Irritable Bowel Syndrome (IBS)

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    Gabrielle Fundaro, Katie Jantz

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    Nick Milazzo, Shyam Jayaraman
    Last Updated: October 13, 2024

    Irritable Bowel Syndrome (IBS) is a common functional disorder of the large intestine characterized by long-term changes in bowel habits (e.g., frequent diarrhea or constipation) and abdominal pain. The exact causes are unknown, but research suggests that multiple factors — such as the gut-brain axis, abnormal muscular contractions, and gut microbes — could play a role in the disease. IBS can be managed with dietary modifications, psychotherapy, supplements, and prescription medications.

    Irritable Bowel Syndrome (IBS) falls under the Gut Health category.

    34 references on this page
    687,624 participants in 21 trials and 5 meta-analyses

    What is IBS?

    IBS is a common functional disorder of the large intestine that affects an estimated 20% of the global population, with a significant negative impact on quality of life and high co-occurrence with anxiety and depression.[1] IBS is twice as common in women compared to men, which could be explained, in part, by genetics and hormonal changes during the menstrual cycle.[2]

    IBS can be classified into three different subtypes: diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), or mixed (IBS-M). If it occurs after a gastrointestinal infection, such as food poisoning, it’s considered post-infectious IBS.[3]

    What are the main signs and symptoms of IBS?

    The main signs and symptoms of IBS include long-term changes in bowel habits (lasting months), abdominal pain, bloating, mucus in the stool, and a feeling of incomplete evacuation after having a bowel movement.[3]

    How is IBS diagnosed?

    The Rome IV criteria can be used to diagnose IBS based on the proportion of bowel movements rated as constipation or diarrhea compared to those rated as normal. Symptoms need to occur at least once per week for at least three months to be considered IBS.[4] However, there is no exact test for IBS, so a doctor (often a gastroenterologist) may need to rule out other potential diseases with blood and stool tests, and they might also perform a colonoscopy.[3]

    What are some of the main medical treatments for IBS?

    Medications for diarrhea-predominant IBS include antidiarrheals that reduce intestinal motility (organized contractions of the digestive tract) and reduce water content in the bowel. Doctors may also prescribe antibiotics to treat underlying infections or small intestinal bacterial overgrowth (SIBO). Drugs for constipation include over-the-counter laxatives or prescriptions that increase water content in the bowel or enhance intestinal motility. Antidepressants or antispasmodics can be used to normalize intestinal motility.[3]

    Have any supplements been studied for IBS?

    Several supplements have been studied and supported by strong evidence for the relief of certain IBS symptoms. Enteric-coated peppermint oil can reduce abdominal pain, and certain probiotic strains are effective for multi-symptom relief.[5][6] Polymethylsiloxane polyhydrate — an over-the-counter intestinal adsorbent — may also relieve multiple IBS symptoms.[7] One study has shown that glutamine supplementation may improve the symptoms of post-infectious IBS.[8] Prebiotics (carbohydrates used preferentially by beneficial gut microbes) aren’t clearly effective, however, and the benefits of other alternatives like traditional Chinese medicinal herbs or aloe vera need to be confirmed in higher-quality studies.[9]

    How could diet affect IBS?

    Many soluble fibers can be fermented by gut microbes to produce energy, resulting in by-products such as short-chain fatty acids and gas. The combination of fermentability and solubility can lead to accumulated gas and water retention in the colon, which can worsen abdominal pain and diarrhea. The low-FODMAP diet has been shown to reduce diarrhea-predominant IBS symptoms, and traditional dietary advice (such as avoiding trigger foods, limiting alcohol, and eating smaller, more frequent meals) is similarly effective.[10]

    Should certain foods be avoided for IBS?

    Can a high-fiber diet help with IBS?

    Are there any other treatments for IBS?

