Systematic review: the effect of prunes on gastrointestinal function

Background Prunes (dried plums) are high in fibre and are perceived to promote healthy gastrointestinal (GI) function. Aim To assess the effect of prunes on GI function through a systematic review of randomised controlled trials (RCTs). Methods Sixteen electronic databases were searched, a hand search was performed and key opinion leaders were contacted. RCTs investigating the effect of prunes on GI function were included. Two reviewers independently screened relevant articles, extracted data and assessed risk of bias. Results Four trials met the inclusion criteria, one in constipation and three in non-constipated subjects. In constipation, 3 weeks of prune consumption (100 g/day) improved stool frequency (3.5 vs. 2.8 CSBM per week, P = 0.006) and stool consistency (3.2 vs. 2.8 on Bristol stool form scale, P = 0.02) compared with psyllium (22 g/day). In non-constipated subjects, prunes softened stool consistency in one trial and increased stool weight (628 g vs. 514 g/72 h wet weight, P = 0.001) in another trial, compared with control. No trials found differences in GI symptoms between prunes and comparator. Meta-analysis was not appropriate due to heterogeneity in populations and methods. Two of the trials were limited by unclear risk of bias. Conclusions In constipation, prunes appear superior to psyllium for improving stool frequency and consistency, however, the evidence for other outcomes and the effects in non-constipated subjects is weak. Although prunes may be a promising intervention for the management of constipation and increasing stool weight, this needs to be confirmed by further rigorous research.