IBD vs IBS: What’s the Difference?

Co-written by Ranjani Priya Ravinuthala

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are two distinct gastrointestinal disorders, though the differences between the two can be confusing for many people. Although some of the symptoms may be similar, these two health conditions are VERY different. The intention of this blog is to compare both conditions, as well as demonstrate how nutritional recommendations are different for each condition.

Irritable bowel syndrome (IBS)

What is IBS?

IBS is characterized by unexplained abdominal discomfort or pain that is associated with changes in bowel habits. Other common symptoms include gas, bloating, diarrhea and constipation, and increased GI distress associated with psychological and social stress.

Irritable bowel syndrome is a functional GI disorder [1]. This means that the condition is caused by changes in the way the GI tract works, as opposed to a physical abnormality in the GI tract (like in Crohn’s disease or ulcerative colitis [UC]).

An up close image of a healthy colon from the view of a colonoscopy.

So you can see in the endoscopy image above, the IBS GI tract looks normal…there’s no physical damage here with IBS. Because tests show no diagnostic abnormalities, diagnosis depends on symptoms.

How common is IBS?

An estimated 10-20% of the United States population has IBS [2], with about twice as many women as men being affected [3].

IBS Subtypes

IBS subtypes are based on the predominant bowel habits and stool form [4].


  • Irritable Bowel Syndrome with increased symptoms of watery stools and diarrhea is known as IBS-D.


  • Irritable Bowel syndrome with constipation is another common form of IBS which is associated with passing hard stools. People experience gas, bloating, straining, painful bowel movements and abdominal pain.


  • IBS-M is mixed IBS is irritable bowel syndrome mixed which is going back and forth with diarrhea and constipation.


  • IBS-U, or Unclassified IBS is defined as a patient who meets diagnostic criteria for IBS but whose bowel habits cannot be accurately categorized into the other 3 subgroups. This is when the patient reports that they rarely have abnormal stools.

Medical Management of IBS

  • There is no specific therapy that works for all people with IBS. Generally, the treatment option is determined by the predominant bowel pattern and the symptoms that most disrupt the patient’s quality of life.
  • For example, different medications, dietary interventions, and/or mind-body therapies would be recommended if a person has IBS-D compared with IBS-C.
  • Many people find that with these changes, symptoms improve and are able to be managed for long periods of time. [5]

Nutrition for IBS

Just as there is no single therapy for treating IBS, it’s important to remember there’s no single dietary strategy either. [67] However, a growing amount of research suggestions that the low-FODMAP diet is an eating pattern that has improved symptoms and quality of life for many people with IBS.

What is the Low FODMAP Diet?

The term FODMAPs was coined by a group of Australian researchers who theorize that foods containing these forms of carbohydrates worsen the symptoms of some digestive disorders such as IBS. [8]

The low-FODMAP elimination diet is based on limiting certain short-chain carbohydrate-containing foods, including sugars, starches, and fibers that some people can’t fully digest and absorb. These short-chain carbohydrates are poorly absorbed in the small intestine, resulting in gas, pain, and diarrhea in sensitive individuals. [9]

Evidence started building in the 1980s and 1990s for restricting poorly absorbed short-chain carbohydrates to provide symptomatic relief of IBS symptoms. The first research trial confirming the role of a low-FODMAP diet in managing GI complaints was a 2006 retrospective audit of patients with IBS and fructose malabsorption following a low-fructose/fructan diet. In this trial, 74% of patients reported symptomatic improvement on the diet. [10]

Since this study, more details on food composition have become available to fine-tune the low-FODMAP approach, including a broader range of FODMAP-containing foods. More recently, a questionnaire was completed for patients who received either standard dietary advice for symptom control of IBS that we just explored or low-FODMAP dietary advice. Significantly more patients in the low-FODMAP group experienced improvements in bloating, abdominal pain, and flatulence compared with the standard diet group.

Nutritional Deficiencies Common in IBS

It is important to be aware that common nutritional deficiencies can arise with the low FODMAP diet if foods that are eliminated are not substituted with comparable items. [1112] Common nutritional deficiencies include:

  • folate, thiamin, and vitamin B6 (from limiting cereals and breads)
  • calcium and vitamin D (from avoidance of dairy products)

Fiber for IBS

  • Although increasing fiber intake is a usual component of initial therapy for IBS, you’ve got to be careful about the type of fiber consumed, because people with IBS may develop symptoms possibly related to the type of fiber consumed.
  • For example, research has demonstrated that for IBS constipation management, you want to go for a combination of soluble and insoluble fiber. But for IBS-Diarrhea, increasing the amount of insoluble fiber in the diet may worsen IBS symptoms. [13]

