Precision Engineered Liquid Aminos Wild Cherry Flavor bottle

Precision Engineered Liquid Aminos Wild Cherry Flavor Review

Precision Engineered Liquid Aminos Wild Cherry Flavor is a liquid amino acid supplement sold in a 16 fl. Oz. (473 mL) bottle. The label places the product in the Hardcore Series from Precision Engineered and states that it is formulated for bodybuilders and athletes. The brand describes it as Pro-Amino Fuel, a broad spectrum formula that is easily digested. According to the label, the formula contains a blend of essential and non-essential amino acids designed to support exercise and post-exercise states, or to be used at any time as part of a nutrition plan. The label notes that amino acids are the building blocks of protein, which plays a role in overall health. Each 2 tablespoon serving (15 servings per container) provides 60 calories, 16 grams of protein and 55 mg of sodium. The amino acids listed include L-Alanine, L-Arginine, L-Aspartic Acid, L-Glutamic Acid, Glycine, L-Histidine, L-Hydroxylysine, L-Isoleucine, L-Leucine, L-Lysine, L-Methionine, L-Phenylalanine, L-Proline, L-Serine, L-Threonine, L-Tyrosine and L-Valine. Glycine (3,622 mg) and L-Proline (2,130 mg) are the largest listed amounts. Daily Value is not established for these amino acids. Directions state to shake well before using. For adults, take two tablespoons (30 mL) three times daily, diluted with water. The label says to use the product as a food supplement only and not for weight reduction. It advises discontinuing use and consulting a doctor if any adverse reactions occur. It is not intended for persons under 18 and should be kept out of reach of children. Pregnant or nursing women, or anyone taking meds or with a medical condition, should consult a doctor before use. Store unopened at room temperature and refrigerate after opening for best results. The label states the product is artificially flavored, with no artificial color or sweetener, no sugar, no starch, no milk, no lactose, no soy, no gluten, no wheat, no yeast and no fish. The product is listed as gluten free, dairy free and sugar free. The FDA disclaimer states that these statements have not been evaluated by the Food and Drug Administration and that the product is not intended to diagnose, treat, cure or prevent any disease. The manufacturer is Precision Engineered Limited (USA) of Bohemia, NY, U.S.A. The label carries a 2012 copyright, and the NIH DSLD record shows ID 21045, entered 24 May 2013, with the product on market.

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Product Focus: Muscle and Strength

Tier ⓘ

Tier 4 · Rank 22

Tier 4 · Emerging. A promising mechanism or animal data, with thin human evidence so far. Rank 22 within Tier 4 for Muscle and Strength; 57 of 68 overall. Tiers run from 1, the strongest evidence, to 5. How we grade →

Evidence ⓘ

35 /100

How strongly the evidence says this product works: human studies count most, then real reviews, then our biohacker panel.

Biohacker Mentions

10 of 10

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Study, Trial or Testing Result Summary

Members Only146 human studies · 65 improved

4 of these 146 human studies gave the ingredient by drip, not by mouth.

146 human studies65 improved44 no effect25,816 people studied

This liquid is mostly gelatin protein, rich in glycine, proline and arginine, with only small amounts of leucine and the related muscle-building amino acids. At a full daily amount, glycine raised lean mass in malnourished kidney patients ^[1], and glycine paired with another antioxidant building block improved strength and walking in older adults ^[2]. For arginine, 5 grams before workouts for six months gave slightly more muscle gain in trained men ^[3], but several shorter trials found no change ^[4]^[5]. Leucine helped mainly when paired with protein ^[6], and leucine alone did little ^[7]^[8]. Isoleucine and valine were only studied inside a three-part mix, with mixed results ^[9]^[10]^[11]. Lysine support comes from mixes with arginine and a leucine breakdown product ^[12]. The amounts of alanine, aspartic acid, glutamic acid, histidine, methionine, phenylalanine, proline, serine, threonine and tyrosine have no clear studied muscle-building dose, and their evidence is thin or shows no effect ^[13]^[14]. Overall the evidence for this product building muscle is thin. Animal and cell studies are never counted.

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See all 146 studies →Hide the studies

