As with some other chronic digestive conditions, there isn’t a cure for irritable bowel syndrome (IBS). This functional gastrointestinal disorder, also known as a disorder of gut-brain interaction, affects both the small and large intestines. It can trigger symptoms such as abdominal pain, bloating, constipation, and diarrhea.Still, there are many ways you can manage IBS pain and other symptoms. These strategies include following a low-FODMAP diet to help identify food triggers, doing cognitive behavioral therapy (CBT), and making lifestyle changes, like getting enough quality sleep each night. Another approach that may help ease symptoms for certain types of IBS? Taking L-glutamine supplements.
Gastroenterologists and registered dietitians say the current research on L-glutamine for IBS shows promise. Here’s what to know about this amino acid, including who may benefit most.
What Is L-Glutamine?
“L-glutamine is the most abundant amino acid in the body,” says Michael Bass, MD, a gastroenterologist, hepatologist, and founding medical director at Oshi Health, based in Philadelphia. When you eat protein-rich foods, your body breaks the protein down into the amino acids that it’s built from. Your body then uses these molecules to repair tissues, including the gut lining, and support a wide range of essential bodily functions.“The gut uses a ton of L-glutamine as fuel for enterocytes, or the cells that line your intestine, and it supports gut barrier integrity and immune function,” Dr. Bass says. This is especially important because 70 to 80 percent of the body’s immune cells live in the gut and rely on L-glutamine (also called glutamine) and other amino acids to function.Bass says that interest in L-glutamine has grown because some research has suggested that it may help tighten the “leakier” intestinal barrier seen in some people with IBS — especially in those who develop diarrhea-predominant IBS after food poisoning or another kind of bacterial gut infection. “This could translate to fewer loose stools and less urgency,” he says.Your body makes L-glutamine, although it produces insufficient amounts as you age. You can also get L-glutamine through your diet, or take it as a supplement. According to Bass, these foods are rich in the amino acid:
Poultry, including chicken and turkey
Beef
Fish
Eggs
Dairy
Beans and legumes
Soy products like tofu
Grains, like rice and oats
Vegetables like red cabbage, spinach, and parsley
For most people, getting L-glutamine through diet alone is sufficient, says Alyssa Simpson, RDN, who specializes in digestive health and is the owner of Nutrition Resolution in Phoenix. But if you’re working on gut repair, research suggests that taking a short-term supplement may help.
L-Glutamine for IBS: What Research Shows
Although more large-scale research is needed, early studies suggest that consuming L-glutamine may help ease symptoms in certain types of IBS and strengthen the gut’s resilience. The amino acid may benefit IBS in the following ways.
Symptom Relief in IBS-D and Post-Infectious IBS
In diarrhea-predominant IBS (IBS-D) and post-infectious IBS, one small, randomized controlled trial of 54 people taking 5 grams (g) of L-glutamine three times a day for eight weeks found that it decreased intestinal permeability and improved stool consistency and overall symptoms. Although the study looked specifically at people who developed post-infectious IBS after a viral, bacterial, or parasitic infection, the findings may also be relevant for those with IBS-D, who experience similarly loose and frequent stools, Simpson says.
Reduced Intestinal Permeability
People with IBS often have a different balance of gut bacteria than those without the condition. That may make them more prone to gut barrier dysfunction, which is sometimes referred to as “leaky gut” or increased intestinal permeability.One review of research on 216 people with inflammatory bowel diseases — conditions that are also connected to increased intestinal permeability — found that taking more than 30 g of L-glutamine per day for up to two weeks significantly reduced intestinal permeability. That means the gut lining became less likely to let unwanted substances such as partially digested food, toxins, and bacteria pass through.While these results are promising, more studies are needed, including trials on people with IBS, to confirm the findings. Improving intestinal permeability could be a way to reduce IBS symptoms in some people, other research suggests.
“This shows that L-glutamine could be a helpful tool for improving gut health in the right situations,” Simpson says.
Enhanced Effects of IBS-Friendly Dietary Changes
L-glutamine may also offer added support when paired with diet-based IBS therapies. In a small, randomized controlled trial, 22 participants who took 5 g of L-glutamine three times daily in addition to following a low-FODMAP diet for six weeks had a significant reduction in overall IBS symptoms compared with those who just followed the diet and didn’t take the supplement.
“This suggests glutamine could be an easy way to get even more out of a low FODMAP approach,” Simpson says. More large-scale research is needed to confirm these results, though.
Should You Try L-Glutamine for IBS?
Bass and Simpson agree there’s reasonable evidence that taking L-glutamine may help ease symptoms of IBS-D or post-infectious IBS. But Bass says there isn’t enough research to show similar benefits for IBS-C — when more than a quarter of stools are hard or lumpy — or for IBS-M, which involves a mix of loose and hard stools.As far as side effects go, “L-glutamine is usually well tolerated, but start with low doses so you can ease into it to avoid any potential bloating,” Simpson says. Bass suggests starting with 5 g of L-glutamine up to three times a day for six to eight weeks.However, Bass says those with advanced liver disease or cirrhosis should steer clear of the supplement unless they get approval from their hepatologist. Taking large amounts of L-glutamine can increase ammonia levels in the body, because L-glutamine breaks down into ammonia, Bass says. In people with advanced liver disease or cirrhosis, that extra ammonia can build up and become dangerous, potentially leading to confusion and mood changes caused by a condition called hepatic encephalopathy.
The bottom line is this: If you find that taking an L-glutamine supplement works for you, then stick to it. If you find that other IBS strategies help keep symptoms at bay, then you probably don’t need to introduce another approach.
“I don’t really recommend for or against [L-glutamine supplements]. But I advise that if they feel like there is an improvement in symptoms, then continue. Otherwise, [don’t] keep spending your money if you do not feel it is making any difference,” says Andrew Moore, MD, a Chicago-based gastroenterologist with Endeavor Health Medical Group.
If you choose to take a supplement, be sure to look for ones that are third-party tested, because the U.S. Food & Drug Administration (FDA) does not test supplements for safety or effectiveness. Bass recommends only buying those tested by one of the following companies: United States Pharmacopeia (USP), NSF, or ConsumerLab.com.Always talk to your doctor before starting a new supplement, as L-glutamine can interfere with certain medications and shouldn’t be used by people with liver problems. “Look for a pure L-glutamine powder without added sweeteners, flavorings, or fillers,” Simpson says.
The Takeaway
L-glutamine is an amino acid naturally found in your body that, when supplemented, may help ease gastrointestinal symptoms in those with IBS-D and post-infectious IBS.
Specifically, research shows that L-glutamine supplementation may reduce intestinal permeability and potentially enhance the effects of the low-FODMAP diet.
There isn’t enough evidence to suggest that L-glutamine supplementation can help with other types of IBS, such as IBS-C and IBS-M.
Even though taking L-glutamine isn’t linked to many side effects, it’s always a good idea to talk with your healthcare provider or care team before starting a new supplement.
