IBS treatment with a FODMAP diet: How it fixes symptoms

If you’re looking for an IBS treatment, you’ve likely heard of a low FODMAP diet. If you haven’t, our last video blog covered what FODMAPs are and why they cause gut issues. You can check that out by clicking here.

It seems too-good-to-be-true that a simple dietary intervention would improve IBS. The symptoms in IBS are crushing, and have a major impact on quality of life. Many IBS sufferers note that their symptoms exert a large influence over their lifestyle.

A recent study compared the low FODMAP diet to otilonium bromide(OB). OB is an anti-spasmolytic drug used to relieve pain in IBS.

The low FODMAP diet was administered via an app and wasn’t a strict low FODMAP diet(LFD). Instead, they followed a more bottoms-up approach where only some high FODMAP foods were restricted and others allowed. We explained why a bottoms-up approach is likely better in the video linked above.

Within 4 weeks, the low FODMAP diet outperformed OB. Interestingly, adherence was greater in the LFD group vs the PB group(94% vs 73%). Additionally, more people saw relief in LFD too.

In the group following the LFD, 62% of participants saw improvement in 4 weeks vs 51% in the OB group. At 8 weeks, 71% of the people in LFD saw benefit, compared to 61% in the OB group.

This is great news, but brings up a few questions. First, how does the LFD improve symptoms so well vs OB? Secondly, would these persist long term? Fortunately, another smaller study gives us a little insight.

IBS treatment

How does IBS treatment with a low FODMAP diet work?

One of the predominant theories in IBS is that the microbiome plays an important role. This jibes well with the research on low FODMAP diets.

The rapid fermentation of FODMAPs by the microbiome of people with IBS may drive abdominal pain, gas, and bloating. But it’s actually not quite that simple.

Not all studies show more gas production in people with IBS vs healthy controls. However, they do experience more severe symptoms. So there are definitely other things going on.

A recent paper shows that the microbiome does play an important role in the response to an LFD. It’s actually a really cool study.

Low FODMAP diet high responders

In this paper, they found substantial symptom improvement with LFD after 4 weeks in 75% of participants. However, they identified a group of people who saw significantly more improvement based on their starting microbiome.

They labeled this group IBSP for IBS pathogen-like and the other IBSH for IBS health-like. The microbiome of these people were enriched in genes that metabolize carbohydrates and synthesize amino acids. Of note, this microbiome would generate more butyrate from FODMAPs and synthesize more of the amino acids tryptophan and histidine.

These amino acids are precursors to serotonin (5HT) and histamine, both believed to play a role in IBS. Furthermore, while butyrate is generally considered beneficial, excess production of it and other solutes pull water into the colon, causing diarrhea. On top of this, butyrate increase serotonin production.

After 4 weeks on LFD, the microbiome of IBSP shifted towards that of IBSH. Though IBSP had a much more severe IBS symptom severity score at the beginning of the study, their scores were nearly identical after the microbial shift.

On top of this, both their symptom scores and microbiome remained similar 12 weeks after the diet. During this period, some participants restricted trigger foods identified during re-challenge.


The microbiome appears to be a significant player in IBS. IBS treatment using a low FODMAP diet causes significant shifts in the microbiome. As a result, metabolites that exacerbate IBS symptoms decrease and symptoms improve.

Another interesting aspect of this second study is that microbiome testing may help identify low FODMAP diet responders. Subsequently, in the future, we may be able to use microbiome testing to identify specific FODMAPs that individuals should avoid.

It’s also interesting that a low FODMAP diet seems to work better than a commonly prescribed drug for treating IBS. Of note, the use of a bottoms-up approach without the standard 8 week hardcore FODMAP restriction likely made compliance much easier.

To sum up, IBS treatment with a low FODMAP diet improves symptoms by shifting the microbiome in a beneficial way. This may be due, at least in part, to changes in microbial metabolites that exacerbate IBS symptoms.

Therefore, using a low FODMAP diet helps address IBS and provides long term support when people limit trigger foods.

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