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Leucine Supplements
Does Protein + Leucine = Bigger Muscles?


Leucine is one of the hot new things currently promoted by supplement companies. It's being added to drinks, powders and pills with the vague promise you'll grow more muscle if you take it. Before you put your money down, you might want to take a closer look at this "miracle" ingredient.

Let's start with a little background. Leucine is an essential amino acid. You've probably heard that phrase before, here's what it means. There are at least 8 amino acids that our bodies have to get from outside sources. They're called "essential" because we can't make them and we can't live without them.

Protein is made up of amino acids. Our bodies need protein and the amino acids it's made from to build muscle and survive.

That means whenever we eat foods with all the essential amino acids in them, we're getting a little leucine. We also get some leucine in any protein supplement that says it includes, "all the essential amino acids."

What's different is how the supplement companies are promoting it. Many are now claiming that by adding extra leucine to their protein mixes, it makes them more effective muscle builders. Unfortunately the marketing doesn't match up with the research.

To make sure I'm not being lied to, I insist every supplement I take is subjected to a double-blind clinical trial. (It's part of my Four Point Reality Check.) I want to see half the group taking the "treatment" and the other half a placebo. When I read the leucine studies, there was a significant problem.

The studies being promoted by supplement companies usually had two groups of people. One took a protein supplement with leucine, the other didn't take anything at all. At the end of the study, the group taking leucine and protein saw greater muscle growth.

Unfortunately those studies don't tell me anything about leucine. You see, there are hundreds of studies through the years that show taking protein after a workout will stimulate muscle growth. It's an established fact. If you compare one group of people who take nothing, to another group that takes protein and leucine, the people who take the protein are always going to do better.


What I needed are studies where there were two groups of people. One that got protein only, and the other that got protein with leucine. Over the last few years a couple of them have taken place. Here's what they found.

A University of Texas study done in 2009 declared that, "whey protein plus leucine in healthy young volunteers results in an anabolic response in muscle that is NOT GREATER [emphasis ours] than the previously reported response to whey protein alone."

Whey protein - good, whey protein with leucine - no added benefit.

Maastricht University in the Netherlands did a similar study in 2008 and they concluded that, "Co-ingestion of leucine with carbohydrate and protein following physical activity does not further elevate muscle protein fractional synthetic rate in elderly men when ample protein is ingested."

They discovered the same thing the University of Texas did. Protein alone is good. Protein with added leucine provides no additional benefit. If you're spending more for the combo, you're wasting your money.

Having said that, there are at least three situations where clinical trials suggest added leucine may be of benefit.

  • If you're over the age of 65 and don't workout,
  • are just beginning to workout or
  • are experiencing muscle wasting.

Each of those conditions show a very slight improvement in muscle growth for the people taking protein with added leucine versus standard whey protein alone.

For those of you without a serious medical condition, who workout two or more times a week and are under the age of 65, don't bother spending the extra for additional leucine in your protein. Save that money for a gym membership, exercise equipment, personal training sessions or to buy healthier foods. Those are all healthy investments that will yield much higher returns.

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