Food Dyes may Trigger Colitis, IBD in Some People: Study

A growing number of scientists now recognize that the increased consumption of processed foods and food additives like synthetic food dyes in the human diet in recent years correlate with an increase in the incidence of illnesses–including inflammatory and autoimmune diseases.  Now one team of scientists have examined the role that synthetic food dyes in particular may play in illnesses like inflammatory bowel disease (IBD).  The results from recent scientific research from the Icahn School of Medicine at Mount Sinai suggest that certain artificial food dyes can cause inflammatory bowel disease (IBD)* when the immune system has become dysregulated. More specifically, the study found that mice with dysregulated expression of the immune system cytokine IL-23 developed colitis when they consumed food with the artificial food colorants Red 40 and Yellow 6**. Development of colitis in the animals also required the presence of commensal bacteria that could metabolize the food dyes. The scientists say the study is the first to show this phenomenon. Future studies are needed to definitively demonstrate that these food colorants have similar effects in humans.

“The dramatic changes in the concentration of air and water pollutants and the increased use of processed foods and food additives in the human diet in the last century correlate with an increase in the incidence of inflammatory and autoimmune diseases. These environmental changes are thought to contribute to development of these diseases, but relatively little is known about how they do so. We hope this research is a step toward understanding the impact of food colorants on human health.”

-Sergio Lira, MD, PhD, the Leona M. and Harry B. Helmsley Charitable Trust Professor of Immunology at the Precision Immunology Institute at Icahn Mount Sinai

Study overview

The researchers created different mouse models that conditionally expressed IL-23, or in which IL-23 expression was augmented. To their surprise, they found that mice with the dysregulated immune response did not develop inflammatory bowel disease spontaneously, even though dysregulated IL-23 is a factor in people with the disease. However, when given a diet containing the food dyes Red 40 or Yellow 6, the animals did develop colitis. Conversely, control mice with a normal immune system did not develop IBD when given the food dye-infused diet.

To prove that the food colorant was responsible for the development of IBD in the mice with dysregulated immune systems, the researchers fed the animals diets without the food colorant, but gave them water that did contain it. The disease developed when the mice consumed the colorant, but not otherwise. The researchers replicated the finding across several diets and several food colorants.

“We show here that Red 40 alone does not induce colitis in control mice, but it can trigger severe IBD-like colitis in IL-23-overexpressing mice.”

Interestingly, induction of colitis was dependent on the presence of commensal bacteria that metabolized Red 40 and Yellow 6, to produce a metabolite, 1-amino-naphthol-6-sulfonate sodium salt. “Our studies reveal that food colorants contribute to development of colitis in conditions characterized by increased IL-23 signaling…additionally, disease development in this setting requires commensal bacteria, such as E. faecalis and B. ovatus, to metabolize Red 40 or Yellow 6.”



“Our findings suggest that specific food colorants are risk factors for experimental IBD in conditions of immune dysregulation … In our study we show that the azo dyes Red 40 and Yellow 6, the most abundant food colorants in the world, can trigger an IBD-like colitis in mice conditionally expressing IL-23…These results may have implications for human health as IL-23 is clearly implicated in development of IBD, and consumption of food colorants such as Red 40 and Yellow 6, is widespread.”



*According to the study authors, both genetic predisposition and environmental factors are thought to play a role in IBD development, but while more than 200 loci and genes have been linked with IBD in humans, the environmental factors contributing to disease have remained elusive. In particular, genetic studies in humans have linked the interleukin (IL)-23 signaling pathway with IBD. In fact, IL-23 is one of the best-studied immune factors contributing to development of IBD, and IL-23 dysregulation is known to be a factor in the development of the condition in humans.

**Red 40 (also known as Allura Red AC), and Yellow 6, are the most widely used synthetic food dyes in the world, and are found in many foods, beverages and medicines.

Journal reference: He, Z., et al.  Food colorants metabolized by commensal bacteria promote colitis in mice with dysregulated expression of interleukin-23, Cell Metabolism Journal, May, 2021,

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