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Constipation And Irritable Bowel Syndrome

People say they have constipation if they think that they defecate too infrequently or with too much effort, if their stools are too hard or too small, if defecation is painful, or if they feel that they haven’t emptied their rectum completely. This can also be confused by the fact that what is constipation to one person may be the usual situation for another.

Today, people and their doctors are more concerned with discomfort than with the number of stools passed or their size and shape, but a century ago constipation was big business. It was considered to be the scourge of civilisation, the source of many diseases and an explanation for all those symptoms that couldn’t be explained by anything else. People became obsessed with keeping their bowels regularly cleared. Laxative sales took off, and high fibre-products were highly promoted. As a house officer in Plymouth when I qualified over 20 years ago, we would first do a ward round of the patients and then one of their stools – all carefully saved for our inspection by the nurses! Stools were serious stuff, and lectures on the evils of a low-fibre diet were commonplace.

But somehow constipation was already falling off its pedestal as the disease of civilisation. Perhaps it was the failure of laxatives to transform lives, the need for a more sophisticated diagnosis or indeed a greater understanding of the links between the mind and the gut. And so the concept of the irritable bowel syndrome (IBS) evolved and became popular. Today, people more readily admit to an irritable bowel and can accept it, probably correctly, as an explanation of many of their symptoms.

Constipation remains a common problem. Most of us will become constipated from time to time, often for no clearly definable reason. Some of us will have constipation as part of the constellation of symptoms that form irritable bowel syndrome. About a third of people with irritable bowel syndrome have constipation as one of their main problems (described as IBS-C).



Is there any right number of times to open my bowels each day?

About 50% of people open their bowel once a day, and most people open their bowel at least three times a week. But there is a wide variation among people such that it is perfectly normal for some people to open their bowels several times a day, whereas others are comfortable with just one bowel motion a week. There is no hard and fast rule. You should listen to the ‘call to stool’ from your bowel and go as often as you need to.

I have heard that it is abnormal to open the bowels more than three times per day, or less than three times per week. Is this so?

These are definitions used in studies, surveys and clinical guidelines. They suggest that something may be wrong, such as irritable bowel syndrome, or that the individual is at one or other extreme of the normal range.

Should I try and go regularly?

No, you don’t need to do this. Most people have an irregular pattern and do not have bowel movements every day or even the same number of bowel movements each day.

What should my stool look like, and what consistency should it be?

The consistency and shape of your stool may be a better guide to how fast or slow your bowel is than the number of times that you go. Passing separate hard lumps, like nuts, or a lumpy sausage suggests that your bowel may be slow or constipated. This is because the longer a stool remains in the bowel, the more water is absorbed from it and the harder it becomes. However, it doesn’t matter what your stool looks like or what consistency it has as long as you are comfortable. If the stool is so hard that you frequently have to strain, you are constipated. Mucus (slime) passing along with the stool is normal in some people but is more common in people with an irritable bowel.

The Bristol stool chart

The Bristol stool chart


When should I worry about what my stool looks like?

A yellow, particularly foul-smelling stool that is loose, tends to float and is difficult to flush away is called steatorrhoea. It suggests that the digestion and absorption of food, especially fat, is impaired. You should consult your family doctor if you suspect that you are getting steatorrhoea.

A tarry black, loose and shiny stool with a different smell is called melaena. This indicates bleeding from high in the gastrointestinal tract, usually the stomach or duodenum (see Figure 1.1). Blood passing through the gut becomes partially digested, losing its red colour and turning a shiny black. Blood in the gut acts as a laxative so the stool is loose. When the bleeding is still going on, the stool is liquid and shiny black. When the bleeding has stopped and previously bled blood is coming out, the stool loses its shine but remains black. If you think that you have melaena, you should phone your family doctor as you may need admission to hospital.

Bright red blood, described by doctors as ‘fresh’ blood, usually comes from the lower parts of the gastrointestinal tract. It looks like blood because there has not been time for any digestion to take place. If there is blood just on the toilet paper, or on an otherwise usuallooking stool, the blood is likely to be coming from the anus or the rectum. Commonly, this is from haemorrhoids, which are large rectal veins, but it can be due to polyps (small mushroom-like growths, usually benign) or tumours (larger growths, sometimes malignant and sometimes benign) and should be taken seriously, especially in people over the age of 50. If there is fresh blood mixed in with the stool, the site of the bleeding is probably above the rectum but within about 40 centimetres (16 inches) of the anus. Common causes include inflammatory bowel disease, polyps, tumours and diverticular disease.

This symptom should be investigated at any age, usually with a flexible sigmoidoscopy. If you are passing small amounts of blood (small specks to several teaspoons), make an appointment with your family doctor. If you are passing cupfuls of blood, phone your doctor as you may need admission to hospital.

Sometimes I get some slime coming out with my stool. Does that mean that I have irritable bowel syndrome?

Mucus (slime) is common in irritable bowel syndrome and in other conditions affecting the bowel. But it can also occur in those who do not have irritable bowel syndrome. It suggests that the rectum is irritated, much as the nose can be irritated by a cold or an allergy. But just as you can get mucus from the nose without having anything wrong, mucus from the rectum can be normal in some people.

I only open my bowels once or twice a week. I’m perfectly happy with this, but am I doing myself any long-term harm by not going more regularly? If you are comfortable, it does not matter how infrequently your bowels are open.

There was a theory, which some people still believe, that not clearing the bowel frequently would cause ill-health in both the short and the long term. This theory, called ‘autointoxication’, suggested that the rotting waste in the bowel produced toxins that could be absorbed to produce disease. This idea started in ancient Egyptian times and became the standard medical view in the 19th century. As a popular American health manual warned in the 1850s, ‘daily evacuation of the bowels is of the utmost importance to the maintenance of health’. Without this daily movement, ‘the entire system will become deranged and corrupted’! Many symptoms were blamed on constipation, including fatigue, poor sleep, headaches, poor memory, bad breath, a coated tongue, depression, aching muscles and joints, hair loss and impotence. It was felt to be the cause of colon cancer and even heart disease.

