A retrospective study of a cohort of 124 patients with stress fractures of the foot showed that 83% of them had circulating serum 25-hydroxyvitamin D levels below 40 ng/mL. These results suggest that active patients at higher risk of stress factures may require a higher vitamin D intake than the average individual.
The key physiological function of vitamin D is to ensure adequate bone mineralization and turnover through maintenance of serum calcium and phosphorous levels. Insufficiency can lead to osteoporosis, reduced bone mineral density and increased risk of bone fracture. The current retrospective study looked at circulating serum25-hydroxyvitamin D levels in patients measured within three months of the diagnosis of a stress fracture of the foot (1). The Vitamin D Council defines sufficiency as serum 25-hydroxyvitamin D levels of 40 ng/mL. The study found that 83% of the patients with stress fractures had levels below this.
Previously, a double-blind, placebo-controlled trial carried out with female military recruits had shown that the incidence of stress fractures could be reduced by 20% with a daily intervention of 2000 mg calcium and 800 IUvitamin D (2). In a similar case-controlled study of 600 female navy recruits, it was shown that those with serum vitamin D levels of less than 20 ng/mL were twice as likely to suffer a fracture of the leg than those with levels of 40 ng/mL or more (3).
The Endocrine Society has suggested that adults with vitamin D deficiency should supplement with 6000 IU per day for eight weeks in order to achieve serum 25-hydroxyvitamin D levels of greater than 30 ng/mL (4). Hence, it appears that greater serum concentrations of vitamin D than previously thought may be required to prevent stress fractures in active individuals.