Elevations in plasma glucagon are associated with reduced insulin clearance after ingestion of a mixed-macronutrient meal in people with and without type 2 diabetes.

AIMS/HYPOTHESIS: The temporal suppression of insulin clearance after glucose ingestion is a key determinant of glucose tolerance for people without type 2 diabetes. Whether similar adaptations are observed after the ingestion of a mixed-macronutrient meal is unclear. METHODS: In a secondary analysis of data derived from two randomised, controlled trials, we studied the temporal responses of insulin clearance after the ingestion of a standardised breakfast meal consisting of cereal and milk in lean normoglycaemic individuals (n=12; Lean-NGT), normoglycaemic individuals with central obesity (n=11; Obese-NGT) and in people with type 2 diabetes (n=19). Pre-hepatic insulin secretion rates were determined by the deconvolution of C-peptide, and insulin clearance was calculated using a single-pool model. Insulin sensitivity was measured by an oral minimal model. RESULTS: There were divergent time course changes in insulin clearance between groups. In the Lean-NGT group, there was an immediate post-meal increase in insulin clearance compared with pre-meal values (p<0.05), whereas insulin clearance remained stable at baseline values in Obese-NGT or declined slightly in the type 2 diabetes group (p<0.05). The mean AUC for insulin clearance during the test was ~40% lower in the Obese-NGT (1.3 ± 0.4 l min-1 m-2) and type 2 diabetes (1.4 ± 0.7 l min-1 m-2) groups compared with Lean-NGT (1.9 ± 0.5 l min-1 m-2; p<0.01), with no difference between the Obese-NGT and type 2 diabetes groups. HOMA-IR and glucagon AUC emerged as predictors of insulin clearance AUC, independent of BMI, age or insulin sensitivity (adjusted R2=0.670). Individuals with increased glucagon AUC had a 40% reduction in insulin clearance AUC (~ -0.75 l min-1 m-2; p<0.001). CONCLUSIONS/INTERPRETATION: The ingestion of a mixed-macronutrient meal augments differing temporal profiles in insulin clearance among individuals without type 2 diabetes, which is associated with HOMA-IR and the secretion of glucagon. Further research investigating the role of hepatic glucagon signalling in postprandial insulin kinetics is warranted. TRIAL REGISTRATION: ISRCTN17563146 and ISRCTN95281775.

The Mediterranean diet is not associated with neuroimaging or cognition in middle-aged adults: a cross-sectional analysis of the PREVENT dementia programme.

BACKGROUND AND PURPOSE: The Mediterranean diet (MedDiet) has been associated with reduced dementia incidence in several studies. It is important to understand if diet is associated with brain health in midlife, when Alzheimer's disease and related dementias are known to begin. METHODS: This study used data from the PREVENT dementia programme. Three MedDiet scores were created (the Pyramid, Mediterranean Diet Adherence Screener [MEDAS] and MEDAS continuous) from a self-reported food frequency questionnaire. Primary outcomes were hippocampal volume and cube-transformed white matter hyperintensity volume. Secondary outcomes included cornu ammonis 1 and subiculum hippocampal subfield volumes, cortical thickness and measures of cognition. Sex-stratified analyses were run to explore differential associations between diet and brain health by sex. An exploratory path analysis was conducted to study if any associations between diet and brain health were mediated by cardiovascular risk factors for dementia. RESULTS: In all, 504 participants were included in this analysis, with a mean Pyramid score of 8.10 (SD 1.56). There were no significant associations between any MedDiet scoring method and any of the primary or secondary outcomes. There were no differences by sex in any analyses and no significant mediation between the Pyramid score and global cognition by cardiovascular risk factors. CONCLUSIONS: Overall, this study did not find evidence for an association between the MedDiet and either neuroimaging or cognition in a midlife population study. Future work should investigate associations between the MedDiet and Alzheimer's disease and related dementias biomarkers as well as functional neuroimaging in a midlife population.

Are there interindividual differences in the reactive hypoglycaemia response to breakfast? A replicate crossover trial.

