IBS can be uncomfortable but is usually harmless. Symptoms include bouts of abdominal (tummy) discomfort and pain, bloating and changeable bowel habits from diarrhoea (runny poo) to constipation (hard poo).
IBS affects 1 in 7 people and is more common in women than men, and in those aged under 50.
Changing to a low-FODMAP diet improves symptoms in 3 out of 4 people. Keeping active and managing stress can also help.
If dietary and lifestyle changes don't help, there are medications to help relieve specific symptoms.
What causes IBS?
The exact cause of IBS is still not certain. However, there is emerging evidence that changes in your gut bacteria and inflammation of your immune system may play a role in its development.
In particular, factors that contribute to IBS are thought to be:
sensitivity – you may have a more sensitive gut (sometimes called ‘visceral sensitivity’)
digestion speed – the contents of your gut may move unusually quickly or slowly (sometimes called ‘altered gut motility’)
bacteria – you may have an imbalance of ‘good’ and ‘bad’ bacteria in your gut (sometimes called ‘dysbiosis’)
leaky gut – your gut may be slightly inflamed or ‘leaky’, ie, it may have small cracks or openings that allow partially digested food, toxins and bugs to get through the gut barrier
infection – you may have had an infection, such as gastroenteritis, that trigged the IBS.
What are the symptoms of IBS?
The most common symptoms of IBS are abdominal pain or discomfort, often reported as cramping, along with changes in bowel habits.
Usually, the pain or discomfort will be associated with at least 2 of the following 3 symptoms:
Feeling better after having a bowel movement
Having bowel movements more or less often than usual
Having diarrhoea or constipation as defined below:
diarrhoea – having loose, watery stools 3 or more times a day and feeling urgency to have a bowel movement
constipation – having fewer than 3 bowel movements a week. Stools can be hard, dry and small, making them difficult to pass. Some people find it painful and often have to strain to have a bowel movement.
For a diagnosis of IBS, these symptoms must occur at least 3 times a month.
Other symptoms of IBS may include:
feeling that a bowel movement is not completely finished
passing mucus – a clear liquid made by your gut that coats and protects its tissues
What triggers symptoms of IBS?
Most people with IBS notice that food triggers symptoms. In particular, a group of short-chain carbohydrates called FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols).
FODMAPs are either poorly absorbed in your small intestine or are not digestible.
Because they are poorly absorbed, they reach the end of your digestive system (the large intestine or colon), where most of your gut bacteria live. Here, your gut bacteria ferment them, producing gas. This leads to bloating and flatulence.
FODMAPS also have an osmotic effect and draw water into your colon. This can cause cramping and more bloating.
Depending on your digestive system, the combination of producing gas and drawing water in can lead to inconsistent or excessive bowel movements, diarrhoea or constipation and tummy pain.
This process is likely to be made worse by stress and lack of physical activity.
When should I seek medical advice?
If you have the symptoms above, see your doctor for a check-up. See your doctor immediately if have any of the following symptoms:
Your doctor will usually make a diagnosis based on your symptoms. Because the symptoms of IBS are similar to those of more serious conditions, you may have one or more of the following tests: sigmoidoscopy, faecal (poo) testing or a colonoscopy.
There is also breath testing available to see if you have intolerances to fructose or lactose or are a methane producer. Breath testing can also see whether you may have small bowel bacterial overgrowth. This approach involves you eating the substrates individually and then breathing into a machine to assess your response and symptoms to this. This is usually done a few days apart and will enable a suitably qualified dietitian to give you advice on what to avoid to improve your symptoms.
What are the treatments for IBS?
There is no cure for IBS, but there are treatments that can make a big difference. Talk to your doctor about what might be best for you. Treatment options include:
following a low-FODMAP diet
increasing physical activity
having cognitive behavioural therapy.
Research suggests that 3 in 4 people with IBS get symptom relief, usually within 1–4 weeks, from following a low-FODMAP diet, and that these positive effects can continue long term. It’s best if you can see a dietitian experienced in this diet to help support you make the changes needed. Read more about the low-FODMAP diet and common foods containing FODMAPs. There is also an app developed by Monsash University to help you follow this diet.
There is also evidence that being more active can help reduce your IBS symptoms. This may be because it helps digested food move through your gut, reducing gas and bloating. Read more about the benefits of physical activity.
Medications are sometimes recommended to help treat IBS symptoms. Some examples include:
laxatives for relief of constipation
anti-diarrheal medications to relieve chronic diarrhoea
anti-spasmodic medications to assist in relieving abdominal pain and cramps
Dr Derek Luo is a consultant gastroenterologist at Counties Manukau Health and has also been in private practice since 2011. He has a broad interest in general gastroenterology and hepatology and has a sub-specialty interest in pancreatic and hepatobiliary disease.
Credits: Health Navigator Editorial Team . Reviewed By: Dr Derek Luo, consultant gastroenterologist
Last reviewed: 04 Jun 2019
Managing IBS with a low-FODMAP diet
Many dietitians and doctors now recommend a low-FODMAP diet as a key part of a treatment plan for people with IBS.
Most people with IBS who have tried the diet have experienced a great improvement in their symptoms and a reduced need for medication.
What are FODMAPs?
Some foods can cause your bowel to stretch and expand. This usually happens because they contain elements that:
are 'osmotic' and draw in fluid
produce gas when they are fermented by bacteria in your bowel.
