Irritable bowel syndrome (IBS) is a gastrointestinal (GI) disorder that is characterized by symptoms of abdominal discomfort and altered bowel habits that have been ongoing for at least three months. It’s classified as a functional disorder, meaning that there is a disturbance in the way the GI system is functioning but no structural abnormalities that can be seen through x-rays or other diagnostic tests. Approximately 3-15% of the population in Western countries is affected by IBS.
IBS is associated with bloating, constipation, diarrhea, abdominal pain, excessive gas production, headaches, fatigue, anxiety, and depression. It can be divided into four categories based on these symptoms: IBS-D (diarrhea predominant), IBS-C (constipation predominant), IBS-M (mixed), and IBS-U (unspecified). There is no single diagnostic test to confirm IBS. Rather, it is identified by examining the type, frequency, and severity of symptoms and ruling out other conditions with similar presentations (such as Chron’s disease or Celiac disease).
The exact etiology of IBS is unknown. Smoking and a family history of the disorder both increase risk. Although stress does not cause IBS, it may intensify symptoms. Many new cases are identified after a prolonged illness or bacterial infection, which can cause low-grade inflammation and alter the microbiome. IBS may also involve a disturbance of the gut-brain axis through disruption of the normal activity of the neurotransmitter serotonin, over 80% of which is produced in the GI tract. Altered serotonin activity can affect GI motility and sensation. It also causes mood imbalances, which is part of the reason IBS is sometimes associated with anxiety and depression.
IBS is a chronic condition, but simple dietary modifications can modify the frequency and severity of flare-ups. Common triggers for IBS include:
- High-fat foods (such as butter, oils, and fatty meats)
- Gas-producing vegetables (examples include beets, broccoli, brussels sprouts, cabbage, cauliflower, and legumes)
- Raw fruits (with the exclusion of peeled apples, ripe bananas, and melons)
- Alcohol
- Caffeine
- Sugar alcohols (found in certain beverages, as well as some sugar-free gums and candies)
Better-tolerated foods may be:
- Cooked whole grains (try oatmeal for breakfast in the morning or brown rice at dinner)
- Lean protein (focus on fish and chicken rather than high-fat meats such as marbled steak and bacon)
- Low-fat dairy (yogurt is especially beneficial, as it contains live active cultures that bolster the microbiome)
- Any fruits or vegetables that your body tolerates (eat them cooked rather than raw to ease digestion)
If you have IBS-C, eat a fiber-rich diet (high in fruits, vegetables, and whole grains) to promote bowel regularity. As fiber initially increases the amount of gas in your system, increase your intake slowly to give your body time to adapt. For those with IBS-D, too much fiber will worsen symptoms; focus on refined white flour products (yes, in some cases these can be good for you!), cooked produce, and soft protein (i.e. smooth nut butters and well-cooked meats).
Food timing, eating habits, and stress also play a role. Staying well hydrated is important. Eating five or six small meals throughout the day rather than two or three big ones may be easier on your GI system. Slowing down while you eat also helps, as eating quickly can cause you to swallow air and lead to gas and bloating. I’m a big proponent of slow, mindful eating for many different reasons; it can help you to enjoy your food more, and to feel full with less.
Another nutritional approach to treating IBS is the low FODMAP diet. The acronym FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These compounds are poorly absorbed and may therefore increase symptoms of GI disorders such as IBS. As the low -FODMAP diet is restrictive and must be performed in a regimented manner, it should only be done under the direct supervision of a registered dietitian.
IBS is very common, and one of the conditions that I get the most questions about. If you have additional questions or would like further guidance, please feel free to contact me directly and I will get back to you as soon as I can!
References
Escott-Stump, Sylvia. Nutrition and Diagnosis-Related Care. 8th ed., Wolters Kluwer, 2015.
“Irritable Bowel Syndrome (IBS) Nutrition Therapy.” Academy of Nutrition and Dietetics. Accessed 24 August 2018.