this randomized double blind clinical trial designed to evaluate efficacy of Black seed (Nigella sativa) extract and its active component thymoquinone for management of Irritable bowel syndrome (IBS) as one of the most common functional gastrointestinal disorders.

This control randomized clinical trial conducted on patients with diagnose of IBS based on ROME-IV criteria referred to the gastrointestinal outpatient clinics of 3 referral centers during 2021. IBS patients were randomly divided into two groups to receive either capsules containing 100 mg black seed extract PO BID (case group; n=32) or same capsules containing placebo (control group; n=30) 2 times a day, along with their routine treatments for 8 weeks. The patients followed up every two weeks and their symptoms recorded. The symptoms severity was evaluated based on IBS severity score (pain severity, abdominal pain severity, abdominal distension severity, satisfaction with bowel habit and the effect IBS on general life).

Overall, 62 IBS patients included. There was no significant difference between two groups in the severity of IBS symptoms before the intervention, and at the second and fourth weeks of treatment (P>0.05). However, in the sixth (P=0.004) and eighth weeks of treatment (P=0.018), the severity of the disease in black seed group was significantly lower than placebo group. The average scores of abdominal pain severity from the sixth weeks onwards, and the scores of abdominal distension severity, satisfaction with bowel habits, the impact of IBS on daily life and the overall score of the IBS severity questionnaire from the fourth weeks onwards in black seed group were significantly lower than placebo group (P<0.05).

This study showed that Black seed extract supplementation is safe and effective for improving all of the IBS symptoms and severity. Considering its low cost and availability, Black seed administration could be a therapeutic option among patients with IBS.