Indeed, leucine is getting a lot of lip service. And for good reason I will add. For a quick review, remember that researchers have shown that increases in the blood levels of amino acids results in an increase in muscle protein synthesis. Studies a few years later then went on to show that only the essential amino acids were needed to stimulate muscle protein synthesis. The essential amino acids are those amino acids which cannot be produced by the body and as a result they must be received in the diet. Leucine, of course, is one of the essential amino acids.
Next, researchers began exploring how much of the essential amino acids were needed to stimulate muscle protein synthesis and they concluded that a dose of 6 to 12 grams of the essential amino acids were needed. This amount of the essential amino acids is what is provided with a typical 25 gram dose of whey protein isolate or hydrolysate.
Certainly you can get good doses of the essential amino acids with eating any complete protein as well. A complete protein is any source of protein that contains all of the essential amino acids and all animal sources of protein are complete proteins. Milk, egg, dairy, beef, chicken, fish, etc. are all complete protein sources and provide all of the essential amino acids, but a solid whey protein isolate contains the greatest concentrations of these.
A total of nine amino acids are considered to be essential, and to date very little research has been conducted to determine which of these nine essential amino acids are needed in the greatest amounts. Much of this research has focused upon leucine. In particular, leucine is now known to have a critical role at stimulating protein translation (just think protein growth) and is also linked to maintaining a more favorable glycemic and insulinemic response and for this reason is thought to be a critical nutrient for regulation and control over diabetes, obesity, insulin resistance and other unfavorable metabolic problems. Of course, the scope of our discussion, will center upon leucine’s ability to stimulate growth of proteins.
In a highly regulated and complicated series of processes inside muscle cells as well as other tissues, leucine acts a positive regulator of many of these steps. In fact, Dr. Donald Layman, a leading researcher on leucine at the University of Illinois, feels like leucine is by far the most important nutrient to consider when talking about stimulating growth of muscle proteins.
In a recent presentation he indicated that a dosage of 2 to 3 grams of leucine was needed to turn on protein synthetic processes and that this mechanism operated in an all or none fashion. What this means is that a minimum threshold for leucine appears to exists and this value seems to be close to a 2 gram dose. If less than the amount is given, say one gram, the processes aren’t turned on. Also, if a five gram dose is given the same processes are turned on and to the same degree. So the sayings, “some leucine is better than none” and “more is better” need not apply as a dose of 2 to 3 grams appears the necessary amount to trigger or “turn on” protein translation.
Another key discussion Dr. Layman shared was that the stimulating powers of leucine were quite powerful and impacted how long elevations in amino acids could be found. Interestingly, he recommended for people to not take leucine by itself. While this sounds like the opposite of what you might expect, his explanation was equally convincing and impressive. He went on to explain that if leucine was provided without any other amino acids, leucine’s power at starting processes to use amino acids to build proteins would actually decrease overall protein growth. Say what, how is that possible? You just said leucine increased protein growth. It does, no doubt about it, but you must provide the other essential amino acids along with it. If you don’t (if you were to take leucine by itself), it would force the body to breakdown other proteins (oftentimes this protein comes from your existing muscle tissue…not good) to provide the necessary amino acids to result in protein building. You might be thinking this is like borrowing from your neighbor to pay back another neighbor or you are taking one step forward (by taking leucine) but two steps back and this would be a good way of looking at this. Basically, without other amino acids around, leucine results in a negative response. If you add this to the fact that blood levels of amino acids are increased for around 3 hours after ingestion, the timing and composition of the amino acids you provide are very important factors.
Hopefully, if I’ve done my part, you understand a little bit more of the most recent research associated with leucine. Now it’s time to talk about how to apply this information with the food and supplements you should be taking.
In a perfect world, every person would eat a 25 to 30 gram dose of a complete protein source every 3 hours throughout the entire day. Practically speaking and day in and day out this a difficult thing to accomplish. For this reason, the next layer of recommendation would include you ingesting a protein shake of your favorite high quality whey protein isolate during “snack” times throughout the day and do so in a manner where no more than 3 hours would pass each day before another dose of essential amino acids would be provided. Shaker cups and protein powder are oftentimes more convenient and faster than planning several meals each and every day and for this reason they should be considered by almost everyone for their ability to provide a convenient dose of high quality proteins and essential amino acids.
Finally, the latest product to become available which can provide an additional layer of convenience are a quick dose of essential amino acid capsules. The idea behind these are not to provide the complete amount, but rather to provide enough that when added to a small indestructible snack (think apple, granola bar, etc.) will provide the minimum dose of the essential amino acids (particular leucine) to turn on muscle protein synthesis for another few hours until and until your next meal.
In conclusion, leucine appears to be the single-most important nutrient when it comes to turning on the processes which build muscle proteins (i.e., bigger muscles). A necessary single dose of 2 to 3 grams is required to turn on these processes and in combination with enough of the other essential amino acids (so none of them become completely consumed by the processes), will result in an increase in muscle protein synthesis. To be certain the most current research says 2 to 3 grams of leucine and 6 to 12 total grams of all nine essential amino acids is what is needed to turn on the processes. Its important to plan ahead and make sure you are able to regularly provide at least this amount of the amino acids every 2 to 3 hours throughout the entire day. Whether you rely on food sources, protein supplements or cocktails of amino acid caps is up to you as they will all accomplish the task. Regardless, take heed of the fact the leucine is a critical player in the processes of muscle growth and getting enough of it and the other essential amino acids periodically throughout the entire day is a critical first step to maximizing muscle growth and maintaining a lean physique.