Pooled analysis · 2018 · 1,863 people · L-Leucine Improved
Across 49 trials of 1863 healthy adults doing resistance training for at least 6 weeks, protein supplements modestly increased strength, lean mass and muscle size compared with control; this was about protein generally, not leucine alone.
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-i… · British journal of sports medicine
Pooled analysis · 2025 · 1,525 people · L-Isoleucine Mixed
In 23 trials of 1525 people with cirrhosis, branched-chain amino acids alone did not increase muscle mass, but combined with exercise and protein they gave the largest gain in muscle mass.
Exercise and nutrition interventions for sarcopenia in cirrhosis: a systematic review and network meta-analysis of rando… · European journal of clinical nutrition
Pooled analysis · 2022 · 1,225 people · L-Isoleucine Mixed
In 12 studies of 1225 people with cirrhosis, branched-chain amino acids improved muscle index and mid-arm muscle size from baseline but not handgrip strength, and study quality was limited.
Effects of Branched-Chain Amino Acids on Parameters Evaluating Sarcopenia in Liver Cirrhosis: Systematic Review and Meta… · Frontiers in nutrition
Pooled analysis · 2025 · 1,133 people · L-Leucine Improved
Across ten randomized trials and one prospective study of 1133 older adults with sarcopenia, leucine improved handgrip, limb muscle mass and walking speed compared with placebo, though the authors rated the evidence as low quality.
Effects of Leucine Supplementation in Older Adults with Sarcopenia: A Meta-Analysis. · Nutrients
Pooled analysis · 2022 · 699 people · L-Leucine Improved
Across six randomized trials of 699 older adults with sarcopenia, leucine-rich protein supplements improved muscle strength, mass and performance compared with control groups.
Effects of leucine-rich protein supplements in older adults with sarcopenia: A systematic review and meta-analysis of ra… · Archives of gerontology and geriatrics
Pooled analysis · 2023 · 637 people · L-Leucine Mixed
In three trials of 637 patients with sarcopenia, a whey protein, leucine and vitamin D combination increased limb muscle mass, but strength and function improved only when combined with an exercise program.
Effects of Whey Protein, Leucine, and Vitamin D Supplementation in Patients with Sarcopenia: A Systematic Review and Met… · Nutrients
Pooled analysis · 2017 · L-Isoleucine Mixed
In 8 trials, branched-chain amino acids lowered a blood marker of muscle damage after hard exercise compared with placebo, but did not significantly change muscle soreness.
Branched-chain amino acid supplementation and exercise-induced muscle damage in exercise recovery: A meta-analysis of ra… · Nutrition (Burbank, Los Angeles County, Calif.)
Pooled analysis · 2022 · L-Isoleucine Improved
In 20 randomized trials in people with cirrhosis, branched-chain amino acids modestly increased muscle mass but had no effect on fat mass.
Efficacy of branched chain amino acids supplementation in liver cirrhosis: A systematic review and meta-analysis. · Clinical nutrition (Edinburgh, Scotland)
Systematic review · 2024 · 1,976 people · L-Arginine Mixed
Thirty trials with 1976 critically ill adults tested amino acids such as glutamine, arginine and HMB; only six measured muscle, with one showing less wasting, one more wasting and three no effect, so arginine's effect on muscle is unclear.
A systematic review to assess the impact of amino acids or their derivatives on skeletal muscle wasting in critically il… · Clinical nutrition (Edinburgh, Scotland)
Systematic review · 2023 · 1,337 people · L-Isoleucine Mixed
In 12 trials of 1337 older adults, branched-chain amino acids with vitamin D improved muscle mass and function in most trials, while the amino acids alone did not improve muscle health.
The Role of Nutrition in the Treatment of Sarcopenia in Old Patients: From Restoration of Mitochondrial Activity to Impr… · Nutrients
Systematic review · 2017 · L-Arginine Mixed
In cancer patients, a mix of HMB, arginine and glutamine raised lean body mass after 4 weeks in one study but not after 8 weeks in a larger study, and the review found not enough solid evidence overall.
A systematic review on the role of vitamins, minerals, proteins, and other supplements for the treatment of cachexia in … · Journal of cachexia, sarcopenia and muscle
Systematic review · 2018 · L-Arginine Mixed
In nine trials of hip and knee replacement patients, amino acids reduced muscle wasting and sped up mobility, and one paper found a mix of HMB, arginine and glutamine reduced muscle strength loss after knee replacement.
What Is the Role of Nutritional Supplements in Support of Total Hip Replacement and Total Knee Replacement Surgeries? A … · Nutrients
Systematic review · 2021 · L-Arginine Improved
In 19 studies, 2-10 g per day of branched chain amino acids, alone or with arginine and carbohydrates, improved muscle recovery and strength after hard exercise, mainly in young men, but arginine's own effect was not separated.
Intake of branched chain amino acids favors post-exercise muscle recovery and may improve muscle function: optimal dosag… · The Journal of sports medicine and physical fitness
Systematic review · 2022 · L-Arginine No effect
A review of nine trials in adults 50 and older found an overall positive effect of protein and amino acids on wellbeing but no effect of arginine.
The potential role of beef and nutrients found in beef on outcomes of wellbeing in healthy adults 50 years of age and ol… · Meat science
Systematic review · 2003 · L-Isoleucine No effect
A review of trials in people with motor neuron disease found no benefit of branched-chain amino acids on survival, muscle strength or physical function.
Amino acids for amyotrophic lateral sclerosis / motor neuron disease. · The Cochrane database of systematic reviews
Systematic review · 2008 · L-Isoleucine No effect
This withdrawn review of trials in people with motor neuron disease found no benefit of branched-chain amino acids on survival, muscle strength or physical function.
WITHDRAWN: Amino acids for amyotrophic lateral sclerosis / motor neuron disease. · The Cochrane database of systematic reviews
Systematic review · 2017 · L-Isoleucine Mixed
A review of 11 studies found branched-chain amino acids could reduce exercise muscle damage when damage was low to moderate, with high daily intake for over 10 days, but results varied widely between studies.
Is Branched-Chain Amino Acids Supplementation an Efficient Nutritional Strategy to Alleviate Skeletal Muscle Damage? A S… · Nutrients
Systematic review · 2022 · L-Isoleucine Improved
In a review of 27 diet and exercise studies in people with cirrhosis, benefits for body composition were also seen with branched-chain amino acid supplements, though the largest gains came from combined diet and exercise.
The Effect of Diet and Exercise Interventions on Body Composition in Liver Cirrhosis: A Systematic Review. · Nutrients
Systematic review · 2014 · L-Leucine Mixed
A systematic review of studies in adults aged 50 and over with sarcopenia found that essential amino acid supplements containing about 2.5 g of leucine showed some improvement in muscle mass and function, though nutrition study results overall were inconsistent and few in number.
Prevalence of and interventions for sarcopenia in ageing adults: a systematic review. Report of the International Sarcop… · Age and ageing
Systematic review · 2019 · L-Leucine Mixed
A review of 23 studies found leucine or leucine-enriched protein (1.2 to 6 grams of leucine daily) was well tolerated and improved lean muscle mass in older people with sarcopenia, while strength results were mixed.
Beneficial Effects of Leucine Supplementation on Criteria for Sarcopenia: A Systematic Review. · Nutrients
Systematic review · 2021 · L-Leucine Improved
A review of 15 systematic reviews in people aged 65 and older found leucine had a significant effect on muscle mass in elderly people with sarcopenia, though evidence quality was low to moderate.
Nutritional interventions to improve muscle mass, muscle strength, and physical performance in older people: an umbrella… · Nutrition reviews
Systematic review · 2022 · L-Leucine Mixed
A review of intervention studies in older adults with sarcopenia found leucine alone without exercise did not improve sarcopenia markers, but leucine paired with protein supplements was effective.
Effect of supplementation with leucine alone, with other nutrients or with physical exercise in older people with sarcop… · Endocrinologia, diabetes y nutricion
Randomized trial · 2008 · 472 people · 8 weeks · L-Arginine No effect
In 472 advanced cancer patients, a twice-daily mix of HMB, glutamine and arginine for 8 weeks did not significantly change lean body mass versus control, though only 37% finished and there was a trend toward higher lean mass.
A randomized, double-blind, placebo-controlled trial of a beta-hydroxyl beta-methyl butyrate, glutamine, and arginine mi… · Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer
Randomized trial · 2015 · 380 people · 13 weeks · L-Leucine Mixed
In 380 older adults with sarcopenia, a vitamin D and leucine-enriched whey protein supplement taken twice daily for 13 weeks did not improve handgrip strength more than control, but increased muscle mass by 0.17 kg more and improved the chair-stand test.
Effects of a vitamin D and leucine-enriched whey protein nutritional supplement on measures of sarcopenia in older adult… · Journal of the American Medical Directors Association
Randomized trial · 2021 · 200 people · 16 weeks · L-Leucine No effect
In 200 pre-frail and frail older adults doing resistance training for 16 weeks, leucine supplementation did not improve muscle mass or function compared with placebo.
Supplement-based nutritional strategies to tackle frailty: A multifactorial, double-blind, randomized placebo-controlled… · Clinical nutrition (Edinburgh, Scotland)
Randomized trial · 2024 · 150 people · 52 weeks · L-Isoleucine No effect
In 150 people with cirrhosis, 30 grams a day of branched-chain amino acids for 12 months did not improve grip strength or muscle mass compared with whey protein.
Branched-chain amino acid supplementation does not improve measures of sarcopenia in cirrhosis: results of a randomised … · Alimentary pharmacology & therapeutics
Randomized trial · 2020 · 140 people · 4 weeks · L-Leucine Improved
In 140 older hospitalized adults with sarcopenia, a leucine and vitamin D enriched whey protein formula twice daily for 4 to 8 weeks during rehabilitation improved gait speed, muscle mass, and physical performance more than a control formula.
Improving rehabilitation in sarcopenia: a randomized-controlled trial utilizing a muscle-targeted food for special medic… · Journal of cachexia, sarcopenia and muscle
Randomized trial · 2021 · 132 people · 24 weeks · L-Isoleucine No effect
In 132 overweight or obese adults on a calorie-cut diet, branched-chain amino acids at 0.1 g per kg body weight daily for 16 weeks (plus 8 weeks of maintenance) did not significantly preserve lean mass compared with control.
Branched-Chain Amino Acid Supplementation Does Not Preserve Lean Mass or Affect Metabolic Profile in Adults with Overwei… · The Journal of nutrition
Randomized trial · 2016 · 130 people · 12 weeks · L-Leucine Improved
In 130 sarcopenic elderly people, 12 weeks of whey protein, essential amino acids including 4 grams of leucine, and vitamin D alongside exercise increased fat-free mass and grip strength and lowered an inflammation marker compared with placebo plus exercise.
Whey protein, amino acids, and vitamin D supplementation with physical activity increases fat-free mass and strength, fu… · The American journal of clinical nutrition
Randomized trial · 1984 · 96 people · 52 weeks · L-Leucine No effect
In 96 people with Duchenne muscular dystrophy followed for one year, oral leucine at 0.2 grams per kilogram daily produced no lasting therapeutic benefit compared with placebo, and early differences were attributed to a drop in the placebo group.
Clinical investigation in Duchenne muscular dystrophy: IV. Double-blind controlled trial of leucine. · Muscle & nerve
Randomized trial · 1996 · 95 people · 26 weeks · L-Isoleucine No effect
In 95 people with ALS, six months of branched-chain amino acids (including 8 g isoleucine daily) did not improve muscle strength or function compared with placebo, and lung function declined faster.
A controlled trial of amino acid therapy in amyotrophic lateral sclerosis: I. Clinical, functional, and maximum isometri… · Neurology
Randomized trial · 2022 · 81 people · 24 weeks · L-Leucine Mixed
In older adults with sarcopenia, whey and leucine supplementation after resistance training did not differ from training alone at the end of 24 weeks, but after a further 24 weeks without training, muscle mass and grip strength stayed higher in the supplement group.
De-Training Effects Following Leucine-Enriched Whey Protein Supplementation and Resistance Training in Older Adults with… · The journal of nutrition, health & aging
Randomized trial · 2017 · 80 people · 8 weeks · L-Arginine No effect
In 80 resistance-trained men, a pre-workout supplement containing 2 g arginine alpha-ketoglutarate for 8 weeks did not change body composition more than placebo, with only some early strength and thinking gains that faded by week 8.
Effects of ingesting a pre-workout dietary supplement with and without synephrine for 8 weeks on training adaptations in… · Journal of the International Society of Sports Nutrition
Randomized trial · 2009 · 77 people · 52 weeks · L-Arginine Improved
In 77 elderly men and women, a daily mix of HMB, arginine and lysine for one year increased lean mass by 1.2% and body cell mass by 1.6% versus control and raised protein turnover.
Year-long changes in protein metabolism in elderly men and women supplemented with a nutrition cocktail of beta-hydroxy-… · JPEN. Journal of parenteral and enteral nutrition
Randomized trial · 2011 · 77 people · 52 weeks · L-Arginine Improved
In 77 older adults given a combination of HMB, arginine and lysine for one year, lean body mass rose regardless of vitamin D level, but strength rose only in those with adequate vitamin D.
Vitamin D status affects strength gains in older adults supplemented with a combination of β-hydroxy-β-methylbutyrate, a… · JPEN. Journal of parenteral and enteral nutrition
Randomized trial · 2023 · 70 people · 26 weeks · L-Arginine Improved
In 70 men doing regular resistance training, 5 g of arginine before workouts for 6 months led to a 0.62% greater muscle mass gain and 1% greater body fat loss than the control group.
Oral Arginine Supplementation in Healthy Individuals Performing Regular Resistance Training. · Healthcare (Basel, Switzerland)
Randomized trial · 2000 · 68 people · 8 weeks · L-Arginine Improved
In 68 people with HIV-related weight loss (43 finished), 14 g arginine with 3 g HMB and 14 g glutamine daily for 8 weeks gave 2.55 kg lean mass gain versus a 0.70 kg loss on placebo.
Nutritional treatment for acquired immunodeficiency virus-associated wasting using beta-hydroxy beta-methylbutyrate, glu… · JPEN. Journal of parenteral and enteral nutrition
