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  • Writer's pictureTrina Palomarez, CNS

Understanding Root Causes of IBS

Updated: Jul 30, 2023

IBS, or Irritable Bowel Syndrome, is a digestive disorder that is estimated to affect up to 10-15 % of the population in the US. It is characterized by changes in bowel habits, such as chronic constipation, chronic diarrhea or both. Other common symptoms include bloating, abdominal pain and digestive spasm. There can be a dramatic range in intensity of IBS symptoms, from mild to so severe that it prevents some people from working a regular job or even leaving the house. In western countries, IBS affects more women than men, although IBS is frequently diagnosed in both sexes in all age ranges.

Understanding and managing the root cause of IBS is a critical piece to healing and coping with symptoms. In the past, very little was known about the etiology of IBS. More recently, a better understanding of IBS and the mechanisms behind it, have led to a wider range of treatment protocols allowing for a higher quality of life. If you or someone you know is struggling with IBS, then understanding the root causes of this syndrome may help you make the pathways you need to start improving your health today.

What Is IBS?

IBS is often considered a diagnosis of exclusion. People with this disorder, characterized by pain and dramatic changes in bowel pattern, will usually undergo a battery of tests when addressing their digestive concerns with their doctor. Common testing often includes, food allergy testing, testing for parasites and celiac disease and possible colonoscopy. If all digestive tests return normal, but the patient is still struggling with symptoms, they will often get a diagnosis of IBS. What this means is that although these patients are dealing with real symptoms, there is no definitive testing method to identify the actual cause of this digestive disturbance. A diagnosis of IBS can leave those suffering from it feeling isolated and overwhelmed as they struggle to understand why this is happening and what to do about it.

Conventional Approaches to IBS

Conventional medical treatment of IBS can be challenging at best. Most methods are aimed at controlling or modulating symptoms. If someone struggles with IBS with constipation they will often be recommended motility agents such as Miralax, Milk of Magnesia or large doses of fiber. More severe cases may warrant medications such as Linzess which promote more regular bowel movements.

IBS with diarrhea has a similar series of treatments with motility agents including Immodium and bismuth subsalicylate (Pepto-Bismol) to stop diarrhea. Antispasmodics are also often prescribed for those struggling with pain. These medications can be useful for managing symptoms in some cases but results are not often permanent and for many, symptoms may return over time.

Identifying the Root Causes to IBS

For many years IBS was seen as a psychosomatic illness, triggered by stress and emotions with no definitive treatment. Many patients with IBS have heard from their doctors that it was “all in their head”, or even worse, that there was nothing left to be done for them if their symptoms did not improve with common medical treatments. Although there is a very strong connection between mental state and IBS (more about that to come), it is not the only reason for IBS.

There are actually many causes and triggers to IBS and identifying them involves a skilled understanding of the gastrointestinal system, along with a fluid knowledge of the way that food, emotions and environmental factors interplay with the gut.

Here are some common underlying causes of IBS and how they develop in the gut.


SIBO is an acronym for small intestinal bacterial overgrowth. You may not have heard of it, or your doctor for that matter, as it is still a relatively new topic in the world of medicine and GI health. SIBO is a disorder associated with changes in the gut microbiome that can lead to changes in bowel patterns associated with IBS.

In a healthy digestive tract there is an abundant amount of bacteria in the large intestine, with adequate amounts of beneficial bacteria and very little bacteria in the small intestine. In SIBO bacteria gets into the small intestines, sets up shop and reproduces, leading to overgrowth. This bacteria consumes some of the foods we eat and produces gases that are often associated with constipation and/or diarrhea. While in the small intestine this bacteria damages the intestinal lining, interfering with nutrient absorption and creating irritation. Over time this irritation and inflammation caused by this bacteria can create long term changes in motility, resulting in chronic constipation and/or diarrhea, which in turn can be diagnosed as IBS.

SIBO has many has many causes, with some of the top triggers being food poisoning, use and/or overuse of certain medications such as antibiotics, NSAIDs, narcotics and antacids, food allergies and sensitivities, low stomach acid, leaky gut, environmental exposures and chronic stress. Treatments for SIBO are varied and include the use of specific types of antibiotics, herbal remedies, probiotics, motility agents and specialized diets, all with a goal of restoring the delicate balance of the microbiota. These treatments are sometimes used alone but more often in combination to achieve the best results.

Food Intolerance

Food moves through the colon via muscular contractions called peristalsis. As certain foods pass through the colon, it can cause the colon to constrict and even spasm in some individuals with IBS, resulting in intense pain. Consumption of foods that are naturally high in fiber, high FODMAP foods ( a category of carbohydrates that contain fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) and foods that are not digested well in certain individuals such as dairy products, for example, can all potentially cause cramping, constipation and/or diarrhea in those with IBS.

As discussed earlier, food intolerance is also a potential trigger for SIBO, which in turn can be an underlying cause of IBS. When we regularly eat foods that we don't digest properly they can create irritation and inflammation which can set the stage for both motility issues (too fast or too slow) and increase the risk for bacterial overgrowth. Identifying potential food allergies and removing them from your normal diet can be a helpful tool for those struggling with IBS.

Gut Brain Axis

Stress has been thought to be a cause of IBS for many years in the medical community. As we have learned in this article, there are many underlying causes to IBS, it is not just about stress, but stress and how it affects the body, mind and gut can be real trigger for some.

The parasympathetic nervous system is one of three divisions of the autonomic nervous system which plays a vital role in keeping our bodies functioning at optimal levels. Sometimes called the rest and digest system, the parasympathetic system conserves energy as it slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in the gastrointestinal tract. There are several body functions stimulated by the parasympathetic nervous system including sexual arousal, salivation, lacrimation, urination, digestion, and defecation. In order to maintain healthy, regular bowel movements, our bodies need to be in a calm rest and digest state.

When the body is under stress or perceived stress, the sympathetic nervous system takes over, also known as fight or flight. While in the sympathetic state, the heart rate increases and muscles contract. Being in the fight or flight state can cause some people to experience constipation, as the bowls shut down, and for others it causes the bowels to become overly agitated leading to loose stools or diarrhea.

If you have ever noticed changes in your bowel movements while you are travelling (too slow or too fast), this is an example of how the sympathetic nervous system affects the gut, a connection often referred to as the gut brain axis. This connections affects many aspects of digestion, not just bowel patterns. For some being in the sympathetic state can cause pain and cramping in the GI tract, as signals to inhibit or reduce digestive capacity are sent from the nervous system to the gut. For others they may experience bloating, or reflux, but the symptoms stem from the body's state of high alert, triggered by stress which directly impacts gut function.

It is normal to experience stress and have changes in bowel patterns, but in terms of IBS, the natural stress response of the body is often chronically overactivated, and difficult to shut off. People with IBS can also develop stress based bowel changes that manifest out changes in gut flora. Overgrowth of bacteria and/or food intolerances can cause changes in bowel patterns, which can make a person feel stress and anxiety. The stress about changing bowel patterns can in turn can make bowel symptoms worse, and there begins a vicious cycle of heightening stress levels causing more pain, diarrhea and/ or constipation. In order to maintain a healthy digestive tract and promote regular bowel patterns, it is essential to address the effects of stress on the body and find a way to manage it successfully.

There was a time when it was believed that IBS was only a stress response and that there was no real treatment. Now with a better understanding of the gut and the microbiome, we know that there are a variety of factors involved in the development of IBS, and treatment and recovery is dependent upon addressing the appropriate underlying causes and managing all aspects of their effects on the body.


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