    Cognitive behavioral therapy provided modest IBS symptom improvement (similar to other forms of psychotherapy) in a small number of studies.[11] Hypnotherapy has also been found to help about 50% of the participants in the few studies that have been performed.[12] Psyllium husk is an over-the-counter fiber supplement that can normalize stool and reduce symptoms in IBS.[13] Acupuncture has also been studied, but it was no more effective than the sham (or placebo) treatment, so its benefits are very likely due to the placebo effect.[14]

    How does physical activity affect IBS?

    What causes IBS?

    The causes of IBS are unknown, but research indicates a number of factors are involved, including abnormal gut-brain axis communication, visceral hypersensitivity and altered motility, and the gut microbiota. Miscommunication between the brain and the gut could cause abnormal intestinal motility and visceral hypersensitivity, leading to changes in bowel function and abdominal pain. One form of IBS can be brought on by a gastrointestinal infection, and many symptoms of IBS also occur with small-intestinal bacterial overgrowth (SIBO). Some studies show that the gut microbes of people with IBS differ from healthy people, but it’s unclear whether this is a cause or a consequence of the disease. Genetics and early life trauma may also influence the risk of developing IBS later in life.[3]

    Can stress make IBS worse?

    What is the role of genetics in IBS?

    Examine Database: Irritable Bowel Syndrome (IBS)

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    Frequently asked questions

    What is IBS?

    IBS is a common functional disorder of the large intestine that affects an estimated 20% of the global population, with a significant negative impact on quality of life and high co-occurrence with anxiety and depression.[1] IBS is twice as common in women compared to men, which could be explained, in part, by genetics and hormonal changes during the menstrual cycle.[2]

    IBS can be classified into three different subtypes: diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), or mixed (IBS-M). If it occurs after a gastrointestinal infection, such as food poisoning, it’s considered post-infectious IBS.[3]

    What are the main signs and symptoms of IBS?

    The main signs and symptoms of IBS include long-term changes in bowel habits (lasting months), abdominal pain, bloating, mucus in the stool, and a feeling of incomplete evacuation after having a bowel movement.[3]

    How is IBS diagnosed?

    The Rome IV criteria can be used to diagnose IBS based on the proportion of bowel movements rated as constipation or diarrhea compared to those rated as normal. Symptoms need to occur at least once per week for at least three months to be considered IBS.[4] However, there is no exact test for IBS, so a doctor (often a gastroenterologist) may need to rule out other potential diseases with blood and stool tests, and they might also perform a colonoscopy.[3]

    What are some of the main medical treatments for IBS?

    Medications for diarrhea-predominant IBS include antidiarrheals that reduce intestinal motility (organized contractions of the digestive tract) and reduce water content in the bowel. Doctors may also prescribe antibiotics to treat underlying infections or small intestinal bacterial overgrowth (SIBO). Drugs for constipation include over-the-counter laxatives or prescriptions that increase water content in the bowel or enhance intestinal motility. Antidepressants or antispasmodics can be used to normalize intestinal motility.[3]

    Have any supplements been studied for IBS?

    Several supplements have been studied and supported by strong evidence for the relief of certain IBS symptoms. Enteric-coated peppermint oil can reduce abdominal pain, and certain probiotic strains are effective for multi-symptom relief.[5][6] Polymethylsiloxane polyhydrate — an over-the-counter intestinal adsorbent — may also relieve multiple IBS symptoms.[7] One study has shown that glutamine supplementation may improve the symptoms of post-infectious IBS.[8] Prebiotics (carbohydrates used preferentially by beneficial gut microbes) aren’t clearly effective, however, and the benefits of other alternatives like traditional Chinese medicinal herbs or aloe vera need to be confirmed in higher-quality studies.[9]

    How could diet affect IBS?

    Many soluble fibers can be fermented by gut microbes to produce energy, resulting in by-products such as short-chain fatty acids and gas. The combination of fermentability and solubility can lead to accumulated gas and water retention in the colon, which can worsen abdominal pain and diarrhea. The low-FODMAP diet has been shown to reduce diarrhea-predominant IBS symptoms, and traditional dietary advice (such as avoiding trigger foods, limiting alcohol, and eating smaller, more frequent meals) is similarly effective.[10]

    Should certain foods be avoided for IBS?

