WEDNESDAY, May 4, 2011 (HealthDay News) -- Low levels of vitamin D are common in obese adolescents, a new study finds.
Researchers screened 68 obese adolescents and found low vitamin D levels in all of the girls (72 percent were deemed deficient and 28 percent insufficient) and in 91 percent of the boys (69 percent deficient and 22 percent insufficient).
After treatment, 43 of the youths had their vitamin D levels measured again and, although levels generally increased, normal levels were achieved in just 28 percent of the participants. In the others, repeated bouts of vitamin D treatment did not bring the teens' vitamin D levels to normal, which the researchers described as "concerning."
The adolescents' lack of response to treatment may be due to the fact that vitamin D is sequestered in body fat, the researchers said.
"The prevalence of low vitamin D status among obese adolescents in this study is greater than previously reported for this age group," Dr. Zeev Harel, a pediatrician specializing in adolescent medicine at Hasbro Children's Hospital in Providence, R.I., and the study's lead author, said in a hospital news release.
The study was published in the May issue of the Journal of Adolescent Health.
Vitamin D is produced by the skin in response to exposure to sunlight. It is also found in certain foods, including eggs, fish and fortified foods such as dairy products and breakfast cereals.
"It is possible that the association between obesity and low vitamin D status is indirect, arising from obese individuals having fewer outdoor activities than lean individuals and, therefore, less exposure to sun," the researchers wrote. "Likewise, it is also possible that obese individuals do not consume enough foods that contain vitamin D."
They called for closer monitoring of vitamin D levels in obese adolescents and for more research to determine if restoring normal vitamin D levels could help reduce the health risks associated with obesity.
Obesity -- now estimated to affect 16.4 percent of kids and teens between 10 and 17 -- can increase the risk of high blood pressure, heart disease, and type 2 diabetes, as well as some types of cancer, the researchers noted.
The U.S. Office of Dietary Supplements has more about vitamin D.