💊 What it does
Branched-chain amino acids (BCAAs) — leucine, isoleucine, and valine — are essential amino acids that cannot be synthesised by the body. Leucine specifically is the primary anabolic trigger for muscle protein synthesis, activating the mTOR signalling pathway. BCAAs are found in all complete protein sources. The evidence for BCAA supplementation shows benefits primarily when total protein intake is inadequate — when overall protein needs are met through food, BCAA supplements add little benefit over and above whole protein sources.
👤 Who needs it
Plant-based athletes with low total protein intake who struggle to meet leucine thresholds from food alone. People who train fasted. Those doing extended endurance exercise where muscle protein breakdown is significant. However — for most athletes meeting protein targets through soya, legumes, tofu, tempeh, and seitan, BCAA supplements are unnecessary.
🥦 Food sources first
Leucine: soya products (tofu, tempeh, edamame), lentils, chickpeas, pumpkin seeds, quinoa, peanuts. Isoleucine and valine: similar plant sources. Soya protein is the most leucine-rich plant protein source and most closely matches animal protein in amino acid profile. A diet including regular soya products, legumes, and adequate total protein will provide all BCAAs needed without supplementation.
🗓 When to supplement
Only when total protein intake is genuinely insufficient and BCAA-rich foods cannot be increased. As a convenience supplement for fasted training. For plant-based athletes specifically targeting leucine thresholds for muscle protein synthesis — 2.5–3 g leucine per meal is the approximate threshold.
🏷 Best form to look for
2:1:1 ratio (leucine:isoleucine:valine) is standard. Some products offer higher leucine ratios (3:1:1 or leucine-only) based on leucine's primacy in mTOR activation. Powder form mixed in water is cost-effective.
⏰ When to take it
Around training — pre, intra, or post-workout. With meals if used to boost leucine content of lower-leucine plant protein meals.