    IBS “trigger foods” will be different for everyone, and making a “one size fits all” list of foods to avoid is therefore difficult. However, there are some common foods that seem more likely to aggravate IBS symptoms, such as:

    Can a high-fiber diet help with IBS?

    Whether a high-fiber diet helps IBS symptoms likely depends on a few factors, including the subtype of IBS (i.e., diarrhea-predominant, constipation-predominant, or mixed), the type of fiber consumed, and the person. There are two main types of fiber: soluble and insoluble. Insoluble and soluble fiber can be further characterized by their chain length, fermentability, and viscosity.[15] Interestingly, different types of fiber can have very different effects on IBS symptoms. In general, experts recommend an increased intake of soluble fiber, but not insoluble fiber, for people with IBS.[16][17] However, there are some caveats. For example, some sources of soluble fiber, such as fructans (e.g., inulin) and galactooligosaccharides, can aggravate IBS symptoms. These fibers are highly fermentable and may increase gas production and worsen bloating and feelings of fullness.[18][19] These fiber types are found in foods like onions, garlic, asparagus, and legumes.[20][21] In a low-FODMAP diet, these fibers (among other dietary components) are reduced and then slowly reintroduced, which may reduce symptoms of IBS, particularly in people with diarrhea-predominant IBS.[22][23][24]
    Psyllium is a soluble fiber with relatively low fermentability and high viscosity (gel-forming properties).[25] Research suggests that supplementing with psyllium may reduce symptoms of IBS in all subtypes of IBS. However, psyllium fiber is difficult to come by naturally in foods and is usually taken as a dietary supplement.[26][13] Insoluble fibers are commonly found in whole grains, fruits, and vegetables. They tend to undergo little fermentation and result in a low amount of gas production.[15] Most studies on IBS have used wheat bran as a source of insoluble fiber, and results have consistently demonstrated no effect on symptoms of IBS.[26][13]
    The recommended intake for fiber is 25–38 grams per day.[15] Research suggests that people with IBS tend to eat less fiber compared to people without IBS, which could indicate an avoidance of dietary triggers.[27] Finding the right balance between consuming enough fiber and minimizing IBS symptoms can be a challenge. This often requires a personalized approach that can be aided by consulting a nutrition professional, like a dietitian or nutritionist.

    Are there any other treatments for IBS?

    Cognitive behavioral therapy provided modest IBS symptom improvement (similar to other forms of psychotherapy) in a small number of studies.[11] Hypnotherapy has also been found to help about 50% of the participants in the few studies that have been performed.[12] Psyllium husk is an over-the-counter fiber supplement that can normalize stool and reduce symptoms in IBS.[13] Acupuncture has also been studied, but it was no more effective than the sham (or placebo) treatment, so its benefits are very likely due to the placebo effect.[14]

    How does physical activity affect IBS?

    New therapies, including hypnotherapy and cognitive behavioral therapy, are being developed to help manage IBS and its symptoms.[32][33] One study found that physical activity improved IBS symptoms in general, but this study included all patients with IBS without looking at IBS-C and IBS-D separately.[34]

    What causes IBS?

    The causes of IBS are unknown, but research indicates a number of factors are involved, including abnormal gut-brain axis communication, visceral hypersensitivity and altered motility, and the gut microbiota. Miscommunication between the brain and the gut could cause abnormal intestinal motility and visceral hypersensitivity, leading to changes in bowel function and abdominal pain. One form of IBS can be brought on by a gastrointestinal infection, and many symptoms of IBS also occur with small-intestinal bacterial overgrowth (SIBO). Some studies show that the gut microbes of people with IBS differ from healthy people, but it’s unclear whether this is a cause or a consequence of the disease. Genetics and early life trauma may also influence the risk of developing IBS later in life.[3]

    Can stress make IBS worse?

