Nutritional care of the patient with constipation

Best Practice & Research Clinical Gastroenterology Vol. 20, No. 3, pp. 575–587, 2006 doi:10.1016/j.bpg.2005.11.002 available online at http://www.sciencedirect.com

9 Nutritional care of the patient with constipation Fernando Ferna´ndez-Ban˜ares* MD Department of Gastroenterology, Hospital Universitari Mutua Terrassa, Plaza Dr Robert 5, 08221 Terrassa, Barcelona, Spain Chronic constipation is defined as a symptom-based disorder based on the presence for at least 3 months in the last year of unsatisfactory defecation characterized by infrequent stools, difficult stool passage, or both. On the other hand, the presence of clinically important abdominal discomfort or pain associated with constipation defines irritable bowel syndrome (IBS) with constipation. Intake of dietary fibre and bulking agents (psyllium) may be effective in alleviating chronic constipation in patients without slow colonic transit or disordered constipation. On the other hand, fibre may improve stool consistency in patients with IBS with constipation, but it is considered to be not effective in improving abdominal pain, distension or bloating. Probiotics may be effective in relieving constipation; however, the effect of lactic acid bacteria ingestion may be dependent on the bacterial strain used and the population being studied. Lactulose, which is a substrate for lactic acid bacteria (prebiotic), is effective to treat patients with chronic constipation. Key words: chronic constipation; irritable bowel syndrome; dietary fibre; bulking agents; probiotics; prebiotics.

DEFINITION Recently the American College of Gastroenterology Chronic Constipation Task Force defined chronic constipation as a symptom-based disorder based on the presence for at least 3 months in the last year of ‘unsatisfactory defecation characterized by infrequent stools, difficult stool passage, or both. Difficult stool passage includes straining, a sense of difficulty passing stool, incomplete evacuation, hard/lumpy stools, prolonged time to stool, or need for manual manoeuvres to pass stool”.1 Previously, a consensus definition was proposed by a group of experts to define this heterogeneous clinical condition (Rome II) in 1998.2 The symptom-based so-called

* Corresponding author. Tel.: C34 3 7365050; fax: C34 3 7365043. E-mail address: [email protected]

1521-6918/$ - see front matter Q 2005 Elsevier Ltd. All rights reserved.

576 F. Ferna´ndez-Ban˜ares

‘Rome criteria’ include 12 weeks or more of symptoms in the preceding 12 months, including hard or lumpy stools, straining, a sense of incomplete evacuation, the need to use manual manoeuvres to pass stool, or a sense of anorectal obstruction with R25% of bowel movements, and/or !3 bowel movements/week, with no evidence of organic disease. At least two symptoms should be present to make the diagnosis of chronic functional constipation. This definition allows identifying uniform groups of patients for inclusion in randomised controlled trials. However, its use is impractical in clinical practice and most patients who refer for constipation do not fulfil the criteria. In this sense, the constipation task force members recommended a broader definition that encompasses the symptoms most commonly expressed by patients who self-report constipation. On the other hand, symptom-based criteria for chronic constipation and irritable bowel syndrome (IBS) with constipation might overlap. IBS is characterized by abdominal discomfort or pain, bloating, and disturbed defecation. The disturbed defecation can take the form of constipation, diarrhoea, or mixed/alternating bowel habits. Task force members emphasized that the presence of clinically important abdominal discomfort or pain associated with constipation defines IBS with constipation. Most patients with chronic constipation report minimal abdominal bloating or discomfort. Thus, in some patients it may be difficult, if not impossible, to differentiate chronic constipation and IBS accurately.

