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Medicine and Science in Sports and... Feb 2019Recommendations for dietary protein are primarily based on intakes that maintain nitrogen (i.e., protein) balance rather than optimize metabolism and/or performance. (Randomized Controlled Trial)
Randomized Controlled Trial
UNLABELLED
Recommendations for dietary protein are primarily based on intakes that maintain nitrogen (i.e., protein) balance rather than optimize metabolism and/or performance.
PURPOSE
This study aimed to determine how varying protein intakes, including a new tracer-derived safe intake, alter whole body protein metabolism and exercise performance during training.
METHODS
Using a double-blind randomized crossover design, 10 male endurance-trained runners (age, 32 ± 8 yr; V˙O2peak, 65.9 ± 7.9 mL O2·kg·min) performed three trials consisting of 4 d of controlled training (20, 5, 10, and 20 km·d, respectively) while consuming diets providing 0.94 (LOW), 1.20 (MOD), and 1.83 (HIGH) g protein·kg·d. Whole body protein synthesis, breakdown, and net balance were determined by oral [N]glycine on the first and last day of the 4-d controlled training period, whereas exercise performance was determined from maximum voluntary isometric contraction, 5-km time trial, and countermovement jump impulse (IMP) and peak force before and immediately after the 4-d intervention.
RESULTS
Synthesis and breakdown were not affected by protein intake, whereas net balance showed a dose-response (HIGH > MOD > LOW, P < 0.05) with only HIGH being in positive balance (P < 0.05). There was a trend (P = 0.06) toward an interaction in 5-km Time Trial with HIGH having a moderate effect over LOW (effect size = 0.57) and small effect over MOD (effect size = 0.26). IMP decreased with time (P < 0.01) with no effect of protein (P = 0.56). There was no effect of protein intake (P ≥ 0.06) on maximum voluntary isometric contraction, IMP, or peak force performance.
CONCLUSION
Our data suggest that athletes who consume dietary protein toward the upper end of the current recommendations by the American College of Sports Medicine (1.2-2 g·kg) would better maintain protein metabolism and potentially exercise performance during training.
Topics: Adult; Cross-Over Studies; Diet; Dietary Proteins; Double-Blind Method; Endurance Training; Energy Drinks; Energy Metabolism; Exercise Test; Humans; Isometric Contraction; Male; Muscle, Skeletal; Myalgia; Physical Endurance; Plyometric Exercise; Young Adult
PubMed: 30252774
DOI: 10.1249/MSS.0000000000001791 -
International Journal of Sport... Apr 2017Dietary protein intake should be optimized in all athletes to ensure proper recovery and enhance the skeletal muscle adaptive response to exercise training. In addition... (Comparative Study)
Comparative Study
Dietary protein intake should be optimized in all athletes to ensure proper recovery and enhance the skeletal muscle adaptive response to exercise training. In addition to total protein intake, the use of specific proteincontaining food sources and the distribution of protein throughout the day are relevant for optimizing protein intake in athletes. In the present study, we examined the daily intake and distribution of various proteincontaining food sources in a large cohort of strength, endurance and team-sport athletes. Well-trained male (n=327) and female (n=226) athletes completed multiple web-based 24-hr dietary recalls over a 2-4 wk period. Total energy intake, the contribution of animal- and plant-based proteins to daily protein intake, and protein intake at six eating moments were determined. Daily protein intake averaged 108±33 and 90±24 g in men and women, respectively, which corresponded to relative intakes of 1.5±0.4 and 1.4±0.4 g/kg. Dietary protein intake was correlated with total energy intake in strength (r=0.71, p <.001), endurance (r=0.79, p <.001) and team-sport (r=0.77, p <.001) athletes. Animal and plant-based sources of protein intake was 57% and 43%, respectively. The distribution of protein intake was 19% (19±8 g) at breakfast, 24% (25±13 g) at lunch and 38% (38±15 g) at dinner. Protein intake was below the recommended 20 g for 58% of athletes at breakfast, 36% at lunch and 8% at dinner. In summary, this survey of athletes revealed they habitually consume > 1.2 g protein/kg/d, but the distribution throughout the day may be suboptimal to maximize the skeletal muscle adaptive response to training.
