A systematic review of high-fibre dietary therapy in diverticular disease
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- Ünlü, C., Daniels, L., Vrouenraets, B.C. et al. Int J Colorectal Dis (2012) 27: 419. doi:10.1007/s00384-011-1308-3
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The exact pathogenesis of diverticular disease of the sigmoid colon is not well established. However, the hypothesis that a low-fibre diet may result in diverticulosis and a high-fibre diet will prevent symptoms or complications of diverticular disease is widely accepted. The aim of this review is to assess whether a high-fibre diet can improve symptoms and/or prevent complications of diverticular disease of the sigmoid colon and/or prevent recurrent diverticulitis after a primary episode.
Clinical studies were eligible for inclusion if they assessed the treatment of diverticular disease or the prevention of recurrent diverticulitis with a high-fibre diet. The following exclusion criteria were used for study selection: studies without comparison of the patient group with a control group.
No studies concerning prevention of recurrent diverticulitis with a high-fibre diet met our inclusion criteria. Three randomised controlled trials (RCT) and one case–control study were included in this systematic review. One RCT of moderate quality showed no difference in the primary endpoints. A second RCT of moderate quality and the case–control study found a significant difference in favour of a high-fibre diet in the treatment of symptomatic diverticular disease. The third RCT of moderate quality found a significant difference in favour of methylcellulose (fibre supplement). This study also showed a placebo effect.
High-quality evidence for a high-fibre diet in the treatment of diverticular disease is lacking, and most recommendations are based on inconsistent level 2 and mostly level 3 evidence. Nevertheless, high-fibre diet is still recommended in several guidelines.
KeywordsHigh-fibre dietary therapy Diverticular disease Sigmoid colon
Diverticulosis of the colon is an acquired condition resulting from herniation of the mucosa through defects in the muscle layer of the bowel wall. The condition is rare in developing countries but common in Western and industrialized countries. Approximately 60% of humans over age 60 living in westernized countries will develop colonic diverticula . In the great majority of cases, the condition is asymptomatic with only 10% to 25% of affected individuals developing symptoms [2, 3]. Symptomatic diverticular disease results in an annual hospitalization rate of 130,000 in the USA .
Autopsy series from 1920 to 1940 identified diverticulosis present in 2% to 10% of individuals [5, 6]. In later autopsy studies, the presence of diverticulosis increased up to 20–50% [7, 8, 9, 10, 11]. This sharp rise in the incidence of diverticulosis has been largely attributed to dietary changes, mainly in the decline of dietary fibre intake from cereal grains . Burkitt and Painter first proposed the initial hypothesis of a fibre deficiency as the aetiology of diverticular disease in 1971. While Burkitt was in Uganda, he found that diverticulitis was virtually nonexistent in rural Africa. He investigated fibre intake, stool weight and transit time, by comparing a rural Ugandan population to an English population. The Ugandan population had a lower average transit time and a lower stool volume compared to the English population who had a diet with higher refined sugar and lower dietary fibre .
The hypothesis is that decreased dietary fibre intake results in decreased intestinal contents and smaller size of the lumen. This in turn results in the transmission of muscular contraction pressure to the wall of the colon rather than to the contents of the lumen. The result of increased pressure on the wall is the formation of diverticula at the weakest point in the wall, namely the sites of penetration by blood vessels, called vasa recta . This systematic review summarizes the results of studies investigating high-fibre diet in the treatment of diverticular disease and discusses the evidence and the aetiology of diverticular disease.
A Medline search was performed to identify guidelines issued by professional organisations on the conservative treatment of diverticulitis and recommendations on the use of high-fibre diet. A Google search was used to identify guidelines not published in Medline indexed journals. We evaluated (a) whether or not high-fibre diet will prevent symptomatic diverticular disease, (b) whether or not high-fibre diet is mandatory in treatment of symptomatic diverticular disease and (c) whether or not high-fibre diet will prevent recurrence. The evidence supporting the recommendations was noted, specifically references to original research dealing with high-fibre diet in symptomatic diverticular disease. Only practice parameters and guidelines published by professional organisations between 1999 and 2010 were included.
