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Food & Function Mar 2016A protein consists of amino acids (AA) linked by peptide bonds. Dietary protein is hydrolyzed by proteases and peptidases to generate AA, dipeptides, and tripeptides in... (Review)
Review
A protein consists of amino acids (AA) linked by peptide bonds. Dietary protein is hydrolyzed by proteases and peptidases to generate AA, dipeptides, and tripeptides in the lumen of the gastrointestinal tract. These digestion products are utilized by bacteria in the small intestine or absorbed into enterocytes. AA that are not degraded by the small intestine enter the portal vein for protein synthesis in skeletal muscle and other tissues. AA are also used for cell-specific production of low-molecular-weight metabolites with enormous physiological importance. Thus, protein undernutrition results in stunting, anemia, physical weakness, edema, vascular dysfunction, and impaired immunity. Based on short-term nitrogen balance studies, the Recommended Dietary Allowance of protein for a healthy adult with minimal physical activity is currently 0.8 g protein per kg body weight (BW) per day. To meet the functional needs such as promoting skeletal-muscle protein accretion and physical strength, dietary intake of 1.0, 1.3, and 1.6 g protein per kg BW per day is recommended for individuals with minimal, moderate, and intense physical activity, respectively. Long-term consumption of protein at 2 g per kg BW per day is safe for healthy adults, and the tolerable upper limit is 3.5 g per kg BW per day for well-adapted subjects. Chronic high protein intake (>2 g per kg BW per day for adults) may result in digestive, renal, and vascular abnormalities and should be avoided. The quantity and quality of protein are the determinants of its nutritional values. Therefore, adequate consumption of high-quality proteins from animal products (e.g., lean meat and milk) is essential for optimal growth, development, and health of humans.
Topics: Amino Acids; Dietary Proteins; Growth and Development; Humans; Malnutrition; Muscle Weakness; Nutritive Value; Recommended Dietary Allowances
PubMed: 26797090
DOI: 10.1039/c5fo01530h -
Current Protein & Peptide Science 2019Dietary protein and its metabolites, amino acids, are essential nutrients for humans and animals. Accumulated research has revealed that the gut microbiota mediate the... (Review)
Review
Dietary protein and its metabolites, amino acids, are essential nutrients for humans and animals. Accumulated research has revealed that the gut microbiota mediate the crosstalk between protein metabolism and host immune response. Gut microbes are involved in the digestion, absorption, metabolism and transformation process of dietary protein in the gastrointestinal tract. Amino acids can be metabolized into numerous microbial metabolites, and these metabolites participate in various physiological functions related to host health and diseases. The components of dietary protein impact the gut microbiota composition and microbial metabolites. The source, concentration, and amino acid balance of dietary protein are primary factors which contribute to the composition, structure and function of gut microbes. A suitable ratio between protein and carbohydrate or even a low protein diet is recommended over a diet with protein in excess of requirements. Greater levels and undigested protein lead to an increase of pathogenic microorganism with associated higher risk of metabolic diseases. Herein, the crosstalk between dietary protein and gut microbiota composition and function is summarized, which will help to reveal the potential mechanism of gut microbes on the gastrointestinal tract health.
Topics: Animals; Diet; Dietary Proteins; Gastrointestinal Microbiome; Gastrointestinal Tract; Humans; Intestinal Absorption; Proteolysis
PubMed: 29756574
DOI: 10.2174/1389203719666180514145437 -
Journal of Sports Sciences 2011Opinion on the role of protein in promoting athletic performance is divided along the lines of how much aerobic-based versus resistance-based activity the athlete... (Review)
Review
Opinion on the role of protein in promoting athletic performance is divided along the lines of how much aerobic-based versus resistance-based activity the athlete undertakes. Athletes seeking to gain muscle mass and strength are likely to consume higher amounts of dietary protein than their endurance-trained counterparts. The main belief behind the large quantities of dietary protein consumption in resistance-trained athletes is that it is needed to generate more muscle protein. Athletes may require protein for more than just alleviation of the risk for deficiency, inherent in the dietary guidelines, but also to aid in an elevated level of functioning and possibly adaptation to the exercise stimulus. It does appear, however, that there is a good rationale for recommending to athletes protein intakes that are higher than the RDA. Our consensus opinion is that leucine, and possibly the other branched-chain amino acids, occupy a position of prominence in stimulating muscle protein synthesis; that protein intakes in the range of 1.3-1.8 g · kg(-1) · day(-1) consumed as 3-4 isonitrogenous meals will maximize muscle protein synthesis. These recommendations may also be dependent on training status: experienced athletes would require less, while more protein should be consumed during periods of high frequency/intensity training. Elevated protein consumption, as high as 1.8-2.0 g · kg(-1) · day(-1) depending on the caloric deficit, may be advantageous in preventing lean mass losses during periods of energy restriction to promote fat loss.
