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British Journal of Sports Medicine Mar 2018We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced... (Meta-Analysis)
Meta-Analysis Review
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.
OBJECTIVE
We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength.
DATA SOURCES
A systematic search of Medline, Embase, CINAHL and SportDiscus.
ELIGIBILITY CRITERIA
Only randomised controlled trials with RET ≥6 weeks in duration and dietary protein supplementation.
DESIGN
Random-effects meta-analyses and meta-regressions with four a priori determined covariates. Two-phase break point analysis was used to determine the relationship between total protein intake and changes in fat-free mass (FFM).
RESULTS
Data from 49 studies with 1863 participants showed that dietary protein supplementation significantly (all p<0.05) increased changes (means (95% CI)) in: strength-one-repetition-maximum (2.49 kg (0.64, 4.33)), FFM (0.30 kg (0.09, 0.52)) and muscle size-muscle fibre cross-sectional area (CSA; 310 µm (51, 570)) and mid-femur CSA (7.2 mm (0.20, 14.30)) during periods of prolonged RET. The impact of protein supplementation on gains in FFM was reduced with increasing age (-0.01 kg (-0.02,-0.00), p=0.002) and was more effective in resistance-trained individuals (0.75 kg (0.09, 1.40), p=0.03). Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM.
SUMMARY/CONCLUSION
Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults. Increasing age reduces and training experience increases the efficacy of protein supplementation during RET. With protein supplementation, protein intakes at amounts greater than ~1.6 g/kg/day do not further contribute RET-induced gains in FFM.
Topics: Adult; Dietary Proteins; Dietary Supplements; Humans; Muscle Strength; Muscle, Skeletal; Randomized Controlled Trials as Topic; Regression Analysis; Resistance Training
PubMed: 28698222
DOI: 10.1136/bjsports-2017-097608 -
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 -
Nutrients Nov 2019While animal products are rich in protein, the adequacy of dietary protein intake from vegetarian/vegan diets has long been controversial. In this review, we examine the... (Review)
Review
While animal products are rich in protein, the adequacy of dietary protein intake from vegetarian/vegan diets has long been controversial. In this review, we examine the protein and amino acid intakes from vegetarian diets followed by adults in western countries and gather information in terms of adequacy for protein and amino acids requirements, using indirect and direct data to estimate nutritional status. We point out that protein-rich foods, such as traditional legumes, nuts and seeds, are sufficient to achieve full protein adequacy in adults consuming vegetarian/vegan diets, while the question of any amino acid deficiency has been substantially overstated. Our review addresses the adequacy in changes to protein patterns in people newly transitioning to vegetarian diets. We also specifically address this in older adults, where the issues linked to the protein adequacy of vegetarian diets are more complex. This contrasts with the situation in children where there are no specific concerns regarding protein adequacy because of their very high energy requirements compared to those of protein. Given the growing shifts in recommendations from nutrition health professionals for people to transition to more plant-based, whole-food diets, additional scientific evidence-based communications confirming the protein adequacy of vegetarian and vegan diets is warranted.
Topics: Diet, Vegetarian; Dietary Proteins; Humans; Nutritional Requirements
PubMed: 31690027
DOI: 10.3390/nu11112661 -
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 -
Current Opinion in Clinical Nutrition... Jan 2017High-protein intake may lead to increased intraglomerular pressure and glomerular hyperfiltration. This can cause damage to glomerular structure leading to or... (Review)
Review
PURPOSE OF REVIEW
High-protein intake may lead to increased intraglomerular pressure and glomerular hyperfiltration. This can cause damage to glomerular structure leading to or aggravating chronic kidney disease (CKD). Hence, a low-protein diet (LPD) of 0.6-0.8 g/kg/day is often recommended for the management of CKD. We reviewed the effect of protein intake on incidence and progression of CKD and the role of LPD in the CKD management.
RECENT FINDINGS
Actual dietary protein consumption in CKD patients remains substantially higher than the recommendations for LPD. Notwithstanding the inconclusive results of the 'Modification of Diet in Renal Disease' (MDRD) study, the largest randomized controlled trial to examine protein restriction in CKD, several prior and subsequent studies and meta-analyses appear to support the role of LPD on retarding progression of CKD and delaying initiation of maintenance dialysis therapy. LPD can also be used to control metabolic derangements in CKD. Supplemented LPD with essential amino acids or their ketoanalogs may be used for incremental transition to dialysis especially on nondialysis days. The LPD management in lieu of dialysis therapy can reduce costs, enhance psychological adaptation, and preserve residual renal function upon transition to dialysis. Adherence and adequate protein and energy intake should be ensured to avoid protein-energy wasting.
