The knowledge of bioavailability, i.e. the fraction of bioactive compound
that can be absorbed and utilized, is a very relevant topic of food and nutraceutical
research. The present review sheds light to the concepts of bioavailability,
bioaccessibility, bioactivity, bioefficiency and bioconversion. Besides, it reviews the
main in vivo methods such as balance techniques (chemical balances and isotopes
methods), plasma biomarkers and animal models. Several in vitro methods that
simulate physiological conditions of the human gastrointestinal digestion (static or
dynamic models) and the usefulness of Caco2 culture cells for evaluating bioactive
compounds bioavailability in foods are also reviewed. The advantages and
disadvantages of these methods are discussed, beside specific conditions applied for
several bioactive compounds (minerals, carotenoids, α-tocopherols, folic acid, plant
sterols and polyphenols) from recent studies. Human studies are the method of choice,
and data obtained from these assays represent the gold reference because they provide
the most accurate results and the highest scientific evidence regarding the
bioavailability of a bioactive compound. In vitro models are reproducible, rapid and
simple, due to the fact they allow tight control of the experimental variables than
animal or human studies. These methods are particularly useful to check the impact of
digestion conditions and to undertake studies on the positive or negative effects of food
structure, food composition, dietetic factors and food processing. Furthermore, it is
mandatory to promote more research into in vivo-in vitro correlations using well
harmonized and standardized systems, so that more valid in vitro models can be
designed to evaluate the bioavailability of bioactive food compounds.
Keywords: Animal models, Balance studies, Bioaccessibility, Bioactive compounds,
Bioavailability, Caco2 cells, Simulated gastrointestinal digestion.