Irritable Bowel Syndrome: What You Need to Know

Written by: Rebecca Goodrich, MS, RDN, LDN

Irritable bowel syndrome or commonly known as IBS is a functional bowel disorder that can be seen in 9%-23% of the population worldwide (1).

This disorder can affect people differently for many reasons. Functional bowel disorders can have a wide variety of symptoms that may include bloat, abdominal pain, excessive flatulence, and changes in bowel movements.

When seeking medical attention for possible IBS, it is important to rule out other conditions or “red flags” that might mimic IBS. Some conditions that may act similarly to IBS include celiac disease, inflammatory bowel disease (IBD) such as ulcerative colitis or Crohn’s disease, bile salt malabsorption, and even endometriosis. IBS can be diagnosed by a gastroenterologist by ruling out these similar conditions and by using the Rome IV criteria. IBS can come in many forms including IBS-C (constipation), IBS-D (diarrhea), IBS-M (mix of both constipation + diarrhea), and IBS-U (unclassified). Utilizing the Bristol stool chart can be helpful when determining the characteristic of your bowel movements and can help classify the type of IBS that is present. Having recurrent abdominal pain for at least 1 day a week, within the past 3 months, is part of the piece to solving the puzzle when diagnosing for IBS.

Diagnosed with Irritable Bowel Syndrome: Now What?

As a registered dietitian, I have seen many clients struggle with this debilitating condition. We have our good days, and then we have our bad days. The important thing to remember is that you are not alone! Once a proper IBS diagnosis has been made, it is suggested that the client works with a dietitian who specializes in IBS while using the low FODMAP diet approach to help alleviate symptoms. While there may be a few exceptions to using the low FODMAP diet, studies have shown the diet overall to be effective in managing symptoms (2).

Other treatments for IBS may also include controlling diarrhea with anti-spasmodic medications and using laxatives or 5-HT4 receptor agonist with constipation. There are many other therapies that can be used in conjunction with the low FODMAP diet such as biofeedback, exercise, cognitive behavioral therapy (CBT), and gut-directed hypnotherapy. Treatment should be individualized and communicated with the client and their physician.

Low FODMAP diet: The Phases

FODMAPs is an acronym that stands for Fermentable Oligo-Di-Monosaccharide and Polyols. FODMAPs are short-chain carbohydrates that are smaller in size, and due to their indigestible properties, are either slowly absorbed or not absorbed at all in the small intestine. For those with IBS, symptoms such as bloat, abdominal distention, excessive flatulence, and visceral hypersensitivity are commonly reported due to their intolerance to certain FODMAPs.

In 2005, Monash University created a low FODMAP diet and developed cut-off values for specific FODMAPs to help better understand the effects it has on managing IBS symptoms. The low FODMAP diet is broken down into 3 phases.

“1-Low FODMAP diet”

The first phase which is called “phase 1-Low FODMAP diet” is followed for about 2-6 weeks. During this phase, the goal is to gain symptom control and to have a clearer picture of what foods may be challenging for the client with IBS. Foods that are consumed during phase 1 are all low in FODMAPs according to their respectable serving sizes.

“2-FODMAP reintroduction”

Once phase 1 has been completed successfully, it is then recommended for the client to transition into a “Phase 2-FODMAP reintroduction” for roughly 6-8 weeks. During this phase, each FODMAP group is re-challenged separately and as tolerated. While this phase is being performed, it is important for both the client and dietitian to take note of the client’s tolerance level. Short-chain carbohydrates such as galactooligosaccharides (GOS), fructans, excess fructose, mannitol, sorbitol, and lactose are all challenged individually.

“3-FODMAP Personalization”

Once the dietitian and client both have a good understanding of the client’s tolerance to these FODMAPs, it is then recommended for the client to transition into the third phase which is “Phase 3-FODMAP Personalization.” In this last phase, the client is able to consume the foods that are well tolerated while having the tools to gain better symptom control.

Final Thoughts

IBS can often be confused with other possible underlying conditions due to its similarities with other well-known conditions. It is important to get diagnosed correctly from a physician in order to get the proper treatment plan. IBS symptom control is not a “one size fits all” approach. Some people may experience milder symptoms, while others can be severe. There are many resources that a person with IBS can explore when trying to manage their symptoms. Working with a registered dietitian who specializes in the 3-phased low FODMAP diet along with other approaches, as mentioned previously, can help with better symptom control.


  1. Saha, L. (2014). Irritable bowel syndrome: Pathogenesis, diagnosis, treatment, and evidenced-based medicine. World Journal of Gastroenterology. Jun 14; 20(22):6759-6773. https://doi:10.3748/wjg.v20.i22.6759
  2. Altobelli, E., Del Negro, V., Matteo Angeletti, P., Latella, G. (2017). Low-FODMAP Diet Improves Irritable Bowel Syndrome Symptoms: A Meta-Analysis. Nutrients. 9(9):940. https://doi:10.3390/nu9090940

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