Branched-chain amino acids (BCAAs) are a popular sports supplement with bodybuilders and athletes. But you don’t need to look for them in a bottle as our diet naturally contains them as part of the amino acid building blocks of protein. With claims of increased muscle protein synthesis, decreased muscle protein breakdown, enhanced endurance and less muscle soreness, they seem to be an essential supplement that no athlete can do without. In this podcast episode, I’ll look at those claims and explore the evidence. TL;DR – save your money on BCAA supplements and just eat a variety of high-protein foods which is what athletes pretty much do already.
So, what exactly are BCAAs? BCAAs are three chemically distinct essential amino acids: leucine, isoleucine and valine. Being essential amino acids means we need them in our diet for effective protein synthesis as our body can’t make enough of them. But the fact they’re essential isn’t really that big of a deal or a unique selling point as there are 9 essential amino acids we need in our diet. And we get all of them from a varied diet with different protein sources.
The interest in the three particular BCAAs is because they’re considered the most anabolic. So not only can BCAAs provide building blocks for making new protein, but they also could have an additional protein stimulating role. This makes gym bros happy. And supplement manufacturers wealthy.
BCAAs are metabolised mostly within the skeletal muscle. They play an important role in both cellular energy homeostasis and in the regulation of muscle protein synthesis. And there is evidence that BCAAs can stimulate muscle protein synthesis and inhibit protein breakdown – at least from cell culture and animal studies. And that’s because BCAAs, in particular leucine, can stimulate a key muscle protein synthesis signalling pathway called mTOR.
But when you get to the human research, and by that I mean the more young and gym focussed subjects as well as athletes, and look for clear evidence of the muscle gainz, the evidence is best described as weak.
Just why you don’t seem to see much of a benefit of BCAAs for muscle growth in healthy people, despite what all that glossy supplement company literature may tell you, comes down to one simple fact. Taking BCAAs alone with little other protein will do zero for muscle growth – you need a full complement of protein including all 9 essential amino acids on top of an adequate ‘dose’ which could be getting up to 1.6 grams per kilogram of body weight and above for some athletes. So, you still need to supplement BCAAs on top of regular food. And keep in mind that regular food already contains BCAAs with meat and dairy being some of the highest sources.
At best, it seems that the key BCAA, that being leucine, could be used as an isolated supplement to enhance the anabolic potential of certain meals that may not, on their own, maximise muscle protein synthesis. So, if the diet or a specific meal had mostly lower-quality protein sources in it, then there may be a benefit to supplementing that meal with leucine up to a total of 3 grams. It should be noted that the ‘benefit’ in this instance is purely for muscle protein synthesis as there isn’t much firm evidence that this would then translate into more practical longer-term muscle growth, strength, or recovery.
The broader protein supplement research field shows that even studies that use lower-quality protein such as that derived from wheat can elicit a significant muscle protein synthesis response if greater amounts of it are consumed and this may be an effective strategy to compensate for its lower protein quality. So, the story here is that adequate protein overall in the diet may trump the source of protein, and the need for BCAA supplements, so long as the diet is varied. And an overall adequate amount of high-quality protein would mostly trump the benefits that taking an additional commercial BCAA supplement could provide. It is likely then that BCAA supplements are just an expensive source of amino acid building blocks.
Outside of muscle protein synthesis, BCAA supplements are also promoted as an agent to enhance endurance and improve recovery following muscle damage. There is some evidence for these claims, but much of the BCAA research around endurance performance and fatigue has poor quality research designs. There is evidence for BCAA supplementation reducing the severity of delayed onset muscle soreness following damaging exercise, but the benefit here appears to be marginal. Also, the placebo used in most studies didn’t contain any protein so it remains to be seen if BCAA supplementation would be better or worse than whole protein foods, which also contain BCAAs.
If you want a nice summary document of all the research I’ve covered here, then the AIS nutrition team has a great fact sheet on BCAAs as part of their supplement evaluation framework. And I’ll link to this document in the show notes. https://www.ais.gov.au/__data/assets/pdf_file/0013/1000417/36182_Supplements-fact-sheets_BCAA-v4.pdf
Now in this podcast, my focus has been on healthy people who are more interested in growing muscle mass for their sport. There is though some clinical research looking at the specialist use of BCAA supplements in people with liver cirrhosis. Why BCAAs may be of benefit here is because they have a unique characteristic in that they can be metabolised in the skeletal muscle rather than in the liver. And there is evidence they can help improve clinical outcomes such as reducing the incidence of hepatic encephalopathy, which is the loss of brain function that occurs when the liver is unable to remove toxins from the blood.
And BCAAs could also have a role as a supplement for use by people with disease- or age-related muscle wasting which we call sarcopenia. In one theory of ageing, a higher amount of BCAAs, in particular leucine, is needed to fully switch on the protein synthesis signalling cascade. So, there is still a plausible use story for these supplements, but here, we’re talking about disease states that are also compounded by higher protein needs in the face of likely malnutrition.
So, let’s wrap all this up. Based on the available evidence, there is not a strong case to recommend BCAA supplements for enhancing muscle growth or reducing muscle damage in the healthy adult population. While evidence does exist to support the claims of BCAAs, the benefit appears less than actually eating foods containing high biological value protein, and in sufficient quantities, in the first place. My view: don’t waste your money on BCAAs if you don’t have the cornerstones of a good varied diet, adequate protein to meet your requirements and some hard training in place first – that’s where almost all of the gains come from.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.