By Dr Adam Collins, Form’s Head of Nutrition and Program Director for the MSc and BSc Nutrition courses at the University of Surrey. A qualified nutritionist for nearly 20 years Dr Collins is also a PhD in energy expenditure and body composition. His research interests lie in exercise nutrition, body composition, exercise intensity and energy balance, intermittent fasting and timing of food around exercise.
This is part one of a two part series. Part two coming soon.
The benefits of Protein have long been studied and understood in terms of both sports nutrition and nutrition in general. Following a more reductionist approach however, protein has been viewed by the properties of its individual components, and to this end, specific amino acids identified as being better than others when it comes to certain benefits. Branched chain amino acids (BCAAs) very much sit in this category. But what is the rationale for taking these specifically? And can they really single handedly give you all the claimed BCAA benefits? And actually, what are BCAAs?!
Firstly, let us go back to basics for a minute. All proteins are constructed from amino acids (AAs), with the structure and function of that protein dictated by which ones are used, in what order, and how many in total (some as small as 10-20, others in the 100s of thousands). There are only 20 different amino acids, yet the length and combination of these gives rise to a near infinite range of possible proteins that can be made. The often used analogy is to think of amino acids as letters, proteins are then words.
These 20 different amino acids have classically been categorised into two groups, namely essential and non-essential. The essential amino acids (EAAs) are so called because the body cannot synthesise or manufacture them, so they have to be imported from the diet. Or taken in the form of a BCAA supplement. In fact 9 out of the 20 are classified as EAAs. The other 11 amino acids are technically non-essential, but in reality only 5 of the 11 can be manufactured and made available enough not to have to rely on importing them from the diet. Table 1 below shows a list of all 20 amino acids categorized by essentiality. Within the EAAs, the three branched chain amino acids (BCAAs) are highlighted, so called simply because they have a branched hydrocarbon chain attached to the amino group.
Congratulations, you now know more than most people: what BCAAs actually are.
Table 1: Categorization of amino acids in the diet
|Essential Amino Acids (EAAs)
(may need some importing)
(import not essential)
*denotes branched chain amino acids (BCAAs).
Now you know what BCAAs are, why do they get attention? BCAAs receive special attention for two main reasons. Firstly due to their proposed ability to stimulate muscle protein synthesis, and secondly their ability to delay the onset of fatigue (hence enhance performance). In this article we look at the first, BCAAs and muscle protein synthesis. Part two will cover the second.
BCAAs and muscle protein synthesis.
Body protein (e.g. muscle) is not static, it can be both broken down to liberate amino acids (muscle breakdown), or built up/increased from the building blocks of amino acids (muscle protein synthesis). If muscle protein synthesis (MPS) outweighs the extent of muscle protein breakdown (MPB), then you get net muscle protein synthesis, hence muscle repair and/or growth.
Various factors will stimulate muscle protein synthesis, by activating the anabolic MTORC1 signalling pathways that regulate MPS. These include insulin (and IGF1), mechanical strain through the muscle (i.e. exercise), and the presence of certain amino acids. BCAAs are important in this regard, in particular the BCAA Leucine. Leucine has a dual effect on stimulating MPS. Firstly, Leucine is suggested to be insulinotropic, contributing to increased insulin release irrespective of carbohydrate (i.e. glucose) availability. Insulin will strongly stimulates MPS but also aid uptake of other amino acids into the muscle (see later). Secondly, uptake of Leucine can directly increase levels of active MTORC1 in the cell and potentially activate the signalling pathway at several points, e.g. Akt (Protein kinase B). These insulin independent effects of leucine on MPS have been shown to be further enhanced by presence of the other BCAAs (valine and isoleucine).
If all that was over your head, just know that there is strong evidence to support the notion that leucine (with or without other BCAAs) is a significant stimulator of MPS.
So far, so good, but stimulating MPS is not enough. In order to actually achieve muscle protein synthesis you have to have the materials with which to build the muscle, i.e. amino acids. In particular you need to make sure you have an adequate supply of all 9 essential amino acids (EAAs), not just the BCAAs. You also need to have the means to manufacture (if needed) the non-essential and conditionally essential ones from other things like carbohydrate, hence the reason why insulin and IGF1 are key promoters as they signify available fuel or energy. The essential amino acids are indeed the truly limiting factor when it comes to the magnitude of MPS. If the import of EAAs is inadequate then the only way to get these would be from body protein or indeed muscle protein itself, hence protein breakdown (MPB) will increase alongside this increase in MPS. The result is less net protein synthesis.
So yes, BCAAs (in particular Leucine) are true stimulators of MPS, but a few grams of these will not singlehandedly lead to muscle synthesis, you need an adequate supply of EAAs as well. And of course, don’t forget the stimulus of the exercise itself and ensuring you have adequate fuel/energy overall.
In practice what this means is that there is no need to consume BCAA’s supplements alone. Rather what you should look for are complete sources of protein either in your diet or from protein supplements when required. Indeed, studies show that in terms of net protein synthesis, complete protein is better than BCAAs alone.
This is why we use the blend of pea, rice, hemp and algae protein we do – to provide a complete source of protein. The exact formulation of each protein is chosen so levels of amino acids are such that we ensure the optimum level of BCAAs without the need for additional supplements.
BCAAs will not on their own do everything touted in the marketing. To provide the benefits you need all the other amino acids, i.e a complete protein and studies show complete proteins to be superior to BCAA’s alone.
The take home is therefore if you ensure you eat or supplement complete proteins to meet your protein requirements you have no need for BCAA supplements.
To find a good protein supplement, read the label, ensure it is has a complete amino acid profile with a good amount of BCAAs and at least 1.5g Leucine. Double check these come from protein itself and are not added individually, the dodgy practice of ‘protein spiking’ – adding individual amino acids rather than more costly proteins. Our Performance Protein is a complete protein with over 5g BCAAs per serving, all from pea, rice, hemp and algae proteins.
Further reading and references
Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? Wolfe RR.J Int Soc Sports Nutr. 2017 Aug 22;14:30. doi: 10.1186/s12970-017-0184-9. eCollection 2017.
Branched-Chain Amino Acid Ingestion Stimulates Muscle Myofibrillar Protein Synthesis following Resistance Exercise in Humans. Jackman SR, Witard OC, Philp A, Wallis GA, Baar K, Tipton KD. Front Physiol. 2017 Jun 7;8:390. doi: 10.3389/fphys.2017.00390. eCollection 2017.