Ultra-processed grains & IBD

September 29, 2025

Issue 19

Clinical Question

Is ultra-processed grain consumption associated with increased risk of developing inflammatory bowel disease?

Editor’s Bottom Line

These important prospective data add to growing evidence that diet and lifestyle strongly influence the risk of developing inflammatory bowel disease. Understanding mechanisms for such associations is an important research priority.

Reference

Narula N, Wong ECL, Mente A, et al. Ultra-Processed Grains and Risk of Inflammatory Bowel Disease: Results from the Prospective Urban Rural Epidemiology (PURE) Study. Am J Gastroenterol. Epub ahead of print Aug 4, 2025. https://journals.lww.com/ajg/abstract.aspx

Synopsis

This multinational prospective cohort study examined the association between ultra-processed grain consumption and incident IBD using data from 124,590 participants across 21 countries in the Prospective Urban Rural Epidemiology (PURE) study. Participants, who were aged 35–70 years at baseline, completed validated country-specific food frequency questionnaires documenting intake of ultra-processed grains, defined as grains that have been chemically modified or refined and contain artificial additives such as flavorings, sweeteners, stabilizers, emulsifiers, thickeners and preservatives. Examples included packaged breads and cereal products.

Participants were categorized into three intake groups: those who consumed less than 19 g/day, 19 to less than 50 g/day and 50 g/day or more of ultra-processed grains.

During a median follow-up of 12.9 years (Interquartile Range: 11.7–15 years), 605 participants developed IBD, including 497 cases of ulcerative colitis (UC) and 108 cases of Crohn’s disease (CD). After multivariate adjustment for a range of known risk factors, participants consuming 19 g/day or more of ultra-processed grains were found to have an 86% higher risk of developing IBD compared to those consuming less than 9 g/day (Hazard Ratio [HR]: 1.86, 95% Confidence Interval [CI]: 1.26–2.61, ptrend=0.0003).

When they examined dose-response relationships using only the three intake categories, researchers found participants consuming 50 g/day or more of ultra-processed grains had more than double the risk of IBD compared to those consuming less than 19 g/day (HR: 2.08, 95% CI: 1.68–2.58, ptrend<0.0001), while those consuming 19 to less than 50 g/day showed an intermediate increase in IBD risk (HR: 1.37, 95% CI: 1.06–1.77).

The association was primarily driven by UC risk (HR: 2.46, 95% CI: 1.93–3.14 for highest versus lowest intake category, ptrend<0.0001), with no significant association observed for CD after adjustment for confounding variables. Packaged bread specifically showed strong associations with IBD risk, with participants consuming 30 g/day or greater demonstrating more than double the risk compared to those with zero intake (HR: 2.11, 95% CI: 1.65–2.70, ptrend<0.0001).

In contrast, consumption of minimally processed grains showed protective associations. Fresh bread intake of 65 g/day or greater was associated with a 39% reduced IBD risk (HR: 0.61, 95% CI: 0.45–0.84, ptrend<0.0001), and consumption of one or more servings of rice per day also was linked to a lower risk of IBD (HR: 0.63, 95% CI: 0.44–0.91, ptrend=0.0236).

The study also updated previous analyses on total ultra-processed food intake showing that participants consuming five or more servings per day of ultra-processed foods had nearly four times the risk of developing IBD compared to those consuming less than one serving per day (HR: 3.95, 95% CI: 2.74–5.71, ptrend<0.0001). Unlike the previous PURE analysis, which found significant associations primarily with CD, the current study with extended follow-up and increased case numbers demonstrated robust associations for both UC and CD.

The authors proposed several potential mechanisms for these associations, including disruption of gut microbiota by emulsifiers like carboxymethylcellulose, increased intestinal permeability from additives such as aluminum and titanium dioxide and pro-inflammatory effects of maltodextrin, all of which are commonly found in packaged breads and cereals.

Details

Study Design: Prospective cohort study
Funding: Population Health Research Institute, Hamilton Health Sciences Research Institute, Canadian Institutes of Health Research, Heart and Stroke Foundation of Ontario, with unrestricted grants from pharmaceutical companies and various national organizations in participating countries.
Allocation: Not applicable
Setting: International multicenter
Level of Evidence: 2b