Fortification of Plant-Based Milk with Calcium May Reduce Vitamin D Bioaccessibility: an in Vitro Digestion Study

Many plant-based milks lack key micronutrients found in bovine milk, such as calcium and vitamin D. In this study, we fortified almond milk with these two micronutrients and used a standardized gastrointestinal model to examine the impact of product formulation on their bioaccessibility. The impact of different forms (CaCl2 versus CaCO3) and concentrations (0, 1, or 2 g per 240 mL) of calcium on the physicochemical properties, lipid digestibility, and vitamin D bioaccessibility was examined. Soluble calcium (CaCl2) promoted particle aggregation by reducing the electrostatic repulsion, while colloidal calcium (CaCO3) did not because there were fewer free calcium ions. High levels of calcium (soluble or insoluble) reduced vitamin D bioaccessibility, which was attributed to insoluble calcium soap formation in the small intestine. Calcium bioaccessibility was higher for CaCO3 than CaCl2. These findings are useful for the development of nutritionally fortified plant-based milks with improved physicochemical and nutritional properties.