Last Updated: 27 March 2023

L-Glutamine for IBS – Does It Help?

Researched & Written By:
L-Glutamine is one of the most popular supplements for gut health these days. But can this amino acid really help with IBS? In this guide, we look at all the research that has been conducted on human tissue (ex vivo) and in human trials (in vivo), to see how glutamine impacts intestinal permeability and in turn may help with symptoms of IBS. We even cover which IBS subtypes it might be more beneficial for. And finally, we uncover how much L-Glutamine to take, based on the amounts used in studies. By the end of this guide, you'll know if L-Glutamine is worth considering or not.
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Table of Contents

What Is Glutamine?

Glutamine is one of the 20 amino acids our body needs to function. We get glutamine from the protein we eat in our diet, but our bodies can also make glutamine on their own, which is why glutamine is considered a non-essential amino acid. 

With that said, while glutamine technically isn’t one of the 9 amino acids considered to be “essential,” it’s not your average amino acid. It’s the most abundant amino acid in the human body, and is extremely versatile.

Why do we need glutamine?

Not only is it used as a building block to make new proteins, it also has several other significant jobs. These include the modulation of inflammation, regulation of cellular lifespan, and acid-base balance maintenance. Significant amounts of glutamine are also needed by our rapidly dividing gut and immune cells. And if that wasn’t enough, glutamine is used to make a wide variety of very important molecules, such as other amino acids, the nucleotides that make up DNA strands, and molecules that prevent cellular oxidative damage. 2Talk about a multitasking superstar!

Long story short, glutamine is pretty important to our basic functioning. Safe to say we probably wouldn’t last too long if our bodies couldn’t make it on their own.

Glutamine rich foods like salmon
Glutamine is an amino acid found in dietary protein sources like salmon and spinach

Why would we need to supplement glutamine?

Great question. So here’s the deal…

Research done on critically ill patients (think, hospital intensive care units), have found significant associations between low glutamine plasma levels and worse outcomes. Because of these findings, glutamine is thought to actually be a “conditionally essential” amino acid, as it seems that our need for glutamine can sometimes exceed what the body is able to make.5

Indeed, giving extra glutamine has been shown to be effective in decreasing mortality and infections in certain groups of critically ill patients, such as those with severe burns or trauma with delayed wound healing. With this, supplementation is recommended by well-respected organizations, like the European Society for Clinical Nutrition and Metabolism (ESPEN).6

How might glutamine help IBS and gut health?

Along with low glutamine levels, studies on the critically ill have also found that it is common for these patients to have increased gut permeability, which can be improved by supplementing with glutamine.78

In addition, studies have also shown that when there is not enough glutamine, tight junctions, the proteins that help regulate gut permeability, are decreased and intestinal permeability increases. 

However, this effect was reversed when glutamine was reintroduced.9

These connections between glutamine, gut permeability, and tight junctions are relevant for those with IBS, as increased gut permeability is a relatively common occurrence in IBS, especially IBS-D and post-infectious IBS (PI-IBS).1011

L-Glutamine may help intestinal permeability
L-Glutamine may help intestinal permeability and in turn IBS
Compared to controls, significant decreases in the expression of tight junction proteins have been observed in IBS patients, particularly in those with IBS-D.12

Quick Summary

Does L-Glutamine Help IBS?

So, can supplementing with glutamine help fix gut permeability issues in IBS patients?

While the evidence we’ve reviewed so far suggests that it might, the unfortunate truth is that very few studies have directly tested this theory. With that said, we are here to give you the most up-to-date and accurate information available, so sit tight, and we’ll go over what is out there to help you decide if you should consider using glutamine.

L-Glutamine IBS ex vivo
Ex vivo studies involve taking tissue from the subject and testing it outside their body

2010 study - ex-vivo

In 2010, a group of researchers from Ohio, USA, published a study on IBS-D patients with increased gut permeability.13

They found that this specific subgroup of IBS patients had significantly increased expression of a micro RNA called miR-29a, which regulates permeability and the gene that is used to make glutamine synthetase, an enzyme that makes glutamine.