BACKGROUND: Following consumption of a meal, circulating glucose concentrations can rise and then fall briefly below the basal/fasting concentrations. This phenomenon is known as reactive hypoglycaemia but to date no researcher has explored potential inter-individual differences in response to meal consumption. OBJECTIVE: We conducted a secondary analysis of existing data to examine inter-individual variability of reactive hypoglycaemia in response to breakfast consumption. METHODS: Using a replicate crossover design, 12 healthy, physically active men (age: 18-30 y, body mass index: 22.1 to 28.0 kg⋅m- 2) completed two identical control (continued overnight fasting) and two breakfast (444 kcal; 60% carbohydrate, 17% protein, 23% fat) conditions in randomised sequences. Blood glucose and lactate concentrations, serum insulin and non-esterified fatty acid concentrations, whole-body energy expenditure, carbohydrate and fat oxidation rates, and appetite ratings were determined before and 2 h after the interventions. Inter-individual differences were explored using Pearson's product-moment correlations between the first and second replicates of the fasting-adjusted breakfast response. Within-participant covariate-adjusted linear mixed models and a random-effects meta-analytical approach were used to quantify participant-by-condition interactions. RESULTS: Breakfast consumption lowered 2-h blood glucose by 0.44 mmol/L (95%CI: 0.76 to 0.12 mmol/L) and serum NEFA concentrations, whilst increasing blood lactate and serum insulin concentrations (all p < 0.01). Large, positive correlations were observed between the first and second replicates of the fasting-adjusted insulin, lactate, hunger, and satisfaction responses to breakfast consumption (all r > 0.5, 90%CI ranged from 0.03 to 0.91). The participant-by-condition interaction response variability (SD) for serum insulin concentration was 11 pmol/L (95%CI: 5 to 16 pmol/L), which was consistent with the τ-statistic from the random-effects meta-analysis (11.7 pmol/L, 95%CI 7.0 to 22.2 pmol/L) whereas effects were unclear for other outcome variables (e.g., τ-statistic value for glucose: 0 mmol/L, 95%CI 0.0 to 0.5 mmol/L). CONCLUSIONS: Despite observing reactive hypoglycaemia at the group level, we were unable to detect any meaningful inter-individual variability of the reactive hypoglycaemia response to breakfast. There was, however, evidence that 2-h insulin responses to breakfast display meaningful inter-individual variability, which may be explained by relative carbohydrate dose ingested and variation in insulin sensitivity of participants.

Pharmacokinetic Profile of Incremental Oral Doses of Dietary Nitrate in Young and Older Adults: A Crossover Randomized Clinical Trial.

BACKGROUND: Dietary nitrate consumption can increase concentrations of nitrate and nitrite in blood, saliva, and urine. Whether the change in concentrations is influenced by age is currently unknown. OBJECTIVES: We aimed to measure changes in nitrate and nitrite concentrations in plasma, urine, and saliva and exhaled NO concentrations after single incremental doses of dietary nitrate in young and older healthy adults. METHODS: Twelve young (18-35 y old) and 12 older (60-75 y old) healthy, nonsmoking participants consumed single doses of 100 g, 200 g, 300 g whole beetroot (BR) and 1000 mg potassium nitrate (positive control) ≥7 d apart in a crossover, randomized clinical trial. Plasma nitrate and nitrite concentrations and exhaled NO concentrations were measured over a 5-h period. Salivary nitrate and nitrite concentrations were measured over a 12-h period and urinary nitrate over a 24-h period. Time, intervention, age, and interaction effects were measured with repeated-measures ANOVAs. RESULTS: Dose-dependent increases were seen in plasma, salivary, and urinary nitrate after BR ingestion (all P ≤ 0.002) but there were no differences between age groups at baseline (all P ≥ 0.56) or postintervention (all P ≥ 0.12). Plasma nitrite concentrations were higher in young than older participants at baseline (P = 0.04) and after consumption of 200 g (P = 0.04; +25.7 nmol/L; 95% CI: 0.97, 50.3 nmol/L) and 300 g BR (P = 0.02; +50.3 nmol/L; 95% CI: 8.57, 92.1 nmol/L). Baseline fractional exhaled NO (FeNO) concentrations were higher in the younger group [P = 0.03; +8.60 parts per billion (ppb); 95% CI: 0.80, 16.3 ppb], and rose significantly over the 5-h period, peaking 5 h after KNO3 consumption (39.4 ± 4.5 ppb; P < 0.001); however, changes in FeNO were not influenced by age (P = 0.276). CONCLUSIONS: BR is a source of bioavailable dietary nitrate in both young and older adults and can effectively raise nitrite and nitrate concentrations. Lower plasma nitrite and FeNO concentrations were found in older subjects, confirming the impact of ageing on NO bioavailability across different systems.This trial was registered at www.isrctn.com as ISRCTN86706442.

Relative protein intake and associations with markers of physical function in those with type 2 diabetes.

