# Branched-chain amino acids (BCAAs)

The branched-chain amino acids (BCAAs) are leucine, isoleucine, and valine. They are essential amino acids, rich in meat, dairy, eggs, and the protein supplements you might buy. Leucine in particular strongly activates mTORC1 and drives muscle protein synthesis. That is the basis for taking BCAAs in sport, and in clinical muscle-loss (sarcopenia). But there is a flip side. Observational human studies and rodent work link high blood or dietary BCAAs to insulin resistance and type 2 diabetes risk. In mice, Solon-Biet et al. (2019, Nature Metabolism) showed that chronic high-BCAA diets shorten lifespan. The cause was indirect, through amino-acid imbalance and overeating, not direct toxicity. So it is BCAA balance, not the absolute amount, that drives the metabolic effect. And there is no EU health claim for BCAA supplements.

## Sources

- Solon-Biet SM, Cogger VC, Pulpitel T, et al.. (2019). Branched-chain amino acids impact health and lifespan indirectly via amino acid balance and appetite control. Nature Metabolism. https://doi.org/10.1038/s42255-019-0059-2
- Newgard CB, An J, Bain JR, et al.. (2009). A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance. Cell Metabolism. https://doi.org/10.1016/j.cmet.2009.02.002
- Choi BH, et al.. (2024). The role of BCAA metabolism in metabolic health and disease. Experimental & Molecular Medicine. https://doi.org/10.1038/s12276-024-01263-6

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