Bioavailability of Non-Provitamin A Carotenoids

The role of carotenoids in human nutrition has gained increased interest, especially due to their associated health-beneficial effects for a number of chronic diseases, including certain types of cancer and cardiovascular disease. Whereas data is available on the intake and presence of carotenoids in foods, limited information exists on factors influencing their bioavailability, especially for the non-provitamin A carotenoids. However, carotenoid absorption strongly depends on a number of factors which are not entirely understood. These include mainly the release of carotenoids from the food matrix, their incorporation into mixed bile micelles, the transfer of carotenoids from micelles to the mucosa for passive or facilitated absorption (via SR-BI proteins), and the sequestration into chylomicrons. Thus, dietary compounds influencing carotenoid micelle incorporation, e.g. the amount fat present in an ingested meal or components competing for uptake, such as phytosterols and other carotenoids, can have a considerable impact on carotenoid bioavailability. However, the effect of many dietary factors, including dietary fiber, type of fat, or minerals on carotenoid absorption is not well understood. In addition, bioavailability also depends on the carotenoid structure; in general, polar carotenoids are preferably incorporated into mixed micelles and tend to be of higher bioavailability, as may be the case for free vs. esterified xanthophylls, and cis-isomers vs. their trans-form, due to apparent shorter chain-lengths. Whereas their importance as part of a healthy diet warrants an improved understanding of carotenoids, their dietary fate following ingestion, including their stability, efficiency of micelle-incorporation, and pathway of absorption are still marginally understood.