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Background: Ingestion of protein concentrates or isolates increases muscle protein synthesis rates in young and older adults. There is far less information available on the anabolic response following the ingestion of dairy wholefoods, which are commonly consumed in a normal diet. Objectives: This study investigates whether ingestion of 30 g protein provided as quark increases muscle protein synthesis rates at rest and whether muscle protein synthesis rates are further increased after resistance exercise in young and older adult males. Methods: In this parallel-group intervention trial, 14 young (18–35 y) and 15 older (65–85 y) adult males ingested 30 g protein provided as quark after a single-legged bout of resistance exercise on leg press and leg extension machines. Primed, continuous intravenous L-[ring- 13C 6]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4-h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data represent means ± SDs; η 2 was used to measure the effect size. Results: Plasma total amino acid and leucine concentrations increased after quark ingestion in both groups (both time: P < 0.001; η 2 > 0.8), with no differences between groups (time × group: P = 0.127 and P = 0.172, respectively; η 2−1) and older adult males (from 0.036 ± 0.011 to 0.062 ± 0.013 %·h −1), with a further increase in the exercised leg (to 0.071 ± 0.023 %·h −1 and to 0.078 ± 0.019 %·h −1, respectively; condition: P < 0.001; η 2 = 0.716), with no differences between groups (condition × group: P = 0.747; η 2 = 0.011). Conclusions: Quark ingestion increases muscle protein synthesis rates at rest with a further increase following exercise in both young and older adult males. The postprandial muscle protein synthetic response following quark ingestion does not differ between healthy young and older adult males when an ample amount of protein is ingested. This trial was registered at the Dutch Trial register, which is accessible via trialsearch.who.int www.trialregister.nl as NL8403.

Rationale: Dietary protein may attenuate the muscle atrophy experienced by patients in the ICU, yet protein handling is poorly understood. Objectives: To quantify protein digestion and amino acid absorption and fasting and postprandial myofibrillar protein synthesis during critical illness. Methods: Fifteen mechanically ventilated adults (12 male; aged 50 ± 17 yr; body mass index, 27 ± 5 kg⋅m-2) and 10 healthy control subjects (6 male; 54 ± 23 yr; body mass index, 27 ± 4 kg⋅m-2) received a primed intravenous L-[ring-2H5]-phenylalanine, L-[3,5-2H2]-tyrosine, and L-[1-13C]-leucine infusion over 9.5 hours and a duodenal bolus of intrinsically labeled (L-[1-13C]-phenylalanine and L-[1-13C]-leucine) intact milk protein (20 g protein) over 60 minutes. Arterial blood and muscle samples were taken at baseline (fasting) and for 6 hours following duodenal protein administration. Data are mean ± SD, analyzed with two-way repeated measures ANOVA and independent samples t test. Measurements and Main Results: Fasting myofibrillar protein synthesis rates did not differ between ICU patients and healthy control subjects (0.023 ± 0.013% h-1 vs. 0.034 ± 0.016% h-1; P = 0.077). After protein administration, plasma amino acid availability did not differ between groups (ICU patients, 54.2 ± 9.1%, vs. healthy control subjects, 61.8 ± 13.1%; P = 0.12), and myofibrillar protein synthesis rates increased in both groups (0.028 ± 0.010% h-1 vs. 0.043 ± 0.018% h-1; main time effect P = 0.046; P-interaction = 0.584) with lower rates in ICU patients than in healthy control subjects (main group effect P = 0.001). Incorporation of protein-derived phenylalanine into myofibrillar protein was ∼60% lower in ICU patients (0.007 ± 0.007 mol percent excess vs. 0.017 ± 0.009 mol percent excess; P = 0.007). Conclusions: The capacity for critically ill patients to use ingested protein for muscle protein synthesis is markedly blunted despite relatively normal protein digestion and amino acid absorption.

Background Protein ingestion increases muscle protein synthesis rates. The food matrix in which protein is provided can strongly modulate the postprandial muscle protein synthetic response. So far, the muscle protein synthetic response to the ingestion of whole foods remains largely unexplored. Objectives To compare the impact of ingesting 30 g protein provided as milk protein or cheese on postprandial plasma amino acid concentrations and muscle protein synthesis rates at rest and during recovery from exercise in vivo in young males. Methods In this randomized, parallel-group intervention trial, 20 healthy males aged 18-35 y ingested 30 g protein provided as cheese or milk protein concentrate following a single-legged resistance-type exercise session consisting of 12 sets of leg press and leg extension exercises. Primed, continuous intravenous L-[ring-C-13(6)]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4-h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data were analyzed using repeated measures Time x Group (x Leg) ANOVA. Results Plasma total amino acid concentrations increased after protein ingestion (Time: P < 0.001), with 38% higher peak concentrations following milk protein than cheese ingestion (Time x Group: P < 0.001). Muscle protein synthesis rates increased following both cheese and milk protein ingestion from 0.037 +/- 0.014 to 0.055 +/- 0.018%center dot h(-1) and 0.034 +/- 0.008 to 0.056 +/- 0.010%center dot h(-1) at rest and even more following exercise from 0.031 +/- 0.010 to 0.067 +/- 0.013%center dot h(-1) and 0.030 +/- 0.008 to 0.063 +/- 0.010%center dot h(-1), respectively (Time: all P < 0.05; Time x Leg: P = 0.002), with no differences between cheese and milk protein ingestion (Time x Group: both P > 0.05). Conclusion Cheese ingestion increases muscle protein synthesis rates both at rest and during recovery from exercise. The postprandial muscle protein synthetic response to the ingestion of cheese or milk protein does not differ when 30 g protein is ingested at rest or during recovery from exercise in healthy, young males.

