Irritable bowel syndrome

Irritable bowel syndrome

Irritable bowel syndrome, or IBS for short, is a term used to describe a group of gastrointestinal symptoms that vary from person to person, but can include constipation, diarrhea, gastric upset, and bloating. Constipation being the most common symptom.

Irritable bowel syndrome is becoming more common in these modernized times and the Journal of the American Medical Association noted that IBS now affects between 7 percent to 21 percent of the general population.

Although the exact cause of IBS is unknown, some factors thought to play a role in the development of IBS include genetics, western diet, female sex (estrogen), infectious gastroenteritis, altered gut motility, inflammation, altered gut microbiome, hypersensitivity, altered gut immune responses, food intolerance, and dysregulated gut-brain axis.

IBS is found more commonly in women and those 18-50 years old. In addition, since one of the risk factors for IBS is a western diet full of processed foods, IBS is found more commonly in modernized countries. It is estimated that 10-20% of the population in the Western World have IBS, while only 6.5-10.1% of people in Asian countries.

Risk Factors for IBS

Age: IBS is seen in all age groups, but typically occurs in the first half of life. Around 50% of patients with IBS report having symptoms before the age of 35 years and most sufferers are typically between the age of 18-50.

Sex: Women are at higher risk for IBS than men. Some postulate this is due to the hormone estrogen as many women report a worsening of symptoms during their menstrual cycle. In addition, when women no longer have periods after menopause IBS seems to resolve or is reduced.

Genetics: Genetics may also play a role in the development of IBS as 33% of patients with the condition have a family history of IBS.

Western Diet: Processed foods and foods with additives are thought to trigger or worsen the condition. 

Anxiety or other psych disorder: Studies have linked anxiety to IBS, this is because the GI tract is sensitive to and mirrors emotional upset.

Gastrointestinal infection or altered GI bacteria: Like the rest of the body, the GI tract needs to maintain homeostasis. When the GI tract is altered due to infection or change in GI bacteria the person is at risk for a condition such as IBS.

Symptoms of IBS

Symptoms vary per case, but can include some combination of the following

  • Chronic abdominal pain and discomfort
  • Frequent loose watery stools (diarrhea)
  • Infrequent hard to pass stools (constipation)
  • Bloating

IBS patients also suffer from multiple comorbidities such as indigestion, fibromyalgia, gastro-esophageal reflux disease, interstitial cystitis, chronic fatigue, chronic back pain, insomnia, and headache/migraine.

A strong association of psychiatric disorders occurs in IBS patients, suggesting the role of psychological factors in the etiology of IBS. The gut and the brain are closely connected and have an impact on each other. Just as a nervous mind can cause a nervous belly, an unhealthy gut full of bad bacteria can increase the risk of mental health disorders also.

Types of IBS

There are three main types of IBS, which are based on stool formation. Although some patients will not fall into any of these three categories and will be “unclassified.”

Constipation-predominant Irritable Bowel Syndrome

  • Majority of stools are hard or lumpy
  • Minority of stools are loose/mushy or watery

Diarrhea-predominant Irritable Bowel Syndrome

  • Majority of stools are loose/mushy or watery
  • Minority of stools are hard or lumpy

Mixed-Irritable Bowel Syndrome

  • Equal amount of loose/mushy and hard or lumpy stools

Role of SIBO in IBS

The relationship between gut microbiome (bacteria) balance and gut health is supported by several scientific studies. So it shouldn’t be surprising that evidence shows that an increased amount of bad bacteria in the small intestine, known as (SIBO), is linked to IBS.

The human gut is colonized by 100 trillion microbes which play a role in the functions and maintenance of the GI. The number and composition of gut microbes vary along the length of the GI tract. In a healthy individual, the number of microbes increases further down the GI tract you go. In other words, the closer to the mouth, the fewer microbes and the closer to the anus, the more microbes are found.

The gut will function normally under healthy conditions, but when the number of microbes is out of balance issues can occur. There are several factors that can disrupt normal gut microbial environments such as repeated antibiotic use, western diet, infections, and stress. When enough stress or environmental factors occur, the gut can enter a state of imbalance called dysbiosis. Dysbiosis can cause colonic bacteria to migrate into the small intestine, leading to increased colonic bacteria in the small intestine. This is referred to as small intestine bacterial overgrowth (SIBO).

Small intestine bacterial overgrowth can often be detected by the hydrogen breath test (HBT). When SIBO is present, hydrogen and methane gas will appear in the breath as a result of abnormal fermentation of carbohydrates by the colonic bacteria in the small intestine. HBT can also be used to test lactose intolerance.

SIBO has been often observed in many patients with IBS and can be tied to many of the IBS symptoms. SIBO leads to abnormal fermentation in the small intestine which causes gas, bloating, characteristics of IBS. Other pathophysiological mechanisms of IBS such as altered motility, visceral hypersensitivity, and abnormal brain-gut interaction may also be explained by SIBO. Moreover, studies show that the treatment of SIBO relieves symptoms of IBS.

Diagnosing IBS

As each person will present differently and the symptoms of IBS can mimic many other conditions, diagnosing IBS can be difficult at times. The diagnosis will be based on patient-reported symptoms and stool patterns.

