Irritable Bowel Syndrome



Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder. It is the number one reason for a gastroenterology visit. IBS affects between 25 and 45 million people in the United States (10 to 15% of the population). About 2 in 3 IBS sufferers are female. IBS affects people of all ages, even children.

What are the different types of IBS?

There are 3 main types of IBS but 4 types in total. These are:

  • IBS with predominant diarrhea
  • IBS with predominant constipation
  • IBS with mixed (constipation and diarrhea)
  • IBS-unclassified.

How is IBS diagnosed?

The diagnosis of IBS is difficult because there are no specific tests to identify the disease. We rely on symptoms that are non-specific.  These symptoms often resemble symptoms of other serious conditions like colitis. Experts say that IBS is not a diagnosis of exclusion and that the diagnosis should be based on symptoms. This is not often reassuring to patients that are scared, have family members with cancer or IBD or patients that have previously suffered from a misdiagnosis or delayed diagnosis. For these patients; no testing at all is not an option. For some of these patients, a negative result from tests is reassuring.

The Rome IV criteria for the diagnosis of IBS are recurrent abdominal pain, on average, at least 1 day/week in the last 3 months, associated with two or more of the following criteria:

  • Related to defecation.
  • Associated with a change in frequency of stool.
  • Associated with a change in form (appearance) of stool.

The criteria should be fulfilled for the last 3 months but symptoms should be present at least 6 months before diagnosis.

Key to diagnosis

  • History
  • Physical examination
  • ESR, CRP, and fecal calprotectin in patients with persistent diarrhea. If positive, a colonoscopy may be warranted.
  • Celiac panel in patients with persistent diarrhea. If positive, a colonoscopy may be warranted.
  • Thyroid function test in appropriate individuals.
  • Stool studies in patients with persistent diarrhea and other features (e.g. travel history) to rule out infection or infestation.
  • Screening colonoscopy in age-appropriate persons if not previously done.
  • Diagnostic colonoscopy with random biopsies in patients with persistent diarrhea despite therapy.
  • Empiric therapy for bile acid malabsorption in suspected cases.
  • Breath test to rule out carbohydrate malabsorption in certain patients with persistent IBS with diarrhea despite treatment.
  • A test is not required to make the diagnosis of IBS.

What causes IBS?

The exact cause of IBS is unknown. The following pathophysiologic mechanisms have been proposed:

  • Abnormal motility: IBS patients appear to have an abnormal movement of the gut especially after a meal.
  • Visceral hypersensitivity: Patients with IBS have altered thresholds to pain within the GI tract.
  • Role of infection: About 10% of IBS patients develop the symptoms after experiencing infectious gastroenteritis. Salmonella, Shigella, and Campylobacter are usually involved but any infection including viral infection can be involved.
  • Role of inflammation: Inflammatory cells are sometimes seen in patients with IBS even in the absence of infectious gastroenteritis.
  • Role of bacterial overgrowth: IBS patients experience excessive fermentation and increased small bowel gas formation. Some patients with IBS with diarrhea have improvements in symptoms with antibiotics. All of these point to a potential role of small intestinal bacterial overgrowth (SIBO) in IBS.
  • Role of serotonin: The guts of patients with IBS contain low amounts of serotonin, the enzyme that synthesizes it, as well as a transporter that brings serotonin into cells.
  • Role of the brain-gut axis interaction: Disruption of the brain-gut communication has been implicated in IBS. Stress acts on the emotional limbic system leading to increased release of adrenocorticotropic hormone and cortisol. This leads to symptoms of IBS.
  • Role of the microbiota: Fecal analysis showed that people with IBS have an altered gut microbiota. They have more of the phylum Firmicutes and fewer of Bacteroidetes.


10 Myths about IBS

Myth 1: IBS is a psychological disorder. It’s just all in your head.

The Truth: IBS is a real disease. It is a functional disorder with no specific disease marker or diagnostic test.

Myth 2: IBS is just a minor bother.

The Truth: IBS patients feel miserable. IBS can affect all aspect of their lives. The economic impact of IBS is huge from reduced productivity, days off work, physician office visits, hospital visits, and diagnostic tests.

Myth 3: IBS is similar to IBD (inflammatory bowel disease).

The Truth: IBS is completely different from inflammatory bowel disease (ulcerative colitis or Crohn’s disease). There are specific tests for the diagnosis of IBD but not IBS. Unlike IBD, IBS do not cause bloody stool or anemia. IBS do not lead to surgeries.

Myth 4:  I have IBS. Treatment that works for someone will also work for me.

The Truth: No two IBS patients are the same. Treatment that works for one individual will not necessarily work for another. Treatment should be individualized.

Myth 5: All patients with IBS should be on gluten free diet.

The Truth: Some patients with IBS may have symptoms from food that contain gluten but complete avoidance of gluten should not be undertaken without consulting with a physician. IBS is different from celiac disease, a disease that requires complete abstinence from gluten.

Myth 6: IBS patient should not eat this particular food.

The Truth: Patients with IBS benefit from low FODMAP diet but there is no particular food that an IBS patient should avoid forever.

