlight exposure.
That's why researchers say those low vitamin D levels may reflect current trends of children spending less time outdoors and drinking less milk than in the past.
Severely low levels of vitamin D can lead to muscle weakness, bone weakness, and rickets. Earlier studies -- cited by the researchers -- show that vitamin D also plays an important role in immune system function.
Vitamin D and Kids
In the study, published in the American Journal of Clinical Nutrition, researchers analyzed blood levels of vitamin D in 382 healthy children from ages 6 to 21.
They found 55% of the children had lower than recommended vitamin D levels.
African-American children, children over age 9, and those who didn't get much vitamin D in their diet were the most likely to have low levels of the vitamin in their blood.
Vitamin D levels also dropped during winter. Overall, 68% of children had inadequate stores of the vitamin in their blood during the colder months when they spent more time indoors.
"Vitamin D deficiency remains an under-recognized problem overall, and is not well studied in children," says researcher Babette Zemel, PhD, a nutritional anthropologist at Children's Hospital of Philadelphia, in a news release.
Zemel says more study is needed to determine appropriate blood levels of vitamin D in children, and a review of current recommendations for vitamin D intake may be needed.