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Food and IBS

Many symptoms of IBS may be precipitated or made worse by eating, and this brings many people to believe that food plays a crucial role. Foods that have been associated with IBS symptoms include fatty and spicy foods, alcohol, caffeine, fermentable carbohydrates and particular food chemicals.

People with IBS frequently report their symptoms are worsened by certain foods, often concluding that they are suffering from a food allergy. Food allergies are not common in the IBS population and in most cases people will have a food intolerance.

What is a food allergy versus a food intolerance?

Food allergies: Food allergies are a result of an immune system reaction. Within cells of the skin, gut, lungs and nose we have antibodies which aim to target allergens within the environment that we may come in contact with. In people with a food allergy they will have an antibody which recognises a food protein as an allergen (e.g. peanuts) and when the person comes into contact with this food, it will trigger a cascade of events and activate the immune system to get rid of the allergen. Symptoms of this type of food allergy often occur within 30 minutes of eating a food. In the most server cases this can result in anaphylaxis (people can stop breathing). Food allergies are most common in children and most people grow out of them by adolescence. Food allergies can be diagnosed with special skin prick or patch tests, often after referral to an immunologist.

If you suspected you have a food allergy you should talk to your dietitian, or gastroenterologist and consider getting a referral to an immunologist.

Food intolerances: Food intolerances do not involve the immune system. They are much more varied, and often more difficult to diagnose. Reactions can often be delayed and may require eating larger amounts of foods. Why certain foods produce symptoms of IBS in some people remains relatively unknown. Some food intolerances are a result of malabsorption, due to a lack of enzymes in the digestive system to break down the food. For example some people do not adequately digest carbohydrates in foods, such as lactose and fructose and when they are eaten they will get symptoms of diarrhoea, abdominal pain and bloating (see Food Intolerances associated with IBS section). Other food intolerances are poorly understood and may arise from the body’s response to certain food chemicals or additives.

Food intolerances are best managed by dietitians in consultation with a gastroenterologist.


If you are interested in other gastrointestinal-focused information and intervention websites developed and hosted at
Swinburne University of Technology,
please go to:

IBDclinic.org.au for individuals with Inflammatory Bowel Disease

Gastroparesisclinic.org for individuals with Gastroparesis


This website and its content is not intended or recommended as a substitute for medical advice, diagnosis or treatment. Always seek advice of your own physician or other qualified health care professional regarding any medical questions or conditions.

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