Chey SW, Chey WD, Jackson K, Eswaran S. Exploratory comparative effectiveness trial of green kiwifruit, psyllium, or prunes in US patients with chronic constipation. Am J Gastroenterol. 2021;116(6):1304-1312.
A partially randomized, comparative-effectiveness trial conducted on adults with chronic constipation at a US medical center
To determine the comparative effectiveness of psyllium, prunes, and kiwifruit on symptoms of chronic constipation in a US-based study population
Investigators recruited eligible patients from those who met the Rome IV criteria for either functional constipation (FC) or irritable bowel syndrome with constipation (IBS-C).
Out of the original 247 patients who were approached for study recruitment, 109 were enrolled for baseline screening, and 79 patients satisfied inclusion criteria and were randomized (69 female [87%], with a mean age of 42.7 years [range 18–76 years]).
Inclusion criteria included adult having chronic constipation (CC) for the last 3 months with symptoms at least 6 months earlier; the absence of loose stools without the use of laxatives, as well as the presence of other CC symptoms such as a daily abdominal pain score ≤7 (on a scale of 1–10, 10=worst pain); having ≤3 complete spontaneous bowel movements (CSBM) per week; and having at least 2 of the following symptoms: straining, hard/lumpy stools, incomplete emptying of bowels, utilization of manual maneuvers for relief, and a sensation of obstruction or blockage on ≥25% of bowel movements (BMs).
Exclusion criteria included having any of the following: severe abdominal pain (>7 on the scale of 1–10), presence of gastrointestinal (GI) bleeding, unexplained iron deficiency, unexplained weight loss, active anal fissures, and significant comorbid chronic disease, history of GI surgery, or neurological disease. Also excluded were pregnant women and patients taking probiotics, antibiotics, or opioids or with allergy to study ingredients.
Participants were entered into a 2-week baseline screening period to assess symptoms through daily questionnaires. Those who qualified were then randomized into 3 study arms for a 4-week treatment period, to be then followed with a 2-week observation period.
- 2 whole green kiwifruit daily, peeled (Actinidia deliciosa var. Hayward), fiber=6 g/day
- 50 g prunes (about 6 prunes) twice daily (Kirkland brand), fiber=6 g/day
- 6 g of psyllium twice daily, dissolved in water (Metamucil brand), fiber=6 g/day
Researchers and participants were not blinded to the allocated intervention. Due to availability of fresh kiwifruit, the investigators allocated the first 30 enrolled patients into the kiwifruit arm and randomized through computer generation the remaining patients into the prune or psyllium arms.
Investigators instructed all participants to avoid eating all other food containing kiwi, psyllium, or prunes or adding any high-fiber fruits/vegetables to their diets during the study.
Study Parameters Assessed
Patients answered daily symptom questionnaires, and investigators collected diet assessments by 3-day food diaries after the screening period and after the treatment period.
Primary Outcome Measure
The primary outcome measure was the proportion of participants in each group reporting an increase of 1 or more CSBMs per week compared with the baseline screening period for at least 2 of the 4 weeks of intervention. The groups were not compared to each other.
Secondary outcome measures included effects on frequency, consistency, straining, and sensation of incomplete evacuation. Satisfaction and dissatisfaction with the treatment were also tracked.
For the primary outcome of an increase in BMs by at least 1 weekly, the proportions of responders to therapy were 45% for the kiwifruit group (13/29; 95% CI [0.27–0.63]); 67% for the prunes group (16/24; 95% CI [0.48–0.86]); and 64% for the psyllium group (14/22; 95% CI [0.44–0.84]). There was no statistically significant difference in number of responders between groups, indicating that all of them were equally effective in increasing the number of CSBMs.
Kiwifruit stood out in this study for 1 other reason: Participants disliked it the least.
When investigators considered the entire 4-week treatment period, the prune group had the greatest average change in CSBMs (+2.1; P<0.001) with the psyllium group second (+1.4; P=0.005) and kiwi the least effective (+1; P=0.0049).