FODMAPs are the most common food element this happens with. They are fermentable, poorly absorbed, short-chain carbohydrates or 'sugars'. They can't be digested by your body but are easily fermented by bacteria once they reach your bowel.
FODMAPs stands for:
Fermentable – rapidly broken down (fermented) by bacteria in your the bowel
Oligosaccharides – fructans and galacto-oligosaccharides (GOS)
Disaccharides – lactose
Monosaccharides – fructose
Polyols – sorbitol, mannitol, xylitol and maltitol.
If this seems too complex – just remember that 'saccharide' is a different word for sugar. Polyols are sugar alcohols — meaning sugar molecules that have an alcohol side-chain attached. You might already know some of these sugars or have seen them in ingredients lists on food packaging.
There are medicines that can help with some symptoms of IBS such as pain, constipation or diarrhoea. Medicines can help to control the severity of the symptoms but do not reverse or “cure” them.
Each person with IBS will have different symptoms and medicines are aimed at easing your most troublesome symptom or combination of symptoms.
Ask your doctor or nurse for dietary advice; many people with IBS find that certain foods such as FODMAPS can trigger symptoms and following a low-FODMAP diet can be beneficial.
Abdominal pain and bloating medicines
Medicines that relax the stomach (tummy) muscles can be used to used to relieve tummy cramps or spasm-type pain that can occur with IBS. They can also help to ease bloating. These medicines are called anti-spasmodics.
Examples of anti-spasmodics include hyoscine tablets (Buscopan® or Buscopan Forte®) and mebeverine (Colofac®).
Your doctor may recommend a 1 week trial of taking these regularly. If they work, then you may be advised to use them as required, when the symptoms arise. Read more about hyoscine tablets and mebeverine.
There is some evidence that peppermint oil may be useful for bloating, wind and bowel cramps. However, in some people, peppermint oil can cause or worsen reflux (indigestion).
In New Zealand, peppermint oil is available as capsules (Mintec® and Colpermin®).
Your doctor may recommend a trial of 1 capsule 3 times daily 30–60 minutes before meals for 2 weeks. If it's helpful, you can continue taking these, but reduce to the lowest effective dose. Ask your pharmacist for advice on how to take peppermint oil capsules.
If your main symptom is constipation, laxatives may help. There are a variety of different laxatives which work in different ways. Some laxatives can cause bloating, flatulence and discomfort, which can make your IBS worse. Your doctor or pharmacist can advise you on the best laxative for you. You may need to try a few laxatives before you find the right one for you. Read more about laxatives.
If diarrhoea (runny poos) is your main problem, medicines such as loperamide may be helpful to increase stool firmness, decrease stool frequency and reduce urgency. This can be used in combination with an anti-spasmodic such as mebeverine.
Loperamide works by slowing the movement of the gut, and in this way reduces the number of bowel motions and firms up runny poos.
Your doctor will start you on a low dose and depending on your symptoms, may increase your dose gradually. Do not take more than 8 tablets in 24 hours.
An approach that has been suggested for people who are fearful of the sudden and urgent need to defaecate (poo) that can occur with IBS, is for them to take 2–4 mg of loperamide approximately 45 minutes before leaving their house, particularly if access to a toilet is limited, such as when shopping or exercising.
Note that additional doses need to be carefully managed to avoid constipation later in the day. Discuss the best options with your doctor or pharmacist.
Another medicine that may be used for diarrhoea associated with IBS is mebeverine. Read more about loperamide and mebeverine.
Some people may be started on a trial of antidepressants such as amitriptyline or nortriptyline. These are used to relieve pain and slow movement of the gut, rather than treatment of psychological symptoms.
You will be started on a low dose and if needed, your dose will be increased only after 3 to 4 weeks. Amitriptyline or nortriptyline may not be suitable if you also have constipation. Read more about amitriptyline and nortriptyline.
The evidence to support the use of probiotics in irritable bowel syndrome is inconclusive (not clearly for or against their use). A 4-week trial of probiotics in the form of yoghurts or other fermented milk products can be considered. However, some of these products also contain ingredients that may worsen IBS symptoms, such as fructans, fructose or lactose. Read more about probiotics.
Information for healthcare providers on irritable bowel syndrome
The content on this page will be of most use to clinicians, such as nurses, doctors, pharmacists, specialists and other healthcare providers.
Clinical pathways and guidelines
From Auckland Regional HealthPathways: Irritable Bowel Syndrome Flow Chart
Treatment of IBS includes dietary modification, reassurance about its benign nature and lifestyle advice, such as increasing exercise and reducing stress. Most patients do not need medication. (Auckland Regional HealthPathways).
Check for symptoms, signs and other features that may suggest significant underlying pathology, and ensure that conditions such as diverticulitis, coeliac disease, inflammatory bowel disease, endometriosis, ovarian cancer, and colorectal cancer are ruled out.
Consider non‑dietary therapies for patients with a history of disordered eating patterns, as low FODMAP dietary treatment is not recommended for these patients.
Ask about potential symptom triggers, eg, caffeine, medication, stress and alcohol.
Note that a low FODMAP diet should only be undertaken be under the supervision of a dietitian.
Earlier advice has been to advice reducing foods that may aggravate specific symptoms, such as bloating, constipation, wind or diarrhoea. Irritable Bowel Syndrome and Diet Auckland DHB, 2014