β-
Carotene intake and tissue/blood concentrations have been associated with reduced incidence of several
chronic diseases. Further bioactive
carotenoid-metabolites can modulate the expression of specific genes mainly via the
nuclear hormone receptors:
retinoic acid receptor- and
retinoid X receptor-mediated signalling. To better understand the metabolic conversion of β-
carotene, inter-individual differences regarding β-
carotene bioavailability and bioactivity are key steps that determine its further metabolism and bioactivation and mediated signalling. Major
carotenoid metabolites, the
retinoids, can be stored as
esters or further oxidised and excreted via phase 2 metabolism pathways. In this review, we aim to highlight the major critical control points that determine the fate of β-
carotene in the human body, with a special emphasis on β-
carotene oxygenase 1. The hypothesis that higher dietary β-
carotene intake and serum level results in higher β-
carotene-mediated signalling is partly questioned. Alternative autoregulatory mechanisms in β-
carotene /
retinoid-mediated signalling are highlighted to better predict and optimise nutritional strategies involving β-
carotene-related health beneficial mediated effects.