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What is Irritable Bowel Syndrome?

Last updated on 3rd May 2023

Research suggests that at least one in ten people in the UK suffer from irritable bowel syndrome (IBS) and the majority of them are women. It is also thought that there are many more people with the condition who fail to seek medical attention and are missing out on the appropriate treatment.

IBS is the most researched of more than 20 known functional gastrointestinal disorders (FGIDs), although there is still a significant gap in scientific knowledge about the condition.

What is irritable bowel syndrome?

Irritable bowel syndrome (IBS) is a condition of the digestive system that causes uncomfortable and irritating symptoms such as painful cramps and stomach upset.

It is a common condition that currently has no cure, although there are ways to control it.

People usually suffer from IBS for their whole life, but this does not mean that the symptoms are always there. People can go a long time without having any problems from their IBS then the symptoms will suddenly show again, often after experiencing a ‘trigger’.

Man suffering with irritable bowel syndrome

What are functional GI disorders?

Functional gastrointestinal (GI) disorders is the name given to a group of disorders that primarily cause issues with the GI tract and disrupt its normal function. This causes gastrointestinal symptoms such as pain, bloating, diarrhoea and constipation.

Stress and emotional difficulty can make symptoms worse.

Functional GI disorders have three primary features:

1. The way the muscles in the GI tract work is abnormal, including spasms or contractions.

2. The nerves within the GI tract react in an abnormal way when stimulated. This often means they are oversensitive so even attempting to digest food can result in contractions that are painful and uncomfortable.

3. There is something wrong with the way that the brain and gut work together and communicate. This is known as brain gut dysfunction.

IBS is the most thoroughly researched of all known GI disorders.

What are the different types of irritable bowel syndrome?


This is a common form of IBS and is associated with sufferers experiencing constipation. This may be accompanied by other symptoms including pain, gas and bloating.


This form of IBS is associated with diarrhoea and frequent (sometimes urgent) bowel movements. Sufferers of IBS-D may also feel pain and have excessive gas.


IBS-M is where you get a mixture of the above two types of IBS. IBS-A is known as ‘alternating’ IBS where symptoms go from one extreme to the other: the sufferer may be constipated and then suffer from diarrhoea.

Post-infectious IBS (PI-IBS)

Symptoms of this form of IBS show after a gastrointestinal infection. These types of infections can result in inflammation and long-term changes to gut flora. With this type of IBS diarrhoea and nausea are common.

Some people with this type of IBS have been able to recover completely given time and the correct treatment.

Post-diverticulitis (PD-IBS)

Having diverticulitis might place you at a higher risk of developing IBS. When you have diverticulitis disease, you develop pouches along your digestive tract which become infected and inflamed. Symptoms can be similar to IBS and a small number of patients can develop complications including abscesses and fistulas.

PD-IBS can sometimes develop once the initial disease has been treated.

What are the signs and symptoms of irritable bowel syndrome?

Common symptoms associated with IBS include:

  • Stomach cramps – This could be experienced as a constant pain or as a cramp where your stomach tightens and then the tightness releases, then it tightens again. You may feel worse after eating something and experience relief after a bowel movement.
  • Diarrhoea – Your bowel movements might be loose or watery.
  • Constipation – You may struggle to go to the toilet and if you manage a bowel movement it might be hard and uncomfortable.
  • Bloating – Your stomach might swell up or feel full and uncomfortable.
  • Frequent bowel movements – You will know what is normal for your own body. When IBS symptoms are there, you may need to use the toilet more often, sometimes with urgency.

Other symptoms that some IBS sufferers experience include:

  • Passing a lot of gas/flatulence.
  • Tiredness/lethargy.
  • Nausea.
  • Backache.
  • Passing mucus from your anus.
  • Bowel incontinence (not being able to control when bowel movements happen).
  • Sudden urge to urinate, frequent urination or a feeling of never fully emptying your bladder.