Randomized trial · 2022 · 66 people · 6 weeks · L-Arginine No effect
In 66 older adults training for 6 weeks, L-arginine did not change body measurements, strength, endurance or physical performance compared with placebo.
l-Arginine and Beetroot Extract Supplementation in the Prevention of Sarcopenia. · Pharmaceuticals (Basel, Switzerland)
Randomized trial · 2022 · 61 people · 6 weeks · L-Arginine Mixed
In 61 older adults at risk of sarcopenia over 6 weeks, L-arginine raised circulating vitamin D levels compared with placebo, but the abstract does not report a clear improvement in physical fitness tests.
Nitric-Oxide-Inducing Factors on Vitamin D Changes in Older People Susceptible to Suffer from Sarcopenia. · International journal of environmental research and public health
Randomized trial · 2018 · 60 people · L-Arginine No effect
In 60 people having open abdominal cancer surgery, a blend containing 7 grams of L-arginine a day for about 10 days before and after surgery did not reduce wound complications compared with placebo, and muscle mass and grip strength did not differ.
Perioperative Nutritional Support With Beta-hydroxy-beta-methylbutyrate, Arginine, and Glutamine in Surgery for Abdomina… · Wounds : a compendium of clinical research and practice
Randomized trial · 2022 · 60 people · 26 weeks · L-Isoleucine No effect
In 60 people with cirrhosis and muscle loss, 12 g daily of branched-chain amino acids for 6 months on top of exercise did not improve muscle mass or strength compared with placebo.
Randomised clinical trial: effect of adding branched chain amino acids to exercise and standard-of-care on muscle mass i… · Hepatology international
Randomized trial · 2022 · 60 people · 9 weeks · L-Leucine Improved
In 60 adults aged about 80 with sarcopenia, a 2-month medical food containing 2.5 grams of leucine, omega-3 fats and a probiotic increased lean limb mass, balance, walking and grip strength compared with placebo.
Effectiveness of a Novel Food Composed of Leucine, Omega-3 Fatty Acids and Probiotic Lactobacillus paracasei PS23 for th… · Nutrients
Randomized trial · 2017 · 56 people · 6 weeks · L-Arginine Improved
In 56 male soccer players, 2 grams of L-arginine daily for 45 days increased VO2 max compared with placebo, but did not change body weight or lean body mass.
The effect of l-arginine supplementation on body composition and performance in male athletes: a double-blinded randomiz… · European journal of clinical nutrition
Randomized trial · 2025 · 55 people · 12 weeks · L-Isoleucine Improved
In 55 older adults with kidney disease, 12 weeks of a leucine-rich amino acid mix (1.5 g isoleucine daily) increased lean muscle mass by 0.4 kg versus a 0.2 kg loss on placebo, with no change in strength.
Anti-sarcopenic effect of leucine-enriched branched-chain amino acid supplementation among elderly chronic kidney diseas… · International urology and nephrology
Randomized trial · 2021 · 54 people · 4 weeks · L-Isoleucine No effect
In 54 COPD patients over 4 weeks of pulmonary rehabilitation, branched-chain amino acids did not add benefit to rehabilitation alone for muscle function or exercise capacity.
Does branched-chain amino acid supplementation improve pulmonary rehabilitation effect in COPD? · Respiratory medicine
Randomized trial · 2023 · 54 people · 16 weeks · L-Isoleucine Improved
In 54 frail people with cirrhosis, 16 weeks of branched-chain amino acids (isoleucine dose not stated) compared with control increased skeletal muscle index and improved frailty scores.
Branched-chain amino acids supplementation improves liver frailty index in frail compensated cirrhotic patients: a rando… · BMC gastroenterology
Randomized trial · 2004 · 50 people · 12 weeks · L-Arginine Improved
In elderly women taking 5 grams of arginine, 2 grams of HMB and 1.5 grams of lysine daily for 12 weeks, strength and walking test scores improved and whole-body protein synthesis rose about 20% compared with placebo.
Effect of beta-hydroxy-beta-methylbutyrate, arginine, and lysine supplementation on strength, functionality, body compos… · Nutrition (Burbank, Los Angeles County, Calif.)
Randomized trial · 1990 · 50 people · L-Arginine No effect
In 50 burn patients, a tube feeding formula that included arginine reduced wound infections and stay length, but its effect on muscle mass was not statistically significant, and the arginine dose was not reported separately.
Differential effects of three enteral dietary regimens on selected outcome variables in burn patients. · JPEN. Journal of parenteral and enteral nutrition
Randomized trial · 2021 · 49 people · 2 weeks · L-Arginine No effect
In 49 older adults recovering from minor trauma, a complex containing 14 grams of arginine for two weeks did not change thigh muscle size, grip strength or daily function compared with a glutamine control.
Urinary Titin N-Fragment Evaluation in a Randomized Controlled Trial of Beta-Hydroxy-Beta-Methylbutyrate for Acute Mild … · Nutrients
Randomized trial · 2022 · 48 people · 6 weeks · L-Arginine No effect
In 48 trained young men over 6 weeks, adding L-arginine to high intensity interval training did not change body mass index, body fat or lean body mass, although it was linked to lower interleukin-6 levels.
High intensity interval training and L-Arginine supplementation decrease interleukin-6 levels in adult trained males. · La Tunisie medicale
Randomized trial · 2022 · 47 people · 12 weeks · L-Isoleucine Mixed
In 47 adults with inflammatory muscle disease over 12 weeks, branched-chain amino acids did not improve muscle strength scores compared with placebo but did produce a greater improvement in shoulder movement function.
Branched chain amino acids in the treatment of polymyositis and dermatomyositis: a phase II/III, multi-centre, randomize… · Rheumatology (Oxford, England)
Randomized trial · 2022 · 46 people · 4 weeks · L-Arginine Improved
In 46 adults with long COVID, 1.66 grams of arginine plus vitamin C twice daily for 28 days improved six-minute walk distance and handgrip strength more than placebo.
Effects of l-Arginine Plus Vitamin C Supplementation on Physical Performance, Endothelial Function, and Persistent Fatig… · Nutrients
Randomized trial · 2025 · 46 people · L-Arginine No effect
In 46 healthy trained men, a single dose of 0.15 g per kg of L-arginine with citrulline malate did not improve aerobic, anaerobic or CrossFit performance compared with placebo, except for a faster time to peak power in one sprint test.
Acute effects of combined supplementation of L-arginine and citrulline malate on aerobic, anaerobic, and CrossFit exerci… · Scientific reports
Randomized trial · 2020 · 46 people · 8 weeks · L-Isoleucine Improved
In 46 stroke patients doing two months of exercise, taking the leucine-enriched amino acid supplement with breakfast improved leg strength and balance and reduced body fat, with timing relative to exercise making no difference.
The Effects of Timing of a Leucine-Enriched Amino Acid Supplement on Body Composition and Physical Function in Stroke Pa… · Nutrients
Randomized trial · 2019 · 45 people · L-Isoleucine Mixed
In 45 older men, a single 6 gram drink of branched-chain amino acids raised muscle protein building for the first two hours after drinking, but the increase did not last to five hours, unlike milk protein.
Branched-chain amino acid and branched-chain ketoacid ingestion increases muscle protein synthesis rates in vivo in olde… · The American journal of clinical nutrition
Randomized trial · 2025 · 44 people · 2 weeks · L-Arginine Improved
In 44 adults aged 65 and older having heart surgery, taking an arginine, glutamine and beta-hydroxy-beta-methylbutyrate supplement for at least 2 weeks before surgery improved 6-minute walking distance and physical function and shortened hospital stays, without changing muscle mass.
Effects of preoperative beta-hydroxy-beta-methylbutyrate, arginine, and glutamine supplementation on cardiac surgery: A … · Clinical nutrition (Edinburgh, Scotland)
Randomized trial · 2022 · 42 people · 4 weeks · L-Arginine No effect
In 42 long-stay intensive care patients, the amount of arginine received through nutrition was not linked to muscle loss over four weeks.
Is the amino acid pattern in medical nutrition therapy crucial for successfully attenuating muscle mass loss in adult IC… · Clinical nutrition ESPEN
Randomized trial · 2005 · 40 people · 12 weeks · L-Arginine No effect
In 40 people with rheumatoid arthritis and muscle wasting, 12 weeks of a beta-hydroxy-beta-methylbutyrate, glutamine and arginine mixture was not more effective than a placebo amino acid mixture, though it caused fewer stomach complaints.
Dietary treatment of rheumatoid cachexia with beta-hydroxy-beta-methylbutyrate, glutamine and arginine: a randomised con… · Clinical nutrition (Edinburgh, Scotland)
Randomized trial · 2026 · 40 people · 1 weeks · L-Isoleucine Improved
In 40 critically ill patients, 10 days of 40 g daily branched-chain amino acids prevented thigh muscle thickness loss (0% vs 13% loss in controls) and lowered inflammation (IL-6).
High leucine branched-chain amino acids supplementation ameliorates quadriceps femoris muscle thickness reduction and at… · Clinical nutrition ESPEN
Randomized trial · 2012 · 40 people · 8 weeks · L-Lysine Mixed
In 40 young men fed controlled diets for 8 weeks, a high lysine intake (80 mg per kg daily) raised muscle strength by about 7.5% but had no effect on other measures.
The effect of a controlled 8-week metabolic ward based lysine supplementation on muscle function, insulin sensitivity an… · Clinical nutrition (Edinburgh, Scotland)
Randomized trial · 2021 · 38 people · 12 weeks · L-Arginine No effect
In 38 people with advanced lung cancer, a beta-hydroxy-beta-methylbutyrate, arginine and glutamine supplement alongside standard nutrition and exercise support showed no benefit for preserving lean body mass over 12 weeks, and the trial was halted early.
Beta-hydroxy beta-methylbutyrate/arginine/glutamine (HMB/Arg/Gln) supplementation to improve the management of cachexia … · BMC cancer
Randomized trial · 2021 · 36 people · 17 weeks · Glycine Improved
In 36 malnourished kidney dialysis patients (27 completed), 14 grams a day of glycine for 4 months raised fat-free mass index compared with branched-chain amino acids, though other measures did not change.
Glycine increases fat-free mass in malnourished haemodialysis patients: a randomized double-blind crossover trial. · Journal of cachexia, sarcopenia and muscle
Randomized trial · 2023 · 36 people · 16 weeks · Glycine Improved
In 24 older adults, 16 weeks of glycine combined with N-acetylcysteine improved antioxidant levels, mitochondrial function, inflammation, and physical function including muscle strength and walking, compared with placebo.
Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, M… · The journals of gerontology. Series A, Biological sciences and medical sciences
Randomized trial · 2022 · 36 people · 24 weeks · L-Isoleucine No effect
In 36 older adults with type 2 diabetes, 24 weeks of branched-chain amino acids (8 g daily, isoleucine dose not stated) did not change muscle mass compared with soy protein, while leg strength rose in the soy group and showed a trend upward in the amino acid group.
Effects of Branched-Chain Amino Acids on Skeletal Muscle, Glycemic Control, and Neuropsychological Performance in Elderl… · Nutrients
Randomized trial · 2020 · 36 people · 10 weeks · L-Leucine No effect
In 36 untrained midlife women over 10 weeks of resistance training, 5 grams of daily leucine added no benefit to fat-free mass, strength or hormone levels compared with placebo.
Efficacy of L-leucine Supplementation Coupled With Resistance Training in Untrained Midlife Women. · Journal of the American College of Nutrition
Randomized trial · 2006 · 35 people · 8 weeks · L-Arginine Improved
In 35 trained men taking 12 grams daily of arginine alpha-ketoglutarate with resistance training for eight weeks, bench press one-rep max and peak anaerobic power improved, but body composition did not change.
Pharmacokinetics, safety, and effects on exercise performance of L-arginine alpha-ketoglutarate in trained adult men. · Nutrition (Burbank, Los Angeles County, Calif.)
Randomized trial · 1979 · 35 people · 1 weeks · L-Isoleucine Improved
In 35 patients after surgery, five days of infusion with branched-chain amino acids (isoleucine dose not stated) prevented the muscle breakdown seen with glucose-only infusion, leaving patients in nitrogen balance and limiting weight loss.
Infusion of the branched chain amino acids in postoperative patients. Anticatabolic properties. · Annals of surgery
Randomized trial · 2024 · 34 people · 8 weeks · L-Valine Mixed
In 34 trained young adults doing resistance training for 8 weeks, hemp increased arm muscle thickness in women while soy increased it in men, so effects differed by sex.
Effects of hemp supplementation during resistance training in trained young adults. · European journal of applied physiology
Randomized trial · 2021 · 32 people · 12 weeks · L-Isoleucine Improved
In 32 people with cirrhosis and muscle loss, 12 weeks of branched-chain amino acids plus standard care increased muscle mass, with 83.3 percent of the amino acid group improving versus 46.7 percent on placebo.
Adding Branched-Chain Amino Acids to an Enhanced Standard-of-Care Treatment Improves Muscle Mass of Cirrhotic Patients W… · The American journal of gastroenterology
Randomized trial · 2019 · 31 people · 26 weeks · L-Arginine Improved
In 31 healthy adults aged 65 to 89, a daily blend containing 14 grams of L-arginine (with HMB and glutamine) for six months increased total lean body mass more than placebo and improved timed stair climbing, though thigh muscle volume did not change.
Oral Supplementation with Beta-Hydroxy-Beta-Methylbutyrate, Arginine, and Glutamine Improves Lean Body Mass in Healthy O… · Journal of dietary supplements
Randomized trial · 2022 · 30 people · L-Arginine No effect
In 30 young male athletes, a single dose of an amino acid blend with 3 grams of L-arginine did not change biceps blood flow, muscle size or muscle pump compared with placebo.
New perspectives for investigating muscular perfusion response after dietary supplement intake: an exploratory, randomiz… · Journal of the International Society of Sports Nutrition
Randomized trial · 2016 · 30 people · L-Isoleucine No effect
In 30 resistance-trained men, branched-chain amino acids with carbohydrate (1 g isoleucine daily) over three days of hard training did not reduce strength loss or soreness compared with carbohydrate alone.
Post-exercise branched chain amino acid supplementation does not affect recovery markers following three consecutive hig… · Journal of the International Society of Sports Nutrition
Randomized trial · 2021 · 30 people · 8 weeks · L-Isoleucine No effect
In 30 postmenopausal women doing 8 weeks of resistance training, 9 grams a day of branched-chain amino acids did not add to gains in muscle mass or strength compared with training plus placebo.
Effects of branched-chain amino acid supplementation and resistance training in postmenopausal women. · Experimental gerontology
Randomized trial · 2026 · 30 people · 4 weeks · L-Isoleucine Improved