Two authors (CU, LD) independently performed a literature search to identify studies investigating the effectiveness of a high-fibre diet in human subjects proven of diverticular disease. In our search, we have also included the articles that compared use of fibre supplement such as methylcellulosis or psyllium seed husks with placebo. We searched MEDLINE databases for papers published between January 1966 and January 2011, using the following keywords: (((“Diverticulitis, Colonic” [MeSH] OR “Diverticulitis, Colonic/diet therapy” [MeSH])) OR “Diverticulum, Colon” [MeSH]) AND “Dietary Fiber/therapeutic use” [MeSH]. EMBASE database was searched with the following terms: diverticulosis and high-fibre diet. CINAHL database was also checked for relevant studies with the following keywords: (MM “Diverticulum, Colon”) AND (MM “Dietary Fibre”) or (MM “Diet Therapy”)). The Cochrane Database of Systematic Reviews was searched with the following words: Diverticular disease and fibre diet.
The “related articles” function in PubMed and reference lists of retrieved articles were also used to identify articles not found in the original search. Clinical studies published in English were included. No unpublished data or abstracts were included.
After identifying relevant titles, all abstracts were read and eligible articles were retrieved. A manual cross-reference search of the bibliographies of relevant articles was performed to identify other studies not found in the search. Only clinical studies published in English were included. No unpublished data were included. A full search strategy is available at request. Two authors independently assessed the methodological quality of the articles using the Jadad score and the checklist of the Cochrane collaboration. The Jadad score is a well-known instrument assigning a numerical score between 0 and 5 to each study, reflecting its quality (0 indicating poor quality and 5 high quality) .
Diverticular disease comprises a wide spectrum of conditions; in order to be able to reliably compare the data, uncomplicated diverticular disease was defined as symptomatic disease associated with colonic diverticula. This is associated with mild symptoms, usually abdominal pain and/or change in bowel habit, but without clinical features of inflammation. Diverticulosis is asymptomatic colonic diverticula. Diverticulitis is complicated diverticular disease with severe clinical symptoms and evidence of inflammation. Complicated diverticulitis is perforation, abscess, fistula, bleeding or stricture/obstruction, usually needing surgical, percutaneous or, in case of bleeding, endoscopic intervention.
Inclusion and exclusion criteria
Types of studies
Clinical studies were eligible for inclusion if they assessed the treatment of symptomatic diverticular disease or the prevention of recurrent diverticulitis with a high-fibre diet. The only exclusion criterion used for study selection was studies without comparison of the patient group with a control group.
Types of participants
Patients of 18 years or older diagnosed with uncomplicated diverticular disease or an episode of acute diverticulitis were included. The diagnosis had to be confirmed by barium enema, colonoscopy, ultrasonography or computed tomography (CT).
Types of interventions
Studies that compare high-fibre intake vs low-fibre intake were searched. Also studies on the effect of different kinds of fibres, soluble or insoluble, were included.
Types of outcome measures
Primary endpoint parameters for inclusion were the occurrence of complicated diverticular disease (e.g. diverticulitis, abscess, perforation) or recurrent diverticulitis after a primary episode of diverticulitis. Secondary endpoints were severity of symptoms and pain by diverticular disease, morbidity and mortality.
Organisations with advises concerning fibres
Fibres recommended preventing diverticular disease
Original research cited
Fibres recommended in treatment of symptomatic diverticular disease
Original research cited
Fibres recommended in preventing recurrence of diverticulitis
Original research cited
American College of Gastroenterology 
Aldoori et al. 
European Association for Endoscopic Surgery 
American Society of Colon and Rectal Surgeons 
World Gastroenterology Organization 
Relevant excluded studies
Number and type of participants
Type(s) of treatment
Reason(s) for exclusion
Painter et al. 
Prospective interventional study
70 unselected patients with diverticular disease proven by barium enema
High-residue, low-sugar diet together with unprocessed bran for an average of 22 months
Symptoms in 88.6% of patients relieved or abolished
No control group
None of the 62 patients who took the diet needed surgery
Plumley and Francis 
Prospective interventional (partly cross-over) study
48 patients with the “spastic colon” type of diverticulosis proven by barium enema
HFC (OR normal crispbread) for at least 2 months
Of 42 patients suffering pain 69% were controlled satisfactorily on HFC
Only 14 patients took part in the cross-over trial (HFC → normal crispbread) of which the design was unclear and no results were mentioned
Of the total of 98 presenting symptoms 73% were controlled satisfactorily on HFC
5 patients required surgery
Brodribb and Humphreys 
Prospective interventional study
40 patients with diverticular disease proven by barium enema
Wheat bran 24 g/day for at least 6 months
60% of all symptoms were abolished, and a further 28% were relieved
No control group
Taylor and Duthie 
Cross-over randomised trial
20 patients with symptomatic diverticular disease (confirmed by barium enema)
HRD or Normacol plus an antispasmodic or bran tablets for 2 periods of 1 month
All patients experienced some improvement with each treatment: 20% of patients was symptom-free after HRD, 40% after Normacol and 60% after bran tablets
No high vs low-fibre diet but vs supplements
8 included patients were recently diagnosed with acute diverticulitis, 2 were surgically drained
Devroede et al. 
