Effects of 30 days of undernutrition on plasma neurotransmitter precursors, other amino acids, and behavior

Negative energy balance during military training: The role of contextual limitations

During multiday training exercises, soldiers almost systematically face a moderate-to-large energy deficit, affecting their body mass and composition and potentially their physical and cognitive performance. Such energy deficits are explained by their inability to increase their energy intake during these highly demanding periods. With the exception of certain scenarios in which rations are voluntarily undersized to maximize the constraints, the energy content of the rations are often sufficient to maintain a neutral energy balance, suggesting that other limitations are responsible for such voluntary and/or spontaneous underconsumption. In this review, the overall aim was to present an overview of the impact of military training on energy balance, a context that stands out by its summation of specific limitations that interfere with energy intake. We first explore the impact of military training on the various components of energy balance (intake and expenditure) and body mass loss. Then, the role of the dimensioning of the rations (total energy content above or below energy expenditure) on energy deficits are addressed. Finally, the potential limitations inherent to military training (training characteristics, food characteristics, timing and context of eating, and the soldiers' attitude) are discussed to identify potential strategies to spontaneously increase energy intake and thus limit the energy deficit.

Metabolomics profile of Japanese female patients with restricting-type anorexia nervosa

In this study, the serum metabolic profiles of 10 female patients with restricting type anorexia nervosa (ANR) were compared to those of 10 age-matched healthy female controls. While the levels of amino acids were lower among the patients than among the controls, the levels of uremic toxins, including p-cresyl sulfate (PCS), indole-3-acetic acid, and phenyl sulfate, were higher in ANR patients. The serum PCS levels correlated positively with the abundance of the Clostridium coccoides group or the C. leptum subgroup in the feces of patients, but not in those of controls. Collectively, these results indicate that the serum metabolic profiles of patients with ANR differ from those of healthy women in terms of both decreased amino acid levels and increased uremic toxins. Gut microbes including C. coccoides or C. leptum may be involved in such an increase in uremic toxins.

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.

Physiological Factors Which Influence Cognitive Performance in Military Personnel

OBJECTIVE

To identify and detail physiological factors that influence cognition in military personnel.

BACKGROUND

Maintenance of cognitive and task performance is important under several scenarios, none more so than in a military context. Personnel are prepared for and trained to tolerate many of the stressors they encounter; however, consideration of stressors typically extends only as far as the physical, psychological, and environmental requirements of a given task. While considering these factors certainly characterizes the broader picture, several physiological states and traits can influence cognition and thus, should also be considered.

METHOD

A systematic review of the electronic databases Medline (PubMed), EMBASE (Scopus), PsycINFO, and Web of Science was conducted from inception up to January 2019. Eligibility criteria included current military personnel, an outcome of cognition, and the assessment of a physiological factor.

RESULTS

The search returned 60,564 records, of which 60 were included in the review. Eleven studies examined the impact of demographic factors on cognition, 16 examined fatigue, 10 investigated nutrition, and 24 the impact of biological factors on cognitive performance.

CONCLUSION

Factors identified as having a positive impact on cognition include aerobic fitness, nutritional supplementation, and visual acuity. In contrast, factors identified as having a negative impact include fatigue arising from sustained operations, dehydration, undernutrition, and an exaggerated physiological stress response to a cognitive task or a stressor. A further subset of these factors was considered modifiable.

APPLICATION

The modifiable factors identified provide avenues for training and preparation to enhance cognition in ways previously unconsidered.

Two days of calorie deprivation impairs high level cognitive processes, mood, and self-reported exertion during aerobic exercise: A randomized double-blind, placebo-controlled study

Military personnel and emergency responders perform cognitively-demanding tasks during periods of sustained physical exertion and limited caloric intake. Cognitive function is preserved during short-term caloric restriction, but it is unclear if preservation extends to combined caloric restriction and physical exertion. According to the "reticular-activating hypofrontality" model, vigorous exertion impairs prefrontal cortex activity and associated functions. This double-blind, placebo-controlled, crossover study examined cognitive function during sustained exertion while volunteers were calorically-deprived. Twenty-three volunteers were calorie-depleted for two days on one occasion and fully-fed on another. They completed intermittent bouts of exercise at 40-65% VO_2peak while prefrontal cortex-dependent tasks of cognitive control, mood, and perceived exertion were assessed. Calorie deprivation impaired accuracy on the task-switching task of set-shifting (p < .01) and decreased sensitivity on the go/no-go task of response inhibition (p < .05). Calorie deprivation did not affect risk taking on the Rogers risk task. During exercise, calorie deprivation, particularly on day 2, increased perceived exertion (p < .05) and impaired mood states of tension, depression, anger, vigor, fatigue, and confusion (all p < .01). Physical exertion during severe calorie deprivation impairs cognitive control, mood, and self-rated exertion. Reallocation of cerebral metabolic resources from the prefrontal cortex to structures supporting movement may explain these deficits.

