Vitamin D status in female military personnel during combat training

Nancy E Andersen, J Philip Karl, Sonya J Cable, Kelly W Williams, Jennifer C Rood, Andrew J Young, Harris R Lieberman, James P McClung, Nancy E Andersen, J Philip Karl, Sonya J Cable, Kelly W Williams, Jennifer C Rood, Andrew J Young, Harris R Lieberman, James P McClung

Abstract

Vitamin D is an essential nutrient for maintaining bone health. Recent data suggest that vitamin D and calcium supplementation might affect stress fracture incidence in military personnel. Although stress fracture is a health risk for military personnel during training, no study has investigated changes in vitamin D status in Soldiers during United States (US) Army basic combat training (BCT). This longitudinal study aimed to determine the effects of BCT on 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) levels in female Soldiers. Serum 25(OH)D and PTH were assessed in 74 fasted Soldier volunteers before and after an 8-week BCT course conducted between August and October in Columbia, South Carolina. In the total study population, 25(OH)D levels decreased (mean ± SD) from 72.9 ± 30.0 to 63.3 ± 19.8 nmol/L (P < 0.05) and PTH levels increased from 36.2 ± 15.8 to 47.5 ± 21.2 pg/mL (P < 0.05) during BCT. Ethnicity affected changes in vitamin D status (ethnicity-by-time interaction, P < 0.05); 25(OH)D decreased (P < 0.05) in both Hispanic and non-Hispanic whites, but did not change in non-Hispanic blacks. Ethnicity did not affect BCT-induced changes in PTH. These data indicate that vitamin D status in female Soldiers may decline during military training in the late summer and early autumn months in the Southeastern US. Future studies should strive to determine the impact of military clothing and seasonality on vitamin D status, as well as the functional impact of declining vitamin D status on bone health.

Figures

Figure 1
Figure 1
(A) Mean serum 25-hydroxyvitamin and (B) parathyroid hormone levels in female Soldiers pre- and post-basic combat training. Serum 25-hydroxyvitamin D, 25(OH)D; parathyroid hormone, PTH. n = 74; values are means ± SD. Asterisks (*) indicate significant differences (P < 0.05) from pre-values.
Figure 2
Figure 2
(A) Boxplots of serum 25-hydroxyvitamin D and (B) parathyroid hormone levels in female Soldiers pre- and post-basic combat training by ethnicity. Serum 25-hydroxyvitamin D, 25(OH)D; parathyroid hormone, PTH; basic combat training, BCT. n = 74; non-Hispanic white, n = 39; non-Hispanic black, n = 24; Hispanic white, n = 11. Boxes represent the middle 50th percentile, and vertical lines extend to the 10th and 90th percentiles. Median values are marked by a line within each box. Values below the 10th percentile or above the 90th percentile are identified by solid circles (•). A two-factor repeated measures ANOVA with Bonferroni adjustments was utilized to determine the effects of time and ethnicity on 25(OH)D and PTH levels. Asterisks (*) indicate significant differences between mean values pre- and post-BCT within ethnicities (P < 0.05). adifferences between mean values of non-Hispanic whites and non-Hispanic blacks pre-BCT (P < 0.01); bdifferences between mean values of non-Hispanic blacks and Hispanic whites pre-BCT (P < 0.05); cdifferences between mean values of all ethnic groups post-BCT (P < 0.05).

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