TY - JOUR
AU - PhD, Erin Gaffney-Stomberg, RD,
AB - ABSTRACT Nutrition is essential for maintaining peak health and performance of Warfighters. This review will focus on a series of nutrients of concern for female Warfighters. Biological function, dietary sources, and requirements will be reviewed, and recommendations for women in combat roles will be provided. Iron, essential for physical and cognitive performance, is critical for female Warfighters because of elevated dietary requirements as compared to male Warfighters, as well as declines in iron status that may occur in response to physical activities, such as military training. Calcium and vitamin D are essential for bone health, and should be considered in efforts to prevent stress fractures, which occur with greater frequency in female Warfighters as compared to their male counterparts. Folate, essential for the prevention of neural tube defects during pregnancy and gestation, is critical for female Warfighters because of elevated dietary requirements before pregnancy. Providing optimal levels of these nutrients will facilitate readiness as women prepare to serve in combat roles. INTRODUCTION Optimal nutrition is essential for maintaining peak health and performance of Warfighters. Failure to provide energy and nutrients at required levels results in measurable declines in cognitive and physical performance and, if chronic, may be associated with distinct nutritional deficiency disorders. Nutritional requirements and feeding procedures for all military personnel are published in Army Regulation (AR) 40-25 (BUMED 10110.6 and AFI 44-141 for the Navy and Air Force, respectively).1 This regulation, titled “Nutrition Standards and Education,” defines Military Dietary Reference Intakes (MDRIs or nutritional standards), establishes Nutritional Standards for Operational Rations (NSORs), defines responsibilities within the military food service program and outlines nutrition education policy. The Surgeon General of the U.S. Army holds Department of Defense responsibility for the regulation. The MDRIs are generally adapted from the U.S. Food and Nutrition Board's Recommended Dietary Allowances (RDAs), Dietary Reference Intakes (DRIs), and associated updates,2 although the requirement for calories and a number of nutrients is adjusted because of differences that may occur in military personnel as compared to the civilian population. Similarly, NSORs are based upon MDRIs and are intended to support nutrition requirements during actual or simulated combat situations. In many cases, MDRIs for female and male Warfighters are similar or the same, with notable exceptions. First, caloric requirements for female Warfighters participating in routine military activities (2,300 kcal/d) are reduced as compared to male Warfighters (3,250 kcal/d) because of the reduced body size (and lean body mass) of women as compared to men. Similarly, the protein requirement is reduced in female as compared to male Warfighters (72 vs. 91 g/d, respectively). A number of vitamin requirements are different in female as compared to male Warfighters, including vitamins A, C, and K, thiamin, riboflavin, and niacin. Similar to energy and protein requirements, these MDRIs are reduced in women as compared to men because of body size (and lean body mass). Notably, the requirement for iron is 50% greater for female as compared to male Warfighters (15 vs. 10 mg/d). Increased requirements for iron in women are due to the natural loss of iron that occurs through menstruation.3 It should be noted that AR 40-25 does not establish MDRIs for pregnant or lactating women, which may be of concern for female Warfighters, as requirements for a series of nutrients, to include iron and folate, are significantly elevated during pregnancy. Lastly, AR 40-25 does not address the potential benefit of particular nutrients, such as calcium and vitamin D, at levels beyond the MDRI in an effort to prevent injury (such as stress fractures) or influence other health outcomes that may affect female Warfighters with a greater frequency than male Warfighters, especially during initial entry training (IET) or other physically demanding activities that may affect nutrient requirements. This manuscript will focus on a series of nutrients of particular concern for female Warfighters as women prepare to enter combat Military Occupational Specialties (MOSs). Nutrients to be addressed include iron for the optimization of physical and cognitive performance, calcium and vitamin D for the maintenance of bone health, and folic acid for the prevention of neural tube defects (NTDs) during pregnancy. The biological roles of each of these nutrients will be described, followed by a review of recent