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

Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline

BACKGROUND

Numerous studies demonstrate associations between serum concentrations of 25-hydroxyvitamin D (25[OH]D) and a variety of common disorders, including musculoskeletal, metabolic, cardiovascular, malignant, autoimmune, and infectious diseases. Although a causal link between serum 25(OH)D concentrations and many disorders has not been clearly established, these associations have led to widespread supplementation with vitamin D and increased laboratory testing for 25(OH)D in the general population. The benefit-risk ratio of this increase in vitamin D use is not clear, and the optimal vitamin D intake and the role of testing for 25(OH)D for disease prevention remain uncertain.

OBJECTIVE

To develop clinical guidelines for the use of vitamin D (cholecalciferol [vitamin D3] or ergocalciferol [vitamin D2]) to lower the risk of disease in individuals without established indications for vitamin D treatment or 25(OH)D testing.

METHODS

A multidisciplinary panel of clinical experts, along with experts in guideline methodology and systematic literature review, identified and prioritized 14 clinically relevant questions related to the use of vitamin D and 25(OH)D testing to lower the risk of disease. The panel prioritized randomized placebo-controlled trials in general populations (without an established indication for vitamin D treatment or 25[OH]D testing), evaluating the effects of empiric vitamin D administration throughout the lifespan, as well as in select conditions (pregnancy and prediabetes). The panel defined "empiric supplementation" as vitamin D intake that (a) exceeds the Dietary Reference Intakes (DRI) and (b) is implemented without testing for 25(OH)D. Systematic reviews queried electronic databases for publications related to these 14 clinical questions. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology was used to assess the certainty of evidence and guide recommendations. The approach incorporated perspectives from a patient representative and considered patient values, costs and resources required, acceptability and feasibility, and impact on health equity of the proposed recommendations. The process to develop this clinical guideline did not use a risk assessment framework and was not designed to replace current DRI for vitamin D.

RESULTS

The panel suggests empiric vitamin D supplementation for children and adolescents aged 1 to 18 years to prevent nutritional rickets and because of its potential to lower the risk of respiratory tract infections; for those aged 75 years and older because of its potential to lower the risk of mortality; for those who are pregnant because of its potential to lower the risk of preeclampsia, intra-uterine mortality, preterm birth, small-for-gestational-age birth, and neonatal mortality; and for those with high-risk prediabetes because of its potential to reduce progression to diabetes. Because the vitamin D doses in the included clinical trials varied considerably and many trial participants were allowed to continue their own vitamin D-containing supplements, the optimal doses for empiric vitamin D supplementation remain unclear for the populations considered. For nonpregnant people older than 50 years for whom vitamin D is indicated, the panel suggests supplementation via daily administration of vitamin D, rather than intermittent use of high doses. The panel suggests against empiric vitamin D supplementation above the current DRI to lower the risk of disease in healthy adults younger than 75 years. No clinical trial evidence was found to support routine screening for 25(OH)D in the general population, nor in those with obesity or dark complexion, and there was no clear evidence defining the optimal target level of 25(OH)D required for disease prevention in the populations considered; thus, the panel suggests against routine 25(OH)D testing in all populations considered. The panel judged that, in most situations, empiric vitamin D supplementation is inexpensive, feasible, acceptable to both healthy individuals and health care professionals, and has no negative effect on health equity.

CONCLUSION

The panel suggests empiric vitamin D for those aged 1 to 18 years and adults over 75 years of age, those who are pregnant, and those with high-risk prediabetes. Due to the scarcity of natural food sources rich in vitamin D, empiric supplementation can be achieved through a combination of fortified foods and supplements that contain vitamin D. Based on the absence of supportive clinical trial evidence, the panel suggests against routine 25(OH)D testing in the absence of established indications. These recommendations are not meant to replace the current DRIs for vitamin D, nor do they apply to people with established indications for vitamin D treatment or 25(OH)D testing. Further research is needed to determine optimal 25(OH)D levels for specific health benefits.

A Systematic Review Supporting the Endocrine Society Clinical Practice Guidelines on Vitamin D

CONTEXT

Low vitamin D status is common and is associated with various common medical conditions.

OBJECTIVE

To support the development of the Endocrine Society's Clinical Practice Guideline on Vitamin D for the Prevention of Disease.

METHODS

We searched multiple databases for studies that addressed 14 clinical questions prioritized by the guideline panel. Of the 14 questions, 10 clinical questions assessed the effect of vitamin D vs no vitamin D in the general population throughout the lifespan, during pregnancy, and in adults with prediabetes; 1 question assessed dosing; and 3 questions addressed screening with serum 25-hydroxyvitamin D (25[OH]D). The Grading of Recommendations Assessment, Development and Evaluation approach was used to assess certainty of evidence.

RESULTS

Electronic searches yielded 37 007 citations, from which we included 151 studies. In children and adolescents, low-certainty evidence suggested reduction in respiratory tract infections with empiric vitamin D. There was no significant effect on select outcomes in healthy adults aged 19 to 74 years with variable certainty of evidence. There was a very small reduction in mortality among adults older than 75 years with high certainty of evidence. In pregnant women, low-certainty evidence suggested possible benefit on various maternal, fetal, and neonatal outcomes. In adults with prediabetes, moderate certainty of evidence suggested reduction in the rate of progression to diabetes. Administration of high-dose intermittent vitamin D may increase falls, compared to lower-dose daily dosing. We did not identify trials on the benefits and harms of screening with serum 25(OH)D.

CONCLUSION

The evidence summarized in this systematic review addresses the benefits and harms of vitamin D for the prevention of disease. The guideline panel considered additional information about individuals' and providers' values and preferences and other important decisional and contextual factors to develop clinical recommendations.

Green strength: The role of micronutrients in plant-based diets for athletic performance enhancement

This review examines the correlation between plant-based diets and athletic performance, with a specific emphasis on the vital aspect of optimizing micronutrients for athletes. In light of the increasing prevalence of plant-based nutrition among athletes due to its perceived advantages in terms of health, ethics, and the environment, this study investigates the ability of these diets to satisfy the demanding nutritional requirements essential for achieving optimal performance and facilitating recovery. The article emphasizes the significance of essential micronutrients such as iron, vitamin B12, calcium, vitamin D, zinc, and omega-3 fatty acids and also addressing the challenges with their absorption and bioavailability from plant sources. The review consolidates existing scientific knowledge to propose strategies for improving micronutrient consumption, comparing the effects of supplements against whole foods, and highlighting the significance of enhancing bioavailability. The proposal supports the implementation of personalized meal planning, with the assistance of sports nutritionists or dietitians, and is substantiated by case studies showcasing the success of plant-based athletes. Future research directions examine the long-term effects of plant-based diets on micronutrient status and athletic performance, as well as developing nutritional trends and technology. The review concludes that plant-based diets can meet athletes' nutritional demands and improve peak performance while aligning with personal and ethical values with strategic planning and professional guidance. This study intends to help athletes, coaches, and nutritionists understand plant-based nutrition for enhanced athletic performance.

Hormonal contraceptive use is associated with altered bone structural and metabolic responses to military training in women: An observational cohort study

Military training increases tibial density and size. Female sex hormones may influence the adaption of bone to loading, but it is unknown if women using different hormonal contraceptives adapt similarly to military training. One hundred and sixteen women (57 women not using hormonal contraceptives [non-users], 38 combined oral contraceptive pill [COCP] users, 21 depot medroxyprogesterone acetate [DMPA] users) completed this study. Tibial volumetric bone mineral density (vBMD) and geometry were measured by peripheral quantitative computed tomography (4 %, 14 %, 38 %, and 66 % sites) at the start (week 1) and end (week 14) of British Army basic training. Circulating markers of bone and calcium metabolism were measured at weeks 1, 2, 4, 6, 10, and 14. Training increased trabecular vBMD at the 4 % site, periosteal perimeter at the 14 % and 66 % sites, and total area, cortical area, cortical thickness, and bone strength at all sites (0.1 to 1.6 %, p ≤ 0.009), with no differences between hormonal contraceptive groups (p ≥ 0.127). Trabecular vBMD increased at the 14 % site in non-users (0.8 %, p = 0.005), but not in COCP or DMPA users (p ≥ 0.205). Periosteal perimeter increased at the 38 % site in COCP (0.4 %, p < 0.001) and DMPA (0.5 %, p < 0.001) users, but not in non-users (p = 0.058). Training had no effect on periosteal perimeter at the 4 % site or cortical vBMD or endosteal perimeter at any site (p ≥ 0.168). βCTX decreased and PINP increased during training with no difference between hormonal contraceptive groups. Training increased iPTH in non-users, but not COCP or DMPA users. Hormonal contraceptives may exert site-specific effects on the mechanobiology of bone, with higher endogenous oestradiol promoting trabecularisation and inhibiting periosteal expansion in non-users compared with hormonal contraceptive users.

Load carriage exercise increases calcium absorption and retention in healthy young women

Aerobic exercise reduces circulating ionized Ca (iCa) and increases parathyroid hormone (PTH), but the cause and consequences on Ca handling are unknown. The objective of this study was to determine the effects of strenuous exercise on Ca kinetics using dual stable Ca isotopes. Twenty-one healthy women (26.4 ± 6.7 yr) completed a randomized, crossover study entailing two 6-d iterations consisting of either 60 min of treadmill walking at 65% VO2max wearing a vest weighing 30% body weight on study days 1, 3, and 5 (exercise [EX]), or a rest iteration (rest [REST]). On day 1, participants received intravenous 42Ca and oral 44Ca. Isotope ratios were determined by thermal ionization mass spectrometry. Kinetic modeling determined fractional Ca absorption (FCA), Ca deposition (Vo+), resorption (Vo-) from bone, and balance (Vbal). Circulating PTH and iCa were measured before, during, and after each exercise/rest session. Data were analyzed by paired t-test or linear mixed models using SPSS. iCa decreased and PTH increased (P < .001) during each EX session and were unchanged during REST. On day 1, urinary Ca was lower in the EX pool (25 ± 11 mg) compared to REST (38 ± 16 mg, P = .001), but did not differ over the full 24-h collection (P > .05). FCA was greater during EX (26.6 ± 8.1%) compared to REST (23.9 ± 8.3%, P < .05). Vbal was less negative during EX (-61.3 ± 111 mg) vs REST (-108 ± 23.5 mg, P < .05), but VO+ (574 ± 241 vs 583 ± 260 mg) and VO- (-636 ± 243 vs -692 ± 252 mg) were not different (P > .05). The rapid reduction in circulating iCa may be due to a change in the miscible Ca pool, resulting in increased PTH and changes in intestinal absorption and renal Ca handling that support a more positive Ca balance.

Stress fractures of the foot - current evidence on management

Stress fractures are a consequence of repeated submaximal loads with inadequate time for recovery and biologic repair or remodelling. The foot and ankle complex (FAC) represents a common site for development of stress fractures. Whilst the overall incidence of stress fractures is low, they are prevalent in athletes and military personnel causing significant time away from sports or work. Within these populations, certain stress fractures directly correlate to specific activities. Factors that commonly influence these fractures include an acute increase in new repetitive physical activity combined with muscle fatigue, training errors or improper athletic techniques, which challenge the regenerative and remodelling capacity of bone. Depending on the site that is subject to repetitive loading, various biomechanical factors can result in abnormal concentration of forces to specific areas of the FAC resulting in stress fracture. Decreased bone marrow density (BMD) is a major biologic cause for developing stress fractures. The female athlete triad comprising eating disorder, amenorrhea and osteoporosis in competitive athletes also predisposes to stress fractures. Vitamin D deficiency is also postulated to be the cause of these fractures and may contribute to poor healing. Clinical presentation is usually with vague pain of insidious onset which worsens with activity and improves with rest. Diffuse tenderness over the affected bone is common with only a minority having any visible swelling. Plain radiographs are the first line of investigation but rarely reveal an obvious fracture. MRI scans aid in diagnosis and CT scans help in treatment and characterisation of the fracture and monitor healing. Management relates to the site of injury, which stratifies them into high or low-risk. Stress fractures of the calcaneus, cuboid and cuneiforms are classed as low-risk fractures as they usually heal with simple activity modification or short duration of non-weight bearing. Stress fractures of the navicular, talus and hallucal sesamoids are classed as high-risk fractures due to higher rates of non-union and prolonged recovery time. Metatarsal fractures can be considered high or low-risk depending on location. These warrant aggressive management, often requiring surgical intervention. Adjuncts such as vitamin D supplements, external shockwave therapy, low-intensity pulsed ultrasound therapy have been used with varying success but there remains little supportive evidence of superiority in the available literature.

Correlation between body composition and white matter hyperintensity in patients with acute ischemic stroke

White matter hyperintensity (WMH) burden is associated with a higher risk of ischemic stroke. The relationship between WMH and obesity is somewhat controversial which might be interfered by different body composition such as skeletal muscle, fat and bone density. However, few researchers have evaluated the relationship between WMH burden and disaggregated body constituents in acute ischemic stroke (AIS) patients systematically. A total of 352 AIS patients were enrolled in this study. The subcutaneous adipose tissue, erector spinae muscle area and bone density were evaluated on the computed tomography scanning. The burden of WMH was evaluated using the Fazekas scale based on the fluid-attenuated inversion recovery sequence. The severity of overall WMH was defined as none-mild WMH (total Fazekas score 0-2) or moderate-severe WMH (total Fazekas score 3-6). Based on the severity of periventricular WMH (P-WMH) and deep WMH, patients were categorized into either a none-mild (Fazekas score 0-1) group or a moderate-severe (Fazekas score 2-3) group. We found that patients with moderate-severe WMH showed lower bone density and smaller erector spinae muscle area and subcutaneous adipose tissue than none-mild. The logistic regression analysis showed that the bone density was independently associated with moderate-severe overall WMH (odds radio = 0.98, 95% confidence interval, 0.972-0.992, P < .001) and similar results were found in the analyses according to P-WMH (odds radio = 0.98, 95% confidence interval, 0.972-0.992, P < .001). These findings suggest that among the AIS body composition, the bone density is independently associated with the severity of overall WMH and P-WMH.

The association of osteoprotegerin and RANKL with osteoporosis: a systematic review with meta-analysis

OBJECTIVES

The OPG/RANKL signal pathway was important regulation mechanism of bone remodeling cycle, but the effect of osteoprotegerin (OPG) and RANKL in osteoporosis was uncertain. We did a systematic review with meta-analysis to assess the association between serum OPG/RANKL and osteoporosis.

METHODS

The systematic search, data extraction, critical appraisal, and meta-analysis were performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Randomized controlled studies were searched in PubMed, OvidMedline, Embase (1946 to present). Standard mean difference (SMD), and associated credible interval (CI) were calculated using RevMan statistical software to assess the continuous data. Heterogeneity in studies was measured by I2 values. Subgroup analysis was performed based on different bone turnover.

RESULTS

A total of 5 randomized controlled studies met the inclusion criteria. Both OPG and RANKL had no significant differences between the osteoporosis and control group, and the statistical heterogeneity was high in meta-analysis. However, RANKL had significant differences between the osteoporosis group with low bone turnover and control group (SMD =  - 1.17; 95% CI - 1.77 to 0.57; P value < 0.01) in subanalysis. Furthermore, the OPG/RANKL ratio was significant lower in the osteoporosis group than in the control group (SMD =  - 0.29; 95% CI - 0.57 to - 0.02; P value < 0.05), and the statistical heterogeneity was very low (Chi2 = 0.20, P = 0.66, I2 = 0%).

CONCLUSIONS

Our meta-analysis study supported OPG and RANKL were important modulatory factors of bone formation and resorption in bone turnover, respectively. Although the serum level of both OPG and RANKL were not associated with osteoporosis, but the OPG/RANKL ratio was associated with osteoporosis. In future, standardizing the test method and unit was good to clinical application.

Utility of HR-pQCT in detecting training-induced changes in healthy adult bone morphology and microstructure

Healthy bone adjusts its traits in an exceptionally coordinated, compensatory process. Recent advancements in skeletal imaging via High-Resolution Peripheral Quantitative Computed Tomography (HR-pQCT) allows for the in vivo 3-dimensional and longitudinal quantification of bone density, microarchitecture, geometry, and parameters of mechanical strength in response to varying strain stimuli including those resulting from exercise or military training. Further, the voxel size of 61 microns has the potential to capture subtle changes in human bone in as little as 8 weeks. Given the typical time course of bone remodeling, short-term detection of skeletal changes in bone microstructure and morphology is indicative of adaptive bone formation, the deposition of new bone formation, uncoupled from prior resorption, that can occur at mechanistically advantageous regions. This review aims to synthesize existing training-induced HR-pQCT data in three distinct populations of healthy adults excluding disease states, pharmacological intervention and nutritional supplementation. Those included are: 1) military basic or officer training 2) general population and 3) non-osteoporotic aging. This review aims to further identify similarities and contrasts with prior modalities and cumulatively interpret results within the scope of bone functional adaptation.

Vitamin D Metabolites Are Associated With Musculoskeletal Injury in Young Adults: A Prospective Cohort Study

The relationship between vitamin D metabolites and lower body (pelvis and lower limb) overuse injury is unclear. In a prospective cohort study, we investigated the association between vitamin D metabolites and incidence of lower body overuse musculoskeletal and bone stress injury in young adults undergoing initial military training during all seasons. In 1637 men and 530 women (aged 22.6 ± 7.5 years; body mass index [BMI], 24.0 ± 2.6 kg/m- 2 ; 94.3% white ethnicity), we measured serum 25-hydroxyvitamin D (25(OH)D) and 24,25-dihydroxyvitamin D (24,25(OH)2 D) by high-performance liquid chromatography tandem mass spectrometry, and 1,25-dihydroxyvitamin D (1,25(OH)2 D) by immunoassay during week 1 of training. We examined whether the relationship between 25(OH)D and 1,25(OH)2 D:24,25(OH)2 D ratio was associated with overuse injury. During 12 weeks of training, 21.0% sustained ≥1 overuse musculoskeletal injury, and 5.6% sustained ≥1 bone stress injury. After controlling for sex, BMI, 2.4 km run time, smoking, bone injury history, and Army training course (Officer, standard, or Infantry), lower body overuse musculoskeletal injury incidence was higher for participants within the second lowest versus highest quartile of 24,25(OH)2 D (odds ratio [OR] = 1.62; 95% confidence interval [CI] 1.13-2.32; p = 0.009) and lowest versus highest cluster of 25(OH)D and 1,25(OH)2 D:24,25(OH)2 D (OR = 6.30; 95% CI 1.89-21.2; p = 0.003). Lower body bone stress injury incidence was higher for participants within the lowest versus highest quartile of 24,25(OH)2 D (OR = 4.02; 95% CI 1.82-8.87; p < 0.001) and lowest versus highest cluster of 25(OH)D and 1,25(OH)2 D:24,25(OH)2 D (OR = 22.08; 95% CI 3.26-149.4; p = 0.001), after controlling for the same covariates. Greater conversion of 25(OH)D to 24,25(OH)2 D, relative to 1,25(OH)2 D (ie, low 1,25(OH)2 D:24,25(OH)2 D), and higher serum 24,25(OH)2 D were associated with a lower incidence of lower body overuse musculoskeletal and bone stress injury. Serum 24,25(OH)2 D may have a role in preventing overuse injury in young adults undertaking arduous physical training. © 2023 Crown copyright and The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). This article is published with the permission of the Controller of HMSO and the King's Printer for Scotland.

Distal Tibial Bone Properties and Bone Stress Injury Risk in Young Men Undergoing Arduous Physical Training

Trabecular microarchitecture contributes to bone strength, but its role in bone stress injury (BSI) risk in young healthy adults is unclear. Tibial volumetric BMD (vBMD), geometry, and microarchitecture, whole-body areal BMD, lean and fat mass, biochemical markers of bone metabolism, aerobic fitness, and muscle strength and power were measured in 201 British Army male infantry recruits (age 20.7 [4.3] years, BMI 24.0 ± 2.7 kg·m2) in week one of basic training. Tibial scans were performed at the ultra-distal site, 22.5 mm from the distal endplate of the non-dominant leg using High Resolution Peripheral Quantitative Computed Tomography (XtremeCT, Scanco Medical AG, Switzerland). Binary logistic regression analysis was performed to identify associations with lower body BSI confirmed by MRI. 20 recruits (10.0%) were diagnosed with a lower body BSI. Pre-injured participants had lower cortical area, stiffness and estimated failure load (p = 0.029, 0.012 and 0.011 respectively) but tibial vBMD, geometry, and microarchitecture were not associated with BSI incidence when controlling for age, total body mass, lean body mass, height, total 25(OH)D, 2.4-km run time, peak power output and maximum dynamic lift strength. Infantry Regiment (OR 9.3 [95%CI, 2.6, 33.4]) Parachute versus Line Infantry, (p ≤ 0.001) and 2.4-km best effort run time (1.06 [95%CI, 1.02, 1.10], p < 0.033) were significant predictors. Intrinsic risk factors, including ultradistal tibial density, geometry, and microarchitecture, were not associated with lower body BSI during arduous infantry training. The ninefold increased risk of BSI in the Parachute Regiment compared with Line Infantry suggests that injury propensity is primarily a function of training load and risk factors are population-specific.

Fortification of Staple Foods for Household Use with Vitamin D: An Overview of Systematic Reviews

Vitamin D deficiency is a global public health concern with significant implications for bone health and chronic disease prevention. Our aim was to summarize the evidence from Cochrane and other systematic reviews evaluating the benefits or harms of vitamin D fortification of staple foods for household use. In April 2023, we systematically searched Ovid MEDLINE, Embase, Epistemonikos and the Cochrane Database of Systematic Reviews for systematic reviews investigating the effects of vitamin D fortification of food in general populations of any age. We used Cochrane methodology and assessed the methodological quality of included studies using AMSTAR (A MeaSurement Tool to Assess Systematic Reviews). We assessed the degree of overlap among reviews. All outcomes included in systematic reviews were assessed. The protocol is registered in PROSPERO (registration number: CRD42023420991). We included 27 systematic reviews out of 5028 records for analysis. Overall, 11 out of 12 systematic reviews calculating pooled estimates reported a significant increase in serum 25(OH)D concentrations. The mean change in serum 25(OH)D concentrations per additional 100 units of vitamin D ranged from 0.7 to 10.8 nmol/L. Fortification of food with vitamin D showed a reduction in the prevalence of vitamin D deficiency based on high-certainty evidence. Parathormone (PTH) levels were described to decrease, bone mineral density to increase, while the effects on other bone turnover markers were inconsistent. Fortification did not significantly impact most anthropometric parameters, but it seemed to positively influence lipid profiles. In summary, fortification of food with vitamin D results in a reduction of vitamin D deficiency and might increase serum 25(OH)D concentrations, to varying extents depending on the fortified vehicle and population characteristics. Additionally, fortification may have a positive impact on bone turnover and lipid metabolism but may only have a limited effect on anthropometric parameters.

The bone-protective benefits of amino-conjugated calcium in an ovariectomized (OVX) rat model

Low bone density, fragility, and microarchitectural disintegration are the symptoms of osteoporosis. An imbalance between bone growth and resorption can lead to osteoporosis. This study evaluated the effects of amino-calcium (AC) on bone protection in ovariectomized control group (NC) rats. Amino-calcium (AC) was characterized using Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDS), and nuclear magnetic resonance spectroscopy analyses (NMR). After determining the biocompatibility of amino-calcium (AC) with MC3T3-E1 cells, alkaline phosphatase staining revealed significant changes on day 7. Three of the four groups underwent ovariectomy, whereas one group received a placebo. On micro-computed tomography, in vivo, data showed increased bone volume fraction in the femoral head and shaft areas in the amino-calcium (AC) group. Hematoxylin and eosin staining showed a bone mass and architectural protection in the amino-calcium (AC) group compared with the calcium carbonate and OVX control group. RNA sequencing analysis revealed high expression of osteogenesis-related genes in MC3T3-E1 cells. RNA sequencing revealed a significant fold change in the expression of integrin-binding sialoprotein (IBSP), bone gamma-carboxyglutamate proteins 1 and 2(BGLAP1 and BGLAP2), and periostin (POSTN). The study concluded that supplementing the OVX rats with calcium enhanced bone protection.

Pathophysiological mechanism of acute bone loss after fracture

BACKGROUND

Acute bone loss after fracture is associated with various effects on the complete recovery process and a risk of secondary fractures among patients. Studies have reported similarities in pathophysiological mechanisms involved in acute bone loss after fractures and osteoporosis. However, given the silence nature of bone loss and bone metabolism complexities, the actual underlying pathophysiological mechanisms have yet to be fully elucidated.

AIM OF REVIEW

To elaborate the latest findings in basic research with a focus on acute bone loss after fracture. To briefly highlight potential therapeutic targets and current representative drugs. To arouse researchers' attention and discussion on acute bone loss after fracture.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Bone loss after fracture is associated with immobilization, mechanical unloading, blood supply damage, sympathetic nerve regulation, and crosstalk between musculoskeletals among other factors. Current treatment strategies rely on regulation of osteoblasts and osteoclasts, therefore, there is a need to elucidate on the underlying mechanisms of acute bone loss after fractures to inform the development of efficacious and safe drugs. In addition, attention should be paid towards ensuring long-term skeletal health.

The effect of calcium supplementation on calcium and bone metabolism during load carriage in women: protocol for a randomised controlled crossover trial

BACKGROUND

Military field exercises are characterised by high volumes of exercise and prolonged periods of load carriage. Exercise can decrease circulating serum calcium and increase parathyroid hormone and bone resorption. These disturbances to calcium and bone metabolism can be attenuated with calcium supplementation immediately before exercise. This randomised crossover trial will investigate the effect of calcium supplementation on calcium and bone metabolism, and bone mineral balance, during load carriage exercise in women.

METHODS

Thirty women (eumenorrheic or using the combined oral contraceptive pill, intrauterine system, or intrauterine device) will complete two experimental testing sessions either with, or without, a calcium supplement (1000 mg). Each experimental testing session will involve one 120 min session of load carriage exercise carrying 20 kg. Venous blood samples will be taken and analysed for biochemical markers of bone resorption and formation, calcium metabolism, and endocrine function. Urine will be collected pre- and post-load carriage to measure calcium isotopes for the calculation of bone calcium balance.

DISCUSSION

The results from this study will help identify whether supplementing women with calcium during load carriage is protective of bone and calcium homeostasis.

TRIAL REGISTRATION

NCT04823156 (clinicaltrials.gov).

Current risks factors and emerging biomarkers for bone stress injuries in military personnel

INTRODUCTION

Bone stress injuries (BSIs) have plagued the military for over 150 years; they afflict around 5 to 10% of military recruits, more so in women, and continue to place a medical and financial burden on defence. While the tibia generally adapts to the rigours of basic military training, the putative mechanisms for bone maladaptation are still unclear.

METHODS

This paper provides a review of the published literature on current risk factors and emerging biomarkers for BSIs in military personnel; the potential for biochemical markers of bone metabolism to monitor the response to military training; and, the association of novel biochemical 'exerkines' with bone health.

RESULTS

The primary risk factor for BSI in military (and athletic) populations is too much training, too soon. Appropriate physical preparation before training will likely be most protective, but routine biomarkers will not yet identify those at risk. Nutritional interventions will support a bone anabolic response to training, but exposure to stress, sleep loss, and medication is likely harmful to bone. Monitoring physiology using wearables-ovulation, sleep and stress-offer potential to inform prevention strategies.

CONCLUSIONS

The risk factors for BSIs are well described, but their aetiology is very complex particularly in the multi-stressor military environment. Our understanding of the skeletal responses to military training is improving as technology advances, and potential biomarkers are constantly emerging, but sophisticated and integrated approaches to prevention of BSI are warranted.

Correlation between Baseline 25(OH) Vitamin D Levels and Both Humoral Immunity and Breakthrough Infection Post-COVID-19 Vaccination

Objective: Vaccines against COVID-19 induce specific antibodies whose titer is perceived as a reliable correlate of protection. Vitamin D confers complex regulatory effects on the innate and adaptive immunity. In this study, we explored a plausible impact of baseline vitamin D content on achieved immunity following COVID-19 vaccination. Methods: A retrospective observational study comprising 73,254 naïve subjects insured by the Leumit Health Service HMO, who were vaccinated between 1 February 2020 and 30 January 2022, with one available vitamin D level prior to vaccination, was performed. The association between 25(OH) vitamin D levels, SARS-CoV-2 antibody titer, and post-vaccination PCR results were evaluated. Results: Of the study population, 5026 (6.9%) tested positive for COVID-19. The proportion of low 25(OH)D levels (<30 ng/mL) was significantly higher in the PCR-positive group (81.5% vs. 79%, p < 0.001). Multivariate analysis showed a higher incidence of breakthrough infection among non-smokers [1.37 (95% CI 1.22−1.54, p < 0.001)] and lower incidences among subjects with sufficient 25(OH)D levels (>30 ng/mL) [0.87 (95% CI 0.79−0.95, p—0.004)], hyperlipidemia [0.84 (95% CI 0.76−0.93, p < 0.001], depression [OR-0.87 (95% CI: 0.79−0.96, p < 0.005], socio-economic status >10 [0.67 (95% CI 0.61−0.73, p < 0.001)], and age >44 years. SARS-CoV-2 antibody titers were available in 3659 vaccinated individuals. The prevalence of antibody titers (<50 AU) among PCR-positive subjects was 42% compared to 28% among PCR-negative subjects (p < 0.001). Baseline 25(OH)D levels showed an inverse relation to total antibody titers. However, no association was found with an antibody titer <50 AU/mL fraction. Conclusion Baseline 25(OH)D levels correlated with the vaccination-associated protective COVID-19 immunity. Antibody titers <50 AU/mL were significantly linked to breakthrough infection but did not correlate with 25(OH)D levels.

Divergent effects of sex and calcium/vitamin D supplementation on serum magnesium and markers of bone structure and function during initial military training

Maintaining Mg status may be important for military recruits, a population that experiences high rates of stress fracture during initial military training (IMT). The objectives of this secondary analysis were to (1) compare dietary Mg intake and serum Mg in female and male recruits pre- and post-IMT, (2) determine whether serum Mg was related to parameters of bone health pre-IMT, and (3) whether Ca and vitamin D supplementation (Ca/vitamin D) during IMT modified serum Mg. Females (n 62) and males (n 51) consumed 2000 mg of Ca and 25 μg of vitamin D/d or placebo during IMT (12 weeks). Dietary Mg intakes were estimated using FFQ, serum Mg was assessed and peripheral quantitative computed tomography was performed on the tibia. Dietary Mg intakes for females and males pre-IMT were below the estimated average requirement and did not change with training. Serum Mg increased during IMT in females (0·06 ± 0·08 mmol/l) compared with males (-0·02 ± 0·10 mmol/l; P < 0·001) and in those consuming Ca/vitamin D (0·05 ± 0·09 mmol/l) compared with placebo (0·001 ± 0·11 mmol/l; P = 0·015). In females, serum Mg was associated with total bone mineral content (BMC, β = 0·367, P = 0·004) and robustness (β = 0·393, P = 0·006) at the distal 4 % site, stress-strain index of the polaris axis (β = 0·334, P = 0·009) and robustness (β = 0·420, P = 0·004) at the 14 % diaphyseal site, and BMC (β = 0·309, P = 0·009) and stress-strain index of the polaris axis (β = 0·314, P = 0·006) at the 66 % diaphyseal site pre-IMT. No significant relationships between serum Mg and bone measures were observed in males. Findings suggest that serum Mg may be modulated by Ca/vitamin D intake and may impact tibial bone health during training in female military recruits.

Proportion of Navy Recruits Diagnosed With Symptomatic Stress Fractures During Training and Monetary Impact of These Injuries

BACKGROUND

Lower extremity stress fractures result in lost time from work and sport and incur costs in the military when they occur in service members. Hypovitaminosis D has been identified as key risk factor in these injuries. An estimated 33% to 90% of collegiate and professional athletes have deficient vitamin D levels. Other branches of the United States military have evaluated the risk factors for stress fractures during basic training, including vitamin D deficiency. To the best of our knowledge, a study evaluating the correlation between these injuries and vitamin D deficiency in US Navy recruits and a cost analysis of these injuries has not been performed. Cutbacks in military medical staffing mean more active-duty personnel are being deferred for care to civilian providers. Consequently, data that previously were only pertinent to military medical providers have now expanded to the nonmilitary medical community.

QUESTIONS/PURPOSES

We therefore asked: (1) What proportion of US Navy recruits experience symptomatic lower extremity stress fractures, and what proportion of those recruits had hypovitaminosis vitamin D on laboratory testing? (2) What are the rehabilitation costs involved in the treatment of lower extremity stress fractures, including the associated costs of lost training time? (3) Is there a cost difference in the treatment of stress fractures between recruits with lower extremity stress fractures who have vitamin D deficiency and those without vitamin D deficiency?

METHODS

We retrospectively evaluated the electronic medical record at Naval Recruit Training Command in Great Lakes, IL, USA, of all active-duty males and females trained from 2009 until 2015. We used ICD-9 and ICD-10 diagnosis codes to identify those diagnosed with symptomatic lower extremity stress fractures. Data collected included geographic region of birth, preexisting vitamin D deficiency, vitamin D level at the time of diagnosis, medical history, BMI, age, sex, self-reported race or ethnicity, hospitalization days, days lost from training, and the number of physical therapy, primary care, and specialty visits. To ascertain the proportion of recruits who developed symptomatic stress fractures, we divided the number of recruits who were diagnosed with a stress fracture by the total number who trained over that span of time, which was 204,774 individuals. During the span of this study, 45% (494 of 1098) of recruits diagnosed with a symptomatic stress fracture were female and 55% (604 of 1098) were male, with a mean ± SD age of 24 ± 4 years. We defined hypovitaminosis D as a vitamin D level lower than 40 ng/mL. Levels less than 40 ng/mL were defined as low normal and levels less than 30 ng/mL as deficient. Vitamin D levels were obtained at the discretion of the individual treating provider without standardization of protocol. Cost was defined as physical therapy visits, primary care visits, orthopaedic visits, diagnostic imaging costs, laboratory costs, hospitalizations, if applicable, and days lost from training. Diagnostic studies and laboratory tests were incorporated as indirect costs into initial and follow-up physical therapy visits. Evaluation and management code fee schedules for initial visits and follow-up visits were used as direct costs. We obtained these data from the Centers for Medicare & Medicaid Services website. Per capita cost was calculated by taking the total cost and dividing it by the study population. Days lost from training is based on a standardized government military salary of recruits to include room and board.

RESULTS

We found that 0.5% (1098 of 204,774) of recruits developed a symptomatic lower extremity stress fracture. Of the recruits who had vitamin D levels drawn at the time of stress fracture, 95% (416 of 437 [95% confidence interval (CI) 94% to 98%]; p > 0.99) had hypovitaminosis D (≤ 40 ng/mL) and 82% (360 of 437 [95% CI 79% to 86%]; p > 0.99) had deficient levels (≤ 30 ng/mL) on laboratory testing, when evaluated. The total treatment cost was USD 9506 per recruit. Days lost in training was a median of 56 days (4 to 108) for a per capita cost of USD 5447 per recruit. Recruits with deficient vitamin D levels (levels ≤ 30 ng/mL) incurred more physical therapy treatment costs than did those with low-normal vitamin D levels (levels 31 to 40 ng/mL) (mean difference USD 965 [95% CI 2 to 1928]; p = 0.049).

CONCLUSION

The cost of lost training and rehabilitation associated with symptomatic lower extremity stress fractures represents a major financial burden. Screening for and treatment of vitamin D deficiencies before recruit training could offer a cost-effective solution to decreasing the stress fracture risk. Recognition and treatment of these deficiencies has a role beyond the military, as hypovitaminosis and stress fractures are common in collegiate or professional athletes.

LEVEL OF EVIDENCE

Level III, prognostic study.

Iron deficiency and high-intensity running interval training do not impact femoral or tibial bone in young female rats

In the USA, as many as 20 % of recruits sustain stress fractures during basic training. In addition, approximately one-third of female recruits develop Fe deficiency upon completion of training. Fe is a cofactor in bone collagen formation and vitamin D activation, thus we hypothesised Fe deficiency may be contributing to altered bone microarchitecture and mechanics during 12-weeks of increased mechanical loading. Three-week old female Sprague Dawley rats were assigned to one of four groups: Fe-adequate sedentary, Fe-deficient sedentary, Fe-adequate exercise and Fe-deficient exercise. Exercise consisted of high-intensity treadmill running (54 min 3×/week). After 12-weeks, serum bone turnover markers, femoral geometry and microarchitecture, mechanical properties and fracture toughness and tibiae mineral composition and morphometry were measured. Fe deficiency increased the bone resorption markers C-terminal telopeptide type I collagen and tartate-resistant acid phosphatase 5b (TRAcP 5b). In exercised rats, Fe deficiency further increased bone TRAcP 5b, while in Fe-adequate rats, exercise increased the bone formation marker procollagen type I N-terminal propeptide. In the femur, exercise increased cortical thickness and maximum load. In the tibia, Fe deficiency increased the rate of bone formation, mineral apposition and Zn content. These data show that the femur and tibia structure and mechanical properties are not negatively impacted by Fe deficiency despite a decrease in tibiae Fe content and increase in serum bone resorption markers during 12-weeks of high-intensity running in young growing female rats.

Sex differences in tibial adaptations to arduous training: An observational cohort study

Military training increases tibial density and size, but it is unknown if men and women adapt similarly to the same arduous training. Seventy-seven men and 57 women not using hormonal contraceptives completed this study. Tibial volumetric bone mineral density (vBMD) and geometry were measured by peripheral quantitative computed tomography (4%, 14%, 38%, and 66% sites) at the start (week 1) and end (week 14) of British Army basic training. Training increased trabecular vBMD (4% site in men; 4% and 14% sites in women), cortical vBMD (38% site), total area (14% and 38% sites), trabecular area (14% site), cortical area and thickness (14%, 38%, and 66% sites), periosteal perimeter (14%, 38%, and 66% sites), and all indices of estimated strength (14%, 38%, and 66% sites); and, decreased endosteal perimeter (66% site) in men and women (all p ≤ 0.045). The increase in trabecular vBMD (4% and 14% sites) was greater in women and the increases in cortical area and strength (38% site) were greater in men (sex × time interactions, all p ≤ 0.047). P1NP increased and βCTX and sclerostin decreased during training in men and women, consistent with adaptive bone formation. PTH decreased in men but increased in women. Arduous weight-bearing activity increased the density and size of the tibia after 14 weeks. Women experienced similar tibial adaptations as men, however, a greater increase in trabecular vBMD in women compared with men could be due to higher loading at this skeletal site in women, whereas the small increase in cortical area could be due to inhibitory effects of oestradiol.

Longitudinal Tibia Stress Fracture Risk During High-Volume Training: a Multi-Scale Modeling Pipeline Incorporating Bone Remodeling

Tibia stress fractures are prevalent during high-intensity training, yet a mechanistic model linking longitudinal training intensity, bone health, and long-term injury risk has yet to be demonstrated. The objective of this study was to develop and validate a multi-scale model of gross and tissue level loading on the tibia including bone remodeling on a timescale of week. Peak tensile tibial strain (3517 µstrain) during 4 m/s running was below injury thresholds, and the peak anteromedial tibial strain (1248 µstrain) was 0.17 standard deviations away from the mean of reported literature values. An initial study isolated the effects of cortical density and stiffness on tibial strain during a simulated eight week training period. Tibial strains and cortical microcracking correlated to initial cortical modulus, with all simulations presenting peak anteromedial tensile strains (1047-1600 µstrain) near day 11. Average cortical densities decreased by 7-8 percent of their nominal value by day 11, but the overall density change was &lt;2% by the end of the simulated training period, in line with reported results. This study demonstrates the benefits of multi-scale models for investigating stress fracture risk and indicates that peak tibial strain, and thus injury risk, may increase early in a high intensity training program. Future studies could optimize training volume and recovery time to reduce injury risk during the most vulnerable training periods.

Using food fortification to improve vitamin D bioaccessibility and intakes

Vitamin D intakes and status are low in many countries due to seasonal UVB exposure variation and the fact that few foods are naturally vitamin D rich. Data modelling studies show that vitamin D intakes increase with food fortification, and countries with mandatory fortification policies have higher vitamin D intakes and status compared to countries without. While many foods can be vitamin D fortified, vitamin D bioavailability differs depending on fortification methods, food structure and composition. Randomised controlled trials (RCT) report that vitamin D2 bioavailability varies between foods, whereas vitamin D3 is bioavailable from many foods. In vitro studies suggest that altering the lipid composition of fortified foods increases vitamin D3 absorption. Olive oil increased vitamin D3 absorption during in vitro digestion compared to other dietary oils. Additionally, when vitamin D3 was incorporated into micelles formed from in vitro digestion of olive oil, more vitamin D3 was absorbed compared to other dietary oils. However, in a human postprandial study, a preformed vitamin D3 micelle dairy drink did not increase vitamin D3 absorption, and a vitamin D3 olive dairy drink increased vitamin D3 absorption in vitamin D insufficient participants only. Action is urgently needed to improve vitamin D intakes and status worldwide. Food fortification improves vitamin D intakes; however, fortification strategies unique to each country are needed. This review will synthesise the literature describing data modelling and intervention trials that assess the safety and efficacy of vitamin D fortification strategies, and those manipulating food composition to alter vitamin D bioavailability from fortified foods. Additionally, RCT examining the impact of vitamin D fortification strategies on vitamin D intakes and status over time are reviewed.

Once daily calcium (1000 mg) and vitamin D (1000 IU) supplementation during military training prevents increases in biochemical markers of bone resorption but does not affect tibial microarchitecture in Army recruits

Basic combat training (BCT) is a period of novel physical training including load carriage resulting in higher risk of stress fracture compared to any other time during military service. Prior trials reported a 20% reduction in stress fracture incidence with Ca and vitamin D (Ca + D) supplementation (2000 mg Ca, 800 IU vitamin D), and greater increases in tibia vBMD during BCT compared to placebo. The primary objective of this randomized, double-blind, placebo-controlled trial was to determine the efficacy of a lower dose of Ca (1000 mg/d Ca, 1000 IU vit D) on PTH, bone biomarkers and tibial microarchitecture during BCT. One hundred volunteers (50 males, 50 females; mean age 21.8 ± 3.5 y) were block randomized by race and sex to receive a daily Ca + D fortified food bar or placebo. Anthropometrics, dietary intake, fasted blood draws and high resolution pQCT scans of the distal and mid-shaft tibia were obtained at the start of BCT and 8 wks later at the conclusion of training. As compliance was 98% in both treatment groups, an intent-to-treat analysis was used. At the distal tibia, total vBMD, Tb.vBMD, Tb.N, Th.Th and Tb.BV/TV increased (+1.07 to 2.12% for all, p < 0.05) and Tb.Sp decreased (0.96 to 1.09%, p < 0.05) in both treatment groups. At the mid-shaft, Ct.Pm increased (+0.18 to 0.21%, p = 0.01) and Ct.vBMD decreased (-0.48 to -0.77%, p < 0.001) in both groups. Ca + D prevented increases in CTX and TRAP, which were observed in the placebo group (group-by-time, p < 0.05). Mean circulating 25OHD, BAP, P1NP and iCa increased and PTH decreased in both treatment groups (p < 0.05). These results, in agreement with other studies, suggest that bone microarchitectural changes indicative of bone formation occur during BCT. While Ca + D supplementation at lower doses than those tested in previous studies prevented increases in biochemical markers of bone resorption in this study, there were no significant changes in bone tissue after 8 wks of Army BCT.

Perspectives on the systematic review for the 2020 Dietary Reference Intakes for Koreans for calcium

An accurate assessment of the recommended calcium (Ca) intake may contribute to reducing the risk of fractures and chronic diseases, ultimately improving quality of life. This review was performed to summarize key findings of Ca studies, investigate the effect of Ca intake on health outcomes, and determine the adequacy of evidence to revise the 2015 Dietary Reference Intakes for Koreans (KDRIs) for Ca in 2020. Databases were searched for intervention studies that assessed health outcomes by providing Ca in diets or as supplements. The framework of the systematic review comprised conducting literature searches, data extraction, quality assessment of the literature, and summarizing key findings relevant to set the Estimated Average Requirement (EAR) and Tolerable Upper Intake Level (UL) for Ca for the 2020 KDRI. The final search was performed in June 2019. A total of 13,309 studies were identified through databases and manual search. Sixtyfive studies were included in the final quality assessment and were summarized according to health indicators. As bone health was used as an indicator of the EAR for Ca, literature reports on bone health were further categorized by the life-cycle stage of the participants. This systematic review did not find new evidence that could be applied to the general Korean adult population, including postmenopausal women, for defining a new EAR for Ca in the 2020 KDRIs. Evidence in most of the reviewed literature was considered weak; however, some evidence was found that could improve the criteria on how the EAR for Ca was determined in children and adolescents. A review of the literature for the 2020 KDRIs for Ca did not find strong evidence in order to change the recommended values of the 2015 KDRIs. More clinical interventions are required among Koreans to strengthen the body of evidence to warrant the revision of the KDRIs.

Breakfast Skipping Is Associated with Vitamin D Deficiency among Young Adults entering Initial Military Training

BACKGROUND

Vitamin D deficiency (VDD), defined as serum 25-hydroxyvitamin D (25[OH]D) levels < 20 ng/mL [to convert 25[OH]D ng/mL to nmol/L, multiply by 2.5]) is prevalent in young adults and has been associated with adverse health outcomes, including stress fracture during periods of increased physical activity such as military training. Foods commonly consumed at breakfast provide an important source of vitamin D, yet breakfast skipping is common among young adults. However, whether breakfast skipping is associated with VDD in young adults is unclear.

OBJECTIVES

This study aimed to determine whether breakfast skipping is associated with odds of VDD among recruits entering initial military training (IMT), and with changes in serum 25(OH)D during IMT. In addition, whether diet quality and vitamin D intake mediated these associations was determined.

DESIGN

Secondary analysis of individual participant data collected during five IMT studies. Breakfast skipping (≥ 3 times/week) was self-reported. Dietary intake was determined using food frequency questionnaires, and vitamin D status was assessed using circulating 25(OH)D concentrations pre- and post-IMT.

PARTICIPANTS AND SETTING

Participants were healthy US Army, US Air Force, and US Marine recruits (N = 1,569, 55% male, mean ± standard deviation age 21 ± 4 years) entering military service between 2010 and 2015 at Fort Jackson, SC; Fort Sill, OK; Lakeland Air Force Base, TX; or the Marine Corps Recruit Depot, Parris Island, SC.

MAIN OUTCOME MEASURES

Primary outcomes were VDD pre-IMT and change in 25(OH)D from pre- to post-IMT.

STATISTICAL ANALYSIS PERFORMED

Associations were determined using multivariate-adjusted logistic and linear regression and mediation models.

RESULTS

Forty-six percent of military recruits were classified as breakfast skippers pre-IMT, and 30% were VDD. Breakfast skipping was associated with a higher odds of pre-IMT VDD (odds ratio 1.5, 95% CI 1.1 to 1.9), and lower vitamin D intake and diet quality were partial mediators of the association. Serum 25(OH)D concentrations improved (P = 0.01) among habitual breakfast skippers versus nonskippers during IMT; however, regression to the mean could not be ruled out. Neither change in diet quality nor vitamin D intake were associated with change in 25(OH)D concentrations during IMT.

CONCLUSIONS

Breakfast skipping is prevalent among incoming military recruits and is associated with VDD. This relationship may be mediated by lower diet quality and vitamin D intake.

Vitamin D Food Fortification and Biofortification Increases Serum 25-Hydroxyvitamin D Concentrations in Adults and Children: An Updated and Extended Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Low vitamin D status is a global public health issue that vitamin D food fortification and biofortification may help to alleviate.

OBJECTIVES

We investigated the effect of vitamin D food fortification and biofortification on circulating 25-hydroxyvitamin D (25(OH)D) concentrations. We expanded the scope of earlier reviews to include adults and children, to evaluate effects by vitamin D vitamer, and investigate linear and nonlinear dose-response relations.

METHODS

We conducted a systematic review and meta-analysis. We searched CINAHL, MEDLINE, PubMed, Embase, the Cochrane Library, and gray and unpublished literature sites for randomized controlled trials, including people of all ages, with the criteria: absence of illness affecting vitamin D absorption, duration ≥4 wk, equivalent placebo food control, dose quantification, dose ≥5 μg/d, baseline and endpoint or absolute change in 25(OH)D concentrations reported, random allocation, and participant blinding. Quality was assessed using the Jadad Scale.

RESULTS

Data from 34 publications (2398 adults: 1345 intervention, 1053 controls; 1532 children: 970 intervention, 562 controls) were included. Random-effects meta-analysis of all studies combined (mean dose 16.2 μg/d) indicated a pooled treatment effect of 21.2 nmol/L (95% CI: 16.2, 26.2), with a greater effect for studies using cholecalciferol than ergocalciferol. Heterogeneity was high (I2  > 75%). Metaregression analyses for all studies combined suggested positive effect differences for baseline circulating 25(OH)D concentrations <50 nmol/L, dose ≥10 μg/d and a negative effect difference when the intervention arm included a calcium dose ≥500 mg/d greater than the control arm. Dose-response rates were found to be nonlinear (Wald test for nonlinearity P < 0.001). For all studies combined, a threshold occurred at ∼26 nmol/L for a dose of ∼21 μg/d.

CONCLUSIONS

These results support use of vitamin D food fortification to improve circulating 25(OH)D circulations in populations. This work was registered with PROSPERO as CRD42020145497.

Energy Restriction Suppresses Muscle Protein Synthesis, and High Protein Diets Extend Protein Half-Lives Across the Muscle Proteome in Obese Female Zucker Rats

BACKGROUND

Effects of high protein (HP) diets and prolonged energy restriction (ER) on integrated muscle protein kinetics have not been determined.

OBJECTIVE

The objective of this study was to measure protein kinetics in response to prolonged ER and HP on muscle protein synthesis (MPS; absolute rates of synthesis) and muscle protein breakdown (MPB; half-lives) for proteins across the muscle proteome.

METHODS

Female 6-wk-old obese Zucker rats (Leprfa+/fa+, n = 48) were randomly assigned to one of four diets for 10 wk: ad libitum-standard protein (AL-SP; 15% kcal from protein), AL-HP (35% kcal from protein), ER-SP, and ER-HP (both fed 60% feed consumed by AL-SP). During week 10, heavy/deuterated water (2H2O) was administered by intraperitoneal injection, and isotopic steady-state was maintained via 2H2O in drinking water. Rats were euthanized after 1 wk, and mixed-MPS as well as fractional replacement rate (FRR), relative concentrations, and half-lives of individual muscle proteins were quantified in the gastrocnemius. Data were analyzed using 2-factor (energy × protein) ANOVAs and 2-tailed t-tests or binomial tests as appropriate.

RESULTS

Absolute MPS was lower in ER than AL for mixed-MPS (-29.6%; P < 0.001) and MPS of most proteins measured [23/26 myofibrillar, 48/60 cytoplasmic, and 46/60 mitochondrial (P < 0.05)], corresponding with lower gastrocnemius mass in ER compared with AL (-29.4%; P < 0.001). Although mixed-muscle protein half-life was not different between groups, prolonged half-lives were observed for most individual proteins in HP compared with SP in ER and AL (P < 0.001), corresponding with greater gastrocnemius mass in HP than SP (+5.3%; P = 0.043).

CONCLUSIONS

ER decreased absolute bulk MPS and most individual MPS rates compared with AL, and HP prolonged half-lives of most proteins across the proteome. These data suggest that HP, independent of energy intake, may reduce MPB, and reductions in MPS may contribute to lower gastrocnemius mass during ER by reducing protein deposition in obese female Zucker rats.

Feeding female soldiers: Consideration of sex-specific nutrition recommendations to optimise the health and performance of military personnel

Appropriate nutrition recommendations are required to optimise the health and performance of military personnel, yet limited data are available on whether male and female military personnel have different nutrition requirements.

OBJECTIVES

To consider the evidence for sex-specific nutrition requirements to optimise the health and performance of military personnel.

DESIGN

Narrative review.

METHODS

Published literature was reviewed, with a focus on sex-specific requirements, in the following areas: nutrition for optimising muscle mass and function, nutrition during energy deficit, and nutrition for reproductive and bone health.

RESULTS

There are limited data on sex differences in protein requirements but extant data suggest that, despite less muscle mass, on average, in women, sex-specific protein feeding strategies are not required to optimise muscle mass in military-aged individuals. Similarly, despite sex differences in metabolic and endocrine responses to energy deficit, current data do not suggest a requirement for sex-specific feeding strategies during energy deficit. Energy deficit impairs health and performance, most notably bone and reproductive health and these impairments are greater for women. Vitamin D, iron and calcium are important nutrients to protect the bone health of female military personnel due to increased risk of stress fracture.

CONCLUSIONS

Women have an increased incidence of bone injuries, less muscle mass and are more susceptible to the negative effects of energy deficit, including compromised reproductive health. However, there are limited data on sex differences in response to various nutrition strategies designed to improve these elements of health and performance. Future studies should evaluate whether sex-specific feeding recommendations are required.

Does vitamin D supplementation prevent SARS-CoV-2 infection in military personnel? Review of the evidence

For most individuals residing in Northwestern Europe, maintaining replete vitamin D status throughout the year is unlikely without vitamin D supplementation and deficiency remains common. Military studies have investigated the association with vitamin D status, and subsequent supplementation, with the risk of stress fractures particularly during recruit training. The expression of nuclear vitamin D receptors and vitamin D metabolic enzymes in immune cells additionally provides a rationale for the potential role of vitamin D in maintaining immune homeostasis. One particular area of interest has been in the prevention of acute respiratory tract infections (ARTIs). The aims of this review were to consider the evidence of vitamin D supplementation in military populations in the prevention of ARTIs, including SARS-CoV-2 infection and consequent COVID-19 illness. The occupational/organisational importance of reducing transmission of SARS-CoV-2, especially where infected young adults may be asymptomatic, presymptomatic or paucisymptomatic, is also discussed.

Promoting adaptive bone formation to prevent stress fractures in military personnel

Mechanical loading leads to adaptive bone formation - the formation of new bone on existing skeletal surfaces - which increases bone strength and fatigue resistance. The same mechanical loading can also cause microdamage to bone and development of a stress fracture through targeted remodelling. Stress fractures are common in military recruits and cause significant morbidity, lost training time, and discharge from military service. This narrative review proposes strategies to promote adaptive bone formation as a novel approach to mitigate the risk of stress fracture injuries during arduous military training. Exercise that is unaccustomed, dynamic, high-impact, multidirectional, intermittent, and includes extended rest periods to restore bone mechanosensitivity, is most osteogenic. New bone formation can take up to one year to mineralize, and so new exercise training programmes should be initiated well in advance of military activities with high risk of stress fracture. Bone mechanosensitivity is highest in adolescence, before puberty, and so increasing physical activity in youth is likely to protect skeletal health in later life, including for those in the military. Recent data show that adaptive bone formation takes place during initial military training. Adaptive bone formation can also be supported with adequate sleep, vitamin D, calcium, and energy availability. Further evidence on how strategies to promote adaptive bone formation affect stress fracture risk are required. Adaptive bone formation can be optimized with a range of training and nutritional strategies to help create a resilient skeleton, which may protect against stress fracture throughout military service.

Mediterranean diet - promotion and dissemination of healthy eating: proceedings of an exploratory seminar at the Radcliffe institute for advanced study

The traditional Mediterranean diet is considered the world's most evidence-based eating pattern for promoting health and longevity. However, institutional food environments and their busy consumers often sacrifice health benefits for the convenience of faster and cheaper foods that generally are of lower quality and are more processed, and thus, contribute to the current epidemics of obesity and diabetes. Expert consensus has even identified the Mediterranean diet as the easiest to follow among healthy eating patterns. Nonetheless, fewer American families cook at home and many food services have been slow to implement healthier food options compatible with the Mediterranean diet. In September 2019, we convened a group of thought leaders at an exploratory seminar entitled: "Mediterranean Diet: Promotion and Dissemination of Healthy Eating", hosted by the Radcliffe Institute for Advanced Studies at Harvard University. The multidisciplinary faculty discussed best practices for translating traditional Mediterranean lifestyle principles to modern society.

Tibial Macrostructure and Microarchitecture Adaptations in Women During 44 Weeks of Arduous Military Training

Bone adapts to unaccustomed, high-impact loading but loses mechanosensitivity quickly. Short periods of military training (≤12 weeks) increase the density and size of the tibia in women. The effect of longer periods of military training, where the incidence of stress fracture is high, on tibial macrostructure and microarchitecture in women is unknown. This observational study recruited 51 women (age 19 to 30 years) at the start of 44 weeks of British Army Officer training. Tibial volumetric bone mineral density (vBMD), geometry, and microarchitecture were measured by high-resolution peripheral quantitative computed tomography (HRpQCT). Scans of the right tibial metaphysis (4% site) and diaphysis (30% site) were performed at weeks 1, 14, 28, and 44. Measures of whole-body areal bone mineral density (aBMD) were obtained using dual-energy X-ray absorptiometry (DXA). Blood samples were taken at weeks 1, 28, and 44, and were analyzed for markers of bone formation and resorption. Trabecular vBMD increased from week 1 to 44 at the 4% site (3.0%, p < .001). Cortical vBMD decreased from week 1 to 14 at the 30% site (-0.3%, p < .001). Trabecular area decreased at the 4% site (-0.4%); trabecular bone volume fraction (3.5%), cortical area (4.8%), and cortical thickness (4.0%) increased at the 4% site; and, cortical perimeter increased at the 30% site (0.5%) from week 1 to 44 (p ≤ .005). Trabecular number (3.5%) and thickness (2.1%) increased, and trabecular separation decreased (-3.1%), at the 4% site from week 1 to 44 (p < .001). Training increased failure load at the 30% site from week 1 to 44 (2.5%, p < .001). Training had no effect on aBMD or markers of bone formation or resorption. Tibial macrostructure and microarchitecture continued to adapt across 44 weeks of military training in young women. Temporal decreases in cortical density support a role of intracortical remodeling in the pathogenesis of stress fracture. © 2021 Crown copyright. Journal of Bone and Mineral Research © 2021 American Society for Bone and Mineral Research (ASBMR). This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

The Male Athlete Triad-A Consensus Statement From the Female and Male Athlete Triad Coalition Part II: Diagnosis, Treatment, and Return-To-Play

ABSTRACT

The Male Athlete Triad is a medical syndrome most common in adolescent and young adult male athletes in sports that emphasize a lean physique, especially endurance and weight-class athletes. The 3 interrelated conditions of the Male Athlete Triad occur on spectrums of energy deficiency/low energy availability (EA), suppression of the hypothalamic-pituitary-gonadal axis, and impaired bone health, ranging from optimal health to clinically relevant outcomes of energy deficiency/low EA with or without disordered eating or eating disorder, functional hypogonadotropic hypogonadism, and osteoporosis or low bone mineral density with or without bone stress injury (BSI). Because of the importance of bone mass acquisition and health concerns in adolescence, screening is recommended during this time period in the at-risk male athlete. Diagnosis of the Male Athlete Triad is best accomplished by a multidisciplinary medical team. Clearance and return-to-play guidelines are recommended to optimize prevention and treatment. Evidence-based risk assessment protocols for the male athlete at risk for the Male Athlete Triad have been shown to be predictive for BSI and impaired bone health and should be encouraged. Improving energetic status through optimal fueling is the mainstay of treatment. A Roundtable on the Male Athlete Triad was convened by the Female and Male Athlete Triad Coalition in conjunction with the 64th Annual Meeting of the American College of Sports Medicine in Denver, Colorado, in May of 2017. In this second article, the latest clinical research to support current models of screening, diagnosis, and management for at-risk male athlete is reviewed with evidence-based recommendations.

