Here we propose that the efficiency of micellarization of provitamin A carotenoids during simulated digestion of plant foods is an effective tool for the initial screening of the relative bioavailabilities of carotenoids from candidate cultivars. This in vitro model can also be used to evaluate the effect of different food processing and meal preparation methods. We further propose that the coupling of simulated digestion with the Caco-2 human intestinal cell line can be useful for confirming that micellarized provitamin A carotenoids are indeed accessible for uptake by absorptive small intestine cells. Results from such studies are expected to facilitate the selection of appropriate cultivars for in vivo studies with gerbils or ferrets. Animal studies in turn will generate data that can be used to identify plants and processing methods that merit examination in human intervention trials in local communities.
This review is organized as follows. First, the characteristics of the digestion and absorption and the metabolism of vitamin A and carotenoids are briefly discussed in Sections 2 and 3, respectively. The numerous factors that affect carotenoid bioavailability are considered in Section 4. Section 5 first presents an overview of the techniques used to determine the relative bioavailabilities of carotenoids in vivo, and then describes the biochemical and cellular methods that are used to investigate the gastrointestinal processes associated with the accessibility and cellular transport of carotenoids. Key results from studies employing in vitro methods are systematically reviewed in Section 6. Finally Section 7 directly compares the findings of in vivo and in vitro studies and, on the basis of this comparison, proposes the use of simulated digestion and Caco-2 cells as tools for the initial screening for the relative bioavailability of provitamin A carotenoids from staple foods prepared according to local methods.