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Position Statement: The International Society of Sports Nutrition (ISSN) presents this position based on a critical examination of literature surrounding the effects of essential amino acid (EAA) supplementation on skeletal muscle maintenance and performance. This position stand is intended to provide a scientific foundation to athletes, dietitians...
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Context 1
... data are available upon which to base the safe upper limit of individual EAA consumption. Table 1 lists consumption levels of each EAA that has been shown to be safe. The safe upper limits in Table 1 are expressed as the amount of each EAA consumed above habitual intake. ...Context 2
... 1 lists consumption levels of each EAA that has been shown to be safe. The safe upper limits in Table 1 are expressed as the amount of each EAA consumed above habitual intake. Thus, when considering the safe amounts of each EAA, these data indicate that more than 100 g of supplemental EAAs can be safely consumed per day in an American adult already consuming the average habitual dietary intake of approximately 40 grams per day. ...Context 3
... data are available upon which to base the safe upper limit of individual EAA consumption. Table 1 lists consumption levels of each EAA that has been shown to be safe. The safe upper limits in Table 1 are expressed as the amount of each EAA consumed above habitual intake. ...Context 4
... 1 lists consumption levels of each EAA that has been shown to be safe. The safe upper limits in Table 1 are expressed as the amount of each EAA consumed above habitual intake. Thus, when considering the safe amounts of each EAA, these data indicate that more than 100 g of supplemental EAAs can be safely consumed per day in an American adult already consuming the average habitual dietary intake of approximately 40 grams per day. ...Citations
... Leucine plays a crucial role as a primary EAA in activating the mammalian target of rapamycin complex-1 (mTOR), a key protein responsible for triggering MPS (35). It is suggested that MPS begins to increase with around 3 g of leucine and plateaus at approximately 15 to 18 g (9,13). For example, Coburn et al. (11) reported that consuming 20 g of a whey protein blend with 6.2 g of leucine, combined with 8 weeks of unilateral leg extension dynamic constant external resistance (DCER) training resulted in greater increases in muscular strength compared to a PLA group. ...
... Based on the findings of previous studies (11,13,23,26,28,48), the following hypotheses were made: (a) A dose of 40 g of whey protein with a total of 6.2 g of leucine taken once daily would significantly improve muscular strength and endurance as well as increase muscle size and BM following the 8-week training intervention; (b) The 40 g of whey protein with a total of 6.2 g of leucine once daily would yield effects on muscular strength and endurance as well as muscle size and BM comparable to those from the 20 g of whey protein and 6.2 g of leucine taken twice daily; and (c) Both the 40 g of whey protein plus 6.2 g of leucine once daily and the 20 g of whey protein plus 6.2 g of leucine taken twice daily would significantly improve muscular strength, muscular endurance, and muscle size for individual subjects in comparison to the placebo group. ...
This study examined the effects of resistance training combined with whey protein and leucine blends on muscular strength (1-RM), endurance (repetitions to failure [RTF]), cross-sectional area (CSA), perceived exertion (RPE), and body mass (BM). Thirty-nine men (age = 20.6 ± 1.5 yrs) were randomly assigned to 1 of 3 Groups: (a) 1 dose of 40 g of whey protein and 6.2 g of total leucine (1PRO+L, n = 13); (b) 2 doses of 20 g of whey protein and 6.2 g of total leucine per dose (2PRO+L, n = 12); or (c) placebo (PLA, n = 14). The dependent variables were assessed before and after 8 weeks of high-intensity resistance training 3 d·wk-1. Mixed factorial ANOVAs revealed significant (P < 0.001) increases in BP and LE 1-RM and RTF, VL CSA, a reduction in RPE, and no change in BM (P > 0.05), with no between Group differences. Individual analyses indicated that a greater proportion of the 1PRO+L Group exceeded the minimal important difference for LE 1-RM and RTF compared to those in the 2PRO+L and PLA Groups (P < 0.05). No other differences were observed for the individual responses. These findings indicate that 40 g of whey protein with 6.2 g of total leucine increased LE 1-RM and RTF more than 2 doses of 20 g of whey protein with 6.2 g of total leucine or PLA.
