Long-term consumption of Allura Red food dye can be a potential trigger of inflammatory bowel diseases (IBDs), Crohn’s disease and ulcerative colitis, says McMaster researcher Waliul Khan, using experimental animal models of IBD.

Researchers found that continual exposure to Allura Red AC harms gut health and promotes inflammation. The dye directly disrupts gut barrier function and increases the production of serotonin, a hormone/neurotransmitter found in the gut, which subsequently alters gut microbiota composition, leading to increased susceptibility to colitis.

Allura Red, also called FD&C Red 40 and Food Red 17, is a common ingredient in candies, soft drinks, dairy products and some cereals, Khan said. The dye is used to add colour and texture to foods, often to attract children.

The use of synthetic food dyes such as Allura Red has increased significantly over the last several decades, but there has been relatively little study of their effects on gut health before now.

“This study demonstrates significant harmful effects of Allura Red on gut health and identifies gut serotonin as a critical factor mediating these effects. These findings have important implication in the prevention and management of gut inflammation,” said Khan, the study’s senior author, a professor in the department of Pathology and Molecular Medicine and a principal investigator of Farncombe Family Digestive Health Research Institute in the Faculty of Health Sciences.

“What we have found is striking and alarming, as this common synthetic food dye is a possible dietary trigger for IBDs. This research is a significant advance in alerting the public on the potential harms of food dyes that we consume daily,” he said.

“The literature suggests that the consumption of Allura Red also affects certain allergies, immune disorders and behavioural problems in children, such as attention deficit hyperactivity disorder.”

IBDs are serious chronic inflammatory conditions of the human bowel that affect millions of people worldwide, Khan said.

While their exact causes are still not fully understood, studies have shown that dysregulated immune responses, genetic factors, gut microbiota imbalances, and environmental factors can trigger these conditions.

In recent years there has been significant progress in identifying susceptibility genes and understanding the role of the immune system and host microbiota in the pathogenesis of IBDs. However, similar advances in defining environmental risk factors have lagged, he said.

Environmental triggers for IBDs include the typical Western diet, which includes processed fats, red and processed meats, sugar and a lack of fibre, Khan said. The Western diet and processed foods also contain large amounts of various additives and dyes, he added.

The study suggests a link between a commonly used food dye and IBDs and warrants further exploration between food dyes and IBDs at experimental, epidemiological and clinical levels, Khan said.

Khan and his team published their findings in Nature Communications. Yun Han (Eric) Kwon, who recently completed PhD in Khan’s laboratory, is first author.

The study was funded by the Canadian Institutes of Health Research.