Vitamin D insufficiency is thought to play a role in a range of diseases, including bone and autoimmune disease, cancer, infection, and life-threatening conditions such as heart attack and stroke.
"Vitamin D synthesis in the skin from UVB exposure cannot be dissociated from acute and chronic photodamage, including photocarcinogenesis," said Dr. Ki-Young Suh. "Because it is has a relatively long half-life in the serum, 25(OH)D is the metabolite we use to measure the amount of vitamin D status."
The amount of vitamin D needed for good health remains controversial, noted Dr. Suh of the University of California, Los Angeles. The accepted level that has been shown to prevent rickets is 50 nmol/L, and any serum vitamin D level below that is considered deficient. Serum vitamin D levels of at least 75 nmol/L have been associated with preventing osteoporosis.
Recent studies have shown that the prevalence of vitamin D deficiency in the U.S. population is on the rise. Potential factors that impact serum vitamin D levels include sun exposure, diet, obesity, and the use of certain medications, Dr. Suh said at the seminar on women's and pediatric dermatology, which was sponsored by Skin Disease Education Foundation.
It has been questioned whether or not dermatologists contribute to the increased prevalence of vitamin D deficiency because of sun protection recommendations, Dr. Suh said. However, studies have shown that most Americans probably do not use sun protection properly or adequately enough to cause vitamin D deficiency.
Although in vitro studies of human skin show inhibition of vitamin D production with sunscreen use, real-life studies show that seasonal increases in serum vitamin D levels persist even when people use sunscreen, she said.
One key factor that may drive vitamin D deficiency is the increased amount of time children spend indoors, both at school and during leisure time. Adolescent girls in particular have been found to have the lowest amount of dietary vitamin D consumption, Dr. Suh said.
The American Academy of Pediatrics' latest recommendations on vitamin D were issued in 2008. The recommendations stated that serum vitamin D levels in children should be greater than 50 nmol/L to maintain good bone health. The AAP recommends a supplement of 400 IU of vitamin D for breastfed infants, for infants and children who consume less than 1 L/day of vitamin D–fortified milk or formula, and for adolescents whose diets are low in vitamin D.
Dr. Suh noted that these recommendations may not apply equally to all ethnic groups, and that children who are at increased risk of vitamin D deficiency may need additional supplementation.
Disclosures: Dr. Suh did not report having any conflicts of interest. SDEF and this news organization are owned by Elsevier.