... Similarly, insufficient or excessive intake of non-EAAs is harmful to the human body. Foods that maintain a similar proportion of amino acids to the human body's requirements are considered highly nutritional (4). As an essential indicator of food quality, amino acids' composition and content directly affect food protein quality. ...
Amino acids are an essential source of human protein, and their content and composition are the main factors determining food protein utilization rate. Determining amino acids is essential in the component analysis of food. Therefore, a groundbreaking technique was developed utilizing ultra-high performance liquid chromatography interfaced with a triple quadrupole mass spectrometer (UHPLC-QQQ-MS/MS) for concurrently quantifying 18 amino acids across various types of meat. According to the test results, it can be known that the average content of glutamate (2.03 × 10⁴ ± 3.94 × 10³ μg/g in pig feet) was the highest in all meat samples, and the content of aspartate (0.0945 ± 0.0950 μg/g in pork) was the lowest, which was not detected in some samples such as beef and lean meat. Orthogonal partial least-squares discrimination analysis (OPLS-DA) showed: (1) 13 amino acids (arginine, valine, serine, alanine, lysine, glycine, asparagine, methionine, proline, threonine, glutamate, phenylalanine, and leucine, VIP > 1) were used as characteristic amino acids between pork and pig feet; (2) serine, threonine, alanine, histidine, asparagine, and arginine (VIP > 1) were used as signature amino acids in different components of pork (lean meat, fat, and pigskin); (3) asparagine, glutamate, histidine, tyrosine, and valine (VIP > 1) were considered as signature amino acids in different types of meats (pork, mutton, beef, and chicken). This study provides a new UHPLC-QQQ-MS/MS method for the determination of amino acid content in meat and also provides data support for the comprehensive evaluation of the nutritional value of foods containing amino acids.
... Additionally, resistance training influences the endocrine system by regulating hormone levels, thereby promoting muscle growth and repair 34 . Resistance training enhances the utilization efficiency of amino acids within muscles, promoting the synthesis of muscle protein, which counters the decline in muscle mass due to aging 35,36 . ...
Aging has made stroke a top killer and disabler, with post-stroke sarcopenia worsening disability and quality of life. While resistance training benefits the elderly, its impact on stroke patients is understudied. This study evaluates the potential of a 4-week unilateral resistance training (URT) program to prevent sarcopenia in stroke patients. It assesses the impact of URT on hand grip strength (HG), muscle thickness (MT), upper limb functionality, and the psychological status of the patients. The study aims to quantitatively analyze these indicators to inform evidence-based post-stroke rehabilitation practices. This study employed a randomized controlled trial (RCT) involving 77 eligible stroke survivors, equally allocated into a control group (n = 39) and an intervention group (n = 38). The control group received standard rehabilitation, while the intervention group additionally underwent a 4-week URT program. The primary outcomes were unaffected side HG and MT, measuring muscle mass and function. Secondary outcomes included the Fugl-Meyer Assessment of the Upper Extremity (FMA-UE) for upper limb functionality and the Hamilton Depression Rating Scale (HAMD) for psychological well-being changes. Statistical analysis showed significant differences (p < 0. 05) in all measured parameters between the intervention and control groups after the 4-week period. Intra-group comparisons also indicated substantial improvements (p < 0. 05). Unilateral resistance training significantly mitigates muscle atrophy in stroke patients, preventing sarcopenia and enhancing upper limb function. It also ameliorates depressive symptoms, improving rehabilitation outcomes and overall quality of life.
... The process of MPS is highly sensitive to the availability of essential amino acids (EAAs), particularly leucine. Leucine activates the mTOR pathway, a crucial regulator of cell growth and protein synthesis [82]. Studies such as the International Society of Sports Nutrition Position Stand by Jäger et al. [83] emphasize the importance of high-quality protein sources rich in EAAs for maximizing MPS and enhancing muscle recovery and adaptation. ...
