Diet and IBS
The effect of diet on irritable bowel varies from person to person. While dietary factors do not cause IBS, they may worsen symptoms in some persons. Increased intestinal muscle reactivity and/ or heightened sensitivity in IBS can cause the bowel to over-respond to stimuli. Even the normal digestive process, and not a particular food, may aggravate symptoms at times.
When Eating Triggers Symptoms
Certain foods are known to stimulate gut reactions in general, and in those with IBS eating too much of these might worsen symptoms.
For example, meals that are too large or high in fat, coffee, caffeine, or alcohol may provoke symptoms of abdominal cramps and diarrhea.
Eating too much of some types of sugar that are poorly absorbed by the bowel (e.g., sorbitol, commonly used as a sweetener in many dietetic foods, candies, and gums; and fructose, also used as a sweetener and found naturally in honey as well as some fruits) can also cause cramping or diarrhea.
Eating too much of foods that are gas producing (e.g., beans, raisins, bagels) may cause increased gaseousness, particularly since IBS can be associated with retention of gas and bloating.
Often, IBS patients report that some foods can be bothersome at certain times but not at other times. There is a sense of inconsistency and unpredictability. Maintaining a food and symptom diary for a minimum of one week can help identify triggering foods. [IFFGD has available a Personal Daily Diary to help sort this out.]
In some persons, intolerance to a food product may be related to their symptoms. A sizeable proportion of people are unable to digest significant amounts of milk or milk products (lactose intolerance). It is thought that the enzyme lactase, which breaks down the milk sugar, is missing or reduced in their digestive tracts. These people may experience symptoms similar to IBS when they eat or drink milk products. Once this has been identified, the treatment is to avoid or reduce consumption of milk products in the diet. Nonetheless, people who are lactase deficient can usually tolerate a small portion at any one time of a milk product. The use of artificial sources of the enzyme lactase may control the symptoms for some.
People may also experience worsening of their symptoms due to fructose intolerance. This occurs specifically with foods that contain fructose in excess of glucose. A recent study found that poorly absorbable, highly gas-forming carbohydrates are associated with increased IBS symptoms. These foods are collectively called FODMAPS (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols). This group of foods includes fruits with fructose in excess of glucose (e.g., apples and pears), fructan-containing foods (e.g., onions, asparagus, artichokes, large amounts of wheat), raffinose-containing foods (e.g., lentils, cabbage) and sorbitol-containing foods (e.g., plums, artificial sweeteners). A FODMAPS diet in which these foods are avoided or reduced may provide some symptom relief in IBS.
For those with IBS who benefit from simple dietary modifications, it makes sense to adjust the diet. It does not make sense to adopt unnecessarily limited diets. Physicians and patients need to talk about diet. If dietary factors seem to influence symptoms, guidance needs to be provided by a knowledgeable health care professional (e.g., physician or registered dietician) who can assess individual circumstances while helping make sure that nutritional needs are being met through a balanced diet, and healthy eating habits. Read more about IBS and Diet