AIMS: To examine the independent associations between relative protein intake (g kg-1  day 1 ) and markers of physical function in those with type 2 diabetes, while also comparing with current guidelines for protein intake. METHODS: This analysis reports data from the ongoing Chronotype of Patients with Type 2 Diabetes and Effect on Glycaemic Control (CODEC) study. Functional assessments included: Short Physical Performance Battery (SPPB), 60 s sit-to-stand (STS-60), 4-m gait speed, time to rise from a chair (×5) and handgrip strength. Participants also completed a self-reported 4 day diet diary. Regression analyses assessed whether relative protein intake was associated with markers of physical function. Interaction terms assessed whether the associations were modified by sex, age, HbA1c or body mass index (BMI). RESULTS: 413 participants were included (mean ± SD:age = 65.0 ± 7.7 years, 33% female, BMI = 30.6 ± 5.1 kg/m2 ). The average total protein intake was 0.88 ± 0.31 g kg-1  day-1 . 33% of individuals failed to meet the reference nutrient intake for the United Kingdom (≥0.75 g kg-1  day-1 ), and 87% for European recommendations (≥1.2 g kg-1  day-1 ). After adjustment, each 0.5 g/kg of protein intake was associated with an 18.9% (95% CI: 2.3, 35.5) higher SPPB score, 22.7% (1.1, 44.3) more repetitions in STS-60, 21.1% (4.5, 37.7) faster gait speed and 33.2% (16.9, 49.5) lower chair rise time. There were no associations with handgrip strength or any interactions. CONCLUSIONS: Relative protein intake was positively associated with physical function outcomes, even after consideration of total energy intake. As a number of individuals were below the current guidelines, protein intake may be a modifiable factor of importance for people with type 2 diabetes.

Whey protein consumption following fasted exercise reduces early postprandial glycaemia in centrally obese males: a randomised controlled trial.

PURPOSE: Acute submaximal exercise and whey protein supplementation have been reported to improve postprandial metabolic and appetite responses to a subsequent meal independently. We aimed to examine the combination of these strategies on postprandial responses to a carbohydrate-rich breakfast. METHODS: Twelve centrally obese males (age 41 ± 3 years, waist circumference 123.4 ± 2.9 cm), completed three trials in a single-blind, crossover design. Participants rested for 30 min (CON) or completed 30 min low-moderate-intensity treadmill walking (51 ± 1% [Formula: see text]) followed immediately by ingestion of 20 g whey protein (EX + PRO) or placebo (EX). After 15 min, a standardised breakfast was consumed and blood, expired gas and subjective appetite were sampled postprandially. After 240 min, an ad libitum lunch meal was provided to assess energy intake. RESULTS: During EX + PRO, post-breakfast peak blood glucose was reduced when compared with EX and CON (EX + PRO: 7.6 ± 0.4 vs EX: 8.4 ± 0.3; CON: 8.3 ± 0.3 mmol l-1, p ≤ 0.04). Early postprandial glucose AUC0-60 min was significantly lower under EX + PRO than EX (p = 0.011), but not CON (p = 0.12). Over the full postprandial period, AUC0-240 min during EX + PRO did not differ from other trials (p > 0.05). Peak plasma insulin concentrations and AUC0-240 min were higher during EX + PRO than CON, but similar to EX. Plasma triglyceride concentrations, substrate oxidation and subjective appetite responses were similar across trials and ad libitum energy intake was not influenced by prior fasted exercise, nor its combination with whey protein supplementation (p > 0.05). CONCLUSION: Following fasted low-moderate-intensity exercise, consuming whey protein before breakfast may improve postprandial glucose excursions, without influencing appetite or subsequent energy intake, in centrally obese males. TRIAL REGISTRATION NUMBER: NCT02714309.

The effects of vitamin C and E on exercise-induced physiological adaptations: a systematic review and Meta-analysis of randomized controlled trials.

We conducted a systematic review and meta-analysis of randomized controlled trials examining the effect of vitamin C and/or E on exercise-induced training adaptations. Medline, Embase and SPORTDiscus databases were searched for articles from inception until June 2019. Inclusion criteria was studies in adult humans where vitamin C and/or E had to be consumed alongside a supervised exercise training program of ≥4 weeks. Nine trials were included in the analysis of aerobic exercise adaptations and nine for resistance training (RT) adaptations. Vitamin C and/or E did not attenuate aerobic exercise induced improvements in maximal aerobic capacity (V̇O2max) (SMD -0.14, 95% CI: -0.43 to 0.15, P = 0.35) or endurance performance (SMD -0.01, 95% CI: -0.38 to 0.36, P = 0.97). There were also no effects of these supplements on lean mass and muscle strength following RT (SMD -0.07, 95% CI: -0.36 to 0.23, P = 0.67) and (SMD -0.15, 95% CI: -0.16 to 0.46, P = 0.35), respectively. There was also no influence of age on any of these outcomes (P > 0.05). These findings suggest that vitamin C and/or E does not inhibit exercise-induced changes in physiological function. Studies with larger sample sizes and adequate power are still required.

