Supplementing an energy adequate, higher protein diet with protein does not enhance fat-free mass restoration after short-term severe negative energy balance.

Negative energy balance during military operations can be severe and result in significant reductions in fat-free mass (FFM). Consuming supplemental high-quality protein following such military operations may accelerate restoration of FFM. Body composition (dual-energy X-ray absorptiometry) and whole body protein turnover (single-pool [15N]alanine method) were determined before (PRE) and after 7 days (POST) of severe negative energy balance during military training in 63 male US Marines (means ± SD, 25 ± 3 yr, 84 ± 9 kg). After POST measures were collected, volunteers were randomized to receive higher protein (HIGH: 1,103 kcal/day, 133 g protein/day), moderate protein (MOD: 974 kcal/day, 84 g protein/day), or carbohydrate-based low protein control (CON: 1,042 kcal/day, 7 g protein/day) supplements, in addition to a self-selected, ad libitum diet, for the 27-day intervention (REFED). Measurements were repeated POST-REFED. POST total body mass (TBM; -5.8 ± 1.0 kg, -7.0%), FFM (-3.1 ± 1.6 kg, -4.7%), and net protein balance (-1.7 ± 1.1 g protein·kg-1·day-1) were lower and proteolysis (1.1 ± 1.9 g protein·kg-1·day-1) was higher compared with PRE (P < 0.05). Self-selected, ad libitum dietary intake during REFED was similar between groups (3,507 ± 730 kcal/day, 2.0 ± 0.5 g protein·kg-1·day-1). However, diets differed by protein intake due to supplementation (CON: 2.0 ± 0.4, MOD: 3.2 ± 0.7, and HIGH: 3.5 ± 0.7 g·kg-1·day-1; P < 0.05) but not total energy (4,498 ± 725 kcal/day). All volunteers, independent of group assignment, achieved positive net protein balance (0.4 ± 1.0 g protein·kg-1·day-1) and gained TBM (5.9 ± 1.7 kg, 7.8%) and FFM (3.6 ± 1.8 kg, 5.7%) POST-REFED compared with POST (P < 0.05). Supplementing ad libitum, energy-adequate, higher protein diets with additional protein may not be necessary to restore FFM after short-term severe negative energy balance.NEW & NOTEWORTHY This article demonstrates 1) the majority of physiological decrements incurred during military training (e.g., total and fat-free mass loss), with the exception of net protein balance, resolve and return to pretraining values after 27 days and 2) protein supplementation, in addition to an ad libitum, higher protein (~2.0 g·kg-1·day-1), energy adequate diet, is not necessary to restore fat-free mass following short-term severe negative energy balance.

The effects of ginseng, ephedrine, and caffeine on cognitive performance, mood and energy.

A variety of claims regarding the purported energy-enhancing properties of nutritional supplements and food constituents have recently been made. It appears that the supplements most frequently associated with such assertions are ginseng, ephedrine, and caffeine. Claims of increased energy are difficult to evaluate objectively because their meaning is not usually defined or specified. Often it is not clear whether the claims refer to physical or mental energy or both. Furthermore, an agreed upon scientific definition of either physical or mental energy enhancement does not exist. In spite of obvious differences in what the term physical energy, as opposed to mental energy implies, there is no clear scientific consensus on whether there is a difference between the two types of energy. Because the substances in question have been anecdotally associated with improvements in both physical and mental performance, their effects on both functions will be discussed, but with an emphasis placed on cognitive function and mood. Of the three substances discussed, caffeine's effects on cognitive and physical function, mood, and energy are best understood. It is clear that this food/drug enhances these functions when administered in moderate doses. Ephedrine may also enhance certain physical and mental functions related to "energy," but the evidence that ginseng has such properties is exceedingly weak.

Tyrosine improves behavioral and neurochemical deficits caused by cold exposure.

