Effects of physical form of ß-lactoglobulin and calcium ingestion on GLP-1 secretion, gastric emptying and energy intake in humans: a randomised crossover trial.

The aim of this study was to assess whether adding Ca2+ to aggregate or native forms of ß-lactoglobulin alters gut hormone secretion, gastric emptying rates and energy intake in healthy men and women. Fifteen healthy adults (mean ± sd: 9M/6F, age: 24 ± 5 years) completed four trials in a randomised, double-blind, crossover design. Participants consumed test drinks consisting of 30 g of ß-lactoglobulin in a native form with (NATIVE + MINERALS) and without (NATIVE) a Ca2+-rich mineral supplement and in an aggregated form both with (AGGREG + MINERALS) and without the mineral supplement (AGGREG). Arterialised blood was sampled for 120 min postprandially to determine gut hormone concentrations. Gastric emptying was determined using 13C-acetate and 13C-octanoate, and energy intake was assessed with an ad libitum meal at 120 min. A protein × mineral interaction effect was observed for total glucagon-like peptide-1 (GLP-1TOTAL) incremental AUC (iAUC; P < 0·01), whereby MINERALS + AGGREG increased GLP-1TOTAL iAUC to a greater extent than AGGREG (1882 ± 603 v. 1550 ± 456 pmol·l-1·120 min, P < 0·01), but MINERALS + NATIVE did not meaningfully alter the GLP-1 iAUC compared with NATIVE (1669 ± 547 v. 1844 ± 550 pmol·l-1·120 min, P = 0·09). A protein × minerals interaction effect was also observed for gastric emptying half-life (P < 0·01) whereby MINERALS + NATIVE increased gastric emptying half-life compared with NATIVE (83 ± 14 v. 71 ± 8 min, P < 0·01), whereas no meaningful differences were observed between MINERALS + AGGREG v. AGGREG (P = 0·70). These did not result in any meaningful changes in energy intake (protein × minerals interaction, P = 0·06). These data suggest that the potential for Ca2+ to stimulate GLP-1 secretion at moderate protein doses may depend on protein form. This study was registered at clinicaltrials.gov (NCT04659902).

Postprandial Metabolic Mesponses to High-fat Feeding in Healthy Adults Following Ingestion of Oolong Tea-Derived Polymerized Polyphenols: A Randomized, Double-blinded, Placebo-controlled Crossover Study.

BACKGROUND: Polymerized polyphenols (PP) found in oolong tea can inhibit pancreatic lipase activity in vitro, and pilot work indicates that this may reduce postprandial lipemia. Since tea contains caffeine and catechins, the interactions between these ingredients and PP warrant investigation. OBJECTIVES: To assess whether PP ingested alone or with caffeine and catechins lowers postprandial lipemia. METHODS: Fifty healthy adults [mean (SD) age: 26 (7) y; BMI (in kg/m2): 24.0 (2.7); female: n = 16] completed 4 oral lipid tolerance tests in a placebo-controlled randomized, crossover design. Participants ingested 40 g of fat with either 1) placebo, 2) 100 mg PP, 3) 150 mg PP, or 4) 100 mg PP plus 50 mg caffeine and 63 mg catechins (PP + CC). Blood was sampled for 3 h postprandially to assess concentrations of serum and plasma triacylglycerol and plasma markers of lipid (NEFA; glycerol; LDL and HDL cholesterol; and ApoA-I, A-II, B, C-II, C-III, and E) and glucose metabolism (glucose, insulin, and C-peptide). RESULTS: Serum and plasma triacylglycerol concentrations and lipid metabolism variables generally increased following any test drink ingestion (main effect of time, p < 0.001). Nevertheless, for the lipid metabolism responses, there were no statistically significant condition-time interactions and no statistically significant differences in incremental or total area under the curve between conditions, apart from HDL cholesterol (p = 0.021). Ingesting 100 mg PP + CC lowered peak plasma glucose, insulin, and C-peptide concentrations compared with all other conditions 30 min postingestion (p < 0.001), with persistent alterations in glucose concentrations observed for 90 min compared with placebo and 100 mg PP conditions. CONCLUSIONS: PP ingested at doses ≤150 mg does not clearly alter early-phase postprandial triacylglycerol concentrations in healthy adults, irrespective of the presence or absence of caffeine and catechins. Nevertheless, caffeine and catechins added to PP lowered postprandial glucose and insulin concentrations. This trial was registered in ClinicalTrials.gov as NCT03324191 (https://clinicaltrials.gov/ct2/show/NCT03324191).

