Branched-chain amino acids (BCAAs) – are often hailed in the fitness industry as essential if you are serious about results. But are BCAA supplements really all they’re cracked up to be?
Fitness Savvy has produced this article using the most up-to-date scientific research available, covering areas such as optimum ratio, side effects, food sources, as well as their association with insulin resistance and type 2 diabetes. We have also tackled some bold claims to see if they are valid, and included a little info on each of the branched-chain amino acids to show what makes each of them special.
What Are Branched-Chain Amino Acids?
Branched-chain amino acids are, as their name suggests, amino acids. There are three of them – leucine, isoleucine and valine – which make up 35% of the essential amino acids in muscle proteins and 40% of the preformed amino acids required by mammals.
BCAAs are known to be oxidized (broken down to release energy) in skeletal muscle. Exercise greatly increases energy expenditure and therefore promotes oxidation of branched-chain amino acids. So naturally one would look to reduce the risk of this happening.
Leucine, isoleucine and valine are essential amino acids; this basically means that they cannot be synthesized from scratch by organisms, so must be supplied in your diet. Without going into in-depth scientific detail, the reason you should be interested in BCAAs is because they promote protein synthesis and turnover.
- Protein synthesis is the process whereby biological cells generate new proteins
- Protein turnover is the balance between protein synthesis and protein degradation
When protein synthesis is greater than protein breakdown, your body is anabolic. This is the preferred state when looking to build muscle or stay lean, as it means you are building lean tissue at a faster rate than you are breaking it down.
When protein breakdown is greater than protein synthesis, your body is catabolic. This means that you are actively breaking down lean tissue faster than you are building it. This is obviously not great if looking to build or maintain muscle.
When you hit the gym, you might notice the following day or two (or seven, if it was leg day!) you experience muscle aches, sometimes referred to as DOMS (delayed onset muscle soreness). During your workout, you damaged muscle fibres and now you need to recover. Ideally you should consume adequate protein to aid protein synthesis. However, in situations where protein breakdown falls too low, the body is unable to remove damaged muscle cells, which, in turn prevent the growth of new muscle cells. Which again, is something we don’t want.
Show Me Some Evidence!
If you need convincing that BCAAs are important for exercise and recovery – but don’t have a spare few days to research scientific papers – you will be glad to hear we have it covered. We have examined many papers to find evidence concerning the benefits and side-effects of branched-chain amino acids.
Claim 1: Branched-Chain Amino Acids Stimulate Muscle Growth
A study investigating the effect of BCAA supplementation and resistance exercise1 found that:
“BCAA, ingested during and after resistance exercise, mediate signal transduction through p70(S6k) in skeletal muscle”.
A sentence, which to most means absolutely nothing! So for your convenience, we have translated it into English:
The chemical signals which modify proteins to help repair and grow muscle are assisted by branched-chain amino acid consumption during and after resistance exercise.
This means that BCAA ingestion aids with repairing and growing muscle tissue. Which is a good thing. In fact, there are countless studies supporting the role BCAAs play in protein synthesis, and this is now considered scientific fact.
Claim 2: BCAA Supplements Will Aid Recovery Following Exercise and Reduce Fatigue
For the amateur gym enthusiast, the speed at which one recovers might not be such a big issue. However, if you take your training seriously, anything with potential to speed up recovery is welcome. The next paper we refer to investigated the effects of acute BCAA supplementation on recovery from exercise-induced muscle damage, among experienced resistance-trained athletes.2 It concluded that:
“Acute supplementation of BCAAs (0.087 g/kg) increased the rate of recovery in isometric strength, CMJ height and perceived muscle soreness compared to placebo after a hypertrophy-based training session among diet-controlled, resistance-trained athletes.”
In this study, the ratio of BCAAs used was 2:1:1.
In contrast, a study conducted in 2016 which looked at three consecutive days of intense lower body training found that BCAA supplementation did not affect recovery markers compared to a carbohydrate only drink.3
However, there were significant limitations to this study, as follows:
- The supplements were not standardized to carbohydrate or calorie content, and had participants consumed isocaloric amounts of each supplement, the results may have differed.
- The training protocol was brief and lacked a degree of external validity (i.e., not many practitioners or athletes would engage in three consecutive days of heavy squats).