According to the guidelines of these criteria, patients with IBS patients will have the following symptoms:

  • Symptoms for at least six months 
  • Abdominal discomfort at least 3 days per month in the last 3 months
  • Along with some or all of these; change in either frequency or form of stool, abdominal discomfort that improves after going to that bathroom, the passage of mucus in stool

Tests used to confirm or rule out diagnosis

Hydrogen breath test (HBT), which is a non-invasive test used to for small intestinal bacterial overgrowth (called H.pylori) may be ordered. H.pylori is often thought to be related to IBS symptoms.

Blood testing and stool analysis may be ordered.

  • Blood tests include; WBC and Sedimentation rate. A high WBC would indicate possible infection and an elevated Sedimentation rate would indicate possible inflammation. Most of the time IBS will not test positive for these two.
  • A stool analysis would be used to rule out bleeding, parasites, etc

Colonoscopy, which is an invasive test where they insert a small camera into the anus and view the lower intestines may be ordered to monitor for any type of cell changes or breakdown in the integrity of the intestinal tract.

Treatment of IBS

Treatment of IBS should be based on both the underlying triggers such as food allergies or depression and the symptoms the patient presents with. Most IBS plans will include diet and lifestyle changes, stress modification, probiotics, and some medications.

Diet Changes and Lifestyle Changes

Most cases of IBS are mild and treatment is focused on diet and lifestyle changes such as stress modification and elimination of food allergies.

Diet: There are many diets aimed at reducing IBS symptoms, this is because patients often complain that their symptoms worsen upon consumption of certain types of foods. The tricky part is some of the food found to help symptoms in some people may worsen symptoms for others.

Studies show that 60% of IBS patients have symptoms following certain foods. Symptoms develop within 15 mins after eating for 28% and within 3 hours in 93%. Paying attention to how your body reacts to certain foods is key in choosing a diet.

High fiber is thought to help with constipation while low fiber is thought to help people with gas and diarrhea. On an elimination diet, you cut out groups of foods one at a time and see if your symptoms improve in order to identify foods that may be triggering symptoms. Going gluten-free is a common tactic to control IBS as gluten intolerance and sensitivity is on the rise and often linked to IBS.

A low FODMAP diet is also gaining traction in people who suffer from IBS. Some of the foods that may exacerbate IBS symptoms include wheat products, dairy products, peaches, citrus, apples, fried foods, legumes, onion, garlic, and food additives such as honey. These foods are rich in FODMAP.

Probiotics: Taking probiotics, which are healthy gut bacteria, is linked to improved symptoms of IBS. Probiotics are found in fermented foods such as yogurt, kimchi, sauerkraut, etc or can be taken as OTC supplements. 

Many studies have investigated the efficacy of probiotics in IBS patients, which is why it is considered a staple in the treatment of IBS. However, there is a discrepancy on factors such as bacterial strain, dose, dosage form.

Reduce Stress: Gut hypersensitivity is linked to stress so managing stress is needed. Meditation, yoga, going for a run, getting a message, or walking in nature are all activities that help to clear the mind.

Using heat therapy by taking a warm bath or applying heat to the abdomen is thought to sooth the stomach and nerves and improve symptoms as well.

It is important to identify and eliminate key stressors, be it physical or psychological. Antidepressants or anti-anxiety medication may be given if the medical provider deems it necessary.

Medications and Supplements

When diet and lifestyle changes are not enough to control symptoms, or an identified trigger is found, some of the following medications and supplements may be advised.

Antispasmodics and Anticholinergics: Medications such as Bentyl help to reduce cramping, but no clinical evidence has shown their effectiveness.

Antidiarrhea: Imodium can be taken for uncontrollable diarrhea.

Stool softeners and bulk-forming: Increased fiber through diet or supplements like Metamucil and stool softeners such as Colace can be used for constipation.

Antibiotics: Have been commonly used in the treatment of IBS. Typical antibiotics include neomycin, metronidazole, amoxicillin, and rifaximin. Rifaximin has been found very effective at improving symptoms of diarrhea-predominant IBS. 

Alternative medicine: Peppermint oil or tea, ginger, and mint are shown to reduce indigestion and discomfort.

Psychology medications: Anti-anxiety or antidepressants are shown to improve symptoms of IBS since gut and brain health are closely linked.


IBS remains a challenging condition to diagnose and treat. This is partly due to the fact that the exact underlying mechanisms and pathophysiology of IBS remains unclear. 

Studies have indicated that an altered gut microbial community plays an important role in the manifestation of IBS. While probiotics are helpful in balancing gut microbes in the stomach and improving symptoms, more research on doses and types are needed. Rifaximin, which is an antibiotic, also appears to be a promising candidate for the treatment of IBS due to its success in treating SIBO, which is an overgrowth of bad bacteria in the gut. When it comes to diet, studies show that allergy avoidance or low FODMAP diets are helpful for reducing symptoms.

Listening to your body, identifying and avoiding foods that trigger symptoms, reducing stress, and taking medications when needed is the best plan of care for symptom management.

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