evidence highlighting the importance of these nutrients for women in combat. IRON Iron is an essential mineral that confers function through incorporation into a series of proteins and enzymes. Many of these proteins and enzymes are essential for cognitive and physical performance. For example, iron is required for the transport and storage of oxygen, as both hemoglobin and myoglobin require iron for function. Iron is essential for energy metabolism, as iron incorporates into cytochromes, which function in electron transfer in the respiratory chain, and dehydrogenases, which function in substrate oxidation.4 Iron is also a component of aconitase, an enzyme within the tricarboxylic acid cycle. Iron occurs in the diet in both heme and nonheme forms. Heme iron is found primarily in meat products and is absorbed with greater efficiency (15–35%) than nonheme iron (2–20%).5 Iron absorption is affected by a number of factors; these include dietary enhancers and inhibitors of nonheme iron absorption. Ascorbic acid (vitamin C), found in fruits and vegetables, is an enhancer of nonheme iron absorption. Inhibitors of nonheme iron absorption include tannins, found in coffee and tea, and phytate, which binds a number of essential minerals and is found in grains and legumes. The RDA for iron is 8 mg/d for adult men and 18 mg/d for women between the ages of 19 and 50 (Table I). The RDA for iron is 27 mg/d during pregnancy. The MDRI for iron is 10 mg/d for men and 15 mg/d for women.1 The NSOR for iron is 15 mg/d for operational rations (ORs).1 TABLE I Nutrient Requirements: Iron, Calcium, Vitamin D, and Folate    RDA  MDRI  NSOR  OR  Iron (mg/d)   Men  8  10  15   Womena  18  15     Calcium (mg/d)b  1,000  1,000  1,000  Vitamin D (IU/d)  600  200  200  Folate (μg DFE per day)  400  400  400  Pregnancyc  600        Lactation  500           RDA  MDRI  NSOR  OR  Iron (mg/d)   Men  8  10  15   Womena  18  15     Calcium (mg/d)b  1,000  1,000  1,000  Vitamin D (IU/d)  600  200  200  Folate (μg DFE per day)  400  400  400  Pregnancyc  600        Lactation  500        RDA, Recommended Dietary Allowance; MDRI, Military Dietary Reference Intake; NSOR, Nutritional Standards for Operational Rations; OR, Operational Rations. a NSORs apply to both male and female Warfighters. b No differences in RDA or MDRI between men and women for calcium, vitamin D, or folate (excluding pregnancy). c MDRI values do not exist for pregnancy or lactation. View Large TABLE I Nutrient Requirements: Iron, Calcium, Vitamin D, and Folate    RDA  MDRI  NSOR  OR  Iron (mg/d)   Men  8  10  15   Womena  18  15     Calcium (mg/d)b  1,000  1,000  1,000  Vitamin D (IU/d)  600  200  200  Folate (μg DFE per day)  400  400  400  Pregnancyc  600        Lactation  500           RDA  MDRI  NSOR  OR  Iron (mg/d)   Men  8  10  15   Womena  18  15     Calcium (mg/d)b  1,000  1,000  1,000  Vitamin D (IU/d)  600  200  200  Folate (μg DFE per day)  400  400  400  Pregnancyc  600        Lactation  500        RDA, Recommended Dietary Allowance; MDRI, Military Dietary Reference Intake; NSOR, Nutritional Standards for Operational Rations; OR, Operational Rations. a NSORs apply to both male and female Warfighters. b No differences in RDA or MDRI between men and women for calcium, vitamin D, or folate (excluding pregnancy). c MDRI values do not exist for pregnancy or lactation. View Large Poor iron status, characterized clinically as iron deficiency (ID, diminished iron stores) and iron deficiency anemia (IDA, diminished iron stores coupled with reduced hemoglobin levels), is the most frequent single nutrient deficiency disorder in the world, affecting billions in both developed and developing nations. Poor iron status affects premenopausal women at a greater frequency than men, as iron requirements are greater for premenopausal women because of the loss of iron that occurs through menstruation.3 Population data collected in the United States indicate that ID affects up to 16% of females between the ages of 16 and 19, and that IDA affects up to 4% of females between the ages of 20 and 49.6 The impact of poor iron status on physical and cognitive performance in women has been reviewed extensively.7 Classic animal and human studies have documented the effects of IDA on aerobic work capacity and physical performance, as diminished levels of hemoglobin are linked with reduced oxygen-carrying capacity and maximal oxygen consumption. In one study, Gardner et al8 assessed the physical performance of women with varying levels of hemoglobin using a multistage incremental treadmill test and found that total time on the treadmill, percentage of women reaching the highest workload, and postexercise lactate levels all correlated with hemoglobin levels. The