- No skeletal muscle biopsies were obtained and analysed for infiltrating inflammatory cells and/or histological signs of muscle damage.
Both the above studies looked at resistance training and hypertrophy. So how about endurance training? Are BCAAs beneficial when that’s your primary form of exercise? A study conducted by Coombes & McNaughton, 2000,4 investigated the effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise. Creatine kinase and lactate dehydrogenase are enzymes associated with muscle damage, so are recognised as accurate indicators.
The study compared two groups: both consumed the recommended daily allowance (RDA) of BCAAs, with one group taking an additional supplementation of 12g per day. It found that supplementary BCAA intake reduced muscle damage more so than the group simply consuming the RDA, suggesting that extra supplementation is of benefit.
Another study5 which looked at the effects of BCAA on endurance athletes concluded that:
“Supplementary BCAA decreased serum concentrations of the intramuscular enzymes following exhaustive exercise. This observation suggests that BCAA supplementation may reduce the muscle damage associated with endurance exercise.”
Another paper6 studied nine untrained men, who performed three 90 min cycling bouts, separated by 8 weeks. They consumed either the BCAA, a carbohydrate drink or a placebo. The CK activities were significantly lower after the BCAA trial than in the placebo trial at 4, 24, and 48 hours postexercise, as well as lower than the carbohydrate beverage at 24 hours postexercise.
Claim 3: Exercise Is Often Cited as Causing Muscle Catabolism
We refer to a study entitled: Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise.7 In the concluding remarks, the report states:
“It is clear that exercise promotes degradation of BCAAs. Promotion of fatty acid oxidation appears to be associated with greater rates of BCAA oxidation, which suggests that fatty acids may be regulators of BCAA oxidation. Furthermore, muscle-protein synthesis is enhanced after exercise. From these findings, it may be concluded that the BCAA requirement is increased by exercise.”
In conclusion, we believe there appears to be sufficient evidence to suggest that BCAAs are important for stimulating muscle growth and preventing muscle breakdown, beneficial in aiding recovery (unless you’re crazy and decide three consecutive days of squats is a good idea!) and that even if consuming the recommended daily amount, extra supplementation could be of benefit.
What is the 2:1:1 Ratio?
When looking at the packaging of BCAA supplements, you will often see the 2:1:1 ratio. This the ratio of the three BCAAs mentioned earlier, and is as follows:
- 2 parts leucine
- 1 part isoleucine
- 1 part valine
You may notice other ratios on packaging, with the manufacturer marketing different reasons as to why their supplement is superior, and what benefits will be observed by using a different ratio. The ratio will nearly always include a higher proportion of leucine (more on this in a minute). Interestingly, there has not been a huge amount of research conducted in aid of discovering the optimum ratio, and so any claims made on supplement packaging should be taken with a pinch of salt. In fact, although research is limited, one thing that does seem to be apparent is that larger proportions of leucine could actually be detrimental. The only exception being in regards to endurance, or “steady state” exercise. One study found that a higher dosage of leucine produced favourable results, increasing muscle protein synthesis by over 30% when using a ratio of 4:1:1.8
Leucine is an mTOR activator. mTOR links with other proteins and serves as a core component of protein complexes which regulate various cellular processes such as cell growth, cell proliferation, cell survival, and the all-important – protein synthesis. It also promotes the activation of insulin receptors; these receptors play a key role in the regulation of glucose homeostasis (a functional process that under certain conditions may result in a range of clinical manifestations including diabetes and cancer).
Leucine has the capacity to directly stimulate muscle protein synthesis, and so begs the question: why is it not promoted more often as a standalone supplement? One study conducted in 20089 examined the effects of oral BCAAs and leucine supplementation combined with an acute lower-body resistance exercise. The study sought to discover if an isolated leucine supplement was superior to BCAA supplementation including isoleucine and valine in regards to muscle protein synthesis. It found leucine to perform better than the placebo, but not as well as the BCAA of 2:1:1.
While isoleucine is more powerful than valine regarding muscle protein synthesis, it is far weaker than leucine. Isoleucine does not promote glycogen synthesis, however, is able to significantly increase glucose uptake as well as glucose usage during exercise10 – which is great, due to the importance of glucose as a fuel for contracting muscles.
Although extensive human testing has not been conducted, isoleucine is regarded as the BCAA which mediates glucose uptake into cells and breakdown into energy to a greater degree than other amino acids and may enhance performance if taken pre-workout when training fasted, for example.
