Doctors out of Israel have recently reported in the Journal of the International Society of Sports Nutrition that low nutritional intake is associated with increased risk of bone leg stress fractures in elite military recruits.
The team of researchers took a variety of measurements in 74 male combat recruits (average age 18 years old) at the beginning of a 4 month training program, after the program, and then again two months later. They measured:
- Changes in body measures, dietary intake, hemoglobin (Hgb), iron, transferrin, ferritin, folic acid, vitamin B12, calcium, and vitamin D [25(OH)D].
Note that this was not an interventional study. What they wanted to see is if there were any relationships between these measurements and incidence of long bone leg stress fractures. Stress fractures are a major problem in military training.
Throughout the 6 month period, 12 recruits got long leg stress fractures, while 62 did not. The researchers found:
- There was dietary deficiency before training.
- During training, the recruits’ nutritional intake (both groups) did not meet the recommendations for total energy and most nutrients, including carbohydrates, total fat, folate, vitamin D, calcium, zinc, and magnesium. They note the diet may be adequate, but not fully consumed (there were 3 meals and 3 snacks/day).
- Those who got stress fractures developed iron deficiency and anemia symptoms. Iron status is associated with stress fracture risk.
- 25(OH)D levels were a little higher in those that didn’t get a stress fracture, but nothing significant:
The authors note that in a study in 2008, Lappe et al found a 20% reduction in stress fractures in Navy recruits by supplementing with vitamin D and calcium. But the Israeli authors concluded that vitamin D and calcium supplementation is not worth the 20% reduction.
I disagree. The US Army trains 130,000 soldiers a year and, if the Israel 16% rate were applied to the US Army, over 20,000 would suffer a stress fracture. A 20% reduction would prevent over 4,000 stress fractures per year, a substantial number.
However, it’s important to remember that bone strength is a complex, multi-factorial issue including bone geometry, exercise, over 20 nutrients, height, workload, mileage, footwear and access to medical care. Reducing stress fractures requires a comprehensive approach, not just vitamin D and calcium.
I think a best approach would be to intervene before training. Stress fractures significantly affect military training, both in terms of costs and readiness. Treating fractures is much more costly than preventing them. A few simple measures could include:
- Assign high-risk folks to either a longer, slower training program or a pre-training program, combined with appropriate dietary/supplement interventions.
- Improve military training design and diet, perhaps with appropriate fortified snacks. This includes better vitamin D intake.