The effects of acute cold stress were assessed behaviorally and neurochemically. The norepinephrine (NE) precursor, tyrosine (TYR), the catecholamine-releasing compound, amphetamine (AMPH), and the adrenoceptor agonist, phenylpropanolamine (PPA), were administered systemically either alone or in conjunction with TYR 30 min prior to cold exposure. All three sympathomimetic treatments dose-dependently improved performance in a forced swim test following hypothermia (T(c)=30 degrees C). AMPH/TYR or PPA/TYR combinations further improved performance vs. either agent given alone. Microdialysis showed elevated hippocampal NE concentrations in response to hypothermia. TYR further elevated NE concentration in cold/restrained rats vs. saline (SAL)-treated controls. These results suggest that sympathomimetic agents, including the nutrient TYR, which enhance noradrenergic function, improve performance in animals acutely stressed by hypothermia.

Antisense oligonucleotide sequences targeting the muscarinic type 2 acetylcholine receptor enhance performance in the Morris water maze.

Blocking autoinhibitory muscarinic type 2 (m2) acetylcholine receptors in the central nervous system may increase the release of acetylcholine and improve learning and memory. Antisense oligonucleotides (OGNs) complementary to m2 receptor mRNA were synthesized and evaluated for their efficacy at decreasing receptor number and reversing deficits in a cognitive task. Three antisense OGNs, which decreased m2 receptor binding in NG108-15 cells, were continuously infused into the lateral cerebral ventricle of rats for 6 days at a rate of 0.5 micro1/h and a daily dose of 72 microg. Performance in the Morris water maze was compared to groups receiving control OGNs or vehicle alone. Decrements induced by 0.2 mg/kg of scopolamine i.p. were significantly reversed by 2 of the 3 antisense OGNs. Use of antisense OGNs targeting the m2 receptor may be a new strategy to increase cholinergic neurotransmission and improve learning and memory.

The effects of choline supplementation on physical performance.

It has been reported that plasma choline levels decrease following certain types of strenuous exercise. Preliminary findings also suggest that a drop in plasma choline may limit physical performance, while choline supplementation may delay fatigue during prolonged efforts. A double-blind crossover design was used to determine the relationship between plasma choline and performance during and after 4 hr of strenuous exercise. Volunteers (N = 14) received either a placebo or treatment beverage (8.425 g choline citrate) prior to and midway through a 4-hr load carriage treadmill exercise (3% grade at 5.6 km/h 3 20 km) carrying a total load of 34.1 kg. Following the treadmill test, run time-to-exhaustion and squat tests were performed, and perceived exertion, plasma choline, glycerophosphocholine, and phosphatidylcholine were measured. Plasma choline levels increased 128% after the run-to-exhaustion with the choline supplemented beverage but remained unchanged with the placebo beverage. No significant effects were seen with choline supplementation on any outcome performance measure. Consequently, soldiers conditioned to carry heavy loads over long distances do not deplete plasma choline as a result of a prolonged exhaustive exercise under a placebo beverage, nor do they benefit from choline supplementation to delay fatigue under the same conditions.

Influence of a carbohydrate drink on nutritional status, body composition and mood during desert training.

BACKGROUND: Nutritional intake by military personnel is typically inadequate during field exercises, potentially compromising health and performance. HYPOTHESIS: Drinking a supplemental carbohydrate (CHO) beverage will increase total caloric intake and maintain nutritional status during military training in the desert. METHODS: A total of 63 volunteers were randomly assigned to one of two groups to receive either a CHO or placebo beverage with military rations during an 11-d desert field exercise. Fluid intake was ad libitum and adequate rations were provided. Blood samples were collected twice to assess nutritional status, and nutrient intake was determined with consumption data. Mood state was examined by questionnaire. RESULTS: Energy intake was significantly higher in the CHO group (3050 kcal x d(-1) vs. 2631 kcal x d(-1)), with additional CHO from the beverage providing energy with some compensation by reduced fat and protein intake. Intakes of energy, folacin, calcium, magnesium, iron, and zinc in both groups were inadequate, with intakes significantly lower (p<0.05) for calcium, magnesium, and zinc in the CHO beverage group. Blood parameters of nutritional status remained within normal ranges with no differences between groups, but significant decreases were seen in pre-albumin. No changes in mood were seen during the training, nor after exposure to desert conditions. CONCLUSIONS: The operational ration supplemented with a CHO beverage significantly increases CHO and energy intakes compared with standard rations and maintains nutritional status for short exercises. Fortification with micronutrients most at risk for deficient intake from foods may be needed for longer deployments.