Background/Objectives: Sports supplements have become popular among fitness enthusiasts for enhancing the adaptive response to exercise. This review analyzes five of the most effective ergogenic aids: creatine, beta-alanine, nitrates, caffeine, and protein. Methods: We conducted a narrative review of the literature with a focus on the sport supplements with the most robust evidence for efficacy and safety. Results: Creatine, one of the most studied ergogenic aids, increases phosphocreatine stores in skeletal muscles, improving ATP production during high-intensity exercises like sprinting and weightlifting. Studies show creatine supplementation enhances skeletal muscle mass, strength/power, and muscular endurance. The typical dosage is 3–5 g per day and is safe for long-term use. Beta-alanine, when combined with the amino acid histidine, elevates intramuscular carnosine, which acts as a buffer in skeletal muscles and delays fatigue during high-intensity exercise by neutralizing hydrogen ions. Individuals usually take 2–6 g daily in divided doses to minimize paresthesia. Research shows significant performance improvements in activities lasting 1–4 min. Nitrates, found in beetroot juice, enhance aerobic performance by increasing oxygen delivery to muscles, enhancing endurance, and reducing oxygen cost during exercise. The recommended dosage is approximately 500 milligrams taken 2–3 h before exercise. Caffeine, a central nervous system stimulant, reduces perceived pain while enhancing focus and alertness. Effective doses range from 3 to 6 milligrams per kilogram of body weight, typically consumed an hour before exercise. Protein supplementation supports muscle repair, growth, and recovery, especially after resistance training. The recommended intake for exercise-trained men and women varies depending on their specific goals. Concluions: In summary, creatine, beta-alanine, nitrates, caffeine, and protein are the best ergogenic aids, with strong evidence supporting their efficacy and safety.
... Protein and/or EAA supplementation appeared unlikely to cause any adverse events, including AKI. Previous studies on older adults and patients with chronic heart failure reported no adverse events [14,54,55]. Additionally, another SR suggested that higher protein intake does not worsen kidney function in individuals with normal kidney function, regardless of age or type 2 diabetes [56]. ...
... However, most studies in this SR excluded patients with kidney dysfunction or disease. Given the uncertainty about the safety of protein and/or EAA supplementation in individuals with kidney dysfunction or disease, caution might be needed when considering its use in such patients [54,57,58]. ...
This study aimed to examine the efficacy and safety of protein and/or essential amino acid (EAA) supplementation in all lower limb surgeries using systematic reviews and meta-analysis of randomized controlled trials (RCTs). We included RCTs that assessed the efficacy of protein and/or EAA supplementation in lower limb surgeries. On June 2, 2023, we searched EMBASE, MEDLINE, the Cochrane Central Register of Controlled Trials, the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. The primary outcomes were mobility, patient-reported outcomes (PRO), and acute kidney injury (AKI). The secondary outcomes were exercise capacity, muscle strength, muscle mass, and all adverse events. We performed meta-analyses using the random-effects model. We assessed the risk of bias using the Cochrane risk-of-bias tool and the certainty of evidence using the Grading of Recommendations, Assessment, Development, and Evaluation approach. We included 12 RCTs (622 patients). These studies included four on hip fracture surgery, three on total hip arthroplasty, and five on total knee arthroplasty. Protein and/or EAA supplementation may slightly improve PRO (standard mean difference 0.51, 95% confidence interval (CI): 0.22 to 0.80, low certainty of evidence). Nevertheless, it may not improve mobility (mean difference 0.07 m/s, 95% CI: -0.01 to 0.16, low certainty of evidence). No adverse events including AKI were reported. Muscle strength may have increased (standard mean difference 0.31, 95% CI: 0.02 to 0.61, very low certainty of evidence). However, exercise capacity (mean difference 5.43 m, 95% CI: -35.59 to 46.45, very low certainty of evidence) and muscle mass (standard mean difference -0.08, 95% CI: -0.49 to 0.33, very low certainty of evidence) were not improved. While protein and/or EAA supplementation in lower limb surgeries may improve PRO, it is unlikely to affect mobility. Despite this, the medical team and patients might still consider protein and/or EAA supplementation a useful option.
