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.

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.

A comparison of subjective and objective measures of physical exertion.

Better methods are needed to improve validity and reliability of physical activity (PA) assessment instruments. The purpose of this study was to compare individual's Borg's 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 (χ(2) = 10.9, P = 0.004), and exercise status (χ(2) = 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.

Musculoskeletal abnormalities of the tibia in juvenile rheumatoid arthritis.

OBJECTIVE: To characterize local bone geometry, density, and strength, using peripheral quantitative computed tomography (pQCT), compared with general bone characteristics as measured using dual x-ray absorptiometry (DXA), and to assess their relationship to disease-related factors in children with juvenile rheumatoid arthritis (JRA). METHODS: Forty-eight children ages 4-18 years with JRA (17 pauciarticular, 23 polyarticular, 8 systemic) were compared with age-matched healthy controls (n = 266). Measurements included cortical and trabecular bone geometry, density, and strength at the distal and midshaft tibia determined by pQCT, and whole-body, lumbar spine, and femoral neck measurements by DXA. RESULTS: Methotrexate (MTX) was prescribed to 23 of 48 patients (47.9%) and glucocorticoids and MTX were prescribed to 15 of 48 patients (31.3%), with the greatest use in children with systemic JRA. All JRA patients had decreased tibia trabecular bone density, cortical bone size and strength, and muscle mass. Children with systemic JRA had lower femoral neck densities. Systemic JRA was associated with a shorter, less mineralized skeleton, while a narrower, less mineralized skeleton was observed in polyarticular JRA. The tibia diaphysis was narrower with decreased muscle mass, but normal, size-adjusted bone mineral in all subtypes indicated a localized effect of JRA on bone. Patients exposed to glucocorticoids and MTX or to glucocorticoids or MTX alone had greatly reduced trabecular density, cortical bone geometry properties, and bone mineral content, muscle mass, and bone strength. CONCLUSION: Children with JRA have decreased skeletal size, muscle mass, trabecular bone density, cortical bone geometry, and strength. Not surprisingly, these bone abnormalities are more pronounced in children with greater disease severity.

Association of adipose and red blood cell lipids with severity of dominant Stargardt macular dystrophy (STGD3) secondary to an ELOVL4 mutation.

OBJECTIVE: To determine whether adipose and red blood cell membrane lipids, particularly long-chain polyunsaturated fatty acids such as docosahexaenoic acid and eicosapentaenoic acid, are significantly correlated with phenotype in a family with autosomal dominant Stargardt macular dystrophy (gene locus STGD3). A mutation in the ELOVL4 gene is responsible for the macular dystrophy in this family, and its disease-causing mechanism may be its possible involvement in fatty acid elongation in the retina. METHODS: The subjects in this study included 18 adult family members known to have a 2-base pair deletion in the ELOVL4 gene. Control subjects included 26 family members without the mutation. Each subject received a complete eye examination including fundus photographs, the results of which were used to grade the severity of macular dystrophy on a 3-tier scale. Red blood cell membrane and adipose tissue lipids were analyzed as an indication of short-term and long-term dietary fatty acid intake. RESULTS: When adipose lipids were analyzed, there was a significant inverse relationship between phenotypic severity and the level of eicosapentaenoic acid (r = -0.54; P = .04). When red blood cell lipids were analyzed, there were significant inverse relationships between phenotypic severity and levels of eicosapentaenoic acid (r = -0.55; P = .02) and docosahexaenoic acid (r = -0.48; P = .04). CONCLUSIONS: These results indicate that the phenotypic diversity in this family may be related to differences in dietary fat intake as reflected by adipose and red blood cell lipids. CLINICAL RELEVANCE: This study demonstrates that dietary factors can influence the severity of an inherited human macular dystrophy.

Bone mineral acquisition in adolescents with type 1 diabetes.