The Effects of a High-Protein Diet on Markers of Muscle Damage Following Exercise in Active Older Adults: A Randomized, Controlled Trial.

PURPOSE: This study examined whether a higher protein diet following strenuous exercise can alter markers of muscle damage and inflammation in older adults. METHODS: Using a double-blind, independent group design, 10 males and eight females (age 57 ± 4 years; mass 72.3 ± 5.6 kg; height 1.7 ± 6.5 m) were supplied with a higher protein (2.50 g·kg-1·day-1) or moderate protein (1.25 g·kg-1·day-1) diet for 48 hr after 140 squats with 25% of their body mass. Maximal isometric voluntary contractions, muscle soreness, creatine kinase, Brief Assessment of Mood Adapted, and inflammatory markers were measured preexercise, and 24 hr and 48 hr postexercise. RESULTS: The maximal isometric voluntary contractions decreased postexercise (p = .001, ηp2=.421), but did not differ between groups (p = .822, ηp2=.012). Muscle soreness peaked at 24 hr post in moderate protein (44 ± 30 mm) and 48 hr post in higher protein (70 ± 46 mm; p = .005; ηp2=.282); however, no group differences were found (p = .585; ηp2=.083). Monocytes and lymphocytes significantly decreased postexercise, and eosinophils increased 24 hr postexercise (p < 0.05), but neutrophils, creatine kinase, interleukin-6, C-reactive protein, monocyte chemotactic protein-1, and Brief Assessment of Mood Adapted were unchanged by exercise or the intervention (p > .05). CONCLUSION: In conclusion, 2.50 g·kg-1·day-1 of protein is not more effective than 1.25 g·kg-1·day-1 for attenuating indirect markers of muscle damage and inflammation following strenuous exercise in older adults.

Protein Valuation in Food Choice Is Positively Associated with Lean Mass in Older Adults.

BACKGROUND: Calorie for calorie, protein is more satiating than carbohydrate or fat. However, it remains unclear whether humans perceive calories derived from these macronutrients equally and whether lean mass is associated with a tendency to "value" protein when dietary decisions are made. OBJECTIVES: This study aimed to determine the test-retest reliability of a novel method for quantifying macronutrient valuations in human volunteers and to determine whether "protein valuation" is associated with a higher fat-free mass index (FFMI) in older adults. METHODS: A 2-alternative, forced-choice task in which 25 foods were compared in 300 trials was undertaken in 2 studies. In study 1, participants (age range 19-71 y, n = 92) attended 2 test sessions, spaced 1 wk apart. In study 2, older adults (age range 40-85 y; n = 91) completed the food-choice task and assessed the test foods for liking, expected satiety, and perceived healthiness. Body composition and habitual protein intake were assessed in both studies. Data were analyzed through the use of individual binomial logistic regressions and multilevel binomial logistic regressions. RESULTS: In study 1, measures of macronutrient valuation showed excellent test-retest reliability; responses in the forced-choice task were highly correlated (week 1 compared with week 2; protein, r = 0.83, P < 0.001; carbohydrate, r = 0.90, P < 0.001; fat, r = 0.90, P < 0.001). Calorie for calorie, protein and carbohydrate were stronger predictors of choice than fat (P < 0.001). In study 2, protein was a stronger predictor than both carbohydrate (P = 0.039) and fat (P = 0.003), and a positive interaction was observed between protein valuation and FFMI (OR = 1.64; 95% CI: 1.38, 1.95; P < 0.001). This was the case after controlling for age, gender, liking for foods, and habitual protein consumption. CONCLUSIONS: Together, these findings demonstrate that adult humans value calories derived from protein, carbohydrate, and fat differently, and that the tendency to value protein is associated with greater lean mass in older adults.

Skipping Breakfast Before Exercise Creates a More Negative 24-hour Energy Balance: A Randomized Controlled Trial in Healthy Physically Active Young Men.