PATHOPHYSIOLOGY OF CHRONIC CONSTIPATION Primary or idiopathic constipation can be broadly divided into three subtypes, including slow transit constipation (i.e. colonic inertia), outlet delay constipation (i.e. obstructive defecation, pelvic floor dyssnergia, pelvic floor dysfunction, defecatory dysfunction, anismus), and functional constipation. Physiologic abnormalities in patients with slow transit defecation include abnormal postprandial colonic motor function, autonomic dysfunction, and reduced numbers of enterochromaffin cells and interstitial cells of Cajal.3–5 Outlet delay constipation can occur as a consequence of the inability to coordinate actions of the abdominal musculature, anorectum, and pelvic floor musculature.6 This prevents straightening of the anorectal angle, which should precede the normal passage of stool. The third subtype is comprised of patients with complaints of constipation but with normal transit and normal pelvic floor function.7 However, there is a significant overlap between these subtypes, and p.e., many patients with dyssynergic defecation may also have prolonged colonic transit. Secondary causes of chronic constipation are listed in Table 1. In this sense, in some patients a careful history and physical examination can provide clues as to the etiology of constipation.

MANAGEMENT OF CHRONIC CONSTIPATION Lifestyle measures The need to set aside a regular time for defecation and respond to a defecatory urge should be stressed.

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Table 1. Secondary causes of chronic constipation. Medications Opiates Anticholinergics Antidepressants Anticonvulsants Dopaminergics Calcium channel blockers Bile acid binders Supplements (calcium and iron) Endocrine/metabolic disorders Diabetes mellitus Hypothyroidism Hypercalcemia Pheochromocytoma Porphyria Neurologic disorders Systemic Parkinson disease Multiple sclerosis Autonomic neuropathy Autonomic failure Traumatic Spinal cord lesions Gastrointestinal disorders Aganglionosis (Hirschprung’s disease, Chagas’ disease) Myopathy Neuropathy Megarectum/megacolon

It has been claimed that a sedentary life style may contribute to constipation. Several population studies support the idea than those who are more active and perform more physical activity have a lesser incidence of constipation.8 Physical activity affects colonic motor function, with changes in function probably proportional to the extent of activity. Prolonged physical inactivity in those who are normally physically active, especially in the elderly, can reduce colonic transit, favouring constipation. However, other factors such as cognitive function, presence of depressive symptoms, use of medications that slow bowel motility, an inadequate diet, are likely to play a role in the elderly constipation. In healthy subjects, only vigorous physical activity such as running a marathon increases gut and colonic activity and can lead to dramatic increases in large bowel function.9 Modest physical activity may help subjects with mild constipation, but there is no evidence that it may improve severe constipation.10 Increasing fluid intake does not have an important effect on colonic function, and it is not recommended to treat constipation unless there is evidence of dehydration.8 In this sense, children or adults with fever, or subjects in hot environments, should be advised to consume sufficient fluid.