Topics: Adaptation, Physiological; Amino Acids; Athletic Performance; Body Composition; Diet; Dietary Proteins; Energy Intake; Exercise; Guidelines as Topic; Humans; Muscle Proteins; Nutritional Requirements; Physical Education and Training; Protein Biosynthesis; Protein-Energy Malnutrition; Resistance Training; Sports
PubMed: 22150425
DOI: 10.1080/02640414.2011.619204 -
The American Journal of Clinical... Jun 2017: Considerable attention has recently focused on dietary protein's role in the mature skeleton, prompted partly by an interest in nonpharmacologic approaches to maintain... (Meta-Analysis)
Meta-Analysis Review
: Considerable attention has recently focused on dietary protein's role in the mature skeleton, prompted partly by an interest in nonpharmacologic approaches to maintain skeletal health in adult life. The aim was to conduct a systematic review and meta-analysis evaluating the effects of dietary protein intake alone and with calcium with or without vitamin D (Ca±D) on bone health measures in adults. Searches across 5 databases were conducted through October 2016 including randomized controlled trials (RCTs) and prospective cohort studies examining ) the effects of "high versus low" protein intake or ) dietary protein's synergistic effect with Ca±D intake on bone health outcomes. Two investigators independently conducted abstract and full-text screenings, data extractions, and risk of bias (ROB) assessments. Strength of evidence was rated by group consensus. Random-effects meta-analyses for outcomes with ≥4 RCTs were performed. Sixteen RCTs and 20 prospective cohort studies were included in the systematic review. Overall ROB was medium. Moderate evidence suggested that higher protein intake may have a protective effect on lumbar spine (LS) bone mineral density (BMD) compared with lower protein intake (net percentage change: 0.52%; 95% CI: 0.06%, 0.97%, : 0%; = 5) but no effect on total hip (TH), femoral neck (FN), or total body BMD or bone biomarkers. Limited evidence did not support an effect of protein with Ca±D on LS BMD, TH BMD, or forearm fractures; there was insufficient evidence for FN BMD and overall fractures. Current evidence shows no adverse effects of higher protein intakes. Although there were positive trends on BMD at most bone sites, only the LS showed moderate evidence to support benefits of higher protein intake. Studies were heterogeneous, and confounding could not be excluded. High-quality, long-term studies are needed to clarify dietary protein's role in bone health. This trial was registered at www.crd.york.ac.uk as CRD42015017751.
Topics: Bone Density; Bone Density Conservation Agents; Calcium; Calcium, Dietary; Dietary Proteins; Female; Fractures, Bone; Humans; Lumbar Vertebrae; Male; Osteoporosis; Vitamin D
PubMed: 28404575
DOI: 10.3945/ajcn.116.145110 -
Annual Review of Nutrition 2009The role of dietary protein in weight loss and weight maintenance encompasses influences on crucial targets for body weight regulation, namely satiety, thermogenesis,... (Review)
Review
The role of dietary protein in weight loss and weight maintenance encompasses influences on crucial targets for body weight regulation, namely satiety, thermogenesis, energy efficiency, and body composition. Protein-induced satiety may be mainly due to oxidation of amino acids fed in excess, especially in diets with "incomplete" proteins. Protein-induced energy expenditure may be due to protein and urea synthesis and to gluconeogenesis; "complete" proteins having all essential amino acids show larger increases in energy expenditure than do lower-quality proteins. With respect to adverse effects, no protein-induced effects are observed on net bone balance or on calcium balance in young adults and elderly persons. Dietary protein even increases bone mineral mass and reduces incidence of osteoporotic fracture. During weight loss, nitrogen intake positively affects calcium balance and consequent preservation of bone mineral content. Sulphur-containing amino acids cause a blood pressure-raising effect by loss of nephron mass. Subjects with obesity, metabolic syndrome, and type 2 diabetes are particularly susceptible groups. This review provides an overview of how sustaining absolute protein intake affects metabolic targets for weight loss and weight maintenance during negative energy balance, i.e., sustaining satiety and energy expenditure and sparing fat-free mass, resulting in energy inefficiency. However, the long-term relationship between net protein synthesis and sparing fat-free mass remains to be elucidated.
