L-Leucine (standalone)
What it is
The primary nutritional activator of mTORC1, the intracellular kinase complex that triggers muscle protein synthesis (MPS). A leucine threshold of approximately 2–3 g per meal is required to maximally stimulate MPS — meals providing less fail to build muscle regardless of total protein content. Adding 2.5 g L-leucine to a low-protein meal in older adults increases MPS to the same level as a high-protein meal. Particularly important for: vegans (plant proteins have 30–50% lower leucine content than animal proteins), adults over 65 (higher leucine threshold needed for equivalent MPS response), and those spreading protein across many small meals.
Dose
2–3 g pure L-leucine added to each protein meal or protein shake; older adults may need 3–4 g per serving
Time of day & tips
Add to protein shakes, oatmeal, or low-protein meals to activate muscle protein synthesis. Particularly valuable for plant-based eaters — add to pea protein or rice protein shakes. For adults over 65, prioritise 3 g leucine per meal to overcome the anabolic resistance of aging.
Cycling
Safe for continuous daily use indefinitely. Can be used with every protein-containing meal for maximum muscle-sparing effect.
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