Study conducted at the Children’s Hospital Boston showed some surprising results when Kendrin R. Sonneville, Sc.D., R.D and his colleagues examined the relation between risk of stress fractures in growing girls and their intake of calcium, Vitamin D and/or dairy products. (4)
Stress fractures usually occur due to overuse of a particular bone or set of bones. In other words, they arise out of repeated strain on a bone. Stress fractures are incomplete fractures and occur when muscles become fatigued due to overuse/repeat movement without adequate rest and recovery. These muscles are unable to absorb shock of the movement and transfer the repeat stress overload to the bones which develop microscopic cracks or fractures. They most commonly occur in the lower leg and feet. High impact physical activities such as running on hard surfaces, tennis, squash, basketball put one to risk of stress fractures especially brought on by improper form, weak bones and inadequate rest. (1)
The study which was named ‘The Growing Up Today Study’, examined 6712 pre-adolescent girls between the ages 9 and 15 was published in the Online First by Archives of Pediatrics & Adolescent Medicine, one of the JAMA/Archives journals. The findings pointed that it was Vitamin D and not as much calcium or dairy products that had a direct impact on occurrence of stress fractures among the said age group and especially in those girls who were involved with high impact activities and/or were physically very active. (2)
So there is now a challenge to the earlier education that growing children should consume calcium-rich dairy products everyday and take additional calcium supplements during the growing years.
‘The Growing Up Today Study’ included a seven year follow-up of the 9-15 age group of the 6,712 pre-adolescent girls and found that approximately 3.9 percent of the girls developed a stress fracture despite adequate intakes of calcium and dairy-rich products through their diet, clearly showing that either of the two factors were unrelated to the risk. However, adding or taking away Vitamin D from their diet showed a corresponding change in the risk of developing the stress fracture especially in those children who were involved in at least an hour of high-impact physical activity a day.
According to the authors of the study, “In contrast, there was no evidence that calcium and dairy intakes were protective against developing a stress fracture or that soda intake was predictive of an increased risk of stress fracture or confounded the association between dairy, calcium or vitamin D intakes and fracture risk.” (3)
Some rich sources of Vitamin D are mushrooms, cod liver oil, Salmon, tuna, sardines, mackerel, eggs, cheese, green leafy vegetables and a moderate dose of sunshine. As per the Institute of Medicines, 400-600 IU (international units) of Vitamin D are considered adequate for pre-adolescents, preferably coming in through diet as opposed to supplements.
Among all the forms of Vitamin D, D3 is considered most suitable by pediatric orthopaedicians as it is naturally available in various foods.
Another finding of the study worth mentioning is that a stratified analysis of the children under study showed that a higher intake of calcium actually increased the risk of developing stress fractures. As this finding was rather unexpected, the authors suggested further research into the matter. They were also of the opinion that a more detailed study needed to be done to determine if Vitamin D taken as supplements (Vitamin D2) would confer the same benefits to children as would taking it in the natural D3 form available in foods.
- Stress Fractures; American Academy of Orthopaedic Surgeons – Ortho Info; March 2012; http://orthoinfo.aaos.org/topic.cfm?topic=a00112
- Vitamin D Intake May Be Associated With Lower Stress Fracture Risk in Girls; Science Daily News; March 2012; http://www.sciencedaily.com/releases/2012/03/120305173453.htm
- Vitamin D Intake May Reduce Fracture Risk In Girls; Medical News Today; March 2012; http://www.medicalnewstoday.com/articles/242565.php
- Vitamin D, Calcium, and Dairy Intakes and Stress Fractures Among Female Adolescents; Archives of Pediatrics & Adolescent Medicine; March 2012; http://archpedi.jamanetwork.com/article.aspx?articleid=1149502
- Vitamin D Intake May Reduce Stress Fracture Risk in Adolescent Girls; Medscape Education; MArch 2012; http://www.medscape.org/viewarticle/759881