What are BCAAs?
BCAAs are three essential amino acids — leucine, isoleucine, and valine — that the body cannot synthesise and must obtain through diet or supplementation. They are found in high concentrations in meat, eggs, and dairy. Leucine is the primary driver of muscle protein synthesis among the three.
How they work
Leucine activates the mTOR signalling pathway, which stimulates muscle protein synthesis. BCAAs are metabolised directly in muscle tissue rather than the liver, making them rapidly available as an energy substrate during exercise. They may also reduce exercise-induced muscle damage and decrease perceived exertion.
What the research says
- BCAAs stimulate muscle protein synthesis, but to a lesser extent than a complete protein source providing equivalent leucine (Wolfe, 2017)
- Reduced muscle soreness and damage markers after resistance exercise in some studies
- Benefits are largely negated when total daily protein intake is adequate (1.6g+ per kg bodyweight)
- Most effective for fasted training or individuals with low dietary protein intake
Effective dose
5–10g at a 2:1:1 ratio of leucine to isoleucine to valine. For most people who eat sufficient protein, BCAAs provide little additional benefit. A 25–30g serve of whey protein delivers approximately 5–6g of BCAAs plus all other essential amino acids — making it a more complete and cost-effective option.
What to check on the label
Confirm the leucine:isoleucine:valine ratio. 2:1:1 is the most researched ratio. Products with very high leucine ratios (e.g. 8:1:1) are not supported by stronger evidence. Flavoured BCAA products often contain significant amounts of sugar or artificial sweeteners — check the full ingredient list.
Safety
Safe at recommended doses for healthy adults. No established upper limit for supplemental use. Excessive intake is unnecessary and provides no additional benefit once muscle protein synthesis is maximised.