In 30 healthy adults, 4 weeks of saponin extract taken with whey protein and resistance training raised isoleucine absorption by 6.33% and grip strength by 5.2% versus 2.44% with placebo, but isoleucine itself was not the tested ingredient.
Effects of Astragalus membranaceus and Panax notoginseng Saponins Extract on the Pharmacokinetics of Whey Protein Absorp… · Nutrients
Randomized trial · 2019 · 26 people · 12 weeks · L-Leucine No effect
In 26 resistance-trained young men over 12 weeks, adding 1.5 grams of leucine twice daily to whey protein produced muscle and strength gains no different from adding HMB, and HMB was no more effective than leucine.
Equivalent Hypertrophy and Strength Gains in β-Hydroxy-β-Methylbutyrate- or Leucine-supplemented Men. · Medicine and science in sports and exercise
Randomized trial · 2017 · 25 people · 1 weeks · L-Arginine Mixed
In 25 resistance-trained people, a pre-workout drink containing 1.3 grams of arginine nitrate improved some strength measures over seven days compared with placebo but did not change cycling time-trial performance.
Short-Term Effects of a Ready-to-Drink Pre-Workout Beverage on Exercise Performance and Recovery. · Nutrients
Randomized trial · 2007 · 24 people · 9 weeks · L-Isoleucine Mixed
In 24 young women on 60 days of bed rest, a protein plus branched-chain amino acid supplement (7.2 g per day) prevented loss of heart muscle mass seen in the sedentary group, but heart chamber volume still shrank, and exercise worked better.
Cardiac atrophy in women following bed rest. · Journal of applied physiology (Bethesda, Md. : 1985)
Randomized trial · 2025 · 24 people · L-Isoleucine Improved
In 24 untrained young men, taking branched-chain amino acids after resistance training reduced muscle soreness at 48 hours and lowered blood markers of inflammation at 24 hours compared with placebo, while taking them before training did not match this effect.
Effect of Timing of Branched-Chain Amino Acid Supplementation on Muscle Recovery after Resistance Training in Healthy Ma… · American journal of men's health
Randomized trial · 2026 · 24 people · 12 weeks · L-Isoleucine Improved
In 24 dialysis patients, 12 weeks of a supplement containing branched-chain amino acids (isoleucine amount not stated) at 10 g daily increased thigh muscle thickness and fat-free mass percentage compared with placebo, and lowered inflammation and oxidative stress markers.
The Combined Use of Hydroxymethylbutyrate and Branched-Chain Amino Acids to Counteract Uremic Sarcopenia. · Nutrients
Randomized trial · 2008 · 23 people · 26 weeks · L-Arginine Mixed
In 23 postmenopausal women taking 14.2 grams of L-arginine a day for six months, jump force per kilogram rose more than in the dextrose control group, while grip strength, jump power and muscle area did not change significantly.
The effect of L-arginine administration on muscle force and power in postmenopausal women. · Clinical physiology and functional imaging
Randomized trial · 2015 · 23 people · 4 weeks · L-Arginine Improved
In 23 patients having knee replacement, taking an HMB, arginine and glutamine combination for about 4 weeks after surgery helped prevent the loss of quadriceps strength seen in the control group.
Effects of supplementation with a combination of β-hydroxy-β-methyl butyrate, L-arginine, and L-glutamine on postoperati… · Asia Pacific journal of clinical nutrition
Randomized trial · 2020 · 23 people · 4 weeks · L-Arginine Improved
In 23 liver transplant patients, an HMB-enriched formula containing 7 grams of L-arginine per pack, taken for 30 days with rehabilitation, raised grip strength and muscle mass index compared with the control group.
Effect of administration of β-hydroxy-β-methyl butyrate-enriched formula after liver transplantation: A pilot randomized… · Nutrition (Burbank, Los Angeles County, Calif.)
Randomized trial · 2017 · 22 people · 12 weeks · L-Aspartic Acid No effect
In 22 resistance-trained men doing 12 weeks of lifting, 6 g daily of D-aspartic acid did not change testosterone or improve muscle growth or strength compared with placebo, and both groups gained similar muscle size.
The effects of d-aspartic acid supplementation in resistance-trained men over a three month training period: A randomise… · PloS one
Randomized trial · 1988 · 22 people · 52 weeks · L-Isoleucine Improved
In 22 people with motor neuron disease, a daily mix of branched-chain amino acids including 8 g isoleucine for one year helped maintain limb muscle strength and walking ability compared with placebo.
Pilot trial of branched-chain aminoacids in amyotrophic lateral sclerosis. · Lancet (London, England)
Randomized trial · 2025 · 20 people · L-Arginine No effect
In 20 patients with advanced liver cancer taking lenvatinib, a beverage containing a leucine metabolite, arginine and glutamine plus walking training did not reduce hand-foot skin reactions, though muscle mass was maintained somewhat better than in controls (not statistically significant).
An open-label, randomized, controlled trial on the benefit of β-hydroxy-β-methyl butyrate, l-arginine, l-glutamine combi… · Clinical nutrition ESPEN
Randomized trial · 2010 · 20 people · 0 weeks · L-Leucine No effect
In 20 resistance-trained adults, adding leucine to carbohydrate drinks before and after leg squats did not reduce muscle damage markers or soreness over 72 hours and did not change squat performance compared with placebo.
The effects of adding leucine to pre and postexercise carbohydrate beverages on acute muscle recovery from resistance tr… · Journal of strength and conditioning research
Randomized trial · 2005 · 20 people · L-Tyrosine No effect
In 20 healthy men, a single dose of tyrosine (150 mg per kg body weight) taken before a loaded treadmill march did not improve endurance, handgrip strength, or stair-stepping power compared with placebo.
Ingestion of tyrosine: effects on endurance, muscle strength, and anaerobic performance. · International journal of sport nutrition and exercise metabolism
Randomized trial · 2021 · 18 people · 12 weeks · L-Isoleucine Improved
In 18 people with rheumatic disease taking prednisolone, 12 weeks of branched-chain amino acids slowed the loss of plasma amino acids and reduced a muscle breakdown marker, and higher plasma isoleucine was linked to less thigh muscle atrophy.
Amino Acid Profile in 18 Patients with Rheumatic Diseases Treated with Glucocorticoids and BCAAs. · Journal of nutritional science and vitaminology
Randomized trial · 1995 · 18 people · L-Isoleucine Improved
In 18 preterm infants, mixed amino acids given from birth on the first day of life improved nitrogen retention and prevented protein loss compared with glucose alone, but isoleucine was not tested on its own.
Immediate commencement of amino acid supplementation in preterm infants: effect on serum amino acid concentrations and p… · The Journal of pediatrics
Randomized trial · 2010 · 17 people · 3 weeks · L-Arginine Improved
In 17 strength-trained athletes during 3 weeks of heavy resistance training, arginine and ornithine supplements raised growth hormone and IGF-1 levels after exercise compared with placebo.
Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heav… · Journal of strength and conditioning research
Randomized trial · 2021 · 17 people · 4 weeks · L-Arginine Mixed
In 17 professional water polo players taking 5 grams of L-arginine per day for 4 weeks, muscle strength and 200 meter speed did not change, but the lactate-to-speed ratio fell, suggesting better oxidative metabolism.
Effects of Chronic Supplementation of L-Arginine on Physical Fitness in Water Polo Players. · Oxidative medicine and cellular longevity
Randomized trial · 2002 · 17 people · 12 weeks · L-Isoleucine No effect
In 17 men over 65, taking an amino acid and carbohydrate drink after 12 weeks of knee strength training produced no more gain in muscle strength or thigh muscle size than the control group.
Oral amino-acid provision does not affect muscle strength or size gains in older men. · Medicine and science in sports and exercise
Randomized trial · 2017 · 16 people · L-Isoleucine Improved
In 16 resistance-trained athletes, a single dose of branched-chain amino acids (0.087 grams per kilogram of body weight) before a hard leg workout led to faster recovery of leg strength, jump height and soreness at 24 to 48 hours compared with placebo.
The effects of acute branched-chain amino acid supplementation on recovery from a single bout of hypertrophy exercise in… · Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme
Randomized trial · 2012 · 16 people · L-Phenylalanine Improved
In 16 healthy older men, a single dose of protein given during sleep raised overnight muscle protein building rates (0.045 vs 0.029 percent per hour) compared with placebo; phenylalanine was mainly used as a tracer.
Intragastric protein administration stimulates overnight muscle protein synthesis in elderly men. · American journal of physiology. Endocrinology and metabolism
Randomized trial · 2012 · 15 people · L-Arginine Mixed
In 15 men, a single 6 gram dose of L-arginine increased blood volume in the biceps during recovery from resistance exercise compared with placebo, but it did not improve strength.
Acute l-arginine supplementation increases muscle blood volume but not strength performance. · Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme
Randomized trial · 2011 · 12 people · L-Arginine No effect
In 12 trained young men, a single arginine alpha-ketoglutarate dose before resistance exercise reduced total chin-ups and reverse chin-ups compared with placebo, so it did not improve muscle endurance.
Acute arginine supplementation fails to improve muscle endurance or affect blood pressure responses to resistance traini… · Journal of strength and conditioning research
Randomized trial · 2025 · 12 people · L-Isoleucine Mixed
In 12 young adults after a single resistance workout, a branched-chain amino acid drink (including 1.5 g isoleucine) increased whole-body leucine retention compared with a collagen drink, but it did not differ from a dileucine-based amino acid formula and did not reduce muscle breakdown markers.
Dileucine-supplemented essential amino acids support whole-body anabolism after resistance exercise and serum-stimulated… · Journal of the International Society of Sports Nutrition
Randomized trial · 2010 · 8 people · 4 weeks · L-Isoleucine Improved
In 8 resistance-trained men during a 4-week period of intense training, a high branched-chain amino acid supplement was linked to higher testosterone and lower cortisol and muscle damage markers than placebo.
Amino acid supplements and recovery from high-intensity resistance training. · Journal of strength and conditioning research
Randomized trial · 2013 · 7 people · L-Arginine Improved
In 7 resistance-trained men, a single 10.2 gram dose of a glycine, arginine and ketoacid supplement before leg-press sets increased total work performed compared with placebo, with no change in one-rep maximum.
Effects of supplemental GAKIC ingestion on resistance training performance in trained men. · Research quarterly for exercise and sport
Randomized trial · 2004 · 7 people · L-Isoleucine Improved
In 7 men, drinking a branched-chain amino acid solution during and after one leg resistance workout boosted muscle growth signaling more than a placebo drink, though muscle growth itself was not measured.
Branched-chain amino acids increase p70S6k phosphorylation in human skeletal muscle after resistance exercise. · American journal of physiology. Endocrinology and metabolism
Randomized trial · 2013 · 4 weeks · L-Aspartic Acid No effect
In resistance-trained men taking 3 g of D-aspartic acid daily for 28 days alongside training, body composition, strength and sex hormones did not differ from placebo.
D-aspartic acid supplementation combined with 28 days of heavy resistance training has no effect on body composition, mu… · Nutrition research (New York, N.Y.)
Randomized trial · 2016 · 13 weeks · L-Isoleucine No effect
In heart failure patients over 3 months, 10 grams a day of branched-chain amino acids added to a resistance exercise program did not improve body composition or function beyond exercise alone.
Changes in body composition in heart failure patients after a resistance exercise program and branched chain amino acid … · Clinical nutrition (Edinburgh, Scotland)
Controlled trial · 2020 · 155 people · 8 weeks · L-Isoleucine Mixed
In 155 malnourished older adults, a branched-chain amino acid mixture for 2 months improved muscle mass, strength and performance in both groups, but beat diet advice only for cognition, mitochondrial energy production and oxidative stress.
From mitochondria to healthy aging: The role of branched-chain amino acids treatment: MATeR a randomized study. · Clinical nutrition (Edinburgh, Scotland)
Controlled trial · 2024 · 57 people · 4 weeks · L-Isoleucine Improved
In 57 people one month after sleeve gastrectomy, whey protein with branched-chain amino acids and vitamin D lost less lean mass and muscle strength than protein alone (3.8% vs 18.5% strength loss).
Adding Branched-Chain Amino Acids and Vitamin D to Whey Protein Is More Effective than Protein Alone in Preserving Fat F… · Nutrients
Controlled trial · 2022 · 54 people · 4 weeks · L-Isoleucine Improved
In 54 patients with subacute stroke, one month of branched-chain amino acid powder during rehabilitation produced greater gains in muscle mass index than matched controls who did not take it.
The Effect of Branched Chain Amino Acid Supplementation on Stroke-Related Sarcopenia. · Frontiers in neurology
Controlled trial · 2020 · 48 people · 12 weeks · L-Leucine Improved
In 48 untrained adults doing supervised resistance training three times a week for 12 weeks, 2 grams of leucine from either whey or soy protein increased body weight, lean mass and leg strength, with no difference between the two protein sources.
No Significant Differences in Muscle Growth and Strength Development When Consuming Soy and Whey Protein Supplements Mat… · International journal of environmental research and public health
Controlled trial · 2021 · 35 people · 40 weeks · L-Isoleucine Mixed
In frail older adults in care homes, a 40-week program of group exercise plus branched-chain amino acids lowered a blood inflammation marker (TNF-alpha) more than other groups, with only slight changes in strength and other measures.
Effect of Training-Detraining Phases of Multicomponent Exercises and BCAA Supplementation on Inflammatory Markers and Al… · Nutrients
Controlled trial · 2011 · 30 people · 8 weeks · L-Arginine No effect
In 30 patients after gastric bypass surgery, 24 grams twice daily of an HMB, glutamine and arginine mixture for 8 weeks did not change lean body mass or resting metabolic rate compared with no supplement.
Nutritional effect of oral supplement enriched in beta-hydroxy-beta-methylbutyrate, glutamine and arginine on resting me… · Surgical endoscopy
Controlled trial · 2001 · 28 people · 26 weeks · L-Isoleucine Improved
In 28 malnourished elderly dialysis patients, six months of branched-chain amino acids (isoleucine dose not stated) compared with placebo in a crossover design increased anthropometric measures of body size and raised blood albumin.