    Psychological stress is a well-established risk factor for IBS, to the point that some claim IBS is a condition of “irritable bowel and irritable brain.”[28] Changes in the gut-brain axis induced by stress can aggravate IBS symptoms through multiple different pathways involving the microbiome and the nervous system. It is estimated that around 45% of individuals with IBS may also have anxiety, depression, or other psychiatric disorders.[29]

    What is the role of genetics in IBS?

    IBS has a strong genetic component, and genetic studies have suggested that the heritability of IBS (the degree to which this condition is due to genetic factors) may be between 22–57%.[30] Individuals who have a relative with IBS are 2–3 times more likely to have IBS.[30] A study found that women with IBS-D had a gene mutation that affected serotonin receptors in the gut. Since gut-derived serotonin helps regulate intestinal motility, this could explain some IBS symptoms.[31] While hundreds of genetic variants have been studied for their potential role in IBS, to date, no single gene has been identified as playing a major role in IBS, though research is ongoing.

    Update History

    Examine Database References

    1. Breath Methane - Derrick K Ong, Shaylyn B Mitchell, Jacqueline S Barrett, Sue J Shepherd, Peter M Irving, Jessica R Biesiekierski, Stuart Smith, Peter R Gibson, Jane G MuirManipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndromeJ Gastroenterol Hepatol.(2010 Aug)
    2. Fatigue Symptoms - Heidi Maria Staudacher, Miranda C E Lomer, Freda M Farquharson, Petra Louis, Francesca Fava, Elena Franciosi, Matthias Scholz, Kieran M Tuohy, James O Lindsay, Peter M Irving, Kevin WhelanA Diet Low in FODMAPs Reduces Symptoms in Patients With Irritable Bowel Syndrome and A Probiotic Restores Bifidobacterium Species: A Randomized Controlled TrialGastroenterology.(2017 Oct)
    3. Fatigue Symptoms - Shanti Eswaran, William D Chey, Kenya Jackson, Sivaram Pillai, Samuel W Chey, Theresa Han-MarkeyA Diet Low in Fermentable Oligo-, Di-, and Monosaccharides and Polyols Improves Quality of Life and Reduces Activity Impairment in Patients With Irritable Bowel Syndrome and DiarrheaClin Gastroenterol Hepatol.(2017 Dec)
    4. Irritable Bowel Syndrome Symptoms - Shanti L Eswaran, William D Chey, Theresa Han-Markey, Sarah Ball, Kenya JacksonA Randomized Controlled Trial Comparing the Low FODMAP Diet vs. Modified NICE Guidelines in US Adults with IBS-DAm J Gastroenterol.(2016 Dec)
    5. Irritable Bowel Syndrome Symptoms - Mohammad Javad Zahedi, Vahideh Behrouz, Maryam AzimiLow fermentable oligo-di-mono-saccharides and polyols diet versus general dietary advice in patients with diarrhea-predominant irritable bowel syndrome: A randomized controlled trialJ Gastroenterol Hepatol.(2018 Jun)
    6. Irritable Bowel Syndrome Symptoms - Natalia Pedersen, Nynne Nyboe Andersen, Zsuzsanna Végh, Lisbeth Jensen, Dorit Vedel Ankersen, Maria Felding, Mette Hestetun Simonsen, Johan Burisch, Pia MunkholmEhealth: low FODMAP diet vs Lactobacillus rhamnosus GG in irritable bowel syndromeWorld J Gastroenterol.(2014 Nov 21)
    7. Irritable Bowel Syndrome Symptoms - Emma P Halmos, Victoria A Power, Susan J Shepherd, Peter R Gibson, Jane G MuirA diet low in FODMAPs reduces symptoms of irritable bowel syndromeGastroenterology.(2014 Jan)
