Titanium dioxide (TiO2) has become an increasingly popular additive for the food industry – E171, a white food colouring, is used in icing, chewing gum and marshmallows. It’s also found in chocolate and doughnuts.
Campaigners, as well as the French food safety agency ANSES, have raised concerns about widespread use of the nanoparticle and called for more research. As yet, the European Food Safety Authority (EFSA) has imposed no restrictions on the use of TiO2 in the food industry.
Not all TiO2 in use is in the engineered nanoparticle form, but the smaller particles are thought to behave differently when ingested.
Now, researchers at the University of Zurich have warned that “patients with an intestinal barrier dysfunction as found in colitis should abstain from foods containing titanium dioxide".
Professor Gerhard Rogler and his team first studied the effect of inorganic TiO2 particles in cell cultures. They were able to show that TiO2 can penetrate human intestinal epithelial cells and macrophages and accumulate there.
The nanoparticles were detected as danger signals by inflammasomes (receptors and sensors involved in the immune system), which triggered the production of inflammatory messengers.
In addition, patients with ulcerative colitis, whose intestinal barrier is disrupted, have an increased concentration of TiO2 in their blood. "This shows that these particles can be absorbed from food under certain disease conditions," Professor Rogler explained.
The scientists also orally administered TiO2 nanoparticles to mice, which serve as a disease model for inflammatory bowel disease. And once again the particles activated the NLRP3 protein complex (an inflammasome), which led to “strong intestinal inflammation and greater damage to the intestinal mucosa in the mice”. Crystals of TiO2 also accumulated in the animals' spleens.
Time to test TiO2?
Inflammatory bowel disease, like Crohn's disease and ulcerative colitis, have been on the rise in many Western countries for decades. Genetic and environmental factors – such as nutrition – play a role in the development of the illnesses.
Professor Rogler said that further studies are needed in humans but those with colitis should avoid food with TiO2. This isn’t easy, given its widespread use in a range of foods nowadays.
In February, scientists in the US noted that ingestion of the nanoparticle is “nearly unavoidable”. The researchers highlighted some of the “subtle effects” from consumption of TiO2, including an increase in inflammatory signals and a fall in enzyme activity.
EFSA has said that TiO2 poses no health concerns at current exposure levels, but a lack of data has prevented it from setting an acceptable daily intake (ADI).
Campaigners remain concerned, however. Last year French environmental NGO Agir pour l’Environnment found undeclared titanium dioxide particles in three products, including chocolate biscuits and bubble gum.
"Titanium dioxide nanoparticles exacerbate DSS-induced colitis: role of the NLRP3 inflammasome."
Published online ahead of print, July 2017, DOI:10.1136/gutjnl-2015-310297
Authors: Pedro A Ruiz, Belen Morón, Helen M Becker, Silvia Lang, Kirstin Atrott, Marianne R Spalinger, Michael Scharl, Kacper A Wojtal, Anne Fischbeck-Terhalle, Isabelle Frey-Wagner, Martin Hausmann, Thomas Kraemer, Gerhard Rogler.