Protein & Amino Acids
BCAAs (Leucine / Isoleucine / Valine)
Redundant if protein intake is sufficient. Leucine specifically drives MPS — but you get more of it from whey protein at lower cost.
Effective Dose
5–10g / serving
per clinical evidence
Evidence Level
Limited
Protein & Amino Acids
Mechanism
Leucine-driven MPS (partial)
primary action
Best For
Fasted training
Vegan diets, Intra-workout
This profile is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications.
What Is BCAAs (Leucine / Isoleucine / Valine)?
BCAAs — leucine, isoleucine, and valine — are three of the nine essential amino acids and are unique in being metabolised primarily in skeletal muscle rather than the liver. Leucine is the key MPS trigger; isoleucine and valine provide supporting roles in glucose metabolism and immune function. However, as isolated supplements they are largely outperformed by complete protein sources.
How It Works: The Science
Leucine activates mTORC1 via the Ragulator–Rag GTPase complex, initiating translation of muscle protein mRNA. However, sustained MPS requires all essential amino acids as substrates — BCAAs alone can trigger the signal but cannot sustain synthesis without the other EAAs. This is why complete protein (whey, EAAs) outperforms BCAAs for net muscle protein balance.
Primary Mechanism
Leucine-driven MPS (partial)
Evidence-Based Benefits
Dosage Guide
Effective Dose
5–10g / serving
5–10g per dose. Standard 2:1:1 ratio (leucine:isoleucine:valine) is most studied. High-leucine ratios (4:1:1, 8:1:1) are marketed for enhanced MPS but offer little practical advantage over consuming adequate total protein.
Safety Profile & Side Effects
Safe at standard doses. Chronic very high intake of BCAAs (>20g/day) has been theoretically linked to metabolic disruption in some animal studies, but not replicated in human trials at normal supplement doses.
Who Should (and Shouldn't) Take It
Useful for fasted training, vegans with low dietary leucine, or intra-workout use during long sessions. Not worth supplementing if you already hit 1.6g/kg protein per day from food and whey — you are paying for what you already get.
Frequently Asked Questions
Related Ingredients
Medical Disclaimer
Ingredient profiles are for informational purposes only and do not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications. Full disclaimer →