Long-term data collected from more than 116,000 adults between 2003 and 2016 as part of the Prospective Urban Rural Epidemiology study reviewed by Canadian researchers from McMaster University found participants who consumed one to four servings per day of ultra-processed foods were 67% more likely to have IBD than those who consumed less than one serving per day of the products. The risk increased to 82% for those who had five or more servings per day.
As an observational study that relied on self-reported diagnoses and which did not account for dietary changes over time, the research cannot establish causality.
However, the researchers noted, consumption of unprocessed versions of the same base ingredient as in ultra-processed foods were not associated with an increased risk of IBD, which they say “suggests that it might not be the food itself that confers this risk, but rather the way the food is processed or ultra-processed.”
While the study could not identify with confidence what about the ultra-processed foods might explain the correlation with IBD, the researchers ruled out sodium as the culprit.
They explain, “we found no relation between urinary sodium, a surrogate for dietary sodium intake [which is often higher in ultra-processed foods than unprocessed versions] and development of IBD. This suggests that components other than sodium in ultra-processed foods might be responsible for the higher risk of IBD observed with higher consumption of salty snacks.”
The researchers further hypothesized – but did not test – specific emulsifiers and additives that are widely used in western diets and ultra-processed foods “could be a plausible pathway for disruption of gut microbiota and propagation of the subsequent immune activation that occurs in IBD.”
Specifically, they call out, carboxymethylcellulose and polysorbate 80, which mice studies suggest could induce thinning of the mucosal layer and dysbiosis to promote colitis and colitis associated colon cancer, and other additives that have been “implicated” in preclinical studies, including maltodextrin and titanium dioxide.
The study also revealed an association between higher intake of fried food and higher risk of IBD, but again the researchers did not pinpoint a cause.
Instead, they hypothesized, “this association might exist because many fried foods are also processed (eg, chicken nuggets, French fries). It could be that the action of frying and the processing of oil leads to modification of nutrients within the food. The type and quality of oil used might also be relevant.”
Despite controlling for many variables, the researchers acknowledge there could be “residual confounding” factors that were unmeasured or unknown that could compromise their findings.
With this in mind, they recommend additional research to identify specific factors of processed and ultra-processed food that might account for the observed association.