578 F. Ferna´ndez-Ban˜ares

Fibre-enriched diet In 2001, a National Academy of Sciences expert panel was appointed to define fibre.11 ‘Dietary fibre’ was defined as nondigestible carbohydrates and lignin that are intrinsic and intact in plants. Foods high in dietary fibre include whole grains, legumes, vegetables and fruits. Another class of fibre, ‘functional fibre’ was defined as nondigestible carbohydrates extracted from foods that have beneficial physiological effects in humans. ‘Total fibre’ was then defined as the sum of dietary fibre and functional fibre. Dietary fibre, or non-starch polysaccharide, is composed of cellulose, non-cellulose polysaccharide, and lignin. Non-digestible (i.e. resistant) starch and oligosaccharides (e.g. fructo-oligosaccharides -FOS-) cannot be decomposed by human digestive enzymes in the upper alimentary tract, and thus have been recently included in a nutritional/physiological definition of dietary fibre, as ‘functional fibre’.11 It is important to know that fibre is neither a single substance nor an inert, indigestible, unavailable material that simply passes through the gut. Non-absorbed carbohydrates entering the colon suffer digestion by colonic anaerobic bacterial flora that produce polysaccharidases and other enzymes. Because this digestion occurs anaerobically it is known as fermentation, which is a process characterised by a complex series of inter-related reactions resulting in the formation of a variety of end-products including short-chain fatty acids (acetate, propionate, and butyrate), gases (hydrogen, methane, carbon dioxide), as well as energy, which bacteria use for growth and maintenance.12 It has been estimated that about 70 g carbohydrate/ day is required to maintain the colonic flora. Virtually all fibres are broken down to a greater or lesser extent in the colon. The extent of fermentation and the range and nature of the end-products depends on a number of factors, including among others type of fibre, physical nature of the fibre (e.g. particle size), solubility, and surface area. Different types of fibre have different effects on stool weight.13 The cellulosic fraction of some cereal fibres has the most effect on increasing the stool weight and decreasing transit time, since it tends to survive digestion better than non-cellulosic polysaccharides (10% of cabbage fibre is recovered in faeces, compared with 60% of wheat bran). Soluble fibres such as pectin or guar, different forms of resistant starch, and fructans such as inulin or FOS are the less effective in increasing the stool weight, and some of them are not detected in faeces after consumption, indicating that they are completely fermented in the colon. Dietary fibre may be classified according to their solubility, as summarised in Table 2. Increased fibre particle size results in increased stool output. Large particles are more slowly degraded, whereas reducing the particle size increases the available surface area, resulting in increasing digestibility, so that the cellulose content of finely ground bran is digested faster than that in coarse bran.14 Furthermore, it has been shown that the particles themselves may stimulate colon motility.15 A diet poor in fibre should not be assumed to be the cause of constipation but could be a contributing factor. There is not doubt that intake of dietary fibre, mainly insoluble fibre, increases stool bulk and frequency, and decreases consistency in healthy people (Grade A recommendation). A careful meta-analysis showed that in 18 of 20 studies stool weight was increased by adequate fibre supplementation, and there was increased faecal transit.16 In this sense an inadequate diet with a diminished intake of dietary fibre may contribute to constipation in an important subgroup of patients. These patients may be considered to suffer from a ‘relative fibre deficiency’, as they have not identifiable cause of their complaints. However, there is a subgroup with more severe

Nutrition and constipation 579

Table 2. Categorisation of dietary fibre according to solubility. Type of fibre

Examples

Insoluble fibre

Insoluble polysaccharides Cellulose Hemicelluloses Soluble polysaccharides Pectins Beta-glucans Plant exudates gums Mucilages Legume seed gums Seaweed polysaccharides Bacterial polysaccharides Fructo-polysaccharides (inulin) Fructo-oligosaccharides (oligofructose) Resistant starch

Soluble fibre

constipation secondary to slow transit constipation and/or disordered defecation who get worse with an increase in dietary fibre intake.8 Despite that, all constipated subjects should be advised as an initial measure to increase their dietary fibre intake as the simplest, most physiologic, and cheapest form of treatment.17 In those people in whom fibre aggravates their sense of abdominal distension or in whom fibre lead to incontinence (mainly in elderly subjects), a reduction in their fibre intake should be recommended. On the other hand, gas production from fibre metabolism may limit acceptance. This is particularly true from extensively fermented fibres (usually the soluble types), which lead to increased bulk in colon by increasing microbial mass. Less well fermented fibres (usually the insoluble types) produce less gas and contribute to increasing bulk in the colon by their water-holding properties. Water-holding appears to be related to solubility and thus to rate of fermentation by colonic microflora; rapidly degraded fibres have a less pronounced effect of stool weight than less well degraded fibres. Increased bulk in the colon decreases transit time, which in turn results in decreased water reabsorption, and as a consequence wetter stools and thus increased stool weight.13 It follows from these discussions, therefore, that the optimum way of improving colonic function in most constipated patients is to prescribe a diet whose fibre content is higher than that ingested previously. The amount of fibre that is necessary to correct constipation varies in different people, but the effect of fibre on stool weight is dose dependent. Whereas some subjects may require 10 g per 1000 cal, others may require 20 g per 1000 cal.18 Cummings reviewed over 100 studies of the effect of fibre intake on stool weight and calculated the increase in weight of the stool as a function of fibre intake.19 There was a wide range of the contribution of dietary fibre to fecal weight (p.e, an increase of 5.7 g fecal bulk per gram of wheat bran fed compared to an increase of 1.3 g per gram of pectin in the diet). The 2005 Dietary Guidelines of the Institute of Medicine (IOM) (USA) support a daily fibre intake of 14 g per 1000 kcal to reduce the risk of cardiovascular disease and promote healthful laxation (for a critical daily stool weight of 160–200 g).20 In general, patients with chronic constipation require greater doses of fibre than do healthy subjects in order to produce similar increases in stool