Phosphate Loading Does not Improve 30-km Cycling Time-Trial Performance in Trained Cyclists.

Phosphate is integral to numerous metabolic processes, several of which strongly predict exercise performance (i.e., cardiac function, oxygen transport, and oxidative metabolism). Evidence regarding phosphate loading is limited and equivocal, at least partly because studies have examined sodium phosphate supplements of varied molar mass (e.g., mono/di/tribasic, dodecahydrate), thus delivering highly variable absolute quantities of phosphate. Within a randomized cross-over design and in a single-blind manner, 16 well-trained cyclists (age 38 ± 16 years, mass 74.3 ± 10.8 kg, training 340 ± 171 min/week; mean ± SD) ingested either 3.5 g/day of dibasic sodium phosphate (Na2HPO4: 24.7 mmol/day phosphate; 49.4 mmol/day sodium) or a sodium chloride placebo (NaCl: 49.4 mmol/day sodium and chloride) for 4 days prior to each of two 30-km time trials, separated by a washout interval of 14 days. There was no evidence of any ergogenic benefit associated with phosphate loading. Time to complete the 30-km time trial did not differ following ingestion of sodium phosphate and sodium chloride (3,059 ± 531 s vs. 2,995 ± 467 s). Accordingly, neither absolute mean power output (221 ± 48 W vs. 226 ± 48 W) nor relative mean power output (3.02 ± 0.78 W/kg vs. 3.08 ± 0.71 W/kg) differed meaningfully between the respective intervention and placebo conditions. Measures of cardiovascular strain and ratings of perceived exertion were very closely matched between treatments (i.e., average heart rate 161 ± 11 beats per minute vs. 159 ± 12 beats per minute; Δ2 beats per minute; and ratings of perceived exertion 18 [14-20] units vs. 17 [14-20] units). In conclusion, supplementing with relatively high absolute doses of phosphate (i.e., >10 mmol daily for 4 days) exerted no ergogenic effects on trained cyclists completing 30-km time trials.

Plasma glucagon-like peptide-1 responses to ingestion of protein with increasing doses of milk minerals rich in calcium.

A high dose of whey protein hydrolysate fed with milk minerals rich in calcium (Capolac®) results in enhanced glucagon-like peptide-1 (GLP-1) concentrations in lean individuals; however, the effect of different calcium doses ingested alongside protein is unknown. The present study assessed the dose response of calcium fed alongside 25 g whey protein hydrolysate on GLP-1 concentrations in individuals with overweight/obesity. Eighteen adults (mean ± sd: 8M/10F, 34 ± 18 years, 28·2 ± 2·9 kgm-2) completed four trials in a randomised, double-blind, crossover design. Participants consumed test solutions consisting of 25 g whey protein hydrolysate (CON), supplemented with 3179 mg (LOW), 6363 mg (MED) or 9547 mg (HIGH) Capolac® on different occasions, separated by at least 48 h. The calcium content of test solutions equated to 65, 892, 1719 and 2547 mg, respectively. Arterialised-venous blood was sampled over 180 min to determine plasma concentrations of GLP-1TOTAL, GLP-17-36amide, insulin, glucose, NEFA, and serum concentrations of calcium and albumin. Ad libitum energy intake was measured at 180 min. Time-averaged incremental AUC (iAUC) for GLP-1TOTAL (pmol·l-1·min-1) did not differ between CON (23 ± 4), LOW (25 ± 6), MED (24 ± 5) and HIGH (24 ± 6). Energy intake (kcal) did not differ between CON (940 ± 387), LOW (884 ± 345), MED (920 ± 334) and HIGH (973 ± 390). Co-ingestion of whey protein hydrolysate with Capolac® does not potentiate GLP-1 release in comparison with whey protein hydrolysate alone. The study was registered at clinical trials (NCT03819972).