Oral supplementation of branched-chain amino acid improves nutritional status in elderly patients on chronic haemodialys… · Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association
Controlled trial · 2015 · 24 people · 2 weeks · L-Aspartic Acid No effect
In 24 resistance-trained men, 6 g of D-aspartic acid daily for 14 days lowered total and free testosterone, while 3 g had no significant effect.
Three and six grams supplementation of d-aspartic acid in resistance trained men. · Journal of the International Society of Sports Nutrition
Controlled trial · 1989 · 22 people · 5 weeks · L-Arginine Improved
In 22 adult men on a 5-week strength program, taking arginine and ornithine increased total strength and lean body mass compared with placebo and lowered a marker of tissue breakdown in urine.
Effects of arginine and ornithine on strength, lean body mass and urinary hydroxyproline in adult males. · The Journal of sports medicine and physical fitness
Controlled trial · 2024 · 20 people · 8 weeks · L-Arginine No effect
In 20 men in their 20s doing weight training three times a week for 8 weeks, taking arginine before training lowered systolic blood pressure and triglycerides compared with placebo, but the abstract reports no muscle mass or strength results.
Effects of arginine intake during weight training on blood variables. · Journal of exercise rehabilitation
Controlled trial · 2019 · 20 people · 4 weeks · L-Isoleucine Improved
In 20 young combat sport athletes, 5 g a day of branched-chain amino acids for 4 weeks raised muscle mass from 23.4 to 25.1 kg and improved a body cell health measure, while the control group did not change.
[The efficiency of branched chain aminoacids (BCAA) in the nutrition of combat sport athletes]. · Voprosy pitaniia
Controlled trial · 2016 · 18 people · 10 weeks · L-Valine Mixed
In 18 trained cyclists, 10 weeks of a BCAA mix with 4 g valine daily did not change lean mass but improved sprint peak and mean power compared with placebo.
Ten weeks of branched-chain amino acid supplementation improves select performance and immunological variables in traine… · Amino acids
Controlled trial · 1992 · 16 people · 3 weeks · L-Isoleucine Improved
In 16 trekkers at high altitude over 21 days, taking 2.88 grams of isoleucine daily as part of branched-chain amino acids kept lean mass rising and reduced loss of leg power compared with placebo, though body mass still fell in both groups.
Branched-chain amino acid supplementation during trekking at high altitude. The effects on loss of body mass, body compo… · European journal of applied physiology and occupational physiology
Controlled trial · 2023 · 16 people · 9 weeks · L-Isoleucine Improved
In 16 healthy young women during 60 days of bed rest, a high-protein diet with added branched-chain amino acids prevented the loss of insulin sensitivity seen with a standard diet, although lean body mass fell in both groups.
High-protein diet with excess leucine prevents inactivity-induced insulin resistance in women. · Clinical nutrition (Edinburgh, Scotland)
Controlled trial · 2015 · 14 people · L-Isoleucine Mixed
A single oral leucine-enriched branched-chain amino acid dose in 6 people with alcoholic cirrhosis and 8 controls reduced whole-body protein breakdown and reversed impaired muscle growth signaling, but muscle protein synthesis was not changed.
Metabolic and molecular responses to leucine-enriched branched chain amino acid supplementation in the skeletal muscle o… · Hepatology (Baltimore, Md.)
Controlled trial · 1999 · 12 people · L-Phenylalanine Mixed
In 12 adults, a single bout of intense leg resistance exercise raised muscle protein synthesis in both trained and untrained people, but the rise was smaller in the trained group, and breakdown rose only in the untrained group.
Resistance training reduces the acute exercise-induced increase in muscle protein turnover. · The American journal of physiology
Controlled trial · 1984 · 7 people · 8 weeks · L-Histidine No effect
In seven young men fed a very low histidine diet for 8 weeks, lean body mass did not change significantly, while nitrogen balance turned negative; two control men given 1.05 g of histidine daily for 8 weeks had stable parameters.
Long-term effects of low histidine intake on men. · The Journal of nutrition
Controlled trial · 2000 · 6 people · Glycine No effect
In six healthy young adults, an amino acid infusion raised muscle protein building, but adding extra glycine or glutamine to the infusion gave no further increase.
Intravenous glutamine does not stimulate mixed muscle protein synthesis in healthy young men and women. · Metabolism: clinical and experimental
Controlled trial · 2001 · L-Valine Improved
In a small study of patients on peritoneal dialysis, adding amino acids, mainly valine, to the dialysis fluid increased muscle protein synthesis during a single session compared with dextrose alone.
Acute effects of peritoneal dialysis with dialysates containing dextrose or dextrose and amino acids on muscle protein t… · Journal of the American Society of Nephrology : JASN
Open-label trial · 2021 · 56 people · 12 weeks · L-Leucine Mixed
In 56 sarcopenic older adults, a whey and leucine supplement for 12 weeks did not change muscle mass or grip strength more than counselled protein intake, but it improved walking speed, especially in those under 75.
Effects of adequate dietary protein with whey protein, leucine, and vitamin D supplementation on sarcopenia in older adu… · Clinical nutrition (Edinburgh, Scotland)
Open-label trial · 2019 · 55 people · L-Isoleucine Mixed
In 55 hospital inpatients with walking problems, twice-daily branched-chain amino acid jelly raised muscle mass by 4.3 percent while controls lost 2.2 percent, but daily living function did not differ between groups.
The Effect of Branched Chain Amino Acids-Enriched Nutritional Supplements on Activities of Daily Living and Muscle Mass … · The journal of nutrition, health & aging
Open-label trial · 2020 · 33 people · 5 weeks · L-Isoleucine Improved
In 33 adults with pre-sarcopenia or sarcopenia, 7.2 grams of branched-chain amino acids per day for five weeks improved muscle mass index, gait speed, and grip strength, but these gains faded after 12 weeks without the supplement.
Effects of enriched branched-chain amino acid supplementation on sarcopenia. · Aging
Open-label trial · 2014 · 8 people · 2 weeks · Glycine Improved
In eight older men with HIV, 14 days of cysteine plus glycine raised glutathione levels, improved fat and sugar burning in mitochondria, and increased forearm muscle strength.
Effect of increasing glutathione with cysteine and glycine supplementation on mitochondrial fuel oxidation, insulin sens… · The Journal of clinical endocrinology and metabolism
Open-label trial · 2021 · 8 people · 24 weeks · Glycine Improved
In eight older adults taking glycine plus NAC for 24 weeks in an open-label study, oxidative stress, inflammation and mitochondrial function improved, along with muscle strength; benefits faded after stopping for 12 weeks.
Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress,… · Clinical and translational medicine
Observational study · 2022 · 4,336 people · L-Isoleucine Improved
Among 4,336 older Chinese adults, higher dietary intake of branched-chain amino acids was linked to better grip strength and walking speed and lower risk of low muscle strength.
Association between Branched-Chain Amino Acid Intake and Physical Function among Chinese Community-Dwelling Elderly Resi… · Nutrients
Observational study · 2020 · 3,292 people · L-Histidine No effect
In 3292 Korean adults aged 50 to 64, higher skeletal muscle mass index was linked to higher total energy and branched-chain amino acid intake, with no independent link reported for histidine from food.
Estimation of Dietary Amino Acid Intake and Independent Correlates of Skeletal Muscle Mass Index among Korean Adults. · Nutrients
Observational study · 2022 · 1,140 people · L-Valine Improved
In older adults in Qingdao, China, higher dietary branched chain amino acid intake was linked to lower sarcopenia risk, and higher valine intake was linked to faster gait speed.
Branched chain and other amino acid intakes are inversely associated with sarcopenia among community elders in Qingdao, … · Asia Pacific journal of clinical nutrition
Observational study · 2022 · 310 people · L-Aspartic Acid Mixed
In two US cohorts, aspartic acid levels in the blood linked to muscle mass and strength in one group but not the other, while glutamic acid was linked to sarcopenia traits in both.
Pathway-based metabolomics study of sarcopenia-related traits in two US cohorts. · Aging
Observational study · 2022 · 300 people · L-Valine No effect
In 300 older Iranian adults, dietary branched chain amino acid intake, including valine, was not significantly linked to sarcopenia or its components of muscle mass, grip strength, or gait speed.
Association between dietary intake of branched-chain amino acids and sarcopenia and its components: a cross-sectional st… · Scientific reports
Observational study · 2025 · 257 people · L-Arginine Improved
In a cross-sectional study of 257 older adults, the highest intake of dietary arginine was linked to lower odds of sarcopenia, a condition of muscle loss.
Association between dietary intake of protein and amino acids and sarcopenia: a cross-sectional study. · PloS one
Observational study · 2020 · 189 people · L-Lysine Improved
In a cross-sectional study of 189 older adults, lower blood levels of the amino acid lysine were linked to sarcopenia (low muscle mass and strength), but this does not show that taking lysine helps.
Systemic and Metabolic Signature of Sarcopenia in Community-Dwelling Older Adults. · The journals of gerontology. Series A, Biological sciences and medical sciences
Observational study · 2025 · 142 people · 13 weeks · L-Leucine Improved
In 142 malnourished patients followed for 3 months, those taking a leucine-enriched supplement improved phase angle and rectus femoris muscle thickness more than those taking a standard supplement, though the study was observational and groups differed.
Nutritional impact of leucine-enriched supplements: Evaluating protein type through artificial intelligence (AI)-augment… · Clinical nutrition ESPEN
Observational study · 2020 · 128 people · L-Valine Mixed
In a study of 128 older women from Brazil and Italy, dietary intake of valine, leucine and isoleucine was linked to chair-stand performance only in the Italian women, so this observational link is not proof that valine builds muscle.
Association between Dietary Habits and Physical Function in Brazilian and Italian Older Women. · Nutrients
Observational study · 2018 · 29 people · L-Methionine Improved
In a retrospective review of 29 adults with short bowel syndrome on home IV feeding, muscle mass increased only when the feeding mixture supplied at least 0.06 g per kg body weight of methionine along with enough branched-chain amino acids.
Essential Amino Acid Profile in Parenteral Nutrition Mixtures: Does It Meet Needs? · Nutrients
Observational study · 2022 · 28 people · 52 weeks · L-Histidine Mixed
In 28 young Japanese women tracked through the seasons, histidine intake from food did not change with summer energy intake drops, and leg muscle weight was higher in spring and summer than in winter, though this was an observational food-record study and not a histidine supplement trial.
Relationship between Seasonal Changes in Food Intake and Energy Metabolism, Physical Activity, and Body Composition in Y… · Nutrients
Study · 2025 · 114 people · 12 weeks · L-Isoleucine Mixed
In 57 people with sarcopenia given exercise plus branched-chain amino acids, calcium and vitamin D for 12 weeks, noradrenaline rose, but the analysis was about neurotransmitter levels and did not test muscle gain against a control.
Plasma levels of adrenaline, noradrenaline, dopamine, serotonin, and cortisol in sarcopenia: comparison with non-sarcope… · Journal of the International Society of Sports Nutrition
Study · 2022 · 21 people · L-Phenylalanine No effect
In 12 lean and 9 obese people, phenylalanine was used only as a tracer to measure protein turnover, and blocking the inflammation signal interleukin-6 did not change protein turnover during rest, exercise or recovery.
Amino Acid Metabolism and Protein Turnover in Lean and Obese Humans During Exercise-Effect of IL-6 Receptor Blockade. · The Journal of clinical endocrinology and metabolism
Study · 2017 · 20 people · L-Leucine Mixed
In 8 obese men with type 2 diabetes and 12 controls, a single 20-gram essential amino acid dose raised muscle protein synthesis similarly in both groups, but the diabetes group showed a blunted cell-signaling response, so the study does not show muscle loss is explained by impaired feeding response.
Anabolic resistance does not explain sarcopenia in patients with type 2 diabetes mellitus, compared with healthy control… · Clinical nutrition (Edinburgh, Scotland)
Study · 2022 · 12 people · L-Phenylalanine Improved
In 12 young adults over 7.5-hour sessions, short walking or squat breaks during sitting increased muscle protein building from meal amino acids compared with sitting; phenylalanine was a tracer, not a tested supplement.
Walking or body weight squat "activity snacks" increase dietary amino acid utilization for myofibrillar protein synthesi… · Journal of applied physiology (Bethesda, Md. : 1985)
Study · 1989 · 9 people · 12 weeks · L-Leucine Improved
In nine men given testosterone for 12 weeks, muscle mass rose and muscle protein synthesis increased; this study tested testosterone, not leucine supplementation.
Effect of testosterone on muscle mass and muscle protein synthesis. · Journal of applied physiology (Bethesda, Md. : 1985)
Study · 2006 · L-Arginine Improved
Athletes taking an amino acid mixture at 2.2 to 7.2 grams per day for 10 to 90 days recovered faster from muscle fatigue after eccentric exercise, and blood oxygen-carrying capacity improved at the higher doses.
Amino acid mixture improves training efficiency in athletes. · The Journal of nutrition
Study · 2024 · L-Arginine Improved
A single 3.6 gram dose of an essential amino acid blend containing arginine increased muscle protein synthesis by 0.058% per hour over 3 hours in older adults.
Stimulation of muscle protein synthesis with low-dose amino acid composition in older individuals. · Frontiers in nutrition
Study · 2023 · L-Histidine No effect
In male mice, cutting dietary histidine by 67% reduced weight gain and both fat and lean mass in young lean animals, and human data showed body mass index rose with dietary histidine, so lowering histidine works against muscle gain.
Regulation of metabolic health by dietary histidine in mice. · The Journal of physiology
Study · 2017 · 4 weeks · L-Aspartic Acid Improved
In rats and muscle cells, a four-week ammonia-lowering treatment that included ornithine aspartate improved muscle mass, muscle fiber size and grip strength; this was an animal and cell study, not a human trial of aspartic acid alone.
Ammonia lowering reverses sarcopenia of cirrhosis by restoring skeletal muscle proteostasis. · Hepatology (Baltimore, Md.)

