Popular Food Dye Linked to Intestinal Inflammation, Colitis: Study

In this file photo taken in 2009, Gummi Bears are displayed in a glass jar at a candy store in San Francisco, California. Justin Sullivan/Getty Images

Recent research shows that long-term consumption of Allura Red (AR), a commonly used synthetic color additive, could trigger inflammatory bowel diseases (IBDs) and colitis.

Also known as Red 40, AR is one of the nine synthetic color additives approved by the U.S. Food and Drug Administration (FDA) for use in food. Manufacturers prefer synthetic dyes over natural ones extracted from animals and plants because they cost less, provide a more vivid and uniform color, and don’t introduce unwanted flavors.

In a study published on Dec. 20 in Nature Communications, scientists at 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 colorant could cause mild intestinal inflammation in mice.

“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,” the scientists said in a press release.

For the study, the scientists examined the effects of several most widely used food dyes on serotonin production, including AR, Brilliant Blue FCF, Sunset Yellow FCF, and Tartrazine Yellow. While these dyes had all promoted serotonin secretion, AR was found to have the most pronounced effect.

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

When colitis was induced via exposure to a chemical seven days after the feeding, scientists found the group of mice that occasionally consumed AR—most similar to the pattern in humans—didn’t become more vulnerable to colitis. Those mice that ate AR-infused food for a consecutive 12 weeks, however, developed mild colitis.

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

To further investigate the effect of early exposure to AR, the scientists performed another controlled experiment by feeding 4-week-old mice with either standard or AR-infused food for 14 weeks. As a result, they found that AR-exposed young mice developed mild inflammation in their colons, with genes regulating antimicrobial responses less actively expressed.

“This is particularly important since synthetic colorants are a convenient and low-cost alternative for food manufacturers to make foods even brighter and more appealing to the customer, particularly young children,” they noted in the study.

Waliul Khan, the study’s leading author and professor at McMaster’s Department of Pathology and Molecular Medicine, said these findings should alert consumers to the potential harms of food additives.

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

“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,” he added.

It has long been suspected that exposure to synthetic food dyes at a young age can cause ADHD. According to the California government’s 2021 review (pdf) of scientific studies over the preceding decade, consumption of synthetic food dyes, including AR, did cause hyperactivity and other neurobehavioral issues for at least some children.

AR is present in a wide range of foods and beverages, including cereals, dairy products, pudding, candy, chewing gums, soda, energy drinks, and confections.