Processed foods were blamed then, as they are today. ‘The whiter your bread, the sooner you’re dead’ is a saying attributed to the famous surgeon Sir William Arbuthnot Lane, who popularised a treatment for constipation that involved removing the large bowel. The cereal All-Bran was introduced in the early 1900s precisely to combat this autointoxication, as were any number of other bran cereals; stimulant laxatives were widely used, and colonic irrigation was born.

A number of experimental studies in the 1910s cast doubt on the idea of bowel toxins getting into the circulation, so autointoxication as a theory slowly faded away during the 1920s. But in the 1970s, the theory was revived by the English surgeon Dennis Burkitt. When he was in Uganda, he noticed that Africans produced several times more faeces than Westernised people did. In addition, their faeces were soft and produced with virtually no discomfort, again in contrast to Westernised people. Burkitt then suggested that one major cause of Western disease was eating large amounts of refined carbohydrates, which contain little dietary fibre. Burkitt’s book Don’t Forget Fibre in your Diet, published in 1979, spurred a popular revolution in diet.

Today, the causes of various diseases and how they may relate to our diet are closely studied in large studies over several countries. It seems that our longer-term health is improved by dietary fibre and that constipation may increase the risk of diverticular disease and bowel cancer. But there is no evidence for ‘autointoxication’ as a cause of chronic fatigue, headaches, muscle pains or any of the other myriad symptoms we may develop. What is also clear is the wide variation in normal function between healthy people. So after all this information, the answer is quite short – if you are comfortable with your current bowel habit, you do not need to make any changes.

Should I set aside a specific time to open my bowels?

The bowel tends to be more active in the morning, and distension of the stomach following breakfast may also stimulate the bowel. If that describes you, you would be wise to allow enough time in the morning to attend to your bowel. If you keep suppressing the need to go to the toilet, the urge to defecate may get weaker, and this is one way in which people can become constipated.

Is there any best position to sit on the toilet?

When a person is standing up, there is an angle of about 90 degrees between the rectum and the anal canal. This is there to help with continence, that is, to help keep the faeces in during our normal activities. So, to defecate successfully, the anal canal and rectum must be in as straight a line as possible. This is achieved by bending at the hips. The ideal is a squatting position, but sitting down is more comfortable.

When you are sitting on the toilet, the best position is to place your elbows on your knees, keep your back straight, push your belly out, pretend to blow up a balloon so as to increase the pressure in your chest and abdomen and bear down. Lifting your feet off the ground will also help.

The best position to sit on a toilet

The best position to sit on a toilet


So are squatting toilets better?

Squatting does make defecation easier, so if you have problems passing stool a squatting toilet may be better. However, in cultures where this is the norm, haemorrhoids are more common.



What causes constipation?

When constipation is the main symptom, the underlying problem is usually irritable bowel syndrome or what is called idiopathic constipation (which means constipation without an obvious cause).

There are many causes of constipation. It is often impossible for any doctor to give a precise explanation of why a particular person has become constipated. There may be a multitude of possible factors, a combination of factors or even no explanation at all. The distinction between idiopathic (unknown aetiology) constipation and constipation-predominant irritable bowel syndrome is also unclear. It’s rare for cancer to show up with constipation as its main symptom.

It is a widely held belief that the main cause of constipation is insufficient dietary fibre, but this belief is not supported by research studies. Although more fibre in the diet will help constipation, people who are constipated do not actually eat less fibre than those who are not. Neither do they drink less fluid, and drinking more fluid doesn’t usually help. There are many conditions and treatments associated with constipation, and the symptoms associated with those other conditions are usually more obvious. When people say that constipation is their major symptom, the problem is usually irritable bowel syndrome or idiopathic constipation.


Causes of Constipation


Lifestyle Causes





Inadequate fibre intake

Although this is often given as cause, most people with constipation do not in fact eat less fibre than those without it

Inadequate food

Constipation always follows starvation

Suppressing or ignoring the urge to defecate

This is possibly the most common cause


Lack of movement is a common cause of constipation in those who are elderly and ill. Exercise increases bowel activity.


Gastointestinal causes





Irritable bowel syndrome

About a third of patients with irritable bowel syndrome have mainly constipation (IBS-C), and irritable bowel syndrome is one of the most frequent causes of constipation.

Poor function and lack of co-ordination of the pelvic floor muscles. The doctor might call this pelvic floor dyssynergia or anismus.

Defecation involves several muscle groups that need to contract and relax in the correct pattern. For example, the anal muscles must relax as the rectum contracts to push the stool out. If this does not happen, there is a feeling of blockage.


This is a bulging of the front wall of the rectum into the back wall of the vagina. It may mean that the force of defecation is directed towards the vagina rather than down towards the anus.







Opiate-based analgesics such as codeine, dihydrocodeine, morphine, diamorphine and others

Constipation is a common side effect of powerful painkillers that contain opiates.

Antidepressants of the tricyclic type, including amitriptyline, imipramine and lofepramine

Constipation is a side effect of this class of antidepressant. Despite this, low-dose amitriptyline is often used to treat irritable bowel syndrome that has pain as its main symptom.

Iron tablets

iron tablets can also cause diarrhoea.


Hormonal and metabolic causes





Hydrothyroidism (an underactive thyroid)

It is routine practice to take blood test for thyroid function in people who go to the doctor with constipation, although in my expereince it is rarely a factor.

Hypercalcaemia (a raised blood calcium level)

People with a very high calcium level are ill with a variety fo symptoms, including nausea, vomiting, fatigue, tirst and passing a lot of urine. Constipation is usually present but tends to be the least of their problems. Blood calcium levels are routinely measured in blood test that may be taken to diagnose other problems.


This is a very rare disorder of haemoglobin production – although I ahve often tested for porphyria in people with otherwise unexplainable symptoms, I ahve never diagnosed it. It can show up with severe abdominal pain and constipation. The initial diagnosis is with a simple urine test.


