Natural antioxidant substances improve oxidative stress and alleviate ulcerative colitis: a meta-analysis of randomized controlled trials

Oxidative stress is a key driver of mucosal damage in ulcerative colitis (UC). Antioxidant supplementation may restore redox balance, but its clinical efficacy remains controversial. To evaluate the effects of natural antioxidant substances supplementation on oxidation/antioxidant biomarkers and clinical outcomes in UC patients. The databases included PubMed, Embase, Web of Science, and Cochrane Library (up to July 2025) were searched, and RCTs comparing oral antioxidants with placebo in UC were included. The primary outcomes were changes in oxidative stress markers (MDA, SOD, TAC, GPX). The secondary outcomes included the short IBD questionnaire (SIBDQ) score and the simple clinical colitis activity index (SCCAI) score. 9 articles involving 624 patients were included in this study. Compared to placebo group, antioxidant substances supplementation could significantly reduce the level of MDA (P = 0.001, SMD=-1.09, 95% CI -1.75 to -0.43), increased the levels of SOD, TAC, GPX in patients with UC (P = 0.02, SMD = 0.57, 95% CI 0.10 to 1.04; P = 0.0004, SMD = 0.74, 95% CI 0.33 to 1.16; P = 0.004, SMD = 0.69, 95% CI 0.22 to 1.16). In addition, antioxidant substances supplementation remarkably decreased the SCCAI score of UC patients (P = 0.04, SMD=-0.62, 95% CI -1.21 to -0.04), thus improving the disease activity. However, there is no significant difference in the change of IBDQ score (P = 0.13, SMD = 0.55, 95% CI -0.17 to 1.28). Natural antioxidant substances supplementation effectively enhanced antioxidant capacity and ameliorated oxidation status, improved the disease activity of UC patients, but had no significant impact on their quality of life. This study will provide a basis for the selection of adjuvant therapy drugs for UC.