Leucine being an essential amino acid cannot by synthesized by humans. New research is focusing heavily on leucine supplementation both to enhance muscle hypertrophy and to prevent muscle loss during weight loss.
Leucine does not only play a role as substrate for protein synthesis, but also as a signal nutrient that regulates protein metabolism. However, studies have found that leucine-rich amino acid mixtures are more effective than leucine alone in improving muscle mass and performance. This suggests that the efficacy or effectiveness of leucine depends on other amino acids (Balage et al, 2010).
Researchers at McMaster University have recently suggested (Little et al, 2010) the following:
“Based on results from acute and chronic studies in humans in a wide variety of wasting conditions, we propose that resistance exercise training combined with appropriately timed protein (likely leucine-rich) ingestion represents a highly effective means to promote muscle hypertrophy, and may represent a highly effective treatment strategy to counteract the muscle wasting associated with aging and chronic disease.”
Researchers at the University of Chicago have also suggested (Devkota et al, 2010):
“Leucine consumed at 2.5 g triggers a postmeal anabolic response that protects metabolic active tissues during weight loss and increases loss of body fat. SUMMARY: Balanced daily distribution of protein with increased intake at breakfast and lunch protects metabolically active tissues including skeletal muscle during weight loss.”
Key points made by Devota et al (2010):
“A growing body of research reveals that dietary intakes of protein above the minimum requirement designated as the recommended dietary allowance (RDA) are beneficial in treatment of diseases including obesity, metabolic syndrome, and type 2 diabetes.
We proposed that the beneficial effects of a higher-protein diet originate with the unique roles of the essential amino acid leucine in stimulating muscle protein synthesis, increasing diet-induced thermogenesis, enhancing satiety, and stabilizing glycemic regulations.”
Devota et al (2010) proposes that a minimum of a 2-3 times increase in plasma leucine is required to stimulate protein synthesis. To achive this effect, they suggest that humans need to consume a minimum of 25-30 g of protein containing a minimum of 2.5 g of leucine per meal. Different protein sources have varying percentages of leucine content by weight. The authors note that milk protein has 10% leucine content by weight while wheat proteins only have 6.8%. As such, they note that the quality of protein source for achieving this result is determined by the leucine content.
Bottom line: The importance of supplementation or consuming the essential amino acid, Leucine, appears to be attracting more attention from researchers with respect to its role in promoting protein synthesis and preventing muscle wasting during weight loss.
references:
Balage M, Dardevet D.Long-term effects of leucine supplementation on body composition.Curr Opin Clin Nutr Metab Care. 2010 May;13(3):265-70.
Little JP, Phillips SM. Resistance exercise and nutrition to counteract muscle wasting. Appl Physiol Nutr Metab. 2009 Oct;34(5):817-28.
Devkota S, Layman DK. Protein metabolic roles in treatment of obesity. Curr Opin Clin Nutr Metab Care. 2010 Jul;13(4):403-7.
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