Pilot study on the effect of hyperimmune egg protein on elevated cholesterol levels and cardiovascular risk factors.

Coronary heart disease is the leading cause of death in the United States, accounting for almost half of all deaths. Animal studies have suggested that the daily addition of "hyperimmune egg" to one's diet might reduce the risk of cardiovascular disease. Military personnel with initial total cholesterol levels higher than 180 mg/dl were randomly enrolled in a 26-week double-blind study of a drink containing a hyperimmune egg protein. Subjects were randomly assigned to three groups: control (no drink); placebo (drink without egg); and active (drink combined with hyperimmune egg). Throughout the study this physically fit group maintained a program of strenuous exercise and participated in a dietary education program intended to reduce fat and cholesterol intake. At the end of the trial, total cholesterol levels of the control and placebo groups had increased, whereas the group that consumed the drink with hyperimmune egg showed no significant change in total cholesterol. The ratio of total cholesterol to high-density lipoproteins and the apolipoprotein B level increased in both control and placebo groups but remained essentially unchanged in the group consuming hyperimmune egg. Triglyceride and apolipoprotein A-I values did not change significantly in any of the groups. These findings suggest that hyperimmune egg may beneficially modify the regulation of serum lipoprotein levels and thereby reduce the possibility of cardiovascular diseases.

Spatial memory under acute cold and restraint stress.

This study examined spatial memory as measured by radial arm maze (RAM) performance after exposure to two stress conditions and a normothermic-unrestrained control condition. Male Fischer 344 rats were trained on the win-shift RAM procedure for 7 days, by which time they achieved asymptotic performance. The next day, rats in the two stress groups were exposed to 15 min of restraint in either 37 degrees C water (normothermic-restraint) or in 20 degrees C water (cold-restraint). Rats were then allowed 40 min in a dry cage before being tested in the RAM. Performance was measured using the following dependent variables: number of correct out of the first eight choices, total number of choices, and time per choice. There were statistically significant effects of stress on all these variables; performance decrements were observed in both stress conditions relative to the normothermic-unrestrained condition. Normothermic-restrained rats displayed less impairment than cold-restrained rats on the stress day. Performance of normothermic-restrained rats returned to baseline levels the day after stress, whereas performance for the cold-restrained rats typically did not. This study demonstrates that: 1) restraint and cold stress impair performance on a memory task; and 2) impairment extent is related to stress severity. One of the mechanisms responsible for the observed behavioral deficits under cold stress may involve altered cholinergic function, because we previously demonstrated that hippocampal acetylcholine levels also decrease in relation to the severity of cold stress.

Elevation-dependent symptom, mood, and performance changes produced by exposure to hypobaric hypoxia.

Altitude exposures above 3,000 m produce changes in symptoms, moods, and cognitive/motor performance of unacclimatized individuals and should produce graded effects on these parameters as elevation and duration are increased. This study examined effects on these parameters as a function of altitude level and duration of exposure by administering standardized tests from 1 to 3 times to 23 males in an altitude chamber during 4.5-hour exposures to 3 levels of hypobaric hypoxia: 500 m, 4,200 m, and 4,700 m. Exposure to altitude significantly affected symptoms, moods, and performance in an elevation-dependent fashion. Adverse changes increased with higher altitudes (all measures were affected at 4,700 m, whereas only some were at 4,200 m) and usually with longer durations. Therefore, specific aspects of symptoms, moods, and performance are significantly degraded after only a few hours of exposure to hypobaric hypoxia, and the severity of the effects dramatically increases when testing is conducted at 4,700 m compared to 4,200 m.

