A meta-analysis involving 2,043,601 participants identified dietary patterns significantly associated with the risk of Crohn’s disease, with no consistent dietary links observed for ulcerative colitis.
The analysis included 72 prospective cohort studies published from 2008 to 2025 and examined the long-term impact of diet on inflammatory bowel disease (IBD).
Across 65 adult cohort studies, 1,902 participants developed Crohn’s disease and 4,617 developed ulcerative colitis (UC) during a mean follow-up of 12.8 years. The mean age at recruitment was 53.1 years, and 62.3% of participants were women.
Inflammatory and ultra-processed diets were linked to higher Crohn’s disease risk. The pooled adjusted hazard ratio (aHR) for inflammatory diets was 1.63 (95% confidence interval [CI], 1.26–2.11), and for ultra-processed food intake, the aHR was 1.71 (95% CI, 1.36–2.14).
Conversely, several dietary patterns were associated with reduced Crohn’s disease risk. High fiber intake showed an aHR of 0.53 (95% CI, 0.41–0.70). Mediterranean diets were associated with lower risk (aHR, 0.59; 95% CI, 0.43–0.81). Healthy dietary indexes, including the Healthy Eating Index and Healthful Plant-Based Diet Index, showed protective effects with aHRs ranging from 0.61 (95% CI, 0.46–0.80) to 0.70 (95% CI, 0.54–0.91). Unprocessed or minimally processed foods were also protective (aHR, 0.71; 95% CI, 0.53–0.94).
No consistent associations were found between UC and any specific dietary pattern or food group. Red meat, fish, dairy, sweetened beverages, fruits, vegetables, and fats did not show significant associations with UC risk in pooled analyses.
Dietary data across studies were collected using validated food-frequency questionnaires administered before any IBD diagnosis. Sensitivity analyses were performed to reduce the likelihood of reverse causality by increasing the interval between dietary assessment and diagnosis.
Dose-response relationships further supported the findings. Significant p-trend values were reported for fiber (p = .003), Mediterranean diet (p = .03), inflammatory diet (p = .001), healthy dietary indices (p < .01), ultra-processed foods (p < .001), and unprocessed foods (p = .004).
Sub-analyses of maternal and early-life diets found that high dietary quality at age 1 was associated with reduced risk of IBD, while high fish intake at ages 1 and 3 was specifically linked to a lower risk of UC. Greater maternal diet diversity during pregnancy was also linked to lower risks of Crohn’s disease or UC in offspring in some studies.
Most diagnoses were physician-confirmed or based on ICD codes. The authors noted that the strength of associations for diet and Crohn’s disease is comparable to known risk factors such as smoking.
The findings may help inform the design of future dietary prevention trials targeting Crohn’s disease.
Full disclosures can be found in the published study.
Source: eClinicalMedicine