Probiotics for IBS

  • Some studies suggest that probiotic supplements, especially those with certain strains like Bifidobacterium infantis, may help alleviate abdominal pain, bloating, and irregular bowel movements experienced with IBS. [141516]
  • Some examples of probiotic supplements for people with irritable bowel syndrome could include Align, Bio-K+® BiomePRO, Bio-Kult, or FloraVantage Balance. [17]

Peppermint Oil for IBS

  • Recent studies have shown that peppermint oil can be used to treat both overall symptoms and pain. [18] This treatment may be used either daily or as needed.
  • Peppermint oil can be found in the form of teas, drops, gels, and capsules. There have not been any specific trials comparing one form to another.
  • Side effects are uncommon but can include heartburn and nausea. These may be reduced by using a coated form, as coated pills minimize the activity of the peppermint oil in the stomach.

Inflammatory Bowel Disease (IBD)

Inflammatory bowel disease is an umbrella term used to describe conditions that involve chronic inflammation of the digestive tract. The two major forms of inflammatory bowel disease, or IBD, are Crohn’s disease and ulcerative colitis, or UC.

How Common is IBD?

  • An estimated 1.3% (or 3 million) of US adults reported being diagnosed with IBD.
  • The onset of IBD occurs most often in patients 15-30 years of age, but it is becoming more prevalent in the elderly.
  • Men and women are equally likely to be affected by the disease.
  • The disease is most common among people of eastern European backgrounds, but there have been an increased number of cases of IBD reported in Hispanic, African American, and Asian populations in recent years.
  • IBD occurs more commonly in developed areas of the world, in urban compared with rural environments. These findings could be partly explained by increased access to health care and better medical records in more developed than less developed countries. But the prevalence and incidence is increasing as IBD emerges as a global disease.

How are Crohn’s disease and ulcerative colitis different?

An image that compares inflammation in the intestinal tract in Crohn's disease versus inflammation in the intestinal tract of ulcerative colitis.
Image courtesy of the Crohn’s and Colitis Foundation
  • Crohn’s disease may involve any part of the GI tract from mouth to anus, but approximately 50-60% of cases involve the distal ileum and the colon.
  • In UC, disease activity is limited to the large intestine and rectum.
  • In Crohn’s disease, segments of inflamed bowel may be separated by healthy segments, whereas in UC the disease process is continuous.
an image that compares a healthy colon to moderate and severe colitis

In inflammatory bowel disease, the inflammatory response results in gastrointestinal tissue damage. So here, in this second image, you can see the image of a healthy colon on the left, remember that’s what IBS looked like…but looking at the moderate and severe colitis here, you can see that tissue damage or destruction has occurred.

  • The clinical course of the disease may be mild and episodic, or severe and unremitting.

Medical Management of IBD

  • The goals of treatment in IBD are to induce and maintain remission and to improve nutrition status.
  • Currently, the most effective medical agents include corticosteroids, anti-inflammatory agents, immunosuppressive agents, antibiotics, and anti-TNF agents.

Surgical Management of IBD

In Crohn’s disease, surgery may be necessary to repair strictures or remove portions of the bowel when medical management fails. Approximately 50-70% of persons with Crohn’s disease undergo surgery related to the disease. Surgery does not cure Crohn’s disease, and recurrence often occurs within 1 to 3 years of surgery. The chance of needing subsequent surgery in the patient’s life is approximately 30-70%, depending on the type of surgery and the age of the first operation.

This is important from a nutritional perspective because major resections of the intestine may result in varying degrees of malabsorption of fluid and nutrients.

an image of nutrient absorption sites
Image courtesy of Dietitians on Demand
  • For example, in the majority of Crohn’s cases, the disease activity occurs in the ileum. So if a patient needs the majority her ileum removed, she may need to get her vitamin B12 lab values checked regularly.

With UC, approximately 20% of patients have a colectomy (removal of the colon), and this actually resolves the disease because without the colon, there is no more colon to be chronically inflamed. Whether a colectomy is necessary depends on the severity of the disease and indicators of increased cancer risk. After a colectomy for UC, surgeons may create an ileostomy with an external collection pouch or an internal abdominal reservoir fashioned with a segment of ileum or an ileoanal pouch, which spares the rectum, to serve as a reservoir for stool.

Nutrition for IBD

  • As you can imagine, people with IBD are at increased risk of nutrition problems for a host of reasons related to the disease and its treatment. And medical nutrition therapy can look very different for a person depending on their specific situation. 
  • For example, if someone with Crohn’s has a stricture, the nutritional recommendations are going to look different than someone with UC who just had a colectomy and now has an ostomy.

