What Triggers IBS? 5 Surprising Root Causes

Did your doctor diagnose you with IBS, but your symptoms are not improving with treatment? While well intentioned, many doctors are quick to label most GI conditions as “IBS” without investigating what triggers your IBS in the first place.

Stacy and I see this time and time again with our clients, and it can be so frustrating when you feel your “gut feelings” are being ignored. We know it feels dismissive to know that something is wrong but yet you get the “IBS” diagnosis without further investigation.The good news is that there is new research on the most common underlying causes of IBS your doctor may not be talking about(1). Now, it’s possible to understand what triggers your IBS with a proper diagnoses.

This is why we take such an individual approach with our clients, because no one IBS “type” is the same.

This article will reveal the 5 surprising root causes of IBS, common symptoms, diagnosis and how they’re treated. Read on to find out what may be causing your IBS and how to take a more targeted approach to feeling better.

Because how amazing would it feel to know what triggers IBS symptoms for you so you can cut out the guesswork?

Root Causes of IBS

1.   SIBO (Small intestinal bacterial overgrowth)

SIBO is a condition where the bacteria in our small intestine shifts out of balance. Normally, we should have a limited amount of good gut bacteria in the small intestine.  This is the same good gut bacteria we have in the colon.  So, the problem is that it has overgrown in the small intestine because the motility of the small intestine has slowed down. 

This can lead to unpleasant symptoms, and we know from firsthand experience just how unpleasant they can be.

SIBO is more common than many think, and studies show close to 80% of those with IBS also have SIBO!  It is frequently underdiagnosed by medical doctors, which can delay proper treatment(2).

We have had clients who were diagnosed with IBS years ago and were never tested for SIBO.  That means they had been struggling with miserable SIBO symptoms unnecessarily for years.  UGH!


  • Bloat
  • Gas
  • Diarrhea, constipation or both
  • Feeling overly full after eating
  • Loss of appetite
  • Unintentional weight loss


SIBO is diagnosed through a test that measures the levels of hydrogen and methane in your breath. This helps determine the presence of gas-producing bacteria in your gut. If it is above a certain level, this may signal SIBO.


Treatment for SIBO is all about addressing the underlying cause, and can involve several interventions:

Diet – There are 3 main types of diets for SIBO – the low-FODMAP diet, the SIBO Bi-Phasic Diet, and the Specific Carbohydrate Diet (SCD). All of these reduce the number of carbs available for the bacteria to feed on.  Unfortunately, diet is not a cure for SIBO but can help manage symptoms.

Learn more about these 3 diets here.

Antibiotics or Herbal Antimicrobials – Antibiotics are often given for SIBO to reduce the number of bacteria present. They are not meant to be a long-term solution however, as they can also decrease the number of good bacteria in the gut along with the bad(3).

Learn more about how to treat SIBO naturally here.

Address Root Cause

SIBO can be a recurring condition if the underlying cause is not addressed.  This means we need to determine what is causing the slowing of the motility of the small intestine and help it resume its proper function. 

The most common causes of SIBO that we see in our practice include:

  • Low thyroid function
  • History of food poisoning or traveler’s diarrhea
  • Stress! 

Learn more about other root causes of SIBO here.

2.   Bile Acid Diarrhea

Bile is a fluid made by the liver needed for fat digestion. In bile acid diarrhea (BAD), your body doesn’t properly process bile, which prevents high-fat foods from being digested and absorbed. BAD is said to be present in ⅓ of people who have IBS-related diarrhea(4).


  • Watery stool
  • Urgency
  • Fecal incontinence
  • Nutrition deficiencies


There are 3 main tests to diagnose BAD:

  • The 75selenium homotaurocholic acid test (75SeHCAT)
  • Serum biomarkers of hepatic BA synthesis (serum C4 and FGF19)
  • Total and individual fecal BAs

All of these tests measure the amount of bile loss, which can indicate that BAD is present. The SeHCAT test is said to be the most accurate, but unfortunately it’s not yet available in the U.S.(5). Total and individual fecal BA’s are the most common tests performed in the U.S.


