Chapter 3 Irritable bowel syndrome
constipation-predominant (C-IBS)
AETIOLOGY
Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterised by altered bowel habit and abdominal pain.1 It is a chronic disorder of unclear aetiology.2 Recent research, however, has brought to light a number of possible aetiological factors:
RISK FACTORS
CONVENTIONAL TREATMENT
Many agents are currently used for the treatment of IBS and no one agent has proven particularly effective and/or free from side effects.25–27 Key classes of medications used to treat C-IBS include antispasmodics, antidepressants, laxatives and 5-hydroxytryptamine type 4 receptor agonists (such as tegaserod). Therapeutic gains (the difference in treatment response between placebo and active therapy) have often been minimal with these agents28 and adverse events severe.29
KEY TREATMENT PROTOCOLS
GIT microflora: overview
The microflora of the GIT represents an ecosystem of the highest complexity.30 The microflora is believed to be composed of over 50 genera of bacteria,31 accounting for over 500 different species.32 The adult human GIT is estimated to contain 1014 viable microorganisms, which is 10 times the number of eukaryotic cells found within the entire human body.33 Some researchers have called this microbial population the ‘microbe’ organ – an organ that is similar in size to the liver (1–1.5 kg in weight).34 Indeed, this ‘microbe’ organ is now recognised as rivalling the liver in the number of biochemical transformations and reactions in which it participates.35
The microflora plays many critical roles in the body; thus, there are many areas of host health that can be compromised when the microflora is altered. The GIT microflora is involved in the stimulation of the immune system, synthesis of vitamins (B group and K), enhancement of GIT motility and function, digestion and nutrient absorption, inhibition of pathogens (colonisation resistance), metabolism of plant compounds (for example, phytoestrogens and glycosides), and production of short-chain fatty acids and polyamines.30,36,37
The colon is the most heavily colonised area of the GIT and this microbial ecosystem is believed to play the greatest role in human health. The colonic microflora is composed almost entirely of anaerobic bacteria, with the largest two genera being Bacteroides (accounting for up to 30% of all organisms) and Bifidobacterium (which can constitute up to 25% of total faecal counts). Other numerically important anaerobes include eubacteria, lactobacilli, clostridia and gram-positive cocci. Existing in smaller proportions are coliforms, methanogens, enterococci and dissimilatory sulfate-reducing bacteria. These important groups of bacteria have been divided into species that exert either beneficial or harmful effects on the host, as outlined in Figure 3.1.37 When the beneficial species are present in insufficient numbers or when concentrations of potentially harmful bacteria are relatively high, then dysbiosis is said to result. Dysbiosis is a state in which the microflora produces harmful effects through one or more of the following factors: (1) qualitative and quantitative changes in the intestinal flora itself; (2) changes in their metabolic activities; and (3) changes in their local distribution.38
Optimise the GIT microflora
Probiotics
The term ‘probiotic’ is derived from the Greek and literally means ‘for life’. It was first coined in 1965 by Lilley and Stillwell to describe substances secreted by one microorganism that stimulate the growth of another.39 In 1974, Parker modified this definition to ‘organisms and substances which contribute to intestinal microbial balance’.40 The current World Health Organization definition of probiotics is ‘live microorganisms which when administered in adequate amounts confer a health benefit on the host’.41 Probiotic organisms can be found in fermented foods (such as yoghurt, sauerkraut and kefir), as well as supplements. The microorganisms found in these products are typically lactobacilli and bifidobacteria.42
Probiotics have a long history of successful use in the treatment of IBS. In fact the first case series detailing the efficacy of a Lactobacillus acidophilus supplement in IBS was published in 1955.43 A recent systematic review and meta-analysis of randomised, controlled trials found probiotic use to be associated with improvements in global IBS symptoms compared to placebo and reductions in abdominal pain.44 It is well-known, however, that efficacy in this condition, as it is in all conditions, is strain dependent. Commercially available probiotic strains that have shown efficacy in the treatment of IBS include L. fermentum PCC45,46 and L. plantarum 299V.47,48 Commercially-available strains found to be ineffective in the management of IBS include L. acidophilus NCFM49 and L. rhamnosus GG.50,51
To achieve the desired therapeutic results, it is imperative to prescribe the precise probiotic strains that have demonstrated therapeutic and clinical efficacy in the condition in question. Strains that work in one condition will not necessarily be effective in other conditions. For example, Lactobacillus rhamnosus GG appears to be effective in the prevention of antibiotic-associated side effects,65 but not of any demonstrable benefit in urinary tract infections.66 Tables 3.2 and 3.3 outline the most appropriate probiotic strains and prebiotic to use for specific disease conditions, as determined by human trials.
