Chronic constipation affects 15–20% of people in the UK⁽ Reference Suares and Ford ^{1 )}. Lifestyle modifications such as increased dietary fibre intake are recommended as first line therapy but the evidence base for this is poor⁽ Reference Suares and Ford ^{2 )}. Prunes (dried plums) are commonly believed to have a laxative effect⁽ Reference Muller-Lissner, Kaatz, Brandt, Keller and Layer ^{3 )} and used as a traditional remedy to improve bowel function, however there has been no systematic review of the quality or number of clinical trials investigating the efficacy of prunes on gastrointestinal health in constipated or healthy subjects.

The aim of this study was to assess the effect of prunes on markers of gastrointestinal health in constipated and healthy subjects through a systematic review of randomised controlled trials (RCTs).

Sixteen electronic databases were searched, a hand search of reference lists and cited articles of relevant reports and review articles was performed and key opinion leaders were contacted. Only RCTs investigating the effect of prunes on gastrointestinal health were included. Two reviewers independently screened the relevant articles, extracted the data and assessed risk of bias.

Four RCTs were eligible⁽ Reference Tinker, Schneeman, Davis, Gallaher and Waggoner ^{4 –} Reference Lucas, Hammond, Mocanu, Arquitt, Trolinger, Khalil, Smith, Soung, Daggy and Arjmandi7 ⁾. All evaluated the effect of prune consumption versus another food on markers of gastrointestinal health. One study was conducted in constipated patients and three studies were in healthy subjects. Meta-analysis was not possible due to variability in how outcomes were assessed and reported. Due to lack of adequate reporting there was unclear risk of bias for many quality components. All four trials examined the effect of prunes on stool frequency, consistency and gastrointestinal symptoms. Only one, conducted in constipated patients, reported that prunes significantly increased stool frequency (3.5 ± 0.2 vs. 2.8 ± 0.2 complete spontaneous bowel movements/week)⁽ Reference Attaluri, Donahoe, Valestin, Brown and Rao ^{6 )}. Two of the four studies reported that prunes led to an improvement in stool consistency (3.2 vs. 2.8 on 7-point Bristol stool scale)⁽ Reference Howarth, Petrisko, Furchner-Evanson, Nemoseck and Kern ^{5 ,} Reference Attaluri, Donahoe, Valestin, Brown and Rao6 ⁾. One of the four studies examined the effect of prunes on stool weight and faecal bile acid concentration in which prunes significantly increased stool weight (628 g ± 43.9 vs. 514 g +/− 34.0 72 hr wet weight) and reduced faecal concentration of lithocholic acid (0.95 mg vs. 1.20 mg/g dry weight stool) in healthy subjects⁽ Reference Tinker, Schneeman, Davis, Gallaher and Waggoner ^{4 )}.

Despite the commonly held belief that prunes have a laxative effect, the evidence for this is limited. There was heterogeneity in methods and findings and studies were limited due to unclear risk of bias and lack of adequate reporting. It is unclear if the findings have clinical relevance. This review has highlighted the need for well conducted and reported RCTs investigating the effect of prunes on gastrointestinal health in constipated and healthy individuals.