They then took biopsied gut tissue samples from some of these subjects. Sure enough, they found that the patients with elevated miRNA-29a expression also had decreased expression of glutamine synthetase.

This suggests that some IBS patients may be making less glutamine due to epigenetic changes.

2016 study - ex-vivo

In 2016, French researchers did a study where they took colonic biopsies from IBS-D subjects and incubated them with varying amounts of glutamine.14

They found that glutamine increased the expression of claudin-1, one of those tight junction proteins.

They also found a significant negative correlation between how effective glutamine is at increasing tight junction expression and the basal level of expression of both claudin-1 and occludin. In other words, the lower the expression of these tight junction proteins were to begin with, the more effective glutamine was at increasing their expression.

This gives further evidence that glutamine may be helpful for those with increased gut permeability and that the extent to which it can help may be predicted by how many of those tight junction proteins are being made. 

Alright, so far we’ve got some nice test tube studies with promising results. What about supplementing glutamine in actual humans? 

Glutamine IBS in vivo
In vivo studies involve performing tests "within" the subject - in this case, measuring changes in IBS patients (human subjects) from consuming L-Glutamine supplements.

2019 study - in vivo

In a study published in 2019, the authors took PI-IBS patients with diarrhea and increased intestinal permeability.

They randomized them into two groups: glutamine (5 g, 3 times a day) and placebo.15  They then measured the change in IBS symptom severity scores (IBS-SSS), with a significant improvement equating to a 50-point score reduction.

By the end of the 8-week trial, they found that 80% of the glutamine group showed a significant response to glutamine versus 6% in the control group. They also found significant improvements in daily bowel movement frequency, stool consistency, and intestinal permeability. Super impressive!

Minor adverse events were reported, including abdominal pain and bloating in 1.9% of the participants.  However, there were no significant differences in adverse events between the glutamine and placebo groups.  

So yay! Promising results have been shown! But what about our other IBS subtypes? Any evidence glutamine can be helpful for them too? Possibly!

2021 study - in vivo

The most recent study on glutamine and IBS was a 2021 randomized controlled trial that did include all subtypes.15

The same dose of glutamine that was used in the previous glutamine study (5 g x 3 times a day) was used for the treatment group in this study. However, unlike the other study, all participants were first put on a low FODMAP diet and then randomized into a treatment or placebo group.

After 6 weeks, significantly more of the group receiving glutamine had a 45% drop or more in their IBS-SSS, compared to the placebo group (88% vs 60%). The glutamine group also had more significant results when it came to their total IBS-SSS, dissatisfaction with bowel habits, and interference with life.

In other words, both groups showed improvements on the low FODMAP diet, but those taking glutamine improved even more! 

The takeaway from these studies

Based on the available literature, glutamine may be beneficial in relieving IBS symptoms, especially in patients with PI-IBS or IBS-D, as they are more likely to have increased intestinal permeability and decreased expression of tight junctions, which glutamine has been shown to help regulate.

Glutamine may be helpful if you have IBS-C, or another subtype, but there just aren’t enough studies yet to confirm that. 

Quick Summary

How To Take L-Glutamine For IBS

How much to take (dosing)

In both in vivo studies we looked at above, the dose given was 5 grams, 3 times a day.  In other words, what has been studied in IBS populations is 15 grams of L-Glutamine per day.

Side effects of L-Glutamine

The good news is that there really aren’t many downsides to giving glutamine a try. While long-term supplementation hasn’t been studied, the current studies on IBS patients haven’t shown that glutamine causes severe adverse events in the doses used.161718

As always, you should check with your doctor before starting or stopping any medication and/or supplements.

Summary & Verdict

IBS ebook

Which Foods Really Trigger Your IBS?

Discover exactly which foods you should and shouldn’t eat using our IBS Food Journal.

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