Investigating in vitro digestion of food models to explain in vivo micronutrient bioavailability

IntroductionA major challenge in the next years will consist in producing healthy and sustainable foods with optimizednutritional quality. Food fortification to increase micronutrient intakes is a strategy currentlyused to overcome deficiencies.ObjectiveSince the structural characteristics of food influence disintegration process during digestion, it appearsrelevant to assess the impact of food structure on micronutrient bioavailability.MethodologyFour model foods have been developed and enriched in lutein and vitamin D. These products weredesigned such as their composition was identical but their structures and textures were different.Custard, pudding, sponge cake and biscuit were thus produced by modulating the production process.A clinical trial has been set up, involving twelve healthy male subjects for a monocentric, controlledand randomized study, in a cross experimental design. After an overnight fast, kinetics of plasmamicronutrient levels were recorded for 8 hours following each product consumption. In a secondphase, the model foods have been digested using the INFOGEST in vitro model. Kinetics of matrixdisintegration and micronutrients release have been recorded.Main findingsThe micronutrient absorption curves depended on the matrix. Especially, the biscuit resulted in asignificantly later peak of maximal absorption for both micronutrients, and a lower total bioavailabilityfor vitamin D. In vitro, digestion might enable to determine which food characteristics influencematrix disintegration, thereby affecting micronutrient bioaccessibility. Indeed, markers of matrix disintegration,namely proteolysis and lipolysis kinetics, suggested differences amongst the four modelfoods.ConclusionThe in vivo results highlight that food structure modulates the kinetics of micronutrient appearancein plasma. Correspondences might be established between the kinetics of food matrix disintegrationduring in vitro digestion and the kinetics of micronutrient absorption during the clinical study. Usingthe DIDGI, a dynamic in vitro digestion model, further studies will aim to refine the quality of themodel and the results obtained.