You may go days, weeks or even months without any symptoms then you may experience a ‘flare up’ when they suddenly come back. Sudden flare-ups can sometimes help you to identify ‘triggers’ that make your condition suddenly get worse.

IBS sufferer experiencing sudden urge to urinate

What causes irritable bowel syndrome?

Research is ongoing into the exact causes of irritable bowel syndrome and it is not yet known.

However, IBS has been linked to:

  • Stress.
  • Food passing through the gut either too fast or too slow.
  • Family history of IBS.
  • An oversensitive gut.
  • A gastrointestinal infection.

What can trigger irritable bowel syndrome?

People with IBS can go for long periods of time without having any symptoms and then have a sudden flare-up. This often happens because of a trigger event which could be something they have eaten, drank or otherwise experienced. Once these triggers are known to IBS sufferers they can start to limit and avoid them.

Triggers will vary from person to person and not everything is known about what causes IBS; however, common triggers can include:

  • Certain foods (especially hard to digest foods, processed and high-fat foods and dairy products).
  • Spicy food.
  • Alcohol and caffeine.
  • Infections.
  • Certain medication.
  • Stress.
  • Trauma.

Triggers can cause changes in the body such as dehydration, altering gut bacteria and affecting the highly-sensitive gastrointestinal tract. This may result in a flare-up of IBS symptoms.

Who is at risk of developing irritable bowel syndrome?

Research suggests that you are more at risk of developing IBS if a parent or sibling also suffers from it. Identical twins are also thought to be at a higher risk of both developing IBS.

There is not enough research in this area to suggest a direct cause and effect between genetics and IBS. The familial link could also be down to shared environmental and dietary factors.

Sometimes people develop IBS symptoms after suffering from a gut infection or diverticulitis. This is thought to be due to the inflammation, infection and disruption to the bacteria in the digestive tract that these conditions cause.

Some research also suggests that being overweight is a risk factor for IBS and is also associated with more severe symptoms. There are multiple hormones that live in the digestive tract that help with weight regulation and some research indicates that these hormones exist in abnormal levels in IBS sufferers.

The actual risk factors associated with IBS require further research to prove cause and effect links.

Scientists are currently studying within this field, including looking at the relationship between:

  • Obesity and IBS.
  • Allergies and IBS.
  • Infections and IBS (Post-infectious IBS).

These areas of study will hopefully, one day, be able to give us further answers as to who is most likely to develop IBS and why.

How does irritable bowel syndrome affect the body?

IBS symptoms can be painful, uncomfortable and embarrassing. Sometimes, people feel there is a stigma to suffering from a digestive condition as talking about it is somewhat of a taboo subject. It is important that sufferers of IBS get the treatment that they need and have a network of supportive family and friends around them.

There can also be a psychological impact of having irritable bowel syndrome. This is especially true when people have suffered for a long time, are struggling to find treatments that help or are experiencing IBS in addition to anxiety or depression. In this instance, talking therapies such as CBT might help.

There can also be side effects from some of the medicine you need to take to control your IBS symptoms that affect the body. Your GP will be able to advise you about managing your medication.

Woman with irritable bowel syndrome at work

How is irritable bowel syndrome diagnosed?

If you think you may have IBS or have noticed any worrying changes in your health you should make an appointment to see your GP.

Your GP will want to talk to you about your symptoms and perform some tests. They will also need information about your general health and lifestyle.

If you are experiencing digestive problems and have any of the following symptoms you should treat this with urgency as it could indicate a serious health issue:

  • Sudden, unexplained weight loss.
  • Rectal bleeding, bloody stools or passing blood during bowel motions.
  • Hard lump or abdominal swelling.
  • Heart palpitations, shortness of breath and pale skin.

Once your GP has all of the information about your symptoms and health they may want to perform an abdominal examination. This is to check for any areas of tenderness, lumps or swelling.

There is no specific test for IBS but your GP might want to run tests just to rule out other causes such as an infection, coeliac disease or inflammatory bowel disease (IBD).