For secondary outcomes comparing weeks 3 and 4 to baseline, there was a significant weekly CSBM rate in all 3 treatment groups (P≤ 0.003). Stool consistency significantly improved with kiwifruit (P=0.01) and prunes (P=0.049). Straining significantly improved with kiwifruit (P=0.003), prunes (P<0.001), and psyllium (P=0.04). Patients in the kiwifruit group also reported a significant decrease in bloating (P=0.02).
When it comes to chronic constipation, fiber is king! Ensuring adequate dietary fiber is a critical component of a treatment plan for constipation, as insoluble fiber adds bulk to stool and soluble fiber assists with retaining fluid in the stool, softening it, and ensuring it is easy to pass. Fiber is also necessary for a normal microbiota in the gut, and some flora is known to contribute to gut motility. The latest Dietary Guidelines for Americans, 2020–2025, states that “over 90% of women and 97% of men do not meet recommended daily intakes for dietary fiber.”1 A high plant-based diet with an emphasis on fiber-rich foods is recommended for nearly all patients, and at least some of those with constipation may simply need to eat more fiber daily (see table below).
Table: Recommended fiber intake (in grams) by age & gender2-4
When increasing dietary fiber is not enough to resolve constipation, clinicians commonly recommend soft fruits or dietary supplements such as flax, psyllium, or other fibers to improve stool.
In this study, there were no statistically significant differences between the 3 groups in the primary outcome measure, CSBMs.
Similar to past studies on prunes, psyllium, and kiwifruit, all 3 agents relieved constipation to some extent. The 1 difference is that in this study, the benefits of kiwifruit seemed to decline after 2 weeks of consumption, although it did remain statistically significant compared to baseline (P=0.002). This contradicts previous studies, which show no drop-off in efficacy over time with kiwifruit.5,6
One finding in this study, which has been found in prior studies on kiwifruit, is that kiwifruit appears to be better tolerated in those with constipation, with a lower incidence of symptoms such as gas and bloating than either prunes or psyllium. The authors speculate that this may be attributable to the sugar composition of kiwifruit, which is relatively low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) in comparison to prunes.
Kiwifruit stood out in this study for 1 other reason: Participants disliked it the least. The authors reported that “There was a statistically significantly lower proportion reporting treatment dissatisfaction between kiwifruit and the other groups (7% kiwifruit vs 17% prunes and 38% psyllium, P=0.02).”
This study was interesting, as the thought of comparative effectiveness of these fiber additions may not have been a prior consideration for practitioners. There are numerous studies comparing effectiveness between supplements but fewer that compare food sources of fiber.7 Understanding that some fiber sources can influence other aspects of digestion or be more easily tolerated can aid the practitioner in selecting the best fiber for even their most sensitive patients.
This study is informative in that it validates the use of any 1 of these substances for chronic constipation, with some interesting differences in their effects. The key to any effective treatment is compliance. This study validates the use of psyllium and prunes for chronic constipation and offers the possibility of kiwifruit for those patients who do not tolerate psyllium or prunes.
- Dietary Guidelines for Americans, 2020–2025. United States Department of Agriculture. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf. Accessed Sept. 27, 2021.
- How much fiber do children need? Cleveland Clinic. https://health.clevelandclinic.org/figuring-dietary-fiber-child-need/. Accessed Sept. 27, 2021.
- McManus KD. Should I be eating more fiber? Harvard Health Blog. https://www.health.harvard.edu/blog/should-i-be-eating-more-fiber-2019022115927. Accessed Sept. 27, 2021.
- Whole grains, refined grains, and dietary fiber. American Heart Association. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/whole-grains-refined-grains-and-dietary-fiber#.WVVm4RMrIdU. Accessed Sept. 27, 2021.
- Chang CC, Lin YT, Lu YT, et al. Kiwifruit improves bowel function in patients with irritable bowel syndrome with constipation. Asia Pac J Clin Nutr. 2010;19:451-457.
- Chan AO, Leung G,Tong T, et al. Increasing dietary fiber intake in terms of kiwifruit improves constipation in Chinese patients. World J Gastroenterol. 2007;13:4771-4775.
- Christodoulides S, Dimidi E, Fragkos KC, et al. Systematic review with meta-analysis: effect of fibre supplementation on chronic idiopathic constipation in adults. Aliment Pharmacol Ther. 2016;44:103-116.