When used in food specifically, titanium dioxide is known as an additive called E171 and can be found in products like candy, chocolate, coffee creamer, cake decorations, chewing gum and even vitamin supplements. E171 is often used as coloring additive in foods, to lend the processed item a natural whiteness and opacity — such as in Skittles candy, where it's used as a white base to help give the candies their signature bright, colorful hue.

Australian researchers examined how titanium dioxide as a food additive affected gut microbiota in mice by orally administering it in drinking water. The study, published in the journal Frontiers in Nutrition in 2019, found the treatment could “alter the release of bacterial metabolites in vivo and affect the spatial distribution of commensal bacteria in vitro by promoting biofilm formation. We also found reduced expression of the colonic mucin 2 gene, a key component of the intestinal mucus layer, and increased expression of the beta defensin gene, indicating that titanium dioxide significantly impacts gut homeostasis.” The changes were then linked to colonic inflammation, along with a higher expression of inflammatory cytokines, which are signal proteins that help with regulation. The researchers concluded that titanium dioxide “impairs gut homeostasis which may in turn prime the host for disease development.”