Valine is an important amino acid which aids in regulating blood sugar. It assists with stimulating the central nervous system and mental functioning. There are limited studies using valine in isolation, but it is understood to be necessary, along with the other two BCAAs to ensure proper function. Valine aids in the prevention of muscle breakdown during periods of strenuous exercise by supplying extra glucose.
A study from 2001 conducted by Gomez-Merino et al. looked at the effects of valine on serotonin levels.11 When serotonin (a neurotransmitter) is released during exercise, the brain receives the signal of fatigue – which naturally leads to poorer performance, lower strength and reduced endurance. Tryptophan uptake (which increases during exercise) is converted in the brain to serotonin. When valine is present, they compete over entry to the brain. This study shows valine to be stronger, denying tryptophan the chance to convert to serotonin, therefore reducing the detrimental effects associated with it. This study concludes that there are both psychological and physiological benefits of valine.
I’ve Been Told That I Should Supplement with Glutamine Instead. What Is the Story Here?
Some studies have found supplementation of glutamine to be superior to BCAAs. One study in particular looked specifically at blood fatigue factors, and cytokines (substances secreted by certain cells of the immune system which have an effect on other cells).12 2,000 metres of rowing at the maximal intensity was performed, using an indoor rowing machine. The subjects were supplied with either BCAA, placebo or glutamine. The study concluded that:
“It seemed that glutamine supplementation had a positive effect on the decrease in fatigue factor stimulation at the recovery stage after maximal intensity exercise compared with supplementation with the placebo or BCAA. Besides, pre-exercise glutamine supplementation seemed to help enhance immune function and the defensive inflammatory reaction.”
Although this particular study showed a more positive result from glutamine supplementation, there is no reason why your diet should not contain both BCAAs and glutamine. You will likely find that many protein powders and other supplements already contain glutamine, so be sure to check the packaging to see if you are already receiving your daily recommendation.
BCAAs Link with Type 2 Diabetes and Insulin Resistance
High levels of BCAA have been linked with increased insulin resistance and Type 2 Diabetes. This has been shown to be the case, regardless of age, sex, glucose tolerance and BMI.13 Studies have shown a causal role of BCAA metabolism in the cause of Type 2 Diabetes.14 However, a study published in February 2017 suggests that it is, in fact, the genetic pre-disposition towards insulin resistance which drives higher levels of circulating BCAAs rather than high levels of BCAA causing insulin resistance.15
As demonstrated in many studies, being active and exercising while eating a varied and nutritional diet is a proven way of improving your insulin sensitivity and would likely outweigh any detrimental effects of minor BCAA supplementation.
However, if diabetes is present in your family, and you are keen to include BCAA supplementation in your diet but are worried about the possibility of increasing your chances of diabetes, we recommend you speak with your doctor first just to be safe.
Are There Any Dangers or Side Effects?
As with all foods and supplements, there are always risks of adverse reactions, allergies or side-effects. While researching for our article we discovered the following:
- As Leucine is responsible for activating mTOR pathways, it may be responsible for speeding up the progression of certain diseases such as Autosomal dominant polycystic kidney disease (ADPKD).16
- Studies have shown that high concentration of branched-chain amino acids promotes oxidative stress and have shown to be pro-imflamatory.17 Based on this, it would be wise to seek professional medical advice from a doctor if you have any medical condition that you fear might be affected by increased BCAA consumption or supplementation.
- A study published in February 2017 highlights the effect of BCAA supplementation in vegans, compared with omnivores. Vegans had a higher insulin sensitivity18 at baseline than the omnivores. During the study, all participants took 15g BCAA per day (women) or 20g per day (men). The results found a negative impact on insulin sensitivity in vegans, concluding that chronic dietary exposure to branched chain amino acids impairs glucose disposal compared with omnivores. This study does not look at the effects of minor supplementation, which – given the already superior insulin sensitivity, might not be of such detriment.
- High intake of leucine can lead to pellagra and hyperammonemia. The upper limit of leucine has been identified as being around 0.5g per kilogram per day for both young and elderly healthy men.19
- It is not advisable to supplement with BCAA if scheduled for surgery. The recommendation is to eliminate supplementation for 2 weeks prior to the operation.20
- Other supplements you are taking may contain BCAAs, as well as foods you may already be commonly eating in your diet. It is wise to ensure that you are not over supplementing.
