L-glutamine is an amino acid—one of the building blocks of protein molecules—and is found abundantly in the body. In fact, it is the most common amino acid in the body, existing in the lungs, brain, muscles, and gut. Since the body makes L-glutamine on its own from other amino acids, it is considered “non-essential,” meaning that we don’t need to get it directly from foods. However, under certain conditions, supplements may be useful. For example, L-glutamine is the energy source of white blood cells, so it is an important part of a healthy immune system. When the body is under stress or subject to trauma, it may require L-glutamine in larger amounts to facilitate healing. In fact, studies show that L-glutamine supplements may help to speed healing and recovery after surgery. As fuel for the immune system, L-glutamine may also help the body recover from illness or injury.

L-glutamine plays a host of roles in the body in addition to its role in the immune system. It helps to maintain the important acid-base balance in cells and tissues. L-glutamine is also important for maintaining muscle tissue, making it a useful supplement for athletes and bodybuilders. In addition, L-glutamine helps prevent the breakdown of muscle when a person is under stress. It can also cross the blood-brain barrier. In the brain, L-glutamine is converted to glutamic acid, a substance that is crucial for proper brain function.

Another major benefit of L-glutamine is its ability to maintain the health of the gastrointestinal tract. The lining of the intestines is important not only in digestion but also in defending against germs. The cells that line the small intestine, known as enterocytes, depend on glutamine for energy. Without sufficient glutamine, toxins may be absorbed through the lining of the gut, causing illness. Allergic reactions, skin conditions, and Crohn’s disease are some of the problems that can result when toxins get into the gastrointestinal tract.

L-glutamine also works in the gut to help small structures known as villi absorb nutrients properly. Supplements may help to increase the length of villi so that they can absorb nutrients better. When nutrients are not properly absorbed, a host of symptoms can occur, including the allergic reactions caused by food allergies. Gluten allergies (celiac disease) and other food allergies may become less severe with L-glutamine supplements, which can help support a healthy intestinal lining.

Problems can also occur when the intestines allow too much absorption. The condition known as leaky gut syndrome, or intestinal hyperpermeability, occurs when undigested food particles, toxins, and potentially harmful microorganisms are able to cross into the bloodstream from the intestine. L-glutamine supplements may work to correct this problem by helping to repair the gut.

While L-glutamine can be obtained from many plant and animal foods, it is easily destroyed through cooking, so supplements are often a good idea for people with conditions or situations that may require higher amounts of this important amino acid. The usual recommended dose for people who want to take an L-glutamine supplement is 1,000 mg per day. Supplements are available in tablets, capsules, and powders, which should always be stored in a cool, dry place to prevent L-glutamine from degrading.

—Maria Kuzmiak