Evidence supporting the use of: L-leucine
For the health condition: Body Building

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Synopsis

Source of validity: Scientific
Rating (out of 5): 4

L-leucine is one of the three branched-chain amino acids (BCAAs) and is widely recognized for its role in muscle protein synthesis, which is a critical process in bodybuilding. Scientific studies have demonstrated that leucine acts as a key regulator of the mTOR pathway, a central signaling mechanism that stimulates muscle protein synthesis following resistance exercise. Supplementation with leucine—either alone or as part of a BCAA mixture—has been shown to increase muscle protein synthesis rates, particularly when taken in conjunction with protein-rich meals or post-workout.

In several controlled trials, leucine supplementation has resulted in modest improvements in muscle mass preservation during calorie restriction and in the elderly. For younger athletes and bodybuilders, evidence suggests that leucine can enhance the anabolic response to protein intake, making it a popular supplement for those seeking to maximize muscle growth and recovery. However, it is important to note that while leucine supplementation can augment the effects of dietary protein, consuming high-quality, protein-rich foods generally provides sufficient leucine for most individuals engaged in regular resistance training.

The evidence supporting the use of leucine for bodybuilding is robust, with a number of human studies and mechanistic research backing its efficacy. However, its benefits are most pronounced in the context of inadequate protein intake or in populations at risk of muscle loss. For those already consuming optimal protein, the incremental gains from additional leucine may be limited.

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