Research

Hormonal

Leucine acts as the primary trigger for muscle protein synthesis by activating the mTORC1 pathway, and increasing leucine content in lower-quality proteins can restore the anabolic response in older adults.

Ensure your meals contain enough leucine, the 'trigger' for muscle building. High-quality proteins like whey, eggs, and meat are naturally rich in leucine. If you rely on plant proteins or lower-quality sources, you may need to consume larger portions or combine them to get enough leucine, especially as you age.

GoodSupportsHIGH confidence
The hypothesis stipulates that MPS activation is a function of leucine concentration within the intracellular AA pool [59,64]. Currently, it is known that the increase in intercellular concentration of leucine signals to activate MPS through a mechanism involving the regulation of the mechanistic target of rapamycin (mTOR) [74].
Sophie Joanisse et al. · Clinical Nutrition Open Science · 2021

Why this rating

Well-established mechanistic pathway supported by multiple studies cited.

Source

Understanding the effects of nutrition and post-exercise nutrition on skeletal muscle protein turnover: Insights from stable isotope studies

Sophie Joanisse et al. · Clinical Nutrition Open Science · 2021

DOI 10.1016/j.nutos.2021.01.005

narrative_reviewCited 38×
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DOI resolved against Crossref · corpus check 2026-06-10

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