SUMMARY
A balanced and individualized dietary approach based on LPD should be elaborated with periodic dietitian counseling and surveillance to optimize management of CKD, to assure adequate protein and energy intake, and to avoid or correct protein-energy wasting.
Topics: Amino Acids, Essential; Diet, High-Protein; Diet, Protein-Restricted; Dietary Proteins; Dietary Supplements; Disease Progression; Humans; Incidence; Renal Insufficiency, Chronic; Treatment Outcome
PubMed: 27801685
DOI: 10.1097/MCO.0000000000000342 -
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 -
Advances in Nutrition (Bethesda, Md.) Sep 2018Proteins are polymers of amino acids linked via α-peptide bonds. They can be represented as primary, secondary, tertiary, and even quaternary structures, but from a...
Proteins are polymers of amino acids linked via α-peptide bonds. They can be represented as primary, secondary, tertiary, and even quaternary structures, but from a nutritional viewpoint only the primary (amino acid) sequence is of interest. Similarly, although there are many compounds in the body that can be chemically defined as amino acids, we are only concerned with the 20 canonical amino acids encoded in DNA, plus 5 others-ornithine, citrulline, γ-aminobutyrate, β-alanine, and taurine-that play quantitatively important roles in the body. We consume proteins, which are digested in the gastrointestinal tract, absorbed as small peptides (di- and tripeptides) and free amino acids, and then used for the resynthesis of proteins in our cells. Additionally, some amino acids are also used for the synthesis of specific (nonprotein) products, such as nitric oxide, polyamines, creatine, glutathione, nucleotides, glucosamine, hormones, neurotransmitters, and other factors. Again, such functions are not quantitatively important for most amino acids, and the bulk of amino acid metabolism is directly related to protein turnover (synthesis and degradation). For an individual in nitrogen balance, an amount of protein equal to that of the daily protein (nitrogen) intake is degraded each day with the nitrogen being excreted as urea and ammonia (with limited amounts of creatinine and uric acid). The carbon skeletons of the amino acids degraded to urea and ammonia are recovered through gluconeogenesis or ketone synthesis, or oxidized to carbon dioxide. Of the 20 amino acids present in proteins, 9 are considered nutritionally indispensable (essential) in adult humans because the body is not able to synthesize their carbon skeletons. These 9 amino acids are leucine, valine, isoleucine, histidine, lysine, methionine, threonine, tryptophan, and phenylalanine. In addition, 2 others are made from their indispensable precursors: cysteine from methionine, and tyrosine from phenylalanine. Although arginine is needed in neonates, it appears that adults, with the possible exceptions of pregnancy in females and spermatogenesis in males, can synthesize sufficient arginine to maintain a nitrogen balance. The others, glutamate, glutamine, aspartate, asparagine, serine, glycine, proline, and alanine, can all be synthesized from glucose and a suitable nitrogen source. Under some conditions, glutamine, glutamate, glycine, proline, and arginine may be considered as conditionally indispensable, meaning that the body is not capable of synthesizing them in sufficient quantities for a specific physiologic or pathologic condition (1). Thus, any discussion of dietary protein must consider not only quantity but also quality (ratio of indispensable amino acids).
Topics: Adult; Amino Acids; Amino Acids, Essential; Dietary Proteins; Dietary Supplements; Female; Humans; Male; Nutritive Value; Pregnancy
PubMed: 30060014
DOI: 10.1093/advances/nmy027 -
Blood Purification 2021Over the last 2 decades, there has been a great accumulation of new evidence regarding the management of nutritional and metabolic aspects of kidney disease. The 2020... (Review)
Review
Over the last 2 decades, there has been a great accumulation of new evidence regarding the management of nutritional and metabolic aspects of kidney disease. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD provides a comprehensive up-to-date information on the understanding and care of patients with CKD. It provides updated information on nutritional aspects of kidney disease for the practicing clinician and allied health-care workers. The current manuscript provides an overview of the updated guideline statements on major subjects including nutritional assessment, dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines are focused on dietary management rather than all possible nutritional interventions.
Topics: Dietary Proteins; Dietary Supplements; Energy Intake; Humans; Micronutrients; Nutrition Assessment; Nutritional Status; Renal Insufficiency, Chronic
PubMed: 33652433
DOI: 10.1159/000513698 -
The American Journal of Clinical... Mar 2016A dietary protein intake higher than the Recommended Dietary Allowance during an energy deficit helps to preserve lean body mass (LBM), particularly when combined with... (Comparative Study)
Comparative Study Randomized Controlled Trial
BACKGROUND
A dietary protein intake higher than the Recommended Dietary Allowance during an energy deficit helps to preserve lean body mass (LBM), particularly when combined with exercise.
