Serious bodybuilders want an edge when it comes to building muscle. Some turn to supplements in hopes of making greater gains in a shorter period of time. One of the most popular of these supplements is branched-chain amino acids, also known as BCAAs. People who take BCAAs, usually in the form of a powder they add to a drink, usually take this supplement before or after a workout for several reasons, the most common of which is to build more muscle. We know that amino acids are essential for building new muscle tissue, so it would seem logical that taking them in supplemental form would be beneficial. Yet, science doesn’t necessarily support this. Are you really getting benefits when you take branched-chain amino acid supplements?
What Are BCAAs?
Branched-chain amino acids are a group of three amino acids, valine, isoleucine, and leucine. As you know amino acids are the building blocks of protein. Amino acids form bonds with one another to build the protein structure that makes up a muscle. This happens under the direction of a variety of factors, including hormones and signaling proteins.
You can divide amino acids into two general classes: non-essential and essential. Non-essential amino acids are ones your body can make. As such, you don’t need to get them in dietary form. When there’s a shortfall, you make more. In contrast, your body can’t make essential amino acids, so you must get them through diet. BCAAs fall into the latter category – you have to get them through diet. However, they aren’t the only essential amino acids. In total, there are 9 essential amino acids that you have to get through diet and 11 that your body can make. If there’s a shortfall of one or more essential amino acids, your body will try to get that amino acid from any source that it can, including muscle tissue.
The Role Branched-Chain Amino Acid SupplementsPlay in Muscle Protein Synthesis
There’s little doubt that the branched-chain amino acids, particularly leucine, play a key role in building new muscle proteins. Along with being incorporated into new muscle tissue, studies show that leucine acts as a signaling molecule to turn on muscle protein synthesis. It does this by activating a critical anabolic pathway called the mTOR pathway. When there are enough amino acids around, the mTOR pathway jumpstarts the synthesis of new muscle proteins, especially after a resistance workout. Of the three branched-chain amino acids, it’s leucine that has the greatest impact on the mTOR pathway. It makes sense that if you’re trying to build new muscle, you need enough leucine in your diet.
Why You Don’t Need Supplemental Branched-Chain Amino Acid Supplements
As popular as branched-chain amino acid supplements are, a recent study points out why you don’t need them in supplemental form and that taking them in isolation may actually be detrimental. This research showed that taking branched-chain amino acids in isolation would not lead to a net increase in muscle protein synthesis. The reason? To build new proteins, your body needs all 9 essential amino acids. If one or more of these building blocks is missing, muscle protein synthesis can’t move forward. It’s like trying to put a puzzle together with pieces being missing or unavailable. When you take a dose of branched-chain amino acids, you’re supplying 3 of the essential amino acids. To get the rest, your body breaks down existing muscle protein and release the essential amino acids that are in short supply.
Based on this, it’s not hard to see why taking branched-chain amino acids in isolation won’t get you very far. You need all of the necessary amino acids and BCAAs are only supply 3 of them. Your muscles are forced to get those amino acids from the breakdown of existing muscle tissue. So, there isn’t a net increase in muscle protein synthesis. Some studies actually correlated isolated BCAAs with a decrease in muscle protein synthesis as the “missing” amino acids have to come from the breakdown of muscle tissue.
What about Leucine?
As mentioned, leucine is an anabolic signal for muscle growth. So, getting enough of it is important. Wouldn’t branched-chain amino acids be beneficial because they supply leucine? As it turns out, the other two BCAAs, valine, and isoleucine, may actually reduce the impact of leucine on muscle protein synthesis. Valine, isoleucine, and leucine all enter the muscle cell on the same transporters. With valine and isoleucine competing with leucine for the same transporter, it reduces the amount of leucine that gets into the muscle cell.
So, what IS the best way to get leucine? If you consume enough dietary protein from natural sources, you should get enough of this necessary amino acid to activate muscle protein synthesis without taking supplements. Leucine is most abundant in animal foods, including beef, chicken, and eggs, as well as dairy, but soy and legumes also contain respectable quantities of leucine. If you get enough total protein in your diet, you’ll also get leucine. One exception might be a strictly plant-based diet. You’d have to eat more plant-based protein to maximize the anabolic effect of leucine. If you consume dairy, whey protein is an excellent source of leucine. There’s also evidence that older people aren’t as responsive to leucine and need higher amounts to maximize muscle protein synthesis. However, a younger person who eats a varied diet that includes animal protein should get enough leucine, assuming they consume enough protein.
Do Branched-Chain Amino Acid Supplements Have Other Benefits?
Some studies suggest that branched-chain amino acid supplements may reduce post-exercise muscle soreness, known as DOMs while other studies fail to show a substantial benefit. A study published in the Journal of the International Society of Sports Nutrition found that BCAAs didn’t reduce markers of muscle damage or prevent decrements of muscle function after a resistance workout.
The Bottom Line
There’s no strong evidence that branched-chain amino acids will give you a muscle-building edge and it won’t necessarily reduce post-workout soreness either. You need all the essential amino acids and if your muscle cells can’t find them, they’ll get them from breaking down muscle tissue. Focus on getting your amino acids from whole food sources and make sure you’re consuming enough total protein.
References:
Wolfe Journal of the International Society of Sports Nutrition (2017) 14:30. DOI 10.1186/s12970-017-0184-9.
J Anim Sci. 2011 Jul; 89(7): 2004–2016. Published online 2010 Oct 8. doi: 10.2527/jas.2010-3400.
Am J Physiol Endocrinol Metab. 2006;291(2):E381-387.
Int J Sport Nutr Exerc Metab. 2010 Jun;20(3):236-44.
Journal of the International Society of Sports Nutrition201613:30 https://doi.org/10.1186/s12970-016-0142-y.
Journal of the International Society of Sports Nutrition 201613:30 https://doi.org/10.1186/s12970-016-0142-y
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