Leucine – The Most Important BCAA and the Ideal Timing

Leucine – The Most Important BCAA and the Ideal Timing

Anabolism, the process of building complex molecules from simpler ones, is a fundamental biological mechanism. In the human body, anabolic pathways play a vital role, particularly in muscle growth. This process involves synthesizing intricate muscle proteins from basic units called amino acids. The accumulation of muscle proteins, a result of anabolic activities, is a driving force behind muscle growth.

In the realm of diet and exercise, the impact of one of the three BCCA’s, the amino acid leucine and it’s effect on muscle protein levels has been widely studied. Particularly during and after weight training, leucine consumption has been shown to significantly increase muscle protein synthesis. This effect is attributed to leucine's ability to activate mTOR, a nutrient-sensing molecule that promotes muscle protein synthesis while inhibiting muscle protein breakdown. Consequently, muscle protein accumulation is triggered, leading to muscle growth.

However, the assumption that more leucine consumption equates to greater muscle growth is misguided. Consuming leucine before exercise can have adverse effects on energy availability within muscle cells. Leucine prompts the conversion of glucose into glycogen while preventing glycogen breakdown into glucose. As a result, the energy required for muscular contractions is compromised, leading to reduced strength output and potentially hindering muscle mass and strength gains.

Insulin, a potent muscle-building hormone, is crucial for muscle growth. It activates muscle protein synthesis through a signaling cascade involving mTOR. Leucine consumption can influence insulin sensitivity. High leucine intake, especially from branched-chain amino acids like leucine, has been linked to insulin resistance. This resistance reduces insulin's anabolic properties, hindering muscle protein accumulation and consequently, muscle growth.

Furthermore, leucine consumption before workouts can affect the central nervous system. Exercise-induced fatigue is linked to increased serotonin release in the brain. While it was once believed that elevated serotonin levels alone caused fatigue, recent studies show that the ratio of serotonin to dopamine plays a more significant role. Dopamine enhances mental arousal, motor control, and motivation, all of which positively impact exercise performance. Leucine competes with dopamine production, resulting in lower dopamine levels and potential sluggishness, thus affecting physical performance.

To optimize muscle growth, the timing of leucine consumption is crucial. Leucine consumption during and after resistance training prevents muscle breakdown and promotes post-workout muscle protein synthesis, enhancing muscle growth. However, consuming leucine before exercise has drawbacks that can negatively affect workout performance. This emphasizes the importance of strategic leucine supplementation to align with workout timing and optimize muscle growth potential.

About the author, Michael Rudolph, his extensive background in exercise science, personal training, and research further underscores the significance of leucine consumption. With a Ph.D. in Biochemistry and Molecular Biology, Rudolph's research has shed light on cellular energy mechanisms. His expertise offers valuable insights into optimizing muscle growth while maintaining energy levels and exercise performance.

REFERENCES:

Wolfe R. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? Journal of the International Society of Sports Nutritionvolume 14, Article number: 30 (August 22, 2017) 

Devries M, McGlory C, Bolster D et al. Leucine, Not Total Protein, Content of a Supplement Is the Primary Determinant of Muscle Protein Anabolic Responses in Healthy Older Women, The Journal of Nutrition, Volume 148, Issue 7, July 2018, Pages 1088-1095, https://doi.org/10.1093/jn/nxy091

Yoshimura Y, Bise T, Takatsuk F et al. Effects of a leucine-enriched amino acid supplement on muscle mass, muscle strength, and physical function in post-stroke patients with sarcopenia: A randomized controlled trial. February 2019 Nutrition https://www.sciencedirect.com/science/article/pii/S089990071830594X?via%3Dihub

Szwiega S, Rafii M, Pencharz P et al. The Leucine Requirement for Elderly Men Is More Than Double the Current Recommendations (P01-015-19). Curr Dev Nutr 2019;3(Suppl 1): nzz028.P01-015-19. Published 2019 Jun 13. doi:10.1093/cdn/nzz028.P01-015-19