In the Journals

Sun exposure provides inadequate vitamin D in UK adolescents

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June 9, 2016

Adolescents in the United Kingdom did not get enough sunlight to receive healthy amounts of vitamin D in a study recently published in The Journal of Clinical Endocrinology & Metabolism, prompting researchers to recommend changes to British government guidelines on vitamin D intake. More than one-quarter of the adolescents in the study had inadequate vitamin D levels even during summer, the period when participants spent the most time outdoors.

“Current U.K. national guidance on vitamin D acquisition assumes those aged 4 to 64 years gain their vitamin D requirements from sunlight alone, thus there is no recommended nutrient intake,” Mark D. Farrar, BSc, PhD, of the Centre for Dermatology, Institute of Inflammation and Repair, University of Manchester, and colleagues wrote. “Meanwhile, substantial proportions of the global population, including the U.K., are reported to have low vitamin D status, and rickets has returned as a clinical concern.”

Farrar and colleagues conducted a prospective cohort study of white adolescents attending six schools — five fee-paying and one free — in the Greater Manchester area of the United Kingdom. The researchers obtained blood samples in January, April, June and September 2011 to determine 25-hydroxyvitamin D levels, and students (n = 131; aged 12-15 years) wore polysulphone film badge UV radiation dosimeters on their clothing for 1 week each season to record their exposure to sunlight, and filled out logs describing the time they spent outdoors.

Results of DXA on 19 participants who were considered deficient (25-[OH]D < 10 ng/mL/25 nmol/L) showed low femoral neck bone mineral apparent density.

The highest levels of mean 25-(OH)D occurred in September at 24.1 ng/mL, and the lowest levels were seen in January at 15.5 ng/mL. Sixteen percent of participants were deficient in at least one season, and 79% were insufficient (25-[OH]D < 20 ng/mL/50 nmol/L). In September, the testing period when 25-(OH)D levels were at their peak, 28% of participants were vitamin D insufficient, and 74% were insufficient in winter. Private school students had lower levels than their public school counterparts, with a mean 25-(OH)D level of 21.8 ng/mL vs. 24.6 ng/mL in June (P = .02).

“Our study highlights the value of repeated, seasonal measures, and shows a greater than anticipated potential for suboptimal bone health revealed in this age group,” the researchers wrote. “... As U.K. current sun-exposure patterns do not provide an adequate source of vitamin D, amendments are required to recommendations on vitamin D acquisition in this age group. While wider skin surface area exposure to sunlight might safely increase vitamin D status, oral vitamin D supplements may be beneficial during this critical time for bone development.” by Andy Polhamus

Disclosure: The researchers report no relevant financial disclosures.