Leucine: Muscle Builder Key

September 26, 2016

Leucine: Muscle Builder Key


Reference: Nutrition Express, Journal of Nutrition, The Body Builder, PLOS1

Leucine is a branched-chain amino acid, one of the essential amino acids your body can't make and must have for proper health. The branched-chain amino acids make up some 10% of most meats, but up to 33% of whey protein. Whole proteins is that they take a while to be digested. The branched-chain amino acids are not only critical building blocks for muscle, but they also are the only amino acids that muscle can use for fuel. 

 But leucine does something else. It turns on muscle synthesis. It has been shown to activate the mTOR pathway (mammalian target of rapamycin) which is the protein synthesis switch. The mTOR switch is the Holy Grail of muscle building. Various studies have shown the effects of leucine on mTOR. A study from Columbia University showed that leucine supplements added to weight loss by some 25% in obese rats. 

What is the ideal amount to help you build muscle? That is the subject of much research and debate. Eating the whole food delivers leucine bound up with other amino acids in a whole protein, which takes hours to break down and import into the blood. The leads to lower levels than eating it as a supplement. Whey is about 10% leucine so a 25 gram whey protein supplement will lead to about 2.5 grams of leucine. That appears to be about the right amount to start protein synthesis

But aging animals may need more. And if you want to do a deep dive, you can get into really arcane physiology and learn all about p70S6K and hVps34 proteins. (Looks to me like a great password for my bank. So, it's just this year that much more interest has been spiked in larger doses of leucine. Aging mice can show that they can still build muscle when given 5% of their diet in leucine, and then exercised. They stop losing muscle with age and in fact, build it up. You can too! 

 WWW.What will work for me? This is fascinating. I have an innovative client who shared with me that he is using 20 grams of leucine a day, higher than the 2.5 grams Volek calls for, and can "feel the muscle building". He looks great. When I look in the mirror, I think, "Maybe I should try some leucine." It helps lose weight and it builds muscle. What's so bad about that.   

Pop Quiz

1. Leucine is a BCAA. What does that stand for?                        Answer:  One of the three "branched chain" amino acids, but the only one that stimulates mTOR. ‪

2. What is mTOR?                        Answer:  The protein switch that turns on muscle building. Stands for the mammalian target of rapamycin. ‪

3. Leucine is a major part of whey protein. T or F?          Answer:   Yup. That's its best source. ‪

4. I may benefit from doses as high as 20 grams a day as an aging human. T or F?                   Answer:  If muscle building and weight loss are on your agenda, this may be a great supplement. ‪

5. What's p70S6K?                        Answer:   One of the other proteins that appears to be stimulated by leucine. It's not my bank password. But it looks promising as my fat burning password.