Treatment for BAD can involve medications called bile acid binders, and limiting fat in the diet can bring relief. The good news is that a low fat diet can reduce symptoms and put less strain on the digestive system(6).

Learn more about dietary fat and the best types here.

3.   Carbohydrate Malabsorption

Carbohydrate malabsorption happens when the body has trouble absorbing certain carbs, starches, and sugars in the diet. It usually occurs because your body lacks the enzyme to digest the particular sugar.

The most common types of carbohydrate intolerance include lactose (milk sugar), fructose (fruit sugar), mannitol and sorbitol (sugar alcohols found in foods like mushrooms and apples) malabsorption.


  • Gas
  • Abdominal Pain
  • Cramps
  • Diarrhea
  • Headaches


The standard test for carbohydrate[1]  malabsorption is the hydrogen breath test. These tests are most commonly used to detect a lactose, fructose or sucrose (table sugar) malabsorption). If a high level of hydrogen exists, that’s a sign your body is having trouble digesting that particular sugar.


Carbohydrate malabsorption can also be determined and addressed with an elimination diet, where you limit or remove the offending carbohydrate. This is why a low-FODMAP diet can be incredibly helpful. You initially limit several carbohydrate groups known as FODMAPs  and then test your tolerance to them through a structured reintroduction process one by one.

We have worked with hundreds of  clients on the low-FODMAP diet, helping them to identify their biggest offenders with the goal of enjoying the least restrictive diet possible.

Here’s a sneak peak into the low-FODMAP diet.

4.   Exocrine Pancreatic Insufficiency

Pancreatic exocrine insufficiency, or PEI, is when your body doesn’t make enough pancreatic enzymes for digestion, or the enzymes don’t work as well as they should. There are 3 main types of pancreatic enzyme – lipase digests fat, protease digests protein, and amylase digests carbohydrates.


  • Abdominal pain
  • Gas
  • Bloating
  • Fatty stool (pale, oily, foul-smelling stool that floats)
  • Unexplained weight loss


There are 3 main tests used for PEI:

  1. Fecal elastase test. This test measures the amount of elastase, an enzyme produced by the pancreas, in your stool.
  2. Fecal fat test. This test checks the amount of fat in your stool.
  3. Pancreatic function test

The pancreatic function test is thought to be the most accurate, but it is performed only at specialized centers. With that being said, most of our clients are diagnosed with one of the stool tests.


Treatment for PEI involves plenty of fluids and a low fat, low fiber diet. Digestive enzyme supplements or prescription-strength pancreatic enzymes can be helpful for PEI.

Learn more about gut healing diets like low fiber here.

5.   Microscopic Colitis

Microscopic colitis is an inflammation in the large intestine that doesn’t often show up on a traditional colonoscopy. As its name implies, it typically can only be seen under a microscope.


The most common symptom is persistent watery diarrhea that doesn’t respond to traditional colitis treatment.


A colon tissue sample (biopsy) is typically obtained during a colonoscopy, so it can be viewed under a microscope.


Common treatment for microscopic colitis involves diet and medications to reduce diarrhea.

The diet recommended is a low fat, low fiber diet. Also, caffeine and sugar are sometimes limited if they are seen to be a trigger. Dairy and gluten are sometimes restricted if they are seen to worsen symptoms.

Luckily, it’s usually not necessary to avoid all these foods. This is why we help our clients identify the biggest food triggers through tracking and elimination.

Key Takeaways: What Triggers IBS?

What triggers IBS is highly individualized, which is why there shouldn’t be a one-size-fits-all approach to treatment. If you’re suffering from IBS symptoms and are not responding to conventional treatment, speak to your doctor about these 5 potential root causes.

Managing IBS takes a whole team approach to incorporate diet, supplements, medications, and lifestyle therapies. This is why we created our personalized gut healing program …to get to the root of your symptoms and help you feel your very best.

If you want personalized guidance so you can stop grasping for straws on IBS treatments, sign up for a free 15-minute nutrition strategy session today.

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