September 29, 2023

Triggering Muscle Growth with Branched-Chain Amino Acids

Author: Kate Findley
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By Michael Ormsbee, Ph.D.Florida State University
Edited by Kate Findley, The Great Courses Daily

We know that protein and exercise go hand in hand, but what proteins should you specifically eat before a workout? Dr. Ormsbee explains the best type of protein for muscle recovery and even muscle growth.

Close up of someone eating yogurt with nuts and granola
The best type of protein for muscle recovery after exercise and for fuel during extensive exercise contain branched-chain amino acids. Photo by goodmoments / Shutterstock

Branched-Chain Amino Acids

Proteins are made of chains of 20 amino acids. Nine of these amino acids are considered essential, which means that our body does not produce them on its own, and thus we need to include them in our diet. Of the nine essential amino acids, three—called branched-chain amino acids—are particularly notable.

Branched-chain amino acids can provide some fuel during long bouts of exercise or when we go long periods of time between meals. They may also help improve body composition.

The three branched-chain amino acids are leucine, isoleucine, and valine. As the name implies, these amino acids have a branched side chain that distinguishes them from the other amino acids. 

Workout Recovery

If you work out, consuming branched-chain amino acids may be beneficial in preventing muscle damage and helping repair damaged muscle tissue. One study investigated the effect of eating foods containing branched-chain amino acids 60 minutes before a 90-minute aerobic exercise session at moderate intensity. These researchers wanted to see whether these foods had any impact on muscle damage after exercise.

What they found was that the biological markers of muscle damage and muscle soreness were lower when branched-chain amino acids were eaten before exercise compared to a placebo group that took no amino acids before exercise. This means that you may be less sore and uncomfortable after moderate to strenuous exercise if protein is consumed beforehand. 

Foods such as milk, yogurt, or protein shakes could do the trick. With regard to body composition, of the three—leucine, isoleucine, and valine—leucine gets the most attention. This is because leucine is considered to be the trigger to start muscle protein synthesis.

In fact, research suggests that you not only want to eat some protein at each meal, but you might also want to make sure that you’re getting roughly two to three grams of leucine in the protein foods that you choose to eat. 

This is pretty easy to do. Most lean meats eaten in a normal, palm-sized portion will provide 2.5 to 4.5 grams of leucine. You can also get about ½ to 1 gram of leucine by drinking one cup of cow’s milk. 

Additionally, eating beans or nuts will provide around two to three grams of leucine per cup. Thus, before a workout, you might think about a snack of milk, yogurt, beans, and nuts, or a protein shake.

Over the past five to 10 years, there’s been a sharp increase in scientific papers that support using protein or amino acids to prevent the loss of muscle as a result of aging or extreme exercise like marathon running, long-distance triathlons, or even ultra-distance events.

The scientific literature has repeatedly shown that a higher protein diet helps with fat loss and improves body composition. You may be wondering, though, how protein does all of these positive things in our bodies, and how can you use it to improve your body composition.

Energy and Amino Acids

Some amino acids, like the branched-chain amino acids and alanine, among others, can be used to make adenosine triphosphate (ATP) in your energy systems. In this way, it is estimated that protein contributes as much as 10 to 15 percent of your energy supply during intense prolonged exercise. 

A common way to use amino acids for energy is to convert them to glucose in a process called the glucose-alanine cycle. This is one way to produce new glucose from non-carbohydrate sources, which is known as gluconeogenesis. 

This is how the amino acid alanine contributes to energy production. Research shows that the more oxygen a person consumes, like when breathing heavily from exercise, the greater the amount of leucine she or he uses as a fuel source.

Thus, in the process of eating protein, using it to make other proteins, and using protein for energy, proteins are constantly being broken down or metabolized and built back up or synthesized. This process is called protein turnover. The turnover process is never-ending, which is why we must eat a good amount of protein in our diets, particularly when we exercise a lot. 

This article was edited by Kate Findley, Writer for The Great Courses Daily.
Dr. Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University.

Dr. Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his M.S. in Exercise Physiology from South Dakota State University and his Ph.D. in Bioenergetics from East Carolina University.

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