A high-fiber personalized dietary advice reduces constipation complaints in adults: a single-arm intervention study

Background: Constipation is characterized by hard stools and infrequent bowel movements, and greatly impacts quality of life (QoL). Dietary fibers can help relieve constipation, however preserving a higher fiber intake remains a challenge, and patients are often referred to fiber supplements. Therefore, we investigated the effects of a personalized dietary advice (PDA) on fiber intake and constipation complaints in adults with constipation complaints.Methods: N=25 adults with constipation complaints were included in a 4-week observation period (week 1-4) followed by a 4-week personalized intervention (week 5-8). The PDA was based on gender and habitual diet and provided high-fiber alternatives via a website. In week 1, 4 and 8, dietary intake, constipation complaints, QoL, physical activity levels and behavioral aspects were assessed. Furthermore, participants collected a fecal sample at week 1, 4 and 8 to determine microbiota diversity and composition, and short-chain fatty acids (SCFA) levels and their dynamics over time. Participants completed questions daily for 8 weeks regarding abdominal complaints, stool frequency and stool consistency. Differences over time were assessed by using mixed models. Results: Fiber intake in week 8 was significantly higher compared to week 1 (Δ=5.7±6.7g, p<.001) and week 4 (Δ=5.2±6.4g, p<.001). Constipation severity and QoL significantly improved at week 8 compared to the observation period (p<.001). Mixed model analysis over time showed that a higher fiber intake significantly reduced constipation severity (ß= -0.031 (-0.05; -0.01), p=.001) and QoL (ß= -0.022 (-0.04; -0.01), p=.009). Stool consistency improved significantly during the intervention (p=.040), but stool frequency did not. Abdominal pain reduced significantly during the intervention (p=.030), but no changes were observed for abdominal cramps or bloating. Average microbial alpha diversity and composition, and SCFA concentrations did not change over time, but indicated individual-specific dynamics. Several SCFAs were associated with constipation complaints. Subjective knowledge (p<.001) and outcome beliefs (p=.036) increased after the intervention, and the PDA was well-accepted.Conclusion: A PDA effectively increased fiber intake and subsequently reduced constipation complaints, indicating that dietary adjustments are important and feasible in the treatment of constipation complaints. Clinicaltrials.gov (NCT04457791).