Diets for IBD?

As of right now, there is no single diet or eating pattern for reducing symptoms or decreasing the flares in all people with IBD. 

An image of a venn diagram depicting different elimination diets considered for Crohn's disease and ulcerative colitis.

Here’s a Venn Diagram I made with the variety of eating patterns from nutritional research publications that are starting to be studied in greater detail. These elimination diets may work for some people, as research methods are improving, and some are showing some promising results. But these eating patterns can also be very restrictive, and none of these diets have been proven to work for everyone with IBD.

What we know right now is that many people with IBD report specific, individualized food triggers or intolerances. [19] But different guts tolerate different foods differently with this condition!!!

A good example of this is my husband with Crohn’s…he is completely lactose intolerant…we learned that even the tiniest amount of lactose is going to cause him a bad time. But I have worked with many clients who tolerate dairy fine, and one client even tolerated dairy products BEST! So at this time, it appears that different guts tolerate different foods differently!

Common Trigger Foods for IBD

Now I just made a big fuss that food triggers are different for each gut with IBD…but there are several common food triggers that have been reported amongst people with IBD [20], as well as ones I’ve seen in my practice. And they are:

  • red meat, alcohol, foods that are high in dietary fiber and fat, carbonated beverages, and excessive intake of lactose, fructose, or sorbitol.

This list of common food triggers could come in handy if you’re newly diagnosed with IBD or are feeling really confused about foods that could be exacerbating symptoms. But at the end of the day, not everyone with IBD experiences symptoms with these foods. And that if you feel okay with most of these foods, then there is no need to eliminate them from the diet forever.

Also, something to keep in mind is that the same foods that are responsible for GI symptoms in a normal, healthy population are likely to be triggers for the same symptoms in patients with mild stages of IBD or those in remission. For example, beans are gas-producing (the magical fruit!), they are gas-producing for a lot of guts out there.

Malnutrition and IBD

We can’t talk about IBD without talking about the HUGE risk for malnutrition. We care so much about malnutrition for IBD because it leads to poorer disease outcomes. Even mild cases of malnutrition can make it more difficult for the body to bounce back after an illness. [21] Malnutrition compromises digestion and absorption function in the GI tract and can cause growth delays in children with IBD [22].

Some of the reasons why malnutrition is so prevalent in people with IBD are:

  • complications experienced from the condition: abscesses, fistulas, strictures, ostomies, and beyond. This blog won’t be diving deep into the nutrition recommendations for each of these complications, but it can be very confusing for a patient to know what to eat if she develops a complication like this.
  • medication side effects: IBD warriors may be taking quite an extensive list of prescription medications, many of which have big nutritional side effects.
  • reduced intake of food: either during a flare from increased symptoms or from a fear of food brought on by a fear of negative consequences after eating said food.

So all of these reasons can lead to an overly restricted diet and increases the likelihood of malnutrition and weight loss.

Nutrient Deficiencies Commonly Found in IBD:

  • 60-75% of people with IBD will experience one or more deficiencies.
  • Several nutrient deficiencies are common for both Crohn’s disease and UC, like iron, folate, magnesium, calcium, and potassium. However, in Crohn’s disease, because the inflammation and disease process affect the small intestine and not just the colon, additional nutrient deficiencies like vitamin B12, vitamins A, D, E, and K, and zinc are commonly deficient. [23]
  • I can share that iron, vitamin D, and B12 are the big three deficiencies I see over and over again in my private practice.

Nutritional Recommendations for IBD

Small, frequent meals

  • Smaller portions consumed at more frequent intervals throughout the day are usually better tolerated by the gut. 
  • Also, small, frequent meals can also maximize nutritional intake as it provides the patient with more opportunities to fit in nutrient-dense foods throughout the day.


  • Protein has many roles in the body, like helping to repair the body’s tissues and keeping the immune system strong. 
  • People with IBD have increased protein needs – for weight gain and to restore losses after an acute flare, protein needs may be increased by 50 percent! 
  • Needs are also increased if taking corticosteroid medications like prednisone.


  • A low-residue or low-fiber diet is often prescribed by the GI doctor during a flare to decrease stool output and minimize pain and symptoms as fiber passes through the GI tract. 
  • So how low is low for a low-fiber recommendation? The answer is: it can depend on the severity of the condition. For example, for a mild to moderate flare, under 13 grams of fiber per day could be appropriate. But with even more severe circumstances, even less fiber per day may be recommended under medical supervision.

