Low Vitamin D, Stress Fractures Often Go Together – MedPage Today

Active adults with serum vitamin D values under 40 ng/mL had an elevated risk for stress fractures regardless of their age, according to a retrospective, cohort study.

The study was small, with just 53 patients who had serum 25(OH)D concentrations measured within 3 months of having a stress fracture, but roughly half had vitamin D levels that qualified as insufficient or deficient under standards recommended by The Endocrine Society, reported Jason R. Miller, DPM, of Premier Orthopaedics and Sports Medicine in Malvern, Pa., and colleagues.

And more than four out of five had non-optimal vitamin D levels under standards set by the Vitamin D Council, which considers a serum 25(OH)D range of 40 to 80 ng/mL to be sufficient, they wrote in the Journal of Foot & Ankle Surgery.

While acknowledging that larger, prospective studies are needed to determine if vitamin D supplementation reduces stress fracture risk, Miller said he believes clinicians should consider testing their active adult patients to determine their vitamin D status, especially if they have had a stress fracture.

“I have patients come in with stress fractures who tell me that they recently started taking a spin class or doing some other exercise,” he told MedPage Today. “The reality is, [the stress fracture] isn’t normal. The body should be able to handle that level of stress, and build bone in response to that stress.”

He added that maintaining a serum vitamin D level of at least 40 ng/mL may help people who regularly participate in high-impact activities avoid stress fractures.

The study is not the first to suggest a link between sub-optimal vitamin D levels and stress fractures in otherwise healthy active adults. A recently published review suggested an association between low serum 25(OH)D levels and lower extremity stress fractures in military personnel. In a 2008 randomized trial involving female navy recruits, vitamin D-calcium supplementation appeared to significantly lower stress fracture risk.

Miller and colleagues included 124 patients treated for stress fractures at a single orthopaedic and sports medicine practice. Two-thirds (66%) were female, the median patient age was 43.92, and the mean patient body mass index (BMI0 was 26.81 kg/m2.

The most common site of stress fracture was the second metatarsal bone (33.9%), followed by the third metatarsal (17.7%).

Serum 25(OH)D levels were recorded within 3 months of diagnosis in 53 (42.74%) of the patients. Forty-four of these patients (83.02%) had serum 25(OH)D levels of <40 ng/mL.

The mean serum 25(OH)D level among tested patients was 31.4 ng/mL and similar mean serum levels were reported for the males and females.

Miller noted that while vitamin D thresholds have been published by groups like the Endocrine Society and Vitamin D Council, there is still no consensus on the level of serum vitamin D needed for optimum health.

Miller and colleagues recommend a serum 25(OH)D of ≥40 ng/mL for stress fracture prophylaxis in active patients with a high functional demand.

But they noted that 16.9% of the patients in the study had serum 25(OH)D levels above 40 ng/mL, “indicating that vitamin D is not the sole predictor in the occurrence of a stress fracture.”

“Other factors, including white race, female gender, nicotine and alcohol abuse, steroid use, low bone density, low body mass index and bisphosphonate therapy have all shown correlations with the development of stress fractures,” they wrote. “Patients who regularly exercise or enjoy participating in higher impact activities should be advised on proper and gradual training regimens to reduce the risk of the development of a stress fracture.”

The Endocrine Society recommends supplementation with 50,000 IU of vitamin D2 or vitamin D3 once a week for 8 weeks or 6000 IU daily in adults with 25(OH)D levels under 30 ng/mL to raise levels above this threshold.

Miller and co-authors disclosed no relevant relationships with industry.

  • Reviewed by
    Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

last updated 12.16.2015


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