Vitamin D often low in seemingly healthy girls

In a study of healthy adolescent girls, researchers found that insufficient vitamin D levels were 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, reported in the Archives of Disease in Childhood.

“Vitamin D deficiency during childhood and adolescence,” warn Dr. M. Zulf Mughal and colleagues, “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.”

Mughal, from Saint Mary’s Hospital for Women and Children in Manchester, and colleagues measured vitamin D levels in 14 white and 37 non-white 14-16-year-old girls attending an inner city multi-ethnic girls’ school in the UK.

Thirty-seven girls (73 percent) were vitamin D deficient, and nine (17 percent) were severely deficient.

Average vitamin D levels were higher in white girls than in non-white girls.

For the group as a whole, the vitamin D 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 explains. “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, expresses concern 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.”

He writes, “We need to take simple, practical measures to reduce the burden of early bone disease and other later problems.” 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, 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: Archives of Disease in Childhood, July 2006.

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