Calcium and phosphorus bioaccessibility from different amino acid-based medical nutrition formulas for infants and children under in vitro digestive conditions

Summary: Objective: Mineral bioavailability from food is important for infants and young children. Mineral bioavailability is influenced by many factors, including e.g., the food matrix, mineral composition, and route of administration. Moreover, physiological factors, such as mineral status and use of medication (e.g., proton-pump inhibitors), are important. The aim of this research was to investigate in two separate, complementary experimental setups the bioaccessibility of calcium (Ca) and phosphorus (P) from amino acid-based medical nutrition infant formulas. Methods: Since this cannot be studied directly in infants and young children due to ethical restrictions, this was tested in a validated, dynamic, computer-controlled in vitro model of the stomach and small intestine (TIM-1). Furthermore, for comparison, two infant and two junior formulas with different mineral salt compositions from two manufacturers were tested in batch digestion experiments, mimicking intestinal feeding. Minerals were analyzed using ICP-MS. Results: Bioaccessibility of Neocate Infant formula was 51.4% ± 2.2% for Ca and 66.9 ± 5.5% for P in the dynamic in vitro model of the stomach and small intestine (TIM-1). The Ca bioaccessibility in the batch experiments ranged from 12% to 17% for the different formulas. The P bioaccessibility ranged from 50% to 61%. Conclusions: The combined experiments showed adequate Ca and P bioaccessibility in the four commercial formulas, with comparable bioaccessibility between manufacturers. The TIM-1 experiments showed the importance of the gastric phase (low pH) for solubility and bioaccessibility of the minerals.