The BCAA (branched chain amino acid) group consists of three amino acids, leucine, isoleucine and valine. The name comes from their chemical structure, these amino acids have a side chain that contains one carbon. BCAA are essential amino acids, our bodies can’t synthesise them and they have to be obtained from the diet. Like other amino acids they are the basic building blocks of proteins, and hence necessary for life. However, they also have some very specific signalling functions, which gives them a very important role in controlling metabolism. Because of this they have a number of health benefits, beyond that of just being constituents of proteins.
BCAA Stimulate Protein Synthesis
One of BCAAs main roles is to stimulate amino acid uptake by cells, and protein synthesis. This role is so well established that they are given to bedridden patients to slow down muscle wasting. Bodybuilders and athletes, of course, use BCAAs to help maximise muscle gain from training.
Recent studies have shown that leucine interacts and activates the mTOR pathway in cells. mTOR stands for ‘mammalian target of rapamycin’ and is a pathway, that acts as a cellular nutrient sensor among other roles. High levels of leucine are interpreted as high overall nutrient levels, and as a sign that the environment is good for increased protein synthesis and growth. Leucine activates the mTOR pathway, which in turn activates other proteins like the initiation factors, which have to be activated to start protein synthesis on the ribosomes.
BCAAs also cause the activation of genes which code for ribosomal proteins. Ribosomes are tiny organelles inside cells where protein synthesis occurs. As a result of increased BCAA levels, more ribosomes are made inside cells.
In short, BCAA amino acids, especially Leucine, acting through the mTOR complex, increase the levels of protein synthesis in two ways. They increase the cells’ capacity to synthesis proteins, by increasing the number of ribosomes, and they stimulate translation, by causing the activation of factors that control it. As everybody knows, increased protein synthesis in muscle cells, results in increased muscle gain.
The protein synthesis stimulating property of BCAAs is also of great importance when going on a calorie reduced diet. One of the problems of trying to lose weight is that muscle mass is lost as well as fat. BCAAs will act to preserve muscle when calories are restricted, leading to more fat being burned, and a higher lean muscle to fat ratio.
Improved Endurance and BCAA Supplements
The vast majority of amino acids can only be metabolised in the liver. BCAA amino acids, on the other hand, can be metabolised directly for energy in muscle cells. Loading up muscles with BCAA before exercise, was shown in scientific studies, to improve performance and endurance. This is presumably because, they increase the amount of fuel immediately available to cells, which can be turned into ATP, which in turn provides energy for muscle contractions. It is a well known fact that BCAAs are severely depleted during exercise. Presumably this happens because they are used up as fuel.
Branched chain amino acids can also lesson the mental perception of fatigue. We all know that how you feel in your mind is at least as important as your physical state. BCAAs achieve this because they compete with transport across the blood
-brain barrier with tryptophan. Since tryptophan is a precursor of the neurotransmitter serotonin, high levels of BCAAs might result in less serotonin being produced and a lower perception of fatigue, which translates into better endurance during exercise.
Increased testosterone and decreased cortisol
Clinical studies have shown that BCAA supplementation has a positive effect on the hormone balance in the body. Specifically BCAA appear to increase the levels of testosterone, while also decreasing the levels of cortisol.
This is the ideal outcome for people trying to gain muscle mass and lose weight. Testosterone is an anabolic hormone, it stimulates protein synthesis and muscle gain. Cortisol, on the other hand, is a catabolic hormone. It is the body’s main response to stress, and one of its main functions is to increase the levels of available glucose in the blood. It achieves this by flooding the system with free amino acids, produced by breaking down muscle protein. The free amino acids are then converted to glucose in the liver.
Although cortisol plays an important part in allowing people to survive immediate physical danger, its effects are detrimental in the long term. An increased level of testosterone and a decreased level of cortisol leads to the effects most people seek, an increase in muscle mass at the expense of fat storage.
BCAAs Increase Insulin Release
Recently studies have generated much excitement about the potential use of BCAAs in the treatment of type II diabetes or metabolic symptom. Both of these conditions are characterised by insulin resistance, which leads to a disruption of the essential blood glycaemic balance. Controlling the levels of glucose in the blood, one of the main functions of insulin, is crucial to good health. Insulin affects not only carbohydrate metabolism, but also protein and lipid metabolism. Many studies have shown that branched chain amino acids, especially leucine, cause insulin to be released from the pancreas. BCAAs have been repeatedly shown to have a stabilising effect on the levels of glucose in blood.
Although leucine seems to play an especially important role in mediating the health benefits of BCAA, taking leucine in isolation is not the most effective way of supplementing branched chain amino acids. Research has shown that isoleucine and valine also play important roles and that the most effective supplements have a 2:1:1 ratio of leucine to the other BCAA.
In summary BCAAs have many health benefits in addition to simply being the building blocks of proteins. These essential amino acids are important for athletes and body builders because of their roles in stimulating protein synthesis and muscle gain, and their ability to enhance endurance during training. However BCAAs are also of importance to people aiming to reduce their weight, since they will help preserve lean muscle on a calorie reduced diet, will help keep blood sugar levels constant, and produce a beneficial balance in anabolic versus catabolic hormones.