Leucine is the most important amino acid for supporting muscle growth, with research suggesting that suboptimal leucine can limit protein synthesis rates. While the amount of leucine in any particular food is less important thanks to the whole food matrix and interplay of nutrients having synergistic effects in whole food protein, research suggests it should be a key consideration when consuming isolated proteins – like protein powdered. If we want to dive into one large systematic review evaluating the role of leucine for muscle protein synthesis, critics will argue that the results are mixed. While the majority of the studies (9 out of 16) did find a significant benefit to leucine for muscle protein synthesis, 7 out of 16 studies did not. And this is where a critical appraisal of literature like this is key, especially when looking at it from a standpoint of what is important to us at neue theory, which is optimal dosing. Looking at the 9 positive results, the low doses of leucine given were almost all 2 grams or less. And the high doses were all around 2.5 grams or above. In the 7 studies that did not find an effect, many either had a very small difference in leucine contents between groups or they were comparing leucine intakes that were both above 2 grams. In other words, they compared doses that were arguably already sufficient so it makes total sense that they didn't see an effect from a dosing standpoint.
At this point, we don't have a specific dose response study but when we look at the body of research to date, we can make strong inferences. For example, we can look to the research on the optimal leucine range for muscle protein synthesis in whey protein, which is often considered one of the, if not the most efficient isolated protein. In contrast, leucine is often one of the most commonly lacking amino acids in plants, with some fully pea protein powders only supplying 1.2 grams of leucine- that is less than half of what we offer in neue theory’s Plant-Based Probiotic Protein Powder. We can also look to the recommendations of world renowned protein researchers, Dr. Stewart Phillips and Dr Donald Layman, who also call out the importance of leucine in protein supplements and Dr. Layman even points out the specific 2.5 grams goal.To summarize, fortifying a plant protein with free leucine is a totally viable, tried and tested strategy for supporting optimal muscle protein synthesis, which is exactly why we opted to top up our leucine in our Plant-Based Probiotic Protein Powder.