# Higher Dietary Phytochemical Index Is Associated With Lower Disease Activity, Inflammation, and Gut Dysbiosis in Patients With Ulcerative Colitis

## TL;DR

A diet rich in phytochemicals is linked to reduced inflammation, better gut health, and lower disease activity in ulcerative colitis patients.

## Contribution

This study is the first to show a strong association between a dietary phytochemical index and multiple clinical and microbiome outcomes in UC patients.

## Key findings

- Higher Dietary Phytochemical Index scores correlated with lower levels of inflammatory biomarkers like FCP, CRP, and IL-6.
- Patients with higher DPI scores had improved gut microbiota diversity and higher butyrate levels, indicating better gut health.
- Higher DPI was associated with better psychological health, sleep quality, and lower disease activity scores in UC patients.

## Abstract

Dietary phytochemicals possess anti‐inflammatory and antioxidant properties that may modulate disease activity in ulcerative colitis (UC). This study examined the association between the Dietary Phytochemical Index (DPI) and disease activity, biomarkers, gut microbiota, and psychological health in UC patients. In this cross‐sectional study of 350 UC patients, dietary intake was assessed using a validated FFQ to calculate the DPI. Participants were stratified into DPI quartiles. Disease activity was measured via the Mayo score. Biomarkers (FCP, CRP, IL‐6, ESR, homocysteine, zonulin), gut microbiota diversity, Firmicutes/Bacteroidetes ratio, and SCFA levels were analyzed. Psychological status and quality of life were evaluated using validated questionnaires (PHQ‐9, GAD‐7, PSQI, FSS, SIBDQ, IBD Disability Index). Participants with higher DPI scores showed significantly lower levels of FCP, CRP, IL‐6, ESR, homocysteine, and zonulin (all p < 0.001). Gut microbial richness (Shannon index) and the F/B ratio increased with higher DPI quartiles (all p < 0.001), indicating reduced inflammation (all p < 0.001). In terms of SCFAs, butyrate levels were significantly higher in Q4 (94.83 μmol/g) compared to Q1 (68.30 μmol/g, p < 0.001). In healthy adults, fecal butyrate concentrations typically range between 60 and 100 μmol/g; thus, the observed increase in Q4 reflects a clinically meaningful improvement. Q4 participants reported significantly better sleep quality, lower depression and anxiety scores, reduced fatigue and disability, and higher quality of life (all p < 0.001). The Mayo score, reflecting clinical disease activity, was significantly lower in Q4 (4.90 ± 0.83) compared to Q1 (6.18 ± 1.95, p < 0.001). Higher DPI adherence was associated with lower disease activity and improved clinical outcomes, though causal relationships cannot be inferred due to the cross‐sectional design.

A higher dietary phytochemical index was significantly associated with lower disease activity, reduced systemic and intestinal inflammation, and improved gut microbiota diversity in ulcerative colitis patients. These findings suggest that phytochemical‐rich diets may offer a supportive strategy to improve clinical outcomes and gut health in UC management.