Caffeine's Effects on Performance and Mood are Independent of Age and Gender.

The purpose of this study was to determine if there were age or gender specific effects of caffeine, as measured by cognitive tasks and mood assessments known to be sensitive to caffeine. The subjects were healthy, non-smoking volunteers between the ages of 18 and 30 (6 male and 6 female), and over the age of 60 (6 male and 6 female). Only low and moderate consumers of caffeine (daily intake < 400 mg) were enrolled in the double-blind, placebo controlled, crossover design. The order of caffeine dosing (placebo, 64, 128, and 256 mg) was counterbalanced by use of a complex Latin Square sequence of administration. Analysis of the data from all measures indicated that the effects of caffeine were no different in either males or females, or in the young or elderly volunteers. A significant dose-dependent improvement in performance of all subjects was observed in a modified version of the Wilkinson Auditory Vigilance Test. Additionally, significant dose-dependent improvements in mood state were observed in all subjects as assessed by the Profile of Mood States, Multiple Affect Adjective Check List, and The Caffeine Analog Scales. The results of this study suggest that the performance and mood enhancing effects of caffeine are neither age nor gender specific.

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.

Effects of sleeping in a chemical protective mask on sleep quality and cognitive performance.

PURPOSE: We wanted to determine whether sleep is disrupted when soldiers sleep in a new chemical protective mask, the M40. Sleep quantity and quality, extent of protection provided by the mask during sleep, and next day performance were assessed. METHOD: After several days of training, 9 male soldiers slept with and without the M40 mask on four occasions. RESULTS: Soldiers were able to tolerate the mask for most or all of the night. However, sleep, as assessed by wrist-worn activity monitors, was significantly disturbed. Minutes (mean +/- SEM) of waking significantly increased, from 25 +/- 2.1 to 86 +/- 8.5 per night (p < 0.001), and number of awakenings rose from 8 +/- 0.6 to 20 +/- 0.9 (p < 0.0001). Soldiers reported that it took longer and was more difficult to fall asleep when wearing the mask. Errors on a choice reaction time task increased significantly and subjects reported greater fatigue and sleepiness the day after sleeping in the mask. Protection provided by the masks varied substantially among subjects and declined over the course of the study. Some soldiers were protected throughout the night but others were only protected intermittently. CONCLUSION: We conclude that sleeping in the chemical protective mask should only be done when necessary, given the adverse effects on sleep and daytime function, as well as the variability of protection, of the mask.

Melatonin efficacy in aviation missions requiring rapid deployment and night operations.

BACKGROUND: The rapid deployment of Army aviation personnel across time zones, combined with missions beginning immediately upon arrival, results in desynchronization of physiological and cognitive performance rhythms. Implementation of effective countermeasures enhances safety, health, well-being, and mission completion. The naturally occurring hormone melatonin has been suggested as an effective counter measure for jet lag and shift lag because of its influence on the human circadian timing system and its hypnotic properties. METHODS: The efficacy of melatonin (10 mg) in maintaining stable sleep/wake cycles of Army aircrews was tested during a training mission involving rapid deployment to the Middle East and night operations. Cognitive performance was tested before and after travel; activity rhythms were recorded continuously for 13 d. RESULTS: Melatonin treatment advanced both bedtimes and rise times (2-3 h) and maintained sleep durations between 7-8 h. Placebo treatment was mostly associated with longer advances in rise times than bedtimes resulting in shorter sleep durations (5-7 h). Upon awakening, the melatonin group exhibited significantly fewer errors (mean: 7.45) than the placebo group (mean: 14.50) in a dual-task vigilance test. CONCLUSION: Melatonin can be a useful treatment for the prevention of sleep disruptions and cognitive degradation, even in uncontrolled sleeping environments characteristic of military deployments.

Citicoline improves verbal memory in aging.

