Efficacy and Safety of Chia Seed Powder, Pea Protein, and Xyloglucan in Patients with Constipation-Predominant Irritable Bowel Syndrome: A Multicenter, Double-Blind, Randomized, Placebo-Controlled Trial

Background/Objectives: Natural compounds represent novel promising alternative treatments for functional gastrointestinal disorders. This multicenter, double-blind, randomized, placebo-controlled, crossover study aimed to evaluate the efficacy and safety of xyloglucan, pea protein, and chia seed powder (XP + CS) in irritable bowel syndrome with constipation (IBS-C). Methods: Sixty patients received twice-daily XP + CS or placebo for 28 days. Following a 28-day washout period, patients switched to the alternative treatment for another 28 days. Efficacy was evaluated using the Bristol Stool Form Scale; a seven-point Likert scale for abdominal pain, bloating, and discomfort; a Visual Analogue Scale for IBS symptom severity; the quality of life (QoL)-IBS questionnaire; Sickness Impact Profile (SIP) score; and serum zonulin concentrations. Adverse events were monitored throughout the study. Results: Compared to the placebo, XP + CS significantly improved stool consistency (p = 0.04 and p < 0.001 at days 15 and 28, respectively), IBS symptoms (p < 0.001 at day 15), QoL (p < 0.001 from day 15 on), and nearly all SIP domains (p < 0.001 at all time-points). Additionally, XP + CS treatment restored serum zonulin concentrations to within normal ranges by day 15. No serious adverse events were reported. Conclusions: This study provides evidence supporting the efficacy and safety of XP + CS in managing IBS-C symptoms.