What Causes IBS?

Jan 21, 2017 by


You can have me read this article to you instead of reading it yourself…

Or you can read it the old-fashioned way below…

So what causes IBS?

Well, that’s not really a straightforward question.  And we are still learning more about the exact causes for some people.  But what we do know is that it appears to be related to how the GI tract interacts with its environment.  I’ve definitely heard plenty of jokes in the way of “Oh you have an irritable bowel?  Well I’m irritable, too!”.  (And if you’re interested in a pretty hilarious comic on this topic, click here!)

But the truth is, the jokes aren’t that far off from the reality.  When IBS occurs, the symptoms develop because your gut really is irritated, and that irritation is caused by something in its environment.

The Gut Environment

This term is a bit misleading, so let’s discuss what the ‘environment’ actually means in this case.

The gut is affected by all sorts of things.  This can include the foods and fluids that you place into it when you eat and drink.  This can also include the bacteria that live inside of your gut – a relationship that, the majority of the time and for most people, is happy and nurturing to the body.  It can also be affected by the hormones that are travelling through the body, as well as the nervous system transmitting messages from the brain.

Food and Fluids

It turns out that some people with IBS actually have a sensitivity to a specific food ingredient.  Sometimes these ingredients are the molecules that make up larger parts of your food, so they can be hard to pin down.  For instance, some people find that they are intolerant of one specific kind of sugar molecule.  Pretty picky, huh?  In an upcoming section we will talk about how this can be identified and managed.  There are more nuances here, but this is a general way to think about how the things that we consume can cause your gut to get irritated.

Gut Bacteria

[If you’re curious about this topic, I talk about the gut bacteria in all of its spectacular strangeness here.]

We all have bacteria living in our guts.  Lots and lots of them, actually.  I talk about that in great detail here.  These bacteria are a good thing for us – they help to keep us healthy and they even help to break down the foods that we eat.

But sometimes those bacteria can move to a new place in the intestine where they don’t belong, and that can cause problems.  Or, a new species of bacteria that your gut is not a huge fan of can decided to settle in and make a home there.  Both are clear reasons for the gut to be out of sorts and react poorly.

Sometimes the bacteria in your stomach are also the reason for certain food sensitivities.  For instance, if your body doesn’t absorb a certain ingredient the way that it should, then the bacteria get to digest it, converting it to gas or liquid products that can cause some unpleasant symptoms.

Hormone and Nerve Signals

[If you’ve been hearing about the brain-gut axis and the “second brain” in our guts, get the full story here.]

Anyone with IBS can tell you that it seems to be awfully correlated to their moods or the stressors occurring in their lives.  This isn’t just coincidence or a self-fulfilling prophecy.  The intestine is very sensitive to the nerve signals coming from the brain and the hormones circulated throughout the body.  Enough of either of these signals can make the gut act differently, whether that is to slow down, speed up, or just fly off the rails in an unexpected way.

We are learning more and more that the gut itself is responsible for sending nerve and hormone signals right back to the brain and the rest of the body, which can impact mood and stress levels.  So this is most definitely a two-way process!  It is called the brain-gut pathway, and I talk about it a lot more here.

But What Triggers It?

Most people don’t grow up with IBS, or even develop it before their teenage or adult years.  So it seems clear that something changed in the body that led to this irritated state for the gut.  We are still learning more about what might cause this to happen, and it is likely different for each person.  The differences can depend on general health, the living environment, mental state, and more.

For instance, there are previously healthy people that develop IBS.  In these cases, there seems to be some type of event that tipped the scales.  These could include a viral or bacterial infection in the GI tract, or even an episode of extreme stress or anxiety.

Other people experience a slow increase in symptoms over time, with no clear idea of where they came from.  This could be the result of greater changes to their living environments, to the foods they have eaten, to the bacteria that are living in their bodies, and more.  There is also good research to indicate that some people who struggle with depression and anxiety are more likely to develop conditions like IBS over time.

We are still learning more about this condition every day, and it is a hot focus for research right now.  I imagine this section will require some pretty regular updating as time goes on!



Interested in more information on IBS?

Next: How is IBS Diagnosed?

Or refer back to the IBS Info Hub.


Trivia and Terminology:

The Gut Microbiome contains 10 times more bacterial cells found in the gut than the number of cells in the entire human body.  All combined, the gut bacteria would weight about the same as your liver.

Gut bacteria aid in digesting certain substances, help our bodies to absorb nutrients, and also play a role in our immune systems (more on this here).

The Brain-Gut Axis is basically a nerve and hormone highway from our minds to our guts.  It is surprising how much one can directly influence the other, although limitations to its capabilities do exist (more on this here).


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