Irritable Bowel Syndrome (IBS) is a gastrointestinal disorder that comprises a group of symptoms that generally occur together without noticeable organic causes. These symptoms typically consist of recurrent discomfort or abdominal pain, bloating, and changes in bowel movements, which can manifest either as constipation, diarrhea, or both.
To diagnose IBS, symptoms must be present for at least three days a month over three months. IBS, however, has a highly variable clinical presentation and can differ in terms of duration and severity between affected individuals. (1)
The article will provide a summary of IBS, its risk factors, associated conditions, and therapeutic options.
Table of Contents
What can cause IBS? What are the Risk Factors?
Although the exact pathophysiological mechanisms behind IBS are still unknown, both psychosocial and physiological factors play a role in the development and persistence of symptoms and disease evolution. Stress, anxiety, diet, lifestyle, and hormonal changes are complex factors that interplay and act as triggers, leading to immune activation and aggravation of symptoms. (2)
The diagnosis of IBS is considered by a review of an individual’s history and the Rome Criteria listed below.
The Rome IV Criteria
- Recurrent abdominal pain, on average of at least 1 day per week in the last 3 months, associated with two or more of the following:
- Related to defecation
- Associated with a change in stool frequency
- Associated with a change in stool form (appearance
- Criteria should be fulfilled for the last 3 months with symptom onset over six months prior to diagnosis
IBS patients usually find that certain foods can aggravate the symptoms. Processed foods, carbonated beverages, and other sugary foods contribute to IBS flare-ups. Additionally, caffeine can increase bowel movements and exacerbate diarrhea.
A specific group of carbohydrates, the FODMAPS, are also known to magnify the symptoms, and they breakdown into the following: Fermentable oligosaccharides (galacto-oligosaccharides and fructans), Disaccharides (lactose), Monosaccharides (fructose), and Polyols (sorbitol and mannitol).
Similarly, sugar malabsorption patterns are also commonly reported amongst people with IBS. For example, in lactose intolerance, the undigested lactose in the colon increases bacterial fermentation and, consequently, gas production. That is why avoiding certain foods and implementing dietary restrictions such as a low FODMAP intake are essential steps for managing IBS. (3)
Mental health contributes to physical wellbeing. Factors such as stress and anxiety have not only emotional repercussions but can also manifest physically. The autonomic nervous system regulates the function and mobility of the gut and our “fight or flight” response. Experiencing emotions and feelings of distress can sometimes result in overactivity of the gut, reduced intestinal blood flow, and increased intestinal permeability. (4)
The Microbiome and the Gut-brain Axis
There are 100 trillion bacteria in the adult body, and 80% exist in the gut. These bacteria have a gene pool that is 150 times greater than the human genome. Here is more information on the Microbiome from a YHF link.
Our diet impacts the growth of our gut microbiome in many ways. Studies have shown that a plant-based diet high in phytochemicals can have a prebiotic effect, supporting the growth of a healthy, diverse microbiome. When the diet is high in processed foods, there is a decreased in microbial diversity. Imbalances of the normal gut bacterial community (dysbiosis) can activate an immune response and lead to inflammation. (5)
Take gastroenteritis as an example. When there is an infection, the immune system becomes activated, with increased cytokines and immune cells production. These inflammatory mediators are crucial to help the body fight the infection. However, they can also induce low-grade inflammation with persistent changes in the mucosa responsible for the emergence or worsening of IBS symptoms. (2)
The gut microbiome produces proteins that can influence the brain. The concept of the gut affecting the brain has been referred to as the gut-brain axis. This can be related to neural pathways of the enteric, autonomic nervous system, and the vagus nerve, hormone signaling, and neurotransmitters produced by gut bacteria.
IBS has been associated with defective serotonin signaling in the gut. Associated with mood, sleeping, and digestion, serotonin is a byproduct of gut bacteria, which affects the brain similarly. The gut produces approximately 95% of total serotonin. Important to IBS, serotonin appears to play a role in immune activation and the development of inflammation.
Signs & symptoms of irritable bowel syndrome
IBS has a particularly variable clinical presentation. The symptoms can be episodic or persistent, but they are usually worse after meals and during menstruation. Some of the most common signs and symptoms include:
- Abdominal discomfort and pain (with relief after a bowel movement)
- Diarrhea (isolated or alternating with constipation)
- Excess gas and flatulence
- Mucus in feces
- Other, generalized symptoms can occasionally occur with IBS, like fatigue.
Overlapping Conditions with IBS
SIBO stands for small intestinal bacterial overgrowth. This condition relates to changes in bacterial populations in the small intestines, where there is overgrowth on of certain bacteria over the usual microbial diversity of the gut. It leads to signs of inflammation, diarrhea, and other health issues. Several diseases lead to SIBO, including renal failure, diabetes, gastric resection, and small bowel dysmotility. The process can be diagnosed by specialized functional tests of the bowel, including a positive lactulose breath tests.
Studies have found a considerable overlap of dysfunction in IBS and SIBO. One study showed that 84% of patients with criteria for IBS had abnormal lactulose breath tests. (10) The prevalence of this condition in irritable bowel syndrome is actually quite high, approximately a 38% prevalence rate in fifty studies. There is also a fivefold increase risk of SIBO in persons with irritable bowel syndrome. (11) However, there are enough inconsistencies that cast doubt that IBS is a subset of SIBO or acting primarily as an infectious disease.
