The low FODMAP diet is one of the best-studied dietary treatments for IBS. It helps many people, although it does not work for everyone and is best followed with dietetic support

Patients may find the video useful for a first line approach to their IBS symptoms.

NICE. Irritable bowel syndrome in adults: diagnosis and management (CG61). 2008, updated 2017.

Vasant DH, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut2021;70:1214.

McKenzie YA, Bowyer RK, Leach H, et al. British Dietetic Association systematic review and evidence-based practice guidelines for the dietary management of irritable bowel syndrome in adults (2016 update). J Hum Nutr Diet 2016.

Diverticular Disease is often diagnosed following investigations for gut symptoms. Diverticular Disease sounds like a dramatic diagnosis but in fact most people will develop some diverticula as they age, with the majority having absolutely no symptoms throughout their lifetime.

Having these pockets is called diverticulosis, and it usually causes no symptoms. When the pockets cause symptoms such as lower abdominal pain, this is called diverticular disease; when they become inflamed or infected, it is called diverticulitis. Around 80 to 85% of people with diverticulosis never develop symptoms. About 10 to 15% develop symptomatic diverticular disease, including diverticulitis.

The dietary advice has changed and patients with Diverticular Disease no longer need to avoid nuts, seeds, pips or fruit skins, and in fact, evidence now shows that patients are less likely to develop diverticular disease or suffer with diverticulitis if they keep plenty of fibre in their diet.

Often the gut symptoms that first led to the diagnosis of Diverticular Disease are in fact caused by IBS and many patients will benefit from an IBS dietary approach.

NICE. Diverticular disease: diagnosis and management (NG147). 2019

Wheat can cause a number of conditions and each condition requires an entirely different dietary intervention so it is important to get the correct diagnosis

Coeliac Disease is an autoimmune condition affecting around 1 in 100 people in the UK. The protein ‘gluten’ found in wheat, barley and rye will cause the immune system to attack the lining of the small intestine resulting in damage to the gut wall. Symptoms such as abdominal pain, urgent diarrhoea, wind and bloating are common, although patients may also suffer with non-gut symptoms such as joint pain, hair loss, infertility, extreme fatigue, headaches etc. A simple blood test at your GP surgery can diagnose this condition. In order to avoid longterm health complications treatment is a lifelong very strict gluten free diet.

Gluten Sensitivity is a relatively newly acknowledged condition which is still undergoing considerable research. Patients can suffer with symptoms similar to coeliac disease, but investigations do not show any damage to the lining of the gut. There are no tests for this condition and it is still not clear if the condition is caused by gluten or a different protein within wheat, barley or rye. It is also unclear if the diet needs to be lifelong or temporary, or how strict the diet needs to be. Dietary intervention is likely to differ between patients depending on their level of sensitivity.

Wheat Allergy is relatively uncommon in adults and can cause, or contribute to, a number of allergic conditions such as Exercise Induced Anaphylaxis; Bakers Asthma; and can be one of the food triggers in eosinophilic oesophagitis. In adults, allergic reactions to wheat can also depend on ‘co-factors’ with symptoms more likely or more severe if wheat is consumed along with co-factors such as exercise, alcohol or non-steroidal anti-inflammatories.

Often people suffer with gut symptoms when they eat wheat and assume that they are suffering with ‘wheat allergy’ when in fact they are suffering with the IBS fermentation symptoms caused by wheat. Hence, it is vital to get the correct diagnosis as a wheat allergy diet requires extremely strict avoidance while the more common IBS-type reaction to wheat only requires a reduction in wheat intake.

NICE. Coeliac disease: recognition, assessment and management (NG20). 2015.

Bile salts (also known as ‘bile acids’) are produced in the liver and released by the gallbladder to help with digestion and absorption of foods. Over 95% of bile salts are reabsorbed in the last part of the small intestine and returned to the liver to be used again.

However, if bile salts are not re-absorbed properly in your small intestine then they are likely to build up in your colon upsetting the chemical balance in your gut. These excess bile salts will cause the colon to release water into your stools resulting in watery diarrhoea. This condition is known as ‘Bile Salt Malabsorption’.

This condition can occur in some patients following the removal of their gall bladder. Patients require a SeHCAT scan to diagnose the condition and can be prescribed medication to reduce the symptoms. The effects of diet on this condition are still under investigation.

Arasaradnam RP, et al. Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition. Gut 2018;67:1380.

