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Irritable bowel syndrome (IBS) is the most common functional GI disorder.

Around 40% of sufferers experience mild IBS, 35% experience moderate IBS, and 25% experience severe IBS.

Although there are no specific biochemical or structural abnormalities associated with IBS, there are common symptoms, each of which has certain triggers. Understanding them can help you avoid triggers and minimize your symptoms.

We recommend a few products — for IBS symptoms — at the bottom of this page. But first, let’s learn more about the most common IBS symptoms and triggers.

Symptom: Abdominal pain and Cramping

Abdominal pain and cramping are among the most common symptoms associated with IBS.

Typically, digestion is controlled by the brain and gut working together. This involves a complex process between nerves, hormones, muscles, and signals released by the beneficial bacteria living in the gut.

For people who suffer from IBS, the signals are uncoordinated, resulting in severe tension in the muscles throughout the gastrointestinal tract. The pain could appear anywhere in the abdominal region. It may lessen after a bowel movement or the passing of flatulence. Pain may also be caused by the production of gas from carbohydrate fermentation.


Pain and cramping have several triggers. These include:

  • Meals high in fat
  • Large meals
  • Certain foods or drinks that may not be digested well, such as high FODMAP foods
  • Trapped gas
  • Visceral hypersensitivity

Some types of sugar, such as fructose and sorbitol, can also cause cramping because the intestine poorly absorbs them.

  • Fructose is a sweetener found naturally in some fruits and honey.
  • Sorbitol is a sweetener found in stone fruits and often used in gums and candies.

Avoiding these triggers can reduce pain and cramping, as can following a low FODMAP diet or a SIBO diet. This may also help improve other symptoms.

Symptom: Diarrhea

Diarrhea-predominant IBS affects around 30% of IBS sufferers. In a 2003 study published in the World Journal of Gastroenterology, it was shown that adults who suffer from diarrhea-predominant IBS have an average of twelve bowel movements per week — more than twice the amount for adults who do not suffer from IBS. (Portincasa, 2003)

IBS often causes an acceleration in the movement of waste through the intestines, which can result in a sudden and immediate urge to have a bowel movement. In diarrhea-predominant IBS, the stool is often watery and contains mucus.

Triggers: Stress and Anxiety, Pathogens, Excess Serotonin, Certain Foods

The human response to stress is a complex process. It involves a combination of processes within the endocrine and nervous systems. These processes trigger several changes within the body including heart rate, blood pressure, muscle tension, and the functioning of the bowel. It is the latter which links IBS to the stress response.  

When you are under stress, your brain sends out signals which trigger two main types of body responses. One is the release of hormones, particularly cortisol. The other is the release of adrenaline and noradrenaline, which cause changes in the digestive and muscular systems. The combination of hormones, adrenaline, and noradrenaline also stimulates the nerves in the bowel.

Excess serotonin in the gut may also be released due to stress, and the particular makeup of the microbiome also influences serotonin production. Serotonin is required for adequate movement in the gut — but high levels can cause diarrhea.

This results in a delay in stomach emptying, and an increase in contractions of the colon. These, in turn, can cause diarrhea and exacerbate other symptoms of IBS.

Pathogens, such as E.coli, Giardia and Cryptosporidium, can also cause diarrhea, which is a natural response to expel their toxins.

Certain foods and drinks may also irritate the gut, causing diarrhea. These include coffee, alcohol and spicy foods.

Symptom: Constipation

Constipation-predominant IBS affects around 50% of sufferers. (Mearin, 2003)

When communication between the brain and the gastrointestinal tract becomes distorted, this can slow down the normal transit time of the stool.

When the process is slowed down, the intestinal tract absorbs more water from the stool, making it more difficult to pass. The result is fewer regular bowel movements.

Medically, constipation is diagnosed when a person has fewer than three bowel movements per week. Functional constipation — chronic constipation not caused by an underlying disease — is not associated with IBS. The difference is that constipation in IBS can often be very painful, though the pain usually subsides after a bowel movement.

Because constipation in IBS often leaves sufferers with the feeling of an incomplete bowel movement, it can lead to straining which may result in hemorrhoids.