Glucose control upon waking is unaffected by hourly sleep fragmentation during the night, but is impaired by morning caffeinated coffee.

Morning coffee is a common remedy following disrupted sleep, yet each factor can independently impair glucose tolerance and insulin sensitivity in healthy adults. Remarkably, the combined effects of sleep fragmentation and coffee on glucose control upon waking per se have never been investigated. In a randomised crossover design, twenty-nine adults (mean age: 21 (sd 1) years, BMI: 24·4 (sd 3·3) kg/m2) underwent three oral glucose tolerance tests (OGTT). One following a habitual night of sleep (Control; in bed, lights-off trying to sleep approximately 23.00-07.00 hours), the others following a night of sleep fragmentation (as Control but waking hourly for 5 min), with and without morning coffee approximately 1 h after waking (approximately 300 mg caffeine as black coffee 30 min prior to OGTT). Individualised peak plasma glucose and insulin concentrations were unaffected by sleep quality but were higher following coffee consumption (mean (normalised CI) for Control, Fragmented and Fragmented + Coffee, respectively; glucose: 8·20 (normalised CI 7·93, 8·47) mmol/l v. 8·23 (normalised CI 7·96, 8·50) mmol/l v. 8·96 (normalised CI 8·70, 9·22) mmol/l; insulin: 265 (normalised CI 247, 283) pmol/l; and 235 (normalised CI 218, 253) pmol/l; and 310 (normalised CI 284, 337) pmol/l). Likewise, incremental AUC for plasma glucose was higher in the Fragmented + Coffee trial compared with Fragmented. Whilst sleep fragmentation did not alter glycaemic or insulinaemic responses to morning glucose ingestion, if a strong caffeinated coffee is consumed, then a reduction in glucose tolerance can be expected.

Pectin-Alginate Does Not Further Enhance Exogenous Carbohydrate Oxidation in Running.

PURPOSE: Maximizing carbohydrate availability is important for many endurance events. Combining pectin and sodium alginate with ingested maltodextrin-fructose (MAL + FRU + PEC + ALG) has been suggested to enhance carbohydrate delivery via hydrogel formation, but the influence on exogenous carbohydrate oxidation remains unknown. The primary aim of this study was to assess the effects of MAL + FRU + PEC + ALG on exogenous carbohydrate oxidation during exercise compared with a maltodextrin-fructose mixture (MAL + FRU). MAL + FRU has been well established to increase exogenous carbohydrate oxidation during cycling compared with glucose-based carbohydrates (MAL + GLU). However, much evidence focuses on cycling, and direct evidence in running is lacking. Therefore, a secondary aim was to compare exogenous carbohydrate oxidation rates with MAL + FRU versus MAL + GLU during running. METHODS: Nine trained runners completed two trials (MAL + FRU and MAL + FRU + PEC + ALG) in a double-blind, randomized crossover design. A subset (n = 7) also completed a MAL + GLU trial to address the secondary aim, and a water trial to establish background expired CO2 enrichment. Participants ran at 60% V˙O2peak for 120 min while ingesting either water only or carbohydrate solutions at a rate of 1.5 g carbohydrate per minute. RESULTS: At the end of 120 min of exercise, exogenous carbohydrate oxidation rates were 0.9 (SD 0.5) g·min with MAL + GLU ingestion. MAL + FRU ingestion increased exogenous carbohydrate oxidation rates to 1.1 (SD 0.3) g·min (P = 0.038), with no further increase with MAL + FRU + PEC + ALG ingestion (1.1 (SD 0.3) g·min; P = 1.0). No time-treatment interaction effects were observed for plasma glucose, lactate, insulin, or nonesterified fatty acids, or for ratings of perceived exertion or gastrointestinal symptoms (all, P > 0.05). CONCLUSION: To maximize exogenous carbohydrate oxidation during moderate-intensity running, athletes may benefit from consuming glucose(polymer)-fructose mixtures over glucose-based carbohydrates alone, but the addition of pectin and sodium alginate offers no further benefit.