Neurological disease





Parkinsons disease

Constipation is very common due to a combination of factors, including side effects from the drug treatment, deterioration of the nerves supplying the gut, and lack of mobility.

Multiple sclerosis and spinal cord damage

In these, there is a combination of nerve damage and reduced mobility.


Psychological causes






Constipation is a common problem, probably because of a combination of factors, including the disease itself, reduces activity, reduced food intake and side effects from drug treament.

Anorexia nervosa

People withanorexia are usually very physically active, but exercise does not make up for the lack of food intake in terms of preventing constipation. Constipation is an inevitable consequence of starvation.


I don’t like using the toilets at work. If I feel I want to go, I try to hold on until I get home. Am I doing myself any harm?

One of the functions of the large bowel is to hold the stool until it is convenient to pass it. Suppressing the ‘call to stool’ from time to time is quite natural. But doing so on a regular basis may significantly slow the bowel and make it harder to recognise the signs of needing to go to the toilet.

In a fascinating experiment, healthy subjects were asked to ignore their normal bowel habit and hold on for as long as possible. Their bowel habit, and the time it took for food to pass through their bowel, was carefully assessed before and after this. After just 3 days of ‘holding on’, half as many stools were passed, and the whole bowel slowed down to such an extent that the total time taken for food to pass through it doubled!

But I still don’t want to use the toilet at work. Do you have any other suggestions?

The bowel is naturally more active in the morning. You may be able to train your bowel to open before you go to work. But this does mean having enough time for a relaxed breakfast. Filling the stomach with food increases muscle activity in the bowel through a mechanism called the gastrocolic reflex. This will encourage the call to stool by increasing the strength of muscular contractions in the rectum and help with defecation. While your bowel is getting used to the new pattern, it may help to take a laxative before going to bed.

Are some people’s bowels simply too slow?

Yes, it’s called slow-transit constipation. We can measure the time it takes for food to pass through the gut by tracking the passage of small, solid, pill-sized balls along it. These balls are made of inert (unreactive) materials that show up on X-rays and are not digested in the gut. The average time it takes for something to travel the whole length of the gut is 50 hours. In over 95% of healthy people, the time is less than 70 hours. But in some constipated individuals, this time is prolonged by several days, and in severe cases by several weeks. It is a particular problem in young women, in whom the constipation is often associated with a lot of bloating and pain. People who have this ‘slow-transit constipation’ often say that they rarely feel a message to go to the toilet.

There are many reasons why people ignore the body’s message that they need to go – no time to go to the toilet, no convenient toilet, too busy to hear the call to stool, or a painful or sore anus. Whatever the reason, it seems that the bowel slows down within a surprisingly short time. Moreover, the longer the stool remains within the bowel, the harder it will get as more water is absorbed from it. As a result, there is constipation, and in some people this will become an ongoing problem.

Why do I get constipated when I go on holiday?

This is a common problem. People often attribute it to a change in diet or a lack of fluid, but there are more likely explanations. It is usually just not convenient to listen to the call to stool in the rushed preparations before a holiday – and even less so while travelling. There is nothing wrong with occasionally ignoring or suppressing the urge to defecate, but you have to accept that the longer the stool remains in the bowel, the more water will be absorbed from it and the harder it will get. Stress, too, may slow the bowel down, even when the stress itself is part of the fun.

If I’m getting stressed, then, how will this affect my bowel?

In simple terms, the bowel is regulated by two sets of nerves: the sympathetic system and the parasympathetic system. The parasympathetic system tends to increase the secretion of digestive juices and speeds up the action of the bowel. The sympathetic system slows the bowel down. The sympathetic system has evolved to help us cope with periods of intense physical and mental stress. It diverts blood flow towards the brain and muscles and away from the gut and the kidneys. This is to help the ‘fight or flight’ response, maximising muscle strength and mental agility while temporarily lessening the function of other organs. In simple terms, you don’t want to defecate while you are being chased by a lion. It’s when the stress continues that constipation can become a problem.

I have depression as well as irritable bowel syndrome. The antidepressants have really helped but they make me very constipated. I don’t want to stop them. What can I do?

The constipating effect of some antidepressant drugs is due to an effect on the nerves supplying the bowel. The nerves that stimulate bowel activity (the parasympathetic system) communicate with the bowel by secreting a chemical called acetylcholine. This binds to specific receptors on the bowel cells that are called cholinergic receptors. Many drugs work by blocking cholinergic receptors – so they are said to have ‘anticholinergic properties’. Some antidepressants work by blocking cholinergic receptors within the brain, and it is inevitable that they will have an effect on the rest of the body too, for example slowing the bowel. Although the constipation may be helped by more fibre and exercise, laxatives may be necessary.

I’ve been told I have a rectocoele. What is that?

The rectum lies directly behind the vagina. It is separated from the vagina by a thick, fibrous membrane that may weaken with age or if there has been any vaginal damage while giving birth. This means that when the pressure within the rectum increases to push the stool out during defecation, the front wall of the rectum may herniate (protrude through) this membrane, pushing into the back of the vagina. Defecation becomes difficult because the force becomes directed towards the back of the vagina rather than down towards the anus.

Sometimes a woman will report that defecation begins normally but never feels complete – the stool seems to get ‘stuck’ on the way out, and no amount of straining seems to shift it. Women develop manoeuvres to help, the most successful of which involves placing two fingers in the vagina to support its back wall. Treatment involves softening the stool with fibre and laxatives. You must avoid straining as this only worsens the condition. Occasionally, an operation may be necessary to repair it.

How do I know if I have just constipation, or whether it’s irritable bowel syndrome and constipation?

There is no clear-cut distinction but more of a continuum of symptoms. Some people just get constipated, and are completely better once their constipation has been relieved. Others have a more complicated problem with pain and bloating that persist even when their bowel is empty. The latter have irritable bowel syndrome.