Inflammatory Bowel Disease (IBD)
Although IBD and IBS can occur concomitantly, they are two distinct disorders. IBD is an umbrella term that comprises two types of chronic inflammation, Crohn’s disease and Ulcerative colitis.
IBD shares some of the same symptoms of IBS, including rectal bleeding, fatigue, and weight loss. Unlike IBS, there is evidence of persistent inflammation, tissue ulceration, and permanent damage in IBD. Consequently, IBD is also associated with a higher risk for colon cancer (from damage and cell turnover). (6)
Celiac disease is a hereditary autoimmune enteropathy caused by a permanent intolerance for the primary storage protein of wheat – gluten. The absorption of nutrients into the bloodstream occurs in the small intestine. This means that, besides the impact on the gastrointestinal tract, there will be systemic symptoms like bone and joint pain, rash, fatigue, anemia, peripheral neuropathy, arthritis, and depression. Additionally, it appears to be beneficial to adopt a gluten-free diet for both celiac and non-celiac IBS patients. (7)
Treatment Options for IBS
Diet & nutrition
IBS patients should avoid triggering foods, particularly FODMAPS. A registered dietician can assist a person in understanding better which problematic foods to eliminate because, ultimately, FODMAPS do have health benefits and, to some degree, can remain in the diet. (3)
Alcohol can also increase IBS symptoms; it reduces the absorption of nutrients, interacts with gut bacteria, speeds up motility, and can increase the absorption of FODMAPS. (8)
The diet should consist mainly of natural foods with a high intake of fiber. Contrary to popular belief, fiber can remain even in the case of diarrhea. Fiber from fruits and vegetables helps diminish bloating, lower LDL cholesterol, and protect against colon cancer. (2, 3) Hippocrates has been attributed to saying, “let food be thy medicine and medicine by they food.” In the case of irritable bowel syndrome, this holds especially true.
Exercise can have a long-term beneficial impact on managing IBS symptoms, both psychological and physical. Increased physical activity helps reduce fatigue, stress, and anxiety, enhances intestinal gas clearing and relieves abdominal bloating. (9)
A pilot study suggested that a nine-week training program on relaxation techniques could improve the symptoms, down to the level of genetic expression, in both IBS and IBD. Further studies are needed to clarify the effect of relaxation and mindfulness meditation on IBS.
The pharmacological approach to IBS used to consist of treating each gastrointestinal symptom individually. Newer medications like linaclotide and lubiprostone can be quite effective options. Their mechanism of action are specific to the GI tract: the former targets guanylate cyclase receptors; the latter affects chloride channels.
Nevertheless, each person should address their condition with dietary changes and medication options specific to their needs.
In summary, the clinical presentation of IBS is wide-ranging with overlapping symptoms and degrees of severity, so there isn’t a one-size-fits-all treatment plan. (2)
However. it is important to remember that a functional condition such as irritable bowel syndrome can be an indicator of a dietary imbalance, stress, and high-risk lifestyle factors. In many ways, the body communicates to the brain its state health or dysfunction. It is important to remain open to the message. Fortunately, most individuals with IBS can recalibrate their diet and optimize self-management to allow for a healthy, functioning bowel, free of pain and cramping.
1. Irritable Bowel Syndrome: a Global Perspective. 2015. World Gastroenterology Organisation. Global Guidelines
2. Lekha, S. Irritable bowel syndrome: Pathogenesis, diagnosis, treatment, and evidence-based medicine, World J Gastroenterol. 2014 Jun 14; 20(22): 6759–6773. doi: 10.3748/wjg.v20.i22.6759
4. Qin H, et al. Impact of physiological stress on irritable bowel syndrome, World J Gastroenterol. 2014 Oct 21; 20(39): 14126–14131, DOI: 10.3748/wjg.v20.i39.14126. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4202343/
5. Menees S. The gut microbiome and irritable bowel syndrome, Version 1. F1000Res. 2018; 7: F1000 Faculty Rev-1029., Published online 2018 Jul 9. doi: 10.12688/f1000research.14592.1.
6. Quigley E. Overlapping irritable bowel syndrome and inflammatory bowel disease: less to this than meets the eye?, Therap Adv Gastroenterol. 2016 Mar; 9(2): 199–212. DOI: 10.1177/1756283X15621230
7. Markharia, A et al. The Overlap between Irritable Bowel Syndrome and Non-Celiac Gluten Sensitivity: A Clinical Dilemma, Nutrients. 2015 Dec; 7(12): 10417–10426. DOI: 10.3390/nu7125541
8. Reding K, et al. Relationship between Patterns of Alcohol Consumption and Gastrointestinal Symptoms among Patients with Irritable Bowel Syndrome, Am J Gastroenterol. Author manuscript; available in PMC 2013 Aug 1.
9. Johannesson E et al. Intervention to increase physical activity in irritable bowel syndrome shows long-term positive effects, World J Gastroenterol. 2015 Jan 14; 21(2): 600–608. doi: 10.3748/wjg.v21.i2.600
10. Dukowicz A, et al. Small Intestinal Bacterial Overgrowth. 2007. Gastroenterol Hepatol (NY) 3(2):112-122.
11. Chen B, Kim J, Zhang Y, Du L, Dia N. Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis. J Gastroenterol. 2018. 53(7):807-818. doi: 10.1007/s00535-018-1476-9.
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