Branched-Chain Amino Acids: What Is Their Function?

Depending on your needs and physical requirements, including branched-chain amino acids may be a great option for you. See why.
Branched-Chain Amino Acids: What Is Their Function?
Maria Patricia Pinero Corredor

Written and verified by the nutritionist Maria Patricia Pinero Corredor.

Last update: 16 June, 2022

Amino acids are the links that form part of proteins – macronutrients that form tissues and compounds for the correct functioning of the body. There are 20 amino acids, between essential and non-essential, but only 3 of them are known as branched-chain amino acids.

Valine, leucine, and isoleucine make up the trio of essential amino acids that have a branched side chain, formed by a carbon atom and 3 hydrogens.

Among their functions are that of building muscle mass and improving physical performance. For this reason, they’re in great demand by athletes. In addition, they’re part of the treatment of some diseases that we’ll see later.

What are amino acids?

In general, amino acids are the basic components of proteins. Without them, the different protein structures of the body can’t be formed. For example, they modulate the production of the hormones, enzymes, and antibodies essential for life.

As we said earlier, there are 20 amino acids in total, and they divide into 9 essential and 11 non-essential.

The essential ones must be supplied by the diet because the body lacks the mechanisms to manufacture them. The non-essential ones are produced in the body itself, although they’re also found in food.

So, from a nutritional point of view, a complete protein, ready to fulfill its function, contains the essential and non-essential amino acids. In addition, it must be accompanied by the energy required by the body through carbohydrates and fats.

What are branched-chain amino acids?

Of the 9 essential amino acids, 3 have a different spatial structure from the rest. Valine, leucine and isoleucine aren’t linear, but have chains on the sides, which is why they’re known as branched-chain amino acids.

When absorbed, they go directly into the blood without passing through the liver. Therefore, by ingesting enough good-quality proteins or supplements of these amino acids, they increase rapidly in the blood. From here they reach the muscles to be used by specific enzymes.

Muscle represents up to 40% of a person’s total weight. It is, therefore, the tissue in which the branched-chain trio exerts its greatest action. They’re involved in muscle recovery and growth.

They’re also known as BCAAs and are consumed by the population seeking a number of physiological and metabolic effects. In theory, branched chain amino acids don’t only build muscle, but also participate in energy metabolism.

A muscular body.
The incorporation of branched-chain amino acids is widely studied in sports science to increase muscle mass faster.

Functions of branched chain amino acids

Branched-chain amino acids have a number of functions for athletes and for the benefit of general health. We discuss them below.

They can be a source of energy

Although this isn’t the main role of amino acids, in long-duration sports, carbohydrates and fats represent the main source of energy. However, in muscle, 1 to 6% of the total energy can be oxidized directly through branched amino acids.

For its part, the Spanish Journal of Human Nutrition and Dietetics tells us that BCAAs act as a substrate to increase the intermediate compounds involved in energy metabolism. The increase in their oxidation to produce energy will depend on the intensity, the person’s diet, the consumption of glycogen in the muscle, and the duration of the sports event.

They favor muscle growth

During the recovery processes of long-lasting sports, BCAAs have anabolic effects on human muscle. Some studies also show that leucine is the amino acid responsible for increasing protein synthesis after exercise.

The muscle synthesis effect of BCAAs may be due to their positive impact on growth hormones, as they provide the necessary amino acids that promote protein synthesis. It should also be noted that muscle growth occurs with the consumption of branched amino acids along with the rest of the essential and non-essential amino acids.

They decrease fatigue

So far, supplementation with branched amino acids has been shown to significantly reduce the production of serotonin, which is responsible for fatigue during exercise. In addition, some experts also report that BAACs may act as a neurotransmitter.

In a trial with runners supplemented with BAACs and a drink rich in these amino acids, just after training, it was found that fatigue decreased significantly after 120 minutes. However, the results with short-duration exercise haven’t yet brought a consensus.

They improve sports performance

A study showed that a long-term intake of BCAAs can be effective in improving the athlete’s ability in long-duration exercise, such as cycling, running, or triathlons.

Less muscle and mental fatigue, and faster recovery, have also been observed when supplemented with BCAAs. However, if used alone and not in a trio, there are no positive effects.

May relieve symptoms of liver disease

Valine, leucine, and isoleucine produce glutamate, a compound that detoxifies ammonium released during liver cirrhosis. Supplementation with BCAAs has also been found to decrease the symptoms of progressive liver failure.

Furthermore, clinical studies show that they reduce the complications of cirrhosis and malnutrition. In addition, an increase in muscle mass and a decrease in fat tissue were obtained in patients.

They could improve neuropathy

The glutamate formed from BCAAs functions as an important excitatory neurotransmitter in the brain. Tests in mice have corroborated neurological abnormalities when BCAA levels are very low. When supplemented with these amino acids, a significant improvement in neurological damage was observed in the animals.

Where can branched-chain amino acids be obtained from?

Since they’re part of proteins, branched-chain amino acids are found in foods with a high protein content. Among these are those of animal origin, such as the following:

  • Meat and meat by-products.
  • White and bluefish.
  • Milk and dairy products.
  • Eggs and egg products.

Other foods of vegetable origin that contain high protein values are the following:

  • Legumes, such as lentils, peas, beans, and chickpeas.
  • Cereals, such as corn, oats, wheat, rice, and barley.
  • Pseudocereals, such as quinoa and amaranth.
  • Nuts, such as hazelnuts, walnuts, and pistachios.

The proportion in which BCAAs are found in different protein foods is high. Therefore, in the traditional omnivorous diet they’re abundant and there are no deficiencies. Likewise, those who practice an ovo-lacto vegetarian diet won’t suffer deficiencies either.

Red meat.
Although their presence in meat is notable, this doesn’t mean that a vegetarian diet lacks BCAAs.

Are supplements effective?

Supplements are another option to consume BCAAs. In this case, you should listen to the recommendations of health professionals, especially in sports nutrition. Everything will depend on your goals and training routines. How much, and how to take them, should also be advised by experts.

When it comes to supplements for the athlete, it’s common to take them at 2 or 3 different times of the day, instead of doing it in a single intake.

A dose before, during, and after training or a competition is suggested for better muscle recovery. If the competition lasts several days, the amount should be spread out to cover all the days.

Excessive intake of these amino acids may cause increased renal work. If it’s maintained for a long time, it could cause alterations in the bones with a greater probability of injuries or fragility.

Of course, for the branched-chain amino acids to fulfill their functions, they have to be in balance with the rest of the nutrients. But, above all, there must be an adequate caloric intake. Otherwise, they won’t build muscle mass, but will be used as an energy source.

There’s currently controversy about the ideal dose of branched-chain amino acids. However, most studies have had good results with daily doses of between 6 and 12 grams.

The ratio between them is 2-3/1/1 in the order leucine, valine and isoleucine. It is recommended that the maximum intake of leucine should be 550 milligrams per kilogram of body weight.

It’s suggested that all studies on BCAAs consider a uniform supplementation protocol to avoid dosages that don’t provide any benefit. Especially for athletes.

Consult with experts

The consumption of branched-chain amino acids, both to improve sports performance and health status, should be indicated and supervised by experts. They’re the ones who will prescribe a balanced and varied diet sufficient to maintain the daily quota of BCAAs or the requirement of supplements.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

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This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.