About a third of people with irritable bowel syndrome tend to be constipated (denoted as IBS-C), a third tend to suffer from diarrhoea (called IBS-D), and a third suffer from both constipation and diarrhoea, with a mixed or alternating bowel habit described as IBS-A (or IBS-M). But some people are constipated without any other symptoms that suggest irritable bowel syndrome. Table 7.2 is adapted from the criteria developed by an international group of experts to provide a standard way of identifying patients for clinical trials. These are known as the Rome criteria and are now also used in clinical practice.

According to these criteria, the most important difference between IBS-C and constipation is the amount of pain and abdominal discomfort in irritable bowel syndrome. In practice, however, I do not find this distinction useful as most constipated people will be uncomfortable, and most of those with IBS-C will be more comfortable once their constipation has been relieved. Symptoms left over after relieving constipation that are not attributable to other conditions tend to be ascribed to irritable bowel syndrome.



What is dietary fibre?

Dietary fibre is indigestible plant carbohydrate (mainly substances called cellulose, pectins and lignins from the plant’s cell wall). It passes through the small bowel without being digested and into the large bowel, where bacteria partially metabolise it into gas, fluid and substances called short-chain fatty acids. These short-chain fatty acids are absorbed by the large bowel and are an important nutrient for the bowel. Most of the rest of the fibre passes through the bowel in the stool, along with water and gas trapped in it and bacteria living on it. Fibre therefore produces a softer, wetter, bulkier stool that is easier to pass.

What is the difference between soluble and insoluble fibre?

There are two major types of fibre – soluble and insoluble. Soluble fibre is broken down by bacteria in the colon to produce energy and gas, and bulky stools. This fibre forms a gel-like substance that can bind to other substances in the gut. It also has the extra benefits of lowering cholesterol levels and slowing down the entry of glucose into the blood, thereby improving blood sugar control. Insoluble fibre is less easily broken down by bacteria in the colon but holds water very effectively (up to 15 times its weight in water), which contributes to an increase in stool weight. It is this fibre that is often referred to as ‘nature’s broom’ in that, by passing right through the gut, with extra water, it helps to clear the bowel out. Plant foods contain a combination of both types of fibre, but some plants contain more of one type than the other.

Sources Of Dietary Fibre

Mainly soluble fibre

Mainly insoluble fibre


The skin and pips of fruit and vegetables


Wholegrain cereals (wheat, rye, rice)

Pulses (peas, beans)









Am I eating too little fibre?

Surprisingly, most studies that have compared diet between people with and without constipation have found no difference in the amount of dietary fibre that they eat or the amount of fluid that they drink. The following table shows the results from two studies, although many more have been done. One explanation for these results is to say that most of us actually do not eat enough fibre, but only some of us are afflicted by constipation. In other words, fibre intake is only one factor.

Results From Two Studies In Dietary Fibre


Number of
people studied

Fibre intake

Fluid intake

People with slow bowels




People with normal bowels




People who say they are constipated




People who say they have a normal bowel habit





So how much fibre should I have?

The usual recommendation is 30 g a day, but this is not easy to achieve! The table below shows the fibre content of some common foods. The fibre content is given in the nutrition information that now comes with foodstuffs, and a full list can also be obtained from the US Department of Agriculture, Agricultural Research Service (see appendix).

If you want to use fibre to help your constipation, it is usually best to start with small additions of up to 10 g a day. Sachets of supplementary fibre usually contain 3.5–5 g of fibre.

Fibre Content Of Common Foods


Amount Of Fibre

Apple (with skin)






Wholemeal bread (1 slice)


Ryvita (1 slice)


Bowl of bran


Bowl of muesli


Bowl of cornflakes


Baked beans (small can)


Lettuce (1 leaf)


Lettuce (1 iceberg)




Cucumber (large)


Pepper (1 sweet red, raw)


Grapes (10 grapes)


Nuts (24 almonds)


Potato (boiled in skin)


Oat bran (cooked, 1 cup)



But if I eat more fibre, will it help my constipation?

Eating more dietary fibre is the most common first recommen dation made by healthcare professionals if someone with constipation comes to see them. Indeed, studies comparing psyllium (Ispaghula husk) or bran with a dummy treatment (placebo) have shown that the frequency and bulk of the stools increases with the fibre.

Although in my experience as a hospital specialist, fewer than 25% of constipated people are helped by an increase in dietary fibre, the limited success of fibre seen by specialists probably occurs because the people referred to them have the worst constipation. Those with less severe symptoms successfully treat themselves or are managed by their family doctor.

I tried taking more fibre, but it just made me more bloated without helping my bowel at all. Why is that?

The usual advice is to keep taking the extra fibre. The fibre may take several days to pass through your large bowel, and it takes time for the extra water that it holds in your bowel to have an effect. So until your bowel empties, it is probably inevitable that the extra bulk, and the wind generated as the bacteria digest some of the fibre, will make you feel more bloated. The excess bloating may well settle down as your bowel adjusts over a few weeks.

For some people, such as myself, life is too short to try this approach! The easiest way to relieve the constipation is with a laxative that stimulates the bowel to move. You can then use extra fibre to stop the problem coming back.



What are the different types of laxative that I could buy at a pharmacy?

Laxatives can be roughly divided into several groups; these are called bulk-forming, osmotic, emollient (also called faecal softeners) and stimulant.

Bulk-forming laxatives

Bulk-forming laxatives are fibre. Like dietary fibre, they work by providing a surface area and nutrients for bacteria to grow and multiply, as well as by drawing water into the bowel. To help this, and to prevent the fibre congealing into a solid mass, you should drink plenty of fluid. The stool will then become bulkier and softer. Fibre does not directly stimulate the muscles of the bowel. It is usually said that the increased bulk of the stool stimulates the muscles of the bowel wall to push the stool out more quickly and that the increased softness of the stool helps this. But although most studies confirm that fibre increases stool bulk and relieves constipation, the time taken for food to pass through the bowel is not affected.

