Irritable Bowel Syndrome (IBS): Causes and Treatments
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Published: Mon, 14 May 2018
- Lucy Crawshaw
Irritable Bowel Syndrome – What is IBS and what are the treatments?
The aim of this report is to provide information on Irritable Bowel Syndrome (IBS) and inform those diagnosed with IBS about the treatments available.
IBS is a common condition of the small and large intestine, or ‘bowel’. It affects about 15% of the population and of those affected, about 9% are female and 6% are male. IBS is a functional condition, meaning that it disrupts bowel function but does not cause detectable abnormalities in the structure of bowel. This can lead to doctors and the public trivialising the condition, even though it affects patients’ quality of life by causing pain, problems associated with passing faeces and psychological issues such as depression.
The Digestive System
The body’s cells require many different molecules and ions to function; it is the digestive system (shown in Figure 1) which supplies these nutrients. The term ‘digestion’ encompasses ingestion, digestion (the breakdown of food into its component nutrients), absorption of nutrients and excretion of waste products.
During ingestion, food is placed into the mouth, chewed and mixed with saliva to form a soft mass, or bolus. Saliva contains enzymes which catalyse, or speed up, the breakdown of food. After the bolus is swallowed, it travels down the oesophagus into the stomach, aided by peristalsis (muscular contractions which travel down the particular organ).
In the stomach, gastric juices including hydrochloric acid and enzymes break down the bolus into a liquid called chyme. The chyme enters the small intestine along with pancreatic juices containing enzymes, and bile (which is produced by the liver and
stored in the gall bladder), where it is fully digested. The nutrients released are absorbed through blood vessels in the small intestine. Peristalsis pushes the undigested matter, including fibre, resistant starch and bacteria into the large intestine (which is divided into the cecum, colon and rectum). Once in the colon, water is absorbed, turning the matter into faeces. The faeces moves into the rectum by peristalsis, after which it is excreted from the anus.
What are the symptoms?
The severity of IBS symptoms vary but are usually worse in the morning and after eating. Typical symptoms include painful abdominal cramps, which ease after passing faeces, abdominal bloating, flatulence, changes in the consistency of faeces (ranging from diarrhoea to constipation) and passing mucus with faeces. Sufferers may also feel the sudden need to empty their bowels or feel that their bowels are not empty despite having been to the toilet. Other symptoms can include feeling sick, back ache, lethargy, bladder problems including the urgent need to urinate, difficulty emptying the bladder and incontinence and dyspareunia, or pain during sex.
IBS is unpredictable in that sufferers may experience no symptoms for months, then experience a ‘flare-up’ for no discernible reason. Symptoms may settle within 2 to 3 days or can take months to settle.
IBS has also been linked with psychological problems such as depression and anxiety. It has been estimated that 3 in 4 sufferers will develop depression and about 50% will develop Generalised Anxiety Disorder (GAD).
What are the causes?
The exact cause of IBS is unknown although several theories have been proposed. Some experts believe that IBS is caused by a change in the speed at which chyme is processed through the bowel; slower processing allows the colon more time to absorb water, causing constipation by making faeces harder and more difficult to excrete. If processed more quickly, less water is absorbed, resulting in diarrhoea. A second theory is that IBS is caused by disruption to nerve signals between brain and bowel, increasing sensitivity to pain, so that mild indigestion to a non-sufferer may cause severe pain to IBS sufferer.
Both of these changes may be linked to food poisoning or intolerance to certain foods. Another theory suggests that these changes may be caused by stress, anxiety or trauma during childhood (such as abuse or neglect), which decreases the level of the neurotransmitter serotonin in the body. Serotonin is produced by the brain and intestines, and is important in controlling mood and digestion. Reduced serotonin levels have been linked to depression and slow peristalsis in the bowel, leading to constipation. Higher levels of serotonin in the body can increase peristalsis, causing diarrhoea; this theory may help to explain the link between IBS and depression.
IBS may also be related to Small Intestinal Bacterial Overgrowth (SIBO), where bacteria from the large intestine migrates to the small intestine and ferment the indigestible components of chyme, and giving off hydrogen, carbon dioxide and methane gas.
How is IBS diagnosed?
As IBS causes no physical changes to the bowel, doctors must rely on patients describing their symptoms. A diagnosis can be made if the patient has been suffering from the typical symptoms for the previous 6 months. However, doctors may wish to carry out tests including blood tests and faeces tests, to rule out other conditions which cause similar symptoms, like inflammatory bowel disease, 1eliac disease or infections.
What are the treatments?
As yet, no cure has been found for IBS, however symptoms can be managed.
One of the easiest treatments is modification of the diet. Dietary advice is best provided by healthcare professionals on an individual basis, based on the patient’s symptoms and reactions to certain foods. Recording a food diary detailing what is eaten and any ill-effects is an effective way of identifying the changes which are needed. Seeking dietary advice may also benefit other aspects of patient health, including ensuring a balanced diet, and weight management.
Fibre, from components of plants like cellulose, lignin and pectin which are resistant to digestive enzymes, is an important factor in the diet. Soluble fibre dissolves in water, causing it to swell and form a gel, softening faeces and stimulating peristalsis. It is though that increasing soluble fibre and water in the diet can ease the symptoms of IBS. In contrast, insoluble fibre acts as an irritant to IBS sufferers as it remains intact during digestion, increasing the speed at which faeces travels through the bowel.