Branched-chain amino acids are present in many everyday foods – so you don’t have to rely on getting your entire requirement from a pill or powder. To make it easier to plan your diet, we have included a list of foods below which are high in BCAAs:
- Dairy products
- Baked beans
- Lima beans
- Brown rice
- Whole wheat
There is also a fantastic website called SELF Nutrition Data that shows the protein profile of many foods, so you can see if the foods you are consuming are “complete” proteins. Whenever you discover a food with an incomplete protein profile, you can click “find foods with complementary profile” to find items to combine to make complete proteins.
You can also find more advice on complete and incomplete proteins, as well as an awesome calculator to work out your daily protein requirements on our protein calculator page.
Should I Use Powder or Pills?
If looking to supplement BCAAs to aid in your workouts, you will find them in either pill or powder form. Powders will either be flavoured or unflavoured. If you are brave, by all means go for the unflavoured variety – which are renowned for their unpleasant taste which can cause some to gag – you have been warned! There is always the option to mix with another, tastier drink; alternatively there are some fantastic flavoured ones on the market as well.
Pills – contain around 1-1.5g per pill, so you may need to take a few of them! Some find pills hard to swallow. If this is you, then we advise using powders.
Powder – mix with water, or your favourite drink, and consume during your workout. Can work out more cost effective when buying in bulk.
It’s more down to personal preference. Why not try both and see which one better suits your lifestyle?
How Often Should I Supplement with BCAAs?
The frequency of supplementation will rely on a variety of factors. It is advised to consume around 3g of leucine at each meal. Below we have provided our advice. As always, check the manufacturer packaging and/or consult your GP if in any doubt.
- Take BCAA during or post-workout as studies have shown this to be most beneficial – which makes sense as the key attributes of BCAA appear to be protein synthesis and recovery. So taking a supplement before your workout seems unnecessary (with an exception, mentioned below).
- If fasting, supplement with 10 g during your fasted window (2 x 5 g to spread dose out), and again during (5 g) and after exercise (5 g), using a supplement with the 2:1:1 ratio. While in the fasted state, your body will look to oxidise BCAA and muscle tissue could break down. The reason for using a supplement rather than food containing BCAAs is that they contain less calories.
- BCAA requirements can be achieved through diet. However, one of the studies which compared the recommended daily intake of BCAA vs. supplements found that subjects supplementing on top of recommended daily allowances benefited more. This study did not look at increasing the dietary intake of BCAA.
- Too much leucine can be dangerous, so a diet naturally high in BCAA, combined with excessive supplementation can be harmful.
Although branched-chain amino acids have been shown to be detrimental in some circumstances, these are clearly the exceptions, not the norm. We believe that the correlation between BCAAs and Type 2 Diabetes is only relevant in predicting the possibility of developing resistance to insulin,21 as opposed to causing it. In addition, those supplementing with BCAAs are typically engaging in strenuous exercise as opposed to living a sedentary lifestyle which has been shown in an overwhelming number of studies to be beneficial for improving insulin sensitivity. Therefore, any possible negative effects on insulin sensitivity should be more than negated by the active lifestyle lived by those typically interested in increasing their levels of BCAAs.
As always, consult with your doctor if you are unsure of anything.
- Karlsson HK, Nilsson PA, Nilsson J, Chibalin AV, Zierath JR, Blomstrand E. Branched-chain amino acids increase p70S6k phosphorylation in human skeletal muscle after resistance exercise. Am J Physiol Endocrinol Metab. 2004 Jul;287(1):E1-7.
- Waldron M, Whelan K, Jeffries O, Burt D, Howe L, Patterson SD. The effects of acute branched-chain amino acid supplementation on recovery from a single bout of hypertrophy exercise in resistance-trained athletes. Appl Physiol Nutr Metab. 2017 Jan 27
- Kephart WC et al. Post-exercise branched chain amino acid supplementation does not affect recovery markers following three consecutive high intensity resistance training bouts compared to carbohydrate supplementation. J Int Soc Sports Nutr. 2016 Jul 26;13:30. doi: 10.1186/s12970-016-0142-y. eCollection 2016.
