The recent years have seen a significant interest in the applications of nanotechnology in various facets of our lives. Due to their increasingly widespread use, human exposure to nanoparticles (NPs) is fast becoming unavoidable. Among the wide group of nanoparticles currently employed in industry, titanium dioxide nanoparticles, TiO2 NPs, are particularly popular. Due to its white colour, TiO2 is widely used as a whitening food additive (E 171). Yet, there have been few studies aimed at determining its direct impact on bacteria, while the available data suggest that TiO2 NPs may influence microbiota causing problems such as inflammatory bowel disease, obesity, or immunological disorders. Indeed, there are increasing concerns that its presence may lead to intestinal barrier impairment, including dysbiosis of intestinal microbiota. This article aims to present an overview of studies conducted to date with regard to the impact of TiO2 NPs on human microbiota as well as factors that can affect the same. Such information is necessary if we are to conclusively determine the potential toxicity of inorganic nanoparticles.