Military nutrition research: Contemporary issues, state of the science and future directions

The importance of diet and nutrition to military readiness and performance has been recognized for centuries as dietary nutrients sustain health, protect against illness, and promote resilience, performance and recovery. Contemporary military nutrition research is increasingly inter-disciplinary with emphasis often placed on the broad topics of (1) determining operational nutrition requirements in all environments, (2) characterizing nutritional practices of military personnel relative to the required (role/environment) standards, and (3) developing strategies for improving nutrient delivery and individual choices. This review discusses contemporary issues shared internationally by military nutrition research programmes, and highlights emerging topics likely to influence future military nutrition research and policy. Contemporary issues include improving the diet quality of military personnel, optimizing operational rations, and increasing understanding of biological factors influencing nutrient requirements. Emerging areas include the burgeoning field of precision nutrition and its technological enablers.

Biomechanical Basis of Predicting and Preventing Lower Limb Stress Fractures During Arduous Training

PURPOSE OF REVIEW

Stress fractures at weight-bearing sites, particularly the tibia, are common in military recruits and athletes. This review presents recent findings from human imaging and biomechanics studies aimed at predicting and preventing stress fractures.

RECENT FINDINGS

Peripheral quantitative computed tomography (pQCT) provides evidence that cortical bone geometry (tibial width and area) is associated with tibial stress fracture risk during weight-bearing exercise. The contribution of bone trabecular microarchitecture, cortical porosity, and bone material properties in the pathophysiology of stress fractures is less clear, but high-resolution pQCT and new techniques such as impact microindentation may improve our understanding of the role of microarchitecture and material properties in stress fracture prediction. Military studies demonstrate osteogenic outcomes from high impact, repetitive tibial loading during training. Kinetic and kinematic characteristics may influence stress fracture risk, but there is no evidence that interventions to modify biomechanics can reduce the incidence of stress fracture. Strategies to promote adaptive bone formation, in combination with improved techniques to assess bone strength, present exciting opportunities for future research to prevent stress fractures.

Vitamin D and Stress Fractures in Sport: Preventive and Therapeutic Measures-A Narrative Review

There are numerous risk factors for stress fractures that have been identified in literature. Among different risk factors, a prolonged lack of vitamin D (25(OH)D) can lead to stress fractures in athletes since 25(OH)D insufficiency is associated with an increased incidence of a fracture. A 25(OH)D value of <75.8 nmol/L is a risk factor for a stress fracture. 25(OH)D deficiency is, however, only one of several potential risk factors. Well-documented risk factors for a stress fracture include female sex, white ethnicity, older age, taller stature, lower aerobic fitness, prior physical inactivity, greater amounts of current physical training, thinner bones, 25(OH)D deficiency, iron deficiency, menstrual disturbances, and inadequate intake of 25(OH)D and/or calcium. Stress fractures are not uncommon in athletes and affect around 20% of all competitors. Most athletes with a stress fracture are under 25 years of age. Stress fractures can affect every sporty person, from weekend athletes to top athletes. Stress fractures are common in certain sports disciplines such as basketball, baseball, athletics, rowing, soccer, aerobics, and classical ballet. The lower extremity is increasingly affected for stress fractures with the locations of the tibia, metatarsalia and pelvis. Regarding prevention and therapy, 25(OH)D seems to play an important role. Athletes should have an evaluation of 25(OH)D -dependent calcium homeostasis based on laboratory tests of 25-OH-D₃, calcium, creatinine, and parathyroid hormone. In case of a deficiency of 25(OH)D, normal blood levels of ≥30 ng/mL may be restored by optimizing the athlete’s lifestyle and, if appropriate, an oral substitution of 25(OH)D. Very recent studies suggested that the prevalence of stress fractures decreased when athletes are supplemented daily with 800 IU 25(OH)D and 2000 mg calcium. Recommendations of daily 25(OH)D intake may go up to 2000 IU of 25(OH)D per day.

Healthy Eating Index and Nutrition Biomarkers among Army Soldiers and Civilian Control Group Indicate an Intervention Is Necessary to Raise Omega-3 Index and Vitamin D and Improve Diet Quality

Diet quality and nutrition status are important for optimal health and military performance. Few studies have simultaneously evaluated diet quality and biochemical markers of nutritional status of military service members. The Healthy Eating Index (HEI) can be used to assess dietary quality and adherence to federal nutrition guidelines. The aim of this study was to assess soldiers' diet quality and nutritional status and compare results to a civilian control group.

METHODS

A cross-sectional study was conducted with 531 soldiers. A food frequency questionnaire was used to calculate HEI scores. A blood sample was collected for analysis of select nutrition biochemical markers. Non-parametric analyses were conducted to compare the diet quality and nutritional status of soldiers and controls. Differences in non-normally distributed variables were determined by using the Wilcoxon signed-rank test.

RESULTS

Soldiers had an HEI score of 59.9 out of 100, marginally higher than the control group (55.4). Biochemical markers of interest were within normal reference values for soldiers, except for the omega-3 index and vitamin D.

CONCLUSIONS

This study identified dietary components that need improvement and deficits in biochemical markers among soldiers. Improving diet quality and nutritional status should lead to better health, performance, and readiness of the force.

Evaluation of the current methods used for assessing dietary intake in military research settings: a scoping review

INTRODUCTION

It is important to collate the literature that has assessed dietary intake within military settings to establish which methods are commonly used and which are valid so that accurate nutrition recommendations can be made. This scoping review aims to identify which methods are typically used to assess dietary intake in military settings and which of these have been validated. This review also aims to provide a recommendation as to which method(s) should be used in military settings.

METHODS

This scoping review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. Searches were conducted in PubMed, Web of Science and SPORTDiscus with the most recent search executed on 12th June 2020. Eligible studies had to report original data, assess and quantify dietary intake and have been published in peer-reviewed academic journals. The reporting bias was calculated for each study where possible.

RESULTS

Twenty-eight studies used a single method to assess dietary intake and seven studies used a combination of methods. The most commonly used methods were the gold standard food intake/waste method, Food Frequency Questionnaire (FFQ) or a food diary (FD). The only method to date that has been validated in military settings is weighed food records (WFR).

CONCLUSIONS

The food intake/waste method or WFR should be used where feasible. Where this is not practical the FFQ or FD should be considered with control measures applied. There is currently not sufficient evidence to state that using multiple methods together improves validity.

Energy Deficiency in Soldiers: The Risk of the Athlete Triad and Relative Energy Deficiency in Sport Syndromes in the Military

Military personnel experience energy deficit (total energy expenditure higher than energy intake), particularly during combat training and field exercises where exercising energy expenditures are high and energy intake is reduced. Low energy availability (energy intake minus exercising energy expenditure expressed relative to fat free mass) impairs endocrine function and bone health, as recognized in female athletes as the Female Athlete Triad syndrome. More recently, the Relative Energy Deficiency in Sport (RED-S) syndrome encompasses broader health outcomes, physical and cognitive performance, non-athletes, and men. This review summarizes the evidence for the effect of low energy availability and energy deficiency in military training and operations on health and performance outcomes. Energy availability is difficult to measure in free-living individuals but doubly labeled water studies demonstrate high total energy expenditures during military training; studies that have concurrently measured energy intake, or measured body composition changes with DXA, suggest severe and/or prolonged energy deficits. Military training in energy deficit disturbs endocrine and metabolic function, menstrual function, bone health, immune function, gastrointestinal health, iron status, mood, and physical and cognitive performance. There are more data for men than women, and little evidence on the chronic effects of repeated exposures to energy deficit. Military training impairs indices of health and performance, indicative of the Triad and RED-S, but the multi-stressor environment makes it difficult to isolate the independent effects of energy deficiency. Studies supplementing with energy to attenuate the energy deficit suggest an independent effect of energy deficiency in the disturbances to metabolic, endocrine and immune function, and physical performance, but randomized controlled trials are lacking.

Markers of Bone Health and Impact of Whey Protein Supplementation in Army Initial Entry Training Soldiers: A Double-Blind Placebo-Controlled Study

Training civilians to be soldiers is a challenging task often resulting in musculoskeletal injuries, especially bone stress injuries. This study evaluated bone health biomarkers (P1NP/CTX) and whey protein or carbohydrate supplementations before and after Army initial entry training (IET). Ninety male IET soldiers participated in this placebo-controlled, double-blind study assessing carbohydrate and whey protein supplementations. Age and fat mass predicted bone formation when controlling for ethnicity, explaining 44% (p < 0.01) of bone formation variations. Age was the only significant predictor of bone resorption (p = 0.02) when controlling for run, fat, and ethnicity, and these factors together explained 32% of the variance in bone resorption during week one (p < 0.01). Vitamin D increased across training (p < 0.01). There was no group by time interaction for supplementation and bone formation (p = 0.75), resorption (p = 0.73), Vitamin D (p = 0.36), or calcium (p = 0.64), indicating no influence of a supplementation on bone biomarkers across training. Age, fitness, fat mass, and ethnicity were important predictors of bone metabolism. The bone resorption/formation ratio suggests IET soldiers are at risk of stress injuries. Male IET soldiers are mildly to moderately deficient in vitamin D and slightly deficient in calcium throughout training. Whey protein or carbohydrate supplementations did not affect the markers of bone metabolism.

Low serum 25-hydroxyvitamin D status in the pathogenesis of stress fractures in military personnel: An evidenced link to support injury risk management

Stress fractures are common amongst healthy military recruits and athletes. Reduced vitamin D availability, measured by serum 25-hydroxyvitamin D (25OHD) status, has been associated with stress fracture risk during the 32-week Royal Marines (RM) training programme. A gene-environment interaction study was undertaken to explore this relationship to inform specific injury risk mitigation strategies. Fifty-one males who developed a stress fracture during RM training (n = 9 in weeks 1-15; n = 42 in weeks 16-32) and 141 uninjured controls were genotyped for the vitamin D receptor (VDR) FokI polymorphism. Serum 25OHD was measured at the start, middle and end (weeks 1, 15 and 32) of training. Serum 25OHD concentration increased in controls between weeks 1-15 (61.8±29.1 to 72.6±28.8 nmol/L, p = 0.01). Recruits who fractured did not show this rise and had lower week-15 25OHD concentration (p = 0.01). Higher week-15 25OHD concentration was associated with reduced stress fracture risk (adjusted OR 0.55[0.32-0.96] per 1SD increase, p = 0.04): the greater the increase in 25OHD, the greater the protective effect (p = 0.01). The f-allele was over-represented in fracture cases compared with controls (p<0.05). Baseline 25OHD status interacted with VDR genotype: a higher level was associated with reduced fracture risk in f-allele carriers (adjusted OR 0.39[0.17-0.91], p = 0.01). Improved 25OHD status between weeks 1-15 had a greater protective effect in FF genotype individuals (adjusted OR 0.31[0.12-0.81] vs. 1.78[0.90-3.49], p<0.01). Stress fracture risk in RM recruits is impacted by the interaction of VDR genotype with vitamin D status. This further supports the role of low serum vitamin D concentrations in causing stress fractures, and hence prophylactic vitamin D supplementation as an injury risk mitigation strategy.