Because the fibre is metabolised by bacteria to make gas, bloating and flatulence are frequent side effects. Taking a bulking agent into an already full bowel usually leads to discomfort, at least to start with. Hence once you decide to treat your constipation with extra fibre, it is essential to persevere for at least a week if not longer.

Osmotic laxatives

Osmosis is the process by which water distributes itself so that the concentration of molecules dissolved within the water is equal between different parts of the body – balancing the concentrations out between these different parts. If we take in substances that are soluble in water but cannot be absorbed from the gut, we can draw water into the bowel from the body and keep it there.

The most commonly used osmotic laxative is a sugar called lactulose, which cannot be digested. It comes as a sweet-tasting syrup. Like sugar, it can absorb a great deal of water. But unlike ordinary sugar, it cannot be digested or absorbed, so it passes out unchanged in the stool. By holding a lot of water within the stool, lactulose softens the stool, and in large doses it can cause diarrhoea. Unfortunately, some bacteria within the bowel can metabolise lactulose to produce gas. Thus, wind and bloating are a common side effect. For most people lactulose is a safe, gentle but relatively weak laxative.

Magnesium is poorly absorbed from the gut, so magnesium salts also act as osmotic laxatives. When magnesium is combined with hydroxide as an alkali – to form magnesium hydroxide (Cream of Magnesia) – it is also a useful antacid. Magnesium can be a potent laxative in some people, such that some people who take magnesium supplements will complain of diarrhoea. Magnesium is also sometimes included in so-called ‘natural’ bowel cleansers or detoxifying products.

More recently, osmotic laxatives based on polyethylene glycols have been introduced. Polyethelene glycols are inert (unreactive), water-soluble compounds formed from ethylene oxide; they are a bit like polythene but soluble in water. They have a very high osmotic activity, meaning that they hold very large quantities of water. In addition, neither the human gut nor the bacteria in it digest them, and they pass right through the gut unchanged. They are more effective than other osmotic laxatives, with less bloating and wind as side effects. As well as being used as laxatives, they are also used as bowel-cleansing agents when the bowel needs to be cleaned out before surgery or tests such as colonoscopy.

Emollient laxatives

Emollient laxatives, also called faecal softeners, consist of mineral oil and docusate salts. Mineral oil can be given by mouth (orally) or by enema; it penetrates and softens the stool. The oldest of these laxatives is liquid paraffin. Although it was once frequently used both orally and as an enema, it is now rarely recommended, for a variety of reasons. It can interfere with vitamin absorption if taken regularly, and it can also be absorbed from the gut and deposited in the liver and spleen. Moreover, leakage of paraffin from the anus can irritate the skin. In previous times, when debilitated patients were encouraged to take liquid paraffin before bed, vomiting and aspiration in bed led to an unpleasant type of pneumonia.

An enema containing arachis (peanut) oil is still occasionally used to soften compressed and hardened stool in the lower bowel. This occasionally occurs in people with prolonged severe constipation, especially if they have been immobile. The bowel may be almost blocked by stool (sometimes called faecal impaction) allowing only water and wind to pass (sometimes called overflow diarrhoea).

Docusate and Dioctyl sodium preparations are sometimes classed as faecal softeners and sometimes as stimulant laxatives. They act mainly to reduce the surface tension of the stool, which allows a greater mixing of water and fat. They may also stimulate the bowel wall to secrete more fluid. Although they are still sold as laxatives, studies comparing them with an inactive treatment (a placebo) have failed to show any change in the water content of the stools, in stool weight, in frequency of defecation or in how long it takes the gut contents to go through the colon after docusates have been taken in the recommended doses, and it is unclear whether they do anything at all. They may, however, be worth trying if you want something very gentle.

Stimulant laxatives

Stimulant laxatives act predominantly by increasing muscle contractions in the bowel wall so that stool is passed more effectively. Castor oil has been known as a stimulant laxative since ancient times. It has an unpleasant taste and makes people sick, as well as leading to severe cramping pains, so very few people like taking it. Surprisingly, it may find a new role in stimulating labour at the end of pregnancy.

The anthraquinones are compounds produced by several different plants, including senna, casacara, frangula and rhubarb. They are metabolised by the bacteria in the large bowel to produce compounds that increase the secretion of water into the bowel and stimulate muscle activity in the bowel wall. A large variety are available at pharmacies without prescription. Like most herbal remedies, the preparations are unrefined and contain mixtures of various chemicals. It is therefore difficult to advise on a dose, but they are generally considered to be safe and effective. They usually work 8–12 hours after dosing so are commonly taken in the evening or before bed to promote the natural increase in bowel activity that occurs in the morning.

Bisacodyl is taken as a tablet and is available over the counter. It has to be converted to an active compound by bacteria in the large bowel and stimulates defecation 6–8 hours after being taken. The usual dose is 5–10 mg before bed, but the dose can be increased to 20 mg. Bisacodyl suppositories work much more quickly: within 15–30 minutes.

Sodium picosulphate is similar to bisacodyl and is also available as over-the-counter tablets. It is better known to generations of doctors, nurses and patients as the bowel-cleansing agent Picolax, in which it is combined with a magnesium salt (magnesium citrate) to produce a very powerful stimulant laxative.

So which laxative should I use?

This is very much a matter of trial and error. There is a lot of subjective opinion but very little experimental evidence of which laxative works best for different problems, so you should be encouraged to experiment for yourself.

Are there any new types of medicine for constipation, or are the ones you’ve mentioned above the ones I should try?

Tegaserod is a new drug treatment for severe constipation and irritable bowel syndrome that has constipation as its main feature.

What about enemas and suppositories?

You can buy laxatives to administer yourself directly into your rectum in the form of suppositories or enemas; they act in a similar way to the equivalent medicines taken by mouth. They usually work within 1 hour, and often within 15 minutes. Glycerine suppositories draw water into the rectum from the bowel wall. In this way, they soften the stool and, by increasing the volume within the rectum, can stimulate the passage of the stool. Bisacodyl suppositories can directly stimulate a bowel action, and a combination of a bisacodyl suppository with a glycerine suppository is sometimes helpful.

