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Leucine or BCAA's

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Leucine or BCAA's

Leucine or BCAAs

One question I get asked a lot is whether it's best to take all three branched-chain amino acids (BCAAs - which include leucine, isoleucine and valine) or just leucine alone by itself.

My answer to that question is that you are better off taking all three of these BCAAs together. And there are numerous reasons why I feel this way. Of the nine essential aminos that are needed by your body for building muscle, the BCAAs are hands down the most important three.

Any others?

While most other amino acids are metabolized in the liver, the BCAAs are some of the few that are metabolized directly in muscle. BCAAs can therefore serve as an important source of energy during workouts. And this especially true when following a low carb diet. The BCAAs also reduce fatigue during workouts, and not just because they are used for energy. They actually trick your brain to help stave off fatigue when you are training hard, so you can train harder for longer. How do they do this trick? Well it all comes down to valine. This BCAA actually prevents tryptophan from being taking up by the brain. Since tryptophan gets broken down into 5-hydroxytryptamine (serotonin), which is a chemical that signals fatigue in the brain and causes you to slow down and get weaker, preventing tryptophan uptake prevents your body from sensing fatigue and slowing you down.

When it comes to muscle growth, leucine is definitely the MVP.

This is because leucine has been shown to interact directly with insulin to stimulate protein synthesis. While isoleucine and valine also play a role in protein synthesis, their effect is generally smaller. This is why many believe that all you need is to take leucine around workouts. While studies have shown that both leucine by itself or in combination with the other BCAAs can stimulate muscle growth, no previous studies have directly compared their effect when taken in supplemental form, Until now.

As Always Science Proves it

Scientists from Baylor University compared the effects of BCAAs against leucine. They gave men either just leucine, all three BCAAs, or a placebo before workouts and immediately after workouts. They reported in a 2008 issue of the Journal of the International Society of Sports Nutrition that although leucine increased muscle protein synthesis (the process that results in muscle growth) after the workout significantly better that the placebo, BCAAs increased muscle protein synthesis significantly better than the placebo AND leucine by itself.


P. La Bounty et al., The effects of oral BCAAs and leucine supplementation combined with an acute lower-body resistance exercise on mTOR and 4E-BP1 activation in humans: preliminary findings. Journal of the International Society of Sports Nutrition, 5(Suppl 1):P21, 2008.

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