Kiwis, psyllium or plums: which is better for chronic constipation?

Relation

Chey SW, Chey WD, Jackson K, Eswaran S. Exploratory comparative effectiveness study of green kiwi, psyllium, or plum in US patients with chronic constipation.Am J Gastroenterol. 2021;116(6):1304-1312.

Draft

A partially randomized, comparative effectiveness study conducted in adults with chronic constipation at a US medical center

Objective

To determine the comparative effectiveness of psyllium, prunes, and kiwifruit on symptoms of chronic constipation in a US-based study population

Participant

Investigators recruited eligible patients from those who met Rome IV criteria for either functional constipation (FC) or irritable bowel syndrome with constipation (IBS-C).

Of the original 247 patients approached for study recruitment, 109 were enrolled for baseline screening and 79 patients met inclusion criteria and were randomized (69 female [87%] with a mean age of 42.7 years [range 18-76 years]).

Inclusion criteria included adults with chronic constipation (CC) in the past 3 months with symptoms occurring at least 6 months previously; 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); have ≤ 3 complete spontaneous bowel movements (CSBM) per week; and having at least 2 of the following symptoms: pressing, hard/lumpy stools, incomplete bowel movements, use of manual maneuvers for relief, and a feeling of obstruction or blockage in ≥ 25% of stools (BMs).

Exclusion criteria included any of the following: severe abdominal pain (>7 on the 1-10 scale), 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 who were allergic to the ingredients in the study.

Study intervention

Participants were enrolled in a 2-week baseline assessment phase to assess symptoms through daily questionnaires. Those who qualified were then randomized into 3 study arms for a 4-week treatment period, followed by a 2-week observation period.

1. 2 ganze grüne Kiwis täglich, geschält (Actinidia deliciosa Var. Hayward), Ballaststoffe = 6 g/Tag
2. 50 g Pflaumen (etwa 6 Pflaumen) zweimal täglich (Marke Kirkland), Ballaststoffe = 6 g/Tag
3. 6 g Flohsamen zweimal täglich, gelöst in Wasser (Marke Metamucil), Ballaststoffe = 6 g/Tag

Researchers and participants were not blinded to the assigned intervention. Because of the availability of fresh kiwifruit, researchers assigned the first 30 enrolled patients to the kiwifruit arm and computer-generated the remaining patients to the plum or psyllium arms.

Researchers instructed all participants not to eat other foods containing kiwi, psyllium, or prunes or to add high-fiber fruits/vegetables to their diet during the study.

Study parameters assessed

Patients answered daily symptom questionnaires, and researchers collected dietary assessments through 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 who reported an increase of 1 or more CSBMs per week compared to the baseline screening period for at least 2 of the 4 weeks of the intervention. The groups were not compared with each other.

Secondary outcome measures included effects on frequency, consistency, effort, and feeling of incomplete evacuation. Satisfaction and dissatisfaction with treatment were also recorded.

Key insights

For the primary endpoint of increasing BMs by at least 1 week, the proportion of responders to therapy was 45% for the Kiwi group (13/29; 95% CI [0.27–0.63]); 67% for the plum 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 the number of responders between groups, suggesting that all were equally effective in increasing the number of CSBMs.

Kiwis stood out in this study for another reason: the participants liked them the least.

When the researchers looked at the entire 4-week treatment period, the plum group had the largest average change in CSBMs (+2.1;P<0.001) followed by the psyllium group in second place (+1.4;P=0.005) and kiwi least effective (+1;P=0.0049).

For secondary endpoints, there was a significant weekly CSBM rate in all 3 treatment groups when comparing weeks 3 and 4 to baseline (P≤ 0.003). Stool consistency significantly improved with kiwis (P=0.01) and plums (P=0.049). Straining is significantly improved with kiwis (P=0.003), plums (P<0.001) and psyllium (P=0.04). Patients in the kiwi group also reported a significant decrease in bloating (P=0.02).

Practice implications

When it comes to chronic constipation, fiber is king! Ensuring adequate fiber is a critical component of a constipation treatment plan because insoluble fiber bulks stools and soluble fiber helps retain fluid in the stool, softening it and ensuring it is easily excreted. Fiber is also necessary for normal intestinal microbiota, and some intestinal flora are known to contribute to intestinal motility. The most recent Dietary Guidelines for Americans, 2020-2025, state that “over 90% of women and 97% of men do not meet the recommended daily intake of fiber.”¹A plant-based diet with an emphasis on high-fiber foods is recommended for almost all patients, and at least some patients with constipation may need to consume more fiber daily (see table below).

Table: Recommended fiber intake (in grams) by age and gender^2-4

If increasing fiber is not enough to resolve constipation, doctors generally recommend soft fruits or supplements such as flax, psyllium, or other fiber to improve bowel movements.

In this study, there were no statistically significant differences between the 3 groups in the primary outcome measure, VSBMs.

Similar to previous studies on prunes, psyllium and kiwi, all 3 active ingredients relieved constipation to some extent. The only difference is that in this study, the benefits of kiwis appeared to decrease after 2 weeks of consumption, although they remained statistically significant compared to baseline (P=0.002). This contradicts previous studies that show no decrease in effectiveness over time in kiwifruit.^5.6

A finding from this study, which has been found in previous studies on kiwifruit, is that kiwifruit is better tolerated by people with constipation, with a lower incidence of symptoms such as gas and bloating than prunes or psyllium. The authors speculate that this may be due to the sugar composition of kiwifruit, which is relatively low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) compared to plums.

Kiwis stood out in this study for another reason: the participants liked them the least. The authors reported that “for kiwi and the other groups (7% kiwi versus 17% plum and 38% psyllium,P=0.02).”

This study was interesting because the idea of ​​comparable effectiveness of these fiber supplements may not have been a prior consideration for practitioners. There are numerous studies comparing the effectiveness of supplements, but few that compare dietary sources of fiber.⁷Understanding that some sources of fiber may affect other aspects of digestion or be more easily tolerated can help physicians select the best fiber for even their most sensitive patients.

This study is informative in that it validates the use of one of these substances in 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 provides the possibility of using kiwifruit for patients who cannot tolerate psyllium or prunes.