OBJECTIVE
The purpose of this study was to conduct a proof-of-principle trial to test whether manipulation of dietary protein intake during a marked energy deficit in addition to intense exercise training would affect changes in body composition.
DESIGN
We used a single-blind, randomized, parallel-group prospective trial. During a 4-wk period, we provided hypoenergetic (~40% reduction compared with requirements) diets providing 33 ± 1 kcal/kg LBM to young men who were randomly assigned (n = 20/group) to consume either a lower-protein (1.2 g · kg(-1) · d(-1)) control diet (CON) or a higher-protein (2.4 g · kg(-1) · d(-1)) diet (PRO). All subjects performed resistance exercise training combined with high-intensity interval training for 6 d/wk. A 4-compartment model assessment of body composition was made pre- and postintervention.
RESULTS
As a result of the intervention, LBM increased (P < 0.05) in the PRO group (1.2 ± 1.0 kg) and to a greater extent (P < 0.05) compared with the CON group (0.1 ± 1.0 kg). The PRO group had a greater loss of fat mass than did the CON group (PRO: -4.8 ± 1.6 kg; CON: -3.5 ± 1.4kg; P < 0.05). All measures of exercise performance improved similarly in the PRO and CON groups as a result of the intervention with no effect of protein supplementation. Changes in serum cortisol during the intervention were associated with changes in body fat (r = 0.39, P = 0.01) and LBM (r = -0.34, P = 0.03).
CONCLUSIONS
Our results showed that, during a marked energy deficit, consumption of a diet containing 2.4 g protein · kg(-1) · d(-1) was more effective than consumption of a diet containing 1.2 g protein · kg(-1) · d(-1) in promoting increases in LBM and losses of fat mass when combined with a high volume of resistance and anaerobic exercise. Changes in serum cortisol were associated with changes in body fat and LBM, but did not explain much variance in either measure. This trial was registered at clinicaltrials.gov as NCT01776359.
Topics: Adipose Tissue; Adult; Body Composition; Body Fluid Compartments; Caloric Restriction; Diet; Dietary Proteins; Energy Intake; Exercise; Humans; Hydrocortisone; Male; Nutritional Requirements; Physical Exertion; Prospective Studies; Resistance Training; Single-Blind Method; Young Adult
PubMed: 26817506
DOI: 10.3945/ajcn.115.119339 -
Current Protein & Peptide Science 2017There is growing recognition that composition and metabolic activity of the gut microbiota can be modulated by the dietary proteins which in turn impact health. The... (Review)
Review
There is growing recognition that composition and metabolic activity of the gut microbiota can be modulated by the dietary proteins which in turn impact health. The amino acid composition and digestibility of proteins, which are influenced by its source and amount of intake, play a pivotal role in determining the microbiota. Reciprocally, it appears that the gut microbiota is also able to affect protein metabolism which gives rise to the view that function between the microbiota and protein can proceed in both directions. In response to the alterations in dietary protein components, there are significant changes in the microbial metabolites including short chain fatty acids (SCFAs), ammonia, amines, gases such as hydrogen, sulfide and methane which are cytotoxins, genotoxins and carcinogens associated with development of colon cancer and inflammatory bowel diseases. A suitable ratio between protein and carbohydrate or even a low protein diet is recommended based on the evidence that excessive protein intake adversely affects health. Supplying high and undigested proteins will encourage pathogens and protein-fermenting bacteria to increase the risk of diseases. These changes of microbiota can affect the gut barrier and the immune system by regulating gene expression in relevant signaling pathways and by regulating the secretion of metabolites. The objective of this review is to assess the impact of dietary proteins on microbiota composition and activity in the gastrointestinal tract. Attention should be given to the dietary strategies with judicious selection of source and supplementation of dietary protein to benefit gut health.
Topics: Actinobacteria; Amines; Ammonia; Bacteroidetes; Dietary Carbohydrates; Dietary Proteins; Fatty Acids, Volatile; Fermentation; Firmicutes; Fusobacteria; Gastrointestinal Microbiome; Gastrointestinal Tract; Humans; Proteobacteria; Proteolysis; Verrucomicrobia
PubMed: 28215168
DOI: 10.2174/1389203718666170216153505