... Protein and/or EAA supplementation appeared unlikely to cause any adverse events, including AKI. Previous studies on older adults and patients with chronic heart failure reported no adverse events [14,54,55]. Additionally, another SR suggested that higher protein intake does not worsen kidney function in individuals with normal kidney function, regardless of age or type 2 diabetes [56]. ...
... However, most studies in this SR excluded patients with kidney dysfunction or disease. Given the uncertainty about the safety of protein and/or EAA supplementation in individuals with kidney dysfunction or disease, caution might be needed when considering its use in such patients [54,57,58]. ...
This study aimed to examine the efficacy and safety of protein and/or essential amino acid (EAA) supplementation in all lower limb surgeries using systematic reviews and meta-analysis of randomized controlled trials (RCTs). We included RCTs that assessed the efficacy of protein and/or EAA supplementation in lower limb surgeries. On June 2, 2023, we searched EMBASE, MEDLINE, the Cochrane Central Register of Controlled Trials, the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. The primary outcomes were mobility, patient-reported outcomes (PRO), and acute kidney injury (AKI). The secondary outcomes were exercise capacity, muscle strength, muscle mass, and all adverse events. We performed meta-analyses using the random-effects model. We assessed the risk of bias using the Cochrane risk-of-bias tool and the certainty of evidence using the Grading of Recommendations, Assessment, Development, and Evaluation approach. We included 12 RCTs (622 patients). These studies included four on hip fracture surgery, three on total hip arthroplasty, and five on total knee arthroplasty. Protein and/or EAA supplementation may slightly improve PRO (standard mean difference 0.51, 95% confidence interval (CI): 0.22 to 0.80, low certainty of evidence). Nevertheless, it may not improve mobility (mean difference 0.07 m/s, 95% CI: -0.01 to 0.16, low certainty of evidence). No adverse events including AKI were reported. Muscle strength may have increased (standard mean difference 0.31, 95% CI: 0.02 to 0.61, very low certainty of evidence). However, exercise capacity (mean difference 5.43 m, 95% CI: -35.59 to 46.45, very low certainty of evidence) and muscle mass (standard mean difference -0.08, 95% CI: -0.49 to 0.33, very low certainty of evidence) were not improved. While protein and/or EAA supplementation in lower limb surgeries may improve PRO, it is unlikely to affect mobility. Despite this, the medical team and patients might still consider protein and/or EAA supplementation a useful option.
... Our study may be a suggestion to fine-tune dietary and supplementation recommendations for high-performance athletes depending on sports specialty. Current focus is on maximizing muscle protein synthesis after resistance exercise to maintain or increase SMM, while endurance athletes are recommended to achieve adequate carbohydrate intake with some protein addition to offset muscle (myofibrillar) damage and to support recovery and net protein balance [57,58]. Conceivably, amino acid blends tailored to the metabolic requirements of specific exercise or training modalities could be beneficial in competitive sports. ...