BACKGROUND: At rest, omission of breakfast lowers daily energy intake, but also lowers energy expenditure, attenuating any effect on energy balance. The effect of breakfast omission on energy balance when exercise is prescribed is unclear. OBJECTIVES: The aim of this study was to assess the effect on 24-h energy balance of omitting compared with consuming breakfast prior to exercise. METHODS: Twelve healthy physically active young men (age 23 ± 3 y, body mass index 23.6 ± 2.0 kg/m2) completed 3 trials in a randomized order (separated by >1 week): a breakfast of oats and milk (431 kcal; 65 g carbohydrate, 11 g fat, 19 g protein) followed by rest (BR); breakfast before exercise (BE; 60 min cycling at 50 % peak power output); and overnight fasting before exercise (FE). The 24-h energy intake was calculated based on the food consumed for breakfast, followed by an ad libitum lunch, snacks, and dinner. Indirect calorimetry with heart-rate accelerometry was used to measure substrate utilization and 24-h energy expenditure. A [6,6-2H2]glucose infusion was used to investigate tissue-specific carbohydrate utilization. RESULTS: The 24-h energy balance was -400 kcal (normalized 95% CI: -230, -571 kcal) for the FE trial; this was significantly lower than both the BR trial (492 kcal; normalized 95% CI: 332, 652 kcal) and the BE trial (7 kcal; normalized 95% CI: -153, 177 kcal; both P < 0.01 compared with FE). Plasma glucose utilization in FE (mainly representing liver glucose utilization) was positively correlated with energy intake compensation at lunch (r = 0.62, P = 0.03), suggesting liver carbohydrate plays a role in postexercise energy-balance regulation. CONCLUSIONS: Neither exercise energy expenditure nor restricted energy intake via breakfast omission were completely compensated for postexercise. In healthy men, pre-exercise breakfast omission creates a more negative daily energy balance and could therefore be a useful strategy to induce a short-term energy deficit. This trial was registered at clinicaltrials.gov as NCT02258399.

Effect of supplemental whey protein timing on postprandial glycaemia in centrally obese males.

Consuming whey protein before a meal may reduce postprandial glucose excursions, however, optimising timing of supplementation is important to improve its clinical utility. A total of thirteen centrally obese, insulin-resistant males (waist circumference: 121 (sem 3) cm; homeostasis model assessment for insulin resistance (HOMA-IR): 6·4 (sem 1·2)) completed four experimental conditions in a single-blind, crossover design. Participants consumed mixed-macronutrient breakfast and lunch meals on all occasions, with 20 g whey protein consumed 15 min before (PRE), alongside (DUR) or 15 min post-breakfast (POST) or omitted (CON). Capillary glucose and plasma concentrations of insulin, TAG and NEFA, in addition to subjective appetite ratings, were collected for 180 min after each meal. PRE and DUR reduced post-breakfast glucose peak by 17·0 (sem 1·9) % (P<0·001) and 9·2 (sem 2·9) % (P=0·046), respectively, compared with CON. Post-breakfast glucose AUC was lower following PRE compared with POST and CON (PRE: 982 (sem 30) v. POST: 1031 (sem 36) and CON: 1065 (sem 37) mmol/l×180 min; P≤0·042) but similar to DUR (1013 (sem 32) mmol/l×180 min; P=0·77). Insulin was lower during PRE, when compared with POST and DUR (both P≤0·042) but similar to CON. There were no between-condition differences in measures of postprandial lipaemia or appetite, and no effect of condition post-lunch. Consumption of whey protein as a preload or alongside a mixed-macronutrient breakfast reduces postprandial glucose excursions in centrally obese, insulin-resistant males. Whey consumed as a preload has superior glycaemic-lowering effects. Supplementation at breakfast does not alter glycaemic responses to subsequent meals.

Preexercise breakfast ingestion versus extended overnight fasting increases postprandial glucose flux after exercise in healthy men.

The aim of this study was to characterize postprandial glucose flux after exercise in the fed versus overnight fasted state and to investigate the potential underlying mechanisms. In a randomized order, twelve men underwent breakfast-rest [(BR) 3 h semirecumbent], breakfast-exercise [(BE) 2 h semirecumbent before 60 min of cycling (50% peak power output)], and overnight fasted exercise [(FE) as per BE omitting breakfast] trials. An oral glucose tolerance test (OGTT) was completed after exercise (after rest on BR). Dual stable isotope tracers ([U-13C] glucose ingestion and [6,6-2H2] glucose infusion) and muscle biopsies were combined to assess postprandial plasma glucose kinetics and intramuscular signaling, respectively. Plasma intestinal fatty acid binding (I-FABP) concentrations were determined as a marker of intestinal damage. Breakfast before exercise increased postexercise plasma glucose disposal rates during the OGTT, from 44 g/120 min in FE {35 to 53 g/120 min [mean (normalized 95% confidence interval)] to 73 g/120 min in BE [55 to 90 g/120 min; P = 0.01]}. This higher plasma glucose disposal rate was, however, offset by increased plasma glucose appearance rates (principally OGTT-derived), resulting in a glycemic response that did not differ between BE and FE ( P = 0.11). Plasma I-FABP concentrations during exercise were 264 pg/ml (196 to 332 pg/ml) lower in BE versus FE ( P = 0.01). Breakfast before exercise increases postexercise postprandial plasma glucose disposal, which is offset (primarily) by increased appearance rates of orally ingested glucose. Therefore, metabolic responses to fed-state exercise cannot be readily inferred from studies conducted in a fasted state.