OBJECTIVE: To track bone mineral acquisition in adolescents with type 1 diabetes (DM). STUDY DESIGN: Subjects were adolescents, ages 12 to 18 years, with DM (n=42) and a healthy regional reference (n=199). Measurements of tibia bone characteristics by peripheral quantitative computed tomography (pQCT) and spine and whole body (WB) by dual-energy x-ray absorptiometry (DEXA), anthropometrics, and lifestyle questionnaires were obtained during a 12-month period. Disease duration, insulin dose, renal function, and glycosylated hemoglobin (HbA1c) values for the previous 12 months were recorded. RESULTS: Body size and maturation were similar between groups. DM had lower tibia, spine, and WB bone characteristics but greater muscle mass (LBM) and lower bone mineral content (BMC)/LBM at baseline and 12 months. Annual gains for tibia cortical bone and WB BMC/LBM were lower and inversely related to HbA1c levels (R=-0.36 to -0.51), whereas spine area and density and WBLBM were greater and were predicted by pubertal-driven growth. Overall, the DM cohort had 8.5% less WB BMC/LBM, suggesting that bone mineral deposition was not adequately adapted to muscle gains. CONCLUSIONS: Adolescents with type 1 diabetes continue to have smaller bone mass and bone size despite normal growth and maturation. Poor metabolic control appears to negatively influence bone mineral acquisition.

Food for high-altitude expeditions: Pugh got it right in 1954--a commentary on the report by L.G.C.E. Pugh: "Himalayan rations with special reference to the 1953 expedition to Mount Everest".

An examination of the nutritional recommendations at altitude by L.G.C.E. Pugh made in the early 1950s reveals that his approaches to feeding and hydration at altitude are still ascribed to today, 50 years later. We can forgive his one perhaps overstatement concerning the "craving" for carbohydrates at altitude if we simply acknowledge that he was generally correct about the benefits of carbohydrates for work at altitude. Pugh's emphasis on adequate energy intake and fluid intake at altitude is as sound today as it was in 1954.

Dietary modification and moderate antioxidant supplementation differentially affect serum carotenoids, antioxidant levels and markers of oxidative stress in older humans.

Oxidative stress is thought to be a factor in the progression of chronic diseases, and even the aging process itself. We examined the effect of two moderate vitamin, mineral and phytochemical supplements and a dietary intervention on markers of oxidative stress and antioxidant status in older humans. Subjects (n = 60, 65-85 y old) were enrolled in a 5-wk, double-blind, placebo-controlled study. The subjects were randomly assigned to a group with one of four interventions: antioxidant supplement capsule, antioxidant supplement tablet, high carotenoid diet or placebo. Postintervention serum levels of some of the supplemented carotenoids and alpha-tocopherol were higher in all treated groups compared with the placebo group and with preintervention levels within groups. Markers of oxidative stress or antioxidant capacity were not significantly different from preintervention levels, although the diet and supplement capsule groups had lower levels of some of those markers than the placebo group postintervention. The results suggest that both moderate antioxidant supplementation and a diet high in carotenoids elevate serum carotenoids and antioxidant levels in an older adult population, although with different specific effects.

Lack of effect of Rhodiola or oxygenated water supplementation on hypoxemia and oxidative stress.

OBJECTIVE: This study investigated the effects of 2 potentially "oxygen promoting" dietary supplements on hypoxia and oxidative stress at a simulated altitude of 4600 m. METHODS: Fifteen volunteers (ages 20-33) received 3 separate 60-minute hypoxic exposures by breathing 13.6% oxygen at an ambient barometric pressure of 633 mm Hg (simulating the partial pressure of oxygen at 4600 m elevation). Each subject received, in random order, treatments of a 7-day supply of placebo, Rhodiola rosea, and an acute dose of stabilized oxygen dissolved in water. Arterialized capillary blood oxygen samples (PcO2) were measured at baseline and at 30 and 60 minutes of exposure. Pulse oximeter oxyhemoglobin saturation (SaO2) was measured at baseline and at every 10 minutes of hypoxic exposure. Oxidative stress markers measured included baseline and 60-minute exposure serum lipid peroxides (LPO) and urine malondialdehyde (MDA). RESULTS: For each treatment group, PcO2 decreased by approximately 38% from baseline to 60-minute hypoxic exposure. Similarly, SaO2 also decreased among groups from approximately 97 to 81%. Serum lipid peroxides increased significantly in the placebo group and decreased significantly from baseline in response to the stabilized oxygen treatment (P = .02); there was a trend for decreased LPO with the Rhodiola treatment (P = .10). There were no significant changes for MDA among groups. CONCLUSIONS: The 2 dietary supplements investigated did not have a significant effect on blood oxygenation after 60 minutes of sedentary hypoxic exposure. Hypoxia-induced oxidative stress was observed in the control group only. Both supplements appeared not to increase oxidative stress and may decrease free radical formation after hypoxic exposure compared with the control.