Table 3.1 Mechanisms of delivery of probiotics, and their advantages and disadvantages
| DELIVERY SYSTEM | ADVANTAGES | DISADVANTAGES |
|---|---|---|
| Fermented foods | • Enhanced bacterial survival through upper GIT (100 × less can be given per dose if given in a dairy base)52 | |
| Capsules | ||
| Tablets | ||
| Powders |
Prebiotics
A prebiotic is defined as ‘a nondigestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon.’53 For food ingredients to be classified as prebiotics, they must:
Most emphasis to date has been on finding and trialling food sources that are used by lactic acid-producing bacteria. This is due to the health-promoting properties of these organisms.42 The best known lactic acid-producing bacteria belong to the genera Lactobacillus and Bifidobacterium. Commonly used prebiotics include lactulose, fructo-oligosaccharides (FOS), and galacto-oligosaccharides (GOS). The most appropriate prebiotics to use for specific health conditions are highlighted in Table 3.3.
Table 3.3 Prebiotics for disease conditions
| DISEASE CONDITIONS | PREBIOTIC |
|---|---|
| Prevention of UTIs | Lactulose (25 g/day) |
| Lowered immunity: decreased rates of infection | FOS (2 g/day in infants) |
| Poor calcium absorption | FOS (8 g/day) |
| Atopic eczema: prevention in infants | GOS and FOS (0.8 g/100 mL formula) |
| Constipation |
One trial has been performed investigating the efficacy of FOS in IBS with disappointing results.54 However, the dose of FOS used in the study (20 g/day in a single dose) is known to cause significant gastrointestinal side effects (such as bloating, distension, borborygmi and increased flatulence).55 Thus it is not surprising that FOS failed
PREBIOTICS VERSUS COLONIC FOODS
There are a number of other substances that are frequently referred to as prebiotics. Many of these, however, fail to meet the criteria outlined above. Slippery elm, psyllium husks, guar gum and pectin would more accurately be described as colonic foods rather than prebiotics as they appear to lack the selectivity of fermentation that is required of prebiotics.56–58 Other substances, such as polydextrose and larch arabinogalactans, have been shown to increase the growth of beneficial bacteria in human trials.59–60 However, they have thus far been the subject of inadequate research to determine if they meet all of the prebiotic requirements.
to reduce these same GIT symptoms in trial participants. It is possible that administration of lower doses of FOS (for example, 3 g/day) or other prebiotic agents (lactulose or GOS) will result in better clinical outcomes.
Synbiotics
Synbiotics are products that contain both probiotic and prebiotic agents.61 The combination is theorised to enhance the survival of the probiotic bacteria through the upper GIT, improve implantation of the probiotic in the colon, and have a stimulating effect on the growth and/or activities of both the exogenously provided probiotic strains and the endogenous inhabitants of the bowel.62 Synbiotics are a promising treatment avenue in C-IBS with two recently published, open-label trials finding a synbiotic preparation (containing a daily dose of 5 × 109 CFU Bifidobacterium longum strain W11 and 2.5 g fructo-oligosaccharides) to significantly decrease abdominal pain and bloating in patients with C-IBS, as well as increasing stool frequency.63,64
Promote daily, easy-to-pass bowel movements
Epidemiological studies have consistently found correlations between dietary fibre intake and improved bowel function.107,108 As the amount of dietary fibre in the diet is increased, mean gastrointestinal transit time decreases, stool frequency increases and stools become softer and easier to pass.107 Clinical trials of fibre supplementation have also consistently found increased bowel movement frequency and improved stool consistency.109
HOW DOES DIETARY FIBRE WORK?