Enemas are more effective than suppositories but are more difficult to administer yourself. Phosphate enemas are often used in hospitals and can be used at home. They draw a large amount of water from the bowel wall into the gut. The resulting rapid distension of the lower bowel usually gives a very effective bowel motion.

I used to be very comfortable taking Ex-lax, but it’s now no longer available. Why is that?

Ex-lax was popular on both sides of the Atlantic. It contained phenolphthalein, which was until recently the main component in numerous over-the-counter laxatives. As well as stimulating the large bowel, it reduced the absorption of fluid from the small bowel so that more water was delivered to the large bowel, which in turn gave softer stools. However, after a 2-year study showed that rats and mice fed 50–100 times the human dose of phenolphthalein developed various tumours, the US Food and Drug Administration reclassified phenolphthalein as ‘not generally recognised as safe and effective’. Although the only data on laxative use and human cancers indicate that laxatives do not increase the risk of large bowel and other cancers, phenolphthalein-containing laxatives were voluntarily withdrawn and largely replaced with senna-containing compounds (Ex-lax Senna).

So do they actually know whether laxatives can cause cancer?

Cancer of the large bowel is the second most common cancer in people, so a great deal of research has been done on it. Although laxatives containing phenolphthalein were withdrawn due to fears of a cancer risk in animals (see the previous question), animal studies using currently available laxatives show no increased risk of cancer. Moreover, in the many studies of cancer of the bowel in humans, no association with laxative use, either past or present, has been shown.

I’m worried about laxatives damaging my bowel in some other way, though. Could this happen?

Laxatives are safe to use. The belief that they can damage the bowel when taken for prolonged periods is a myth.

But I have been told by several doctors and nurses to only use laxatives for a short period. Why do they think that there is a long-term problem with laxatives?

There is a widespread belief among healthcare professionals and lay people that stimulant laxatives used for any significant stretch of time can lead to permanent damage to the nerves and muscles of the bowel wall. The result is a bowel that is even slower than before, so the person ends up dependent on laxatives to keep it going. Stimulant laxatives are therefore traditionally recommended only for short-term use, meaning a few days to a few weeks. However, the idea that they can damage the bowel is so prevalent that many individuals and their doctors will not consider using these compounds even for severe constipation, relying instead on the less effective fibre preparations. Even osmotic laxatives, which have never been suggested to have a detrimental effect on long-term health, have been tarred with the same brush.

There are several reasons why people believe that stimulant laxatives can damage the bowel. A study published in 1968 looked at large bowels surgically removed in an attempt to relieve severe constipation. These showed damage to the nerves supplying the bowel (the enteric nerves) and wasting of the muscle in the bowel wall. Further studies in later years confirmed an association between long-term severe constipation, laxative use and enteric nerve damage. But most of the patients studied had used laxatives for more than 10 years in daily doses that exceeded the recommended daily dose by a factor of 18! Moreover, it is far from clear whether the damage seen was due to laxatives no longer in current use, to taking laxatives still available, to excessive doses or to a disease process of the large bowel itself that, by causing the constipation in the first place, meant that the laxatives were taken to try and cure it. Indeed, damage to the enteric nerves is seen in conditions that specifically affect the bowel, such as inflammatory bowel disease, and in diseases that affect nerve function generally, such as diabetes.

More recently, it has been shown that individuals with severely slow bowels (what is called colonic inertia) have fewer nerve cells in their bowel wall. The implication is that this is the initial problem, part of the disease itself, and not a consequence of laxative use. Furthermore, a study that compared the structure of nerves in the bowel wall between constipated people taking stimulant laxatives and constipated people not taking laxatives showed no significant difference.

In summary, modern research does not support the idea that laxatives induce bowel damage. It is therefore unlikely that stimulant laxatives used regularly in the recommended doses will harm the bowel. I recently had a colonoscopy. They looked around my bowel with a camera, took samples and told me that I had ‘melanosis coli’ – damage to the bowel wall caused by laxatives. What is this?

Melanosis coli is an easily seen brown pigmentation of the bowel wall. It may occur within months if you regularly use anthraquinone laxatives such as senna or rhubarb. It can last for months after stopping laxative use.

Each cell in the lining of the bowel lives for about 6 days before it dies and is replaced. Its debris is taken up by scavenger cells called macrophages. Anthraquinone laxatives stain this debris, so when it is taken up by macrophages, it gives the bowel wall a brown discolouration. This is of no clinical significance. In fact, it makes it easier to spot other, more important problems if you are having a colonoscopy.

Will I become dependent on laxatives once I start using them?

Most people use laxatives intermittently, just when they feel constipated. This may be every few days, every week or just occasionally. Some people do have to use them regularly to avoid constipation. There is nothing wrong with this. If you stop using them, the worst that can happen is constipation, and it will be no worse than the constipation you had before you started.

If I continue to use laxatives, will they become less effective? Will I need to continually increase the dose of laxative that I use?

It has been said that, after months or years of regular use, the bowel’s response to laxatives will diminish, so larger and larger doses will be needed to give the same effect. This is said to be a particular problem with stimulant laxatives, which are recommended for short-term use only. Indeed, in one small study, two-thirds of patients currently using sodium picosulphate (a strong stimulant laxative) claimed to have increased their dose over 10–20 years of use. We don’t know whether this was because the laxative became less effective or because their constipation got worse with time.

In animal studies, senna-type laxatives and bisacodyl (a stimulant laxative) were given to rats and mice in large doses for prolonged periods without any signs of loss of effect. Moreover, in a study looking at people with spinal cord injuries who required bisacodyl (a stimulant laxative), no loss of effect was seen over periods ranging from 2 to 34 years.

In summary, although some patients with severe constipation undoubtedly do need to increase their use of laxatives over time, this is more likely to reflect worsening constipation. In most people regularly using standard doses of laxatives, no tolerance develops, and the laxative remains effective. So you are highly unlikely to become dependent on your laxative.

