New Australian research is raising questions over the safety of a common food additive after mouse studies found titanium dioxide can induce gut microbiome changes associated with the development of several diseases, including colorectal cancer and inflammatory bowel disease.
Titanium dioxide, commonly known as E171, is a frequently used food additive. Often used to whiten food, the compound can be found in everything from mayonnaise and soy milk to chewing gum. Although many studies, and several decades of use, have concluded the chemical to be safe in humans, a small, but growing, body of researchers is beginning to question that safety profile.
This new study focused on the effects of titanium dioxide on the gut microbiome. Interestingly, the mouse studies revealed titanium dioxide did not directly alter gut bacteria populations but instead influenced the expression of certain genes that control the activity of the intestinal mucus layer. Alongside this it seemed the titanium dioxide promoted the production of bacterial biofilms in the intestine, aggregations of which have been associated with the onset of inflammatory bowel disease.
"This study investigated effects of titanium dioxide on gut health in mice and found that titanium dioxide did not change the composition of gut microbiota, but instead it affected bacteria activity and promoted their growth in a form of undesired biofilm," says Laurence Macia, co-lead author on the new research. "Biofilms are bacteria that stick together and the formation of biofilm has been reported in diseases such as colorectal cancer."
The study suggests these microbiome alterations can be associated with increased colonic inflammation and impaired gut homeostasis, although the researchers do not draw a direct line between ingestion of titanium dioxide and any specific disease in humans. In fact, the researchers do note that they are not calling for a specific ban on this food additive, but instead are asking for better regulation, and more research into the impacts of nanoparticle food additives.
"The aim of this research is to stimulate discussions on new standards and regulations to ensure safe use of nanoparticles in Australia and globally," says Wojciech Chrzanowski, co-lead author.
On the topic of titanium dioxide and its safety, scientists are still divided. A large study by a French research organization concluded in 2017 that titanium dioxide does play a role in the early stages of colorectal cancer, and can cross the intestinal barrier to enter the bloodstream. This research led to the French government to ultimately ban the food additive from the beginning of 2020.
On the other hand, both the European Food Safety Authority and French Agency for Food, Environmental and Occupational Health and Safety have released statements claiming, while titanium dioxide exposure in humans should be limited wherever possible, there is no clear evidence, "to confirm or refute the potential carcinogenesis-promoting effect of E171".
At this point the evidence simply isn't clear either way, however, in the case of titanium dioxide, the food additive simply may not be worth the risk. In 2015, following pressure from a public advocacy group, Dunkin' Donuts announced it would remove titanium dioxide from all its products saying it could easily reformulate its recipe to generate the same product without titanium dioxide. As the additive is primarily simply used to add visual appeal to a product it proved a straightforward change for the company.
The new research was published in the journal Frontiers in Nutrition.