    8. Irritable Bowel Syndrome Symptoms - Lena Böhn, Stine Störsrud, Therese Liljebo, Lena Collin, Perjohan Lindfors, Hans Törnblom, Magnus SimrénDiet low in FODMAPs reduces symptoms of irritable bowel syndrome as well as traditional dietary advice: a randomized controlled trialGastroenterology.(2015 Nov)
    9. Irritable Bowel Syndrome Symptoms - Bridgette Wilson, Megan Rossi, Tokuwa Kanno, Gareth C Parkes, Simon Anderson, A James Mason, Peter M Irving, Miranda C Lomer, Kevin Whelanβ-Galactooligosaccharide in Conjunction With Low FODMAP Diet Improves Irritable Bowel Syndrome Symptoms but Reduces Fecal BifidobacteriaAm J Gastroenterol.(2020 Jun)
    10. Irritable Bowel Syndrome Symptoms - Ruth M Harvie, Alexandra W Chisholm, Jordan E Bisanz, Jeremy P Burton, Peter Herbison, Kim Schultz, Michael SchultzLong-term irritable bowel syndrome symptom control with reintroduction of selected FODMAPsWorld J Gastroenterol.(2017 Jul 7)
    11. Irritable Bowel Syndrome Symptoms - Yawen Zhang, Lijun Feng, Xin Wang, Mark Fox, Liang Luo, Lijun Du, Binrui Chen, Xiaoli Chen, Huiqin He, Shuwen Zhu, Zhefang Hu, Shujie Chen, Yanqin Long, Yubin Zhu, Li Xu, Yanyong Deng, Benjamin Misselwitz, Brian M Lang, Bahtiyar Yilmaz, John J Kim, Chung Owyang, Ning DaiLow fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet compared with traditional dietary advice for diarrhea-predominant irritable bowel syndrome: a parallel-group, randomized controlled trial with analysis of clinical and microbiological factors associated with patient outcomesAm J Clin Nutr.(2021 Jun 1)
    12. Diarrhea Symptoms - Dana M Lis, Trent Stellingwerff, Cecilia M Kitic, James W Fell, Kiran D K AhujaLow FODMAP: A Preliminary Strategy to Reduce Gastrointestinal Distress in AthletesMed Sci Sports Exerc.(2018 Jan)
    13. Irritable Bowel Syndrome Symptoms - Lech Y, Olesen KM, Hey H, Rask-Pedersen E, Vilien M, Ostergaard OTreatment of irritable bowel syndrome with peppermint oil. A double-blind study with a placeboUgeskr Laeger.(1988 Oct 3)
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    20. Irritable Bowel Syndrome Symptoms - Belcaro G, Gizzi G, Pellegrini L, Feragalli B, Cotellese R, Cacchio M, Corsi MPycnogenol® supplementation improves the control of irritable bowel syndrome symptomsPanminerva Med.(2018 Jun)
    21. Irritable Bowel Syndrome Symptoms - Chen KH, Zeng BY, Zeng BS, Sun CK, Cheng YS, Su KP, Wu YC, Chen TY, Lin PY, Liang CS, Hsu CW, Chu CS, Chen YW, Yeh PY, Wu MK, Tseng PT, Hsu CYThe efficacy of exogenous melatonin supplement in ameliorating irritable bowel syndrome severity: A meta-analysis of randomized controlled trials.J Formos Med Assoc.(2022-Oct-15)
    22. Irritable Bowel Syndrome Symptoms - Hong SW, Chun J, Park S, Lee HJ, Im JP, Kim JSIs Effective and Safe in Short-term Treatment of Irritable Bowel Syndrome: A Systematic Review and Meta-analysis.J Neurogastroenterol Motil.(2018-Oct-01)
    23. Irritable Bowel Syndrome Symptoms - Wu, Y; et al.The Efficacy of Probiotics, Prebiotics, Synbiotics, and Fecal Microbiota Transplantation in Irritable Bowel Syndrome: A Systematic Review and Network Meta-Analysisnutrients.(2024-07-02)
    24. Irritable Bowel Syndrome Symptoms - .(2024-09-04)
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    26. Constipation Signs and Symptoms - Shelton MGStandardized senna in the management of constipation in the puerperium: A clinical trialS Afr Med J.(1980 Jan 19)