80 diverticular disease patients
Six treatments (high-residue, low-residue or no specific diet, with placebo or Metamucil)
With Metamucil a significant reduction of symptoms (p < 0.025) and more patients without symptoms (p < 0.05)
No significant differences between diet treatments
Radiological confirmation of diagnosis not mentioned
Eastwood et al. 
Non-randomised prospective study
31 patients with diverticular disease proven by barium enema
Bran or ispaghula (Fybogel) or lactulose for 4 weeks period
All agents equally alleviated symptoms
No high vs low-fibre diet compared but different fibre supplements and a laxative
Ewerth et al. 
Double-blind cross-over randomised trial
9 patients with constipation as well as diverticuli on barium enema
Vi-Siblin (6 g ×2) OR placebo (lactose 6 g ×2) during 2 periods of 8 weeks with 4-week interval
Less symptoms with Vi-Siblin (2 vs 16)
Only 9 patients included
Significant improvement of constipation with Vi-Siblin (p < 0.05)
Selection bias: constipation as initial complaint, diverticuli possibly accidental non-causative finding
Hyland and Taylor 
Retrospective cohort study
100 patients with acute diverticular disease
91% of patients on a high-fibre diet reviewed 5 to 7 years after admission had remained symptom-free
It is uncertain whether the patients have diverticulitis or symptomatic diverticular disease
Smits et al. 
43 patients with a confirmed diagnosis of diverticular disease
High-fibre diet (30–40 g daily) or lactulose (15 ml bd) for 12 weeks
Both treatments effective with respect to abdominal pain and bowel movement improvement, even some differences in favour of lactulose
No high vs low-fibre diet compared but high-fibre diet vs laxative
Dietary fibre to prevent recurrence of diverticulitis
No dietary fibre study met the inclusion criteria of this systematic review question.
Dietary fibre for symptomatic diverticular disease
Randomised controlled trials
Results of Stollman and Raskin RCT 
High-fibre group (mean scores initial vs 3 months; n = 9)
Low-fibre group (mean scores initial vs 3 months; n = 9)
Total symptom score
34.3 to 8.1
42.0 to 35.1
11.1 to 1.1
12.7 to 10.2
11.4 to 3.7
14.7 to 11.6
11.7 to 3.3
14.9 to 13.3
Results of Köhler et al. RCT 
Treatment period N = 58
Lower bowel symptom score
General symptom score
Quality assessment and study design of RCT
Köhler et al. 
Stollman and Raskin 
Rafferty et al. 
High-fibre vs low-fibre diet
High-fibre vs low-fibre diet
Methylcellulose vs placebo
Number intervention/number comparison
Treatment allocation concealed?
Eligibility criteria specified?
Outcome assessor blinded
Care provider blinded?
Groups similar at baseline?
Intention to treat?
Results of the study of Leahy et al. 
High-fibre group (n = 31)
Low-fibre group (n = 25)
Surgery due to diverticular disease
8 (p < 0.05)
Mean follow-up (months)
Symptomatic at follow-up
11 (p < 0.05)
No comparative studies were found that assessed the effect of fibre diet in the recurrence rate of diverticulitis. The only three published randomised trials in patients with diverticular disease examining the effect of a high-fibre diet or fibre supplement showed inconsistent results. One RCT has found a significant reduction in pain and improvement of overall symptoms , while a second RCT has found no effect on pain and large bowel symptoms, except for reduction of constipation . The third trial  showed a significant treatment effect of methylcellulose on symptoms. These trials have non-specific and subjective symptom outcomes. Their sample size is far too small to demonstrate a difference in objective outcomes such as the incidence of acute diverticulitis or other complications of diverticular disease (e.g. abscess, perforation, stenosis, fistula or bleeding).
Other interventional studies that had an observational before–after design were not included in the present review because they lacked a control group. These types of studies have found a significant reduction in symptoms associated with diverticular disease with the use of a high-fibre diet [19, 27, 28]. Studies that compared a high-fibre diet with fibre supplements, such as lactulose or bran tablets, have found no advantage of one over the other [30, 34, 37]. A study comparing high-fibre, low-fibre, no specific diet, placebo and Metamucil showed that all treatment options gave reduction of symptoms. Metamucil showed the most significant reduction in symptoms. The authors suggest also a possible placebo effect of dietary therapy . These studies are summarized in Table 2.
