The human body has evolved to survive. It can function for weeks after our last meal using its own energy stores. Our primary energy store is our adipose (a.k.a. fat) tissue. Accumulation of fat is the most efficient way of „saving energy for later” that our body has. Our next big energy source is stored carbohydrates in the form of glycogen. Though carrying a lot less calories, glycogen still contains a lot of energy. We have a far less evident nutrient deposit as well – our muscles, which are our biggest amino acid stock. Our body uses amino acids as an energy source only under extreme circumstances, like ultra-marathons, and a very lowlcarb, very low-fat diet.
In our muscle tissue, a constant remodelling of the contractile proteins takes place. If the breakdown and the synthesis is in balance, the net change of muscle protein is zero.
Our body needs a continuous supply of amino acids for many other processes and chemical reactions. Because of that, even at rest, there is a certain amount of amino acids that we need. If we do not supply it, our body will reach for the stored version – muscle tissue. It is crucial to supply our body with a constant stream of amino acids through our gut, to avoid muscle tissue and contractile protein breakdown.
A continuous flow of amino acids can be achieved with different types and sources of protein. Some are fast absorbing (whey), some are slow (casein).
Multiple studies show, that proper amino acid supply around your workouts is key for muscle building. High concentration of amino acids in the blood not only stops catabolic processes, but increases the body’s sensitivity to stimulation of muscle protein synthesis, meaning, you will get a bigger response for you post-workout shake, if you had enough amino acid in the blood pre/intra-workout.
For the sake of comfort, we want to have an intra-workout amino acid source, that does not sit in our stomach too long and doesn’t get us bloated. We need all the blood for the exercise, can’t afford sparing some of it for digestion. In situations like this, BCAA supplements come in handy. Branched chain amino acids (a.k.a. BCAAs) are 3 essentail amino acids: leucine, isoleucine and valine.
What effect do BCAAs have?
In our muscles, there is a continuous breakdown and synthesis of proteins. The balance between breakdown and synthesis defines the net change in muscle protein content. Consuming protein increases amino acid concentration in the blood, which triggers muscle protein synthesis (and inhibits muscle protein breakdown). The type of amino acids entering the circulation does matter – most important are the essential amino acids, especially BCAAs, especially leucine. These are the ones responsible for the „build more protein” signal.
Consuming BCAAs increases muscle protein synthesis. Besides, BCAAs consumed before or during the workout can increase treshold of fatigue and elevate fatty acid oxidation.
• Leucine: the most important amino acid in building muscle. It can activate a regulatory protein called mTOR, which is the main switch for muscle protein synthesis. These effects of leucine are independent of other growth factors like insulin, mechanical stress, etc.
• Isoleucine: it’s a lot less potent activator of muscle protein synthesis, but has a profound effect of muscle glucose metabolism. Isoleucine can increase glucose uptake by muscle cells and glucose utilization – independent of training or other factors.
• Valine: has a small effect on muscle protein synthesis, but can be converted to one of the elements in the citric acid cycle, and thus help fatty acid oxidation and protect glycogen stores.
Summary: BCAA supplementation can help muscle retention and muscle building, can increase fatty acid oxidation and decreases fatigue. Under circumstances where we need a fast supply of amino acids, BCAAs can serve us pretty well.