Overall, the Food Directorate's comprehensive review of the available science of TiO2 as a food additive showed:
However, they did find that minor levels of 0.01% were absorbed by immune cells — known as gut-associated lymphoid tissue — and may be delivered to other organs. Currently, it’s unknown how this may affect human health (17Trusted Source).
The evidence also suggests that the toxicity of TiO2 particles may be reduced when eaten as part of the diet. This is because proteins and other molecules in a person's diet can bind to the TiO2 particles. This binding alters the physical and chemical properties of the particles, which influences how they interact with cells, tissues and organs.
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.”