If other causes for your symptoms are ruled out and your GP thinks you may have IBS they will go through relevant information and treatment options with you.

If there seems to be any triggers that are making your symptoms worse or any diet and lifestyle changes that might help you, they will discuss that with you also.

How is irritable bowel syndrome treated?

Your GP will advise you about simple changes that you can make to hopefully alleviate some of your IBS symptoms or reduce flare-ups, such as:

  • Try to cook meals from scratch using healthy, fresh ingredients wherever possible.
  • Keep a food diary of meals, drinks and snacks (this will help you to keep a note of what you are eating and also isolate any potential triggers).
  • Exercise regularly.
  • Finds ways to relax (you may want to try mediation, mindfulness or yoga).
  • Try to eat regularly and stick to a routine.

Some IBS sufferers also find taking probiotics helps them to limit their flare-ups or manage their symptoms. These are available in the form of a drink from most supermarkets and also as a pill/capsule from most pharmacies and some health food stores.

  • Avoid skipping meals or eating just before bed.
  • Try not to eat too fast.
  • Avoid/limit alcohol, fizzy drinks and caffeine (no more than three cups of tea or coffee per day).
  • Avoid processed foods.
  • Do not eat lots of spicy or fatty foods.
  • Limit your fruit intake (three portions or 240g maximum per day).

If you are experiencing diarrhoea you might want to cut down on high fibre foods and avoid the sweetener sorbitol because it can have a laxative effect. You can also get medicine from the pharmacy to treat diarrhoea.

If you have bloating, cramps and flatulence from your IBS, eating oats and linseeds may help. You should also avoid foods that are difficult for the body to digest such as broccoli, cauliflower and cabbage. Over-the-counter medicines may also be an option.

Dehydration makes constipation worse. If you get constipated as a result of your IBS it is important to drink plenty of water and stay well hydrated. You should include foods in your diet that contain ‘soluble fibre’ such as oats and barley.

You can also pick up laxative medicine from the pharmacy that can help with constipation; this is usually mixed with water to drink one or more times per day.

If over-the-counter medicines and diet changes are not helping, your GP may prescribe some stronger medicine.

This is usually:

  • Amitriptyline.
  • Citalopram.

This medication can help to ease the symptoms associated with IBS though it is also used to treat depression.

Keeping a food diary

What is a FODMAP?

Speaking to a dietician might help you to navigate through all of the suggested dietary changes that you might need to help with your IBS. You can also do some independent research about this yourself.

A commonly recommended diet for IBS is called a low FODMAP diet.

FODMAP is an abbreviation for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are short-chain carbohydrates which the body struggles to fully absorb, therefore a diet high in FODMAP is associated with different types of digestive problems and conditions, including IBS.

To follow the diet, you have to temporarily reduce high FODMAP foods for a period of time then slowly reintroduce them to see which are causing issues. You should follow this type of diet under the supervision of your GP or nutritionist, who can advise you on how to follow the instructions safely.

This type of diet can be very restrictive but it can be useful to help to identify triggers and ease symptoms of IBS.

Some foods to avoid include:

  • Cow milk.
  • Certain vegetables (including onions, garlic and asparagus).
  • Certain fruit (including cherries and peaches).
  • Wheat based products.
  • Sweets or drinks containing sorbitol.

You should base your meals around low FODMAP foods.

Research into IBS and other FGIDs continues. As new diagnostic techniques are developed and further advancements are made within medicine, hopefully the outlook for IBS sufferers will be a positive one.

Currently, the best advice is to combine dietary and lifestyle changes with medication to manage the condition. You should always see your doctor if you have any concerns about your health or if your IBS symptoms get worse.

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About the author

Vicky Miller

Vicky Miller

Vicky has a BA Hons Degree in Professional Writing. She has spent several years creating B2B content and writing informative articles and online guides for clients within the fields of sustainability, corporate social responsibility, recruitment, education and training. Outside of work she enjoys yoga, world cinema and listening to fiction podcasts.

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