Sonya J. Cable

Randomized, double-blind, placebo-controlled trial of iron supplementation in female soldiers during military training: effects on iron status, physical performance, and mood

BACKGROUND Decrements in iron status have been reported in female soldiers during military training. Diminished iron status adversely affects physical and cognitive performance. OBJECTIVE We wanted to determine whether iron supplementation could prevent decrements in iron status and improve measures of physical performance and cognitive status in female soldiers during basic combat training (BCT). DESIGN In this 8-wk randomized, double-blind, placebo-controlled trial, soldier volunteers (n = 219) were provided with capsules containing either 100 mg ferrous sulfate or a placebo. Iron status indicator assays were performed pre- and post-BCT. Two-mile running time was assessed post-BCT; mood was assessed by using the Profile of Mood States questionnaire pre- and post-BCT. RESULTS The BCT course affected iron status: red blood cell distribution width and soluble transferrin receptor were elevated (P < 0.05), and serum ferritin was lowered (P < 0.05) post-BCT. Iron supplementation attenuated the decrement in iron status; group-by-time interactions (P < 0.01) were observed for serum ferritin and soluble transferrin receptor. Iron supplementation resulted in improved (P < 0.05) vigor scores on the Profile of Mood States post-BCT and in faster running time (P < 0.05) in volunteers reporting to BCT with iron deficiency anemia. CONCLUSIONS Iron status is affected by BCT, and iron supplementation attenuates the decrement in indicators of iron status in female soldiers. Furthermore, iron supplementation may prove to be beneficial for mood and physical performance during the training period. Future efforts should identify and treat female soldiers or athletes who begin training regimens with iron deficiency or iron deficiency anemia.

Randomized, double-blind, placebo-controlled trial of an iron-fortified food product in female soldiers during military training: relations between iron status, serum hepcidin, and inflammation

BACKGROUND Iron status degrades in female soldiers during military training. Inflammation-mediated up-regulation of hepcidin, a key mediator of iron homeostasis, may be a contributing factor. OBJECTIVE We measured the efficacy of an iron-fortified food product for maintaining iron status in female soldiers during basic combat training (BCT) and examined relations between iron status, serum hepcidin concentrations, and inflammation. DESIGN A randomized, double-blind, placebo-controlled trial was conducted. Volunteers received an iron-fortified food product (total dose = 56 mg Fe/d) or a placebo twice daily during the 9-wk BCT course. Iron-status indicators, serum hepcidin concentrations, and markers of inflammation were measured pre- and post-BCT. RESULTS BCT affected iron status; serum ferritin concentrations decreased (P < or = 0.05), and concentrations of soluble transferrin receptor (sTfR) and hemoglobin and the red cell distribution width increased (P < or = 0.05). Consumption of the iron-fortified food product attenuated declines in iron status in iron-deficient anemic soldiers; a group-by-time interaction was observed for hemoglobin and sTfR concentrations (P < or = 0.05). Serum hepcidin concentrations were not affected by BCT; however, hepcidin concentrations were lower in iron-deficient anemic soldiers than in those with normal iron status (P < or = 0.05) and were positively associated with serum ferritin (P < or = 0.05) and C-reactive protein (P < or = 0.05) concentrations pre- and post-BCT. CONCLUSIONS Twice-daily consumption of an iron-fortified food product improved iron status in iron-deficient anemic soldiers but not in iron-normal or iron-deficient nonanemic soldiers. Serum hepcidin concentrations were not affected by training but were associated with iron status and inflammation pre- and post-BCT. This trial was registered at clinicaltrials.gov as NCT01100905.

Longitudinal decrements in iron status during military training in female soldiers

Fe is an essential micronutrient required for optimal cognitive and physical performance. Cross-sectional studies indicate that training degrades Fe status in female military personnel; however, longitudinal studies to measure the direct impact of military training on Fe status and performance have not been conducted. As such, the objective of the present study was to determine the longitudinal effects of military training on Fe status in female soldiers. Fe status was assessed in ninety-four female soldiers immediately before and following a 9-week basic combat training (BCT) course. Fe status indicators included Hb, erythrocyte distribution width (RDW), serum ferritin, transferrin saturation and soluble transferrin receptor (sTfR). A 2-mile (3.2 km) run test was performed at the end of BCT to assess aerobic performance. Fe status was affected by BCT, as all Fe status indicators, excluding Hb, were diminished (P < or = 0.01) at the end of BCT. Fe status indicators at the end of BCT (Hb and RDW) were associated (P < or = 0.05) with running performance, as was the change in sTfR over the training period (r 0.320; P < or = 0.05). In conclusion, Fe status in female soldiers is degraded during BCT, and degraded Fe status is associated with diminished aerobic performance. Female athletes and military personnel should strive to maintain Fe status to optimise physical performance.

