Isoleucine, along with other BCAAs, is part of many supplements aimed at helping you maximize your physical potential and getting the most out of your workouts. Read on to find out what it is, what it does, and how it makes it all happen.

What Is It?

Isoleucine is one of the BCAAs [1], or branched chain amino acids. There are a total of three BCAAs, all of which play a slightly different role in assisting with the recovery of your muscles after strenuous activity such as a workout or other type of competitive activity.

What Is Its Biological Role?

BCAAs are a particular group of amino acids that have been proven to promote protein synthesis. You see, after periods of physical exertion involving either resistance or endurance (such as a weight-training workouts), we know that part of the muscle building process is minute tears to our muscle fibers.

Essentially, they are injured and begin to break down. However, exercise also tells our body to synthesize more protein to repair and grow large. The problem comes in when, all too frequently, the signals for tearing down muscles are the same as or stronger than the signal to build it.

This situation results in no muscle growth, or worse, increased muscle loss. The best way to stop this is to consume BCAAs after a workout, as it tips the balance of these signals in your favor and promotes increased growth. Out of the three BCAAs, isoleucine helps by increasing your endurance during a workout, enabling the muscles to perform longer while incurring less damage.

The end result is decreased protein breakdown, and increased protein synthesis, which leaves the user with a much more beneficial balance of the two processes. Additionally, isoleucine is known to help user recover more quickly after a workout [2]. This is due in part to the reduction in muscle breakdown, but also due to isoleucine’s ability to help fortify the muscles.

How Does It Help Bodybuilders and People Who Work Out?

This type of supplement is perfectly suited to bodybuilders, or anyone who is embracing resistance training while cutting calories.

One of the things that can make it difficult to boost muscle mass while reducing calories (either as someone looking to lean out or a bodybuilder trying to get as cut as possible before a competition), is that as our body’s store of fat diminish, our metabolism can begin to breakdown our muscles for additional energy.

When you consume BCAAs after a workout, you are steering your body’s reaction in a more beneficial direction [3] but ensuring you do not lose muscle mass. In addition, isoleucine can help reduce recovery time between workouts.

All of these benefits combined means that you can workout longer and harder, with better results, and that you can wait less time between workouts to really maximize your physical potential in terms of how quickly you will be able to see results from all of the gym hours you’re putting in.

What Foods Contain It?

Isoleucine in supplements has been isolated and combined with other BCAAs to give you a concentrated form of these essential amino acids. This form of isoleucine consumption is believed to be the most effective post-workout because it causes an immediate spike in the levels of isoleucine in your blood. However, isoleucine can be found in many foods, including soybeans, cheese, and animal meats.

How Much Of It Do You Need?

There is no officially sanctioned daily requirement of isoleucine, as it is part of the other proteins you eat every day. For supplementation it is generally recommended to consume 5g of BCAAs before a workout and 10g after.

Many BCAA products will include a proprietary blend of all the BCAAs, meaning you cannot be exactly sure how much of any particular BCAA you are consuming. If you are pregnant or breastfeeding, it is advised that you do not supplement with BCAAs as there is not significant research to determine how this will affect the baby.

Are There Risks Associated With Consuming Too Much Of It?

When supplementing with isoleucine, it is very difficult to accumulate so much in the body that you get sick. However, consuming more than 15g at a time can cause gastrointestinal distress such as nausea, vomiting, or diarrhea.

Isoleucine is also considered a glucogenic compound; glucogenic compounds can be converted into glucose as an emergency source of energy for the body. If you have diabetes, supplementing with high amounts of isoleucine may make it difficult to control your blood glucose levels.

Are There Risks Associated With Consuming Too Little Of It?

There are no risks associated with too little supplementation. Any isoleucine you ingest is only going to help you build muscles. However, if you consume a low-protein diet it can be important to supplement with BCAAs to help maintain muscle mass.

Now that you understand exactly how this supplement affects your body and can possibly help you get the most out of your current fitness routine, you can make a more informed decision about whether a BCAA supplement product is right for you.


[1] WebMD. Branched Chain Amino Acids: Uses, Side Effects, Interactions and Warnings., 2015.

[2] Hendrickson, Kirstin. The Function of Isoleucine Amino Acids., 2015.

[3] Norton, Layne. BCAAs: The Many Benefits Of Branched Chain Amino Acid Supplements., 2017.