580 F. Ferna´ndez-Ban˜ares

Table 3. Soluble and insoluble fibre contents of some common foods and supplements.18,21,22 Foods

Grams/100 g dry wt

Percentage insoluble fibre (%)

Wheat bran Oat bran Rye bran Corn bran Bran flakes All-Bran Corn flakes Rice Krispies (Kellog’s) Special K (Kellog’s) Cabbage, cooked Cauliflower, cooked Broccoli, cooked Pinto beans Kidney beans Lentils Apple (with skin) Guar gum Psyllium seeds (Ispaghula husk)

35 17 39 55 19.5 30.1 1.6 1.9 2.7 1.5 1.4 2.0 14.2 13.8 7 2.8 95 70–90

90 50 90 90 90 90 70 90 100 60 60 60 75 75 90 60 0 10

Most vegetables are approximately 30–40% soluble and 60–70% insoluble. Most legumes average from 10 to 25% soluble and 75–90% insoluble. Fruits vary from 30 to 65% soluble and 35–70% insoluble.

weight.16 In starting a fibre-enriched diet, the increasing levels of fibre should be introduced slowly to tolerance, or until the patient becomes satisfied with the results. An appropriately balanced soluble and insoluble fibre intake is likely to be the better option. However, some patients will tolerate insoluble better than solublefibre, and others will tolerate soluble better than insoluble. Thus, results can be obtained with one or the other, and this will vary from patient to patient.18 Specific dietary advice is often needed to achieve a satisfactory increase in dietary fibre. An extensive list of the content of dietary fibre in the common foods and breakfast cereals can be obtained from the literature.18,21,22 Table 3 lists soluble and insoluble fibre contents of some common foods and supplements. The most important sources of fructans (inulin and FOS) include garlic, Jerusalem artichoke, chicory, leeks, onion, wheat, asparagus, and artichokes. Resistant starch could be found in raw potato, banana, cooked cooled potato, bread, cornflakes, and partly milled grain and seeds. An overview of the typical intakes of the different fibre components in the Western diet is given in Table 4. Fibre supplements (bulking agents) When symptoms of chronic constipation are sufficiently bothersome to impair the patient’s quality of life, treatment is warranted.1 Dietary fibre supplementation can be achieved by increasing the ingestion of fibre-rich foods (as above described), or by providing commercially available fibre supplements. Bulk agents are a concentrated form of non-starch polysaccharides useful for patients who cannot take adequate dietary fibre. Available bulking agents include psyllium (Ispaghula husk), wheat bran, calcium polycarbophil, methylcellulose, guar gum, and sterculia (Indian tragacanth or

Nutrition and constipation 581

Table 4. Estimated mean typical daily intake of the different components of dietary fibre in healthy adults consuming a Western diet (adapted from Green23). Components of dietary fibre

Grams/day

Total NSP

11.8–15.7 (aprox. 40% from cereals, 50% from vegetables, and 10% from fruit) 6.5–7.0 (cellulose, 3.2; non-cellulose, 3.3–3.8) 5.3–8.7 2–12 1.5–15 1

