Individuals who consumed more ultraprocessed foods had a significantly increased risk of developing inflammatory bowel disease (IBD) than those who consumed less, according to data from more than 100,000 adults.
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“Diet alters the microbiome and modifies the intestinal immune response and so could play a role in the pathogenesis of IBD,” Neeraj Narula, MD, of McMaster University, Hamilton, Ont., and colleagues wrote. Although previous studies have investigated the impact of dietary risk factors on IBD, an association with ultraprocessed foods (defined as foods containing additives and preservatives) in particular has not been examined, they wrote.
In a study published in BMJ, the researchers examined data from 116,087 adults aged 35-70 years from 21 countries between 2003 and 2016 who were part of the large Prospective Urban Rural Epidemiology (PURE) Cohort. Participants completed baseline food frequency questionnaires and were followed at least every 3 years; the median follow-up time was 9.7 years. The primary outcome was the development of Crohn’s disease or ulcerative colitis. In this study, ultraprocessed food included all packaged and formulated foods and beverages that contained food additives, artificial flavors or colors, or other chemical ingredients.
The categories of ultraprocessed foods included processed meat, cold breakfast cereal, various sauces, soft drinks, and fruit drinks, and refined sweetened foods such as candy, chocolate, jam, jelly, and brownies.
Overall, 467 participants developed IBD, including 90 with Crohn’s disease and 377 with ulcerative colitis.
After controlling for confounding factors, the investigators found that increased consumption of ultraprocessed foods was significantly associated with an increased risk of incident IBD. Compared with individuals who consumed less than 1 serving per day of ultraprocessed foods, the hazard ratio was 1.82 for those who consumed 5 or more servings and 1.67 for those who consumed 1-4 servings daily (P = .006).
“The pattern of increased ultraprocessed food intake and higher risk of IBD persisted within each of the regions examined, and effect estimates were generally similar, with overlapping confidence intervals and no significant heterogeneity,” the researchers noted.
The risk of IBD increased among individuals who consumed 1 serving per week or more of processed meat, compared with those who consumed less than 1 serving per week, and the risk increased with the amount consumed (HR, 2.07 for 1 or more servings per day). Similarly, IBD risk was higher among individuals who consumed 100 g/day or more of refined sweetened foods compared with no intake of these foods (HR, 2.58).
Individuals who consumed at least one serving of fried foods per day had the highest risk of IBD (HR, 3.02), the researchers noted. The reason for the association is uncertain, but may occur not only because many fried foods are also processed but also because the action of frying food and the processing of oil, as well as type and quality of oil, might modify the nutrients.
In the subgroup analysis, higher consumption of salty snacks and soft drinks also was associated with higher risk for IBD. However, the researchers found no association between increased risk of IBD and consumption of white meat, unprocessed red meat, dairy, starchy foods, and fruit/vegetables/legumes.
The study findings were limited by several factors including the relatively small number of individuals with Crohn’s disease, potential lack of generalizability to those who develop IBD in childhood or young adulthood, and possible confounding from unmeasured variables. The study also did not account for dietary changes over time, the investigators reported. However, the longitudinal design allowed them “to focus on people with incident IBD and to use medical record review and central adjudication to validate a sample of the diagnoses.”
The results suggest that the way food is processed or ultraprocessed, rather than the food itself, may be what confers the risk for IBD, given the lack of association between IBD and other food categories such as unprocessed red meat and dairy, the researchers concluded.