The altered human serum metabolome induced by a marathon.

INTRODUCTION: Endurance races have been associated with a substantial amount of adverse effects which could lead to chronic disease and long-term performance impairment. However, little is known about the holistic metabolic changes occurring within the serum metabolome of athletes after the completion of a marathon. OBJECTIVES: Considering this, the aim of this study was to better characterize the acute metabolic changes induced by a marathon. METHODS: Using an untargeted two dimensional gas chromatography time-of-flight mass spectrometry metabolomics approach, pre- and post-marathon serum samples of 31 athletes were analyzed and compared to identify those metabolites varying the most after the marathon perturbation. RESULTS: Principle component analysis of the comparative groups indicated natural differentiation due to variation in the total metabolite profiles. Elevated concentrations of carbohydrates, fatty acids, tricarboxylic acid cycle intermediates, ketones and reduced concentrations of amino acids indicated a metabolic shift between various fuel substrate systems. Additionally, elevated odd-chain fatty acids and α-hydroxy acids indicated the utilization of α-oxidation and autophagy as alternative energy-producing mechanisms. Adaptations in gut microbe-associated markers were also observed and correlated with the metabolic flexibility of the athlete. CONCLUSION: From these results it is evident that a marathon places immense strain on the energy-producing pathways of the athlete, leading to extensive protein degradation, oxidative stress, mammalian target of rapamycin complex 1 inhibition and autophagy. A better understanding of this metabolic shift could provide new insights for optimizing athletic performance, developing more efficient nutrition regimens and identify strategies to improve recovery.

Whey protein consumption after resistance exercise reduces energy intake at a post-exercise meal.

PURPOSE: Protein consumption after resistance exercise potentiates muscle protein synthesis, but its effects on subsequent appetite in this context are unknown. This study examined appetite and energy intake following consumption of protein- and carbohydrate-containing drinks after resistance exercise. METHODS: After familiarisation, 15 resistance training males (age 21 ± 1 years, body mass 78.0 ± 11.9 kg, stature 1.78 ± 0.07 m) completed two randomised, double-blind trials, consisting of lower-body resistance exercise, followed by consumption of a whey protein (PRO 23.9 ± 3.6 g protein) or dextrose (CHO 26.5 ± 3.8 g carbohydrate) drink in the 5 min post-exercise. An ad libitum meal was served 60 min later, with subjective appetite measured throughout. Drinks were flavoured and matched for energy content and volume. The PRO drink provided 0.3 g/kg body mass protein. RESULTS: Ad libitum energy intake (PRO 3742 ± 994 kJ; CHO 4172 ± 1132 kJ; P = 0.007) and mean eating rate (PRO 339 ± 102 kJ/min; CHO 405 ± 154 kJ/min; P = 0.009) were lower during PRO. The change in eating rate was associated with the change in energy intake (R = 0.661, P = 0.007). No interaction effects were observed for subjective measures of appetite. The PRO drink was perceived as creamier and thicker, and less pleasant, sweet and refreshing (P < 0.05). CONCLUSION: These results suggest whey protein consumption after resistance exercise reduces subsequent energy intake, and this might be partially mediated by a reduced eating rate. Whilst this reduced energy intake is unlikely to impair hypertrophy, it may be of value in supporting an energy deficit for weight loss.

Correction to: A comparison of isomaltulose versus maltodextrin ingestion during soccer-specific exercise.

The article "A comparison of isomaltulose versus maltodextrin ingestion during soccer-specific exercise", written by "Emma J. Stevenson, Anthony Watson, Stephan Theis, Anja Holz,·Liam D. Harper, Mark Russell", was originally published Online First without open access. After publication in volume [117], issue [11], page.

The plasma bioavailability of nitrate and betanin from Beta vulgaris rubra in humans.

