In a 2019 study published in the journal Nanotoxicology, researchers recreated the first phase of digestion in mice and fed them titanium dioxide, then examined whether accumulation occurred in the organs. Researchers wrote: “Significant accumulation of titanium was observed in the liver and intestine of E171-fed mice; in the latter a threefold increase in the number of TiO2 particles was also measured. Titanium accumulation in the liver was associated with necroinflammatory foci containing tissue monocytes/macrophages. Three days after the last dose, increased superoxide production and inflammation were observed in the stomach and intestine. Overall, [this] indicates that the risk for human health associated with dietary exposure to E171 needs to be carefully considered.”
Though the Food and Drug Administration (FDA) categorizes titanium dioxide as Generally Recognized as Safe (8), other organizations have issued warnings.