To optimally stimulate muscle protein synthesis, one must consume a sufficient amount of leucine, which often makes the bioavailability and amino acid profile of animal proteins more effective than those of plant proteins.

noli's read

Leucine is indeed the key 'trigger' amino acid for activating the mTOR pathway, which is responsible for muscle building, as confirmed by numerous studies on protein metabolism (e.g., Norton & Layman, scientific journal). It is accurate that animal proteins generally exhibit a higher leucine density and digestibility than plant sources, meaning that a larger food volume of plant matter is required to reach the same activation threshold (meta-analysis, Journal of the International Society of Sports Nutrition). The statement is scientifically grounded in the 'leucine threshold' concept. However, the term 'necessary' can be nuanced: it is entirely possible to stimulate protein synthesis using plant sources, provided that quantities are adjusted or sources are combined to compensate for the amino acid profile. This is not a biological impossibility, but a matter of volumetric efficiency.

the sources

1. 1Lim MT, Pan BJ, Toh DWK, Sutanto CN, Kim JE 2021
2. 2Tagawa R, Watanabe D, Ito K, et al. 2020
3. 3Rutherfurd SM, Fanning AC, Miller BJ, Moughan PJ 2015