Body weight and body composition changes during military training and deployment involving the use of combat rations: a systematic literature review

Dismounted military personnel operate in physically and psychologically demanding environments, with energy intake from combat rations often falling short of their requirements, leading to reductions in body weight and changes in body composition, which can impact both their health and performance. This review systematically investigated the effects of the continual use of combat rations for periods of 3–40 d on body weight and/or body composition in military personnel engaged in training or deployment. In all, ten databases were searched from their inception until October 2016. Outcome data were described narratively, with studies assessed for quality and risk of bias. A total of thirty studies undertaken over 3–34 d were included. Studies were rated positive, neutral or negative in quality according to the Academy of Nutrition and Dietetics Quality Checklist, with many at risk of bias. Reductions in mean body weight varied, from a negligible decrease of 0·1 % during 8 d of combat training to a substantial decrease of approximately 8·3 % during 12 d of energy restriction during a US Army Ranger course. Decreases in fat mass, fat-free mass and percentage body fat were also reported. There is thus evidence that the continual use of combat rations for periods of 3–34 d results in reductions in body weight and body composition changes which, in some scenarios, may impact on the performance of troops. Body weight and composition should be routinely monitored before and after field activities, and at more regular intervals depending on the length, intensity and type of activity being undertaken.

Malnutrition and brain development: an analysis of the effects of inadequate diet during different stages of life in rat

Protein malnutrition or undernutrition can result in abnormal development of the brain. Depending on type, age at onset and duration, different structural and functional deficits can be observed. In the present review, we discuss the neuroanatomical, behavioral, neurochemical and oxidative status changes associated with protein malnutrition or undernutrition at different ages during prenatal and immediately postnatal periods as well as in adult rat. Analysis of all data suggests that protein malnutrition as well as undernutrition induced impaired learning and retention when imposed during the immediately postnatal period and in adulthood, whereas hyperactivity including increased impulsiveness and greater reactivity to aversive stimuli occurred when malnutrition or undernutrition was imposed either pre or postnatally. This general state of hyperreactivity may be linked essentially to an alteration in dopaminergic system. Hence, the present review shows that in spite of the attention devoted in the literature to prenatal effects, cognitive deficits are more serious following malnutrition or undernutrition after birth. We thus clearly establish a special vulnerability to malnutrition after weaning in rats.

A low-protein diet alters rat behavior and neurotransmission in normothermic and hyperthermic environments

Dietary protein contains amino acids used in the brain for synthesis of neurotransmitters. Although information on pre- and post-natal exposure to low-protein diets in rodents is available, little is known about effects of such diets on adult animals. Therefore, the behavioral and neurochemical consequences of exposure to a brief (11 days), low (4%)-protein diet in animals exposed to normothermic and hyperthermic test conditions were examined. In separate groups of animals, the Porsolt Swim test and elevated plus maze were administered. These tasks are sensitive to nutritional and/or environmental manipulations. In other groups of rats exposed to the same dietary and environmental conditions, dopamine, norepinephrine, epinephrine, and serotonin in the striatum were assessed using microdialysis. In the Porsolt swim test, which assesses coping behavior, performance was impaired under normothermic and hyperthermic conditions in animals on the low-protein diet. Performance on the plus maze, a measure of exploration and anxiety, was altered in the hyperthermic condition by low protein, with the diet increasing exploration. Microdialysis detected increased norepinephrine in the striatum of hyperthermic animals on the low-protein diet. This study demonstrates that changes in stress-related behaviors of adult animals occur following brief exposure to low-protein diets.