Circulating blood is an important plasma free amino acids (PFAAs) reservoir and a pivotal link between metabolic pathways. No comparisons are available between athletes with opposite training adaptations that include a broader spectrum of both proteinogenic and non-proteinogenic amino acids, and that take into account skeletal muscle mass. We hypothesized that the levels of the exercise-induced PFAAs concentration are related to the type of training-related metabolic adaptation. We compared highly trained endurance athletes (n = 11) and sprinters (n = 10) aged 20‒35 years who performed incremental exercise until exhaustion. Venous blood was collected before and during the test and 30-min recovery (12 samples). Forty-two PFAAs were assayed using LC-ESI-MS/MS technique. Skeletal muscle mass was estimated using dual X-ray absorptiometry method. Glutamine and alanine were dominant PFAAs throughout the whole exercise and recovery period (~350‒650 μmol∙L⁻¹). Total, combined proteinogenic, non-essential, and non-proteinogenic PFAAs levels were significantly higher in endurance athletes than sprinters (ANOVA group effects: p = 0.007, η² = 0.321; p = 0.011, η² = 0.294; p = 0.003, η² = 0.376; p = 0.001, η² = 0.471, respectively). The exercise response was more pronounced in endurance athletes, especially for non-proteinogenic PFAAs (ANOVA interaction effect: p = 0.038, η² = 0.123). Significant between-group differences were observed for 19 of 33 PFAAs detected, including 4 essential, 7 non-essential, and 8 non-proteinogenic ones. We demonstrated that the PFAAs response to incremental aerobic exercise is associated with the type of training-related metabolic adaptation. A greater turnover and availability of circulating PFAAs for skeletal muscles and other body tissues is observed in endurance- than in sprint-trained individuals. Non-proteinogenic PFAAs, despite low concentrations, also respond to exercise loads, indicating their important, though less understood role in exercise metabolism. Our study provides additional insight into the exercise-induced physiological response of PFAAs, and may also provide a rationale in discussions regarding dietary amino acid requirements in high-performance athletes with respect to sports specialization.
... Finally, our study may stimulate research in the area of nutrition and supplementation, even though such data were not included or analyzed here. Current recommendations from the International Society of Sports Nutrition for endurance athletes include adequate carbohydrate intake with added protein to compensate for muscle (myofibrillar) damage, support recovery, and maintain a balance between protein breakdown and synthesis [59,60]. However, non-proteinogenic amino acid supply and training phases are not included. ...
We aimed to evaluate long-term changes in proteinogenic and non-proteinogenic plasma free amino acids (PFAA). Eleven male endurance triathletes participated in a 9-month study. Blood was collected at rest, immediately after exhaustive exercise, and during 30-min recovery, in four consecutive training phases: transition, general, specific, and competition. Twenty proteinogenic and 22 non-proteinogenic PFAAs were assayed using the LC-ESI-MS/MS technique. The structured training modified the patterns of exercise-induced PFAA response, with the competition phase being the most distinct from the others. Branched-chain amino acids (p = 0.002; η2 = 0.216), phenylalanine (p = 0.015; η2 = 0.153), methionine (p = 0.002; η2 = 0.206), and lysine (p = 0.006; η2 = 0.196) declined more rapidly between rest and exhaustion in the competition phase. Glutamine (p = 0.008; η2 = 0.255), glutamate (p = 0.006; η2 = 0.265), tyrosine (p = 0.001; η2 = 0.195), cystine (p = 0.042; η2 = 0.183), and serine (p < 0.001; η2 = 0.346) levels were reduced in the competition phase. Arginine (p = 0.046; η2 = 0.138) and aspartate (p = 0.011; η2 = 0.171) levels were highest during exercise in the transition phase. During the competition phase, α-aminoadipic acid (p = 0.023; η2 = 0.145), β-aminoisobutyric acid (p = 0.007; η2 = 0.167), β-alanine (p < 0.001; η2 = 0.473), and sarcosine (p = 0.017; η2 = 0.150) levels increased, whereas phosphoethanolamine (p = 0.037; η2 = 0.189) and taurine (p = 0.008; η2 = 0.251) concentrations decreased. Overtraining indicators were not elevated. The altered PFAA profile suggests adaptations within energy metabolic pathways such as the tricarboxylic acid cycle, oxidative phosphorylation, ammonia neutralization, the purine nucleotide cycle, and buffering of intracellular H+ ions. The changes seem to reflect normal adaptations.
