An industry-funded randomized trial assessed the effect of daily consumption of kiwifruit versus psyllium on GI function and comfort in 184 adults who were healthy, had functional constipation (FC), or met Rome III diagnostic criteria for constipation-predominant irritable bowel syndrome (IBS-C). Participants in Italy, Japan, and New Zealand consumed either two green kiwifruits or 7.5 g of psyllium per day for four weeks. There was a two-week lead-in period and a four-week washout period, after which the interventions were reversed. Compared with psyllium, daily kiwifruit increased spontaneous bowel movements in participants with FC or IBS-C.
The study was published Jan. 9 by the American Journal of Gastroenterology. The following commentary by ACP Resident/Fellow Member Blake J. Purtle, MD, and Brooks D. Cash, MD, FACP, was published in the ACP Journal Club section of the May Annals of Internal Medicine.
Current guidelines and good clinical practice endorse diet and lifestyle modifications as first-line therapy for FC and IBS-C. Previous studies that compared green kiwifruit with psyllium or prunes showed no differences in increases in bowel movement frequency and consistency but greater improvements in abdominal symptoms with kiwifruit. Kiwifruit contains enzymes that facilitate the digestion of proteins, starches, and sugars, as well as calcium oxalate crystals that are thought to enhance mucin production.
Gearry and colleagues compared green kiwifruit with a comparable dose of psyllium in adults with FC, IBS-C, and healthy controls across 3 geographically and ethnically diverse countries. They showed meaningful improvement in complete spontaneous bowel movement (CSBM) frequency in patients with FC and IBS-C with kiwifruit vs. psyllium. GI comfort level in patients with IBS-C improved more with kiwifruit than psyllium. The trial was adequately powered and used a randomized, controlled, crossover design with concealed allocation and an appropriate washout period between interventions to minimize carryover effects. Although participants were unblinded and 4 weeks is a short intervention duration, the investigators adequately controlled for these issues and demonstrated that systematic bias was unlikely. Moreover, the increase in weekly CSBMs was greater than the increase used in regulatory studies of pharmaceutical agents for chronic constipation (>1 CSBM per wk).
Data to support the common recommendations of diet manipulation and lifestyle modifications for chronic constipation syndromes are sparse, and the findings of the trial by Gearry and colleagues bolster these recommendations. Studies of dietary interventions for FC and IBS-C can inform evidence-based recommendations for low-cost, broadly accessible and acceptable interventions that are often free from common adverse effects associated with pharmaceutical therapies. Additional studies on the effect of diet on GI function and symptoms are encouraged.