effects of ID (without anemia) on performance have also been studied in women, primarily in athletes. These studies noted detrimental effects of ID on endurance,9,–11 aerobic adaptation and metabolic responses,10,12 and muscle fatigue.13 A series of recent studies have assessed iron status in female Soldiers. In one cross-sectional study, McClung et al14 found that the prevalence of ID and IDA was 13.4% and 5.8%, respectively, at the start of U.S. Army basic combat training (BCT), but climbed to 32.8% and 20.9%, respectively, immediately following BCT. Longitudinal studies confirmed these data, to include the decline in iron status associated with military training.15 Declines in iron status over the course of BCT were associated with slower 2-mile run time, an indicator of aerobic performance. A number of studies have focused on preserving iron status in female Soldiers during military training. Such efforts have tested dietary supplements in capsule form15 and iron-fortified food products.16 In the first randomized, double-blind, placebo-controlled trial (RCT15), iron was provided to female Soldiers once per day in capsule form as an iron salt (ferrous sulfate, 15 mg elemental iron/d). As compared to placebo, iron capsules were not associated with adverse effects and attenuated declines in a series of indicators of iron status. Notably, consumption of supplemental iron affected both cognitive and physical performance. Consumption of the iron-containing capsules resulted in improvements in measures of mood (vigor), and 2-mile run time was improved at the end of BCT in Soldiers that began the course with IDA. In the second RCT,16 iron was provided twice per day in a fortified snack item (ferrous sulfate, 56 mg elemental iron/d). Although less effective for maintaining iron status than iron-containing capsules (likely due to inhibitors of iron absorption in the food matrix), the fortified food product attenuated declines in iron status in female Soldiers that began BCT with IDA as compared to their counterparts receiving a noniron-containing snack item. Most recently, research efforts have focused on determining the causes underlying the decline in iron status during training, and indicate that inflammation associated with physical activity results in the release of hepcidin, a protein that sequesters iron at the site of absorption and within macrophages, resulting in poor iron status. Elevated levels of hepcidin have been observed in male military personnel following training and are associated with markers of inflammation,17 although future studies will be required to determine whether inhibiting the hepcidin response to physical activity may be an effective approach to preventing declines in iron status in Warfighters. A number of factors should be addressed when considering iron status in women who engage in combat MOSs. First, sex differences in iron homeostasis may result in ID and IDA in premenopausal women, whereas men typically have robust iron stores and may suffer from iron overload if provided with dietary supplements containing iron or iron-fortified foods. Screening programs should be considered for female recruits as they enter military service, perhaps at the earliest point of medical contact, such as the Military Entrance Processing Station. A safe, nonexclusionary treatment paradigm should be designed for women who present with poor iron status at initial screening. Interventions should be considered in efforts to prevent declines in iron status associated with military training. Because of the potential logistic and safety difficulties associated with dietary supplements during training, iron-fortified food products, to include snacks, should be considered. Nutrition education programs should highlight the importance of iron for female Warfighters. Future studies should be conducted to determine iron status of female Warfighters beyond the IET environment, as questions remain regarding recovery from poor iron status following IET and at other critical points during a military career. For example, no data are currently available regarding iron status in female Warfighters during advanced individual (or technical) training, and studies assessing iron status during deployment are extremely limited.18 CALCIUM AND VITAMIN D Calcium and vitamin D are two micronutrients most often associated with bone health. Deficiency of either calcium or vitamin D results in reduced bone mineralization, and is associated with negative skeletal outcomes. During its most recent review of the research evidence, the Institute of Medicine (IOM) reaffirmed the RDA for calcium of 1,000 mg/d and increased the requirement for vitamin D to 600 IU/d for adults aged 19 to 50, citing