BCAAs and EAAs: Do You Need Amino Acid Supplements?
Do BCAAs or EAAs help build muscle? The science on whether amino acid supplements are worth taking if you already eat enough protein.
Branched-chain amino acids (BCAAs) and essential amino acids (EAAs) are among the most popular gym supplements. But do they actually help? The answer depends almost entirely on whether you are already eating enough protein.
What Are BCAAs?
BCAAs are three amino acids - leucine, isoleucine, and valine - that have a branched chemical structure. They make up about 35% of the essential amino acids in muscle tissue.
- Leucine is the most important: it is the primary trigger for muscle protein synthesis (MPS).
- Isoleucine plays a role in glucose uptake by muscle cells.
- Valine competes with tryptophan for brain uptake, which may reduce central fatigue.
A typical BCAA supplement provides 5–10g per serving in a 2:1:1 ratio (leucine:isoleucine:valine).
What Are EAAs?
EAAs are all nine essential amino acids - the ones your body cannot produce and must get from food:
- Leucine
- Isoleucine
- Valine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Histidine
BCAAs are a subset of EAAs. An EAA supplement contains all nine, including the three BCAAs.
Do BCAAs Build Muscle?
Here is where the evidence gets clear - and perhaps surprising:
When BCAAs Do NOT Help
If you eat enough total protein (0.7+ g/lb or 1.6+ g/kg per day from food and/or protein powder), BCAAs provide no additional muscle-building benefit. A systematic review by Wolfe (2017) concluded:
"The claim that consumption of dietary BCAAs stimulates muscle protein synthesis or produces an anabolic response in human subjects is unwarranted." (Wolfe, 2017, JISSN)
The reason: MPS requires all essential amino acids, not just leucine. Consuming BCAAs alone actually pulls the other EAAs from your existing muscle protein to complete the synthesis process - which can paradoxically increase muscle protein breakdown.
When you eat a chicken breast, eggs, or a whey shake, you get all the BCAAs you need - plus the other six EAAs required for complete muscle building.
When BCAAs Might Help
BCAAs may have a role in very specific situations:
- Fasted training - if you train on an empty stomach, BCAAs taken before or during the session may reduce muscle breakdown. But eating a meal 1–2 hours before training achieves the same thing.
- Very low protein diets - if total protein intake is below 0.55g/lb (1.2g/kg) per day, supplemental BCAAs could partially compensate. But the real solution is to eat more protein.
- Long endurance exercise - some evidence that BCAAs reduce central fatigue during prolonged exercise (2+ hours), though results are mixed.
Are EAAs Better Than BCAAs?
If you are going to supplement with amino acids at all, EAAs are the better choice because they provide the complete set needed for MPS - not just three of the nine.
A study by Jackman et al. (2017) found that EAAs stimulated MPS to a significantly greater degree than BCAAs alone after resistance exercise (Jackman et al., 2017, Frontiers in Physiology).
However, the same caveat applies: if you eat enough total protein from food and shakes, EAA supplements are redundant.
BCAAs/EAAs vs. Protein Powder
| Feature | BCAAs (5g) | EAAs (10g) | Whey Protein (25g) |
|---|---|---|---|
| Total amino acids | 5g (3 types) | 10g (9 types) | 25g (all types) |
| Leucine | ~2.5g | ~3g | ~2.5–3g |
| Calories | 20 | 40 | 110 |
| Stimulates MPS? | Poorly alone | Yes | Yes |
| Complete protein? | No | Yes | Yes |
| Cost per serving | $0.50–1.00 | $0.75–1.50 | $0.50–1.00 |
A scoop of whey provides everything an EAA supplement does plus extra amino acids, for a similar price. For most people, whey is simply a better investment.
So Who Should Take BCAAs or EAAs?
You probably do NOT need them if:
- You eat 0.7+ g/lb (1.6+ g/kg) per day of protein from food and powder
- You eat protein within a few hours of training
- You use whey or casein protein powder
You might consider EAAs if:
- You train fasted and want an intra-workout option with minimal calories
- You are vegan and want to ensure all essential amino acids are covered (though a quality plant protein powder does this too)
You should skip BCAAs in almost all cases - EAAs are superior for the same price.
The Bottom Line
For the vast majority of people who eat adequate protein, BCAA and EAA supplements are unnecessary. Your food and protein shakes already provide all the amino acids you need. Spend your supplement budget on creatine and quality protein powder instead - these have far stronger evidence for muscle growth. Track your protein intake with Protein Pal to confirm you are hitting your target before adding any supplement.