Doses of 2,000 milligrams of calcium per day and 1,000 IU of vitamin D per day were associated with significant increases in bone mineral density and bone mineral content of men and women undergoing basic training at Fort Sill, Oklahoma.
Scientists from the US Army Research Institute of Environmental Medicine (Natick, MA), Louisiana State University System (Baton Rouge, LA), and Initial Military Training Center of Excellence (Fort Eustis, VA) also reported that the calcium-vitamin D combination maintained levels of parathyroid hormone (PTH) during basic training, which is an important result since PTH has been reported to increase during training and this has been linked to stress fractures.
Indeed, basic training puts a lot of stress on the skeleton and often results in injury. Between 2% and 5% of men and 8% and 21% of women are reported to suffer from a stress fracture during initial military training.
‘An effective countermeasure for preserving bone health’
“To our knowledge, this was the first study to document changes in bone geometry and strength as assessed by [peripheral quantitative computed tomography] during basic combat training and beneficial effects of Ca and vitamin D supplementation,” wrote the researchers in Bone.
The researchers didn’t measure whether the incidence of stress fractures were altered as a result of the intervention, but they not that the changes to the skeleton observed in the study would suggest that the calcium-vitamin D combination would be protective against stress fractures.
“These results also provide mechanistic insights, and importantly, document acute changes at the level of bone tissue in response to Ca and vitamin D during military training,” they wrote.
“The stabilization of [parathyroid hormone] through supplemental intake of Ca and vitamin D through a snack product may be an effective countermeasure for preserving bone health during military training.”
The researchers recruited 156 men and 87 women enrolled in basic training to participate in their randomized, double-blind, placebo-controlled trial. The recruits were randomly assigned to receive two snack bars per day with or without 2,000 mg of calcium and 1,000 IU of vitamin D for nine weeks of basic combat training.
Results showed that calcium levels increased in the calcium plus vitamin D group, and PTH levels remained unchanged. PTH levels in the placebo group were found to increase (p=0.051), added the researchers.
In addition, data obtained using peripheral quantitative computed tomography indicated that the calcium-vitamin D group improved bone health, particularly in the trabecular envelope.
“These data support a role for supplemental Ca and vitamin D in order to optimize the anabolic effect of basic combat training on bone and protect bone health during military training,” wrote the researchers. “The observed biochemical and related bone changes suggest a likely mechanism accounting for prior reports indicating that supplemental Ca and vitamin D intake during military training may reduce the risk of stress fracture.”
Volume 68, Pages 46-56, doi: 10.1016/j.bone.2014.08.002
“Calcium and vitamin D supplementation maintains parathyroid hormone and improves bone density during initial military training: A randomized, double-blind, placebo controlled trial”
Authors: Gaffney-Stomberg E, Lutz LJ, Rood JC, Cable SJ, Pasiakos SM, Young AJ, McClung JP.