Vitamin D status, dietary intake, and bone turnover in female Soldiers during military training: a longitudinal study

BackgroundVitamin 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).MethodsAnthropometric, 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.ResultsWhite 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).ConclusionsThese 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.

Calcium and vitamin D supplementation maintains parathyroid hormone and improves bone density during initial military training: A randomized, double-blind, placebo controlled trial

Calcium and vitamin D are essential nutrients for bone health. Periods of activity with repetitive mechanical loading, such as military training, may result in increases in parathyroid hormone (PTH), a key regulator of Ca metabolism, and may be linked to the development of stress fractures. Previous studies indicate that consumption of a Ca and vitamin D supplement may reduce stress fracture risk in female military personnel during initial military training, but circulating markers of Ca and bone metabolism and measures of bone density and strength have not been determined. This randomized, double-blind, placebo-controlled trial sought to determine the effects of providing supplemental Ca and vitamin D (Ca+Vit D, 2000mg and 1000IU/d, respectively), delivered as 2 snack bars per day throughout 9weeks of Army initial military training (or basic combat training, BCT) on PTH, vitamin D status, and measures of bone density and strength in personnel undergoing BCT, as well as independent effects of BCT on bone parameters. A total of 156 men and 87 women enrolled in Army BCT (Fort Sill, OK; 34.7°N latitude) volunteered for this study. Anthropometric, biochemical, and dietary intake data were collected pre- and post-BCT. In addition, peripheral quantitative computed tomography was utilized to assess tibia bone density and strength in a subset of volunteers (n=46). Consumption of supplemental Ca+Vit D increased circulating ionized Ca (group-by-time, P=0.022), maintained PTH (group-by-time, P=0.032), and increased the osteoprotegerin:RANKL ratio (group-by-time, P=0.006). Consistent with the biochemical markers, Ca+Vit D improved vBMD (group-by-time, P=0.024) at the 4% site and cortical BMC (group-by-time, P=0.028) and thickness (group-by-time, P=0.013) at the 14% site compared to placebo. These data demonstrate the benefit of supplemental Ca and vitamin D for maintaining bone health during periods of elevated bone turnover, such as initial military training. This trial was registered with ClincialTrials.gov, NCT01617109.

Vitamin D status in female military personnel during combat training

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.

Poor Iron Status Is Not Associated with Overweight or Overfat in Non-Obese Pre-Menopausal Women

Background: Associations between obesity and poor iron status have been described in children and adults. Proposed mechanisms for this association implicate a physiologic etiology, suggesting body fat accretion may progressively degrade iron status. However, the relationship between iron status and body composition in non-obese adults remains unclear. Objective: In this study we examined the relationship between body composition, inflammation, and iron status in healthy, non-obese, pre-menopausal females. Methods: Iron status was assessed using red cell distribution width, transferrin saturation, serum ferritin, and soluble transferrin receptor (sTfR). Tumor-necrosis factor-α provided a marker of inflammation, and body fat percentage (BF) was calculated from mean skinfold thickness measurements at 3 sites. Results: In this cohort (n = 207), the prevalence of iron deficiency was similar (p > 0.05) between normal and overweight (BMI 25.0–30.0 kg/m2), and normal and overfat (BF ≥30.0%) volunteers. There were no differences in individual iron status indicators, including sTfR, between overweight or overfat volunteers as compared to normal weight and normal fat peers. Logistic regression analyses indicated that overfat volunteers had a lower (p < 0.05) risk of iron deficiency, whereas overweight individuals demonstrated no change in relative risk as compared to peers. Conclusion: These findings suggest that, in non-obese adults, decrements in iron status are not associated with increasing adiposity.