Myth 7: There is a test for IBS.

The Truth: There is no specific test for IBS yet. The diagnosis is based on symptoms and the exclusion of other diseases.

Myth 8: IBS can lead to cancer.

The Truth: IBS do not lead to cancer.

Myth 9: IBS is caused by anxiety and depression.

The Truth: What causes IBS is unclear. Several possible causes have been proposed. IBS patients may suffer from anxiety and depression but they are not the cause of IBS.

Myth 10: IBS do not affect men.

The Truth: IBS affect both men and women. IBS affects women more.

Treatment modalities

  • Lifestyle modification: exercise, stress reduction (yoga, meditation), sleep hygiene.
  • Psychological therapies: psychotherapy, hypnotherapy.
  • Dietary fiber: soluble fiber (psyllium or ispaghula husk) appear to be beneficial compared to insoluble fiber (bran). Certain forms of fiber especially bran can exacerbate bloating, distention and flatulence.
  • Dietary restrictions: Low FODMAP diet is the main diet for IBS. Some patients also report improvement with gluten free diet.
  • Medications: multiple medications have been approved by the FDA for symptoms of IBS.
  • Stool transplant: experimental.


Treatment of Symptoms of Irritable Bowel Syndrome

SymptomTherapyDrug and dose
DiarrheaOpioid agonistsLoperamide 2 - 4mg; when necessary titrate up to 16 mg/d
DietLow FODMAP diet
low or no gluten diet
Bile salt sequestrantscholestyramine (9 g bid - tid)
colestipol (2 g qd - bid)
colesevelam (625 mg qd - bid)
ProbioticsMultiple products available
AntibioticsRifaximin 550 mg tid X 14 days
5-HT3 antagonistsAlosetron (0.5 - 1 mg bid)
Ondansetron (4 - 8 mg tid)
Ramosetron 5 mg qd
Mixed opioid agonists/antagonistsEluxadoline 100 mg bid
Constipation Psylliumup to 30 g/d in divided doses
Polyethylene glycol (PEG) e.g. Miralax17 - 34 g/d
Chloride channel activatorsLubiprostone, 8 mg bid
Guanylate Cyclase C agonistsLinaclotide 290 mcg qd
Guanylate Cyclase C agonistsplecanatide (Trulance)
3mg q day
Abdominal pain Smooth muscle antispasmodicsdicyclomine (10-20 mg qd-qid)
Otilonium (40 80 mg bid tid)
Mebeverine (135 mg tid)
Peppermint oilEnteric-coated capsules, 250-750 mg, bid-tid
Tricyclic antidepressantsDesipramine (25-100 mg qhs)
amitriptyline (10-50 mg qhs)
SSRIsparoxetine (10 40 mg qd)
sertraline (25 100 mg qd)
citalopram (10 40 mg qd)
SNRI Duloxetine 30-90mg qd; Venlafaxine 150mg qd

What is low FODMAP diet?

FODMAP stands for :

F: Fermentable. These foods can be broken down by bacteria in your intestine.

O: Oligosaccharides. Examples are onions, soybeans, leeks, asparagus.

D: Disaccharides.  Examples are lactose in milk and diary products; sucrose in table sugar.

M: Monosaccharides. Examples are fructose in apple and honey.

A: And

P: Polyols. Examples are sorbitol and maltitol in sugar-free gums and mints.


Low FODMAP Diet for IBS

Food CategoryHigh FODMAP foodsLow FODMAP food alternatives
Breads and cerealRye, wheat-containing breads, wheat-based cereals with dried fruit, wheat pastaGluten-free bread and sourdough spelt bread, rice bubbles, oats, gluten-free pasta, rice, quinoa
VegetablesAsparagus, artichokes, onions(all), leek bulb, garlic, legumes/pulses, sugar snap peas, onion and garlic salts, beetroot, Savoy cabbage, celery, sweet cornAlfalfa, bean sprouts, green beans, bok choy, capsicum (bell pepper), carrot, chives, fresh herbs, choy sum, cucumber, lettuce, tomato, zucchini.
Protein sourcesLegumes/pulsesMeats, fish, chicken, Tofu, tempeh
FruitsApples, pears, mango, nashi pears, watermelon, nectarines, peaches, plumsBanana, orange, mandarin, grapes, melon
Milk and dairyCow’s milk, yoghurt, soft cheese, cream, custard, ice cream Lactose-free milk, lactose-free yoghurts, hard cheese
Nuts and seedsCashews, pistachiosAlmonds (<10 nuts), pumpkin seeds
Biscuits (cookies) and snacksRye crackers, wheat-based biscuitsGluten-free biscuits, rice cakes, corn thins
Seasonings and Condimentsblueberry jam, grape jelly, pickles, relish, onion powder, garlic powderrosemary, sage, soy sauce, thyme, turmeric, vanilla, pepper, chili, curry, basil, nutmeg, parsley, paprika, turmeric, wasabi, strawberry jam
Sweetenersmannitol, sorbitol, maltitol, agave, honeyaspartame, saccharine, maple syrup



How does FODMAP cause symptoms?