Review Totals and Summary

Members OnlyWhat buyers say

I could not find customer reviews of this specific product. It was taken off the market around 2012, and the sources I searched, including the NIH label database, Amazon and other retailer pages, held no review content for it. I am not going to invent a review summary. The only nearby feedback I found was for a different product, Health Direct Amino-Sculpt Liquid Collagen in Tart Cherry, on Amazon. It is not the same formula and should not be treated as feedback on Precision Engineered. Reviewers of that product mostly talked about taste. One called the cherry flavor horrible even after diluting it in water. Another gave four stars and said the cherry flavor does not taste like cherry, though it was less unpleasant than the original flavor. That same reviewer also said it helped with energy levels and sleep. The most you can take from this is that liquid amino products often draw complaints about harsh or artificial-tasting flavors. Buyers tend to cope by diluting them, and a few report mild subjective benefits. Those patterns come from a different product, so they say nothing reliable about Precision Engineered Liquid Aminos. A real summary would need archived reviews from retailers such as bodybuilding forums or older store pages. I could not reach those with the search tool.

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Biohacker Summary

Members Only10 of 10 recommend it

10 of 10 biohackers on our panel recommend it

Most of the panel backs the main ingredients, glycine and leucine, with glycine getting the most attention. Glycine is mainly taken for sleep, and six of them describe a dose of 2 grams before bed, while others take it for blood sugar, collagen support, calming the nervous system during a diet, and making glutathione. One panelist has raised his intake to 10 grams a day, and several pair it with NAC for antioxidant support. One panelist warns that 10 to 30 grams a day could form oxalate crystals, and two others stayed neutral on glycine. Leucine is recommended by about half the panel as the key trigger for building and keeping muscle, with doses of 2 to 4 grams per meal, or 8 to 9 grams a day, and one suggests a blend of essential amino acids with about 40% leucine; lysine, arginine and threonine are smaller ingredients in this product and drew only passing mentions.

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See all 10 biohackers →Hide the biohackers

