Protein High in Leucine Better For Resistance Training

27 Oct 2016 --- Protein supplements high in leucine are key to muscle building success after resistance training, according to Tier 1 Canada Research Chair in Skeletal Muscle Health, Dr. Stuart M. Phillips of MacMaster University.

His study, published in Nutrition and Metabolism, reviewed the current science to examine the effects of the quality of supplemental protein on changes in muscle mass, strength and body composition when combined with strength training.

His inquiry suggests that based on the new proposed method to evaluate protein quality using its indispensable (or essential) amino acid composition and its digestibility, protein sources that provide leucine (an essential amino acid) such as whey protein, are the strongest determinant of muscle protein synthesis and likely muscle growth.

“My assessment of the data on protein supplementation and resistance exercise reveals that the amount of leucine in a protein supplement has the greatest impact on muscle protein synthesis,” said, Dr. Phillips.

“Leucine is not only a building block for protein, but a trigger for working muscles to synthesize more protein.”

“In essence, it turns on muscle protein synthesis like a light switch so that over time, there could be greater gains in lean body mass and strength, and subsequently, body composition improvements.”

Proteins with the greatest content of leucine include whey protein isolate or concentrate. Whey protein is a milk protein that is considered high-quality due to its amino acid profile and high score for digestibility.

Based on the culmination of data inspecting protein types and muscle protein synthesis, whey protein rated higher than other protein sources such as soy, pea or rice.

However, previous research published in the Journal of the International Society of Sports Nutrition in 2015, suggests that there is no difference between vegetable pea proteins and whey-based dietary products when it comes to promoting a greater increase of muscle thickness, suggesting vegetable pea proteins could be used as an alternative to Whey-based dietary products. Furthermore, as whey protein is animal derived, vegetable pea proteins are popular options for vegetarians and vegans.

Discussing the result of his study, Dr. Phillips notes, “The outcome of this review isn't just applicable to strength trainers. As we age, muscle loss becomes prevalent if we don't thwart the decline.” 

“Leucine-rich whey protein supplementation, combined with resistance exercise, may be one way to help preserve muscle mass throughout the lifespan.” 

More research is needed to further characterize proteins based on their quality, digestibility, and amino acid profile, as well as to identify their impact on the aging population.