skeletal health as the basis for this increase.19 Tolerable upper intake levels, the highest level at which habitual intake is likely to not increase adverse health effects, were set at 2,500 mg/d and 4,000 IU/d for calcium and vitamin D, respectively. The current MDRI for vitamin D is 200 IU/d for both women and men. The NSOR is 200 IU for ORs. The MDRI for calcium is 1,000 mg/d for both women and men; the NSOR is 1,000 mg for ORs. While calcium is obtained from the diet, vitamin D is a unique nutrient in that it can be gleaned in the diet as well as synthesized in the skin in response to UVB radiation. Regardless of source, vitamin D circulates as 25-hydroxyvitamin D (or 25(OH)D), which is the form of the vitamin used to determine status. When determining the RDA for vitamin D, the IOM identified the level of circulating 25(OH)D that was associated with skeletal health (20 ng/mL) and then estimated the amount of dietary vitamin D required to obtain this circulating level in the absence of sunlight (Fig. 1). There is mounting evidence supporting greater requirements of these micronutrients during military training to prevent stress fractures, as well as for additional nonskeletal effects that may require a higher daily intake. However, the IOM committee determined that at the time of review the nonskeletal health evidence was not substantial enough to be utilized when forming population-based recommendations; thus, additional research is warranted. FIGURE 1 View largeDownload slide Circulating 25(OH)D concentrations associated with bone outcomes. FIGURE 1 View largeDownload slide Circulating 25(OH)D concentrations associated with bone outcomes. The classical biochemical functions of calcium and vitamin D are in the maintenance of bone tissue. Bone is composed of a collagen matrix mineralized by hydroxyapatite crystals primarily containing calcium and phosphorus. Over 99% of body calcium is stored in the skeleton with the remainder in soft tissues and extracellular fluids including blood. Blood calcium is maintained within a narrow range in order to support vital functions such as nerve conduction and muscle contraction. Circulating calcium levels are maintained through the coordinated actions of the hypercalcemic hormone and parathyroid hormone (PTH) on a 3 organ axis: (1) the intestine, where dietary calcium is absorbed, (2) the kidney, where calcium is either reabsorbed or excreted in the urine, and (3) bone, the body's calcium reservoir. Decreases in circulating ionized calcium sensed by the parathyroid gland result in synthesis and secretion of PTH. The PTH stimulates renal activation of 25(OH)D to 1,25-dihydroxyvitamin D, the active hormone form of vitamin D, which then increases intestinal calcium absorption and bone resorption. In addition, PTH increases bone resorption and renal calcium reabsorption. In sum, the actions of PTH serve to raise blood calcium concentrations in part at the expense of bone. Chronically elevated PTH results in sustained bone resorption, thereby reducing bone density and increasing fracture risk. Vitamin D exerts its actions primarily through interaction with the vitamin D receptor (VDR), a member of the nuclear receptor superfamily. Vitamin D–bound VDR translocates to the nucleus and induces the expression of genes involved in many functions including mineral metabolism and cellular proliferation and differentiation. The VDR is expressed in a wide variety of tissues including intestinal epithelial cells and bone cells, where it regulates calcium metabolism; immune cells, where it regulates innate and adaptive immunity; and myocytes, where it induces cell protein synthesis and growth. As such, roles for vitamin D in protection against autoimmune disease, infection, type II diabetes and metabolic syndrome, cancer, and muscle function have been described.20 The roles of calcium and vitamin D in musculoskeletal health are of particular concern for the female Warfighter as stress fracture prevalence is higher in female compared to male trainees. Stress fractures occur as a result of repeated mechanical loading, which exceeds the skeleton's ability to adapt, and are among the most costly injuries to the military.21 Trainees are 17 times more likely to sustain a fracture than active duty personnel, with females at the highest risk.21 Reports estimate that 6 to 21% of female and 2 to 8% of male recruits will sustain a fracture during initial military training (although most recent data indicate that the incidence of stress fracture has declined significantly), and of those that fracture, approximate 60% are discharged from service.22,23 Calcium intake and vitamin D status are known modifiable risk factors for stress fracture.24 In an analysis