The quality of a plant-based diet may influence the risk and progression of inflammatory bowel disease and related complications, according to recent multinational cohort study results.

In the study, published in The Lancet Regional Health–Europe, investigators analyzed data from over 529,000 participants in the UK Biobank and European Prospective Investigation into Cancer and Nutrition (EPIC) cohorts.

They found that a diet high in whole plant-based foods lowered the risk of inflammatory bowel disease (IBD), whereas a diet high in processed plant-based foods increased the risk of the disease. Over a median follow-up of 11.6 years (UK Biobank) and 14.5 years (EPIC), the investigators identified 1,473 IBD cases. Higher adherence to a healthy plant-based diet correlated with a 25% lower IBD risk (hazard ratio [HR] = 0.75, 95% confidence interval [CI] = 0.60–0.94 in UK Biobank; HR = 0.71, 95% CI = 0.59–0.85 in EPIC). In contrast, an unhealthy plant-based diet increased the risk (HR = 1.48, 95% CI = 1.21–1.82 in UK Biobank; HR = 1.54, 95% CI = 1.30–1.84 in EPIC).

Among 2,133 patients with IBD in the UK Biobank, diet quality also influenced disease outcomes. A healthy diet was linked to a 50% lower risk of IBD-related surgery (HR = 0.50, 95% CI = 0.30–0.83), whereas an unhealthy diet more than doubled the risk (HR = 2.12, 95% CI = 1.30–3.44). Genetic analysis suggested the protective effects of a healthy diet were stronger in patients with a moderate or high genetic risk for IBD, with inflammatory markers such as C-reactive protein and INFLA-score mediating up to 22% of associations.

"Not all plant-based diets are equal," said lead study author Jie Chen, of the Department of Gastroenterology at the Third Xiangya Hospital in China, and colleagues. "Clinically, this underscores the need for specialized dietetic counseling to ensure the overall quality of the diet in IBD management, while future research efforts should focus on determining the different aspects within plant-based foods that explain this dichotomy to ensure healthy food in a sustainable environment," they added.

While the study provided strong evidence, the investigators acknowledged limitations, including its observational nature, reliance on dietary recall, and potential residual confounding. Nonetheless, the findings underscored the importance of dietary quality in IBD prevention and management, reinforcing the need for clinical guidance to differentiate between beneficial whole-food, plant-based diets and processed plant-derived foods.

Full disclosures are available in the published study.