Researchers report that 70 percent of U.S. children have insufficient levels in vitamin D. An article published this week in the online version of the journal Pediatrics describes a nationwide study in which researchers analyzed data on more than 6,000 children, ages 1 to 21, collected by the National Health and Nutrition Examination Survey from 2001 through 2004. The researchers found that 9 percent, or 7.6 million children were vitamin D deficient and another 61 percent, or 50.8 million, were vitamin D insufficient.

Low levels were especially common in girls, African-Americans, Mexican-Americans, the obese, those who drank milk less than once a week, and those who spent more than four hours a day watching TV, playing videogames, or using computers. The deficiency was more common among the older children in the data set, too. A separate article in the same journal links vitamin D deficiencies to higher risk for bone and heart disease. Humans can obtain vitamin D through dietary sources such as fish, dairy products and vitamin supplements, but vitamin D levels depend largely on exposure to sunlight, which helps the body convert a form of cholesterol into the vitamin. Researchers speculate that as children spend less time outdoors, more of them are at risk of disease due to vitamin D deficiencies. The reports are available in the online version of Pediatrics.