of 1,200 females undergoing Navy training (600 stress fracture cases and 600 age, race, and length of service-matched controls), Burgi et al25 determined that females with circulating 25(OH)D <20 ng/mL exhibited double the risk of stress fracture compared to those with 25(OH)D ≥40 ng/mL. Similarly, the risk of stress fracture was 3.6-fold higher for male Finnish military recruits with 25(OH)D <30 ng/mL compared to those with levels > 30 ng/mL.26 Thus, circulating 25(OH)D concentrations higher than those used to establish the RDA for vitamin D may be required to protect against stress fractures during IET, and the level at which protection is imparted may be higher for females than males (Fig. 1). Importantly, female Navy recruits randomized to receive 2,000 mg/d supplemental calcium and 800 IU/d vitamin D exhibited a 20% reduction in stress fracture risk compared to those who received placebo capsules.27 Although this study provided important information about the efficacy of calcium and vitamin D supplementation to protect against stress fracture, no biochemical or bone density or strength data were collected, leaving questions about the mechanisms for the protective effects of these micronutrients. In an RCT designed to evaluate the effects of a food product fortified with calcium and vitamin D at levels used in the prior study, Gaffney-Stomberg et al28 determined that the fortified product improved bone responses to training at the distal tibia, increased circulating ionized calcium, and maintained PTH in males and females undergoing Army BCT compared to the unfortified placebo food product. Although no sex differences in response to supplementation were identified in this study, the data indicate that supplemental calcium and vitamin D at levels higher than the RDA are protective for both males and females, but may be particularly important for females given their higher prevalence of stress fractures. Vitamin D also has important functions in muscle physiology, which may be germane to female Warfighters. Muscle biopsies from adults with low 25(OH)D levels revealed atrophic changes in type II muscle fibers, the fiber type characterized by high force, speed, and power production.29 Conversely, vitamin D supplementation increased type II muscle fibers.30 There is also evidence that vitamin D status impacts muscle function and performance, as vitamin D may protect against falls in the elderly. In a meta-analysis of 8 RCTs, Bischoff-Ferrari et al31 found a 13% reduction in risk of falling in those receiving vitamin D supplementation (200–1,000 IU/d) and a 19% reduction with doses 700 to 1,000 IU/d, whereas consuming less than 700 IU/d did not result in risk reduction. In a prospective trial, Bischoff-Ferrari et al31,32 reported a 49% reduction in falls in elderly women who were provided with 800 IU vitamin D and 1,200 mg calcium per day for 3 months as compared to calcium alone suggesting synergistic effects on musculoskeletal health. Although the majority of studies exploring the effect of vitamin D on muscle function have been conducted in adults over the age of 50, studies with adolescents and young adults suggest a link between vitamin D status and muscle function. One study reported an association between 25(OH)D and muscle power, force, velocity, and jump height using jump mechanography in 12- to 14-year-old girls.33 In another, consuming 2,000 IU vitamin D per day for 4 months increased isometric strength and vertical jump height and reduced injury incidence in elite ballet dancers compared to controls,34 although this study was neither blinded nor randomized, potentially limiting the conclusions. Overall, limited evidence supports a role of vitamin D in muscle function and performance in elderly and potentially young adults, but studies designed to assess performance in military personnel are lacking. In summary, available data suggest intakes of calcium and vitamin D above the current RDA and MDRI may be necessary to support bone health and reduce injury risk in women undergoing IET. In both the Lappe et al27 and Gaffney-Stomberg et al27,28 studies, supplementation with 2,000 mg/d of calcium and 800 to 1,000 IU of vitamin D per day were found to be protective with no adverse events reported. These intakes represent 200% and 133 to 150% of the RDA for calcium and vitamin D, respectively. Although dietary intakes were not reported in the Lappe et al27 study, mean calcium intake from diet alone was 1,020 mg/d in the fortified group in the Gaffney-Stomberg et al study28, and 2,700 mg/d on average when supplemental intake was included. Thus, calcium intake greater than the RDA may be required but whether intake less than the upper intake level would be effective