title: Vitamin D status, dietary intake, and bone turnover in female Soldiers during military training: a longitudinal study.
abstract: BACKGROUND
  Vitamin D is an essential nutrient for maintaining bone health, to include protecting against stress fracture during periods of rapid bone turnover. The objective of this longitudinal, observational study was to assess vitamin D status, biomarkers of bone turnover, and vitamin D and calcium intake in female Soldiers (n = 91) during US Army basic combat training (BCT).
  
  
  METHODS
  Anthropometric, biological and dietary intake data were collected at wk 0, 3, 6, and 9 of the 10 wk BCT course. Mixed models repeated measures ANOVAs were used to assess main effects of time, race, and time-by-race interactions.
  
  
  RESULTS
  White volunteers experienced a decrease in serum 25(OH)D levels, whereas non-white volunteers experienced an increase during BCT. However, serum 25(OH)D levels were lower in non-whites than whites at all timepoints (P-interaction < 0.05). Group mean PTH levels increased (P < 0.05) during the first 3 wk of training, remained elevated for the duration of BCT, and were higher in non-whites compared to whites (P-race < 0.05). Biomarkers of both bone formation (bone alkaline phosphatase and procollagen I N-terminal peptide) and resorption (tartrate-resistant acid phosphatase and C-terminal telopeptide) increased (P < 0.05) during BCT, indicating increased bone turnover. Estimated daily intakes of vitamin D and calcium were below recommended levels (15 μg and 1000 mg/day, respectively), both before (group mean ± SEM; 3.9 μg/d ± 0.4 and 887 mg/d ± 67) and during BCT (4.1 μg/d ± 0.3 and 882 mg/d ± 51).
  
  
  CONCLUSIONS
  These findings demonstrate that female Soldiers experience dynamic changes in vitamin D status coupled with increased bone turnover and potentially inadequate vitamin D and calcium intake during military training.
authors.affiliation: Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. James.McClung3@us.army.mil.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Lutz
authors.forename: J Philip
authors.initials: JP
authors.lastname: Karl
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Rood
authors.forename: Sonya J
authors.initials: SJ
authors.lastname: Cable
authors.forename: Kelly W
authors.initials: KW
authors.lastname: Williams
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Young
authors.forename: James P
authors.initials: JP
authors.lastname: McClung