Insoluble NSP Soluble NSP Inulin and FOS Resistant starch Lignin

NSP, Non-starch polysaccharides; FOS, Fructo-oligosaccharides.

karaya). There are three placebo-controlled trials of the use of psyllium in patients with chronic constipation24–26 (Table 5). These have been recently reviewed.27 They demonstrated improvements in stool frequency and consistency at doses between 10 and 24 g/day. However, only one of these was of high quality,26 and it was the only one lasting more than 4 wk, but only included 22 patients. Nonetheless, it appears that psyllium improves stool frequency and consistency (Grade B recommendation).27 There were no statistically significant differences in side effects between psyllium and placebo. In an observational study, 149 patients were treated with psyllium in the form of Plantago ovata seeds, 15–30 g daily, for a period of at least 6 weeks. There was an improvement of 85% in patients without a pathologic finding, whereas there was a poor response to treatment among patients diagnosed from slow colonic transit or a disordered defecation.28 These results emphasize that patients with functional constipation are easily treatable by modification of fibre intake. Of note, despite the popularity of bran as a treatment of constipation, there are no randomised trials that have shown improvements in stool frequency or consistency in patients with chronic constipation.27 Specifically, there is only one placebo-controlled study on the effect of wheat bran in chronic constipation, showing no differences between therapy groups in the improvement of stool frequency or consistency.29 On the other hand, there are no placebo-controlled trials examining the effect of the other bulking agents above mentioned. Small trials comparing some of these agents versus psyllium have failed to demonstrate differences in stool frequency or consistency.27 Overall, studies of bulking agents were of sub-optimal design including very small sample sizes, short duration, or both. They were performed before the advent of what are now generally accepted criteria for treatment trials in patients with functional disorders. Issues pertaining to palatability, and dose-dependent side effects (distension, bloating, flatulence) limit compliance with fibre supplements. Although severe adverse events with bulking agents are rare, oesophageal and colonic obstruction and anaphylactic reactions (psyllium) have been reported.30 In conclusion, it may be considered that bulking agents may be effective in alleviating chronic constipation in patients without slow colonic transit or outlet delayconstipation. If the patient is compliant, fibre treatment may help up to 80%. However, the same results could be obtained by dietary means encouraging patients to eat either a supplement of natural bran or a fibre-enriched diet.

Trial

Study type

N

Treatment

Dose

Duration

P

Cheskin Fenn25 Ashraf26

Crossover Parallel Parallel

10 183 22

Psyllium Psyllium Psyllium

24 g/d 3.6 g t.i.d 5 g b.i.d.

NS p!0.05 p!0.05

Badiali29

Crossover

24

Wheat Bran

6.6 g t.i.d.

Bass42

Parallel

24

Lactulose

60 mL/d

Sanders43

Parallel

47

Lactulose

30 mL/d

Wesselius-De Casparis44

Parallel

103

Lactulose

15–30 mL/d

Mollenbrink39

Crossover

70

E. coli Nissle 1917

Koebnick38

Parallel

70

Banaszkiewicz41

Parallel

84a

Lactobacillus casei Shirota Lactobacillus GG plus lactulose

0.5–5!109 viable cells b.i.d 65 mL/d (6.5!109)

4 weeks each arm 2 weeks 8 weeks after 4 weeks placebo runin 4 weeks each arm after 3 weeks 1 week after 1 week baseline 12 weeks after 2 weeks baseline 3 weeks after 2 weeks baseline 4 week each arm after 1 week 4 weeks 12 weeks

NS

24

a

Constipated children.

109 CFU b.i.d plus 1 mL/kg/d

NS p!0.05 p!0.05 p!0.05 p!0.05 p!0.05

582 F. Ferna´ndez-Ban˜ares

Table 5. Summary of trial characteristics of placebo-controlled trials in chronic constipation.

