| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Muscle Protein Synthesis Multiple human trials using isotope tracer methodology consistently demonstrate that EAA supplementation (6-15g) acutely stimulates muscle protein synthesis (MPS). A meta-analysis of four tracer studies found that a 100% increase in peripheral EAA concentrations increases fractional synthesis rate by ~34% (Church et al. 2020). An RCT in 50 older adults showed EAA supplementation acutely increased MPS both before and after a 24-week intervention (Markofski et al. 2019). The ISSN position stand (2023) confirmed MPS stimulation occurs at doses as low as 1.5-3g and plateaus around 15-18g, with free-form EAAs producing a greater MPS response than equivalent intact protein. | Improves (the measure goes up) | Moderate effect | 7 studies | 350 people | ||
Studies that measured muscle protein synthesis
| ||||||
| Lean Body Mass Two meta-analyses examined EAA/protein supplementation effects on lean body mass in older adults with mixed results. Xu et al. (2014, 9 studies) found a non-significant increase of only 0.34 kg lean body mass vs. placebo. Cheng et al. (2018, 39 RCTs, 4,274 participants) found EAA supplements may improve fat-free mass (SMD 0.21-0.27, P<0.005), though high heterogeneity and few studies with low risk of bias limit conclusions. EAAs were the most effective supplement type. A 24-week RCT in older adults found no significant change in total or regional lean body mass (Markofski et al. 2019). | Improves (the measure goes up) | Small effect | 4 studies | 4,500 people | ||
Studies that measured lean body mass
| ||||||
| Muscle Strength Evidence for EAA supplementation on muscle strength is mixed. Cheng et al. (2018, meta-analysis of 39 RCTs) found modest improvements in muscle strength in older adults with acute or chronic conditions. However, Xu et al. (2014, meta-analysis) found negligible strength improvements in leg press and leg extension (2.14 kg and 2.28 kg respectively, not significant). An RCT combining EAA with aerobic exercise was the only treatment group to significantly increase muscle strength in older adults, suggesting exercise is needed for strength gains (Markofski et al. 2019). | Improves (the measure goes up) | Small effect | 3 studies | 4,000 people | ||
Studies that measured muscle strength
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Supplement
Essential amino acids are the nine protein building blocks your body cannot make, so they must come from food. Most people look at them for muscle, and human trials using tracer methods consistently found that they boosted muscle protein synthesis in the short term, with moderate evidence. Findings for lean mass and strength in older adults were mixed and limited, so that short-term boost has not clearly become bigger muscles.
Sources: PMID 25926508; PMID 35820048
- Updated
- How we grade
- 10 studies cited
- Best evidence
- Grade B
- Conditions studied
- 2
- Outcomes
- 5
- Graded outcomes
- 0140
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Physical Function in Elderly A systematic review and meta-analysis (Cheng et al. 2018, 39 RCTs, 4,274 participants) found that protein and EAA supplements may improve physical function in older adults with acute or chronic conditions, with EAAs being the most effective supplement type. Small beneficial effects were observed even without concurrent rehabilitation exercise. However, only 7 studies had low risk of bias, and no effect of supplementation was found on any outcomes when examining high-quality evidence alone. Undernourished elderly individuals benefitted most. | Improves (the measure goes up) | Small effect | 3 studies | 4,274 people | ||
Studies that measured physical function in elderly
| ||||||
General
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Post-Exercise Recovery Several human studies support EAA supplementation for exercise recovery. Børsheim et al. (2002) showed that 6g EAA taken 1-2 hours after resistance exercise increased net muscle protein balance proportionally more than arterial amino acid concentrations, with EAA alone producing double the response of a mixed EAA/non-essential amino acid supplement. The ISSN position stand (2023) concluded that EAA supplementation within the context of exercise enhances recovery of muscle function and decreases proxy markers of muscle damage and soreness. | Improves (the measure goes up) | Moderate effect | 2 studies | 200 people | ||
Key findings
- Muscle Protein SynthesisImproves (the measure goes up)
- Lean Body MassImproves (the measure goes up)
- Muscle StrengthImproves (the measure goes up)
Safety notes in the studies
- (2018, 39 RCTs, 4,274 participants) found EAA supplements may improve fat-free mass (SMD 0.21-0.27, P<0.005), though high heterogeneity and few studies with low risk of bias limit conclusions.
- However, only 7 studies had low risk of bias, and no effect of supplementation was found on any outcomes when examining high-quality evidence alone.
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Third-party tested Essential amino acid (EAA) products, in the forms the graded studies used where we can match them.
- Grade B
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Studies cited
10 studies from PubMed
- Understanding Dietary Protein Quality: Digestible Indispensable Amino Acid Scores and Beyond.
- Consideration of the role of protein quality in determining dietary protein recommendations.
- International Society of Sports Nutrition Position Stand: Effects of essential amino acid supplementation on exercise and performance
- Seaweed proteins are nutritionally valuable components in the human diet.
- Essential Amino Acids and Protein Synthesis: Insights into Maximizing the Muscle and Whole-Body Response to Feeding
- Effect of Aerobic Exercise Training and Essential Amino Acid Supplementation for 24 Weeks on Physical Function, Body Composition, and Muscle Metabolism in Healthy, Independent Older Adults: A Randomized Clinical Trial
- Systematic review and meta-analysis of the effect of protein and amino acid supplements in older adults with acute or chronic conditions
- Effective translation of current dietary guidance: understanding and communicating the concepts of minimal and optimal levels of dietary protein.
- Clinical effectiveness of protein and amino acid supplementation on building muscle mass in elderly people: a meta-analysis
- Essential amino acids and muscle protein recovery from resistance exercise