Lots of gymgoers take branched-chain amino acids (BCAAs) to help build muscle. Runners and athletes of various other sports may also take BCAAs as a way of building muscle and preventing muscle loss. BCAAs are a set of three amino acids: leucine, isoleucine and valine.

As popular as BCAA shakes are, I highly doubt they are effective for building muscle and you could do yourself a favour by either saving the money or spending it on a complete protein supplement such as whey protein or spending it on real food like chicken breast, eggs, beef, nutritious vegetables, and fruit.

Why BCAAs Are Ineffective For Building Muscle

Supplements are a big market, particularly BCAAs. We are sold this idea that BCAAs will promote muscle protein synthesis, prevent muscle loss and help us to attain an anabolic (muscle building) state, but there is little evidence to back up these claims and suggest this is true other than it seems logical.

BCAAs Don’t Provide All The Amino Acids For Muscle

BCAAs provide three out of the nine essential amino acids humans must consume from dietary sources. Your body is able to synthesise eleven non-essential amino acids, giving us around twenty amino acids the body uses in total. These amino acids are used to build skin, enzymes, hormones, bone and more structures within the body.

Here’s the problem with supplementing with BCAAs for building muscle. The body requires all nine essential amino acids to build muscle – BCAAs only give us three of the nine amino acids. Muscle protein synthesis will be limited by the availability of any one of the nine essential amino acids. This means that the addition of dietary BCAAs alone into the diet will be unable to help promote muscle protein synthesis. If one of the eleven non-essential amino acids is missing, the body is able to synthesise it.

Of course, if you somehow happen to be lacking the amino acids valine, leucine and isoleucine, then BCAAs will enhance muscle protein synthesis but this is highly unlikely as many foods you consume will contain BCAAs.

As of currently writing this article (May 2019), there have been no studies which have shown that supplementing BCAAs in powder or pill form increase muscle protein synthesis.

BCAAs Aren’t Effective At Preventing Muscle Loss Either

Two intravenous studies (no human studies) showed that taking BCAAs decreased protein synthesis. BCAAs turned into fuel in the body, so they may provide you with some extra energy whilst exercising which could potentially improve performance.

Amino Acids In Muscle Protein Breakdown Are Recycled

70% of the muscle loss that occurs is actually recycled. This means that when your muscle protein is broken down into amino acids, 70% of these amino acids are recycled and reused to build that muscle back up again. Fasting is thought to increase the percentage of amino acids recycled from muscle protein breakdown by promoting autophagy, the process of recycling cells within the body.


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