Nutrition and constipation 583

On the other hand, fibre supplements may improve stool consistency in patients with IBS with constipation (constipation with abdominal pain), but they are not considered to be effective in improving abdominal pain, distension or bloating (Grade A recommendation). In a recent meta-analysis about treatment of IBS,31 the odds ratio in the high-quality studies on the effect of fibre treatment was not significant (OR of global symptom relief, 1.4; 95% CI, 0.99–2; pZ0.06). Another meta-analysis showed a benefit of fibre treatment in the relief of global IBS symptoms (relative risk, 1.33; 95% CI, 1.2– 1.5). However, when IBS symptoms were analysed separately, fibre was shown to be ineffective in the relief of abdominal pain.32 Supplemental bran may even worsen symptoms as abdominal pain or bloating compared to a normal diet.33 Fibre additives in enteral formulas for tube feeding Patients receiving enteral nutrition in the chronic care setting often suffer from constipation, necessitating laxative use. Multiple studies have examined the effects on bowel function of adding fibre to enteral diets compared with fibre-free and selected diets, showing only marginal benefits of questionable clinical significance.34 It is possible that the particle size of fibre incorporated into liquid diets may be too small to retain its expected water holding capacity. On the other hand, most studies employed the use of rapidly degradable fibre, which is completely fermented in the colon, losing the possibility to hold water. Certain fibres, e.g. the cellulosic fraction, tend to survive digestion better than non-cellulosic polysaccharides, and have a more pronounced effect on stool weight than the later. However, it may be impossible to manufacture a formula that is of sufficiently low viscosity to pass through a fine nasogastric tube, and that contains sufficiently large fibre particles to exert the expected effects on bowel function. Probiotics and prebiotics Probiotics are defined as live micro-organisms which when administered in adequate amounts confer a health benefit on the host.35 There is some evidence suggesting that probiotics might relieve constipation. Some studies have shown that milk or yoghurt fermented with different types of probiotics may reduce intestinal transit time and increase the daily stool number in constipated patients. In a double-blind, randomised, crossover design, Bifidobacterium animalis reduced the colonic transit time in a group of healthy women aged 18–45 years.36 Likewise, B. animalis intake led to a significant reduction in oro-cecal gut transit time in a group of elderly subjects free of any gastrointestinal pathology.37 In a double-blind, placebo-controlled study performed in 70 patients with chronic constipation, a probiotic beverage containing Lactobacillus casei Shirota administered for a 4-week period was significantly better than placebo in improving severity of constipation and stool consistency38 (Table 5). Likewise, a preparation containing Escherichia coli Nissle 1917 strain was compared to placebo in a double-blind clinical trial in 70 patients with chronic constipation, showing that the E. coli preparation was significantly better than placebo in increasing stool frequency39 (Table 5). In an open trial in elderly subjects, a commercial mixture of Lactobacillus rhamnosus and Propionibacterium freudenreichii improved defecation frequency in a 24%, but no reduction in laxative use was observed.40 Finally, in a double-blind, placebocontrolled trial, Lactobacillus GG was ineffective as an adjunct to lactulose for the treatment of constipation in children41 (Table 5). Thus, probiotics may be effective in

