News Author: Megan Rauscher
CME Author: Penny Murata, MD
August 4, 2006 — In a study of healthy adolescent girls, subclinical hypovitaminosis D was a relatively common finding, with non-white girls more severely affected. According to the UK-based study team, "reduced sunshine exposure rather than diet explained the difference in vitamin D status of white and non-white girls" in the study.
"Vitamin D deficiency during childhood and adolescence," warn Dr. M. Zulf Mughal and colleagues in the July issue of the Archives of Disease in Childhood, "might impair the acquisition of peak bone mass at the end of skeletal growth and maturation, thereby increasing the risk of osteoporotic fracture later in life."
Dr. Mughal, from Saint Mary's Hospital for Women and Children in Manchester, and colleagues determined the prevalence of hypovitaminosis D in 51 girls (14 white, 37 non-white) ranging in age from 14.7 to 16.6 years attending an inner city multiethnic girls' school in the UK.
Thirty-seven girls (73%) were vitamin D deficient, having 25-hydroxyvitamin D [25OHD] levels less than 30 nmol/L and 9 (17%) were severely deficient, with 25OHD levels less than 12.5 nmol/L.
Median 25OHD levels were higher in white girls than in non-white girls (37.3 nmol/L versus 14.8 nmol/L).
For the group as a whole, the 25OHD concentration correlated with the estimated duration of daily sunlight exposure and percentage of body surface area exposed, but not with estimated intake of vitamin D.
"This is in keeping with the fact that the main source of vitamin D is that produced by the action of solar ultraviolet B radiation acting on 7-dehydrocholesterol in skin," the team points out. "Only small amounts are obtained from dietary sources."
As they note, "Avoidance of exposure to sunshine for religious and cultural beliefs that encourage wearing of concealing clothing and restriction of outdoor activities has previously been reported as a risk factor for vitamin D deficiency in Saudi Arabian adolescents."
In an editorial, Dr. N. J. Bishop, from the University of Sheffield, UK, comments that despite the low levels of vitamin D in the 37 girls, "there were no clear functional consequences with immediate impact." Dr. Mughal's group did not find that muscle function was related to vitamin D status.
Nevertheless, "the concern remains that failure to supply an essential nutrient during a period of rapid growth and development is likely to result in problems across the population as a whole," Dr. Bishop writes.
"We need to take simple, practical measures to reduce the burden of early bone disease and other later problems," Dr. Bishop concludes. These include reminding women that breast milk lacks vitamin D and that totally breastfed infants should be supplemented (irrespective of skin color) until receiving a full mixed diet.
It remains to be determined, Dr. Bishop adds, how to meet the needs of older children and adolescents from cultures that avoid sunlight. "Perhaps more exercise outdoors would help deal with this problem."
SOURCE: Arch Dis Child 2006 (Jul); 91 (7): 549–550