by Jeff S. Volek, Ph.D., R.D.
Cutting edge research over the last few years has revealed the unique benefits of leucine, one of the essential amino acids, as an anabolic agent in muscle growth. Thus, many supplement makers add additional leucine to their protein powders to boost its muscle building potential.
One of the reasons whey protein is popular and effective is due to its naturally high leucine content (about 10%). Some whey products contain additional leucine beyond what’s naturally there, but can you get too much of a good thing?
One recent experiment tested the effects on muscle anabolism in young men and women who ingested 16.6g of whey protein plus an additional 3.4g of leucine immediately before a workout. Compared to the placebo trial, pre-exercise ingestion of whey plus leucine resulted in a large increase in muscle protein synthesis. The response, however, was similar to the ingestion of 20g of whey protein reported in their previous study described above. Thus, 20g of whey appears to be adequate to stimulate an anabolic effect in muscle with no further benefit of additional leucine.