Bold Claims and Assertions

Do BCAAs do what we’re led to believe, or is the marketing spiel just a load of bold claims and assertions with flaky research behind them? BCAAs seem to be the current ‘supplement-de-jour’. Social media is full of ‘roided’ up fitness models clutching tubs of BCAA powder and pills attributing their amazing physiques to the supplement (which they of course happen to sell). So, are they worth the hype?

BCAA pic


First of all, what are BCAAs?

BCAA stands for Branched Chain Amino Acid. Amino acids are the building blocks of proteins. When you consume protein rich foods such as chicken, tuna or eggs, the protein is digested and broken down into amino acids. The amino acids are then reassembled into new proteins; muscle and connective tissue, enzymes or hormones for example. There are 21 amino acids in total, 12 of which your body can synthesize for itself and are thus referred to as non essential amino acids. The other 9 aminos are known as essential amino acids as they cannot be synthesised within the body and therefore need to be provided through the diet. Three of these essential amino acids; leucine, isoleucine and valine are collectively known as the branched chain amino acids, or BCAAs.

Leucine is potentially the most famous amino acid due to its role in triggering muscle protein synthesis. Via a molecular signalling pathway known as the mTor pathway, the ingestion of leucine results in a signal to build new muscle tissue. However, this signal is maximised after 2-3g of leucine is ingested (this is known as the leucine threshold) (1), and the signal will only result in hypertrophy if the raw materials and energy (i.e. other amino acids and an energy source such as carbohydrate or fat) are there to allow growth to occur. Alongside leucine, the other BCAAs isoleucine and valine are present in up to 20% of muscle tissue (2), leading to the hypothesis that supplementing with BCAAs could potentially have a positive impact on the growth and maintenance of muscle tissue.

It is also worth noting that many protein rich foods contain BCAAs. Some foods, known as ‘whole proteins’, contain all 21 amino acids and thus also contain BCAAs. Animal based protein sources (meat, eggs, dairy, whey are typically whole proteins). Below is a table showing how much protein rich foods are needed for 10 g of BCAAs (the dose required to hit the leucine threshold). It is fairly easy to eat adequate amounts of BCAAs by eating whole, protein rich foods as per recommendations for protein intake to be in the region of 2.3-3.1 g per kg fat free mass per day (3).

A quick note about the price of BCAAs…

While you can get unflavoured BCAA powder for a reasonable price (as shown be the lower range in the table), a lot of companies will charge a premium for BCAAs in capsule form or as a flavoured drink, as BCAAs quite frankly taste like shit. The range in my table highlights the cheapest and most expensive prices I could find after a very quick Google search.

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BCAAs marketability is based on early animal studies on BCAA supplementation. However, many of the human studies cited as ‘proof’ to leucine or BCAA’s effectiveness in enhancing a hypertrophic response are flawed in a number of ways. For example, subjects’ diets were not controlled for (4), BCAAs were compared to an inadequate (from a BCAA POV) protein source (soy) (5), or the study duration was not long enough (6). The marketeers often also fail to cite the studies which showed BCAAs made no difference to trainees’ body compositions (7–10).

Marketeers would also have you believe that BCAAs are essential to attenuate muscle loss when dieting or when training fasted, such as during an intermittent fast (check out my write up on IF here). While BCAAs will prevent excessive muscle loss in conditions of inadequate protein, they aren’t any more effective than other whole protein source (especially whey) (11,12). If you refer to the table above, you can see that it is pretty easy to get 5-10g BCAAs from milk or whey if that is your concern. For example, a 30 g whey dose before and after training ‘fasted’ would provide ~7 g BCAAs allowing you need to hit the leucine threshold (3 g) and offset any potential for muscle loss (which is a debatable topic itself). It will also provide the other essential amino acids and has the potential for better uptake from the gut and into the muscle (13). Here is an extract from that study:


“Despite the popularity of BCAA supplements we find shockingly little evidence for their efficacy in promoting MPS or lean mass gains and would advise the use of intact proteins as opposed to a purified combination of BCAA that appear to antagonize each other in terms of transport both into into circulation and likely in to the muscle”.


Essentially, if you are consuming enough protein (and thus have enough amino acids in your system), you don’t need to ‘top them up’ during your workout. If you are training in a fasted state, depending on when the meal before, or the next meal after training is you probably still don’t need to top up your amino acids. Even if you did, there would be better choices; for example, whey protein.