Siim Land · Glycine · recommends
- 31 Oct 2026 · recommends · Instagram ↗
  Suggests that a higher glycine to methionine ratio appears to preferentially target visceral fat and improve insulin sensitivity.
- 29 Oct 2026 · recommends · Instagram ↗
  Recommends pairing NAC with glycine to support antioxidant activity in your sleep.
- 26 Oct 2026 · recommends · YouTube ↗
  Believes glycine is the best longevity supplement and encourages viewers to learn more about its longevity benefits.
- 25 Oct 2026 · recommends · Instagram ↗
  States that Glycine can be a useful addition for some people for sleep.
- 21 Oct 2026 · uses · YouTube ↗
  Increased his glycine supplementation to 10g a day, noting that it balances methionine and improves blood sugar and glycation.
- 19 Oct 2026 · uses · YouTube ↗
  Personally uses glycine for its health benefits, including glutathione, blood sugar glycation, and potentially sleep, and notes that it appears to have some autophagy benefits by increasing autophagy through its role in methionine metabolism.
- 19 Oct 2026 · Methionine · recommends · YouTube ↗
  Recommends keeping methionine intake slightly lower to support autophagy.
- 14 Oct 2026 · neutral · Instagram ↗
  Notes that glycine is one of the most important building blocks for collagen synthesis, making up 30% of collagen, and that 12g of glycine a day is needed for collagen turnover.
- 13 Oct 2026 · uses · Instagram ↗
  Increased his glycine intake as part of an experimental amino acid strategy.
- 13 Oct 2026 · neutral · X ↗
  Retweeted a study stating that 3 g of glycine before bed helped people fall asleep faster and reach deep sleep sooner.
- 13 Oct 2026 · Methionine · uses · Instagram ↗
  Lowered his methionine intake as part of an amino acid strategy.
- 12 Oct 2026 · uses · YouTube ↗
  Takes around 3 to 5 grams of glycine before bed, often mixed with chamomile tea, as human trials have found it can improve subjective sleep quality and shorten the time to fall asleep and enter deep sleep.
- 23 Sep 2026 · Arginine · neutral · YouTube ↗
  Explains that blood vessels normally make nitric oxide from the amino acid L-arginine through an enzyme called eNOS.
- 21 Aug 2026 · Methionine · warns · Instagram ↗
  States that methionine in excess may accelerate aging.
Ben Greenfield · Leucine · recommends
- 29 Oct 2026 · recommends · YouTube ↗
  Describes leucine as the 'ignition' that turns on the signal for muscle protein synthesis, and that a sufficient dose is needed to hit the dose response and then have other essential amino acids to maintain the signal.
- 10 Oct 2026 · Arginine · neutral · YouTube ↗
  Mentions an arginine link to thymus metabolism, noting that immune cells require a lot of arginine.
- 9 Jul 2026 · recommends · YouTube ↗
  States that leucine is the primary trigger for muscle protein synthesis and recommends an essential amino acid blend with about 40% leucine for maximum stimulation.
- 16 May 2026 · Glycine · uses · YouTube ↗
  Mentions Dr. James Di Nicolantonio's claim that glycine, at 5 to 6 grams, can help protect cell membranes against damage from oxidized oils, citing rodent studies.
- 15 Apr 2026 · recommends · X ↗
  Recommends pulsing with compounds like leucine for maintaining and building muscle and maximizing muscle protein synthesis.
- 25 Mar 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 18 Mar 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 11 Mar 2026 · Glycine · uses · X ↗
  He takes 2 grams of Glycine before bed for sleep.
- 10 Mar 2026 · Methionine · neutral · X ↗
  A new study found that lowering methionine in the diet of mice significantly increased calorie burning and weight loss, matching the metabolic effects of cold exposure.
- 4 Mar 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 25 Feb 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 18 Feb 2026 · Glycine · uses · X ↗
  He takes 2 grams of Glycine before bed for sleep.
- 11 Feb 2026 · Glycine · uses · X ↗
  He takes 2 grams of Glycine before bed for sleep.
- 7 Feb 2026 · Glycine · uses · YouTube ↗
  Includes Glycine in his Liver Complex Formula for bile production.
Thomas DeLauer · Glycine · neutral
- 27 Oct 2026 · neutral · YouTube ↗
  Explains that glycine is critical for collagen synthesis, which supports the intestinal wall, and deficiency can slow down the repair process.
- 26 Oct 2026 · recommends · YouTube ↗
  Explains that the body needs roughly 10g more of glycine per day than a typical modern diet provides, and that this deficit can lead to issues with creatine production, connective tissue repair, and sleep. He recommends increasing glycine intake.
- 19 Oct 2026 · Leucine · recommends · YouTube ↗
  Identifies leucine as the primary trigger for the mtorc1 pathway, which is the master switch for muscle protein synthesis, and recommends 2 to 3 grams per meal for those under 40, and 3 to 4 grams for those over 40.
- 14 Oct 2026 · uses · YouTube ↗
  Shifts towards glycine when cutting to keep their nervous system calm through the deficit.
- 12 Oct 2026 · neutral · YouTube ↗
  Explains that glycine is a critical amino acid for glutathione production, and the body often has a significant shortage of it, with creatine synthesis consuming a large amount of available glycine.
- 4 Oct 2026 · recommends · YouTube ↗
  Recommends glycine, either from supplements or food sources like bone broth, collagen peptides, and chicken skin, to help build up glutathione.
- 1 Oct 2026 · recommends · YouTube ↗
  Recommends taking 2 to 3 grams of glycine tonight to help fall asleep.
- 25 Sep 2026 · Leucine · neutral · Facebook ↗
  Explains that leucine is important for muscle, with beef, whey, milk, and sardines clearing the 2-3g leucine threshold per meal, and that the threshold increases with age.
- 21 Sep 2026 · Leucine · neutral · Facebook ↗
  States that leucine is what flips the switch for muscle protein synthesis, and that adding leucine and essential amino acids to a small dose of whey can match the effect of a full 25-gram dose of protein.
- 8 Sep 2026 · recommends · YouTube ↗
  Recommends taking 3 grams of glycine before bed to measurably protect brain function the next day, even when chronically underslept, and to accelerate sleep onset without sedation.
- 2 Sep 2026 · recommends · YouTube ↗
  Recommends 3 grams of glycine before bed to get into the specific sleep stage faster by dropping core body temperature, which is a trigger for testosterone production.
- 29 Aug 2026 · recommends · YouTube ↗
  Recommends taking three grams of glycine before bed to help calm the brain and improve sleep, noting its neurotransmitter and GABAergic-like effects.
- 12 Aug 2026 · recommends · YouTube ↗
  Recommends glycine, found in bone broth, to directly feed goblet cells and enterocytes.
- 6 Jun 2026 · Leucine · neutral · YouTube ↗
  Notes that leucine, an important amino acid for muscle growth, activates mTOR signaling after exercise, triggering the first step in building new muscle, and that leucine plus carbs together have the strongest signaling effect.
Dr. Eric Berg · Glycine · recommends
- 24 Oct 2026 · recommends · YouTube ↗
  Recommends Glycine as a cofactor, especially for collagen.
- 23 Oct 2026 · L-Lysine · recommends · YouTube ↗
  Recommends L-lysine because it competes with L-arginine, which the virus needs to reproduce, thus blocking the virus from getting arginine and starving it off.
- 22 Oct 2026 · Leucine · recommends · Podcast ↗
  The amino acid leucine is important for muscle growth, but getting sufficient protein is just as essential for maintaining muscle mass.
- 18 Oct 2026 · Leucine · neutral · YouTube ↗
  Mentions that animal protein provides leucine, an amino acid beneficial for muscle building.
- 23 Sep 2026 · Leucine · recommends · Podcast ↗
  Recommends getting enough leucine, a key amino acid for muscle growth, to help prevent and correct muscle loss.
- 13 Sep 2026 · neutral · Facebook ↗
  Glycine is classified as a non-essential amino acid because the body can make it, but many people are still deficient. It plays a critical role in red blood cell health, DNA and RNA production, bile salts, and glutathione, and is vital for the immune system and quality sleep.
- 13 Sep 2026 · recommends · X ↗
  States that glycine is a powerful anti-aging secret that most people don't know about, and that many people are deficient despite it being a non-essential amino acid.
- 4 Sep 2026 · neutral · Podcast ↗
  Explains that glycine is essential for bile production, glutathione production, and immune function, and that consuming high-quality collagen can help increase glycine intake rather than taking a separate supplement.
- 13 Aug 2026 · Arginine · recommends · YouTube ↗
  Recommends consuming arginine, along with proline and ornithine, in the meal that breaks a prolonged fast to get the benefits of stimulating stem cells.
- 27 Jul 2026 · neutral · Facebook ↗
  Dr. Berg states that a chronic deficiency in glycine could be the cause of joint aches, difficulty sleeping, and gut health issues, as it is essential for building collagen.
- 25 Jul 2026 · neutral · Facebook ↗
  Dr. Berg states that most glycine in the diet comes from collagen.
- 22 Jul 2026 · Leucine · neutral · Podcast ↗
  Explains that leucine is an essential amino acid that signals muscles to grow, and its requirements increase with age, making it important for maintaining muscle after menopause.
- 12 Jul 2026 · uses · YouTube ↗
  Used to take 3 grams of glycine before bed as a remedy to help with sleep, but now prefers magnesium glycinate to get both benefits.
- 15 May 2026 · neutral · Podcast ↗
  Explains that glycine is a non-essential amino acid that many people are deficient in, playing a critical role in red blood cell health, DNA and RNA production, bile salts, glutathione, immune system, and quality sleep, and that low levels can contribute to visible aging.
Bryan Johnson · Glycine · uses
- 22 Oct 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 15 Aug 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 4 May 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 2 May 2026 · uses · X ↗
  He takes 2 g of Glycine before bed for sleep.
- 21 Apr 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 15 Apr 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 14 Apr 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 8 Apr 2026 · uses · X ↗
  Takes 2 grams of glycine before bed for sleep.
- 7 Apr 2026 · uses · X ↗
  He takes 2 grams of Glycine before bed for sleep.
- 4 Apr 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
Dr. Rhonda Patrick · Leucine · recommends
- 30 Sep 2026 · recommends · YouTube ↗
  Notes that foods high in leucine are going to really support muscle protein synthesis.
- 15 May 2026 · Glycine · uses · Instagram ↗
  Rhonda takes 2 grams of Glycine before bed for sleep.
- 15 Oct 2025 · Glycine · recommends · Facebook ↗
  Recommends glycine as a better option for a sleep-promoting supplement.
- 8 Oct 2025 · Glycine · recommends · Facebook ↗
  Recommends Glycine as a sleep supplement that promotes relaxation and reduces nighttime awakenings, offering meaningful improvements to sleep quality.
- 6 Oct 2025 · Glycine · recommends · YouTube ↗
  Notes that glycine seems to promote inhibitory effects and suggests that if someone is taking amino acids at night for recovery, one with extra glycine would be better.
- 9 Sep 2025 · Aspartic Acid · warns · YouTube ↗
  States that D-Aspartic Acid, along with tribulus and fenugreek, has been disproven for its effects on testosterone.
- 2 Sep 2025 · Glycine · uses · Instagram ↗
  Uses glycine, taken about 30-60 minutes before bed, as it may improve subjective sleep quality due to its nervous system effects.
- 29 Apr 2025 · Arginine · recommends · Facebook ↗
  Recommends arginine as a blood flow enhancer that boosts nitric oxide, opens up blood vessels, and can improve how one feels during endurance or high-rep sessions, also sharpening mental clarity.
- 28 Apr 2025 · Arginine · stopped · YouTube ↗
  Notes that arginine has fallen out of favor as a performance enhancer due to bioavailability issues and concerns about cold sores, with citrulline now being the preferred approach.
- 22 Apr 2025 · Arginine · neutral · Podcast ↗
  Discusses whether nitric oxide boosters like beetroot, citrulline, and arginine work.
- 5 Dec 2024 · recommends · YouTube ↗
  Explains that Leucine is the critical signal driving robust activation of mTOR, which plays key roles in skeletal muscle growth by driving muscle protein synthesis and recovery, but also notes a study suggesting Leucine might activate mTOR in the vascular system, promoting plaque buildup.
- 30 Jul 2024 · neutral · YouTube ↗
  Highlights that leucine is an amino acid with strong signaling properties, stimulating the mTOR pathway and setting off the anabolic cascade for muscle protein synthesis.
- 27 Dec 2023 · Glycine · uses · YouTube ↗
  Uses glycine as a supplement to help with sleep.
- 3 Jul 2023 · neutral · YouTube ↗
  Mentions that leucine, a branched-chain amino acid, and other essential amino acids may be partially protective against declines in muscle mass, but not entirely effective against strength declines.
Dave Asprey · Glycine · recommends
- 5 Sep 2026 · recommends · YouTube ↗
  Recommends GlyNAC (glycine and NAC together) as very affordable amino acids that he would bet his coffee on if he had to choose just one thing for longevity, as they help the body make glutathione, the master antioxidant.
- 16 Jul 2026 · warns · Podcast ↗
  Dave discusses safe upper limits for glycine before it starts working against you, mentioning oxalate crystal and Parkinson's-like risks of overdoing it.
- 16 Jul 2026 · warns · YouTube ↗
  Dave Asprey warns that taking too much glycine, such as 10-30 grams a day, can lead to the formation of razor-sharp calcium oxalate crystals, similar to eating high-oxalate foods, and can contribute to diseases of aging.
- 4 Jul 2026 · recommends · Instagram ↗
  Recommends taking 2 grams of glycine to level out blood sugar.
- 16 May 2026 · uses · X ↗
  He takes 2 grams of Glycine before bed for sleep.
- 9 Apr 2026 · warns · YouTube ↗
  Warns that glycine can convert into oxalate via the glyioxilate pathway, contributing to kidney stones, and suggests cutting down to three grams a day or increasing lemon juice intake.
- 9 Apr 2026 · Arginine · recommends · YouTube ↗
  Dave Asprey recommends Joy Mode, an electrolyte packet for sexual performance, to be taken one packet about 45 minutes before sex, as it contains clinical doses of L-citrulline, arginine nitrate, ginseng, and vitamin C to increase nitric oxide levels.
- 21 Feb 2026 · recommends · YouTube ↗
  Recommends pairing L-theanine with the amino acid glycine to strengthen the calming effect with no sedation.
- 3 Feb 2026 · Leucine · warns · YouTube ↗
  States that very low levels of leucine are probably promoting high levels of protection against aging and diseases, but also promoting frailty, and high levels of this amino acid could be a risk for developing a number of diseases.
- 9 Jan 2026 · recommends · TikTok ↗
  States that if he had to pick three raw materials that matter most for aging, glycine would be one of them, as it helps make glutathione.
- 30 Dec 2025 · warns · YouTube ↗
  Warns that mega-dosing glycine could actually be causing more problems than it's solving due to its breakdown into oxalate.
- 24 Dec 2025 · recommends · TikTok ↗
  Recommends taking 1-2 g of glycine before meals to stabilize glucose levels.
- 5 Aug 2025 · Phenylalanine · neutral · YouTube ↗
  Mentions phenylalanine as a precursor and building block for dopamine, and that the brain synthesizes dopamine from precursors like phenylalanine.
- 17 Jul 2025 · Arginine · stopped · YouTube ↗
  Has tried arginine over the years but did not notice a significant difference in blood flow.
Dr. Mark Hyman · Leucine · recommends
- 10 Aug 2026 · recommends · YouTube ↗
  Dr. Mark Hyman, agreeing with the guest, highlights leucine as a primary amino acid important for muscle protein synthesis.
- 7 Aug 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 20 Jul 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 24 Jun 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 22 Jun 2026 · Glycine · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 10 Jun 2026 · Glycine · recommends · YouTube ↗
  Recommends glycine, an amino acid often lacking in modern diets, for its potential role in overall health.
- 3 Jun 2026 · Glycine · recommends · YouTube ↗
  Recommends supplementing with glycine, an amino acid often not obtained enough, which may have a role in overall health.
- 14 May 2026 · Glycine · uses · X ↗
  Takes 2 grams of glycine before bed for sleep.
- 13 May 2026 · Glycine · uses · X ↗
  Takes 2 grams of glycine before bed for sleep.
- 6 May 2026 · Glycine · recommends · YouTube ↗
  Notes that Paleo Valley's bone broth protein is rich in glycine, an amino acid we often don't get enough of, and that glycine may have a role in overall health.
- 24 Apr 2026 · Glycine · recommends · YouTube ↗
  Recommends glycine, an amino acid, for supporting sleep quality by helping to lower core body temperature and promote deeper, more restorative sleep.
- 14 Jan 2026 · neutral · YouTube ↗
  States that leucine is important for muscle health and is the rate-limiting amino acid for turning on the switch that starts muscle building.
- 14 Jan 2026 · Methionine · neutral · YouTube ↗
  Notes that as people age, glutathione production goes down, and they might need three times more protein in methionine.
- 27 Aug 2025 · Methionine · warns · YouTube ↗
  Notes concerns in the longevity camp about excessive methionine intake, especially if not balanced with glycine, which could theoretically impair longevity.
Andrew Huberman · Glycine · uses
- 7 Aug 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 20 Jul 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 13 Jul 2026 · uses · X ↗
  Takes 2 grams of Double Wood Glycine before bed for sleep.
- 12 Jul 2026 · uses · X ↗
  He takes 2 grams of Glycine before bed for sleep.
- 6 Jul 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 25 Jun 2026 · Leucine · recommends · YouTube ↗
  Suggests that adding free leucine, perhaps one gram in a capsule with a normal meal, can significantly boost protein synthetic response, especially for plant-based individuals.
- 22 Jun 2026 · uses · X ↗
  Takes 2 grams of glycine before bed for sleep.
- 17 Jun 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 6 Jun 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 22 May 2026 · uses · X ↗
  He takes 2 grams of Glycine before bed for sleep.
- 11 May 2026 · uses · X ↗
  Takes 2 grams of Glycine before bed for sleep.
- 30 Oct 2025 · Leucine · warns · YouTube ↗
  Suggests that leucine, because it triggers cellular growth by activating the mTOR pathway, is actually pro-aging, similar to growth hormone and testosterone, offering immediate benefits at the expense of long-term health.
- 25 Apr 2025 · Leucine · neutral · YouTube ↗
  Andrew Huberman explains that leucine is an essential amino acid important for inducing muscle protein synthesis, and it is found in high levels in sources like whey protein, beef, chicken, and eggs.
- 10 Apr 2025 · Leucine · neutral · Podcast ↗
  Discusses leucine.
Peter Attia · Glycine · neutral
- 1 Jun 2026 · neutral · Podcast ↗
  Peter reviews the evidence for select off-label medications and supplements commonly used for sleep, including glycine, magnesium, ashwagandha, and phosphatidylserine.
- 26 Sep 2025 · Leucine · recommends · YouTube ↗
  States that leucine is critical for muscle protein synthesis and recommends around 8 or 9 grams a day for optimal muscle health.
- 26 Sep 2025 · Threonine · neutral · YouTube ↗
  Mentions that threonine is important for mucin production in the gut.
- 21 Sep 2025 · Leucine · recommends · YouTube ↗
  Recommends two to three grams of leucine a day for muscle health, with optimal health probably around eight or nine grams.
- 20 Jul 2025 · neutral · YouTube ↗
  Mentions that they also see positive effects of glycine, among other things.
- 30 Aug 2024 · Leucine · neutral · YouTube ↗
  Recounts a story where a vegan doctor chastised him for suggesting ingesting five grams of leucine during a workout due to its negative effect on mTOR and potential link to cancer, which Peter Attia found amusing.
- 20 Jun 2024 · neutral · YouTube ↗
  Mentions that collagen tends to be rich in glycine, among other amino acids.
- 25 May 2024 · Leucine · warns · YouTube ↗
  Warns that there is no benefit to supplementing leucine specifically if one is already consuming enough high-quality protein, and notes that leucine tastes horrible.
- 27 Apr 2024 · Methionine · neutral · YouTube ↗
  Notes that many plant-derived proteins are low in methionine, and some meat alternatives are fortified with it.
- 24 Apr 2024 · Leucine · neutral · YouTube ↗
  Mentions that estimations suggest two to three grams of Leucine in a meal will induce a rapid increase in circulating Leucine, stimulating muscle protein synthesis.
- 22 Apr 2024 · Leucine · recommends · YouTube ↗
  Highlights that leucine content is an important factor in the anabolic response, and adding free leucine to casein can increase its anabolic effect.
- 22 Apr 2024 · Methionine · recommends · YouTube ↗
  Recommends focusing on getting enough methionine, especially for plant-based patients, to ensure adequate amino acid intake for muscle protein synthesis.
- 18 Apr 2024 · Leucine · recommends · YouTube ↗
  Recommends tracking amino acids and ensuring 2 to 4 grams per serving of leucine for muscle mass.
- 18 Apr 2024 · Methionine · recommends · YouTube ↗
  Recommends tracking amino acids and ensuring at least 1 gram of methionine per day for muscle mass.

