Leucine

Leucine is the PRIMARY amino acid trigger for muscle protein synthesis — it directly activates mTORC1 via the Sestrin2 sensor. The 'leucine threshold' concept: ~2.5-3g leucine per meal is needed to maximally stimulate MPS in young adults (4-5g in elderly). This is WHY whey protein beats plant protein for muscle — whey has 11% leucine vs pea's 8% vs rice's 8%. Supplemental leucine (2.5-5g) added to low-protein meals rescues the MPS response. NOT useful in addition to high-protein meals (already at threshold). --- *Reviewed by the Dose AI Research Team and Clinical Advisory Board* *Last updated: 2026-04-06*