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BCAA supplements: useful or not?

Branched-chain amino acids (BCAAs), namely leucine, isoleucine and valine, are three of the nine essential amino acids that the human body cannot synthesize itself. These compounds must be ingested through the diet, making them crucial for everyone, especially those who engage in regular physical activity. The importance of BCAAs goes beyond basic nutrition; they are fundamental to muscle health, influencing muscle growth, recovery and overall metabolic regulation.

Leucine, isoleucine and valine are distinguished from other amino acids by their unique branched chemical structure, which plays an essential role in their metabolic functions within the body. Together, they account for around 14% of the amino acids found in skeletal muscle. Among them, leucine is particularly renowned for its ability to stimulate muscle protein synthesis, the process by which the body repairs and builds muscle fibers. It is also thought to be a key regulator of the mTOR signalling pathway.

The popularity of BCAA supplementation in the sporting community is quite strong, with 37% of exercisers claiming to consume them. Whether consumed in protein-rich foods or in the form of dietary supplements, BCAAs are said to enhance performance, promote muscle protein synthesis and speed recovery. However, despite their widespread use, the effectiveness of BCAA supplementation continues to be the subject of research and debate, particularly when compared to whole protein sources (protein powder, fish, meat, etc.). So, is it worth supplementing with BCAAs?

Effects of BCAAs on muscle protein synthesis and breakdown

Muscle mass growth is determined by the balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). When the rate of MPS exceeds that of MPB, the net protein balance is said to be positive, and protein is accumulated. Conversely, when MPB exceeds MPS, the net protein balance is negative, leading to a loss of muscle mass.

The main regulators of these metabolic processes are protein intake, exercise and caloric deficit:

• With regard to protein intake, the ingestion of proteins, and more precisely of their constituent amino acids, stimulates MPS in a dose-dependent manner. However, this effect is transient, lasting only a few hours. Studies have shown that it is mainly essential amino acids that positively stimulate MPS. And some human studies suggest that leucine alone stimulates protein synthesis.
• With regard to exercise, a muscle-building session stimulates MPS for up to 48 hours. But without amino acids, the net protein balance would remain negative. Some studies have shown that consuming protein or essential amino acids after weight training stimulates MPS to such an extent that the net protein balance becomes positive. This effect lasts around 24 hours.
• With regard to caloric deficit, normal or post-meal MPS levels are reduced, and amino acid oxidation throughout the body increases. A resistance training workout can, under these conditions, increase MPS to levels observed at energy balance. And the ingestion of protein after the session can stimulate MPS to higher levels.

To prevent the accumulation of damaged proteins and prevent cellular dysfunction, proteins throughout the body undergo constant turnover. Muscle anabolism is the result of a positive net protein balance. It is therefore necessary to stimulate MPS and reduce MPB... However, several studies have shown that a muscle-building session stimulates MPB for up to 24 hours post-exercise. Similarly, some studies have shown an increase in MPB levels during a period of caloric restriction.

As mentioned above, the ingestion of proteins or essential amino acids results in a stimulation of MPS. But amino acids can also stimulate insulin concentration. Insulin is a powerful regulator of protein turnover thanks to its ability to suppress MPB. Thus, the stimulation of MPB following a bodybuilding session could be prevented when amino acids are ingested immediately after the session. This would facilitate a positive net protein balance.

Effectiveness of BCAA supplementation compared with complete protein supplementation

BCAAs can stimulate MPS levels in humans, both at rest and after resistance exercise. However, the stimulation of postprandial MPS levels following ingestion of isolated BCAAs is transient and suboptimal compared with the MPS response obtained following ingestion of a complete protein (e.g. whey) matched for BCAA intake, but providing the full complement of amino acids.

For example, a 2019 study compared the impact of ingesting 6g BCAA and 30g milk protein (containing 6g BCAA), at rest, in senior men on myofibrillar protein synthesis overnight. BCAA intake stimulated MPS in the same way as 30g milk protein, however the duration of stimulation was much shorter (~2 hours). Whereas with milk protein, MPS stimulation remained high for up to 5 hours after ingestion. So, although BCAAs can stimulate MPS, the effect is short-lived, probably due to a lack of the other amino acids.

Similarly, several studies have compared the impact of ingesting different sources of amino acids after a resistance training session. While ingestion of BCAAs increases MPS after exercise, the rates of increase are 50% lower than those observed with whey protein containing the same quantity of BCAAs.

Finally, if isolated ingestion of BCAA stimulates MPS after a workout, consumption of a complete protein source may be necessary to optimally stimulate MPS, and for longer period of time. Furthermore, it seems that adding BCAAs to a sufficient dose of whey, soy or mycoprotein protein is useless in terms of stimulating MPS after a workout.

Practical Applications

Branched-chain amino acids (BCAAs) occupy a prominent position due to their potential to influence muscle protein synthesis and breakdown. However, the current body of research suggests that, while BCAAs may have a positive effect on muscle metabolism, their isolated supplementation is not necessary or superior to the consumption of complete protein sources. The most marked benefits of BCAAs (reduction in muscle protein breakdown and temporary increase in muscle protein synthesis) highlight their potential as a supplement. However, these effects are inferior to those provided by a complete protein (whey protein or mycoprotein) containing the same dose of BCAAs.

For athletes and fitness enthusiasts aiming for optimal muscle growth and recovery, the emphasis should be on a well-balanced diet rich in complete proteins. Such a diet naturally ensures an adequate intake of all essential amino acids, including BCAAs, creating the best possible environment for muscle health and athletic performance. BCAA supplementation is therefore not necessary if your daily protein intake meets your needs.

References

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