Side bar about fiber: in my professional experience, even though people with IBD are recommended to decrease fiber during a flare, they are hardly ever given recommendations or guidance to gradually re-introduce foods with fiber when they’re feeling better. This is a shame because more fiber may actually decrease the number of flare-ups a patient has, keeping them in remission for longer. [24]

In the fiber re-introduction process, I would recommend educating patients on the differences between soluble and insoluble fiber, as a patient may be able to tolerate soluble fiber better during their reintroduction journey at first.

In the fiber re-introduction process, I would recommend educating patients on the differences between soluble and insoluble fiber, as a patient may be able to tolerate soluble fiber better during their reintroduction journey at first.


  • Interestingly, the incidence of lactose intolerance is not higher than in the IBD population than the general population [25]. 
  • But lactose intolerance causes gas, bloating, cramping and diarrhea 30 to 90 minutes after consuming the dairy product. So if a person is already flaring, then this recommendation can just prevent additional symptoms.


  • Omega-3 fatty acid supplements in Crohn’s disease may significantly reduce disease activity. 
  • Use of omega-3 fatty acids or fish oil supplements in UC appears to result in a significant medication sparing effect, with reductions in disease activity and increased time in remission reported. [26]


  • Probiotic foods and supplements have been investigated as potential therapeutic agents for IBD because of their ability to modify the gut microbiota and potentially modulate gut inflammatory response. [27]
  • Multistrain probiotic supplements like VSL#3 have been shown to be beneficial in maintaining disease remission in patients with UC who had pouchitis, inflammation in the ileal pouch surgically formed after colectomy. [28] But a different probiotic supplement at a lower dose did not significantly reduce symptoms. Specific probiotic supplements also appear to be useful for induction and extension of remissions in pediatric and adult UC.
  • However, probiotic studies have not demonstrated significant improvement in Crohn’s disease activity in adults or pediatric patients, nor do probiotic supplements appear to prolong remission in Crohn’s disease.

Want more info about nutrition for IBD? 

Learn more about the virtual Eating for Crohn’s & Colitis Remission Program.


1. National Institutes of Health. Irritable Bowel Syndrome. Bethesda, MD: National Digestive Diseases Information Clearinghouse; accessed 2021. Publication No. 12-693.

2. International Foundation for Gastrointestinal Disorders. Accessed November 10, 2021. https://aboutibs.org/what-is-ibs/facts-about-ibs/statistics/

3. Kim YS, Kim N. Sex-Gender Differences in Irritable Bowel Syndrome. J Neurogastroenterol Motil. 2018;24(4):544-558. doi:10.5056/jnm18082

4. The Rome Foundation. Accessed November 29th, 2021. https://theromefoundation.org/rome-iv/rome-iv-criteria/

5. Saha L. Irritable bowel syndrome: pathogenesis, diagnosis, treatment, and evidence-based medicine. World J Gastroenterol. 2014;20(22):6759-6773. doi:10.3748/wjg.v20.i22.6759

6. Palmer S. Soothing the symptoms of IBS with diet therapy. Today’s Dietitian. 2009;11(6):34.

7. Irritable bowel syndrome. Academy of Nutrition and Dietetics website. https://www.eatright.org/health/wellness/digestive-health/irritable-bowel-syndrome. Reviewed March 2021. Accessed November 12, 2021.

8. Gibson PT, Shepherd SJ. Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach. J Gastro Hep. Vol 25:2. 28 Jan 2010. https://doi.org/10.1111/j.1440-1746.2009.06149.x

9. Barrett JS, Gibson PR. Fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) and nonallergic food intolerance: FODMAPs or food chemicals? Therap Adv Gastroenterol. 2012;5(4):261-268.

10. Staudacher HM, Whelan K, Irving PM, Lomer MC. Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. J Hum Nutr Diet. 2011;24(5):487-495.

11. Wendy Marcason, What Is the FODMAP Diet?, Journal of the Academy of Nutrition and Dietetics, Volume 112, Issue 10, 2012, Page 1696, ISSN 2212-2672, https://doi.org/10.1016/j.jand.2012.08.005.

12. Monash University Department of Gastroenterology, Monash University 3-Step FODMAP Diet Guide. Website: https://www.monashfodmap.com/3_step_fodmap_diet/. Published 2019.

13. Bijkerk CJ, de Wit NJ, Muris JW, Whorwell PJ, Knotterus JA, Hoes AW. Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trial. BMJ. 2009;339:b3154.

14. Whorwell PJ, Altringer L, Morel J, et al. Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome. Am J Gastroenterol. 2006;101(7):1581-1590.

