From the Guidelines
Leucine is a crucial essential amino acid that plays a significant role in protein synthesis and muscle growth, and its supplementation has been shown to improve muscle protein synthesis, particularly in patients with cancer and critically ill patients, as evidenced by recent studies 1.
Importance of Leucine
Leucine belongs to the branched-chain amino acids (BCAAs) group and cannot be produced by the body, requiring consumption through diet or supplements. It stimulates muscle protein synthesis through activation of the mTOR pathway, making it valuable for athletes and those looking to maintain or increase muscle mass.
Recommended Intake and Sources
The recommended daily intake for adults is approximately 39 mg per kg of body weight, with higher amounts often used by athletes (5-10 grams daily) 1. Good dietary sources include chicken, beef, fish, eggs, dairy products, soybeans, and whey protein. Leucine supplements are typically taken in doses of 2-5 grams, often before or after exercise for maximum benefit.
Clinical Significance
Recent studies have shown that leucine supplementation may improve muscle mass in sarcopenic, elderly persons 1, and its potential benefits in cancer patients and critically ill patients are being explored 1. However, more research is needed to confirm its roles in these populations.
Key Points
- Leucine is an essential amino acid that stimulates muscle protein synthesis
- Recommended daily intake is approximately 39 mg per kg of body weight
- Good dietary sources include chicken, beef, fish, eggs, dairy products, soybeans, and whey protein
- Leucine supplements are typically taken in doses of 2-5 grams, often before or after exercise
- Potential benefits in cancer patients and critically ill patients are being explored 1
From the Research
Significance of Leucine
- Leucine is an essential amino acid that plays a crucial role in protein synthesis and muscle growth 2, 3, 4, 5, 6
- It is a key regulator of skeletal muscle protein synthesis, activating the mTOR pathway and other proteins involved in this process 5, 6
- Leucine supplementation has been shown to enhance myofibrillar protein synthesis (MPS) at rest and after exercise, particularly when combined with other essential amino acids 4, 5, 6
Effects on Muscle Growth and Recovery
- Leucine-enriched essential amino acids (LEAAs) have been found to moderately attenuate muscle damage and improve recovery from post-exercise muscle damage, independent of increases in integrated myofibrillar protein synthesis 4
- Leucine supplementation has been suggested to develop muscle mass or prevent protein loss in several conditions characterized by muscle protein wasting, although long-term dietary leucine supplementation has been poorly investigated 3
- A low-protein mixed macronutrient beverage can be as effective as a high-protein dose at stimulating increased MPS rates when supplemented with a high amount of leucine 5
Optimal Dosage and Timing
- The optimal dosage and timing of leucine supplementation are still unclear, with varying doses and timing used in different studies 2, 3, 4, 5, 6
- A daily intake of 45 mg/kg bodyweight/day of leucine has been suggested as a minimum for sedentary individuals, with more required for those participating in intensive training 2
- Leucine supplementation before or during endurance exercise may prevent or decrease the net rate of protein degradation and improve mental and physical performance 2