Topics: Dietary Proteins; Energy Intake; Energy Metabolism; Gluconeogenesis; Humans; Obesity; Satiety Response; Thermogenesis; Weight Loss
PubMed: 19400750
DOI: 10.1146/annurev-nutr-080508-141056 -
Kidney360 Aug 2023It has been estimated that over a fifth of deaths worldwide can be attributed to dietary risk factors. A particularly serious condition is salt-sensitive (SS)... (Review)
Review
It has been estimated that over a fifth of deaths worldwide can be attributed to dietary risk factors. A particularly serious condition is salt-sensitive (SS) hypertension and renal damage, participants of which demonstrate increased morbidity and mortality. Notably, a large amount of evidence from humans and animals has demonstrated that other components of the diet can also modulate hypertension and associated end-organ damage. Evidence presented in this review provides support for the view that immunity and inflammation serve to amplify the development of SS hypertension and leads to malignant disease accompanied by tissue damage. Interestingly, SS hypertension is modulated by changes in dietary protein intake, which also influences immune mechanisms. Together, the evidence presented in this review from animal and human studies indicates that changes in dietary protein source have profound effects on the gut microbiota, microbiota-derived metabolites, gene expression, immune cell activation, the production of cytokines and other factors, and the development of SS hypertension and kidney damage.
Topics: Animals; Humans; Dietary Proteins; Blood Pressure; Kidney Diseases; Hypertension; Kidney; Sodium Chloride, Dietary
PubMed: 37424061
DOI: 10.34067/KID.0000000000000210 -
Nutrients Jan 2022The effect of diet on the composition of gut microbiota and the consequent impact on disease risk have been of expanding interest. The present review focuses on current... (Review)
Review
The effect of diet on the composition of gut microbiota and the consequent impact on disease risk have been of expanding interest. The present review focuses on current insights of changes associated with dietary protein-induced gut microbial populations and examines their potential roles in the metabolism, health, and disease of animals. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol was used, and 29 highly relevant articles were obtained, which included 6 mouse studies, 7 pig studies, 15 rat studies, and 1 in vitro study. Analysis of these studies indicated that several factors, such as protein source, protein content, dietary composition (such as carbohydrate content), glycation of protein, processing factors, and protein oxidation, affect the digestibility and bioavailability of dietary proteins. These factors can influence protein fermentation, absorption, and functional properties in the gut and, consequently, impact the composition of gut microbiota and affect human health. While gut microbiota can release metabolites that can affect host physiology either positively or negatively, the selection of quality of protein and suitable food processing conditions are important to have a positive effect of dietary protein on gut microbiota and human health.
Topics: Animals; Diet; Dietary Proteins; Fermentation; Food Handling; Gastrointestinal Microbiome; Mice; Rats; Swine
PubMed: 35276812
DOI: 10.3390/nu14030453 -
The American Journal of Clinical... Aug 2020Protein ingestion increases skeletal muscle protein synthesis rates during recovery from endurance exercise. (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Protein ingestion increases skeletal muscle protein synthesis rates during recovery from endurance exercise.
OBJECTIVES
We aimed to determine the effect of graded doses of dietary protein co-ingested with carbohydrate on whole-body protein metabolism, and skeletal muscle myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis rates during recovery from endurance exercise.
METHODS
In a randomized, double-blind, parallel-group design, 48 healthy, young, endurance-trained men (mean ± SEM age: 27 ± 1 y) received a primed continuous infusion of l-[ring-2H5]-phenylalanine, l-[ring-3,5-2H2]-tyrosine, and l-[1-13C]-leucine and ingested 45 g carbohydrate with either 0 (0 g PRO), 15 (15 g PRO), 30 (30 g PRO), or 45 (45 g PRO) g intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled milk protein after endurance exercise. Blood and muscle biopsy samples were collected over 360 min of postexercise recovery to assess whole-body protein metabolism and both MyoPS and MitoPS rates.
RESULTS
Protein intake resulted in ∼70%-74% of the ingested protein-derived phenylalanine appearing in the circulation. Whole-body net protein balance increased dose-dependently after ingestion of 0, 15, 30, or 45 g protein (mean ± SEM: -0.31± 0.16, 5.08 ± 0.21, 10.04 ± 0.30, and 13.49 ± 0.55 μmol phenylalanine · kg-1 · h-1, respectively; P < 0.001). 30 g PRO stimulated a ∼46% increase in MyoPS rates (%/h) compared with 0 g PRO and was sufficient to maximize MyoPS rates after endurance exercise. MitoPS rates were not increased after protein ingestion; however, incorporation of dietary protein-derived l-[1-13C]-phenylalanine into de novo mitochondrial protein increased dose-dependently after ingestion of 15, 30, and 45 g protein at 360 min postexercise (0.018 ± 0.002, 0.034 ± 0.002, and 0.046 ± 0.003 mole percentage excess, respectively; P < 0.001).
