It is well known that dietary FODMAPs can trigger gut symptoms in people with IBS. However, as FODMAPs have their effects mostly in the small and large intestine, it usually takes at least 4 hours after eating a high FODMAP meal for FODMAP-related symptoms to occur (see blog on timing of symptoms here).
Despite this, many people with IBS report that their gut symptoms seem to appear or worsen immediately or soon after eating a meal. While these symptoms are clearly not related to FODMAPs in the meal just eaten, there are other gut abnormalities found in people with IBS that may help to explain this.
The gastro-colic reflex is a reflex that is triggered by eating and literally helps your gut ‘make room’ for the food you have just eaten. This reflex stimulates your gut (mostly your large intestine) to contract strongly and move its contents along. In fact, the gastro-colic reflex is why many people feel the urge to have a bowel movement shortly after eating a meal.
Studies have found that people with IBS seem to have an exaggerated gastro-colic reflex, meaning that their intestines may contract more intensely in response to eating a meal, contributing to IBS symptoms.(1) The reflex can also be intensified if you eat a very large or particularly fatty meal or even if you drink a large cold drink very rapidly.
‘Motility’ refers to the movement of your gut. Studies have shown that a large proportion of people with IBS have abnormal motility in one or more sections of their gut including the stomach, small intestine and/or large intestine.(1-3) This can mean that the gut either contracts and moves things along too quickly (fast transit time, leading to diarrhoea) or too slowly (slow transit time, contributing to constipation).
Especially strong and frequent contractions in the large intestine are also thought to be one of the main factors contributing to abdominal pain in people with IBS.(1)
How do I know if I have abnormal gut motility?
A simple way to check your own gut transit time is to eat 1-2 Tbsp of corn kernels and measure the time that it takes for the kernels to first start appearing in your stools. Normal gut transit time is considered anywhere between 10-73 hours.(3) If your gut transit is especially fast (with diarrhoea) or slow (with constipation), speak to your doctor or dietitian about possible treatments that may assist to improve your symptoms.
If you frequently experience upper gastrointestinal symptoms like heart burn, reflux, or a persistent, uncomfortable sensation of fullness after eating small amounts of food, this may point to a problem with motility in the stomach.(3) Speak to your doctor about tests that can be done to diagnose this problem.
One of the defining features of IBS is an overly sensitive gut (called visceral hypersensitivity).(1, 2, 4) In fact, one of the main reasons that FODMAPs contribute to IBS symptoms stems back to visceral hypersensitivity.
When FODMAPs are fermented in the large intestine to produce gas, this gas causes the intestines to stretch and expand (much like blowing up a balloon with air). People with IBS have nerves around their intestines that are very sensitive, meaning that this stretching causes pain signals to be sent to the brain. The brain can then also send signals back to the intestine that affect the way they move and function (i.e. can contribute to abnormal gut motility).(2)
How can I reduce the sensitivity of my gut to improve my IBS symptoms?
A low FODMAP diet is effective at reducing IBS symptoms, primarily because it reduces intestinal water retention and gas production in the large intestine.(5) Despite this, reducing FODMAPs in the diet is NOT thought to improve the underlying issue of visceral hypersensitivity, so is only part of the solution.
Psychological factors including stress and anxiety can make the gut even more sensitive, which is one of the reasons why psychological therapies are thought to help improve symptoms in many people with IBS.(6) Gut-directed hypnotherapy is another treatment approach that is believed to work by targeting and reducing gut sensitivity.(6)
Simple strategies like mindfulness meditation, breathing exercises and even yoga have also shown some promise in treating IBS, likely because they reduce stress and anxiety and so in turn reduce gut sensitivity.(6)
1. Mantides A. Gut motility and visceral perception in IBS patients. Annals of Gastroenterology. 2002.
2. Chey WD, Kurlander J, Eswaran S. Irritable bowel syndrome: A clinical review. JAMA. 2015;313(9):949-58.
3. DuPont AW, Jiang ZD, Harold SA, Snyder N, Galler GW, Garcia-Torres F, et al. Motility Abnormalities in Irritable Bowel Syndrome. Digestion. 2014;89(2):119-23.
4. Simren M, Tornblom H, Palsson OS, van Tilburg MAL, Van Oudenhove L, Tack J, et al. Visceral hypersensitivity is associated with GI symptom severity in functional GI disorders: consistent findings from five different patient cohorts. Gut. 2018;67(2):255-62.
5. Staudacher HM, Irving PM, Lomer MC, Whelan K. Mechanisms and efficacy of dietary FODMAP restriction in IBS. Nature reviews Gastroenterology & hepatology. 2014;11(4):256-66.
6. Ballou S, Keefer L. Psychological Interventions for Irritable Bowel Syndrome and Inflammatory Bowel Diseases. Clinical and Translational Gastroenterology. 2017;8(1):e214.