L-Glutamine: A Complete Guide To This Gut-Healing Amino Acid

Photo: Susana Ramírez

As an integrative gastroenterologist, one of the most common things I get asked is "How do I heal my gut?" This is my favorite question because it opens the door to allow me to really and truly make an impact on someone's health, which is the reason I became a doctor in the first place.

And while the question about how to optimize gut health is a loaded one—as every patient has a different gut-healing journey—it gives me and my patients an opportunity to work through and figure out their health problems and develop a personalized plan of action. There are a variety of approaches for evaluation and management of gut health that can be taken depending on the particular situation.

I often suggest a variety of herbals and supplements to help aid in the process of boosting the immune system and healing leaky gut and other gut issues. Oftentimes, L-glutamine is one of the major supplements that comes up. This common supplement is becoming more popular every day and is found in many leaky gut and gut-healing formulations. So let's talk about L-glutamine supplements and their benefits and side effects.

L-glutamine powders and supplements.

L-glutamine is an amino acid, and amino acids are the building blocks of protein, which all of our bodies need to function. As you probably already know, our cells and muscles need protein to carry out their functions as well. L-glutamine supplements are becoming more popular by the day. They are mostly found in a powder form that you add to a glass of water or smoothie, but L-glutamine can also be ingested by way of a few supplement capsules.

L-glutamine has a wide variety of functions (many of which we'll learn about later in this article), but one of the most exciting is its ability to help with leaky gut. A recent article explained that glutamine is one of the most commonly found amino acids in the blood and cells and is a preferred source of energy for the cells of the small bowel and other immune cells. The authors also explained that glutamine supplementation can protect the lining of the bowel and help it keep a strong intestinal barrier, in addition to reducing intestinal permeability (i.e., leaky gut), enhancing immune cell function, and boosting the immune system while reducing the inflammatory response. Another study from 2017 showed that giving a glutamine supplement to athletes who compete in the heat could reduce leaky gut, and it may be beneficial to consider supplementation before exercising in order to support gut health.

L-glutamine benefits.

As I mentioned before, L-glutamine has many benefits. One study showed that taking a glutamine supplement resulted in decreased muscle soreness after eccentric exercise, and this amino acid also can be used in those getting treatment for head and neck cancer because it reduces the incidence of getting inflammation in the mouth and painful swallowing. This allows treatment to continue without added interruptions. In this setting, the glutamine supplement is providing a protective coating to the mouth and esophagus and boosting the healing capacity of the cells. L-glutamine has also shown promise for other conditions, such as:

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1. L-glutamine for fatty liver disease.

Fatty liver is one of the most common conditions I see in my office as an integrative gastroenterologist; this is largely due to lifestyle and dietary patterns that most people follow. One of the leading causes of liver disease and need for liver transplantation in this country is fatty liver and nonalcoholic steatohepatitis, also known as NASH. People with this condition may also have blood sugar problems, heart disease, metabolic syndrome, and/or obesity. Data from a recent study demonstrated that taking a glutamine supplement protected mice from the progression of liver disease from NASH, and prior literature suggested that glutamine could help prevent the development of NASH altogether.

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2. L-glutamine for the immune system.

Another interesting study showed that mice who were given glutamine got an immune system boost and had reduced rates of reactivation of herpes infection. This research further supports that glutamine may play a role in contributing to a more robust immune system. Along these lines, a review of the literature on glutamine suggested that supplementation reduced the rate of hospital-acquired infections, shortened length of hospital stay, and reduced the rate of in-patient mortality. We should note, however, that many of these studies suggested associations and did not reach statistical significance. Nonetheless, this is still an interesting observation.

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3. L-glutamine for inflammatory bowel disease.

One of the settings in which glutamine supplements are used the most is with inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease. These are conditions that can present with ulcers in the digestive tract as a result of an autoimmune attack to the bowel. It may not be unreasonable to use L-glutamine in this setting because there is some data to suggest that it could block activation of the pro-inflammatory mediators NF-kB (nuclear factor kB) and STAT (signal transducer and activator of transcription) and thereby reduce the expression of inflammatory cytokines, which are implicated in contributing to inflammation in this setting.

In my practice, I find that L-glutamine can be useful in reducing symptoms of diarrhea and can help reduce inflammation and ulcers. The same article also looked at other studies and suggested that glutamine supplementation in general seems to help regulate the growth of intestinal cells, maintain the gut's tight junctions, influence inflammatory cascades, and protect against cell death and stresses, among other functions.

Indeed, L-glutamine is an important amino acid when it comes to gut health! This has much greater implications than just inflammation in the gut and inflammatory bowel disease. We know that over 70 percent of our immune system is in the gut. Therefore, autoimmune conditions—such as Hashimoto's thyroiditis, fibromyalgia, and many others—could potentially be influenced by glutamine supplementation. Certainly, further studies are needed to examine each of these conditions individually to prove or disprove this hypothesis. However, there seems to be good evidence that glutamine supplementation can play a role in reducing leaky gut, which is an underlying process that drives many immune and autoimmune conditions.

L-glutamine side effects and safety concerns.

I should mention that, while there seems to be strong data for the use of L-glutamine in many different situations, there is also a large body of conflicting research as well. That is why it's important to consult with an integrative-medicine- or functional-medicine-certified practitioner to discuss whether or not it may be a good idea for you to take this important amino acid as a supplement. The other thing to consider would be potential side effects and drug interactions. Generally speaking, L-glutamine is well-tolerated. Some studies that used particular preparations of glutamine were associated with some adverse effects, including swelling of the extremities, gastrointestinal symptoms (such as constipation), headache, fever, and infections.

As far as interactions are concerned, there is some suggestion that glutamine can reduce the ammonia-lowering effect of lactulose, so in those that have liver cirrhosis and hepatic encephalopathy, this may not be the best choice of supplement. Additionally, glutamine could increase tumor retention of methotrexate and increase its efficacy as a therapy, but this is something that should only be done in coordination with a trained cancer specialist.

L-glutamine is an important amino acid that is essential to our gut and immune health and integrity. It can potentially help with a wide variety of dysfunctions from irritable bowel syndrome with diarrhea to inflammatory bowel disease to supporting your blood sugar regulation, metabolism, liver function, and detoxification capacities. It is often found in formulations that are designed to help treat leaky gut. So it's certainly worth talking to your health care provider about as you go through your gut-healing journey!

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