Co-ingestion of whey protein hydrolysate with milk minerals rich in calcium potently stimulates glucagon-like peptide-1 secretion: an RCT in healthy adults.

PURPOSE: To examine whether calcium type and co-ingestion with protein alter gut hormone availability. METHODS: Healthy adults aged 26 ± 7 years (mean ± SD) completed three randomized, double-blind, crossover studies. In all studies, arterialized blood was sampled postprandially over 120 min to determine GLP-1, GIP and PYY responses, alongside appetite ratings, energy expenditure and blood pressure. In study 1 (n = 20), three treatments matched for total calcium content (1058 mg) were compared: calcium citrate (CALCITR); milk minerals rich in calcium (MILK MINERALS); and milk minerals rich in calcium plus co-ingestion of 50 g whey protein hydrolysate (MILK MINERALS + PROTEIN). In study 2 (n = 6), 50 g whey protein hydrolysate (PROTEIN) was compared to MILK MINERALS + PROTEIN. In study 3 (n = 6), MILK MINERALS was compared to the vehicle of ingestion (water plus sucralose; CONTROL). RESULTS: MILK MINERALS + PROTEIN increased GLP-1 incremental area under the curve (iAUC) by ~ ninefold (43.7 ± 11.1 pmol L-1 120 min; p < 0.001) versus both CALCITR and MILK MINERALS, with no difference detected between CALCITR (6.6 ± 3.7 pmol L-1 120 min) and MILK MINERALS (5.3 ± 3.5 pmol L-1 120 min; p > 0.999). MILK MINERALS + PROTEIN produced a GLP-1 iAUC ~ 25% greater than PROTEIN (p = 0.024; mean difference: 9.1 ± 6.9 pmol L-1 120 min), whereas the difference between MILK MINERALS versus CONTROL was small and non-significant (p = 0.098; mean difference: 4.2 ± 5.1 pmol L-1 120 min). CONCLUSIONS: When ingested alone, milk minerals rich in calcium do not increase GLP-1 secretion compared to calcium citrate. Co-ingesting high-dose whey protein hydrolysate with milk minerals rich in calcium increases postprandial GLP-1 concentrations to some of the highest physiological levels ever reported. Registered at ClinicalTrials.gov: NCT03232034, NCT03370484, NCT03370497.

Oxidative stress, inflammation and recovery of muscle function after damaging exercise: effect of 6-week mixed antioxidant supplementation.

There is no consensus regarding the effects of mixed antioxidant vitamin C and/or vitamin E supplementation on oxidative stress responses to exercise and restoration of muscle function. Thirty-eight men were randomly assigned to receive either placebo group (n = 18) or mixed antioxidant (primarily vitamin C & E) supplements (n = 20) in a double-blind manner. After 6 weeks, participants performed 90 min of intermittent shuttle-running. Peak isometric torque of the knee flexors/extensors and range of motion at this joint were determined before and after exercise, with recovery of these variables tracked for up to 168 h post-exercise. Antioxidant supplementation elevated pre-exercise plasma vitamin C (93 ± 8 µmol l(-1)) and vitamin E (11 ± 3 µmol l(-1)) concentrations relative to baseline (P < 0.001) and the placebo group (P ≤ 0.02). Exercise reduced peak isometric torque (i.e. 9-19% relative to baseline; P ≤ 0.001), which persisted for the first 48 h of recovery with no difference between treatment groups. In contrast, changes in the urine concentration of F(2)-isoprostanes responded differently to each treatment (P = 0.04), with a tendency for higher concentrations after 48 h of recovery in the supplemented group (6.2 ± 6.1 vs. 3.7 ± 3.4 ng ml(-1)). Vitamin C & E supplementation also affected serum cortisol concentrations, with an attenuated increase from baseline to the peak values reached after 1 h of recovery compared with the placebo group (P = 0.02) and serum interleukin-6 concentrations were higher after 1 h of recovery in the antioxidant group (11.3 ± 3.4 pg ml(-1)) than the placebo group (6.2 ± 3.8 pg ml(-1); P = 0.05). Combined vitamin C & E supplementation neither reduced markers of oxidative stress or inflammation nor did it facilitate recovery of muscle function after exercise-induced muscle damage.

