Branched Chain Amino Acid Supplementation.
When it comes to macronutrients, protein is king. The role of protein in the diet is critical for both health and sports performance related reasons, reasons for which do not get discussed enough in the media unfortunately. One of the main reasons for ingesting protein is to stimulate a process called muscle protein synthesis (MPS), which is responsible for the construction of new muscle fibres. It achieves this, along with a whole host of other things but for simplicity of reading and understanding I am going to right this in respect to building muscle.
Muscle protein is comprised of 20 amino acids, 11 non-essential amino acids (NEAA) and 9 essential amino acids (EAA), essential meaning that the body cannot synthesis these itself and they must be consumed through diet. Muscle protein is constantly in a state of flux between muscle protein synthesis and muscle protein breakdown (see above), this is called muscle protein turnover. To build new muscle fibres and repair them after training, the rate of MPS must exceed the rate of muscle protein breakdown, the EAA along with the NEAA must also be present in the body, without them the body cannot produce new muscle fibres.
The branched chain amino acids (BCAAs) are made up of leucine, iso-leucine and valine. The information that has been perpetuated in recent years is that ingestion of these BCAAs can stimulate muscle protein synthesis to achieve maximum gains in muscle mass. The majority of people who take BCAA take them intra-workout as they believe the effects will reduce the rate of MPB during training, but also increase the rate of MPS. Other scenarios in which people take BCAAs are before fasted cardio, as a pre-workout, in between meals or just as a flavour addition to water to hydrate during the day. All under the assumption that BCAA have this magical ability to gain muscle and lose fat at the same time. Thanks to a new review by Robert Wolfe (2017), we now have conclusive evidence that these notions are now unwarranted. The following sections are going to take you through where this information has previously been misinterpreted and also the information that we have now.
Can BCAAs Stimulate MPS?
While this isn't completely true, there is method behind the madness as they say. The main thought process around BCAAs stimulating MPS is due to the presence of Leucine. Leucine is one of the major stimulatory AA when it comes to MPS. Research has shown that 3g of leucine is the threshold for stimulating MPS. However, stimulating MPS is very different to protein accretion. To optimally build new muscle fibres MPS needs to be maximally stimulated, but there also has to be adequate supply of all the NEAA and EAA. This isn't the case when ingesting BCAA so as the review shows this can be actually detrimental to our progress long term. Constant stimulation of MPS without adequate supply of the building blocks for muscle growth can lead to placing you in a negative protein turnover balance.
When considering the stimulatory effect of leucine, you also have to consider the competition for entry into the cell when consume concomitantly with the other two BCAA. When consumed together they will fight for entry into the cell, depending on the ratio of leucine : iso-leucine : valine. Hence, if using leucine as a stimulant for MPS, in combination with a high protein meal, then you are better served taking it in isolation rather than as a BCAA supplement.
When considering the stimulatory effect of leucine, you also have to consider the competition for entry into the cell when consume concomitantly with the other two BCAA. When consumed together they will fight for entry into the cell, depending on the ratio of leucine : iso-leucine : valine. Hence, if using leucine as a stimulant for MPS, in combination with a high protein meal, then you are better served taking it in isolation rather than as a BCAA supplement.
Conclusion
BCAA supplementation cannot be justified by the reasoning of increase MPS. One's diet must be sufficient in all the amino acids to provide adequate supply of AA to the cells to rebuild and repair muscle fibres post-training. Supplementing with leucine on it's own, in combination with a high protein diet, can be a useful strategy to maximally stimulate MPS and provide ample source of AA to build new muscle tissue. There may be scope to use it as an intra-workout supplement for longer training sessions > 2 hours, or during endurance events such as cycling.
Money would be better spent elsewhere on supplements like whey protein etc. For the full review the reference is below. You can also click the download link below to download it directly.
Money would be better spent elsewhere on supplements like whey protein etc. For the full review the reference is below. You can also click the download link below to download it directly.
| Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? |
References:
- Wolfe, R.R., 2017. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?. Journal of the International Society of Sports Nutrition, 14(1), p.30.
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