Topics: Adolescent; Adult; Athletes; Athletic Performance; Child; Cohort Studies; Dietary Proteins; Exercise; Feeding Behavior; Female; Humans; Internet; Male; Middle Aged; Milk Proteins; Muscle Proteins; Muscle Strength; Netherlands; Nutrition Surveys; Physical Endurance; Physical Exertion; Plant Proteins, Dietary; Sports Nutritional Physiological Phenomena; Young Adult
PubMed: 27710150
DOI: 10.1123/ijsnem.2016-0154 -
Nutrients Dec 2017Thyroid hormones (TH) are essential for the normal development and function of every vertebrate. The hypothalamic-pituitary-thyroid (HPT) axis is regulated to maintain... (Review)
Review
Thyroid hormones (TH) are essential for the normal development and function of every vertebrate. The hypothalamic-pituitary-thyroid (HPT) axis is regulated to maintain euthyroid status. One of the most influential environmental factors that determines HPT axis activity is nutrition. Both food availability and substrate diversity affect thyroid hormone economy. The present paper aims to summarize literature data concerning the influence of the amount and the type of protein on thyroid axis activity. This review sheds light on the contribution of a low-protein diet or insufficient intake of essential amino acids to TH abnormalities. We believe that the knowledge of these dependencies could improve the results of nutritional interventions in thyroid axis disorders and enhance the efficiency of animal breeding.
Topics: Animals; Diet, Protein-Restricted; Dietary Proteins; Humans; Hypothalamo-Hypophyseal System; Nutritional Status; Risk Factors; Thyroid Diseases; Thyroid Gland; Thyroid Hormones
PubMed: 29271877
DOI: 10.3390/nu10010005 -
The British Journal of Nutrition Mar 2020Dietary protein insufficiency has been linked to excessive TAG storage and non-alcoholic fatty liver disease (NAFLD) in developing countries. Hepatic TAG accumulation... (Review)
Review
Dietary protein insufficiency has been linked to excessive TAG storage and non-alcoholic fatty liver disease (NAFLD) in developing countries. Hepatic TAG accumulation following a low-protein diet may be due to altered peroxisomal, mitochondrial and gut microbiota function. Hepatic peroxisomes and mitochondria normally mediate metabolism of nutrients to provide energy and substrates for lipogenesis. Peroxisome biogenesis and activities can be modulated by odd-chain fatty acids (OCFA) and SCFA that are derived from gut bacteria, for example, propionate and butyrate. Also produced during amino acid metabolism by peroxisomes and mitochondria, propionate and butyrate concentrations correlate inversely with risk of obesity, insulin resistance and NAFLD. In this horizon-scanning review, we have compiled available evidence on the effects of protein malnutrition on OCFA production, arising from loss in mitochondrial, peroxisomal and gut microbiota function, and its association with lipid accumulation in the liver. The methyl donor amino acid composition of dietary protein is an important contributor to liver function and lipid storage; the presence and abundance of dietary branched-chain amino acids can modulate the composition and metabolic activity of the gut microbiome and, on the other hand, can affect protective OCFA and SCFA production in the liver. In preclinical animal models fed with low-protein diets, specific amino acid supplementation can ameliorate fatty liver disease. The association between low dietary protein intake and fatty liver disease is underexplored and merits further investigation, particularly in vulnerable groups with dietary protein restriction in developing countries.
Topics: Dietary Proteins; Fatty Acids; Humans; Liver; Non-alcoholic Fatty Liver Disease; Protein Deficiency
PubMed: 31779730
DOI: 10.1017/S0007114519003064 -
Advances in Food and Nutrition Research 2020Proteins and its building blocks, amino acids, have many physiological roles in the body. While some amino acids can be synthesized endogenously, exogenous protein and... (Review)
Review
Proteins and its building blocks, amino acids, have many physiological roles in the body. While some amino acids can be synthesized endogenously, exogenous protein and amino acids are necessary to maintain homeostasis. Because skeletal muscle contains a large portion of endogenous protein and plays important roles in movement, regulation, and metabolism, imbalanced protein and amino acid availability may result in clinical conditions including skeletal muscle atrophy, impaired muscle growth or regrowth, and functional decline. Aging is associated with changes in protein metabolism and multiple physiological and functional alterations in the skeletal muscle that are accentuated by decreased dietary protein intake and impaired anabolic responses to stimuli. Inactivity and chronically elevated inflammation of the skeletal muscle can initiate and/or augment pathological remodeling of the tissue (i.e., increase of fat and fibrotic tissues and atrophy of the muscle). Defining an adequate amount of dietary protein that is appropriate to maintain the availability of amino acids for biological needs is necessary but is still widely debated for older adults. This chapter will provide (i) an overview of dietary protein and amino acids and their role in skeletal muscle health; (ii) an overview of skeletal muscle structure and function and the deterioration of muscle that occurs with advancing age; (iii) a discussion of the relationship between protein/amino acid metabolism and skeletal muscle decline with aging; and (iv) a brief discussion of optimal protein intakes for older adults to maintain skeletal muscle health in aging.