RAL Summary

Members OnlyTier 4 for Muscle and Strength

Some amino acids in this formula, such as isoleucine, glycine and arginine, have partial human study support, but results are mixed and mostly from combinations, and there are no reviews of this product, so it stays at an emerging tier.

Take 3 servings a day to match the dose that worked in the studies.

Emerging: not enough evidence to rank higher yet.

Where the evidence disagrees: 44 of the 146 human studies found no effect.

More Details

Members OnlyBody systems · Combine with · Possible side effects

Body systems: Muscular system

Combine with: To support muscle building and recovery, which is the actual strength of this BCAA product, pair it with creatine monohydrate for strength and power, whey or a complete protein for the full essential amino acid profile, and vitamin D3 and magnesium for muscle function and recovery. Electrolytes can help with hydration during training. If sexual function is still the goal, add separate targeted ingredients such as L-citrulline or L-arginine for nitric oxide and blood flow, Panax ginseng, zinc, and a doctor-guided evaluation of any persistent erectile concerns.

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Possible side effects: No major side effects reported.

Supplement Facts

L-Alanine 1306 mg · L-Arginine 1197 mg · L-Aspartic Acid 699 mg

Supplement Facts

Serving Size 2 Tbsp

Servings Per Container 15

Amount Per Serving% Daily Value

Calories	60
Protein	16 g
Sodium	55 mg
L-Alanine	1,306 mg	†
L-Arginine	1,197 mg	†
L-Aspartic Acid	699 mg	†
L-Glutamic Acid	1,554 mg	†
Glycine	3,622 mg	†
L-Histidine	139 mg	†
L-Hydroxylysine	233 mg	†
L-Isoleucine	186 mg	†
L-Leucine	404 mg	†
L-Lysine	513 mg	†
L-Methionine	139 mg	†
L-Phenylalanine	248 mg	†
L-Proline	2,130 mg	†
L-Serine	528 mg	†
L-Threonine	295 mg	†
L-Tyrosine	93 mg	†
L-Valine	342 mg	†

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† Daily Value not established.

Other ingredients: Purified Water, Hydrolyzed Gelatin, Citric Acid, Artificial flavor, Sodium Benzoate, Potassium Sorbate.

Directions: Shake well before using. DIRECTIONS: For adults, take two (2) tablespoons (30 mL) three times daily, diluted with water.

Barcode (UPC) 074312708374 · Label source: NIH label database · Report a label change

Show entire label

The Precision Engineered Liquid Aminos Wild Cherry Flavor label, 16 fl. Oz.; 473 mL — Label record: Liquid Aminos Wild Cherry Flavor, 16 fl. Oz.; 473 mL, in the Label Database ›

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Our articles on this subject

Peter Attia's Supplement List: What He Takes and What the Trials SayArticle · Sep 20, 2026
Layne Norton's Supplement Stack, Reviewed: The Three-Item Core, What He Refuses to Take, and What the Evidence SupportsArticle · Oct 2, 2026

Graded November 4, 2026 by the Reverse Age Lab evidence engine, from human studies, real reviews and our biohacker panel. How we grade. Is this medical advice? No. Rala organizes the published evidence; go over any change with your doctor, especially if you take meds.

Precision Engineered Liquid Aminos Wild Cherry Flavor Review

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