Vitamin D linked to stronger bones in girls

Vitamin D may be helpful in protecting highly active pre-teen and teen girls, such as those who play sports, from stress fractures, researchers reported Monday.

The study was surprising because calcium has long been considered the nutrient most vital to bone health in children. But, in developing children, vitamin D intake may matter more.

Researchers analyzed data from 6,721 girls ages 9 to 15 at the start of the study. The girls’ intake of calcium, vitamin D and dairy products was recorded along with stress fractures, which are common sports-related injuries. The girls were followed for seven years.

During that time, almost 4% of the girls developed a stress fracture. Dairy and calcium intake seemed to bear no relationship to the risk of a stress fracture. However, girls with the highest vitamin D intake had a 50% lower risk of stress fracture compared with the girls who had the lowest intake. This was especially evident among girls who participated in at least one hour a day of high-impact physical activity. They had a 52% decreased risk.

Surprisingly, high calcium intake was associated with a doubling of the risk of stress fracture. However, the authors, from Children’s Hospital Boston, said that this “unexpected finding” should be further investigated.

Soda intake did not alter the fracture. The risk was also unchanged when calcium and vitamin D from food only (excluding supplements) were considered.

In 2010, the Institute of Medicine recommended adolescents consume 600 international units per day of vitamin D -- up from the previous recommendation of 400 IU per day. Researchers were unable to assess whether even higher levels of vitamin D intake may be more protective, but the question should be studied, they noted.

The study was published online in the Archives of Pediatric and Adolescent Medicine.

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