584 F. Ferna´ndez-Ban˜ares

patients with mild to moderate constipation (Grade B recommendation). However, the effect of lactic acid bacteria ingestion may be dependent on the bacterial strain used and the population being studied. On the other hand, there are no studies evaluating the effect of probiotics as compared to fibre supplements (psyllium). Further controlled and well-designed studies in this type of patients are warranted. Prebiotics such as FOS, galacto-oligosaccharides (GOS), lactulose, and inulin can act as being substrates for lactic acid bacteria, thus encouraging their growth in the intestine (see Chapter 3).The widely used laxative lactulose is not digested by human disaccharidases, and is a substrate for the bifidobacteria in the colonic flora. Three placebo-controlled trial have shown that lactulose (15–30 ml twice a day) is effective at increasing stool frequency and stool consistency in patients with mild to moderate chronic constipation42–44 (Table 5). These have been recently reviewed (Grade A recommendation).27 Other prebiotics would be a promising therapy of chronic constipation.45–47 On the other hand, a small number of studies have evaluated the response of IBS to probiotic preparations.48–52 The results between studies are difficult to compare because of differences in study design, type of IBS evaluated, probiotic dose, and strain. Overall there is, however, some evidence of symptom improvement, mainly in symptoms related to altered handling or perception of intestinal gas (abdominal distension, bloating). This improvement is observed independent of any change in stool frequency or consistency, and cannot therefore be attributed to either a laxative or an antidiarrhoeal effect. In fact, it seems that there is no effect of probiotics on stool frequency and consistency in patients with constipation-predominant IBS.50,52 Discordance between the results of some studies support the concept of specific probiotic strains being more effective than others. Further controlled and welldesigned trials are required to evaluate the effect of probiotics in the different subtypes of IBS, and to assess if they are effective in the treatment of IBS with constipation. A review outlining the safety of current probiotic compounds has been published.53 Cases of infection by Lactobacillus and Bifidobacterium organisms are extremely rare and are estimated to occur at a rate of approximately 0.05–0.4% of all cases of infective endocarditis and bacteraemia.

SUMMARY Chronic constipation is defined as a symptom-based disorder based on the presence for at least 3 months in the last year of unsatisfactory defecation characterized by infrequent stools, difficult stool passage, or both. The presence of clinically important abdominal discomfort or pain associated with constipation defines IBS with constipation. A diet poor in fibre should not be assumed to be the cause of constipation but could be a contributing factor. Intake of dietary fibre, mainly insoluble fibre, increases stool bulk and frequency, and decreases consistency in healthy people (Grade A recommendation). Likewise, bulking agents (psyllium) may be effective in alleviating chronic constipation (Grade B recommendation). However, there is a subgroup of patients with severe constipation secondary to slow transit constipation and/or disordered defecation who get worse with an increase in dietary fibre. On the other hand, fibre may improve stool consistency in patients with IBS with constipation, but it is considered to be not effective in improving abdominal pain, distension or bloating (Grade A recommendation). Probiotics may be effective in relieving chronic

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constipation (Grade B recommendation); however, the effect of lactic acid bacteria ingestion may be dependent on the bacterial strain used and the population being studied. Lactulose, which is a substrate for lactic acid bacteria (prebiotic), is effective to treat patients with chronic constipation (Grade A recommendation). Dose-dependent side effects (distension, bloating, flatulence) limit compliance with both fibre supplements and prebiotics (lactulose). Although severe adverse events with bulking agents are rare, oesophageal and colonic obstruction and anaphylactic reactions (psyllium) have been reported. Cases of infection after supplementation with Lactobacillus and Bifidobacterium organisms are extremely rare.

Practice points † a diet poor in fibre may contribute to constipation in an important subgroup of patients † as an initial measure, increasing the dietary fibre intake is the simplest, most physiologic, and cheapest form of treatment of mild to moderate constipation † there is a subgroup of patients with severe constipation due to slow transit time and/or disordered defecation who get worse with dietary fibre or bulking agents † although fibre may improve stool consistency in patients with IBS with constipation, it is not effective in improving abdominal pain or distension † probiotics may be useful to relieve constipation, but the effect may be dependent on the probiotic dose, bacterial strain used, and the population being studied † a prebiotic such as lactulose is effective at improving stool frequency and consistency in patients with chronic constipation

Research agenda † well-designed controlled trials are necessary to define further the efficacy of bulking agents in patients with functional chronic constipation † well-designed placebo- and fibre-controlled trials are necessary to define the efficacy of the different probiotics and prebiotics in patients with functional chronic constipation † the role of probiotics and prebiotics in the treatment of patients with IBS with constipation has to be defined

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