I’ve been told that, if I use laxatives, I could lose too much potassium from my body.

In clinical practice, it is not unusual to see patients with a low blood potassium level (called hypokalaemia) which makes them feel tired and weak. In people with gastroenteritis, for example, large amounts of potassium may be lost in the watery stool, with little food or drink being taken to replace it. A similar situation may arise in people who abuse laxatives to lose weight. But in studies that followed people taking senna for over 1 year, there was no disturbance in the levels of potassium or of other minerals in the blood.

Do laxatives have a role in weight loss?

Laxatives are sometimes taken in doses big enough to cause diarrhoea to ‘help’ with weight loss – presumably in the belief that diarrhoea will prevent food that has been eaten from being absorbed. But this belief is entirely false. Laxatives predominantly affect the large bowel, whereas nutrients are absorbed in the small bowel. All that enters the large bowel is water and waste. The weight loss brought about by laxative-induced diarrhoea is due to dehydration. There is no loss of fat.



I’ve suffered from diarrhoea for a long time. Some days, I would just gush out a small piece of stool followed by lots of water. This could happen several times a day. Oddly, on other days, I wouldn’t need to go at all. Eventually, I was seen at a hospital clinic. They said I was constipated and told me to take laxatives! How can this be?

This is called overflow constipation. It is regularly seen, even in fit and active young people. The image below is an X-ray of an active, 42-year-old man who was suffering from intermittent diarrhoea and bloating. The arrows are pointing to his colon, which is full of stool all the way round; it looks like fluffy shadows. If the bowel were not full of stool, it would be outlined only by the air within it, which looks black on the X-ray.

Irritable Bowel Syndrome x-ray

Irritable Bowel Syndrome x-ray


There is not necessarily anything wrong with this situation – after all, it’s the function of the colon to hold stool, and there’s no problem if the bowel and its owner are comfortable. But when the colon holds more stool than it’s happy with, it may try to excrete the stool by secreting more water and mucus. If the stool is hard and impacted (gets stuck) within the bowel, the water may bypass the stool and come out as just a very watery stool with perhaps some pieces of solid stool within it. So the person thinks that he or she has diarrhoea.

The doctor may find several clues to the right diagnosis. First, the diarrhoea is intermittent, with days of no bowel activity at all, and the abdomen may appear full or distended. If a rectal examination is performed, there may be hard stool within the rectum. The diagnosis can be confirmed by a simple abdominal X-ray. Without the X-ray, it can be very difficult to explain to a young man complaining of diarrhoea that he is actually constipated!

When this gentleman had his X-ray explained to him, he was able to understand his symptoms of frequent bowel motions and spasms, as the bowel tried to empty itself. The treatment he was offered also made sense to him. I would like to say that I always spot this diagnosis straight away, but in fact I believe I more often make it in retrospect.

I have always had an irregular bowel habit – sometimes constipated, sometimes loose. More recently, my bowel habit’s changed and I went to see my doctor about constant diarrhoea. Eventually, I had a colonoscopy. They told me that my bowel was completely normal. I received no treatment, but for the first week or two after the colonoscopy my bowel habit was better than it had ever been. Now it’s all starting up again – sometimes constipation, sometimes diarrhoea. What can I do?

There are a number of possible explanations for why you felt so much better after the colonoscopy. First, the reassurance of knowing that there is nothing seriously amiss can greatly help symptoms. This is true even in people who are not overtly anxious. More intriguing is the possibility that your symptoms are due to overflow constipation, so that the periods of diarrhoea represent an attempt by your bowel to clear itself. The day before the colonoscopy, you would have taken large doses of powerful laxatives to clear your bowel of stool. This is usually the worst part of the procedure, but in your case, by clearing the constipation, it might have been therapeutic! You can test this hypothesis by taking laxatives. You will not need to be as drastic with the laxatives as you were before the colonoscopy, and standard doses of senna or bisacodyl for a few days may do.



I’m 23 and I get pain low down on the left side of my abdomen. It’s a cramping pain that comes and goes, and I get it several times a week. If I can get my bowels open really well, it gets much better, but I usually pass small hard stools with a lot of effort. Am I constipated, or is this something more serious?

It sounds very much like constipation. The bowel in the left lower corner of the abdomen where you get your pain is called the sigmoid colon. Its function is to hold the stool until you are ready to expel it. The pain you describe is a spasmodic contraction of the sigmoid colon as it tries to expel the hard stool.

The usual advice is to drink plenty of water, eat more fibre and take more exercise. This will work in many cases, but it may take time and may initially make you a little worse as well as bloated. Another strategy is to take a stimulant laxative like senna or bisacodyl before bed and you will probably open your bowel well in the morning. You may need to do this for several days to get it clear enough, passing soft stools and feeling that your bowel has emptied. It may then be possible to avoid any more constipation by eating a little more fibre and taking more exercise. However, there is nothing wrong with using stimulant laxatives every so often.

I tried using senna but it gave me the same spasm-like pain in the lower left corner of my abdomen that was bothering me in the first place!

Cramping pains or spasms are a side effect of stimulant laxatives. You can think of it in terms of the laxative stimulating your bowel to contract around the hard stool. Once the stool has cleared, the pain will go.

You may prefer to try non-stimulant laxatives. A popular mild laxative is lactulose. This is a non-digestible sugar that softens the stool by drawing water into the bowel. Bacteria in the bowel are able to metabolise lactulose, producing gas, so bloating and wind are the main side effects. It is also sometimes not sufficiently strong enough. The laxatives based on polyethylene glycol (see a previous question) are also non-stimulating and are more effective, but they tend to be more expensive. They are available without prescription as Movicol or Idrolax. Older remedies, still popular, are magnesium salts such as Cream of Magnesia (magnesium hydroxide), Epsom salts (magnesium sulphate) and Andrews Liver Salts (magnesium sulphate, sodium bicarbonate and citric acid).

Does it do any harm to combine different kinds of laxative?

