Leucine is the key amino acid for stimulating muscle protein synthesis (MPS), but it is not necessary to use supplements to obtain it.

noli's read

The advice is based on a solid understanding of muscle physiology: leucine acts as an essential metabolic trigger to initiate protein synthesis. Research, particularly that published in journals such as 'Nutrients' (a reference cited by the author), confirms that a varied diet is more than sufficient to reach the necessary thresholds, even in older individuals, making supplements often superfluous for the general population. What holds true is the superiority of complete protein sources (meat, dairy products, legumes) which offer a synergistic amino acid profile. The aspect that is potentially exaggerated in the wellness community is the excessive focus on isolating leucine at the expense of total protein intake. There is no evidence that adding free-form leucine is systematically more effective than an adequate dose of high-quality dietary protein. Science here supports a pragmatic and accessible 'food-first' approach.

the sources

No named source held this one up — that absence is part of the verdict.