Topics: Aging; Amino Acids; Dietary Proteins; Humans; Muscle, Skeletal; Muscular Diseases
PubMed: 32035599
DOI: 10.1016/bs.afnr.2019.08.002 -
Physiological Reports Aug 2023Dietary protein ingestion augments post (resistance) exercise muscle protein synthesis (MPS) rates. It is thought that the dose of leucine ingested within the protein... (Review)
Review
BACKGROUND
Dietary protein ingestion augments post (resistance) exercise muscle protein synthesis (MPS) rates. It is thought that the dose of leucine ingested within the protein (leucine threshold hypothesis) and the subsequent plasma leucine variables (leucine trigger hypothesis; peak magnitude, rate of rise, and total availability) determine the magnitude of the postprandial postexercise MPS response.
METHODS
A quantitative systematic review was performed extracting data from studies that recruited healthy adults, applied a bout of resistance exercise, ingested a bolus of protein within an hour of exercise, and measured plasma leucine concentrations and MPS rates (delta change from basal).
RESULTS
Ingested leucine dose was associated with the magnitude of the MPS response in older, but not younger, adults over acute (0-2 h, r = 0.64, p = 0.02) and the entire postprandial (>2 h, r = 0.18, p = 0.01) period. However, no single plasma leucine variable possessed substantial predictive capacity over the magnitude of MPS rates in younger or older adults.
CONCLUSION
Our data provide support that leucine dose provides predictive capacity over postprandial postexercise MPS responses in older adults. However, no threshold in older adults and no plasma leucine variable was correlated with the magnitude of the postexercise anabolic response.
Topics: Humans; Aged; Leucine; Muscle Proteins; Diet; Muscle, Skeletal; Dietary Proteins; Postprandial Period
PubMed: 37537134
DOI: 10.14814/phy2.15775 -
Nutrients Aug 2015Declines in skeletal muscle mass and strength are major contributors to increased mortality, morbidity and reduced quality of life in older people. Recommended Dietary... (Review)
Review
Declines in skeletal muscle mass and strength are major contributors to increased mortality, morbidity and reduced quality of life in older people. Recommended Dietary Allowances/Intakes have failed to adequately consider the protein requirements of the elderly with respect to function. The aim of this paper was to review definitions of optimal protein status and the evidence base for optimal dietary protein. Current recommended protein intakes for older people do not account for the compensatory loss of muscle mass that occurs on lower protein intakes. Older people have lower rates of protein synthesis and whole-body proteolysis in response to an anabolic stimulus (food or resistance exercise). Recommendations for the level of adequate dietary intake of protein for older people should be informed by evidence derived from functional outcomes. Randomized controlled trials report a clear benefit of increased dietary protein on lean mass gain and leg strength, particularly when combined with resistance exercise. There is good consistent evidence (level III-2 to IV) that consumption of 1.0 to 1.3 g/kg/day dietary protein combined with twice-weekly progressive resistance exercise reduces age-related muscle mass loss. Older people appear to require 1.0 to 1.3 g/kg/day dietary protein to optimize physical function, particularly whilst undertaking resistance exercise recommendations.
Topics: Accidental Falls; Aged; Aging; Body Composition; Bone and Bones; Dietary Proteins; Elder Nutritional Physiological Phenomena; Energy Intake; Energy Metabolism; Fractures, Bone; Humans; Motor Activity; Muscle Strength; Muscle, Skeletal; Randomized Controlled Trials as Topic; Recommended Dietary Allowances
PubMed: 26287239
DOI: 10.3390/nu7085311 -
Sports Medicine (Auckland, N.Z.) Nov 2014Given our rapidly aging world-wide population, the loss of skeletal muscle mass with healthy aging (sarcopenia) represents an important societal and public health... (Review)
Review
Given our rapidly aging world-wide population, the loss of skeletal muscle mass with healthy aging (sarcopenia) represents an important societal and public health concern. Maintaining or adopting an active lifestyle alleviates age-related muscle loss to a certain extent. Over time, even small losses of muscle tissue can hinder the ability to maintain an active lifestyle and, as such, contribute to the development of frailty and metabolic disease. Considerable research focus has addressed the application of dietary protein supplementation to support exercise-induced gains in muscle mass in younger individuals. In contrast, the role of dietary protein in supporting the maintenance (or gain) of skeletal muscle mass in active older persons has received less attention. Older individuals display a blunted muscle protein synthetic response to dietary protein ingestion. However, this reduced anabolic response can largely be overcome when physical activity is performed in close temporal proximity to protein consumption. Moreover, recent evidence has helped elucidate the optimal type and amount of dietary protein that should be ingested by the older adult throughout the day in order to maximize the skeletal muscle adaptive response to physical activity. Evidence demonstrates that when these principles are adhered to, muscle maintenance or hypertrophy over prolonged periods can be further augmented in active older persons. The present review outlines the current understanding of the role that dietary protein occupies in the lifestyle of active older adults as a means to increase skeletal muscle mass, strength and function, and thus support healthier aging.