PURPOSE: To evaluate the plasma bioavailability of betanin and nitric oxide (NOx) after consuming beetroot juice (BTJ) and whole beetroot (BF). BTJ and BF were also analysed for antioxidant capacity, polyphenol content (TPC) and betalain content. METHODS: Ten healthy males consumed either 250 ml of BTJ, 300 g of BF or a placebo drink, in a randomised, crossover design. Venous plasma samples were collected pre (baseline), 1, 2, 3, 5 and 8 h post-ingestion. Betanin content in BTJ, BF and plasma was analysed with reverse-phase high-performance liquid chromatography (HPLC) and mass spectrometry detection (LCMS). Antioxidant capacity was estimated using the Trolox equivalent antioxidant capacity (TEAC) and polyphenol content using Folin-Ciocalteu colorimetric methods [gallic acid equivalents (GAE)] and betalain content spectrophotometrically. RESULTS: TEAC was 11.4 ± 0.2 mmol/L for BTJ and 3.4 ± 0.4 µmol/g for BF. Both BTJ and BF contained a number of polyphenols (1606.9 ± 151 mg/GAE/L and 1.67 ± 0.1 mg/GAE/g, respectively), betacyanins (68.2 ± 0.4 mg/betanin equivalents/L and 19.6 ± 0.6 mg/betanin equivalents/100 g, respectively) and betaxanthins (41.7 ± 0.7 mg/indicaxanthin equivalents/L and 7.5 ± 0.2 mg/indicaxanthin equivalents/100 g, respectively). Despite high betanin contents in both BTJ (~194 mg) and BF (~66 mg), betanin could not be detected in the plasma at any time point post-ingestion. Plasma NOx was elevated above baseline for 8 h after consuming BTJ and 5 h after BF (P < 0.05). CONCLUSIONS: These data reveal that BTJ and BF are rich in phytonutrients and may provide a useful means of increasing plasma NOx bioavailability. However, betanin, the major betalain in beetroot, showed poor bioavailability in plasma.

A comparison of isomaltulose versus maltodextrin ingestion during soccer-specific exercise.

PURPOSE: The performance and physiological effects of isomaltulose and maltodextrin consumed intermittently during prolonged soccer-specific exercise were investigated. METHODS: University soccer players (n = 22) performed 120 min of intermittent exercise while consuming 8% carbohydrate-electrolyte drinks (equivalent to ~ 20 g h-1) containing maltodextrin (Glycaemic Index: 90-100), isomaltulose (Glycaemic Index: 32) or a carbohydrate-energy-free placebo in a manner replicating the practices of soccer players (i.e., during warm-up and half-time). Physical (sprinting, jumping) and technical (shooting, dribbling) performance was assessed. RESULTS: Blood glucose and plasma insulin (both P < 0.001) concentrations varied by trial with isomaltulose maintaining > 13% higher blood glucose concentrations between 75 and 90 min versus maltodextrin (P < 0.05). A decline in glycaemia at 60 min in maltodextrin was attenuated with isomaltulose (-19 versus -4%; P = 0.015). Carbohydrates attenuated elevations in plasma epinephrine concentrations (P < 0.05), but isomaltulose proved most effective at 90 and 120 min. Carbohydrates did not attenuate IL-6 increases or reductions in physical or technical performances (all P > 0.05). Ratings of abdominal discomfort were influenced by trial (P < 0.05) with lower values for both carbohydrates compared to PLA from 60 min onwards. CONCLUSIONS: Although carbohydrates (~ 20 g h-1) did not attenuate performance reductions throughout prolonged soccer-specific exercise, isomaltulose maintained higher blood glucose at 75-90 min, lessened the magnitude of the exercise-induced rebound glycaemic response and attenuated epinephrine increases whilst maintaining similar abdominal discomfort values relative to maltodextrin. When limited opportunities exist to consume carbohydrates on competition-day, low-glycaemic isomaltulose may offer an alternative nutritional strategy for exercising soccer players.

T-regulatory cells exhibit a biphasic response to prolonged endurance exercise in humans.

