A commonly used red food coloring has been found to promote gut inflammation in mice, according to new research from scientists at McMaster University. The study suggests chronic consumption of the food dye may increase susceptibility to inflammatory bowel diseases such as Crohn's and colitis.
The new research focused on a group of food coloring compounds known as azo dyes. While most azo dyes are generally considered to be safe and non-toxic, a few studies have indicated some types of azo dyes may exert pro-inflammatory properties in animals. So a team of scientists set out to better understand the potential for azo dyes to contribute to the development of inflammatory bowel disease (IBD).
The hypothesis driving the research was that azo dyes were promoting the secretion of serotonin in the gut, a hormone known to exacerbate the development of intestinal inflammation. The first step was to screen several azo dyes for their potential influence on serotonin secretion using human cell cultures.
Four of the most popular azo dyes used as food colorings were chosen: Allura Red AC (also known as FD&C Red 40 or E129), Brilliant Blue FCF, Sunset Yellow FCF, and Tartrazine Yellow. Of those, Allura Red turned out to have the most pronounced effect on serotonin secretion, leading the researchers to focus on it specifically in further animal tests.
Mice engineered to develop colitis were fed either a normal diet, or a diet supplemented with Allura Red (AR), for 12 weeks. The amount of food dye fed to the animals was calculated relative to the acceptable daily safe intake known for humans.
After 12 weeks the mice chronically exposed to AR had developed mild colitis. Gut levels of serotonin were also elevated indicating this mechanism is likely the driving force behind the increased inflammation.
The findings come with plenty of caveats that are important to understand. First, intermittent exposure to AR was not seen to induce colitis in the mice. Only chronic daily consumption for weeks led to the intestinal inflammation.
Secondly, exposure to AR did not increase susceptibility to colitis in mice not already engineered to develop the condition. This means the food additive may only be a trigger for inflammatory bowel disease in subjects with a predisposition to the condition, either through genetic or lifestyle factors.
Nevertheless, senior author on the study Waliul Khan said the findings are "striking and alarming." According to Khan, inflammatory bowel disease is caused by a number of different genetic, lifestyle and environmental factors coalescing, and it's plausible to suspect these food additives to be a relevant trigger in some people.
"This study demonstrates significant harmful effects of Allura Red on gut health and identifies gut serotonin as a critical factor mediating these effects," said Khan. "These findings have important implication in the prevention and management of gut inflammation."
The researchers do stress these findings have not been verified in humans, so at this stage the association is still speculative. However, the study does call for more investigation into the relationship between IBD and synthetic food colorants, particularly in relation to children's foods.
"Our findings that the exposure of AR during early life primes mice to the heightened susceptibility to DSS-induced colitis support the notion that early life is increasingly considered as a crucial period that influences susceptibility to IBD development in later life," the researchers write in the study. "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. As food colorants are prevalent in many foods commonly consumed by children, they may have greater exposure than adults."
The new study was published in Nature Communications.
Source: McMaster University