Branched Chain Amino Acids (BCAAs) are a specific category of amino acids, which are the building blocks for proteins. They form a subgroup in the essential amino acids (EAAS) containing three amino acids leucine, isoleucine, and valine (Jäger et al., 2017). The available amino acids in EW have a left-handed configuration. Essential amino acids cannot be produced by the body and therefore have to be included in the diet to fulfill the needs of the body for a proper function. BCAAs are taken up from both animal based as well as plant based foods (Nagata et al., 2013; Zheng et al., 2016).
Effects related to sports The effects of BCAAs which are investigated in literature research mainly focuses on two different aspects. The first aspect is the reduction of fatigue (Meeusen, 2014), which is focused mostly on endurance exercise. The second aspect is the reduction of muscle damage and increase of muscle mass (Fouré et al., 2017). There are different kinds of fatigue, the fatigue addressed here is central fatigue. Central fatigue kicks in when there are different signals in the body sensed by the central nervous system, causing changes in neurotransmitters in the brain (Gervasi et al., 2020). This is different to muscular fatigue, and therefore those two kinds of fatigue are not necessarily related (Abumoh’D et al., 2020). Also, ingestion of BCAAs is not related to muscular fatigue (Areces et al., 2015). Intake of BCAAs is thought to postpone the central fatigue, by crossing the blood brain barrier and thereby competing with an amino acid called tryptophan (Gervasi et al., 2020). Competing with tryptophan is beneficial, since this amino acid is the precursor for the neurotransmitter related to increased tiredness (Gervasi et al., 2020). This is the theoretical basis. Various researchers investigated the effect of BCAA intake on performance in different disciplinary 18 sports. Seven RCTs compared the effect of BCAA (sometimes combined with other ingredients) and a placebo on performance, which was measured in physical performance and decision making. All these studies found that the intake of BCAA before the work-out helped to improve the performance of different athletes by lengthening the time to exhaustion (TTE) and sometimes increasing the speed. In one study, participants were untrained (Gervasi et al., 2020), in another study participants were elite athletes (Chen et al., 2016). Both studies found a positive effect upon BCAA intake. BCAA intake can help to resist tiredness for a longer time (see for example (Gervasi et al., 2020) and (Abumoh’D et al., 2020)) For an exact overview, see Appendix 4.
The second aspect is about muscles, on which BCAAs can have a dual effect. BCAAs are thought to enhance muscle building (Kerksick et al., 2018) and reduce the amount of muscle damage (Fouré & Bendahan, 2017). Fouré & Bendahan (2017) have written a systematic review including 11 articles. A conclusion of this review is that there are potentially benefits for low up to moderate muscle damage. However, these potential benefits are only applicable when the athlete has daily a high intake of BCAAs for a longer period of time before the muscle damage occurs. Also, when this muscle damage is caused by high intensity exercise, the reduction of the damage seems to be little. Another systematic review (Pasiakos et al., 2014) addresses the question if proteins help to increase muscle mass and strength. In the first weeks, in untrained individuals, proteins did not have much effect, but a constant protein intake combined with intensive exercise promotes gains in muscle weight and strength.
Strength and short distance athletes Different studies were performed with short distance athletes or strength athletes, showing the positive effect of BCAA intake. The concentrations that were found to be functional, were all combined with arginine, alanine or citrulline (3.2 g BCAA+1.6 g L-alanine (Gervasi et al., 2020); 0.085 g/kg BCAA +0.05g/kg arginine +0.05 g/kg citrulline (Hsueh et al., 2018); 0.17 g/kg BCAA +0.05 g/kg arginine +0.05 g/kg citrulline (Chen et al., 2016)).
Middle distance athletes and game players One study reports a positive effect of BCAA intake in game players, with a doses of 0.17 g/kg BW BCAA. The used ratio of leucine:isoleucine:valine=2:1:1, this is the ratio in which the amino acids are present in the body (Chang et al., 2015).
Endurance athletes Different studies are performed on the effect of BCAA on endurance sporters. They all found that BCAA had a positive effect on sport performance. A supplement contained 6g valine, 5g leucine and 2g isoleucine (Abumoh’D et al., 2020); 0.080 g/kg BCAA (20%isoleucine, 24% valine, 46% leucine) (Kim et al., 2013); 0.110 g/kg BCAA contained 25% l-isoleucine, 45% l-leucine, and 30% l-valine (Moberg et al., 2016). The ratios differ in the various studies. BCAAs are categorised in Group B according to the AIS supplement framework (Australian Institute of Sport, 2019).