PURPOSE: T-regulatory cells (Tregs) are a sub-population of lymphocytes that act to suppress aberrant immune responses. We investigated changes in the numbers of naïve and terminally differentiated Tregs in the peripheral blood to establish their role in the immuno-suppressive response to prolonged exercise. METHODS: Blood was drawn from seventeen experienced runners (age 40 ± 12 years; height 1.75 ± 0.08 m; mass 71.4 ± 10.8 kg) before, ~1 h after (POST-1h), and on the day following the marathon (POST-1d). Tregs (CD3+CD4+Foxp3+CD25++CD127-) were analysed in peripheral blood mononuclear cells using flow cytometry. The markers CD45RA and HLA-DR were included to define naïve and terminally differentiated Tregs, respectively. RESULTS: The absolute number of Tregs decreased (27%) POST-1h marathon (P < 0.001) but increased (21%) at POST-1d (P < 0.01). Naïve CD45RA+ Tregs fell by 39% POST-1h (P < 0.01) but were unaffected POST-1d (P > 0.05). In contrast, an increased number of Tregs expressing HLA-DR was observed at POST-1d (P < 0.01). Interleukin (IL)-1ß, IL-6, IL-8 and IL-10 levels in the serum all increased POST-1h (P > 0.05) but returned to pre-exercise levels POST-1d. The suppressive cytokine, transforming growth factor-beta, was unaffected by the marathon (P > 0.05). CONCLUSIONS: These results suggest that Tregs do not play a major role in immune suppression in the early hours of recovery from a marathon. However, terminally differentiated HLA-DR+ Tregs are mobilized the following day, which could represent a compensatory attempt by the host to restore immune homeostasis and limit excessive cell damage.

Metabolic, endocrine and appetite-related responses to acute and daily milk snack consumption in healthy, adolescent males.

Comprising of two experiments, this study assessed the metabolic, endocrine and appetite-related responses to acute and chronic milk consumption in adolescent males (15-18 y). Eleven adolescents [mean ± SD age: 16.5 ± 0.9 y; BMI: 23.3 ± 3.3 kg/m2] participated in the acute experiment and completed two laboratory visits (milk vs. fruit-juice) in a randomized crossover design, separated by 7-d. Seventeen adolescents [age: 16.1 ± 0.9 y; BMI: 21.8 ± 3.7 kg/m2] completed the chronic experiment. For the chronic experiment, a parallel design with two groups was used. Participants were randomly allocated and consumed milk (n = 9) or fruit-juice (n = 8) for 28-d, completing laboratory visits on the first (baseline, day-0) and last day (follow-up, day-28) of the intervention phase. On laboratory visits (for both experiments), measures of appetite, metabolism and endocrine responses were assessed at regular intervals. In addition, eating behavior was quantified by ad libitum assessment under laboratory conditions and in the free-living environment by weighed food record. Acute milk intake stimulated glucagon (P = 0.027 [16.8 pg mL; 95% CI: 2.4, 31.3]) and reduced ad libitum energy intake relative to fruit-juice (P = 0.048 [-651.3 kJ; 95% CI: -1294.1, -8.6]), but was comparable in the free-living environment. Chronic milk intake reduced free-living energy intake at the follow-up visit compared to baseline (P = 0.013 [-1910.9 kJ; 95% CI: -554.6, -3267.2]), whereas the opposite was apparent for fruit-juice. Relative to baseline, chronic milk intake increased the insulin response to both breakfast (P = 0.031) and mid-morning milk consumption (P = 0.050) whilst attenuating blood glucose (P = 0.025). Together, these findings suggest milk consumption impacts favorably on eating behavior in adolescent males, potentially through integrated endocrine responses.

Antioxidant-rich beetroot juice does not adversely affect acute neuromuscular adaptation following eccentric exercise.

This study examined the effects of beetroot juice on the repeated bout effect (RBE) to eccentric exercise. Twenty-nine recreationally active males performed two bouts of 100-drop jumps, separated by 14-21 days. Using a double-blind, independent groups design, participants consumed either a higher dose beetroot juice (H-BT; 250 ml, n = 10), a lower dose beetroot juice (L-BT; 125 ml, n = 9) or an isocaloric placebo (PLA; 250 ml, n = 10) for 3 days after bout 1; no drinks were consumed after bout 2. Maximal isometric voluntary contraction (MIVC), countermovement jump (CMJ), pressure-pain threshold (PPT) and creatine kinase (CK) were measured pre, post, 24, 48 and 72 h following both bouts. In bout 2, CMJ and MIVC recovered quicker and CK activity was attenuated (versus bout 1) (P < 0.05) in all groups, demonstrating an RBE. At 24 h post bout 1, MIVC was 84.1 ± 16.1, 83.6 ± 11.6, 79.7 ± 15.1% relative to baseline values in the H-BT, L-BT and PLA groups, respectively; at 24 h post bout 2, MIVC recovered to 90.7 ± 13.7, 92.9 ± 6.9, 87.8 ± 6.9, in the H-BT, L-BT and PLA groups, respectively. These findings suggest that supplementation with antioxidant-rich beetroot juice does not adversely affect acute adaptations to a bout of eccentric exercise.