The Dietary Guidelines for Americans 2015–2020 indicate that potassium, choline, magnesium, calcium, vitamins A, D, E, and C are underconsumed (i.e., shortfall) micronutrients. Intakes of specific performance-related micronutrients (i.e., calcium, magnesium, folate, choline, iron, zinc, and vitamins A, D, E, B1, B2, B3, and B12), may also be a concern, as suboptimal intakes may limit adaptations to unaccustomed physical training, such as initial military training (IMT). Protein-containing foods are nutrient-dense; therefore, dietary protein intake may alter the amount of shortfall and performance-related micronutrients habitually consumed. This study explored associations between dietary protein (PRO) intake and shortfall or performance-related micronutrient intakes at IMT accession. A 3-month food frequency questionnaire was used to estimate habitual dietary intake in male (n = 276, age: Mean (SD), 21.1 (3.8)) and female (n = 254, age: 21.2 (3.7)) recruits. Multivariate-adjusted MANCOVA and ANCOVA models were used to identify associations between quartiles of PRO intake and shortfall micronutrients or performance-related micronutrients. Models were adjusted for age, sex, ethnicity, race, physical activity, energy density, and total energy intake. Mean (SE) energy-adjusted PRO intakes were 29.3 (3.2), 36.0 (1.4), 40.8 (1.3), and 47.7 (3.9) g/1000 kcal for quartiles 1–4, respectively. Composite shortfall micronutrient intake differed (P < 0.001) by PRO quartile, as intake of each micronutrient, except vitamin C, progressively increased (all, P < 0.05) with increasing PRO quartiles. Similarly, composite (P < 0.001), and most individual (all, P < 0.05) performance-related micronutrient intakes, except calcium, were different across PRO quartiles. Calcium intake only differed for PRO quartile 1 and was lower than all other quartiles (P < 0.00). These cross-sectional data suggest that habitually consuming more protein is associated with greater intakes of shortfall and performance-related micronutrients in young healthy adults entering the military. Supported by US Army Medical Research and Materiel Command; authors' views not official US Army or DoD policy.
Stress fracture incidence during military training is high. Prior work suggests calcium (Ca) and vitamin D (vit D) intakes above the RDA may reduce fracture incidence in female trainees. How Ca and vit D affect measures of bone density and strength during initial military training (IMT) is not known. This randomized, double‐blind, placebo‐controlled trial was conducted to determine whether Ca and vit D (2000 mg and 800 IU) delivered as 2 snack bars daily throughout 9 wks of IMT improved trainee bone health. Measures of bone density pre‐ and post‐IMT and strength were assessed using peripheral quantitative computed tomography (n=20 men, n=27 women). Tibia scans were performed on the non‐dominant leg at 4, 14 and 66% of the segment length proximal to the distal end plate. Several parameters increased during training including: trabecular volumetric bone mineral density (vBMD) and bone strength index at the 4% site, cortical vBMD at the 14% and 66% sites, and stress strain index at the 66% site suggesting bone strength improved during IMT (all P <0.05). Those who received Ca and vit D had greater increases in total vBMD at the 4% site (3.0 ± 3.3 vs. 1.2 ± 2.4%; P <0.05) as well as cortical thickness (1.9 ± 2.2 vs. 0.6 ± 1.8%; P <0.05) and bone mineral content (1.6 ± 1.6 vs 0.6 ± 1.8%; P <0.05) at the 14% site. These data indicate that Ca and vit D intakes above the RDA may support bone health during periods of high turnover such as IMT. Grant Funding Source : Research supported by: ORISE and USAMRMC.
Effects of dietary calcium (Ca) deficiency on skeletal integrity and endocrine parameters are well characterized in growing and mature mammals; however, little work has examined Ca nutrition during the neonatal period. In this study, we examined the effects of neonatal Ca nutrition on bone integrity, endocrine parameters, and in vivo mesenchymal stem cell (MSC) activity. Neonatal pigs (24 ± 6h post‐partum) were pair‐fed either a Ca adequate or a 30% Ca deficient liquid formula diet for 18 days. There were no differences in growth rate or feed conversion efficiency based on dietary Ca level and all pigs grew at a rate similar to sow‐reared pigs. As anticipated, dietary Ca deficiency reduced (P < 0.05) both BMD and bone flexural strength. The anticipated increase (P < 0.05) in plasma PTH levels in pigs fed the Ca deficeint diet was not evident until the end of the study. Surprisingly, dietary Ca level did not affect plasma Ca or 1,25(OH) 2 vitamin D concentrations throughout the study. Calcium deficiency reduced (P < 0.05) the in vivo proliferation of MSC isolated from bone marrow by approximately 50%. These results indicate that neonatal Ca nutrition is crucial for bone integrity and suggest that early life Ca restriction may have long‐term effects on bone integrity via its effects on MSC activity.