... Additionally, nitric oxide (NO) and amino acids, particularly glutamine and leucine, are involved in these processes. Although leucine directly activates mTORC1 [66,67], muscle protein synthesis strongly relies on essential amino acids, so focusing on the amino acid profile rather than leucine content alone would be a recommended approach [68]. Interestingly, a recent study in a murine model showed that (D)-3-hydroxybutyrate, the main component of ketone bodies, has positive effects on muscle atrophy and beneficial metabolic reprogramming effects in healthy muscle [69]. ...
... Physicians should consider the restrictions in protein intake for certain pathologies (e.g., kidney diseases). Protein of high biological value is recommended, including a combination of plant-based proteins, in order to ensure 8-10 g of essential amino acids and 2-3 g of leucine [68] are consumed. Administer creatine monohydrate as a safe, effective, and conditionally essential nutrient (with vast evidence) to improve muscle strength and hypertrophy, as well as quality of life, cognitive function, and metabolic health when combined with resistance training. ...
The ketogenic diet (KD) is a nutritional strategy characterized by a reduced intake of carbohydrates (between 30 and 45 g per day or ≈5% of one's total calories from this macronutrient). The regimen induces physiological ketosis in which serum levels of ketone bodies increase from 0.5 to 3.0 mM, becoming an essential contributor to energy production. The popularity of using the KD to lose weight and its application in specific physio-pathological conditions, such as epilepsy, lipedema, and polycystic ovary syndrome, which is maintained over extended periods, gave us the impulse to write this brief review. In these types of physio-pathological conditions, subjects can achieve favorable training outcomes even if adhering to a KD. Therefore, performing resistance training under the KD to enhance muscle status and quality of life could be possible. It is important to note that, while some statements here suggest potential future directions, they are hypotheses that require experimental validation, even if they are supported by the independent benefits reported from the KD and resistance training and represent a promising area for future research.
... The 2023 Position Statement by the International Society of Sport Nutrition [102] highlights that EAA ingestion in free form has been shown to be effective in stimulating MPS in doses as small as 1.5 g. Since it is readily absorbable, free-form EAA ingestion results in a more rapid increase in blood EAA concentrations and a subsequently greater peak in intramuscular EAA concentrations compared to whole protein sources [103,104]. ...
... Given the major influences that nutrient quantity, quality, and timing have on muscle protein synthesis and degradation, as well as glycogen resynthesis, optimizing nutritional status throughout these periods may offer a sustained substrate response over the postprandial period. Since the optimization of blood EAA levels with minimal risk of gastric discomfort is desired, the ingestion of 3-18 g of EAA is recommended, depending on gastrointestinal tolerance [102]. During the exercise bout, ingestion of a mixed nutrient solution containing lower-concentration CHO (6-8%) and EAA (6-10 g) may attenuate the exercise-induced cortisol response, as well as increasing insulin and extracellular amino acid availability [25,31]. ...
It is a common belief amongst strength and power athletes that nutritional supplementation strategies aid recovery by shifting the anabolic/catabolic profile toward anabolism. Factors such as nutrient quantity, nutrient quality, and nutrient timing significantly impact upon the effectiveness of nutritional strategies in optimizing the acute responses to resistance exercise and the adaptive response to resistance training (i.e., muscle growth and strength expression). Specifically, the aim of this review is to address carbohydrates (CHOs), protein (PRO), and/or amino acids (AAs) supplementation strategies, as there is growing evidence suggesting a link between nutrient signaling and the initiation of protein synthesis, muscle glycogen resynthesis, and the attenuation of myofibrillar protein degradation following resistance exercise. Collectively, the current scientific literature indicates that nutritional supplementation strategies utilizing CHO, PRO, and/or AA represents an important approach aimed at enhancing muscular responses for strength and power athletes, primarily increased muscular hypertrophy and enhanced strength expression. There appears to be a critical interaction between resistance exercise and nutrient–cell signaling associated with the principle of nutrient timing (i.e., pre-exercise, during, and post-exercise). Recommendations for nutritional supplementation strategies to promote muscular responses for strength and athletes are provided.
