Recent studies on branched-chain amino acids (BCAAs) have provided important insights into their effects on metabolic health, muscle function, and disease risk. BCAA supplementation has been shown to benefit muscle mass and strength in older adults, as indicated by a systematic review and meta-analysis of 35 studies (Eur J Nutr. 2022). Moreover, BCAA supplementation helps reduce muscle damage markers and soreness following resistance exercise in trained males, further supporting its role in muscle recovery (Nutrients. 2021). These findings underline the potential of BCAAs in enhancing physical performance and recovery.

However, elevated BCAA levels have been linked to several metabolic disorders. A Mendelian randomization study established a causal relationship between high BCAA levels, particularly isoleucine, and an increased risk of hypertension (J Am Heart Assoc. 2024). Additionally, higher circulating BCAA levels were associated with a higher risk of developing type 2 diabetes (Nutrients. 2022). Elevated isoleucine levels were also found to be linked with a higher risk of cardiovascular disease in adults under 60 years old (Atherosclerosis. 2022). These associations suggest that while BCAAs can be beneficial for muscle health, they may pose risks for metabolic diseases.

Interestingly, two studies reported no significant association between dietary BCAAs and all-cause mortality. One systematic review and meta-analysis found no link between serum BCAA levels and all-cause mortality (Amino Acids. 2023). Another study reported no significant association between dietary BCAAs and the risk of various cancers or all-cause mortality (Nutr Cancer. 2024). These findings highlight the complex role of BCAAs in health and disease, warranting further research to elucidate their impact.

Lifespan studies provide additional context for BCAA’s effects. Research on mice has shown that dietary restriction of isoleucine promotes metabolic health, reduces frailty, and extends lifespan (Cell Metab. 2023). Another study demonstrated that lifelong BCAA restriction increased lifespan and reduced frailty in male mice, with limited effects observed in female mice (Nat Aging. 2021). These findings suggest that BCAA restriction could have geroprotective effects, although more research is needed to confirm these benefits in humans.

Finally, elevated BCAA levels have been shown to suppress breast tumor growth and metastasis in mice, indicating potential therapeutic benefits (Front Oncol. 2022). This finding underscores the need for a nuanced understanding of BCAAs, as their effects can vary widely depending on the context and health conditions.