Chapter 3.21
Constipation and nutrition
Yolande M. Causebrook and Chris Speed
Newcastle University, Newcastle upon Tyne, UK
Constipation in adults is often trivialised. However, it is a frequent (2–34% of the population in Western countries) and often debilitating medical problem, generating many medical visits and having a considerable impact on individual physical and emotional well-being [1–3].
3.21.1 Definitions and types
Functional constipation (primary or idiopathic) is chronic constipation with an unknown cause [4]. Several physiological subtypes have been described.
- Colonic inertia or slow transit constipation – when movement of GI contents through the colon is slowed.
- Outlet delay constipation (or obstructed defaecation) – which can be caused by pelvic floor dyssynergia (the pelvic floor muscles contract or fail to relax during attempted defaecation) and by anismus (the external anal sphincter contracts instead of relaxing during attempted defaecation).
- Normal transit constipation (without delays in colonic transit or outlet delay) – the least clearly defined and most common subgroup.
Secondary constipation (organic constipation) is caused by a drug or medical condition. Faecal loading/impaction is retention of faeces resulting in difficulty in evacuation. Retained faeces are usually palpable on abdominal examination, and may be felt on internal rectal examination or by external palpation around the anus.
Although constipation means different things to different people, frequency, consistency and normal bowel movements are considered as important criteria to clinicians and patients; it is how these criteria are perceived that differs. The Rome Criteria are considered as the gold standard for constipation and are useful in clinical practice and research [5,6].
Rome III defines functional constipation as a functional bowel disorder that presents as persistently difficult, infrequent or seemingly incomplete defaecation, which does not meet irritable bowel syndrome criteria and includes the criteria shown in Box 3.21.1 [6]. These can be used with the Bristol Stool Form Scale, which helps define stool types and evaluate transit time, to provide a comprehensive clinical definition.
A patient’s perception of constipation may include the objective observation of infrequent defaecation patterns and the subjective complaints of straining at stooling, incomplete evacuation, abdominal bloating or pain, hard or small stools, or a need for digital manipulation to enable defaecation. Stool frequency, as a measure, is imprecise, as it varies between healthy individuals, let alone constipated patients.
3.21.2 Factors involved in causation
Demographics
Although there is a lack of consensus on the prevalence rates of constipation, many researchers have found that certain demographic and dietary factors may increase causation. Constipation is reported to be higher in women than men (median female:male ratio of 1.5) [6] and this persists after age adjustment. Age is inversely associated with constipation, with increasing prevalence of constipation affecting the very young or the very old [7]. Constipation among older people could be due to changes in mobility, diet, fluid intake or polypharmacy. The use of laxatives increases with age, with adults over 65 being frequent users, even when bowel movements would be described as ‘normal’ by clinicians [3,7–9]. Independent living also plays a role in the prevalence of constipation in older people. Healthy, active individuals living in the community are often less likely to experience functional constipation than those in institutions (including hospitals) [3,7,9].
Constipation affects non-white people more than white [6]. Reasons for this are unclear, but it may be linked to dietary differences or genetics. A strong relationship exists between low socioeconomic groups and greater reporting of constipation [3]. This may be related to poor diet and reduced level of physical activity or limited education, as socioeconomic position is often associated with lower attained education level.
Non-starch polysaccharides
It is often said that the prevalence of constipation has increased due to modern food processing methods, resulting in a diet low in non-starch polysaccharides (NSP) [10]. However, a low NSP diet should not be assumed to be the cause of constipation, but possibly a contributory factor [11]. Although evidence is controversial, intake of NSP, mostly insoluble fibre, has been shown to be beneficial [6] and to increase gut transit time, faecal weight and bowel frequency in healthy individuals, but also in some constipated patients [11]. Constipation is often lower among vegetarians [7] and in developing countries, where higher amounts and types of NSP are consumed. Many people with constipation, especially the elderly, report having a low NSP intake because of chewing difficulties and/or denture problems. There are a few cases where high NSP is contraindicated: patients with secondary to slow transit and/or pelvic floor dyssynergia, or where abdominal distension has worsened or resulted in incontinence (mostly in the elderly) [12]. However, these represent a minority.
Fluid
Dehydration is a risk factor [12,13], slowing colonic transit or lowering stool output in healthy adults. This is a problem among the elderly, who tend to drink less in an attempt to control continence. Evidence for increasing fluid intake generally or when NSP is ingested is controversial [14].
3.21.3 Dietary effects of disease or its management
Constipation is common in irritable bowel syndrome and symptomatic diverticulosis or diverticulitis leading to an overlap of risk factors between those diseases and functional constipation.
Reduced NSP intake is believed to be a contributory factor to functional constipation. The greatest effect on constipation seemed to be related to the insoluble fibre component, especially cellulose, found in fruit and vegetables, rather than in cereals [11,15]. Insoluble fibre is known to increase faecal bulk and be a potent stimulus to colon transit [16], which may result in reduced constipation symptoms. Diverticulosis is generally asymptomatic [11,15]. However, when active, NSP should be decreased to reduce pain and bloating sensation, but increased gradually when symptoms lessen. Although symptoms may worsen initially, improvement should follow after a few weeks. Intake of a high-fibre diet is in line with healthy dietary recommendations, but any treatment management should be carefully monitored.
3.21.4 Dietary treatments
A multifaceted approach is preferred to treat patients with functional constipation, with dietary and lifestyle changes being the first step. If unsuccessful, fibre supplements can be used, and if this fails then laxative treatment can be given [1,7]. The latter is currently the most used by health professionals and patients, especially among the elderly population. However, there is little evidence to support either their clinical or cost-effectiveness. Emmanuel designed a draft algorithm for such an approach, which is useful as there is no treatment protocol at present, probably due to the complexity of the condition and the lack of uniformity in defining it [17]. Although toileting time [13], posture [18], physical activity [8] and psychological counselling [2] are important aspects of constipation management, only the dietary aspect of the treatment will be considered here.
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