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A Complete Guide To L-Glutamine, From A Functional MD

Marvin Singh, M.D.
Updated on March 1, 2021
Marvin Singh, M.D.
Integrative Gastroenterologist
By Marvin Singh, M.D.
Integrative Gastroenterologist
Marvin Singh, M.D. is an integrative gastroenterologist in San Diego, California. He is trained and board certified in internal medicine and gastroenterology/hepatology.
March 1, 2021

As an integrative gastroenterologist, one of the most common questions I'm asked is: how do I support my gut?

While the question is a loaded one, it's also one of my favorite questions to answer. In fact, it's the reason I became a doctor in the first place—it opens the door for me to make a real and lasting impact on a patient's health. There are a variety of approaches for evaluation and management of gut health that can be taken depending on the particular person and their situation.

One approach I suggest for most patients is taking a variety of immune-supporting herbs and supplements, including L-glutamine. Here are the main benefits and side effects of L-glutamine, in case you're curious.

L-glutamine powders and supplements.

Glutamine is an amino acid1, aka a building block of protein. Protein is essential nutrient, necessary for the cells and muscles to carry out their functions.

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 supplement capsules.

According to a study published in the International Journal of Molecular Science, glutamine is one of the most common amino acids in the blood and cells, and it's a preferred source of energy for intestinal cells2. The authors also explain 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 supporting the immune system while reducing the inflammatory response3.

Another study from 2017 showed that giving a glutamine supplement to athletes4 who compete in the heat could reduce intestinal permeability, which indicates to me that it may be beneficial to consider supplementation before exercising in extreme conditions, in order to support gut health.

L-glutamine benefits.

As I mentioned before, L-glutamine has many reported benefits. One study suggested that taking a glutamine supplement may result in decreased muscle soreness after eccentric exercise5.

The amino acid can also be used by patients receiving treatment for head and neck cancer since it may reduce the incidence of painful swallowing and inflammation of the mouth.6 In this setting, the glutamine supplement is providing a protective coating to the mouth and esophagus.

L-glutamine has also shown promise for other conditions and bodily functions, such as:


Fatty liver disease

Fatty liver is one of the most common conditions I see in my patients, and it's largely due to lifestyle and dietary patterns.

One of the leading causes of liver disease, and the need for liver transplantation, in the U.S. is fatty liver and non-alcoholic steatohepatitis (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 mice who took a glutamine supplement were protected from developing NASH. 7Prior literature suggests glutamine could help prevent the development of NASH altogether8, but more research is needed to substantiate these findings.


Immune support

Another study published in the Journal of Clinical Investigation found mice who were given glutamine9 saw an increase in their immune response, and were less likely to experience reactivation of herpes infection. This research further supports the idea that glutamine can play a role in supporting the immune system.

Along these lines, a review of the literature on glutamine10 suggests that supplementing with this amino acid 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.


Inflammatory bowel disease (IBD)

Glutamine supplements are most frequently used to help with inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease. These conditions can cause painful ulcers in the digestive tract in response to an autoimmune attack to the bowel.

The International Journal of Molecular Science study from before suggests that L-glutamine could block the activation of two pro-inflammatory mediators, and thereby reduce the expression of inflammatory cytokines. In other words, it may help reduce inflammation.

The same article reviewed other studies and suggested that glutamine supplementation, in general, seems to help regulate the growth of intestinal cells, maintain the gut's tight junctions11, influence inflammatory cascades, and protect against cell death and stresses.

While L-glutamine is an important amino acid when it comes to gut health2, those benefits have greater implications. More than 70% of our immune system lives in the gut. Therefore, autoimmune conditions (Hashimoto's thyroiditis, fibromyalgia, and many others) could potentially be influenced by glutamine supplementation.

Further studies are needed to examine each of these conditions individually, to prove or disprove this hypothesis.

L-glutamine side effects and safety concerns.

While there seems to be strong data for the use of L-glutamine, there is also a large body of conflicting research. That's why it's important to consult with your primary care physician or integrative medicine doctor before adding the amino acid onto your supplement routine. Here are a few noted side effects:

  • Some studies, using particular preparations of glutamine, were associated with adverse effects, including swelling of the extremities, headache, fever, infections, and gastrointestinal symptoms like constipation.
  • As far as drug interactions are concerned, some suggest that glutamine can reduce the ammonia-lowering effect of lactulose. Meaning, those with liver cirrhosis and hepatic encephalopathy should consult a doctor before taking L-glutamine and may want to avoid it altogether.

Bottom Line

Glutamine is an important amino acid that is essential to our gut and immune health. Taking L-glutamine as a supplement can potentially help with a wide variety of issues, from irritable bowel syndrome with diarrhea, to inflammatory bowel disease, and more. If you experience any of these conditions, it's certainly worth talking to your healthcare provider about.

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Marvin Singh, M.D. author page.
Marvin Singh, M.D.
Integrative Gastroenterologist

Marvin Singh, M.D is an Integrative Gastroenterologist in San Diego, California, and a Member of the Board and Diplomate of the American Board of Integrative Medicine. He is also trained and board certified in Internal Medicine and Gastroenterology/Hepatology. A graduate of Virginia Commonwealth University School of Medicine, Singh completed his residency training in Internal Medicine at the University of Michigan Health System followed by fellowship training in Gastroenterology at Scripps Clinic Torrey Pines. Singh was trained by Andrew Weil, M.D., a pioneer in the field of integrative medicine, at the Andrew Weil Center for Integrative Medicine.

Singh is currently the Director of Integrative Gastroenterology at the Susan Samueli Integrative Health Institute at UC Irvine. He is also currently a voluntary Assistant Clinical Professor at UCSD in the Department of Family Medicine and Public Health; prior to this, he has been a Clinical Assistant Professor at UCLA and an Assistant Professor of Medicine at Johns Hopkins University. Singh is a member of the American Academy of Anti-Aging Medicine, American College of Lifestyle Medicine, and many other societies. He is actively involved in the American Gastroenterological Association. He is one of the editors of the textbook of Integrative Gastroenterology, 2nd edition (a Weil Series text) and has written several book chapters and articles.

He is dedicated to guiding his clients toward optimal wellness every step of the way, using the most cutting edge technologies to design highly personalized precision based protocols. Towards this end, he founded Precisione Clinic and wrote the book Rescue Your Health to bring the best in preventive medicine to his clients.