Triggers: Insufficient Fluids or Fiber, Hypothryoidism, Excessive Methane Gas

A diet rich in natural fiber can benefit you if you suffer from constipation-predominant IBS. Fiber is known to regulate bowel movements. Good sources of natural fiber include gluten-free grains, fruits, vegetables, and legumes.

Try to incorporate some fiber into each of your meals but add it a little at a time to avoid bloating. Here are some excellent sources of fiber:

  • Black beans
  • Buckwheat
  • Lentils
  • Fresh fruits
  • Fresh vegetables
  • Soybeans
  • Yams
  • Oats

Drinking plenty of water throughout the day to stay hydrated will keep bowel movements regular. Daily exercise — at the same time each day — can also help to improve IBS-related constipation and improve bowel habits.

If your constipation isn’t resolved with the steps above, assessment of thyroid function and SIBO investigation is worthwhile.

Symptom: Alternating Constipation and Diarrhea

Around 20% of IBS sufferers experience alternating periods of constipation and diarrhea. (Thorpe, 2017)

Symptoms of mixed IBS vary from one individual to another. However, you may continue to experience other symptoms throughout these phases.

Pain typically subsides after a bowel movement. The symptoms of mixed IBS tend to be more frequent and more severe than with other forms of IBS.

Trigger: An Imbalance of Gut Bacteria

Gut bacteria play an important role in the maintenance of IBS symptoms. You can compensate for an imbalance of gut bacteria by taking a probiotic supplement. Some of the best probiotics strains for IBS include:

Nutritional experts recommend trying a probiotic strain for four weeks. If you see no change in symptoms, switch to a different strain.

Symptom: Gas and Bloating

Because IBS alters the rate of digestion, this can lead to the production of more gas in the gut, leading to uncomfortable bloating. For many IBS sufferers, bloating is one of the most persistent and annoying symptoms.  

In a 2009 study published in Clinical Gastroenterology and Hepatology, 83% of patients included experienced bloating. This symptom was more common in women suffering from mixed or constipation-predominant IBS. (Ringel, 2009)

Trigger: Beans, Legumes and High FODMAP Foods

Although high FODMAP foods such as beans and legumes can be helpful for people with constipation-predominant IBS, for others, they can trigger uncomfortable bloating and gas. This is because these food items contain carbohydrates that often do not digest well.

When they are poorly digested, they are fermented by bacteria in the gut and cause gas and bloating. If you experience gas and bloating as a symptom of your IBS, it may help to avoid the following foods:

  • Chickpeas
  • Baked beans
  • Butter beans
  • Black-eyed peas
  • Lima beans
  • Soybeans

Lentils are better tolerated than other legumes — especially in smaller amounts.

You can also reduce gas and bloating by following a low FODMAP diet and avoiding lactose.

Once you begin to familiarize yourself with specific IBS triggers, you can start to make dietary and lifestyle changes to keep your symptoms to a minimum and improve your digestive system and your bowel habits.

This will not only make you feel healthier; it will also reduce the risk of unwanted weight loss.

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Research Citations

  • Portincasa P, Moschetta A, Baldassarre G, Altomare DF, Palasciano G. Pan-enteric dysmotility, impaired quality of life and alexithymia in a large group of patients meeting ROME II criteria for irritable bowel syndrome.World journal of gastroenterology. 2003 Oct;9(10):2293-9. DOI: 10.3748/wjg.v9.i10.2293
  • Mearin F, Balboa A, Badía X, Baró E, Caldwell E, Cucala M, Díaz-Rubio M, Fueyo A, Ponce J, Roset M, Talley NJ. Irritable bowel syndrome subtypes according to bowel habit: revisiting the alternating subtype. European journal of gastroenterology & hepatology. 2003 Feb;15(2):165-72. DOI: 10.1097/01.meg.0000049985.90403.87.
  • Thorpe M. 9 Signs and Symptoms of Irritable Bowel Syndrome (IBS), Healthline. July 19, 2017.
  • Ringel Y, Williams RE, Kalilani L, Cook SF. Prevalence, characteristics, and impact of bloating symptoms in patients with irritable bowel syndrome. Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association. 2009 Jan;7(1):68-72; quiz 3. doi: 10.1016/j.cgh.2008.07.008.
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