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What causes irritable bowel syndrome?

What causes irritable bowel syndrome?
The cause is not clear. It may have something to do with overactivity of part or parts of the gut. The gut is a long muscular tube that goes from the mouth to the anus. The small and large bowel (also called the small and large intestine) are parts of the gut inside the abdomen. Food is passed along by regular contractions (squeezes) of the muscles in the wall of the gut. Pain and other symptoms may develop if the contractions become abnormal or overactive. The area of overactivity in the gut may determine whether constipation or diarrhoea develops.

The cause of overactivity in parts of the gut is not clear. One or more of the following may play a part:

Overactivity of the nerves or muscles of the gut. It is not known why this may occur. It may have something to do with overactivity of messages sent from the brain to the gut. Stress or emotional upset may play a role. About half of people with IBS can relate the start of symptoms to a stressful event in their life. Symptoms tend to become worse during times of stress or anxiety.

Intolerance to certain foods may play a part in some cases. However, this is thought to be only in a small number of cases.

Infection and bacteria in the gut. IBS is not caused by an ongoing gut infection. However, in about 1 in 6 cases, the onset of symptoms seems to follow a bout of gastroenteritis (a gut infection which can cause diarrhoea and vomiting). So, perhaps a virus or other germ may sensitise or trigger the gut in some way to cause persisting symptoms of IBS.

Also, in some cases, symptoms get worse after taking a course of antibiotics. Antibiotics kill certain harmless or ‘good’ bacteria in the gut which changes the balance of bacteria types in the gut.

What are the treatments for irritable bowel syndrome?
Many people are reassured that their condition is IBS, and not something more serious such as colitis. Simply understanding about IBS may help you to be less anxious about the condition, which may ease the severity of symptoms. Symptoms often settle for long periods without any treatment. In some cases, symptoms are mild and do not require treatment.

If symptoms are more troublesome or frequent, one or more of the following treatment options may be advised:

The advice about fibre in treating IBS has changed somewhat over the years. Fibre (roughage) is the part of the food which is not absorbed into the body. It remains in your gut, and is a main part of faeces (stools). There is a lot of fibre in fruit, vegetables, cereals, wholemeal bread, etc. It used to be said that eating a high-fibre diet was good at easing IBS symptoms. Then various research studies showed that a high-fibre diet can, in some cases, make IBS worse. So, one recent guideline on IBS (from Clinical Knowledge Summaries – cited at the end) states that ‘high-fibre diets are not recommended for people with IBS’. But since that guideline was published, a review of treatments for IBS (Ford et al – cited at the end) concluded that fibre was good at easing symptoms in some people with IBS. So, the role of fibre can be confusing!

What seems to be the case is that the type of fibre is probably important. There are two main types of fibre – soluble fibre (which dissolves in water) and insoluble fibre. It is soluble fibre rather than insoluble fibre that seems to help ease symptoms in some cases. So, if you increase fibre, have more soluble fibre and try to minimise the insoluble fibre.

Dietary sources of soluble fibre include oats, ispaghula (psyllium), nuts and seeds, some fruit and vegetables and pectins. A fibre supplement called ispaghula powder is also available from pharmacies and health food shops. The recent review of treatments for IBS mentioned earlier mentions ispaghula as the fibre supplement that seems to be the most beneficial.
Insoluble fibre is chiefly found in corn (maize) bran, wheat bran and some fruit and vegetables. In particular, avoid bran as a fibre supplement.
Foods, drinks and lifestyle
A healthy diet is important for all of us. However, some people with IBS find certain foods of a normal healthy diet can trigger symptoms or make symptoms worse. Current national guidelines about IBS include the following points about diet which may help to minimise symptoms:

Have regular meals and take time to eat at a leisurely pace.
Avoid missing meals or leaving long gaps between eating.
Drink at least eight cups of fluid per day, especially water or other non-caffeinated drinks such as herbal teas. This helps to keep the faeces (stools) soft and easy to pass along the gut.
Restrict tea and coffee to three cups per day (as caffeine may be a factor in some people).
Restrict the amount of fizzy drinks that you have to a minimum.
Don’t drink too much alcohol. (Some people report an improvement in symptoms when they cut down from drinking a lot of alcohol, or stop smoking if they smoke.)
Consider limiting intake of high-fibre food (but see the section above where an increase may help in some cases).
Limit fresh fruit to three portions (of 80 g each) per day.
If you have diarrhoea, avoid sorbitol, an artificial sweetener found in sugar-free sweets (including chewing gum) and in drinks, and in some diabetic and slimming products.
If you have a lot of wind and bloating, consider increasing your intake of oats (for example, oat-based breakfast cereal or porridge) and linseeds (up to one tablespoon per day). You can buy linseeds from health food shops.

Individual food intolerance
Some people with IBS find that one or more individual foods can trigger symptoms, or make symptoms worse (food intolerance or sensitivity). If you are not sure if a food is causing symptoms, it may be worth discussing this with a doctor who may refer you to a dietician. A dietician may be able to advise on an exclusion diet. For example, one meat, one fruit, and one vegetable. Then, advise on adding in different foods gradually to your diet to see if any cause the symptoms. It may be possible to identify one or more foods that cause symptoms. This can be a tedious process, and often no problem food is found. However, some people say that they have identified one or more foods that cause symptoms, and then can control symptoms by not eating them.

The foods that are most commonly reported to cause IBS symptoms in the UK are: wheat (in bread and cereals), rye, barley, dairy products, coffee (and other caffeine-rich drinks such as tea and cola), and onions.