There appear to be at least five ways by which dietary fibre consumption improves laxation. First, plant cell walls that resist microfloral degradation are able to exert a physical bulking effect by retaining water within their cellular structure. This increased bulk stimulates colonic movement. Secondly, the vast majority of consumed dietary fibre is extensively broken down and metabolised by the colonic microflora. This stimulates microbial growth, leading to an increase in microbial products and microbes themselves in faeces – again leading to an increase in faecal bulk. Thirdly, the increase in faecal bulk speeds up the faeces’ rate of passage through the bowel. As transit time decreases, the efficiency with which the bacteria grow improves – further bulking the stools. Shortened transit time also leads to reduced water absorption by the colon and, hence, moister stools. Fourthly, fermentation of dietary fibre by the colonic microflora results in the production of hydrogen, methane and carbon dioxide gas. When trapped within the gut contents they further add to stool bulk.116 Lastly, other end-products of fermentation (short-chain fatty acids, particularly acetate) enhance muscular contraction in the colon.117,118
A recent systematic review and meta-analysis found fibre to significantly improve global IBS symptoms (see Table 3.4, the review of evidence table) and IBS-related constipation. However, fibre supplementation was found to significantly worsen abdominal pain. When soluble fibre was examined in isolation, it was found to induce a greater reduction in global IBS symptoms and to improve constipation in C-IBS subjects. Conversely, insoluble fibre supplementation was found to have no significant effect upon global IBS symptoms, although it did improve constipation. The authors concluded that fibre supplementation appears to be of benefit in improving global IBS symptoms and particularly constipation; it does not, however, improve IBS-related abdominal pain.110
The findings from this systematic review suggest that sources of soluble fibre would be more appropriate therapeutic tools than sources of insoluble fibre in the treatment of C-IBS. Good sources of supplemental soluble fibre include ground flaxseeds,111 slippery elm powder,112 psyllium husks,113 oat bran114 and pectin.115
Fluid intake
Ensuring the intake of adequate fluid is also a vital, although under-researched, therapeutic tool. Positive associations have been observed between bowel movement frequency and fluid intake in epidemiological research.108 Stool frequency and stool weight have also been found to be significantly decreased during enforced periods of low fluid intake in prospective, human research.119 Adequate fluid intake is usually described as 2100–2600 mL daily, although this would need to be increased in warmer climates.120
Exercise
Epidemiological research has found an association between level of physical activity and frequency of bowel habit, with lower levels of physical activity being linked with impaired bowel habit.121 This link between physical activity levels and bowel health is widely known amongst the general populace, with even Roald Dahl remarking in his Revolting Rhymes:122
In support of this connection, prospective human research has found that daily moderate exercise is capable of significantly accelerating gastrointestinal transit time, which should equate to softer, easier-to-pass stools.123 Additionally, a recently published, randomised, controlled trial found daily exercise to significantly improve constipation-related symptoms in IBS subjects.124
Manage GIT symptoms
Although it is a benign disorder, IBS is associated with significant impairments in quality of life.134 Recent research has found that three gastrointestinal symptoms (straining at stool, abdominal pain and abdominal bloating) have the greatest negative impact upon quality of life in IBS sufferers.135 Providing relief from these symptoms should thus be at the forefront of naturopathic management of this condition.
Straining at stool is usually addressed with the agents and interventions discussed in the ‘Promote daily, easy-to-pass bowel movements’ section above. Occasionally, however, laxative herbs are needed at the onset of treatment. Sometimes gentle laxatives like Glycyrrhiza glabra are adequate. In more severe cases of constipation, the anthraquinone-containing laxatives can be used: Senna spp., Rhamnus purshiana,
WHAT IS A ‘NORMAL’ BOWEL PATTERN?
This question should really be broken up into two questions: what is a ‘normal’ bowel habit and what is a ‘healthy’ or ‘optimal’ bowel habit? A ‘normal’ bowel habit has been defined by conventional medicine as between three bowel movements per day to three bowel movements per week. These frequencies are based on epidemiological studies conducted on Western populations which have found the vast majority of individuals to have a bowel frequency within this range, with the most common frequency being once daily.125,126 Constipation is thus defined as less than three bowel movements per week.127
Naturopaths would generally not consider patients who experience three bowel movements per week to have a ‘normal’ bowel habit. Naturopath Henry Lindlahr stated in his 1919 classic Natural Therapeutics that ‘normally a person should have a copious movement of the bowels once in twenty-four hours – twice is better’.128 Studies looking at non-Western populations eating traditional fibre-rich diets found defecation frequencies to average two or three times daily.129 Other studies looking at vegans eating high-fibre diets (about 47 g fibre daily) have found a mean bowel movement frequency of ≥ 1.5 per day.107,108 From these data we can gather that individuals consuming a high-fibre, plant-based diet pass stools more frequently than individuals consuming the typical low-fibre, Western diet (about 11–16 g fibre daily).130 Optimal bowel frequency should be considered to be one, two or three movements daily. Naturopaths generally consider patients as being constipated if they experience less than one bowel movement daily.
Bowel habit: men versus women
Studies have consistently found men to have an increased frequency of daily bowel movements, to produce a greater quantity of faeces daily, to have shorter gastrointestinal transit times and to have softer, less-formed faeces than women.107,108,125 Stool form and bowel movement frequency also appears to vary in women according to the menstrual cycle. During the luteal phase of the cycle, gastrointestinal transit time significantly slows, resulting in more formed, harder stools.107
What is the ‘perfect’ bowel movement?
In terms of consistency, the most common stool passed by typical Western populations is well-formed (sausage or snake-like) with either cracks on its surface or a smooth and soft surface (types 3 and 4 in Figure 3.2).125 Populations consuming a predominantly plant-based, high-fibre diet, on the other hand, have softer, bulkier stools that tend to be less formed and more ‘mushy’ (type 5). These stools are associated with shorter gastrointestinal transit times, whereas harder stools are associated with longer transit times.107 So, what is the perfect bowel movement? Optimal stool form should vary between well-formed, sausage-like stools with cracks on its surface (type 3) through to softer blobs with clear-cut edges (type 5). In addition, there should be little-to-no straining at stool, little urgency and a feeling of complete evacuation after the event.131
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