BackgroundConstipation-predominant irritable bowel syndrome (IBS-C) mainly affects females, and dietary interventions for symptom relief often yield poor results because of low patient adherence. The development of functional food products enriched with dietary fibers may increase patients’ adherence to a healthy diet and relieve IBS-С symptoms. ObjectiveThis proof-of-concept, open-label, randomized controlled pilot study is aimed to evaluate the efficacy of kombucha enriched with inulin and vitamins in females with IBS-C. MethodsForty females with IBS-C were randomly assigned to receive either 220 mL of kombucha enriched with inulin (2.53 g/220 mL) and vitamins (B1 – 0.59 mg, B2 – 0.55 mg, B3 – 5.9 mg, B6 – 0.7 mg, and folic acid – 81.4 μg/220 mL) or water for 10 d. Stool frequency, Bristol stool scale score (BSSS), and abdominal symptoms were evaluated using a 5-point Likert scale on days 5, 9 and 14 of the study. The palatability of the drink was assessed using a visual analog scale. ResultsAfter 10 d, the kombucha group showed a significant increase in stool frequency (0.60 ± 0.31–0.85 ± 0.19 times/d; P = 0.004) compared with the control (0.63 ± 0.33 compared with 0.72 ± 0.28; P = 0.6). The mean values of the BSSS increased in the kombucha group (3.0 ± 1.2–4.4 ± 1.0; P = 0.001), whereas they remained unchanged in the control (2.9 ± 1.2 compared with 3.4 ± 1.2; P = 0.6). The kombucha group also experienced a significant decrease in the feeling of incomplete bowel emptying (1.88 ± 0.78 compared with 1.41 ± 0.56 points; P = 0.015), which was not observed in the control group. ConclusionsShort-term consumption of kombucha enriched with inulin and vitamins was associated with an increase in stool frequency, an improvement in the BSSS, and a reduction in the feeling of incomplete bowel emptying in females with IBS-C. Further large-scale clinical trials investigating the efficacy of kombucha enriched with inulin and vitamins in patients with IBS-C are warranted to prove the observed effects. Trial registration numberThis trial was registered at clinicaltrials.gov as NCT05164861 (==https://clinicaltrials.gov/study/NCT05164861?term=NCT05164861&rank=1; registered on 18 December, 2021).