- Coombes JS, McNaughton LR: Effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise. J Sports Med Phys Fitness. 2000 Sep;40(3):240-6.
- Kim DH, Kim SH, Jeong WS, Lee HY: Effect of BCAA intake during endurance exercises on fatigue substances, muscle damage substances, and energy metabolism substances. J Exerc Nutrition Biochem. 2013 Dec;17(4):169-80.
- Greer BK, Woodard JL, White JP, Arguello EM, Haymes EM: Branched-chain amino acid supplementation and indicators of muscle damage after endurance exercise. Int J Sport Nutr Exerc Metab. 2007 Dec;17(6):595-607.
- Shimomura Y, Murakami T, Nakai N, Nagasaki M, Harris RA: Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise. J Nutr. 2004 Jun;134(6 Suppl):1583S-1587S.
- Pasiakos SM et. al: Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. Am J Clin Nutr. 2011 Sep;94(3):809-18.
- Paul La Bounty, Bill Campbell, Austin Oetken, and Darryn Willoughby: The effects of oral BCAAs and leucine supplementation combined with an acute lower-body resistance exercise on mTOR and 4E-BP1 activation in humans: preliminary findings. J Int Soc Sports Nutr. 2008; 5(Suppl 1): P21.
- Kleinert M, Liao YH, Nelson JL, Bernard JR, Wang W, Ivy JL: An amino acid mixture enhances insulin-stimulated glucose uptake in isolated rat epitrochlearis muscle. J Appl Physiol (1985). 2011 Jul;111(1):163-9
- Gomez-Merino D et al: Evidence that the branched-chain amino acid L-valine prevents exercise-induced release of 5-HT in rat hippocampus. Int J Sports Med. 2001 Jul;22(5):317-22.
- Koo GH, Woo J, Kang S, Shin KO. Effects of Supplementation with BCAA and L-glutamine on Blood Fatigue Factors and Cytokines in Juvenile Athletes Submitted to Maximal Intensity Rowing Performance. J Phys Ther Sci. 2014 Aug;26(8):1241-6.
- Connelly MA, Wolak-Dinsmore J, Dullaart RPF: Branched Chain Amino Acids Are Associated with Insulin Resistance Independent of Leptin and Adiponectin in Subjects with Varying Degrees of Glucose Tolerance. Metab Syndr Relat Disord. 2017 Feb 21. doi: 10.1089/met.2016.0145.
- Lotta LA et al. Genetic Predisposition to an Impaired Metabolism of the Branched-Chain Amino Acids and Risk of Type 2 Diabetes: A Mendelian Randomisation Analysis. PLoS Med. 2016 Nov 29;13(11):e1002179. doi: 10.1371/journal.pmed.1002179. eCollection 2016.
- Mahendran Y et al. Genetic evidence of a causal effect of insulin resistance on branched-chain amino acid levels. Diabetologia. 2017 May;60(5):873-878. doi: 10.1007/s00125-017-4222-6. Epub 2017 Feb 10.
- Yamamoto J et al. Branched-chain amino acids enhance cyst development in autosomal dominant polycystic kidney disease. Kidney Int. 2017 Mar 21. pii: S0085-2538(17)30072-8. doi: 10.1016/j.kint.2017.01.021.
- Zhenyukh O et al. High concentration of branched-chain amino acids promotes oxidative stress, inflammation and migration of human peripheral blood mononuclear cells via mTORC1 activation. Free Radic Biol Med. 2017 Mar;104:165-177. doi: 10.1016/j.freeradbiomed.2017.01.009. Epub 2017 Jan 13.
- Gojda J et al: Chronic dietary exposure to branched chain amino acids impairs glucose disposal in vegans but not in omnivores. Eur J Clin Nutr. 2017 Feb 1. doi: 10.1038/ejcn.2016.274.
- Rasmussen B, Gilbert E, Turki A, Madden K, Elango R. Determination of the safety of leucine supplementation in healthy elderly men. Amino Acids. 2016 Jul;48(7):1707-16.
- Harvard T.H. Chan School of Public Health.
- McCormack SE et al. Circulating branched-chain amino acid concentrations are associated with obesity and future insulin resistance in children and adolescents. Pediatr Obes. 2013 Feb;8(1):52-61. doi: 10.1111/j.2047-6310.2012.00087.x. Epub 2012 Sep 7.