should be the focus of future research in order to optimize bone health while minimizing the potential for longer term health risks. Similar to iron, data regarding vitamin D and calcium status are lacking in female Warfighters following IET, during deployment, or later into military careers. Research in older adults and adolescents provides some evidence that vitamin D status impacts muscle performance, although future research evaluating the effects of vitamin D status on physical performance in military populations is warranted. FOLATE Folates are water-soluble B-complex vitamins that participate as enzyme co-substrates in the metabolism and synthesis of amino acids and nucleotides. In this role, folates serve as acceptors or donors of single carbon units, often referred to as “single-carbon metabolism.” The term “folate” refers to folic acid (pteroylmonoglutamic acid) and a series of related compounds exhibiting the biological activity of folic acid. Folate deficiencies result in impaired synthesis of DNA and RNA, which may result in impaired erythropoiesis and anemia. Folate occurs naturally in a variety of foods, such as leafy green vegetables and organ meats. Folate can also be found in breads, pastas, flour, and other grain products, as the U.S. Food and Drug Administration mandated the fortification of these products in 1998. Folate is a vitamin of concern for female Warfighters because of the importance of this nutrient before and during pregnancy and lactation. Folate requirements increase during pregnancy because of the increased number of single-carbon metabolism reactions required for nucleotide synthesis and cell division, as cell multiplication is required for uterine enlargement, placental development, and fetal growth. The RDA for folate is 400 μg of dietary folate equivalents (DFEs) for women above the age of 14, and increases to 600 μg DFE per day during pregnancy and 500 μg DFE per day during lactation. The MDRI for folate is 400 μg DFE per day. The NSOR is 400 μg DFE per day for ORs. Consuming adequate folate before and during pregnancy is critical for the prevention of NTDs. NTDs are congenital malformations that occur when the neural tube does not close during embryogenesis, and include anencephaly and spinal bifida. Anencephaly is lethal cranial defect, in which the cerebral cortex and overlying bone fail to develop. Spina bifida is a caudal defect, in which the spinal cord is dysplastic and the overlying spinal column is absent, resulting in paraplegia. The link between folate and NTDs is clear, as there is a relationship between folate intake, status, and the risk of NTDs.35,–37 Further, NTD rates have declined by over 25% in the United States since the mandatory folate fortification program began in 1998.38 Studies of folate intake and status in Warfighters are extremely limited. Booth et al39 observed declines in folate status during a 12-day training exercise in the tropics, and Klicka et al40 found that a significant portion of female cadets did not meet the MDRI for folate while attending the U.S. Military Academy. As female Warfighters participate in combat MOSs, and the associated intake of ORs or restricted rations increases, it will be important to consider folate intake in an effort to meet the dietary requirements necessary to avoid NTDs. Assuring adequate folate intake during the period before conception is of added importance, as the optimal timing of folate supplementation for the avoidance of NTDs occurs between the 4 weeks before and after conception.41 SUMMARY AND RECOMMENDATIONS As detailed in this review, nutrition is a factor that must be considered as women transition into combat roles. Iron, calcium, vitamin D, and folate are nutrients that should receive careful consideration, given the roles of these nutrients in sustaining performance, preventing injury, and protecting against NTDs. The following recommendations should be considered in an effort to optimize the nutritional health of female Warfighters: General — Nutrition education should be provided during IET; nutrients of concern for female Warfighters should be highlighted. — Nutrition standards (MDRIs) should be updated regularly to reflect civilian RDAs, DRIs, and needs specific to military personnel to include the potentially increased nutritional requirements experienced during IET and other physically demanding activities. Iron — Screening for iron status should be considered before the start of IET; women with ID or IDA should be provided with nutrition education and/or supplementation under the care of qualified providers. — Provision of iron-fortified foods (such as snack items) should be considered in efforts to maintain iron status and prevent declines in