Gut feeling: getting to the bottom of irritable bowel syndrome

7 minute read

Irritable bowel syndrome can manifest in a range of complex presentations, making it a challenge to treat


“My stomach bloats like I’m six months pregnant.” 

“I’m too scared to leave the house in case I have an accident.” 

“My tummy hurts all the time.” 

These are common presentations of irritable bowel syndrome (IBS), which affects about one in five Australians, with women at least twice as likely to be affected as men.

Irritable bowel syndrome is not a disease. Rather, it is a chronic and debilitating functional gastrointestinal disorder that affects 9% to 23% of the population globally.1

It is a diagnosis of exclusion, once all other pathologies have been ruled out.

IBS can start at any stage of life and can manifest in a range of complex presentations, sometimes influenced by dietary, lifestyle or psychological factors.2 Presenting complaints may include abdominal pain, bloating, and diarrhoea or constipation, or often both at once.

Generally, if a patient opens their bowels more than three times per day, the causes of diarrhoea need investigating. Meanwhile, it’s worth remembering a patient may have had lifelong symptoms, and so in fact have no idea about what constitutes a “normal” bowel pattern.

Bloating is defined as a sensation of tightness and pressure within the abdomen, which may or may not be relieved by the passing of flatus. It can result from receptive relaxation – a reflex involved in the relaxation of distal parts of the digestive system in response to food ingestion. Diabetes can also cause bloating, distension and decreased motility of the small bowel.

As readers will be aware, irritable bowel syndrome can cause patients great physical and emotional discomfort.

In particular, flatulence can be highly embarrassing to discuss both with family members or healthcare providers.

A recent change in the characteristics of flatulence and bowel habit can often prompt a patient to seek help. Flatulence can vary with the changes in diet and is related to the relative predominance of protein, carbohydrate and fibre in food. The resulting gas is a combination of hydrogen sulphide and methane, in variable proportions. Fad diets, such as a high-protein diet, (or pure protein diet consumed by elite athletes) may result in an alteration of the gut microbiota, which can lead to changes in the bowel pattern.

Depending upon the nature and severity of their symptoms, patients may require referral for endoscopic investigations in order to rule out gastrointestinal pathology.

Giving reassurance and acknowledgement to the patient at this time is useful, so that they know that their symptoms are being taken seriously and that the investigations can help guide diagnosis and treatment.

It is also worth explaining that IBS carries no risk for further illness, and that effective options are available to relieve the discomfort, and perhaps all symptoms of IBS.

When taking the history, it is pertinent to ask patients suspected of having IBS whether they chew and swallow quickly, which can sometimes be accompanied by gulping of air. Also enquire about the regularity of meals and food preparation habits, as well as fluid intake. For one patient, the replacement of carbonated water and soft drinks with tap water was sufficient to remove the symptoms.


Adjusting the intake of fibre – either increasing or decreasing – can be helpful in certain circumstances. Fibre can act as a bulking agent and can promote the absorption of water, leading to stretching and promoting gut motility and the transit of the contents.

The Australian Dietary Guidelines encourage an increase in the intake of fruits, vegetables, grains (especially whole grains) and legumes for people with IBS.3 However, while many patients will benefit from an increase in total fibre from both soluble and insoluble sources, it is possible to go overboard in following this recommendation.

Patients who regularly consume a high-fibre breakfast cereal may find their abdominal bloating is relieved by replacement of this with puffed rice.


During the investigation of the symptoms of IBS, food allergies or food intolerance (e.g. to amines, salicylates, butyrates, glutamates and other food chemicals) will need to be eliminated.6 If you feel a dietitian referral would be useful, the association’s website ( can identify practitioners with an interest in this area.


It’s worth noting that IBS symptoms may present as part of an accompanying eating disorder. Chronic constipation is not uncommon in patients with anorexia nervosa, whose intake of food and fluids is low, and who may also be highly anxious.

The sense of urgency can be closely linked to anxiety, and effective management of anxiety may help with the severity and frequency of the symptoms of IBS.

Constipation can also be present when food is purged through regular vomiting. Diarrhoea can be present in patients with an eating disorder who abuse laxatives, or those who binge eat. Binge eaters in particular can suffer from bloating and altered bowel habits due to extreme, but irregular, food intake.

Some patients who binge eat may attempt to seek a diagnosis of IBS, which allows them to remain in denial about the underlying eating disorder.5


Many people who don’t like to use public toilets will “hang on” until they reach homes. They will also endure the pain that comes from habitually delaying their flatulence until a suitable time, especially if it is accompanied by an odour.

They may have endured years of shame and avoidance of social contact. A straightforward discussion about individual differences in bowel habits can be useful here.4


The low FODMAP (fermented oligo, disaccharide, monosaccharide and polyols) diet has attracted a lot of interest in recent years.

FODMAPs are small- and large-chained carbohydrates that are poorly absorbed in the small intestine. They can reach the large intestine where their fermentation by the normal gut bacteria can produce gas and promote the retention of water. This can cause alterations in small and large bowel function in susceptible individuals.  The low-FODMAP diet seeks to decrease the amount of these undigested sugars in the large bowel.7,8

The most common of these is lactose. Many patients obtain symptomatic relief with the removal of the cows’ milk dairy foods, such as milk, soft cheese, yoghurt and ice-cream. In order to maintain the calcium intake, it is important to replace dairy with calcium-enriched soy milk, almond milk or similar, hard cheese, or tinned fish containing bones, such as salmon or sardines.

Other commonly consumed FODMAPs include fructose and sorbitol. The sources of these should clearly explained along with comprehensive instruction in the reading and interpretation of food labels.

Alcohol and caffeine consumption can also give rise to the symptoms of IBS, due to their effects on gut motility, so it’s worth considering a removal of alcohol, tea, coffee, cocoa and chocolate as part of a low-FODMAP regime.

It is important to explain to the patients with  IBS that the production of gas is a normal part of gastrointestinal function, but that excessive or foul-smelling flatulence requires further investigation.

The low-FODMAP diet should not be used for longer than six to eight weeks as it reduces the fibre content of the diet. The dietary benefits of consuming a wide range of foods, including fibre-rich foods, are significant; therefore a low-FODMAP diet should not be pursued long-term. It needs to be discussed in terms of the patient’s overall dietary intake, which is best done with a dietitian.

After the symptoms have settled from the trial of a low-FODMAP diet, a logical and sequential challenge of reintroduction of the removed foods should be attempted. The aim of this process is to reach a compromise between symptom improvement and maintaining the widest possible variety of nutritious foods in the patient’s diet.

Finally, with the current interest in the gut microflora, it will be interesting to see if the possible manipulation of gut microbiome might remove the symptoms of IBS altogether.

Genevieve Michael is an accredited practicing dietitian with more than 30 years’ experience in healthcare and has a specialist interest in diabetes, GDM, IBD and eating disorders


1. World Gastroenterology Organization Irritable bowel syndrome: a global perspective. World Gastroenterology Organization Global Guideline 2009

2. World J Gastroenterol v.20(22); 2014 Jun 14; 20 (22) 6759-73


4. Neurogastroenterol Motil 2015 Sep; 27(9): 1249-57


6. World J Gastroenterol 2015 Jun21:21(23): 7089-109

7.  J Gastroenterol Hepatol. 2010 Feb:25(2) 252-8

8. J Gastroenterol Hepatol. 2010 Aug:25 (8) 1366-73

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