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Titanium dioxide is a naturally-occurring mineral found in the earth’s crust. Because of its white color, opaqueness, and ability to refract light, the ingredient is often used as a pigment, brightener, and opacifier, which is an ingredient that makes a formulation more opaque. Titanium dioxide is also a UV filter and so is an effective active ingredient in sunscreens. It’s often used in cosmetic loose and pressed powders, especially “mineral powder” cosmetics, in addition to other cosmetics, lotions, toothpaste, and soap.

In a study published in the journal Environmental Toxicology and Pharmacology in 2020, researchers examined the effects of food additives titanium dioxide and silica on the intestinal tract by grouping and feeding mice three different food-grade particles — micro-TiO2, nano-TiO2, and nano-SiO2.  With all three groups, researchers observed changes in the gut microbiota, particularly mucus-associated bacteria. Furthermore, all three groups experienced inflammatory damage to the intestine, but the nano-TiO2 displayed the most pronounced changes. The researchers wrote: “Our results suggest that the toxic effects on the intestine were due to reduced intestinal mucus barrier function and an increase in metabolite lipopolysaccharides which activated the expression of inflammatory factors downstream. In mice exposed to nano-TiO2, the intestinal PKC/TLR4/NF-κB signaling pathway was activated. These findings will raise awareness of toxicities associated with the use of food-grade TiO2 and SiO2.”