A few studies suggest that L-glutamine supplements may help IBS symptoms, but more research needs to be done.

L-glutamine, or just glutamine, is an amino acid. Amino acids are molecules that form the basis of proteins. When you eat protein-rich foods, your body breaks down the protein into amino acids, which are important for human health.

L-glutamine is one of 20 essential and nonessential amino acids that create proteins. Essential amino acids can only be obtained through food. Nonessential ones, like L-glutamine, are produced by the body.

Under normal conditions, your body can produce enough L-glutamine to meet most of its needs.

L-glutamine may help irritable bowel syndrome (IBS), a common intestinal disorder. The supplement may help people who have received an IBS diagnosis or experience IBS symptoms regularly.

Symptoms of IBS may include:

L-glutamine appears to have a role in maintaining proper barriers within the intestine. Tissues in the intestine also use this amino acid as a fuel source to function well.

In some instances, L-glutamine deficiency may influence IBS. Glutamine deficiency may lead to increased intestinal permeability, a condition where substances move too easily through the wall of the intestine. This could be linked to IBS.

L-glutamine deficiencies can occur from several causes, including:

You may experience side effects if you’re allergic to L-glutamine or take too much. Potential side effects include:

If you notice any side effects or other reactions, seek medical attention immediately. As with any supplement, talk with a doctor before starting L-glutamine to make sure it’s for you to take.

Some research supports glutamine supplements for IBS, but additional, larger studies are needed to confirm any benefits.

One study from 2019 found that taking 15 grams of glutamine supplements per day for 8 weeks improved symptoms in people who had developed diarrhea-predominant IBS (IBS-D) following an intestinal infection.

A 2021 study examined pairing a low FODMAP diet (a common diet for treating IBS) with 15 grams of a glutamine supplement per day for 6 weeks. Researchers found that the group that took the supplement while following the diet had reduced IBS severity compared with the group that just followed the diet.

Another study from 2022 found that participants who took 15 grams of glutamine per day for 6 weeks had reduced frequency of abdominal pain and lower dissatisfaction with bowel habits compared with the group that took iso whey protein, another popular supplement.

In general, taking L-glutamine appears to be safe if you stick to recommended dosages.

For IBS, the dosage your doctor recommends will depend on your specific case. Studies typically involve taking 5 grams of glutamine three times per day for a total of 15 grams daily. High doses of glutamine range up to 40 grams per day.

Some research indicates that glutamine is essential for the growth of some cancer cells. However, other studies are investigating whether glutamine supplements can be part of cancer treatments.

More research is needed to determine whether people with cancer or a high risk of cancer should take or avoid glutamine supplements.

Sources of L-glutamine

Your body produces L-glutamine, but you can also take it as a supplement or prescription medication or consume it through your diet. Sources of glutamine in foods include:

  • chicken
  • fish
  • dairy
  • grains
  • tofu
  • corn

Your doctor may recommend L-glutamine supplements to address a deficiency, especially in times of significant stress or severe illness.

Talk with your doctor about L-glutamine as a possible supplement for improving your IBS symptoms. If you think you have a deficiency from health problems or other issues — and have IBS — L-glutamine might help.

Taking an L-glutamine supplement may reduce IBS symptoms, but more research needs to be done. Make sure to talk with your doctor before you begin taking it.

As with any supplement, remember to follow dosage directions and guidelines carefully. If you experience side effects, seek medical care right away.