James P. McClung

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.

Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial

The purpose of this work was to determine the effects of varying levels of dietary protein on body composition and muscle protein synthesis during energy deficit (ED). A randomized controlled trial of 39 adults assigned the subjects diets providing protein at 0.8 (recommended dietary allowance; RDA), 1.6 (2X‐RDA), and 2.4 (3X‐RDA) g kg–1 d–1 for 31 d. A 10‐d weight‐maintenance (WM) period was followed by a 21 d, 40% ED. Body composition and postabsorptive and postprandial muscle protein synthesis were assessed during WM (d 9‐10) and ED (d 30‐31). Volunteers lost (P<0.05) 3.2 ± 0.2 kg body weight during ED regardless of dietary protein. The proportion of weight loss due to reductions in fat‐free mass was lower (P<0.05) and the loss of fat mass was higher (P<0.05) in those receiving 2X‐RDA and 3X‐RDA compared to RDA. The anabolic muscle response to a protein‐rich meal during ED was not different (P>0.05) from WM for 2X‐RDA and 3X‐RDA, but was lower during ED than WM for those consuming RDA levels of protein (energy × protein interaction, P<0.05). To assess muscle protein metabolic responses to varied protein intakes during ED, RDA served as the study control. In summary, we determined that consuming dietary protein at levels exceeding the RDA may protect fat‐free mass during short‐term weight loss.—Pasiakos, S. M., Cao, J. J., Margolis, L. M., Sauter, E. R., Whigham, L. D., McClung, J. P., Rood, J. C., Carbone, J. W., Combs, G. F., Jr., Young, A. J. Effects of high‐protein diets on fat‐free mass and muscle protein synthesis following weight loss: a randomized controlled trial. FASEB J. 27, 3837–3847 (2013). www.fasebj.org

Iron deficiency and obesity: the contribution of inflammation and diminished iron absorption

Poor iron status affects billions of people worldwide. The prevalence of obesity continues to rise in both developed and developing nations. An association between iron status and obesity has been described in children and adults. The mechanism explaining this relationship remains unknown; however, findings from recent reports suggest that body mass index and inflammation predict iron absorption and affect the response to iron fortification. The relationship between inflammation and iron absorption may be mediated by hepcidin, although further studies will be required to confirm this potential physiological explanation for the increased prevalence of iron deficiency in the obese.

Prevalence of Iron Deficiency and Iron Deficiency Anemia among Three Populations of Female Military Personnel in the US Army

Background: Iron deficiency is the most prevalent micronutrient deficiency disease in the world and occurs in young women in the United States. Female military personnel represent a unique population faced with intense physical and cognitive demands. Objective: The objective of this study was to determine the prevalence of iron deficiency and iron deficiency anemia among three populations of female military personnel in the US Army. Methods: Iron status was assessed in 1216 volunteers. Volunteers were recruited from three groups: immediately following initial entry to the Army (IET), immediately following basic combat training (AIT), or following at least six months of permanent assignment (PP). Iron deficiency was determined using a three variable model, including cut-off values for serum ferritin, transferrin saturation, and red cell distribution width (RDW). Iron deficiency anemia was categorized by iron deficiency and a hemoglobin (Hgb) value of <12 g/dL. Results: The prevalence of iron deficiency was greater in women in the AIT group (32.8%) than in the IET and PP groups (13.4 and 9.6%, respectively). The prevalence of iron deficiency anemia was greater in the AIT group (20.9%) than in the IET and PP groups (5.8 and 4.8%, respectively). Furthermore, the prevalence of iron deficiency anemia was greater in Hispanic (21.9%) and African-American military personnel (22.9%) than in Caucasian military personnel (10.5%). Conclusions: These data indicate that female military personnel experience diminished iron status following training, and that iron nutriture is an important issue facing females in the military.

Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis

BACKGROUND The effects of essential amino acid (EAA) supplementation during moderate steady state (ie, endurance) exercise on postexercise skeletal muscle metabolism are not well described, and the potential role of supplemental leucine on muscle protein synthesis (MPS) and associated molecular responses remains to be elucidated. OBJECTIVE This randomized crossover study examined whether EAA supplementation with 2 different concentrations of leucine affected post-steady state exercise MPS, whole-body protein turnover, and mammalian target of rapamycin 1 (mTORC1) intracellular signaling. DESIGN Eight adults completed 2 separate bouts of cycle ergometry [60 min, 60% VO(2)peak (peak oxygen uptake)]. Isonitrogenous (10 g EAA) drinks with different leucine contents [leucine-enriched (l)-EAA, 3.5 g leucine; EAA, 1.87 g leucine] were consumed during exercise. MPS and whole-body protein turnover were determined by using primed continuous infusions of [(2)H(5)]phenylalanine and [1-(13)C]leucine. Multiplex and immunoblot analyses were used to quantify mTORC1 signaling. RESULTS MPS was 33% greater (P < 0.05) after consumption of L-EAA (0.08 ± 0.01%/h) than after consumption of EAA (0.06 ± 0.01%/h). Whole-body protein breakdown and synthesis were lower (P < 0.05) and oxidation was greater (P < 0.05) after consumption of L-EAA than after consumption of EAA. Regardless of dietary treatment, multiplex analysis indicated that Akt and mammalian target of rapamycin phosphorylation were increased (P < 0.05) 30 min after exercise. Immunoblot analysis indicated that phosphorylation of ribosomal protein S6 and extracellular-signal regulated protein kinase increased (P < 0.05) and phosphorylation of eukaryotic elongation factor 2 decreased (P < 0.05) after exercise but was not affected by dietary treatment. CONCLUSION These findings suggest that increasing the concentration of leucine in an EAA supplement consumed during steady state exercise elicits a greater MPS response during recovery. This trial is registered at clinicaltrials.gov as NCT01366924.

Skeletal Muscle Responses to Negative Energy Balance: Effects of Dietary Protein

Sustained periods of negative energy balance decrease body mass due to losses of both fat and skeletal muscle mass. Decreases in skeletal muscle mass are associated with a myriad of negative consequences, including suppressed basal metabolic rate, decreased protein turnover, decreased physical performance, and increased risk of injury. Decreases in skeletal muscle mass in response to negative energy balance are due to imbalanced rates of muscle protein synthesis and degradation. However, the underlying physiological mechanisms contributing to the loss of skeletal muscle during energy deprivation are not well described. Recent studies have demonstrated that consuming dietary protein at levels above the current recommended dietary allowance (0.8 g · kg(-1) · d(-1)) may attenuate the loss of skeletal muscle mass by affecting the intracellular regulation of muscle anabolism and proteolysis. However, the specific mechanism by which increased dietary protein spares skeletal muscle through enhanced molecular control of muscle protein metabolism has not been elucidated. This article reviews the available literature related to the effects of negative energy balance on skeletal muscle mass, highlighting investigations that assessed the influence of varying levels of dietary protein on skeletal muscle protein metabolism. Further, the molecular mechanisms that may contribute to the regulation of skeletal muscle mass in response to negative energy balance and alterations in dietary protein level are described.

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.

Iron Nutrition and Premenopausal Women: Effects of Poor Iron Status on Physical and Neuropsychological Performance

Iron is a nutritionally essential trace element that functions through incorporation into proteins and enzymes, many of which contribute to physical and neuropsychological performance. Poor iron status, including iron deficiency (ID; diminished iron stores) and iron deficiency anemia (IDA; poor iron stores and diminished hemoglobin), affects billions of people worldwide. This review focuses on physical and neuropsychological outcomes associated with ID and IDA in premenopausal women, as the prevalence of ID and IDA is often greater in premenopausal women than other population demographics. Recent studies addressing the physiological effects of poor iron status on physical performance, including work productivity, voluntary activity, and athletic performance, are addressed. Similarly, the effects of iron status on neurological performance, including cognition, affect, and behavior, are summarized. Nutritional countermeasures for the prevention of poor iron status and the restoration of decrements in performance outcomes are described.

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.