Topics: Aged; Aging; Dietary Proteins; Exercise; Humans; Muscle Proteins; Muscle, Skeletal; Physical Education and Training
PubMed: 25355192
DOI: 10.1007/s40279-014-0258-7 -
Meat Science Nov 2015Preservation of skeletal muscle mass is of great importance for maintaining both metabolic health and functional capacity. Muscle mass maintenance is regulated by the... (Review)
Review
Preservation of skeletal muscle mass is of great importance for maintaining both metabolic health and functional capacity. Muscle mass maintenance is regulated by the balance between muscle protein breakdown and synthesis rates. Both muscle protein breakdown and synthesis rates have been shown to be highly responsive to physical activity and food intake. Food intake, and protein ingestion in particular, directly stimulates muscle protein synthesis rates. The postprandial muscle protein synthetic response to feeding is regulated on a number of levels, including dietary protein digestion and amino acid absorption, splanchnic amino acid retention, postprandial insulin release, skeletal muscle tissue perfusion, amino acid uptake by muscle, and intramyocellular signaling. The postprandial muscle protein synthetic response to feeding is blunted in many conditions characterized by skeletal muscle loss, such as aging and muscle disuse. Therefore, it is important to define food characteristics that modulate postprandial muscle protein synthesis. Previous work has shown that the muscle protein synthetic response to feeding can be modulated by changing the amount of protein ingested, the source of dietary protein, as well as the timing of protein consumption. Most of this work has studied the postprandial response to the ingestion of isolated protein sources. Only few studies have investigated the postprandial muscle protein synthetic response to the ingestion of protein dense foods, such as dairy and meat. The current review will focus on the capacity of proteins and protein dense food products to stimulate postprandial muscle protein synthesis and identifies food characteristics that may modulate the anabolic properties.
Topics: Animals; Dairy Products; Dietary Proteins; Eating; Energy Intake; Humans; Meat; Muscle Proteins; Muscle, Skeletal; Postprandial Period; Protein Biosynthesis
PubMed: 26021783
DOI: 10.1016/j.meatsci.2015.05.009 -
The Journal of Nutrition, Health & Aging Apr 2024Inflammation and impaired muscle synthesis are important factors of sarcopenia. Plant protein may reduce inflammation but may not be as efficient as animal protein in...
OBJECTIVES
Inflammation and impaired muscle synthesis are important factors of sarcopenia. Plant protein may reduce inflammation but may not be as efficient as animal protein in providing essential amino acids. We therefore examined the associations between dietary protein intake and changes in muscle mass and physical performance, incident sarcopenia, and the interaction effect of inflammation.
DESIGN
Prospective cohort study.
SETTING
The Mr. OS and Ms. OS (Hong Kong) cohort.
PARTICIPANTS
A total of 2,811 sarcopenia-free participants and 569 sarcopenia participants aged ≥65 years were recruited from communities.
MEASUREMENTS
Dietary protein intake was assessed using a validated food frequency questionnaire. Serum high-sensitivity C-reactive protein (hs-CRP) was measured. Linear regression examined the associations between dietary protein intake and 4-year changes in muscle mass and physical performance. Cox regression examined the association between dietary protein intake and incident sarcopenia.
RESULTS
Higher plant protein intake, but not total and animal protein, was associated with less decline in muscle mass and gait speed among sarcopenia-free participants. Conversely, higher ratio of animal-to-plant protein was associated with reduced muscle mass loss among participants with sarcopenia. The highest tertile of plant protein intake was associated with lower incident sarcopenia risk (HR: 0.75, 95% CI: 0.57-0.98; P-trend = 0.034) compared to the lowest tertile. Notably, this association was observed among participants with higher serum hs-CRP levels (HR: 0.57, 95% CI: 0.34-0.95), but not in those with lower hs-CRP levels.
CONCLUSION
Dietary animal and plant protein intake have differential associations with muscle mass and physical performance in older adults with and without sarcopenia. The role of plant protein in preventing sarcopenia involves modulation of inflammation.
Topics: Humans; Sarcopenia; Aged; Male; Female; Independent Living; Inflammation; Prospective Studies; Dietary Proteins; Muscle, Skeletal; C-Reactive Protein; Physical Functional Performance; Hong Kong; Incidence; Plant Proteins, Dietary; Animal Proteins, Dietary; Asian People; East Asian People
PubMed: 38350300
DOI: 10.1016/j.jnha.2024.100163