From a muscle building POV, BCAAs do ‘work’ (in a protein deprived, or fasted state) but they are potentially a more expensive and less efficacious option than milk, whey or any other whole, complete protein. Despite my seemingly very negative stance on BCAAs, I am still very open minded. Intriguing research is emerging around the use of BCAAs in ‘low energy state’ endurance training to reduce perception of fatigue (14), central nervous system fatigue (15), time to fatigue (16) and muscle damage (17) and I’m sure future studies will shed more conclusive light on their effectiveness (or lack of) with regards to hypertrophy. Currently, there simply isn’t the body of research to recommend them to any gym goer, but perhaps it is something worth keeping an eye on over the next few years

What this all means is that BCAAs aren’t all they are cracked up to be. They aren’t as beneficial/important as the salespeople claim they are, and even when they do have a use, there is probably a better and cheaper option out there which you probably already have in your fridge. To balance that view, I would suggest to stay open minded. The science of nutrition, supplements, muscle building and fat loss is constantly moving forwards and we are constantly learning about the mechanisms that allow us to make ‘dem gainz’. It may come to light that they are beneficial for a reason not yet hypothesised. In the meantime, I advise to stick with the basics (adequate protein and calorie intake, sensible, progressive lifting programme) and be wary of anyone selling a supplement based on their nutritional viewpoints.

As an addition, here is a secondary post examining Vegans’ ‘needs’ for BCAAs  –




  1. Tipton KD, Ferrando AA, Phillips SM, Doyle D, Wolfe RR. Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol. 1999 Apr;276(4 Pt 1):E628–34.
  2. Riazi R, Wykes LJ, Ball RO, Pencharz PB. The total branched-chain amino acid requirement in young healthy adult men determined by indicator amino acid oxidation by use of L-[1-13C]phenylalanine. J Nutr. 2003 May;133(5):1383–9.
  3. Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr. 2014 May 12;11:20.
  4. Coburn JW, Housh DJ, Housh TJ, Malek MH, Beck TW, Cramer JT, et al. Effects of Leucine and Whey Protein Supplementation During Eight Weeks of Unilateral Resistance Training. J Strength Cond Res. 2006;20(2):284.
  5. Mourier A, Bigard AX, de Kerviler E, Roger B, Legrand H, Guezennec CY. Combined effects of caloric restriction and branched-chain amino acid supplementation on body composition and exercise performance in elite wrestlers. Int J Sports Med. 1997 Jan;18(1):47–55.
  6. Sharp CPM, Pearson DR. Amino acid supplements and recovery from high-intensity resistance training. J Strength Cond Res Natl Strength Cond Assoc. 2010 Apr;24(4):1125–30.
  7. Balage M, Dardevet D. Long-term effects of leucine supplementation on body composition. Curr Opin Clin Nutr Metab Care. 2010 May;13(3):265–70.
  8. Crowe MJ, Weatherson JN, Bowden BF. Effects of dietary leucine supplementation on exercise performance. Eur J Appl Physiol. 2006 Aug;97(6):664–72.
  9. Koopman R, Pannemans DLE, Jeukendrup AE, Gijsen AP, Senden JMG, Halliday D, et al. Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise. Am J Physiol Endocrinol Metab. 2004 Oct;287(4):E712–20.
  10. Spillane M, Emerson C, Willoughby DS. The effects of 8 weeks of heavy resistance training and branched-chain amino acid supplementation on body composition and muscle performance. Nutr Health. 2012 Oct;21(4):263–73.
  11. Hulmi JJ, Lockwood CM, Stout JR. Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein. Nutr Metab. 2010;7:51.
  12. Katsanos CS, Chinkes DL, Paddon-Jones D, Zhang X, Aarsland A, Wolfe RR. Whey protein ingestion in elderly persons results in greater muscle protein accrual than ingestion of its constituent essential amino acid content. Nutr Res N Y N. 2008 Oct;28(10):651–8.
  13. Morton RW, McGlory C, Phillips SM. Nutritional interventions to augment resistance training-induced skeletal muscle hypertrophy. Front Physiol [Internet]. 2015 Sep 3 [cited 2016 Aug 23];6. Available from:
  14. Newsholme EA, Blomstrand E. Branched-chain amino acids and central fatigue. J Nutr. 2006 Jan;136(1 Suppl):274S – 6S.
  15. Greer BK, White JP, Arguello EM, Haymes EM. Branched-chain amino acid supplementation lowers perceived exertion but does not affect performance in untrained males. J Strength Cond Res Natl Strength Cond Assoc. 2011 Feb;25(2):539–44.
  16. Gualano AB, Bozza T, Lopes De Campos P, Roschel H, Dos Santos Costa A, Luiz Marquezi M, et al. Branched-chain amino acids supplementation enhances exercise capacity and lipid oxidation during endurance exercise after muscle glycogen depletion. J Sports Med Phys Fitness. 2011 Mar;51(1):82–8.
  17. Nelson AR, Phillips SM, Stellingwerff T, Rezzi S, Bruce SJ, Breton I, et al. A protein-leucine supplement increases branched-chain amino acid and nitrogen turnover but not performance. Med Sci Sports Exerc. 2012 Jan;44(1):57–68.


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