CONCLUSIONS
Protein ingested after endurance exercise is efficiently digested and absorbed into the circulation. Whole-body net protein balance and dietary protein-derived amino acid incorporation into mitochondrial protein respond to increasing protein intake in a dose-dependent manner. Ingestion of 30 g protein is sufficient to maximize MyoPS rates during recovery from a single bout of endurance exercise.This trial was registered at trialregister.nl as NTR5111.
Topics: Adult; Amino Acids; Dietary Proteins; Double-Blind Method; Endurance Training; Exercise; Humans; Male; Muscle Proteins; Muscle, Skeletal
PubMed: 32359142
DOI: 10.1093/ajcn/nqaa073 -
The Proceedings of the Nutrition Society May 2021Dietary protein is a pre-requisite for the maintenance of skeletal muscle mass; stimulating increases in muscle protein synthesis (MPS), via essential amino acids (EAA),... (Review)
Review
Dietary protein is a pre-requisite for the maintenance of skeletal muscle mass; stimulating increases in muscle protein synthesis (MPS), via essential amino acids (EAA), and attenuating muscle protein breakdown, via insulin. Muscles are receptive to the anabolic effects of dietary protein, and in particular the EAA leucine, for only a short period (i.e. about 2-3 h) in the rested state. Thereafter, MPS exhibits tachyphylaxis despite continued EAA availability and sustained mechanistic target of rapamycin complex 1 signalling. Other notable characteristics of this 'muscle full' phenomenon include: (i) it cannot be overcome by proximal intake of additional nutrient signals/substrates regulating MPS; meaning a refractory period exists before a next stimulation is possible, (ii) it is refractory to pharmacological/nutraceutical enhancement of muscle blood flow and thus is not induced by muscle hypo-perfusion, (iii) it manifests independently of whether protein intake occurs in a bolus or intermittent feeding pattern, and (iv) it does not appear to be dependent on protein dose per se. Instead, the main factor associated with altering muscle full is physical activity. For instance, when coupled to protein intake, resistance exercise delays the muscle full set-point to permit additional use of available EAA for MPS to promote muscle remodelling/growth. In contrast, ageing is associated with blunted MPS responses to protein/exercise (anabolic resistance), while physical inactivity (e.g. immobilisation) induces a premature muscle full, promoting muscle atrophy. It is crucial that in catabolic scenarios, anabolic strategies are sought to mitigate muscle decline. This review highlights regulatory protein turnover interactions by dietary protein, exercise, ageing and physical inactivity.
Topics: Aging; Dietary Proteins; Exercise; Humans; Muscle, Skeletal; Proteostasis; Sedentary Behavior
PubMed: 33023679
DOI: 10.1017/S0029665120007879 -
International Journal of Sport... Apr 2014Caloric restriction occurs when athletes attempt to reduce body fat or make weight. There is evidence that protein needs increase when athletes restrict calories or have... (Review)
Review
UNLABELLED
Caloric restriction occurs when athletes attempt to reduce body fat or make weight. There is evidence that protein needs increase when athletes restrict calories or have low body fat.
PURPOSE
The aims of this review were to evaluate the effects of dietary protein on body composition in energy-restricted resistance-trained athletes and to provide protein recommendations for these athletes.
METHODS
Database searches were performed from earliest record to July 2013 using the terms protein, and intake, or diet, and weight, or train, or restrict, or energy, or strength, and athlete. Studies (N = 6) needed to use adult (≥ 18 yrs), energy-restricted, resistance-trained (> 6 months) humans of lower body fat (males ≤ 23% and females ≤ 35%) performing resistance training. Protein intake, fat free mass (FFM) and body fat had to be reported.
RESULTS
Body fat percentage decreased (0.5-6.6%) in all study groups (N = 13) and FFM decreased (0.3-2.7kg) in nine of 13. Six groups gained, did not lose, or lost nonsignificant amounts of FFM. Five out of these six groups were among the highest in body fat, lowest in caloric restriction, or underwent novel resistance training stimuli. However, the one group that was not high in body fat that underwent substantial caloric restriction, without novel training stimuli, consumed the highest protein intake out of all the groups in this review (2.5-2.6g/kg).
CONCLUSIONS
Protein needs for energy-restricted resistance-trained athletes are likely 2.3-3.1g/kg of FFM scaled upwards with severity of caloric restriction and leanness.
Topics: Adipose Tissue; Athletes; Body Composition; Body Fluid Compartments; Body Weight; Caloric Restriction; Dietary Proteins; Energy Intake; Female; Humans; Male; Nutritional Requirements; Resistance Training; Sports; Sports Nutritional Physiological Phenomena
PubMed: 24092765
DOI: 10.1123/ijsnem.2013-0054