No, not at all. In fact, combinations may well work better. Fibre may be combined with a stimulant laxative; for example, Manevac is a combination of the fibre Ispaghula and the stimulant laxative senna. Stimulant laxatives often combine well with osmotic laxatives such as lactulose, polyethylene glycol or magnesium. It’s worth trying different combinations to find what works for you.

I get a lot of pain in my abdomen. It’s mostly low down on the right, but sometimes it’s on the left, and sometimes the whole of the lower part of my abdomen aches with a kind of heavy, dragging feeling. I also get a lot of bloating, and sometimes I feel sick. My bowel habit has always been irregular, usually with small, pellet-like stools. I’ve had these symptoms for many years, and my GP has put them down to irritable bowel syndrome. Recently I’ve noticed that if I open my bowels really well, the pain tends to ease. Could I be constipated?

The symptoms you describe are typical of irritable bowel syndrome, and a third of people with irritable bowel syndrome are also constipated (denoted as ‘IBS-C’). If people open their bowels infrequently and produce hard stools, then yes, they are clearly constipated. Occasionally, however, people will pass stool on most days without actually clearing their bowel well enough. The bowel in irritable bowel syndrome is more sensitive to being distended, be this with gas, liquid or solid stool, and pain that is improved by defecation is actually a part of the definition of irritable bowel syndrome. It follows that some individuals with irritable bowel syndrome will feel better if their bowels are emptied more thoroughly, especially if they are constipated.

By examining your abdomen, a doctor can sometimes tell if your bowel is full. Occasionally, I arrange an abdominal X-ray to see just how full a person’s bowel really is. But it’s often easier just to try some laxatives. Most people with your symptoms will also have been advised to increase the fibre content of their diet.

I did try sachets of Fybogel (Ispaghula husk). When I used two sachets a day, my stools did become softer and more formed, in larger pieces. I was going more regularly and I had less pain. It was the bloating I couldn’t stand. I was promised that it would go, but it persisted and it’s much worse with any other fibre preparation that I’ve tried. What can I do?

Unfortunately, bloating and wind are the consequence of taking more fibre. Sometimes it settles with time, but sometimes it doesn’t. One solution is to use smaller quantities of fibre together with a laxative. Stimulant laxatives are simple to take but can cause spasm. Osmotic laxatives, especially polyethylene glycol, may be as effective without spasm. It is worth experimenting. There is a balance to be struck: more fibre will give better stools but more bloating; less fibre gives less wind, but the constipation may be worse. Trying fibre in combination with laxatives, either regularly or intermittently, may be more suitable.

I’ve had an irritable bowel for many years. The worst problem for me is the cramping, spasmy pain in my lower abdomen. I’ve tried all the antispasmodics available at the chemist and several that my doctor prescribed, but the only thing that helps is codeine. My problem with codeine, though, is that it constipates me. My stools become hard, I have to strain, and I generally feel even more bloated. My doctor suggested senna, but it just gives me more spasms. What do you suggest?

Codeine is an opioid-based analgesic (painkiller) but does cause a considerable slowing of the bowel. I would begin by making sure that the whole problem isn’t just constipation that you are exacerbating with the codeine. Try to get a really good clear out with a laxative. That means taking enough laxative to pass a lot more stool than usual and making your stool much looser for a few days. Avoid taking codeine for those few days and see if you can weather the spasms over that time, or just take the antispasmodics. Try and use polyethylene glycol-based laxatives or other osmotic laxatives because stimulant laxatives such as senna can cause spasms and may continue to do so for 12 hours or more.

If you are much better after the clear out, or if your spasms are less severe and can be controlled by simple antispasmodics like peppermint oil, it’s fine to repeat the laxative treatment whenever you need it.

But if your spasms persist despite clearing any constipation, the problem is how to continue using codeine without getting constipated. Taking more fibre in your diet will probably work, but you may find you have more bloating and wind. It might be better to introduce the extra fibre slowly, perhaps taking less than 5 g (about one sachet of fibre supplement or two fruits) each day in addition to your normal diet in the first week, and increasing the dose in the following weeks if necessary. Alternatively, small doses of an osmotic laxative taken routinely will keep the stool soft.

I eat a high-fibre diet with plenty of fluid, I exercise regularly, and I’m not taking any medication. But I’m always constipated. What am I doing wrong?

You’re not doing anything wrong; life is just like that. I suggest that you take some laxatives and congratulate yourself on not having anything more serious and on looking after yourself well.



There are and always have been myths around constipation. Most doctors will now agree that a regular bowel habit is not essential for health and that a constipated bowel does not poison the body. But constipation is still a common problem both on its own and as part of irritable bowel syndrome. Whichever is the case, relieving the constipation will usually help with bloating and pain as well as making defecation easier and more comfortable.

Most doctors and other healthcare professionals advise extra fibre and fluids as the first treatment for constipation. Contrary to the evidence that is available, many professionals advise against laxatives except as a last resort. Consequently, many people suffer for years before being given ‘permission’ by a doctor to use the simple treatments readily available at the chemist. If you suspect that constipation is part of your problem, it is worth trying some of the treatments described above. They are mostly available without prescription and are safe. Some people just try a fibre preparation and give up if it doesn’t work or produces too much bloating. But if one laxative does nothing for you, or causes problems, try another of a different type. Don’t be afraid of using potent stimulating laxatives to clear out your bowel.



A third of people with irritable bowel syndrome will have constipation as their predominant problem.

We are usually unable to determine a specific cause for the constipation.

Constipation is rarely caused by serious bowel disorders.

Some people just have a slow bowel.

Exercise is important. As well as its other benefits, it keeps the bowel going.

Stress usually slows the bowel.

Eating too little fibre may cause or exacerbate constipation.

Although in general people with constipation do not eat less fibre than people with a more usual bowel habit, eating more fibre may help and is the most commonly recommended first treatment.

Fibre often makes the bloating of constipation worse, especially at first.

Laxatives are effective and safe.

The view that laxative use damages the bowel is a myth.