cognitive and physical performance. — Future studies should consider assessing the iron status of female Warfighters at key time points following IET to include operational deployment. Calcium and Vitamin D — Provision of calcium and vitamin D-fortified foods (such as snack items) should be considered in efforts to prevent stress fracture during IET. — Future studies should consider assessing the relationship between calcium and vitamin D status of female Warfighters and bone health and performance outcomes at key time points following IET to include operational deployment. Folate — Female Warfighters should be provided with adequate (400 μg DFE per day) levels of folate at all times, to include training and operational deployment, because of the necessity of folate before conception for the prevention of NTDs. REFERENCES 1. Army USDot Nutrition Standards and Education . Washington, DC, 2001. Available at http://www.apd.army.mil/pdffiles/r40_25.pdf; accessed April 29, 2015. 2. Council NR (editor): Recommended Dietary Allowances , Ed 10, p 302. Washington, DC, The National Academies Press, 1989. 3. Harvey LJ, Armah CN, Dainty JR, et al.   Impact of menstrual blood loss and diet on iron deficiency among women in the UK. Br J Nutr  2005; 94( 4): 557– 64. Google Scholar CrossRef Search ADS PubMed  4. Dallman PR Biochemical basis for the manifestations of iron deficiency. Annu Rev Nutr  1986; 6: 13– 40. Google Scholar CrossRef Search ADS PubMed  5. Monsen ER Iron nutrition and absorption: dietary factors which impact iron bioavailability. J Am Diet Assoc  1988; 88( 7): 786– 90. Google Scholar PubMed  6. Looker AC, Dallman PR, Carroll MD, Gunter EW, Johnson CL Prevalence of iron deficiency in the United States. JAMA  1997; 277( 12): 973– 6. Google Scholar CrossRef Search ADS PubMed  7. McClung JP, Murray-Kolb LE Iron nutrition and premenopausal women: effects of poor iron status on physical and neuropsychological performance. Annu Rev Nutr  2013; 33: 271– 88. Google Scholar CrossRef Search ADS PubMed  8. Gardner GW, Edgerton VR, Senewiratne B, Barnard RJ, Ohira Y Physical work capacity and metabolic stress in subjects with iron deficiency anemia. Am J Clin Nutr  1977; 30( 6): 910– 7. Google Scholar PubMed  9. Zhu YI, Haas JD Iron depletion without anemia and physical performance in young women. Am J Clin Nutr  1997; 66( 2): 334– 41. Google Scholar PubMed  10. Brownlie TIV, Utermohlen V, Hinton PS, Haas JD Tissue iron deficiency without anemia impairs adaptation in endurance capacity after aerobic training in previously untrained women. Am J Clin Nutr  2004; 79( 3): 437– 43. Google Scholar PubMed  11. Dellavalle DM, Haas JD Iron status is associated with endurance performance and training in female rowers. Med Sci Sports Exerc  2012; 44( 8): 1552– 9. Google Scholar CrossRef Search ADS PubMed  12. Zhu YI, Haas JD Altered metabolic response of iron-depleted nonanemic women during a 15-km time trial. J Appl Physiol 1985  1998; 84( 5): 1768– 75. 13. Brutsaert TD, Hernandez-Cordero S, Rivera J, Viola T, Hughes G, Haas JD Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women. Am J Clin Nutr  2003; 77( 2): 441– 8. Google Scholar PubMed  14. McClung JP, Marchitelli LJ, Friedl KE, Young AJ Prevalence of iron deficiency and iron deficiency anemia among three populations of female military personnel in the US Army. J Am Coll Nutr  2006; 25( 1): 64– 9. Google Scholar CrossRef Search ADS PubMed  15. McClung JP, Karl JP, Cable SJ, Williams KW, Young AJ, Lieberman HR Longitudinal decrements in iron status during military training in female soldiers. Br J Nutr  2009; 102( 4): 605– 9. Google Scholar CrossRef Search ADS PubMed  16. Karl JP, Lieberman HR, Cable SJ, Williams KW, Young AJ, McClung JP Randomized, double-blind, placebo-controlled trial of an iron-fortified food product in female soldiers during military training: relations between iron status, serum hepcidin, and inflammation. Am J Clin Nutr  2010; 92( 1): 93– 100. Google Scholar CrossRef Search ADS PubMed  17. McClung JP, Martini S, Murphy NE, et al.   Effects of a 7-day military training exercise on inflammatory biomarkers, serum hepcidin, and iron status. Nutr J  2013; 12( 1): 141. Google Scholar CrossRef Search ADS PubMed  18. Wilson C, McClung JP, Karl JP, Brothers MD Iron status of military personnel deployed to Afghanistan. Mil Med  2011; 176( 12): 1421– 5. Google Scholar CrossRef Search ADS PubMed  19. Ross AC, Taylor CL, Yaktine AL, Del Valle HB (editors): Dietary Reference Intakes for Calcium and Vitamin D . Washington, DC, National Academic Press, 2011. 20. Pludowski P, Holick MF, Pilz S, et al.   Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality-a review of recent evidence. Autoimmun Rev  2013; 12( 10): 976– 89. Google Scholar CrossRef Search ADS PubMed  21. Lee D, Armed Forces Health Surveillance Center (AFHSC) Stress fractures, active component, U.S. Armed Forces, 2004–2010. MSMR  2011; 18( 5): 8– 11. Google Scholar PubMed  22. Jones BH, Thacker SB, Gilchrist J, Kimsey CDJr, Sosin DM Prevention of lower extremity stress fractures in athletes and soldiers: a systematic review. Epidemiol Rev  2002; 24( 2): 228– 47. Google Scholar CrossRef Search ADS PubMed  23. Knapik J, Montain SJ, McGraw S, Grier T, Ely M, Jones BH Stress fracture risk factors in basic combat training. Int J Sports Med  2012; 33( 11): 940– 6. Google Scholar CrossRef Search ADS PubMed  24. Moran DS, Heled Y, Arbel Y, et al.   Dietary intake and stress fractures among elite male combat recruits. J Int Soc Sports Nutr  2012; 9( 1): 6. Google Scholar CrossRef Search ADS PubMed  25. Burgi AA, Gorham ED, Garland CF, et al.   High serum 25-hydroxyvitamin D is associated with a low incidence of stress fractures. J Bone Miner Res  2011; 26( 10): 2371– 7. Google Scholar CrossRef Search ADS PubMed  26. Ruohola JP, Laaksi I, Ylikomi T, et al.   Association between serum 25(OH)D concentrations and bone stress fractures in Finnish young men. J Bone Miner Res  2006; 21( 9): 1483– 8. Google Scholar CrossRef Search ADS PubMed  27. Lappe J, Cullen D, Haynatzki G, Recker R, Ahlf R, Thompson K Calcium and vitamin d supplementation decreases incidence of stress fractures in female navy recruits. J Bone Miner Res  2008; 23( 5): 741– 9. Google Scholar CrossRef Search ADS PubMed  28. Gaffney-Stomberg E, Lutz L, Rood J, et al.   Calcium and vitamin D supplementation maintains parathyroid hormone and improves bone density during initial military training: a randomized, double-blind, placebo controlled trial. Bone  2014; 68: 46– 56. Google Scholar CrossRef Search ADS PubMed  29. Bartoszewska M, Kamboj M, Patel DR Vitamin D, muscle function, and exercise performance. Pediatr Clin North Am  2010; 57( 3): 849– 61. Google Scholar CrossRef Search ADS PubMed  30. Ceglia L Vitamin D and its role in skeletal muscle. Curr Opin Clin Nutr Metab Care  2009; 12( 6): 628– 33. Google Scholar CrossRef Search ADS PubMed  31. Bischoff-Ferrari HA, Willett WC, Orav EJ, et al.   A pooled analysis of vitamin D dose requirements for fracture prevention. N Engl J Med  2012; 367( 1): 40– 9. Google Scholar CrossRef Search ADS PubMed  32. Bischoff-Ferrari HA, Stahelin HB, Dick W, et al.   Effects of vitamin D and calcium supplementation on falls: a randomized controlled trial. J Bone Miner Res  2003; 18( 2): 343– 51. Google Scholar CrossRef Search ADS PubMed  33. Ward KA, Das G, Berry JL, et al.   Vitamin D status and muscle function in post-menarchal adolescent girls. J Clin Endocrinol Metab  2009; 94( 2): 559– 63. Google Scholar CrossRef Search ADS PubMed  34. Wyon MA, Koutedakis Y, Wolman R, Nevill AM, Allen N The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: a controlled study. J Sci Med Sport  2014; 17( 1): 8– 12. Google Scholar CrossRef Search ADS PubMed  35. Werler MM, Shapiro S, Mitchell AA Periconceptional folic acid exposure and risk of occurrent neural tube defects. JAMA  1993; 269( 10): 1257– 61. Google Scholar CrossRef Search ADS PubMed  36. Daly LE, Kirke PN, Molloy A, Weir DG, Scott JM Folate levels and neural tube defects. Implications for prevention. JAMA  1995; 274( 21): 1698– 702. 37. Shaw GM, Schaffer D, Velie EM, Morland K, Harris JA Periconceptional vitamin use, dietary folate, and the occurrence of neural tube defects. Epidemiology  1995; 6( 3): 219– 26. Google Scholar CrossRef Search ADS PubMed  38. Pitkin RM Folate and neural tube defects. Am J Clin Nutr  2007; 85( 1): 285S– 8S. Google Scholar PubMed  39. Booth CK, Coad RA, Forbes-Ewan CH, Thomson GF, Niro PJ The physiological and psychological effects of combat ration feeding during a 12-day training exercise in the tropics. Mil Med  2003; 168( 1): 63– 70. Google Scholar PubMed  40. Klicka MV, King N, Lavin PT, Askew EW Assessment of dietary intakes of cadets at the US Military Academy at West Point. J Am Coll Nutr  1996; 15( 3): 273– 82. Google Scholar CrossRef Search ADS PubMed  41. Mulinare J, Cordero JF, Erickson JD, Berry RJ Periconceptional use of multivitamins and the occurrence of neural tube defects. JAMA  1988; 260( 21): 3141– 5. Google Scholar CrossRef Search ADS PubMed  Reprint & Copyright © Association of Military Surgeons of the U.S.
TI - Optimizing Performance, Health, and Well-being: Nutritional Factors
JF - Military Medicine
DO - 10.7205/MILMED-D-15-00202
DA - 2016-01-01
UR - https://www.deepdyve.com/lp/oxford-university-press/optimizing-performance-health-and-well-being-nutritional-factors-FERhijfaj2
SP - 86
EP - 91
VL - 181
IS - suppl_1
DP - DeepDyve
ER -