OBJECTIVE: To test the verbal memory of older volunteers given citicoline. DESIGN: A randomized, double-blind, placebo-controlled, parallel group design was employed in the initial study. After data analysis, a subgroup was identified whose members had relatively inefficient memories. These subjects were recruited for a second study that used a crossover design. The subjects took either placebo or citicoline, 1000 mg/d, for 3 months in the initial study. In the crossover study, subjects took both placebo and citicoline, 2000 mg/d, each for 2 months. SUBJECTS: The subjects were 47 female and 48 male volunteers 50 to 85 years old. They were screened for dementia, memory disorders, and other neurological problems. Of the subjects with relatively inefficient memories, 32 participated in the crossover study. MAIN OUTCOME MEASURE: Verbal memory was tested at each study visit using a logical memory passage. Plasma choline concentrations were measured at baseline; at days 30, 60, and 90 in the initial study; and at day 60 of each treatment condition in the crossover study. Plasma choline concentrations and memory scores were analyzed using repeated-measures analysis of variance and covariance, followed by planned comparisons when appropriate. RESULTS: In the initial study, citicoline therapy improved delayed recall on logical memory only for the subjects with relatively inefficient memories. In the crossover study, the higher dosage of citicoline was clearly associated with improved immediate and delayed logical memory. CONCLUSIONS: Citicoline therapy improved verbal memory functioning in older individuals with relatively inefficient memories. Citicoline may prove effective in treating age-related cognitive decline that may be the precursor of dementia.

Tyrosine administration prevents hypoxia-induced decrements in learning and memory.

Exposure to hypobaric hypoxia rapidly produces decrements in learning and memory. Tyrosine, a neurotransmitter precursor, has beneficial behavioral effects when administered to animals and humans exposed to various acute stressors. To determine whether tyrosine would protect rats from the adverse effects of hypobaric hypoxia on spatial reference and working memory, it was administered to 27 male Fischer 344 rats tested in the Morris water maze. Rats were tested starting at 2 and 6 h of an 8 h exposure to a simulated altitude of 5950 m (19,500 ft) or sea level. Tyrosine or placebo was administered 1/2 h prior to each testing session (400 mg/kg, IP). Altitude exposure significantly increased working memory escape latency; treatment with tyrosine reversed this decrement. There was no effect of altitude or tyrosine on reference memory. There were also no treatment-related differences in performance when animals were tested the next day at sea level. The beneficial effects of tyrosine on working memory performance may be due to a direct effect of tyrosine on memory, alleviation of a hypoxia-induced retardation of learning, or to other central or peripheral effects of this dietary catecholamine precursor.

Morphological alterations in the hippocampus following hypobaric hypoxia.

1. The morphological consequences of hypobaric hypoxia, exposure to reduced pressure atmospheres, were examined in the hippocampus of male Fischer 344 rats. Severe chronic hypoxia can produce permanent neuronal damage with hippocampal structures being especially vulnerable. 2. Hippocampal morphology was studied using histological observations after a 4 day exposure to sea level, 3500 m, or 6400 m. Two groups tested at 6400 m were sacrificed at different intervals following exposure, 72 and 144 h, to examine the effect of post-exposure time on neuronal damage. 3. Histological damage was observed in rats' brains following exposure to altitude, with cell degeneration and death increasing as altitude increased. In addition, it was found that the longer the time following exposure before sacrifice, the more noticeable the damage, suggesting delayed neurotoxicity. Increases in the number of damaged cells following altitude were significant for the CA3 region of one 6400 m group; however, other differences did not reach statistical significance. Rats exposed to altitude for 4 days ate less and lost significantly more weight than did animals at sea level. 4. It appears that 4 days of exposure to altitudes less than or equal to 6400 m does produce changes in the CA3 subfield, but the damage is different than that seen with other models of non-transient ischemia.

Effects of M2 antagonists on in vivo hippocampal acetylcholine levels.