The initial hypothesis of Burkitt and Painter in 1971, which was based on a fibre deficiency as crucial factor in the aetiology of diverticular disease, has weaknesses in the evidence when one considers the populations under study. The increased lifespan of western populations throughout the twentieth century may parallel the increasing prevalence of diverticulosis. In the epidemiological studies, life expectancy has improved in the last 80 years in the Western world. On the African continent, life expectancy remains low. The World Health Organisation data report a life expectancy of 51 years for both South Africa and Kenya, the African countries from which necropsy data were referenced by Burkitt and Painter . The prevalence of diverticular disease increases with age to up to 50–66% in patients older than 80 years . The fibre hypothesis was studied in a large prospective follow-up study consists of a cohort of 51,529 male US health professionals, enrolled and interviewed in 1986 and interviewed about developing diverticular disease in 1990 and again in 1992 . Fibre intake of individual participants has been measured before development of diverticular disease. In this cohort, fruit and vegetable intake, cellulose, hemicellulose and lignin are inversely associated with the risk of symptomatic diverticular disease. Insoluble fibre reduces the risk of diverticular disease by 37% (relative risk (RR) 0.63, 95% confidence interval (CI) 0.44 to 0.99) and cellulose by 48% (RR 0.52, 95% CI 0.36 to 0.75) . Epidemiological and observational studies have been the two predominant approaches to illuminate the role of diet and lifestyle in the prevalence of diverticular disease [20, 40]. The epidemiological approach is currently confounded by the lack of available up-to-date data on prevalence in different populations.
Despite the lack of evidence, high-fibre diet as treatment for symptomatic diverticular disease, is been recommended in several guidelines [14, 18, 21, 24]. All of the evidence is based on two small sample size randomised clinical trials, with inconsistent results, or observational uncontrolled studies more than 20 years ago. Some of the references given in the several guidelines have not been discussed in this review because the inclusion criteria were not met or were expert opinion papers [19, 20, 22, 23, 25, 26]. In the case of high-fibre diet therapy to prevent recurrent diverticulitis, two guidelines [18, 21] advised high-fibre diet to prevent recurrence. None of the cited papers actually investigate or discuss this advise. One of the guidelines provides no evidence. All of the references given are discussed in this review or summarized in Table 2. Painter  gives a summary of his previous study  together with a review. Larson et al.  discuss surgical treatment vs medical treatment. The other references [25, 26] are reviews.
In present literature search, no study was found enrolling patients with acute diverticulitis. One study enrolled 100 patients with acute diverticular disease of which 25 patients had been operated to evaluate a high-fibre diet . It is uncertain whether these patients have diverticulitis or symptomatic diverticular disease, but inclusion criteria suggest a mixed population. Ninety-one percent of patients on a high-fibre diet reviewed 5 to 7 years after admission had remained symptom-free. It was concluded that high-fibre diet may have a protective role and prevent further complications. This was essentially pre-CT scan era, and therefore, the accurate diagnosis of diverticulitis remains in question.
New hypotheses have emerged which can be helpful in fully understanding the aetiology of diverticular disease. Diverticulosis may be ultimately proved to be a disease of ageing. Recent studies show increasing mitochondrial dysfunction in the ageing colonic epithelia, and these data correlate well with diverticulosis prevalence [41, 42]. Studies of mitochondrial deficiency or other age-associated changes in the colonic muscle might further illuminate the pathology of this condition. Another hypothesis in which environmental factors play a role is the colonic microflora in the disease process. Two studies emphasize the differences in microflora composition between high (Western)- and low (African/Asian)-risk populations [43, 44]. A direct comparison of the faecal and colonic mucosal flora between cases and controls might reveal differences associated with the altered luminal environment. The other way around, diverticulosis may also alter the colonic mucosal flora. New research is needed to distinguish these hypotheses. It seems probable that dietary and/or luminal environmental factors protect against diverticula formation, but solid evidence is lacking.
In conclusion, high-quality evidence for a high-fibre diet in the treatment of diverticular disease is lacking, and most recommendations are based on inconsistent level 2 and mostly level 3 evidence. Nevertheless, high-fibre diet is still recommended in several guidelines.
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