Bioaccessibility and uptake/epithelial transport of vitamin E: Discoveries and challenges of in vitro and ex vivo assays

Vitamin E comprises compounds consisting of a chromanol ring and an isoprenoid side-chain, and is an essential lipid-soluble nutrient with several physiological functions. Vitamin E intake has been reported as inadequate for some populations. Only a fraction of dietary vitamin E is effectively released from the food matrix (bioaccessible fraction), absorbed (enterocyte uptake/epithelial transport) and transported in lipoproteins to reach the target tissues (bioavailable fraction), depending on the food structure, composition, and processing. Therefore, research concerning the fate of vitamin E through the gastrointestinal tract is of paramount importance for developing healthy foods and guiding effective public policies. The combination of simulated in vitro gastrointestinal digestion followed by intestinal epithelial transport and/or enterocyte uptake assays using ex vivo cell models has been successfully used to mimic the physiological conditions and predict the bioaccessibility and epithelial transport of compounds. The objective of this review was to summarize the current knowledge and challenges for predicting the bioaccessibility and uptake/epithelial transport of vitamin E by in vitro and ex vivo assays. Here, we revisited the metabolism of vitamin E and introduced in vitro and ex vivo methods for estimating the bioaccessibility and intestinal absorption of vitamin E. This review compiles data on vitamin E bioaccessibility in vitro and uptake/epithelial transport ex vivo for different food matrices, and discusses the factors that can affect their measurement. Additionally, co-culture approaches using hepatic lineages to assess vitamin E bioavailability are further presented.