BCAAs and Muscle Growth

BCAAs and Muscle Growth

Branch Chain Amino Acids – The Foreman for your Muscles

There is probably not a more talked about supplement in the gyms these days than Branch Chain Amino Acids (BCAAs). It seems to be in everyone's drink while smashing out squats and benching 100kg. BCAAs come in all flavours and colours, so the drink can be matched to your outfit. And despite BCAAs being amino acids, they all seem to taste sweet and delicious. Strange that, considering amino acids are essentially simply parts of a protein. And if these humble BCAAs are just 'parts of a protein', then why is everyone drinking them? What makes them so popular? And most importantly, do they do any good? And do they fulfill the claims of muscle growth and the more subjective 'just makes me feels good' claim? Let's have a look at the claims of muscle growth and mental health.

What are BCAAs?

There are 9 essential amino acids. Of these 9 amino acids, 3 of them are the branch chained amino acids, namely Leucine, Isoleucine, and Valine. There are different ratios in supplements, but the most common ratio is 2:1:1, where the Leucine occupies the '2' spot. Leucine is the chief driver of the natural growth chemical mTORC1 [1] (more about this special chemical later). Isoleucine is a great amino acid for lowering blood sugar. It achieves this feat by stimulating the uptake of glucose into cells[2]. This alone helps with the growth of tissues. Valine is the amino acid that competes with tryptophan’s uptake into the brain[3]. We will discuss how this helps you with your exercise goals later.

It is all in Your Head?

The claim that BCAAs simply make you feel better and thus improve your workouts is worth considering and the science seems to support this. Firstly, a recent study [4] found that there is a strong inverse association between the amount of BCAAs ingested and the incidence of mental health conditions such as anxiety and depression. What this means in English is that if you ingested more BCAAs, you suffered fewer mental health disorders, such as anxiety and depression. This doesn't necessarily mean that the BCAAs are the things that cure depression, but it certainly lends support that BCAAs do something to help your brain.

Serotonin and BCAAs

Most of us know that serotonin is a cool chemical that resides in the brain and makes us happy and relaxed. And sure, serotonin does lots of cool things but that is essentially it. So, it may surprise you to know that consuming BCAAs increases their concentration in blood. This leads to a reduction of tryptophan by the brain and also serotonin synthesis and thereby delay fatigue, meaning you can work out harder for longer[5].

Go longer

A recent 2020 study tested the hypothesis that ingesting BCAAs before you exercise can help you work out longer and harder, which could be one way that BCAAs help you build muscle mass. Usually, the harder you work out and the more exercise you do, you will have associated muscle gains. In this study, they took 16 runners and gave them either 20g of BCAAs or a placebo and what they found was that oral intake of 20 g of BCAAs 1 hour before a treadmill exercise session increased time to exhaustion, probably due to the reduction in serotonin concentration in the brain[6].

BCAAs Boost Muscle Growth

There is a cool chemical in the body that is on the wish list for every gym-goer. This chemical is named mammalian target of rapamycin complex 1 (or mTORC1 to its friends) and boosts muscle growth. Thus, elevating this chemical is an excellent way to grow your guns! You can boost mTORC1 by simply drinking a pretty pink drink, as long as it contains BCAAs. There was a landmark paperback in 2006 [7] that described the signaling pathway of mTORC1. It described how leucine, one of the BCAAs boosts mTORC1, which leads to an increase in muscle mass.

After exercise

So, BCAAs are pretty cool supplements for helping us feel better, maybe reduce anxiety, and of course, help us run longer and grow our muscle, but what if you took it after your workout? The good news is that this question was posed about 20 years ago. They have given BCAAs to subjects after their workout and monitored them for changes in their muscles. What the researchers found was that BCAAs have a protein-sparing effect during the recovery post-exercise or either that protein synthesis has been stimulated and/or protein degradation was decreased[8].

How about the Essential Amino Acids (EAAs)?

As the name would suggest, EAAs are essential for the body to consume. There are 11 essential amino acids and of the essential amino acids[9], 3 of them are the before mentioned branch chained amino acids. The other 8 amino acids need to be consumed by humans to maintain a positive nitrogen balance in the body. So, people ask if they can be consumed together and of course the answer is yes. And in fact, it is vastly more beneficial to take all of these EAAs together as a supplement, preferably after or before exercise to maximise muscle growth.

The Take Home Message

All essential amino acids are just that…essential. Our body can’t make them so they need to be consumed in the diet. Supplementing with an EAAs supplement makes sense over taking a BCAA supplement because EAAs already contain the BCAAs. Thus, you get all of the benefits of supplementing with an EAAs supplement and miss out on nothing!


  1. J Nutr. 2001 Mar;131(3):861S-865S. doi: 10.1093/jn/131.3.861S. Role of leucine in the regulation of mTOR by amino acids: revelations from structure-activity studies. C J Lynch 1
  2. Biochem Biophys Res Commun. 2003 Dec 26;312(4):1111-7. doi: 10.1016/j.bbrc.2003.11.039. Isoleucine, a potent plasma glucose-lowering amino acid, stimulates glucose uptake in C2C12 myotubes. Masako Doi 1, Ippei Yamaoka, Tetsuya Fukunaga, Mitsuo Nakayama
  3. Int J Sports Med. 2001 Jul;22(5):317-22. doi: 10.1055/s-2001-15645. Evidence that the branched-chain amino acid L-valine prevents the exercise-induced release of 5-HT in rat hippocampus. D Gomez-Merino 1, F Béquet, M Berthelot, S Riverain, M Chennaoui, C Y Guezennec
  4. Nutr J. 2021 Jan 29;20(1):11. doi: 10.1186/s12937-021-00670-z. Dietary intake of branched-chain amino acids concerning depression, anxiety, and psychological distress. Glareh Koochakpoor # 1, Asma Salari-Moghaddam # 2, Ammar Hassanzadeh Keshteli 3 4, Hamid Afshar 5, Ahmad Esmaillzadeh 6 7 8, Peyman Adibi 4
  5. J Nutr. 2006 Feb;136(2):544S-547S. doi: 10.1093/jn/136.2.544S. A role for branched-chain amino acids in reducing central fatigue. Eva Blomstrand
  6. J Hum Kinet. 2020 Mar; 72: 69–78. Published online 2020 Mar 31. doi: 10.2478/hukin-2019-0099Effects of Oral Branched‐Chain Amino Acids (BCAAs) Intake on Muscular and Central Fatigue During an Incremental Exercise. Mohammad Fayiz AbuMoh’d,*,1 Laila Matalqah,2 and Zainalabidden Al-Abdulla3
  7. J Nutr. 2006 Jan;136(1 Suppl):227S-31S. doi: 10.1093/jn/136.1.227S. Signaling pathways and molecular mechanisms through which branched-chain amino acids mediate translational control of protein synthesis. Scot R Kimball 1, Leonard S Jefferson
  8. Am J Physiol Endocrinol Metab. 2001 Aug;281(2):E365-74. doi: 10.1152/ajpendo.2001.281.2.E365. BCAA intake affects protein metabolism in muscle after but not during exercise in humans. E Blomstrand 1, B Saltin
  9. Hou Y, Wu G. Nutritionally Essential Amino Acids. Adv Nutr. 2018;9(6):849-851. doi:10.1093/advances/nmy054