Popular food coloring linked to intestinal inflammation, colitis: study

Recent research indicates that long-term consumption of Allura Red (AR), a commonly used synthetic paint additive, may cause inflammatory bowel disease (IBD) and colitis.

Also known as the Red 40, the AR is one of the nine synthetic color additives approved by the US Food and Drug Administration (FDA) for use in food. Manufacturers prefer synthetic dyes over natural ones obtained from animals and plants because they are cheaper, give a more vivid and uniform color and do not introduce unwanted flavors.

In a study published on December 20 in Nature Communicationsscientists from McMaster University in Canada investigated the impact of exposure to AR on gut health. Using an experimental animal model, they found that chronic consumption of the dye can cause mild intestinal inflammation in mice.

“The dye directly disrupts intestinal barrier function and increases the production of serotonin, a hormone/neurotransmitter found in the gut, which subsequently alters the composition of the gut microbiota, leading to increased susceptibility to colitis,” the researchers said in press release.

For the purpose of the study, the researchers examined the effects of several commonly used food colorings on serotonin production, including AR, Brilliant Blue FCF, Sunset Yellow FCF, and Tartrazine Yellow. Although all these dyes increased the release of serotonin, AR was found to have the most pronounced effect.

The scientists then began feeding groups of mice different diets for 12 weeks. One group was fed normal food as a control; the other was fed with AR-infused food every day; and the other received AR-infused food only one day per week. The amount of AR added to their diet was calculated according to levels considered acceptable for humans.

When colitis was induced by exposure to the chemical seven days after feeding, the researchers found that a group of mice that occasionally consumed AR—the most similar to the human model—did not become more vulnerable to colitis. However, those mice fed AR-infused food for consecutive 12 weeks developed mild colitis.

The same effects were seen in mice when AR was added to water instead of food, according to the study.

To further investigate the effect of early exposure to AR, the researchers performed another controlled experiment by feeding 4-week-old mice either standard chow or chow with AR for 14 weeks. As a result, they found that young mice exposed to AR developed mild inflammation in the colon, with less active expression of genes that regulate antimicrobial responses.

“This is particularly important since synthetic dyes are a convenient and inexpensive alternative for food manufacturers to make food even brighter and more attractive to the consumer, especially young children,” they noted in the study.

Waliul Khan, lead author of the study and a professor in McMaster’s Department of Pathology and Molecular Medicine, said these findings should alert consumers to the potential harm of food additives.

“What we found is startling and alarming, as this common synthetic food coloring is a possible dietary trigger for IBD,” Khan said. “This research is a significant advance in warning the public about the potential harm of the food coloring we consume every day.”

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

Exposure to synthetic food dyes at a young age has long been suspected to cause ADHD. According to a 2021 review by the California government.pdf) of scientific studies over the previous decade, consumption of synthetic food dyes, including AR, has caused hyperactivity and other neurobehavioral problems in at least some children.

AR is present in a wide range of foods and beverages, including cereals, dairy products, puddings, sweets, chewing gum, juice, energy drinks and confectionery.