Currently, titanium dioxide as a food additive is classified as GRAS, or “generally recognized as safe.”
It should also be considered that due to the low pH in the stomach, the increased dissolution of the TiO2 particles may increase its bioavailability and may facilitate the entry of titanium ions into the blood circulation. Despite the relatively large consumption of TiO2 as a food additive, no studies on the effect of pH on its absorption and bioavailability have been found in the literature. This can be attributed to a general belief that TiO2is completely insoluble. However, this is not completely true, as TiO2 particles show a certain degree of solubility.
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.”
1. Using roasting and leaching method. The reaction equation is as follows: