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BERLIN — A recent large cohort study has revealed that adherence to a healthy plant-based diet can reduce the risk of developing inflammatory bowel disease (IBD), while an unhealthy plant-based diet may increase disease risk and lead to worse outcomes.
The study, presented at the European Crohn’s and Colitis Organisation (ECCO) 2025 Congress, analyzed both Crohn’s disease (CD) and ulcerative colitis (UC). The results suggest that diet quality plays a crucial role in not only the onset of IBD but also its progression and the likelihood of requiring surgery for individuals already diagnosed with the condition.
Diet Quality Matters
“Not all plant-based foods are equal — they don’t all have the same effect on health outcomes,” stated Dr. Judith Wellens, MD, PhD, a gastroenterology resident at Leuven University Hospital, Belgium, and lead researcher of the study.
“We need to look at what people are eating more carefully because it isn’t black and white, with all plant-based food being good and animal-based food being bad,” Wellens added. She emphasized that while plant-based diets have benefits, they must be individualized to ensure high dietary quality. Simply cutting out meat is insufficient; instead, avoiding unhealthy plant-based foods is key to lowering IBD risk.
Assessing Diet’s Impact on IBD Risk
Preclinical studies have shown that plant-based diets can beneficially alter gut microbiota. However, some diets recommended for IBD, such as the Crohn’s disease exclusion diet, include animal-based ingredients, adding complexity to dietary recommendations.
The researchers examined data from two major cohorts: the UK Biobank, which included 187,888 participants, and the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort, with 341,539 participants from eight European countries. None of the participants had IBD at baseline.
Using participant dietary recalls, the researchers developed plant-based diet indices (PDIs) to categorize diets as either healthy (including whole grains, fruits, vegetables, legumes, and vegetarian protein alternatives) or unhealthy (including emulsifiers, refined grains, fries, fruit juices, sweets, desserts, sugar-sweetened beverages, and processed foods).
The primary outcome was the incidence of IBD (either CD or UC), while the secondary outcome was IBD-related surgery, a marker of disease progression. The results were consistent across both cohorts.
In the UK Biobank cohort, 925 participants developed IBD over a median follow-up of 11.6 years. Those who adhered to a healthy PDI had a 25% reduced IBD risk, whereas those following an unhealthy PDI had a 48% increased risk. Similar trends were observed for both CD and UC.
The EPIC cohort, with a longer median follow-up of 14.5 years, showed that 548 participants developed IBD. Healthy PDIs were linked to a 29% reduced risk, while unhealthy PDIs were associated with a 54% increased risk.
Furthermore, a healthy PDI was found to halve the risk of surgery in the UK Biobank cohort, whereas an unhealthy PDI was linked to a twofold increase in surgery risk.
Genetics and Dietary Risk
The study also examined interactions between genetic predisposition and plant-based diets. Though those findings were not presented at the conference, Dr. Wellens noted that individuals with a moderate to high genetic risk for IBD based on polygenic risk scores exhibited higher odds of developing the disease.
“We don’t test people for their genetic risk of IBD, but if someone has close relatives with IBD, then their genetic risk is likely higher,” she explained.
Expert Commentary
Commenting on the findings, Professor James Lindsay, an expert in inflammatory bowel disease at Queen Mary University of London, highlighted the growing body of research showing that ultra-processed foods increase the risk of developing Crohn’s disease.
“One might assume that plant-based diets would be protective, but this study shows that plant-based diets are not all equal and there are unhealthy aspects to some,” Lindsay said.
He also cautioned that while epidemiological studies can demonstrate associations, they do not confirm causality. “Showing that a diet is associated with an outcome is not the same as knowing that changing a diet will reduce the risk. That requires a well-designed, carefully controlled trial.”
Dr. Wellens and Professor Lindsay disclosed no relevant financial conflicts of interest.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Individuals should consult a healthcare professional before making dietary changes to manage or prevent inflammatory bowel disease.