Short-term recovery from prolonged exercise: exploring the potential for protein ingestion to accentuate the benefits of carbohydrate supplements.

This review considers aspects of the optimal nutritional strategy for recovery from prolonged moderate to high intensity exercise. Dietary carbohydrate represents a central component of post-exercise nutrition. Therefore, carbohydrate should be ingested as early as possible in the post-exercise period and at frequent (i.e. 15- to 30-minute) intervals throughout recovery to maximize the rate of muscle glycogen resynthesis. Solid and liquid carbohydrate supplements or whole foods can achieve this aim with equal effect but should be of high glycaemic index and ingested following the feeding schedule described above at a rate of at least 1 g/kg/h in order to rapidly and sufficiently increase both blood glucose and insulin concentrations throughout recovery. Adding ≥0.3 g/kg/h of protein to a carbohydrate supplement results in a synergistic increase in insulin secretion that can, in some circumstances, accelerate muscle glycogen resynthesis. Specifically, if carbohydrate has not been ingested in quantities sufficient to maximize the rate of muscle glycogen resynthesis, the inclusion of protein may at least partially compensate for the limited availability of ingested carbohydrate. Some studies have reported improved physical performance with ingestion of carbohydrate-protein mixtures, both during exercise and during recovery prior to a subsequent exercise test. While not all of the evidence supports these ergogenic benefits, there is clearly the potential for improved performance under certain conditions, e.g. if the additional protein increases the energy content of a supplement and/or the carbohydrate fraction is ingested at below the recommended rate. The underlying mechanism for such effects may be partly due to increased muscle glycogen resynthesis during recovery, although there is varied support for other factors such as an increased central drive to exercise, a blunting of exercise-induced muscle damage, altered metabolism during exercise subsequent to recovery, or a combination of these mechanisms.

Isocaloric carbohydrate versus carbohydrate-protein ingestion and cycling time-trial performance.

This study was designed to compare the effects of energy-matched carbohydrate (CHO) and carbohydrate-protein (CHO-PRO) supplements on cycling time-trial performance. Twelve competitive male cyclists and triathletes each completed 2 trials in a randomized and counterbalanced order that were separated by 5-10 d and applied in a double-blind manner. Participants performed a 45-min variable-intensity exercise protocol on a cycle ergometer while ingesting either a 9% CHO solution or a mixture of 6.8% CHO plus 2.2% protein in volumes providing 22 kJ/kg body mass. Participants were then asked to cycle 6 km in the shortest time possible. Blood glucose and lactate concentrations were measured every 15 min during exercise, along with measures of substrate oxidation via indirect calorimetry, heart rate, and ratings of perceived exertion. Mean time to complete the 6-km time trial was 433 + or - 21 s in CHO trials and 438 + or - 22 s in CHO-PRO trials, which represents a 0.94% (CI: 0.01, 1.86) decrement in performance with the inclusion of protein (p = .048). However, no other variable measured in this study was significantly different between trials. Reducing the quantity of CHO included in a supplement and replacing it with protein may not represent an effective nutritional strategy when the supplement is ingested during exercise. This may reflect the central ergogenic influence of exogenous CHO during such activity.