Consuming high protein during energy restriction (ER) promotes glycemic control. However, the extent to which protein source modulates the glycemic response and the intracellular mechanisms by which hepatic regulation of blood glucose is maintained during ER is not well described. Eighty male Sprague‐Dawley rats (12 weeks old) were randomly divided into 8 treatment groups and fed energy adequate (EA) or ER (60% of the ad libitum feed intake for EA) diets containing two levels (control: CP, 10%; and high protein: HP, 35%) and sources (milk protein concentrate: MPC; and low isoflavone soy concentrate: SOY) of protein for 16 weeks. Fasting serum insulin and glucose concentrations were assessed, and hepatic regulators of gluconeogenesis were analyzed using Western blot. Blood glucose was similar across groups (group mean ± SD, 109 ± 11 mg/dL, P > 0.05). However, insulin levels were lower ( P < 0.05) for HP (162 ± 63 pmol/L) than CP (208 ± 80 pmol/L); ER (165 ± 65 pmol/L) than EA (204 ± 80 pmol/L); and MPC (160 ± 66 pmol/L) than SOY (208 ± 75 pmol/L). Independent of protein source and energy status, glucose‐6‐phosphatase, phosphoenolpyruvate carboxykinase, and hepatic nuclear factor‐1α total protein content were higher ( P < 0.05) for HP than CP. These data confirm the gluconeogenic advantage conferred by consuming a HP diet and suggest that a milk‐based diet may further enhance glycemic control by increasing insulin sensitivity. Grant Funding Source : Supported by Dairy Research Institute and USAMRMC
The effects of dietary protein and feeding during energy deficit (ED) on cellular regulators of muscle proteolysis are not well documented. This study examined intramuscular caspase‐3 and 26S proteasome responses to feeding during sustained ED in adults consuming varying levels of dietary protein. Using a randomized*block design, 32 men and 7 women were assigned to either standard (0.8 g·kg −1 ·d −1 ; n =13), moderate (1.6 g·kg −1 ·d −1 ; n =14), or high (2.4 g·kg −1 ·d −1 ; n =12) protein diets for 31 days. A 10 day weight maintenance period was followed by 21 days of ED, during which energy intake was restricted to 60% of total daily energy expenditure. Enzyme activities were assessed using fluorescence‐based assays and muscle samples obtained on days 10 and 31 following an overnight fast (FAST) and 120 min after consuming a mixed meal (480 kcals, 20 g protein; FED). The activity of the 26S proteasome's β1, β2, and β5 subunits were 28%, 14% and 22% lower ( P < 0.05), respectively, for FED relative to FAST regardless of energy status and dietary protein. Caspase‐3 activity remained steady in response to feeding and was not influenced by energy and protein manipulations. These data demonstrate that feeding attenuates ubiquitin‐mediated proteolysis, suggesting a novel cellular mechanism for preservation of muscle mass independent of habitual dietary protein intake and decrements in energy balance. Supported by USAMRMC, USDA ARS GFHNRC and EMU CHHS FRF
Musculoskeletal injuries (MSKIs) are common in military trainees and present a considerable threat to occupational fitness, deployability, and overall military readiness. Despite the negative effects of MSKIs on military readiness, comprehensive evaluations of the key known and possible risk factors for MSKIs are lacking. The U.S. Army Research Institute of Environmental Medicine (ARIEM) is initiating a large-scale research effort, the ARIEM Reduction in Musculoskeletal Injury (ARMI) Study, to better understand the interrelationships among a wide range of potential MSKI risk factors in U.S. Army trainees in order to identify those risk factors that most contribute to MSKI and may be best targeted for effective mitigation strategies.This prospective study aims to enroll approximately 4000 (2000 male and 2000 female) U.S. Army trainees undergoing Basic Combat Training (BCT). Comprehensive in-person assessments will be completed at both the beginning and end of BCT. Participants will be asked to complete surveys of personal background information, medical history, physical activity, sleep behaviors, and personality traits. Physical measurements will be performed to assess anthropometrics, tibial microarchitecture and whole body bone mineral density, muscle cross-sectional area, body composition, and muscle function. Blood sampling will be also be conducted to assess musculoskeletal, genetic, and nutritional biomarkers of risk. In addition, participants will complete weekly surveys during BCT that examine MSKI events, lost training time, and discrete risk factors for injury. Participants' medical records will be tracked for the 2 years following graduation from training to identify MSKI events and related information. Research hypotheses focus on the development of a multivariate prediction model for MSKI.Results from this study are expected to inform current understanding of known and potential risk factors for MSKIs that can be incorporated into solutions that optimize Soldier health and enhance military readiness.