15. Aragon G, Graham DB, Borum M, Doman DB. Probiotic therapy for irritable bowel syndrome. Gastroenterol Hepatol (NY). 2010;6(1):39-44.

16. Moayyedi P, Ford AC, Talley NJ, et al. The efficacy of probiotics in the treatment of irritable bowel syndrome: a systematic review. Gut. 2010;59(3):325-332.

17. Clinical Guide to Probiotic Products Available in USA. Applications, Dosage Forms and Clinical Evidence to Date. 2021 Edition. Accessed November 29th, 2021. http://www.usprobioticguide.com/PBCAdultHealth.html?utm_source=adult_ind&utm_medium=civ&utm_campaign=USA_CHART

18. Weerts ZZRM, Masclee AAM, Witteman BJM, Clemens CHM, Winkens B, Brouwers JRBJ, Frijlink HW, Muris JWM, De Wit NJ, Essers BAB, Tack J, Snijkers JTW, Bours AMH, de Ruiter-van der Ploeg AS, Jonkers DMAE, Keszthelyi D. Efficacy and Safety of Peppermint Oil in a Randomized, Double-Blind Trial of Patients With Irritable Bowel Syndrome. Gastroenterology. 2020 Jan;158(1):123-136. doi: 10.1053/j.gastro.2019.08.026. Epub 2019 Aug 27. PMID: 31470006.

19. Wędrychowicz, Zając,&Tomasik. (2016). Advances in nutritional therapy in inflammatory bowel diseases: Review. World Journal of Gastroenterology, 22(3), 1045-66.

20. Hou JK, Lee D, Lewis J. Diet and inflammatory bowel disease: review of patient-targeted recommendations. Clin Gastroenterol Hepatol. 2014;12(10):1592-1600. doi:10.1016/j.cgh.2013.09.063

21. Balestrieri P, Ribolsi M, Guarino MPL, Emerenziani S, Altomare A, Cicala M. Nutritional Aspects in Inflammatory Bowel Diseases. Nutrients. 2020;12(2):372. Published 2020 Jan 31. doi:10.3390/nu12020372

22. Ishige T. Growth failure in pediatric onset inflammatory bowel disease: mechanisms, epidemiology, and management. Transl Pediatr. 2019;8(1):16-22. doi:10.21037/tp.2018.12.04

23. Owczarek D, Rodacki T, Domagała-Rodacka R, Cibor D, Mach T. Diet and nutritional factors in inflammatory bowel diseases. World J Gastroenterol. 2016 Jan 21;22(3):895-905. doi: 10.3748/wjg.v22.i3.895. PMID: 26811635; PMCID: PMC4716043.

24. Carol Brotherton et al, Avoidance of Fiber is Associated with Greater Risk of Crohn’s Disease Flare in a 6-Month Period. Journal of Clinical Gastroenterology and Hepatology, 2016. DOI: https://doi.org/10.1016/j.cgh.2015.12.029

25. Szilagyi, A., Galiatsatos, P. & Xue, X. Systematic review and meta-analysis of lactose digestion, its impact on intolerance and nutritional effects of dairy food restriction in inflammatory bowel diseases. Nutr J 15, 67 (2015). https://doi.org/10.1186/s12937-016-0183-8 

26. Lev-Tzion, R., Griffiths, A., Leder, O.,&Turner, D. (2014). Omega 3 fatty acids (fish oil) for maintenance of remission in Crohn’s disease. The Cochrane Database of Systematic Reviews, (2), CD006320.

27. Ghouri YA, Richards DM, Rahimi EF, Krill JT, Jelinek KA, DuPont AW. Systematic review of randomized controlled trials of probiotics, prebiotics, and synbiotics in inflammatory bowel disease. Clin Exp Gastroenterol. 2014 Dec 9;7:473-87. doi: 10.2147/CEG.S27530. PMID: 25525379; PMC 4266241.

28. Holubar et al, Treatment and prevention of pouchitis after ileal pouch‐anal anastomosis for chronic ulcerative colitis. Cochrane Library, 2010; 6. DOI: 10.1002/14651858.CD001176.pub2


About the Author

Danielle Gaffen, MS, RDN, LD

Danielle Gaffen, MS, RDN, LD

Understanding the link between nutrition and gut disease prompted me to obtain my master’s degree in Nutritional Sciences at San Diego State University and become an IBD Registered Dietitian Nutritionist. Now I work with people who have Crohn’s and colitis who are struggling with confusion around what to eat. My favorite part is helping them to build confidence to eat without fear while managing their symptoms.

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