Dietary intake of phytochemicals in association with irritable bowel syndrome in adults.

BACKGROUND & AIM: There is limited data regarding the association between phytochemical-rich diets and irritable bowel syndrome (IBS). The current study aimed to cross-sectionally evaluate the association of dietary phytochemical index (DPI) with the odds and severity of IBS. METHODS: In this study, which included 3362 Iranian healthcare staffs, a dish-based semi-quantitative food frequency questionnaire (DS-FFQ) was utilized to collect dietary information. The DPI was defined as the daily percentage of calories consumed from phytochemical-rich foods. The IBS assessment was performed using a revised Iranian version of the Rome III questionnaire. We applied the restricted cubic spline (RCS) to detect the possible non-linear dependency of the relationship between DPI and the odds of IBS. RESULTS: The mean age, Body Mass Index (BMI), and DPI scores of the participants were 36.29 ± 7.8 years, 24.90 ± 3.8 kg/m2, and 16.07 ± 9.01, respectively. After adjusting for possible confounders, no significant association was observed between DPI and odds of IBS in the whole study population or in gender- and BMI-stratified analyses. We found a significant inverse association between DPI and IBS severity in the study population (OR: 0.70; 95% CI: 0.51-0.98). Concerning gender, such an association was only found in women (OR: 0.65; 95% CI: 0.44-0.96). However, there was no significant relationship between DPI and IBS severity in BMI subgroups. In addition, we found no meaningful relationship between DPI and IBS subtypes. The RCS model showed that there is no non-linear relationship between DPI classification and IBS (non-linear test, χ2 = 1.14, Pnon-linearity = 0.513). CONCLUSIONS: Higher phytochemical intake was associated with reduced IBS severity, particularly in women. Further prospective studies are required to confirm these findings.