Study may explain why IBD patients react to foods they once tolerated

A new study published in Gastroenterology could provide insight into why individuals with inflammatory bowel disease (IBD) experience adverse reactions to foods they once tolerated. IBD, which encompasses conditions like Crohn's disease and ulcerative colitis, is characterized by bouts of severe inflammation, often prompting patients to modify their diets without strong evidence that such changes alleviate symptoms. Approximately two-thirds of IBD patients report food-related symptoms, primarily dairy, wheat, and fiber.

The gut microbiota, comprising trillions of bacteria residing in the intestines, may hold the key to understanding these food reactions. These bacteria assist in the digestion of food components that human enzymes cannot process independently. Researchers from McMaster University Medical Centre, led by Dr. Alberto Caminero, have identified a novel mechanism by which gut inflammation can contribute to these food sensitivities.

Inflammation impairs the microbiota's ability to digest certain food components, potentially triggering immune responses to foods that were previously harmless.

The study utilized two mouse models of colitis to demonstrate that inflammation makes animals more susceptible to developing food sensitivities. Following inflammation, exposure to dairy or gluten led to an allergic-type immune response in the colon. When these foods were reintroduced later, they caused heightened gut sensitivity and exacerbated colitis symptoms.

The researchers found that inflammation depleted specific bacteria responsible for breaking down these food triggers. This alteration in the gut microbiota alone was sufficient to increase the risk of sensitization. Transferring gut bacteria from inflamed mice to germ-free mice made those mice more prone to sensitization to the same foods, whereas reintroducing the missing bacteria reduced these effects.

Similar patterns were observed in humans, with individuals reporting food intolerances exhibiting reduced capacity to break down common trigger foods and lower levels of bacteria capable of processing these triggers.

While gut microbiota disruption appears to be a significant factor, the researchers emphasize that this mechanism is likely part of a broader interplay involving genetics, infections, and stress, which require further investigation. The findings suggest that inflammation disrupts the gut bacteria responsible for processing certain foods, and this disruption—not the foods themselves—may initiate the immune reactions experienced by IBD patients.

In essence, gut inflammation fosters adverse food reactions by impairing the microbial metabolism of food triggers.