Food allergy affecting the gut is relatively rare in adults. However, it does occur, and the most common ‘red flags’ that I look out for in my patients are extreme symptoms such as multiple daily explosive stools (up to 10-15 per day) with regular accidents.

Importantly, food allergy that predominantly affects the gut and does not cause breathing or skin reactions, is likely to be caused by a non-IgE allergy and there are currently no validated tests for this type of allergy, so diagnosis relies on carefully supervised removal and reintroduction of foods.

However, before a food allergy diagnosis can be made, it is vital that these patients undergo investigations with a gastroenterology team to rule out other conditions such as inflammatory bowel disease.

Other adult food allergies:

Pollen Food Syndrome is the most common form of adult food allergy. Patients with this condition are likely to suffer with reactions to many foods particularly fruits and vegetables. Although symptoms can be alarming, they generally only affect the mouth and throat and pass without the need for medication. Patients with this condition will generally find that reactions only occur to the raw forms of the food e.g. raw carrots, and that they can eat all the relevant foods if the foods are well-cooked.

Eosinophilic Oesophagitis (EO) is a condition affecting the oesophagus (gullet) where certain foods can cause the lining of the oesophagus to over-produce immune cells known as ‘eosinophils’. The build up of these eosinophils can cause damage to the lining of the gullet resulting in problems with swallowing food. In some cases patients can experience distressing ‘food impaction’ where food can become stuck in the gullet. Treatment for EO generally revolves around medication and the elimination of culprit foods. Dietetic support is essential to avoid nutritional deficiencies.

Dhar A, et al. British Society of Gastroenterology and British Society of Paediatric Gastroenterology, Hepatology and Nutrition joint consensus guidelines on the diagnosis and management of eosinophilic oesophagitis in children and adults. Gut 2022;71:1459.

Skypala IJ, et al. BSACI guideline for the diagnosis and management of pollen food syndrome in the UK. Clin Exp Allergy 2022;52(9).

Histamine is one of a group of chemicals known as vasoactive amines which occur naturally in foods. Sensitivity to vasoactive amines is classified as a ‘pharmacological food hypersensitivity’ rather than a food allergy. Symptoms may be mistaken for a food allergy because symptoms can appear quite similar.

Symptoms can include flushing, itching, swelling, urticaria (hives/nettle rash), runny or blocked nose, asthma, irregular heartbeat, hypotension (drop in blood pressure), headache, abdominal pain, nausea, diarrhoea, and bloating. However, many of the gut symptoms are the same as those experienced in other gut conditions e.g. IBS , so it is vital to get a correct diagnosis before embarking on a highly restrictive low histamine diet.

NOTE: Histamine consumed in high levels can affect anyone e.g. oily fish that is degrading can contain very high levels of histamine and when eaten can cause a condition known as ‘scombroid poisoning’. Oily ‘brown’ fish such as tuna and mackerel are often the culprit as they already contain naturally high levels of histamine, although any fish that is not fresh can be involved. However this is a form of fish poisoning and is not a fish allergy, therefore there is no need to avoid fish in the longterm - simply make sure that fish is fresh when eaten.

The Low FODMAP Diet has been shown to reduce symptoms in people with inflammatory bowel disease (IBD) who have overlapping IBS. However, the Low FODMAP diet will not cure or change the underlying diagnosis of IBD and will not alter inflammation within the gut. If your IBD is in remission but you are still experiencing gut symptoms then the Low FODMAP Diet or an adapted version this diet may be useful. Remember, however, that the priority in IBD is to maintain weight and avoid weight loss or malnutrition, and hence dietetic advice and support is essential before embarking on any dietary changes.

Cox SR, et al. Effects of low FODMAP diet on symptoms, fecal microbiome, and markers of inflammation in patients with quiescent inflammatory bowel disease in a randomized trial. Gastroenterology 2020.

A group of inherited disorders that affects the skin and the joints. Often patients are hypermobile and may be able to move their bodies into unusual positions that are not possible for the general population. Many of these patients also suffer with gut symptoms and allergic conditions although research has not yet explained why. Patients commonly report that they have found some relief from gut symptoms with the use of the low FODMAP diet, particularly bloating, abdominal pain and diarrhoea. And some research suggests that the Low FODMAP diet may reduce histamine levels within the body although it remains unclear if this reduction in histamine has a direct effect on gut symptoms.