INTRODUCTION: Plant-derived proteins have received considerable attention as an alternative to animal based proteins and are now frequently used in both plant-based diets and sports nutrition products. However, little information is available on the anabolic properties of potato-derived protein. This study compares muscle protein synthesis rates following the ingestion of 30 g potato protein versus 30 g milk protein at rest and during recovery from a single bout of resistance exercise in healthy, young males.METHODS: In a randomized, double blind, parallel-group design, 24 healthy young males (24 ± 4y) received primed continuous L-[ring-13C6]-phenylalanine infusions while ingesting 30 g potato derived protein or 30 g milk protein following a single bout of unilateral resistance exercise. Blood and muscle biopsies were collected for 5 hours following protein ingestion to assess post-prandial plasma amino acid profiles and mixed muscle protein synthesis rates at rest and during recovery from exercise.RESULTS: Ingestion of both potato and milk protein increased mixed muscle protein synthesis rates when compared to basal post-absorptive values (from 0.020 ± 0.011 to 0.053 ± 0.017 %·h-1 and from 0.021 ± 0.014 to 0.050 ± 0.012 %·h-1, respectively (P < 0.001)), with no differences between treatments (P = 0.54). In the exercised leg, mixed muscle protein synthesis rates increased to 0.069 ± 0.019 and 0.064 ± 0.015 %·h-1 after ingesting potato and milk protein, respectively (P < 0.001), with no differences between treatments (P = 0.52). The muscle protein synthetic response was greater in the exercised compared with the resting leg (P < 0.05).CONCLUSIONS: Ingestion of 30 g potato protein concentrate increases muscle protein synthesis rates at rest and during recovery from exercise in healthy, young males. Muscle protein synthesis rates following the ingestion of 30 g potato protein do not differ from rates observed after ingesting an equivalent amount of milk protein.

Protein degradation rates were assessed by the excretion of Nt-methylhistidine (NtMH) in four strains of mature chickens, two White Leghorns and two broilers (dwarf and normal), fed on diets containing two levels of dietary protein. Over 0.9 of labelled NtMH was recovered within 7 d of injection from three White Leghorn, three dwarf and three normal broiler males. Protein degradation, measured by NtMH output, was related to adult body-weight by the power 0.71 and strain intercepts were significantly different. Strain differences disappeared when the rate of output of NtMH per unit lean was evaluated. The rate of output of NtMH per unit muscle was higher in birds fed on a low-protein diet of 100 g crude protein (nitrogen x 6.25; CP)/kg compared with males fed on 150 g CP/kg. It was concluded that the lower rate of protein degradation in broiler compared with layer strains at young ages is related to increased adult body-weight in agreement with well-established biological principles.

BACKGROUND: Ethanol can account for up to 10 percent of the energy intake of persons who consume moderate amounts of ethanol. Its effect on energy metabolism, however, is not known. METHODS: We studied the effect of ethanol on 24-hour substrate-oxidation rates in eight normal men during two 48-hour sessions in an indirect-calorimetry chamber. In each session, the first 24 hours served as the control period. On the second day of one session, an additional 25 percent of the total energy requirement was added as ethanol (mean [+/- SD], 96 +/- 4 g per day); during the other session, 25 percent of the total energy requirement was replaced by ethanol, which was isocalorically substituted for lipids and carbohydrates. RESULTS: Both the addition of ethanol and the isocaloric substitution of ethanol for other foods reduced 24-hour lipid oxidation. The respective mean (+/- SE) decreases were 49.4 +/- 6.7 and 44.1 +/- 9.3 g per day (i.e., reductions of 36 +/- 3 percent and 31 +/- 7 percent from the oxidation rate during the control day; P less than 0.001 and P less than 0.0025). This effect occurred only during the daytime period (8:30 a.m. to 11:30 p.m.), when ethanol was consumed and metabolized. Neither the addition of ethanol to the diet nor the isocaloric substitution of ethanol for other foods significantly altered the oxidation of carbohydrate or protein. Both regimens including ethanol produced an increase in 24-hour energy expenditure (7 +/- 1 percent with the addition of ethanol, P less than 0.001; 4 +/- 1 percent with the substitution of ethanol for other energy sources, P less than 0.025). CONCLUSIONS: Ethanol, either added to the diet or substituted for other foods, increases 24-hour energy expenditure and decreases lipid oxidation. Habitual consumption of ethanol in excess of energy needs probably favors lipid storage and weight gain.

Gastric bypass surgery leads to profound changes in the secretion of gut hormones with effects on metabolism, appetite, and food intake. Here, we discuss their contributions to the improvement in glucose tolerance and the weight loss that results from the operations. We find that the improved glucose tolerance is due the following events: a negative energy balance and resulting weight loss, which improve first hepatic and later peripheral insulin sensitivity, in combination with increased postprandial insulin secretion elicited particularly by exaggerated glucagon-like peptide-1 responses. The weight loss is due to loss of appetite resulting in reduced energy intake, and we find it probable that this process is driven by exaggerated secretion of appetite-regulating gut hormones including, but probably not limited to, glucagon-like peptide-1 and peptide-YY. The increased secretion is due to an accelerated exposure to and absorption of nutrients in the small intestine. This places the weight loss and the gut hormones in key positions with respect to the metabolic improvements after bypass surgery.