Soluble fibre is found in foods like rice, pasta, oats, root vegetables and fruits including bananas and mangoes. Generally, foods which are stringy, have tough skin or contain seeds are high in insoluble fibre. Specific examples include cereals, wholegrain foods, nuts and seeds, salad and dried fruit. Insoluble fibre should not be completely excluded from the diet but should be consumed in small quantities alongside soluble fibre. Cooking, chopping and pureeing foods containing insoluble fibre may help to reduce their ill-effects.
To reduce flatulence, a low FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) diet is recommended. FODMAPs are carbohydrates which are resistant to digestion and as a result, ferment in the bowel. Foods containing FODMAPs include processed wheat products, dairy products containing the sugar lactose, beans and some fruit and green vegetables, including peaches, nectarines, apples, cherries, cabbage, broccoli and peas.
Other ‘trigger foods’ that should be avoided include red meat, dark poultry meat and skin, saturated fats (such as butter and lard), sulphur-rich foods including onions and garlic, acidic foods like vinegar and citrus fruits, fructose (fruit sugar) and artificial sweeteners.
IBS sufferers are advised to eat regularly, avoid skipping meals and take their time whilst eating. Drinking about 2 litres of non-caffeinated, non-alcoholic liquid per day is also recommended.
It is though that probiotic products like yoghurts and capsules may ease IBS symptoms in some patients. It is currently recommended that patients should use a product for 4 weeks before deciding whether it is beneficial. Other suggested ‘off-the-shelf’ products include remedies containing herbs like peppermint, fennel and acacia.
Another effective way to manage IBS, whilst also benefiting other aspects of a patient’s health, like weight management and fitness, is to conduct about 150 minutes of moderate-intensity exercise per week (like cycling and walking). Exercise reduces stress by increasing serotonin levels and also pumps blood away from the bowel and towards other muscles, which may help to ease IBS symptoms both during exercise and in the long-term.
Stress can also be reduced with relaxation techniques such as breathing exercises and meditation and activities like yoga. Other methods to reduce stress or treat IBS-linked depression are counselling, hypnotherapy and Cognitive behavioural therapy (CBT), which teaches people to alter their thinking and behaviour.
Alternative treatments like acupuncture and reflexology are not recommended.
When other treatments fail, doctors may recommend medication. While medication can ease the symptoms of IBS, it may also pose a risk to health due to possible side effects.
Antispasmodics such as Mebeverine are prescribed to relax the bowel muscles thus reducing painful abdominal cramps. For patients with constipation, bulk-forming laxatives, like Normacol or Fybogel, can make bowel movements easier and more regular, due to the insoluble fibre contained within these drugs. In contrast, antimotility medicines such as Loperamine slow peristalsis allowing faeces time to solidify in the bowel, thus easing symptoms for patients with diarrhoea.
Finally, irrespective of whether a patient is displaying psychological symptoms of IBS, antidepressants may be prescribed. Tri-Cyclic Antidepressants (TCAs), like Amitriptyline, interact with neurotransmitters (including serotonin) in the brain where they reduce anxiety and pain, and in the intestines where they slow peristalsis, making them effective for treating patients with diarrhoea. Selective Serotonin Reuptake Inhibitors (SSRIs), like Citalopram, increase serotonin levels in the body, proving them beneficial to patients with constipation.
Is treatment effective?
A study entitled ‘Effects of a health program comprising reassurance, diet management, probiotics administration and regular exercise on symptoms and quality of life in patients with irritable bowel syndrome’ found that such treatment significantly eased the symptoms of 143 IBS patients who suffered from pain, diarrhoea-dominant IBS or constipation-dominant IBS (as shown in Figure 2). However, this study does not show the individual effect of each treatment.
With regards to probiotics, the NHS argues that little evidence supports their use, however studies such as those cited by probiotic manufacturer OptiBac suggest that their products can be highly efficacious. There is also little evidence to support the use of herbal remedies.
A review of previous studies entitled ‘Efficacy of antidepressants and psychological therapies in irritable bowel syndrome: systematic review and meta-analysis’ found that antidepressants were 34% more effective than placebo drugs in reducing the symptoms of IBS, while psychological therapies reduced symptoms in 33% of patients. The conclusion stated that both treatments are ‘effective’.
What are the implications treatment?
The ease of availability of information about self-help treatments, (especially on the internet) could be considered unethical as patients may fail to seek professional medical help. The implication is that patients may receive inadequate treatment for their IBS or that other causes of their symptoms may not be diagnosed, which could prove fatal.
The lack of conclusive evidence supporting the use of herbs and probiotics as self-help treatments raises questions as to the ethics of manufacturers promoting such products as they may give rise to ‘false hope’ of a cure.
There are also questions as to the ethics of prescribing medication for a ‘functional’ condition. In addition, social stereotyping could lead to patients prescribed antidepressants being labelled as ‘crazy’ etcetera.
Finally, the treatment of IBS has a significant economic impact on the UK; the National Institute of Health And Care Excellence (NICE) estimate that diagnosis and management of IBS cost the NHS £7,879000 in 2008.
Evaluation of reference materials
Websites like ‘NHS Choices’ and ‘Patient’ provide a useful overview on IBS and cover a wide range of topics, however fail to fully explore many areas including how the different types of fibre affect IBS, why exercise is beneficial to sufferers and how certain drug treatments work.
Despite the ethical issues related to selling untested remedies, of all the references cited, ‘Help for IBS’ provides the most practical advice on changing dietary fibre intake, including food preparation tips. In contrast, other websites like ‘NHS Choices’ purely state that changes should be made. ‘Help for IBS’ also includes information on other ‘trigger foods’, which was not available in the other resources.
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