Many kids and adolescents who are otherwise healthy have inadequate levels of vitamin D that is essential when it comes to preventing bone diseases such as rickets.
The findings are based on a study conducted by researchers from The Children's Hospital of Philadelphia, US, who analysed 382 healthy children between six years and 21 years of age.
The 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. Vitamin D deficiency remains an under-recognized problem overall, and is not well studied in children," said Babette Zemel, Ph.D., a nutritional anthropologist at Children's Hospital and primary investigator of this study.
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.
The researchers however added that further study is needed to determine the appropriate blood levels of vitamin D in children, as well as a review of the current recommendations for vitamin D intake.
The study appears in the current issue of the American Journal of Clinical Nutrition.