Irritable Bowel Syndrome

Irritable Bowel Syndrome, commonly referred to as IBS is the most common digestive disorder. It is thought to affect about 15% of us at some time in our lives, with women being affected nearly twice as much as men(1).

Not everyone who has IBS reports it to their doctor however, with only about one third contacting the health services. This could account for some of the differences in the reported prevalence between men and women, and even the decreased reporting of IBS among older people, who may become more accepting of chronic pain.

IBS is in reality just an arbitrary definition of a number of digestive disorders that cannot be clinically identified. In other words there are no detectable structural changes inside the digestive tract. The arbitrary definition of IBS is set out in what is called the Rome criteria. A third revision of these criteria (Rome III) came out in 2006(2). 

Symptoms and causes

The Rome criteria mentioned above define IBS as abdominal pain accompanied by a change in bowel habit persisting for at least 3 months. The level of pain must be relieved to some extent by the passing of stools to qualify as IBS. Changed bowel habits should be reflected either as more constipation or more diarrhoea than before.

While a cause is not established, it is thought that the following changes are indicative of the condition:

  1. Abnormal activity of the smooth muscles lining your digestive tract.
  2. Slower or faster transit times for food related to the above.
  3. Bloating of the abdomen.
  4. A heightened response to nerve sensations from the gut.

Other symptoms that can support a diagnosis include nausea, fatigue, backache and an irritable bladder.

There is a sub-definition of 3 types of IBS which affect people in roughly equal numbers. Diarrhoea dominant - IBS-D, constipation dominant - IBS-C and people with both diarrhoea and constipation at different times - IBS-M. The type of treatment or therapy that works best can vary depending on which type you have. 

Increasingly it appears that IBS-D is associated with a condition called SIBO, which is an overgrowth of bacteria in the small intestine(3).

Causes of IBS are various. Stress, digestive infections or just subjecting your gut to too many foods that you don't process too well, are all potential causes.

Conventional treatment

In the better surgeries in the UK, your diet, lifestyle and exercise regime will be discussed in order to enable you to best manage the condition. There are also drug based treatments, although it should be remembered that both short and long term side effects can be expected. This is especially the case if you take antibiotics, antidepressants or some of the antispasmodics.

For constipation

Laxatives, in particular bulk forming laxatives such as Senokot or Fybogel are often used to loosen the stools and enable them to pass more freely through the colon. It is important to drink adequate fluid with these products.

For diarrhoea

Loperamide slows the muscular contractions in the gut. It can cause side effects such as dizziness, drowsiness and skin rashes in some people.

For abdominal distress

Peppermint oil and other anti-spasmodics are normally tolerated fairly well. They can relieve the pain associated with IBS as well as bloating. 

Diet and lifestyle

While there are some pharmaceutical interventions, these are unlikely to work in the long term. It is important to get to grips with IBS using a combination of diet and lifestyle change. If you can do this you may well be able to see the back of IBS for good.

Changing gut bacteria

A key component in managing IBS is to ensure that the right 'friendly' bacteria inhabit your small intestines and colon. Normally the numbers of bacteria increase the lower down your digestive tract you go. So up in the small intestines there are not so many. It is thought with the diarrhoea dominant type of IBS-D, that an overgrowth of unfriendly bacteria in the small intestines (SIBO) is responsible.

One of the most effective ways to encourage the right sort of bacteria to inhabit your gut is a low FODMAP diet. FODMAPs (fermentable oligo-, di-, mono-saccharides and polyols) if you want the acronym in full, are carbohydrates that have the unfortunate habit of failing to breakdown fully in the small intestine. This allows bacteria lower down the GI tract to ferment them, producing gas. The presence of these carbohydrates lower down the GI tract also draws water into the gut by osmotic pressure. More gas and liquid in the intestines can cause pain, bloating, flatulence and diarrhoea.

Preventing a leaky gut

Another major factor that can lead to digestive problems is a leaky gut. The interior of our gastrointestinal (GI) tract is lined with a mucosal layer of cells. Gaps can appear between these cells allowing the contents of our GI tract to reach immune cells in the outer layers surrounding it. When this happens an immune reaction occurs as our immune cells consider the foodstuffs to be invaders from outside, which they effectively are. There is increasing evidence that a compromised GI tract can lead to the IBS-D form of irritable bowel disease(4).

