I don't see the scientific evidence in the literature that would cause people any concern, said Kaminski.

Scientists analyzed research that examined how titanium dioxide nanoparticles interact with the brain for a 2015 review published in Nanoscale Research Letters. The researchers wrote: “Once the TiO2 NPs are translocated into the central nervous system through [certain] pathways, they may accumulate in the brain regions. For their slow elimination rates, those NPs could remain in the brain zones for a long period, and the Ti contents would gradually increase with repeated exposure.” After reviewing dozens of studies, the scientists concluded: “Long-term or chronic exposure to TiO2 nanoparticles could potentially lead to the gradually increased Ti contents in the brain, which may eventually induce impairments on the neurons and glial cells and lead to CNS dysfunction as a consequence.”

The gastrointestinal tract is a complex barrier/exchange system, and is the most important route by which macromolecules can enter the body. The main absorption takes place through villi and microvilli of the epithelium of the small and large intestines, which have an overall surface of about 200 m². Already in 1922, it was recognized by Kumagai, that particles can translocate from the lumen of the intestinal tract via aggregation of intestinal lymphatic tissue (Peyer’s patch, containing M-cells (phagocytic enterocytes)). Uptake can also occur via the normal intestinal enterocytes. Solid particles, once in the sub-mucosal tissue, are able to enter both the lymphatic and blood circulation.

It adds a bright white color to coffee creamers, baked goods, chewing gums, hard-shell candies, puddings, frostings, dressings, and sauces. But the nanoparticles found in “food-grade” titanium dioxide may accumulate in the body and cause DNA damage—which is one way chemicals cause cancer and other health problems. 

In a study published in the journal Food and Chemical Toxicology in 2016, researchers investigated whether titanium dioxide exposure led to an increase in colorectal tumor creation in mice by using a colitis associated cancer model. By measuring tumor progression markers, the researchers found that mice given titanium dioxide experienced enhanced tumor formation in the distal colon.  There was also a decrease of cells that act as a protective barrier in the colon. The researchers wrote: “These results suggest that E171 could worsen pre-existent intestinal diseases.”