The Impact of Sweat Calcium Loss on Bone Health in Soldiers: A Pilot Study
Name: Mary McCarthy
Rank: CAPT (ret)
Performance Site: Madigan Army Medical Center, Tacoma, WA; Designated Active, Guard or Reserve Combat Arms Units, Fort Lewis, WA; National Training Center, Fort Irwin, CA
Year Published: 2006
Abstract Status: Final
Sixty-eight percent (68%) of the current U.S. Army enlisted soldiers are between 17 and 29 years of age. This age range coincides with the period of peak bone mass, which occurs when the growth in the size of bones and the accumulation of bone mineral has stabilized. There is a possibility that the physical demands and the restricted diet in a wartime scenario may be detrimental to bone health. Armstrong et al. (1992) suggested that in soldiers, a substantial calcium deficit could accumulate over time because of the combined effect of sweat calcium losses and low dietary intake of calcium. More recent studies in athletes and firefighters confirm that a significant amount of calcium may be lost through sweat, but there is no good definition of how much is too much. This prospective, descriptive, longitudinal pilot study will recruit 50 male and female soldiers who will train at the National Training Center and then deploy for OEF/OIF. The study will examine the following three aims: 1) Determine the feasibility of quantifying calcium sweat loss in soldiers in a desert climate undergoing intense physical training; 2) Examine the significance of calcium loss on short-term bone health using biochemical markers of bone turnover, as well as dual-energy x-ray absorptiometry (DEXA) to assess bone mineral quality; and 3) Describe the potential impact of self-reported exercise and dietary habits on bone health of soldiers. Issues regarding feasibility will include the ability to recruit and retain sufficient eligible soldiers, the ability to collect all specimens to include serum and urine bone turnover markers, sweat for calcium quantification, and DEXA scans at baseline and one year post-deployment. Sweat collection will be done using the Tipton et al. method on 2 occasions in a desert climate. Biochemical markers of bone formation and resorption include osteocalcin, P1CP, and ICTP which will be measured in serum by chemiluminescence. Peptide bound N-telopeptide crosslinks (NTX) will be measured by immunoassay in the urine as a specific marker of bone resorption. Soldiers will complete the Baecke Habitual Physical Activity and the Block 2005 Food Frequency Questionnaires. Data analysis will include descriptive statistics using mean ┬▒ SD to report sample demographics and t-tests to examine baseline and post-deployment biochemical markers and DEXA results. Study findings will help determine if sweat calcium loss is sufficient to warrant a clinical trial that includes calcium supplementation for soldiers.
Final report is available on NTRL: https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/PB2013105804.xhtml