There is a close association between eating too much gluten containing grains and increased intestinal permeability (leaky gut) suggesting that reducing intake of wheat, barley and rye could be a useful first step in countering IBS.

Foods to limit

The foods grouped below are not causes of IBS, but may worsen symptoms. Only a few people will have issues with all these types of fruit and vegetable. If you are struggling with IBS the best approach is to eliminate most of the below and then reintroduce foods one at a time, starting with those you suspect are OK. If you seem to react with one, then take 3 days for your system to settle down and then resume with introducing other foods from the lists below.

Underlined foods are key suspects.


Wheat, onion family [garlic, onions, leeks and shallots], some greens [cabbage, brussels and broccoli], artichoke, asparagus and beetroot. These contain chains of fructose called fructans. Chains of more than 10 molecules are called inulin. Less than 10 molecules and they are reffered to as FOS (fructo-oligosaccharides). Fructans are oligosaccharides - the "O" in FODMAP. Garliconion and Jerusalem artichokes are particularly fructan rich and problematic for some people. 


Legumes such as beans, lentils, chickpeas and cabbage. These contain long chains of galactose (part of the sugar in milk) called galactans. Galactans, like fructans are oligosaccharides - the "O" in FODMAP. Beans and chickpeas especially if underdone can cause problems for some people. When broken down and processed, as with tofu and hummus, problems are generally less severe.


This is present in milk and foods derived from it. Cheese may cause problems for some. Butter and yoghurt are normally OK. Lactose, like table sugar (sucrose) is a  disaccharide - the "D" in FODMAP. Cows, goats and sheeps milk all contain around 5% lactose and are problematic in many.


Fruit sugar is present in most fruits as a monosaccharide - the "M" in FODMAP. Too much dried fruit, apples or pears can cause digestive discomfort for those with IBS.


Lastly, polyols, the "P" in FODMAP are sugar alcohols and are found in sweeteners, and fruits with stones such as peaches, apricots and plums. The sweeteners to be wary of are those ending in "ol", such as xylitol, sorbitol, mannitol and lactitol. Isomalt is also a polyol.


Cutting out bread and all other forms of wheat, rye and barley (beer) is strongly advisable if you are suffering with chronic IBS. It may be hard to think of life without bread, but if IBS is causing you a lot of grief it will be well worth trying out a gluten free diet for a period of 1 month to see if it make a major difference. After a month if you re-introduce and have a bad reaction that is another clear sign that you are intolerant to it. 

Foods you can eat

That's a lot of foods that I'm asking you to reduce. What you now need to know is what foods you can safely eat.

Meat, fish and dairy

Meat, fish and some dairy foods are all nourishing and should not worsen symptoms of IBS. If you have a lactose intolerance then milk and cheese may need to be avoided.

Nuts and seeds

Nuts and seeds are generally OK if consumed in moderation.

Fruit and vegetables

Foods containing soluble fibre can help alleviate gut symptoms. They include the starchy vegetables: potato, sweet potato, parsnip, swedes, turnips, celeriac, carrot, beetroot and squashes. The non-peel part of many fruits are also generally OK with the exception of stoned fruits which cause problems for those sensitive to polyols.

Stress reduction

While what you eat is of key importance to healing your gut there are other aspects of life that affect your gut. In particular stress can make your gut feel worse almost instantaneously.

Stress has been shown to make the inner lining of the gut leaky. It can also change the types of bacteria in our gut. What causes negative stress varies between people. Consider the following areas and if you are aware of problems in a particular area really focus on changing it.

  1. Adequate sleep, 7-9 hours a day is best for the vast majority of us. 6 hours or less really is not good anough and has been clearly shown to be detrimental to health(5).
  2. Take regular exercise that you enjoy. Walking for 1-2 hours, gardening or any sort of outdoor sport will get you outside where you will benefit from sunlight (potentially) and interaction with nature.
  3. Avoid spending too much time on electronic devices such as on the internet or watching TV.
  4. Avoid arguments that don't lead anywhere, especially if you feel worse after them.
  5. Develop coping strategies for stress you can't avoid. For instance if you have to stay in a job you don't like because you need the money, then consider seeing the job in a new light. Stop worrying about how your boss perceives you, your end of year appraisal or other issues. Often they may not be as important in the grand scheme of things as you think.