The gastrointestinal fate of inorganic and organic nanoparticles in vitamin D-fortified plant-based milks

Abstract

Both organic and inorganic nanoparticles are often added to food and beverage products to modify their quality attributes, such as their look, feel, flavor, or shelf life. However, there is still poor understanding of how these nanoparticles behave inside the human gut after ingestion, particularly their impact on macronutrient digestion and vitamin bioavailability. In this study, nanocellulose, nanoemulsion, and titanium dioxide (TiO2) particles were used as examples of functional organic and inorganic nanoparticles, while vitamin D-fortified plant-based milks were used to model food products. The plant-based milks were fortified with this vitamin by mixing them with vitamin-D loaded nanoemulsion droplets. The TiO2 nanoparticles were shown to be most effective at increasing the whiteness of the fortified milk, whereas the nanocellulose ones were most effective at increasing the shear viscosity. Alterations in the physicochemical and structural properties of the nanoparticle-loaded model foods were measured as they passed through a harmonized (INFOGEST) in vitro gastrointestinal tract (GIT). The oil bodies in the plant-based milks were strongly flocculated in the stomach but they were still fully digested in the small intestine. The distribution of the nanoparticles in the intestinal fluids was analyzed by optical and transmission electron microscopy, which showed that they were well dispersed, presumably due to protein-adsorption to their surfaces and the mechanical action of the GIT fluids. The addition of TiO2 or nanocellulose to the fortified milks did not significantly affect lipid digestion or vitamin bioaccessibility. Interestingly, our results showed that the bioaccessibility of vitamin D in the plant-based milk was relatively low (~20%) in all samples analyzed. We hypothesized that this may have been due to aggregation and precipitation of the vitamin-loaded micelles in the presence of other components in the GIT fluids, such as calcium ions. Our results are useful for understanding the impact of different kinds of nanoparticles on the behavior of foods in the gastrointestinal tract.