Girls with the highest average intakes of vitamin D were 51% less likely to suffer from stress fractures, compared with girls with the lowest average intakes, according to findings published in theArchives of Pediatrics & Adolescent Medicine.
“Our findings support the Institute of Medicine’s recent increase in the Recommended Dietary Allowance for vitamin D for adolescents from 400 IU/d to 600 IU/d,” wrote researcher led by Kendrin Sonneville, ScD, RD, of Children’s Hospital Boston.
“Because too few participants had a vitamin D intake higher than 600 IU/d, we were unable to explore the potential benefits of vitamin D intake in excess of the Recommended Dietary Allowance.”
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 and -2 diabetes.
The new study adds to the bone health potential of vitamin D. Dr Sonneville and her co-workers explain that stress fractures, a relatively common sports-related injury, occur when stresses on a bone exceed its capacity to withstand and heal from those forces.
The Boston-based researchers analyzed data from 6,712 pre-adolescent and adolescent girls participating in the Growing Up Today Study. During seven years of follow-up, the researchers report that 3.9% of the girls developed a stress fracture.
Intakes of dairy and calcium did not influence the stress fracture risk, they said, but vitamin D was associated with a significant reduction in stress fracture risk.
“Given the limited knowledge of modifiable risk factors for stress fracture among adolescent girls, the results of this study provide important information regarding the role of dietary factors in the prevention of stress fracture,” wrote Dr Sonneville and her co-workers.
Source: Archives of Pediatrics & Adolescent Medicine
Published online, doi:10.1001/archpediatrics.2012.5
“Vitamin D, Calcium, and Dairy Intakes and Stress Fractures Among Female Adolescents”
Authors: K.R. Sonneville, C.M. Gordon, M.S. Kocher, L.M. Pierce, A. Ramappa, A.E. Field