Plasma amino acid concentrations in patients with amnestic mild cognitive impairment or Alzheimer disease

BACKGROUND

Plasma concentrations of several amino acids may affect the availability of important neurotransmitter precursors in the brain. Abnormalities in the plasma amino acid profile have been reported in elderly persons with cognitive impairment, but no data exist for the prodromal phase of Alzheimer disease (AD), which is characterized by amnestic mild cognitive impairment (aMCI).

OBJECTIVE

The objective was to investigate whether the plasma amino acid profiles of elderly patients with aMCI or AD are abnormal.

DESIGN

The plasma amino acid profile was assessed in 29 cognitively normal control subjects (age: 86.7 +/- 5.9 y), 21 patients with aMCI (age: 84.9 +/- 7.0 y), and 51 patients with AD (age: 86.7 +/- 5.4 y). The participants were from the University of Bologna Research Center for Physiopathology of Aging, Italy.

RESULTS

Higher plasma concentrations of the aromatic amino acid phenylalanine were found in the aMCI (68 micromol/L; 95% CI: 63, 73) and AD (62 micromol/L; 95% CI: 59, 65) patients than in the control subjects (54 micromol/L; 95% CI: 48, 61; P < 0.05). The ratio of arginine to other basic amino acids was also higher in the aMCI (0.31 +/- 0.04) and AD (0.27 +/- 0.08) patients than in the control subjects (0.21 +/- 0.05; P < 0.05). Adjustment for differences in body composition, serum vitamin B-12 concentrations, and serum folate concentrations did not significantly affect the results.

CONCLUSIONS

The plasma amino acid profiles of elderly patients with aMCI or AD show abnormalities in aromatic and basic amino acids that potentially affect neurotransmitter biosynthesis.

Postexercise protein supplementation improves health and muscle soreness during basic military training in marine recruits

Elevated postexercise amino acid availability has been demonstrated to enhance muscle protein synthesis acutely, but the long-term impact of postexercise protein supplementation on variables such as health, muscle soreness, and function are unclear. Healthy male US Marine recruits from six platoons (US Marine Corps Base, Parris Island, SC; n = 387; 18.9 ± 0.1 yr, 74.7 ± 1.1 kg, 13.8 ± 0.4% body fat) were randomly assigned to three treatments within each platoon. Nutrients supplemented immediately postexercise during the 54-day basic training were either placebo (0 g carbohydrate, 0 g protein, 0 g fat), control (8, 0, 3), or protein supplement (8, 10, 3). Subjects and observers making measurements and data analysis were blinded to subject groupings. Compared with placebo and control groups, the protein-supplemented group had an average of 33% fewer total medical visits, 28% fewer visits due to bacterial/viral infections, 37% fewer visits due to muscle/joint problems, and 83% fewer visits due to heat exhaustion. Recruits experiencing heat exhaustion had greater body mass, lean, fat, and water losses. Muscle soreness immediately postexercise was reduced by protein supplementation vs. placebo and control groups on both days 34 and 54. Postexercise protein supplementation may not only enhance muscle protein deposition but it also has significant potential to positively impact health, muscle soreness, and tissue hydration during prolonged intense exercise training, suggesting a potential therapeutic approach for the prevention of health problems in severely stressed exercising populations.

Effects of 30 days of undernutrition on reaction time, moods, and symptoms

Few modern studies have addressed the effects of undernutrition on the behavior of healthy individuals. This study, conducted as part of a test of a nutritionally balanced but calorie-deficient experimental ratio, examined the effects of 30 days of undernutrition on healthy, physically active soldiers. Tests of reaction time and standardized questionnaires assessing mood and symptom parameters (known to be sensitive to nutritional and other factors) were administered prior to and following a 30-day field exercise. During the exercise, 17 soldiers consumed a calorie-deficient, lightweight ration (LW group, 1946 kcal/day) and 17 consumed a calorie-adequate control ration (FN group, 2782 kcal/day). Mean energy expenditure for both groups was 3200-3300 kcal/day. There were no differences between the two diet groups on any of the measures of reaction time, mood, or symptoms after 30 days of ration consumption. Additionally, there were no adverse changes in reaction time performance from pre- to post-testing. Adverse changes in moods and symptoms were seen in both groups at the conclusion of the test, possibly because of the rigors of living in the field for an extended period of time. This study demonstrates that, in healthy individuals, various aspects of mental performance, mood, and symptoms are not affected by up to 30 days of moderate undernutrition.