FODMAP are carbohydrates that are difficult to digest. They are fermented by gut bacteria leading to gas and bloating. The pull too much water causing diarrhea or too little water causing constipation.

Can low FODMAP diet help treat IBS?

Yes. Multiple studies show improvement in symptoms of IBS with low FODMAP diet. About 75% of IBS patients that follow the diet report improvement in their symptoms.

How to be on the low FODMAP diet

There are 2 phases to the low-FODMAP diet; the elimination phase and the re-introduction phase.

Elimination Phase: This is where you eliminate all high-FODMAP foods from your diet. This should be done in consultation with your physician and/or dietician. This phase usually lasts 2-6 weeks. You should feel at least 50% better before starting the re-introduction phase. If you do not feel better at all with the low FODMAP diet, discuss this with your physician.

Reintroduction Phase: After the elimination phase, you can start re-introducing individual high-FODMAP food back into your diet. You have to add high-FODMAP food one at a time to see if the food lead to symptoms (belly ache, bloating, gas, distention, diarrhea, constipation). If the food causes symptoms, it is eliminated forever. If it does not cause symptoms, then you can continue to eat it.  You should wait for at least 48 hours to assess symptoms and before adding another food back. You should add as many foods as possible back into your diet without bringing back symptoms. If you are able to eat some high FODMAP diet alongside low FODMAP diet, your diet is now a modified low-FODMAP diet.

The MONASH University Video on IBS

IBS and Fiber

Fiber may help patients with IBS.  Here are some facts about fiber and IBS:

  • The United States Department of Agriculture (USDA) recommends a minimum of 25-35 grams of fiber daily.
  • There are 2 types of fiber: soluble and insoluble fiber.
  • Soluble fiber draws water and turns to a gel inside the body. This slows digestion. Examples of soluble fiber are oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. It is also found in psyllium (found in Metamucil, Konsyl, etc.), methylcellulose (Citrucel).
  • Insoluble fiber does not dissolve in water but adds bulk to the stool. Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains.
  • When you begin a fiber regimen, start small and titrate up.
  • Space out your portions.
  • Hydrate adequately.

IBS and Probiotics

Probiotics are live microorganisms that provide health benefits to people in the right amounts. Examples include Lactobacillus, Bifidobacterium, Saccharomyces. Studies suggests that some patients may benefit from probiotics especially those with Bifidobacterium.

Yogurt and Probiotics

Yogurt BrandsBacteria Strains
YoplaitLactobacillus bulgaricus
Streptococcus thermophilus
Lactobacillus acidophilus
ChobaniLactobacillus acidophilus
Bifidobacterium bifidum
Lactobacillus casei
Stonyfield FarmsLactobacillus bulgaricus
Streptococcus thermophilus
Lactobacillus acidophilus
Bifidobacterium bifidum
Lactobacillus rhamnosus
Dannon Lactobacillus bulgaricus
Streptococcus thermophilus
Lactobacillus acidophilus
Bifidobacterium lactis DN-173 010 in Activia
Lactobacillus casei DN-114- 001 in DanActive
YakultLactobacillus casei Shirota
FageLactobacillus bulgaricus
Streptococcus thermophilus
Lactobacillus acidophilus
Bifidobacterium bifidum
Lactobacillus casei
Greek gods YogurtLactobacillus bulgaricus
Streptococcus thermophilus
Lactobacillus acidophilus
Bifidobacterium bifidum
Lactobacillus casei
La YogurtLactobacillus bulgaricus
Streptococcus thermophilus
Lactobacillus acidophilus
Bifidobacterium bifidum
Lactobacillus casei
Bifidobacterium animalis BB12
Voskos Greek YogurtLactobacillus bulgaricus
Streptococcus thermophilus
Lactobacillus acidophilus
Bifidobacterium bifidum
Lactobacillus casei

Patient Information Brochure on Irritable Bowel Syndrome [PDF and Printable]

Click HERE.


Yoga and IBS

Yoga has been studied in IBS and found to be helpful.. Read 5 Yoga poses for IBS.

IBS Apps

Apps can help you manage your IBS especially your diet. There are so many apps that can be downloaded to your phone, tablet, or watch. These include:

  • Monash University Low FODMAP diet.
  • FODMAP Friendly.
  • FODMAPs 1-2-3.
  • The Low FODMAP Diet for IBS.

Check your app stores (Google Play for Android and App Store for iOS) for listings.


Diaphragmatic Breathing 

Diaphragmatic breathing can help symptoms of IBS especially bloating.  An app BellyBio is a good tool for practicing diaphragmatic breathing. The app instructs you on how to do the breathing right.

Video on how to do diaphragmatic breathing



Hypnotherapy especially gut-directed hypnosis has been shown to be effective in the management of IBS. Gut-directed hypnosis can be performed by a trained therapist or by the patient himself or herself (self-directed). Hypnosis uses suggestions, imagery and relaxation to transform the mind away from the digestive problems into a calm and relaxed state of mind.  A trained therapist provides effective therapy in multiple sessions as well as guides for self-directed therapy at home.