What Are Amino Acids?
When consumed, proteins break down into amino acids, the building blocks of proteins. Once broken down, amino acids are used for many functions. These functions include growth and repair of tissues, making enzymes and hormones, supporting immune function, as an energy source, and as base materials in the production of other compounds needed by the body. Branched-Chain Amino Acids, or BCAAs, contain 3 amino acids.
In short, humans need 20 amino acids. Of those 20, only 9 are essential, which means the body cannot produce them. That being said, we consume the essential amino acids through our diet. Proteins that contain all 9 essential amino acids are “complete” proteins, opposed to“incomplete”.
What Are BCAAs?
Branched-Chain Amino Acids (BCAAs) contain 3 of the essential amino acids – leucine, isoleucine, and valine. The liver processes most amino acids for metabolic functions, but muscle building works a little differently. What makes BCAAs unique is that the muscle metabolizes them instead of the liver. Therefore, the amino acids go directly into the bloodstream and to your muscle for energy during exercise.
Having enough Leucine is the key to muscle building. If Leucine levels in your blood are too low, your body just uses Leucine as fuel instead of building muscle. When Leucine blood levels elevate, your body sees there are enough amino acids for muscle building. Your body then uses Leucine to activate Muscle Protein Synthesis and muscle cells which supports muscle building and repair.
Research determined that Leucine is responsible for initiating the muscle recovery process after training. In other words, Leucine helps the body stop breaking down muscle and start to rebuild it. A 2016 study by Moberg et al compared the impact of water, leucine, BCAAs, and all EAAs in resistance-trained men (2). In short, the results found that BCAAs alone or in the full mix of EAAs stimulate repair and recovery better than water or leucine alone.
Similarly, Isoleucine works with Leucine by stimulating the muscle to absorb glucose from the bloodstream, which fuels the muscle building process. Muscle building is crucial to achieving peak performance. Strenuous workouts can lead to tired, sore and damaged muscles and recovery takes time and reduces workout efficiency. That being said, getting enough Leucine and Isoleucine can help speed muscle recovery, allowing you to workout more often with higher intensity.
On the other hand, Valine helps in preventing the breakdown of muscle by supplying muscles with an extra glucose responsible for the energy production during physical activity. In addition, Valine helps mental fatigue by inhibiting the transport of Tryptophan across the blood-brain barrier, and regulating the immune system (1). In other words, Valine is an essential amino acid important for smooth nervous system and cognitive functioning.
BCAAs and Athletes
Although BCAAs are in some foods we eat, many meals do not provide sufficient levels of protein to initiate muscle building. Additionally, when you are following a hard training plan, working to maximize athletic performance, and/or cutting calories, it can be difficult to make sure you get enough BCAAs regularly. That being said, BCAA supplementation ensures your body has enough of these essential amino acids.
BCAAs and Fatigue
There are 2 types of fatigue: peripheral and central, and BCAAs help protect you from both. First, it has been shown that BCAAs increase exercise capacity or time to exhaustion specifically when the glucose stored in the muscle for energy has been depleted (3). Meaning, BCAA supplementation is extremely beneficial for those engaging in prolonged exercise. As previously stated, BCAAs are metabolized in the muscle and can be converted to glucose for energy if needed by the body (4).
Secondly, BCAAs can help reduce central (mental) fatigue. When you are active, your body releases fat to burn. This, in turn, increases the amount of free tryptophan in your body. Tryptophan is the precursor to serotonin, a neurotransmitter that brings on symptoms of central fatigue (7). BCAAs compete with tryptophan. That being said, the more free BCAAs you have, the less fatigue you feel (4).
BCAAs and Muscles
A study by Shimomura et al. showed that taking a mixture of BCAAs before exercise allowed participants to exert the same force 3 days after an intense bout of exercise compared to the control (5). To clarify, all participants were asked to exert maximum muscle force on a leg extension before doing seven sets of twenty squats. One group was given a BCAA mixture before the exercise, while the other group was not. Then, 3 days later, they were asked to do the same test on leg extension.
The BCAA group was able to exert the same force they did before the squats, while the placebo group only exerted around 80% compared to what they did previously. This suggests that BCAAs could help alleviate some of the damage to the muscle and loss of contractile force.
BCAA Absorption Rate
Amino acids have a quicker absorption rate even when compared to casein or whey protein shakes. Studies show that liquid whey protein as a meal spiked amino acid concentration after about 90 minutes while free form amino acids spiked plasma amino acid concentrations in 30 mins, or 3 times as fast as whey protein (5).
In order to be absorbed and utilized, intact, complete proteins need to be digested first. On the other hand, BCAAs are absorbed more quickly and then directed throughout the body to be utilized their specific functions. By utilizing the rapid absorption of BCAAs, you may prevent potential fatigue, or help prevent some of the muscle damage and soreness, all without loading up on extra calories. BCAAs can help jump-start the recovery process even before your training has ended.