There is evidence that muscarinic receptors of the M2 subtype are presynaptic autoreceptors that modify the release of acetylcholine (ACh) through a negative feedback mechanism. Blocking these receptors by selective antagonists may therefore lead to increased ACh release. This in vivo microdialysis study examined the effects of three M2 antagonists, AF-DX 116, AF-DX 384, and AQ-RA 741, on hippocampal cholinergic neurotransmission. Drug (2, 4, 8, or 16 microM) or vehicle (Ringer's solution) was perfused via a microdialysis probe into the CA1 hippocampal region of conscious male Fischer 344 rats. Levels of ACh and choline were assessed by HPLC-EC. When the dose was expressed in K1 multiples, all drugs (except AQ-RA 741 at the two highest concentrations) were found to be on the same linear dose-response curve. Choline levels were not affected by drug administration. All three compounds elevated ACh levels in a similar K1-normalized dose-response fashion, strongly supporting the concept that the proposed presynaptic mechanism of action is indeed based on the same M2 receptor. Such elevations of ACh may not only improve performance on memory tasks, but may also have therapeutic advantages in conditions of cholinergic hypofunction, such as Alzheimer's disease.

L-tyrosine ameliorates some effects of lower body negative pressure stress.

Tyrosine, a large neutral amino acid normally present in protein foods, is the precursor of the catecholamine neurotransmitters dopamine, norepinephrine, and epinephrine. Animal studies indicate that systemic administration of tyrosine in pharmacological quantities can reduce physiological and behavioral decrements induced by highly stressful conditions. The current study was designed to test the effects of tyrosine (100 mg/kg of body weight) on humans exposed to cardiovascular stress. Twenty participants were exposed to two Lower Body Negative Pressure (LBNP) sessions (-50 mm Hg for a maximum of 30 min) during each of two testing sessions of a repeated measure double-blind placebo-controlled study. The detected effects of tyrosine include an overall increase in pulse pressure (LBNP typically reduces pulse pressure) and an increase in auditory event related potential amplitude (P300-N300), an electro-physiological correlate of attention which may indicate enhanced cognitive activation.

Hypobaric hypoxia impairs spatial memory in an elevation-dependent fashion.

The effects of various levels of hypobaric hypoxia, exposure to reduced atmospheric pressure, on spatial memory in rats were examined. Hypobaric hypoxia simulates high altitude conditions where substantial deficits in human cognitive performance occur. However, few studies have measured cognitive changes in animals during exposure to this type of hypoxia. Male Fischer 344 rats were tested in the learning set version of the Morris water maze, a test known to assess spatial memory. Rats were tested at 2 and 6 hours while exposed to a range of simulated altitudes: sea level, 5500 m, 5950 m, and 6400 m. Altitude exposures at 5950 or 6400 m decreased both reference and working memory performance, as demonstrated by latency, distance, and speed measures, in an elevation-dependent fashion. During sea level testing on the day following hypobaric exposure, decrements in reference memory were still observed on all dependent measures, but only speed was impaired on the working memory task. These results agree with human studies that demonstrate elevation-dependent impairments in spatial memory performance during exposure to hypobaric hypoxia. The deficits may be attributable to changes in hippocampal cholinergic function.

Effects of caffeine or diphenhydramine on visual vigilance.

The effects of two drugs having opposite effects on the central nervous system were investigated using a newly developed visual vigilance task. Twenty-four male volunteers (median age = 20) performed the task on three separate occasions; after consuming placebo, caffeine (200 mg), or diphenhydramine (25 mg), in a double-blind, Latin Square design. At least 2 days intervened between drug administrations. Caffeine use was restricted for 10 h and smoking for 3 h before drug administration. When compared with placebo, caffeine significantly increased the number of correct responses and decreased response times, whereas diphenhydramine decreased the number of correct responses and increased response times. Low habitual consumers of caffeine (< 100 mg/day) and non-smokers had more correct responses than did high habitual caffeine consumers (> 100 mg/day) and smokers, but only in the placebo condition. Non-smokers had faster response times than smokers only in the placebo condition. Both caffeine and diphenhydramine altered certain aspects of mood.