E. Wayne Askew

Efficacy and Safety of Protein Supplements for U.S. Armed Forces Personnel: Consensus Statement

To provide evidence-based guidance regarding the efficacy and safety of dietary protein supplement (PS) use by members of the U.S. Armed Forces, a panel of internationally recognized experts in the fields of protein metabolism and dietary supplement research was convened by the Department of Defense Center Alliance for Dietary Supplement Research and the U.S. Army Medical Research and Material Command. To develop a consensus statement, potential benefits, risks, and strategies to optimize military performance through PS use were considered in the context of specific warfighter populations and occupational demands. To maintain muscle mass, strength, and performance during periods of substantial metabolic demand and concomitant negative energy balance the panel recommended that warfighters consume 1.5-2.0 g · kg(-1) · d(-1) of protein. However, if metabolic demand is low, such as in garrison, protein intake should equal the current Military Dietary Reference Intake (0.8-1.5 g · kg(-1) · d(-1)). Although PS use generally appears to be safe for healthy adults, warfighters should be educated on PS quality, given quality-control and contamination concerns with commercial dietary supplements. To achieve recommended protein intakes, the panel strongly urges consumption of high-quality protein-containing whole foods. However, when impractical, the use of PSs (20-25 g per serving or 0.25-0.3 g · kg(-1) per meal), particularly after periods of strenuous physical activity (e.g., military training, combat patrols, and exercise), is acceptable. The committee acknowledges the need for further study of protein requirements for extreme, military-specific environmental conditions and whether unique metabolic stressors associated with military service alter protein requirements for aging warfighters.

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.

A comparison of subjective and objective measures of physical exertion

Abstract Better methods are needed to improve validity and reliability of physical activity (PA) assessment instruments. The purpose of this study was to compare individuals Borgs Rate of Perceived Exertion (RPE) scores to GT1M ActiGraph accelerometer output, with the aim to better understand estimates of perceived exertion for exercise prescription. Adults were recruited (n = 117) from Utah, with 43.1% males (n = 50), and most (53.1%) self-reporting regular exercise. Participants performed three indoor laps of increasing intensity, ranging from walking to running, and immediately completed a RPE form. A subsample was mailed the same RPE survey 6–8 weeks later to compare differences from their initial responses. Individual accelerometer data was compared to RPE levels from validated metabolic equivalents (METs). There were significant differences between the RPE ratings and the accelerometer output overall for gender (χ2 = 10.9, P = 0.004), and exercise status (χ2 = 15.5, P < 0.001). The odds of underestimating RPE for an exerciser were 3.67 times greater than a non-exerciser (95% CI = 1.48, 9.11). The subsample also underestimated RPE after the time lapse (Z = −2.324, P = 0.020). Overall, the RPE proved to be a useful tool for most individuals and could be used in individualised exercise prescription, although women may overestimate, and regular exercisers may underestimate exertion.

Changes in protein synthesis in rats in response to endurance training

Abstract Experiments were conducted to investigate the influence of endurance exercise training on protein synthesis in skeletal muscle, heart, and liver. Training decreased incorporation of [ 14 C]-leucine into proteins of the stromal fraction of muscle but there was no change in amino acid incorporation into proteins of the sarcoplasmic and myofibrillar fractions. Incorporation of [ 14 C]-leucine into the protein of heart, liver, and plasma was depressed in trained rats compared to untrained rats. The specific radioactivity of [ 14 C]-leucine was similar in tissues of trained and untrained rats and thus the depressed amino acid incorporation represents a decrease in the rate of protein synthesis. These observations demonstrate that the adaptation of muscle protein metabolism to endurance training is quite different than the alterations during work-induced hypertrophy of muscle. The difference in adaptation probably relates to the functional differences between the types of exercise. However depression of protein synthesis in trained rats is a general effect in several tissues and not an effect localized in muscle tissue.

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

Abstract As part of a 30-day field exercise, 17 soldiers consumed a calorie-deficient, lightweight ration (1946 kcal/day) while 17 others consumed a calorie-adequate control ration (2782 kcal/day). Mean energy expenditure for both groups was 3200 to 3300 kcal/day. Plasma amino acid levels were assessed at the start, after 14 days, and at the completion of the study. Behavioral testing was conducted at the start and completion of the study. Alanine, which is used for gluconeogenesis, fell from 389 to 323 nmol/mL over the trial among those who consumed the calorie-deficient diet, whereas it increased in the control group. Plasma tyrosine also fell significantly, from 70 to 52 nmol/mL, as did tryptophan (from 62 to 55 nmol/mL) in the calorie deficient group. The ratio of tyrosine to other large neutral amino acids, an indicator of tyrosine transport to the brain, also fell in the deficient group (from 0.104 to 0.084). At the completion of the study, plasma tryptophan ratio was significantly lower in the calorie deficient group (0.091) compared with the control group (0.103). Decrements in tryptophan, but not tyrosine, ratio were associated with impairments in simple and choice visual reaction time (r = −0.4415, P = 0.009; r = −0.4029, P = 0.018, respectively). Therefore, changes in plasma amino acids occurring during a controlled form of undernutrition can be substantial; some of these alterations may be related to the functional consequences of undernutrition.

Effect of leucine supplementation on fat free mass with prolonged hypoxic exposure during a 13-day trek to Everest Base Camp: a double-blind randomized study

Loss of body weight and fat-free mass (FFM) are commonly noted with prolonged exposure to hypobaric hypoxia. Recent evidence suggests protein supplementation, specifically leucine, may potentially attenuate loss of FFM in subcaloric conditions during normoxia. The purpose of this study was to determine if leucine supplementation would prevent the loss of FFM in subcaloric conditions during prolonged hypoxia. Eighteen physically active male (n = 10) and female (n = 8) trekkers completed a 13-day trek in Nepal to Everest Base Camp with a mean altitude of 4140 m (range 2810-5364 m). In this double-blind study, participants were randomized to ingest either leucine (LEU) (7 g leucine, 93 kcal, 14.5 g whey-based protein) or an isocaloric isonitrogenous control (CON) (0.3 g LEU, 93 kcal, 11.3 g collagen protein) twice daily prior to meals. Body weight, body composition, and circumferences of bicep, thigh, and calf were measured pre- and post-trek. There was a significant time effect for body weight (-2.2% ± 1.7%), FFM (-1.7% ± 1.5%), fat mass (-4.0% ± 6.9%), and circumferences (p < 0.05). However, there was no treatment effect on body weight (CON -2.3 ± 2.0%; LEU -2.2 ± 1.5%), FFM (CON -2.1 ± 1.5%; LEU -1.2 ± 1.6%), fat mass (CON -2.9% ± 5.9%; LEU -5.4% ± 8.1%), or circumferences. Although a significant loss of body weight, FFM, and fat mass was noted in 13 days of high altitude exposure, FFM loss was not attenuated by leucine. Future studies are needed to determine if leucine attenuates loss of FFM with longer duration high altitude exposure.