Cardiometabolic Risk in US Army Recruits and the Effects of Basic Combat Training

Background Cardiometabolic disease risk in US military recruits and the effects of military training have not been determined. This study examined lifestyle factors and biomarkers associated with cardiometabolic risk in US Army recruits (209; 118 male, 91 female, 23±5 yr) before, during, and after basic combat training (BCT). Methodology/Principal Findings Anthropometrics; fasting total (TC), high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol; triglycerides (TG); glucose; and insulin were measured at baseline and every 3 wks during the 10 wk BCT course. At baseline, 14% of recruits were obese (BMI>30 kg/m2), 27% were cigarette smokers, 37% were sedentary, and 34% reported a family history of cardiometabolic disease. TC was above recommended levels in 8%, LDL in 39%, TG in 5%, and glucose in 8% of recruits, and HDL was below recommended levels in 33% of recruits at baseline. By week 9, TC decreased 8%, LDL 10%, TG 13%, glucose 6% and homeostasis model assessment of insulin resistance (HOMA-IR) 40% in men (P<0.05). In women, TC, LDL, glucose and HOMA-IR were decreased from baseline at weeks 3 and 6 (P<0.05), but were not different from baseline levels at week 9. During BCT, body weight declined in men but not women, while body fat percentage declined in both men and women (P<0.05). Conclusions/Significance At the start of military service, the prevalence of cardiometabolic risk in US military recruits is comparable to that reported in similar, college-aged populations. Military training appears to be an effective strategy that may mitigate risk in young people through improvements in lipid profiles and glycemic control.

Differential effects of military training on fat-free mass and plasma amino acid adaptations in men and women.

Fat-free mass (FFM) adaptations to physical training may differ between sexes based on disparities in fitness level, dietary intake, and levels of plasma amino acids (AA). This investigation aimed to determine FFM and plasma AA responses to military training, examine whether adaptations differ between male and female recruits, and explore potential associations between FFM and AA responses to training. Body composition and plasma AA levels were assessed in US Army recruits (n = 209, 118 males, 91 females) before (baseline) and every three weeks during basic combat training (BCT), a 10-week military training course. Body weight decreased in men but remained stable in women during BCT (sex-by-time interaction, P < 0.05). Fifty-eight percent of recruits gained FFM during BCT, with more (P < 0.05) females (88%) gaining FFM than males (36%). Total plasma AA increased (P < 0.05) during BCT, with greater (P < 0.05) increases observed in females (17%) then in males (4%). Essential amino acids (EAA) and branched-chain amino acids (BCAA) were increased (P < 0.05) in females but did not change in males (sex-by-time interaction, P < 0.05). Independent of sex, changes in EAA (r = 0.34) and BCAA (r = 0.27) from baseline were associated with changes in FFM (P < 0.05); greater (P < 0.05) increases in AA concentrations were observed for those who gained FFM. Increases in FFM and plasma AA suggest that BCT elicits a more pronounced anabolic response in women compared to men, which may reflect sex-specific differences in the relative intensity of the combined training and physiological stimulus associated with BCT.

Positive Effects of Basic Training on Cognitive Performance and Mood of Adult Females

Objective: This study investigated whether a stressful military training program, the 9- to 10-week U.S. Army basic combat training (BCT) course, alters the cognitive performance and mood of healthy young adult females. Background: Structured training programs including adolescent boot camps, sports training camps, learning enrichment programs, and military basic training are accepted methods for improving academic and social functioning. However, limited research is available on the behavioral effects of structured training programs in regard to cognitive performance and mood. Method: Two separate, within-subject studies were conducted with different BCT classes; in total 212 female volunteers were assessed before and after BCT. In Study 1, Four-Choice Reaction Time, Match-to-Sample, and Grammatical Reasoning tests were administered. The Psychomotor Vigilance Test (PVT) was administered in Study 2. The Profile of Mood States (POMS) was administered in both studies. Results: In Study 1, reaction time to correct responses on all three of the performance tests improved from pre- to post-BCT. In Study 2, PVT reaction time significantly improved. All POMS subscales improved over time in the second study, whereas POMS subscales in the first study failed to meet criteria for statistically significant differences over time. Conclusion: Cognition and mood substantially improved over military basic training. These changes may be a result of structured physical and mental training experienced during basic training or other factors not as yet identified. Application: Properly structured training may have extensive, beneficial effects on cognitive performance and mood; however, additional research is needed to determine what factors are responsible for such changes.