Composition of Plant-based Diets and the Incidence and Prognosis of IBD

New Research: Composition of plant-based diets and the incidence and prognosis of inflammatory bowel disease

Background

Many proposed diets for IBD focus on increasing plant-based foods. But, it's important to note that a plant-based diet can still contain products like emulsifiers and refined grains, which are believed to negatively impact IBD incidence and progression.


What did this study look at?

  • This study investigated the association between the composition of plant-based diets and both the development and progression of IBD.

  • The researchers used data from two large cohorts: the UK Biobank (187,888 participants) and the European Prospective Investigation into Cancer and Nutrition (EPIC, 341,539 individuals).

  • They characterised diets using "Healthy Plant-based Diet Indexes (PDIs)" and "Unhealthy Plant-based Diet Indexes (PDIs).


What did the study find?
Healthy Plant-based Diets

  • Higher adherence to healthy plant-based diets was associated with a lower risk of developing IBD.

  • For individuals already diagnosed with IBD, a healthy plant-based diet was linked to a reduced need for IBD-related surgery.

Unhealthy Plant-based Diets

  • Greater adherence to unhealthy plant-based diets was associated with an increased risk of developing IBD.

  • For those with IBD, an unhealthy plant-based diet was positively associated with a higher likelihood of needing IBD-related surgery.

Other Outcomes

  • No significant associations were found between plant-based diets and the risk of cardiovascular disease, diabetes, or overall mortality.

Mediating Factors

  • The study suggested that inflammation partially mediates the link between diet and IBD. The associations might also be stronger for individuals with a moderate or high genetic risk for IBD.

Overall

  • The quality of a plant-based diet matters significantly for IBD.

  • A healthy plant-based diet appears protective against IBD development and progression, while an unhealthy plant-based diet (which may include processed plant-based foods, refined grains, and emulsifiers) is linked to adverse outcomes.

What does this mean?

  • Plant-based foods should be encouraged for all individuals with IBD. However, there is a need for specialised dietetic counselling. Simply adopting a "plant-based" label isn't enough; the overall quality of the diet, focusing on whole, unprocessed plant foods, is key to maximising benefits and avoiding potential harm.

  • Further research is needed to understand the exact mechanisms behind these effects.


Reference

Chen, J., Sun, Y., Dan, L., et al. (2025). Composition of plant-based diets and the incidence and prognosis of inflammatory bowel disease: a multinational retrospective cohort study. The Lancet Regional Health - Europe, 52, 101264. https://doi.org/10.1016/j.lanepe.2025.101264

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We are all wonderfully unique and what works for one person may not work for another so please seek help and advice before changing your diet to work out the right way forward for you.

Clemmie Macpherson