Dietary Assessment Methods in Military and Veteran Populations: A Scoping Review

Optimal dietary intake is important for the health and physical performance of military personnel. For military veterans, the complex nature of transition into civilian life and sub-optimal dietary intake is a leading contributor to the increased burden of disease. A scoping review was undertaken to determine what is known about the assessment and reporting of dietary intakes within both military and veteran populations. In addition, this review determines if studies reporting on the dietary intake of military personnel or veterans include comparisons with dietary guidelines. Six databases were searched to identify papers published from the database inception to April 2019. Observational and intervention studies were searched to identify if they assessed and reported whole dietary intake data, reported data exclusively for a military or veteran population, and included only healthy populations. A total of 89 studies were included. The majority of studies used one dietary assessment method (n = 76, 85%) with fewer using multiple methods (n = 13, 15%). The most frequent methodology used was food frequency questionnaires (FFQ) (n = 40, 45%) followed by 24-hour recalls (n = 8, 9%) and food records (n = 8, 9%). The main dietary outcomes reported were macronutrients: carbohydrate, protein, fat, and alcohol (n = 66, 74%) with total energy intake reported in n = 59 (66%). Fifty four (61%) studies reported a comparison with country-specific dietary guidelines and 14 (16%) reported a comparison with the country-specific military guidelines. In conclusion, dietary intake in military settings is most commonly assessed via FFQs and 24-hour recalls. Dietary intake reporting is mainly focused around intakes of energy and macronutrients. Most studies compare against dietary guidelines, however, comparison to specific military dietary guidelines is minimal.

Musculoskeletal Injuries and United States Army Readiness. Part II: Management Challenges and Risk Mitigation Initiatives

Introduction

Noncombat injuries (“injuries”) threaten soldier health and United States (U.S.) Army medical readiness, accounting for more than twice as many outpatient medical encounters among active component (AC) soldiers as behavioral health conditions (the second leading cause of outpatient visits). Noncombat musculoskeletal injuries (MSKIs) account for more than 80% of soldiers’ injuries and 65% of medically nondeployable AC soldiers. This review focuses on MSKI risk reduction initiatives, management, and reporting challenges within the Army. The authors will summarize MSKI risk reduction efforts and challenges affecting MSKI management and reporting within the U.S. Army.

Materials/Methods

This review focuses on (1) initiatives to reduce the impact of MSKIs and risk for chronic injury/pain or long-term disability and (2) MSKI reporting challenges. This review excludes combat or battle injuries.

Results

Primary risk reduction Adherence to standardized exercise programming has reduced injury risk among trainees. Preaccession physical fitness screening may identify individuals at risk for injury or attrition during initial entry training. Forward-based strength and conditioning coaching (provided in the unit footprint) and nutritional supplementation initiatives are promising, but results are currently inconclusive concerning injury risk reduction.

Secondary risk reduction

Forward-based access to MSKI care provided by embedded athletic trainers and physical therapists within military units or primary care clinics holds promise for reducing MSKI-related limited duty days and nondeployability among AC soldiers. Early point-of-care screening for psychosocial risk factors affecting responsiveness to MSKI intervention may reduce risk for progression to chronic pain or long-term disability.

Tertiary risk reduction

Operational MSKI metrics enable commanders and clinicians to readily identify soldiers with nonresolving MSKIs. Monthly injury reports to Army leadership increase command focus on soldiers with nonresolving MSKIs.

Conclusions

Standardized exercise programming has reduced trainee MSKI rates. Secondary risk reduction initiatives show promise for reducing MSKI-related duty limitations and nondeployability among AC soldiers; timely identification/evaluation and appropriate, early management of MSKIs are essential. Tertiary risk reduction initiatives show promise for identifying soldiers whose chronic musculoskeletal conditions may render them unfit for continued military service.

Clinicians must document MSKI care with sufficient specificity (including diagnosis and external cause coding) to enable large-scale systematic MSKI surveillance and analysis informing focused MSKI risk reduction efforts. Historical changes in surveillance methods and injury definitions make it difficult to compare injury rates and trends over time. However, the U.S. Army’s standardized injury taxonomy will enable consistent classification of current and future injuries by mechanism of energy transfer and diagnosis. The Army’s electronic physical profiling system further enables

standardized documentation of MSKI-related duty/work restrictions and mechanisms of injury. These evolving surveillance tools ideally ensure continual advancement of military injury surveillance and serve as models for other military and civilian health care organizations.

Short-Term Intermittent Hypoxic Resistance Training Does Not Impair Osteogenic Response in Sea Level Residents

Background: Osteogenic responses induced by training under hypoxia remain unclear. We aimed to investigate whether intermittent hypoxic resistance training affects osteogenic responses. Materials and Methods: Sixteen male participants underwent resistance training under normoxia (NRT; n = 7) or hypoxia (HRT; O₂ = 14.4%, n = 9), twice a week for 8 weeks. The HRT group exercised and rested for 30 minutes under hypoxia, with total hypoxic exposure time in one session of ∼60 minutes. At pre- and postexperiment, bone mineral density (BMD) of the whole body and right proximal femur was measured. At the first and last training sessions, bone alkaline phosphatase (BAP), osteocalcin (OC), cross-linked N-telopeptide of type I collagen (NTx), type I collagen cross-linked C-telopeptide (ICTP), interleukin-6 (IL-6), and blood lactate (La) concentration were analyzed at rest and postexercise. Results: BMD did not change with training and hypoxia. Although BAP, OC, and ICTP levels at rest significantly increased with training (p < 0.01, 0.05, and 0.05, respectively), they did not change with hypoxia. NTx and IL-6 did not change. Additionally, changing patterns of bone markers and La induced by a single bout of exercise were similar among groups in both training sessions. Conclusions: Short-term resistance training enhanced overall bone metabolism, regardless of the oxygen level. Hypoxia has no effects on osteogenic responses.

Skeletal macro- and microstructure adaptations in men undergoing arduous military training

PURPOSE

Short periods of basic military training increase the density and size of the tibia, but the adaptive response of bone microarchitecture, a key component of bone strength, is not fully understood.

METHODS

Tibial volumetric bone mineral density (vBMD), geometry, microarchitecture and mechanical properties were measured using high-resolution peripheral quantitative computed tomography in 43 male British Army infantry recruits (mean ± SD, age 21 ± 3 years, height 1.76 ± 0.06 m, body mass 76.5 ± 9.4 kg). Bilateral scans were performed at the distal tibia at the start (week 1) and end (week 13) of basic military training. Concurrent measures were obtained for whole-body areal bone mineral density (aBMD) using DXA, and markers of bone metabolism (βCTX, P1NP, PTH, total 25(OH)D and ACa) from venous blood.

RESULTS

Training increased areal BMD for total body (1.4%) and arms (5.2%) (P ≤ 0.031), but not legs and trunk (P ≥ 0.094). Training increased trabecular (1.3 to 1.9%) and cortical vBMD (0.6 to 0.9%), trabecular volume (1.3 to 1.9%), cortical thickness (3.2 to 5.2%) and cortical area (2.6 to 2.8%), and reduced trabecular area (-0.4 to -0.5%) in both legs (P < 0.001). No changes in trabecular number, thickness and separation, cortical porosity, stiffness or failure load were observed (P ≥ 0.188). βCTX decreased (-0.11 μg∙l^-1, P < 0.001) and total 25(OH)D increased (9.4 nmol∙l^-1, P = 0.029), but no differences in P1NP, PTH or ACa were observed between timepoints (P ≥ 0.233).

CONCLUSION

A short period of basic military training increased density and altered geometry of the distal tibia in male military recruits. The osteogenic effects of basic military training are likely due to an increase in unaccustomed, dynamic and high-impact loading.

Vitamin D Supplementation in Military Personnel: A Systematic Review of Randomized Controlled Trials

CONTEXT

Vitamin D supplementation is important in military research because of its role in musculoskeletal health.

OBJECTIVE

This systematic review examined the effects of vitamin D supplementation on serum 25-hydroxyvitamin D (25(OH)D) concentrations and musculoskeletal health outcomes in military personnel.

DATA SOURCES

A comprehensive search was conducted using MEDLINE, EMBASE, CINAHL, SportDiscus, and the Cochrane Library databases and the reference lists of existing review articles and relevant studies.

STUDY SELECTION

Reviewers independently screened titles, abstracts, and full texts of the articles using predefined criteria.

STUDY DESIGN

Systematic review of randomized controlled trials (RCTs) using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement.

LEVEL OF EVIDENCE

Level 3.

DATA EXTRACTION

Three reviewers independently extracted data and assessed the methodological quality. Mean differences with 95% CI in serum 25(OH)D concentrations between the vitamin D and placebo arms were calculated.

RESULTS

Four RCTs were included in the qualitative analyses. The 25(OH)D concentrations were improved with 2000 IU/d supplementation (mean difference, 3.90 ng/mL; 95% CI, 0.22-7.58). A trial on female Navy recruits showed a significant decrease in stress fractures (risk ratio, 0.77; 95% CI, 0.62-0.95), particularly tibial fractures, from daily supplementation of 800 IU vitamin D and 2000 mg calcium.

CONCLUSION

There was a positive trend in 25(OH)D concentrations from higher doses of supplementary vitamin D in military submariners and a possible benefit to bone health when vitamin D was combined with calcium.