Probiotics are nutritional supplements that contain ‘good’ bacteria. That is, bacteria that normally live in the gut and seem to be beneficial. Taking probiotics may increase the ‘good’ bacteria in the gut which may help to ward off ‘bad’ bacteria that may have some effect on causing IBS symptoms. You can buy probiotic capsules (various brands) from pharmacies. The dose is on the product label. You can also buy foods that contain probiotic bacteria. These include certain milk drinks, yoghurts, cheeses, frozen yoghurts, and ice creams. They may be labelled as ‘probiotic’, ‘containing bacterial cultures’, or ‘containing live bacteria’.

There is some evidence that taking probiotics may help ease symptoms in some people with IBS. At present, there are various bacteria that are used in probiotic products. Further research is needed to clarify the role of probiotics and which one or ones are most helpful. In the meantime, if you want to try probiotics, you should keep to the same brand of probiotic-containing product for at least four weeks to monitor the effect. Perhaps try a different probiotic for at least a further four weeks if the first one made no difference.

Other lifestyle factors
Regular exercise may also help to ease symptoms. Stress and other emotional factors may trigger symptoms in some people. So, anything that can reduce your level of stress or emotional upset may help.

It may help to keep a food and lifestyle diary for 2-4 weeks to monitor symptoms and activities. Note everything that you eat and drink, times that you were stressed, and when you took any formal exercise. This may identify triggers, such as a food, alcohol, or emotional stresses, and may show if exercise helps to ease or prevent symptoms.

Antispasmodic medicines
These are medicines that relax the muscles in the wall of the gut. Your doctor may advise one if you have spasm-type pains. There are several types of antispasmodics. For example, mebeverine, hyoscine and peppermint oil. They work in slightly different ways. Therefore, if one does not work well, it is worth trying a different one. If one is found to help, then you can take it as required when pain symptoms flare-up. Many people take an antispasmodic medicine for a week or so at a time to control pain when bouts of pain flare up. Some people take a dose before meals if pains tend to develop after eating. Note: pains may ease with medication but may not go away completely.

Treating constipation
Constipation is sometimes a main symptom of IBS. If so, it may help if you increase your fibre as discussed earlier (that is, with soluble fibre such as ispaghula). Sometimes laxatives are advised for short periods if increasing fibre is not enough to ease a troublesome bout of constipation.

Treating diarrhoea
An antidiarrhoeal medicine may be useful if diarrhoea is a main symptom. Loperamide is the most commonly used antidiarrhoeal medicine for IBS. You can buy this at pharmacies (but it is quite expensive). You can also get it on prescription which may be more cost-effective if you need to take it regularly.

The dose of loperamide needed to control diarrhoea varies considerably. Many people use loperamide as required but some take it regularly. Many people learn to take a dose of loperamide in advance when they feel diarrhoea is likely to be a problem. For example, before going out to places where they know it may be difficult to find a toilet.

Antidepressant medicines
An antidepressant medicine in the tricyclic group is sometimes used to treat IBS. In particular, it tends to work best if pain and diarrhoea are the main symptoms. (Tricyclic antidepressants have other actions separate to their action on depression. They are used in a variety of painful conditions, including IBS.) Unlike antispasmodics, you need to take an antidepressant regularly rather than as required. Therefore, an antidepressant is usually only advised if you have persistent symptoms, or frequent bad flare-ups that have not been helped by other treatments.

Psychological treatments (talking treatments)
Situations such as family problems, work stress, exams, recurring thoughts of previous abuse, etc, may trigger symptoms of IBS in some people. People with anxious personalities may find symptoms difficult to control. The relationship between the mind, brain, nervous impulses, and overactivity of internal organs such as the gut is complex. Some people have found relaxation techniques, stress counselling, cognitive behavioural therapy, psychotherapy, hypnotherapy, and similar therapies useful in controlling symptoms of IBS.

Psychological treatments are generally mainly considered in people with moderate-to-severe IBS, when other treatments have failed. Or, when it seems that stress or psychological factors are contributing to causing symptoms. However, some of these treatments may not be available on the NHS in your area, or there may be long waiting lists.

Other treatments
Various alternative and complementary therapies are sometimes used. For example, studies have shown that certain Chinese herbal medicines may help to ease symptoms in some cases. However, more research is needed to clarify their safety and usefulness.

Newer medicines that affect certain functions of the gut are also being developed and may become useful treatments in the future.

Assess your symptoms – perhaps keep a diary
As you can see from the above section, there are many different treatments that may be tried for IBS. All will have some effect in some people, but none will help in every person with IBS. So, if you are advised to try a particular treatment, it may be sensible is to keep a symptom diary before and after the start of the treatment. For example, before changing the amount of fibre that you eat, or taking a probiotic, or starting medication. You may wish to jot down in the diary the type and severity of symptoms that you get each day for a week or so. Keep the diary going after you start treatment. You can then assess whether a treatment has improved symptoms or not. No treatment is likely to take away symptoms completely, but treatment can often ease symptoms and improve your quality of life.

What is the outlook (prognosis)?
In most people with IBS, the condition tends to persist long-term. However, the severity of symptoms tends to wax and wane and you may have long spells without any symptoms, or with only mild symptoms. Treatment can often help to ease symptoms when they flare up. In a minority of cases, symptoms clear for good at some stage.

IBS does not shorten your expected lifespan, it does not lead to cancer of the bowel, and does not cause blockages of the gut or other serious conditions.


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