
You need protein for almost every function and structure of your body. Human proteins are all made of twenty amino acids. The amino acids that can't be made in your body must be in your diet and are called essential amino acids. Three of the nine essential amino acids are called the branched-chain amino acids (BCAAs). The three BCAAs are valine, leucine, and isoleucine, which have some important body functions. They're believed to be especially valuable in building muscle.
What are BCAAs?
Proteins are vital to making and repairing tissues like bone, muscles, and skin. The enzymes that run all metabolic processes of your body are proteins. Hemoglobin, another protein, transports oxygen to every cell. Movement and work depend on contractile proteins in the muscles
Human proteins are made of twenty amino acids. Nine can't be made in the body and must be consumed in food. These are called essential amino acids. The BCAAs are three essential amino acids — leucine, isoleucine, and valine.
Protein you eat is broken down in the intestines into amino acids. These are absorbed into the blood and reach the liver, where almost all amino acids are metabolized. But BCAAs quickly reach tissues like muscle and the brain. This is an advantage of protein meals or supplements containing these amino acids.
What do BCAAs do?
Branched-chain amino acids have several actions in the body:
Increase protein synthesis
BCAAs are metabolized in tissues and used to form proteins.They are rapidly available to tissues for their needs after absorption. Muscles have the enzyme branched-chain-amino-acid aminotransferase (BCAT), which enables them to use these amino acids.
Leucine, one of the BCAAs, is believed to control the pathways in the cells involved in making protein.
Reduce protein destruction
These amino acids are not only used to make muscle proteins but also stimulate their formation. During illness or stress, BCAAs reduce the activity of the pathway that breaks down protein for energy. This action preserves protein at the expense of other substrates like fat and carbohydrates.
Energy production when under stress or during illness
Like other amino acids and proteins, BCAAs can be metabolized to generate energy under difficult situations.
Modulate neurotransmission
BCAAs can increase brain chemicals that improve the brain's function and behavior. BCAAs have been tried to treat the encephalopathy (brain disorder) that accompanies liver cirrhosis. However, supplements with BCAAs can also reduce the production of serotonin, which is responsible for fatigue during exercise. However, the reduction of serotonin also cancels out the benefits of serotonin on mood and health.
Control glucose metabolism
The BCAAs have variable effects on glucose metabolism, insulin levels, and response. They're known to increase insulin secretion, but excessive intake leads to prevention of insulin release. They can improve glucose uptake by cells but sometimes cause insulin resistance.
Other effects
- Reduce appetite
- Reduce adiposity (fat deposition)
- Improve mammary health and milk quality
- Intestinal development
- Enhanced immune response
- Better response to oxidative stress

QUESTION
According to the USDA, there is no difference between a “portion” and a “serving.” See AnswerMedical use of BCAAs
The many actions of BCAAs in the body make them likely to be effective in treating some diseases. They prevent muscle loss in bedridden people because of their protein anabolic effect. They are investigated for their role in diabetes, liver cirrhosis, heart failure, and cancer. As yet, evidence for their use in any condition is not enough.
Do BCAAs help your workout program?
BCAAs have several benefits if you are exercising. Consuming BCAAs soon after exercise is probably beneficial. They reach the muscles rapidly after you consume them and can help build muscle. BCAAs also help in fatigue recovery and reduction of exercise-induced muscle damage.
Sources of BCAAs
Most foods of animal origin like eggs, fish, and meat have complete proteins. These proteins provide all the essential amino acids, including isoleucine, leucine, and valine (the BCAAs). Soy protein also contains all the essential amino acids. Vegetarian and vegan diets can provide BCAAs and other essential amino acids if you eat a mix of proteins from different plant sources.
If you are looking for a supplement, whey protein is also a complete protein. BCAAs supplements are also available. These are marketed for stimulating protein synthesis and improving mental focus.
Should you take BCAAs every day?
BCAAs are essential amino acids and should be in your food daily. Without essential amino acids, your body can't keep cellular systems running well. This applies to all the nine essential amino acids.
Can you build muscle by selectively eating BCAAs? Building muscle demands adequate amounts of all the essential amino acids. Muscle protein synthesis will stop if any of the nine essential amino acids are in short supply. To build muscle mass, you must consume proteins with all the essential amino acids. Replacing complete protein with a supplement only providing the BCAAs will be harmful. If you only consume three essential amino acids, the body will break down muscle protein to release the other essential amino acids needed.
What's the Final Takeaway?
Branched-chain amino acids (BCAAs) are three essential amino acids. Their metabolic advantage is that they reach high blood levels soon after consuming them. But they can be used for protein synthesis and muscle building only if all the essential amino acids are also available. You must consume BCAAs daily but as part of your food or a supplement that provides adequate amounts of all amino acids.
Journal of the Academy of Nutrition and Dietetics: "Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids."
Journal of the International Society of Sports Nutrition: "Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?"
Lopez, M.J., Mohiuddin, S.S. Statpearls, "Biochemistry, Essential Amino Acids." Statpearls publishing, 2022.
Nutrition and Metabolism: "Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements."
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