Absorption and Metabolism of Carotenoids

Carotenoids are absorbed passively, dissolved in lipid micelles various studies have estimated the biological availability and absorption of dietary carotene as between 5% to 60%, depending on the nature of the food, whether it is cooked or raw, and the amount of fat in the meal. In addition, much of the carotene in foods is present as crystals that may not dissolve to any significant extent in intestinal contents (Parker, 1989 1996 Parker et al., 1999 Hickenbottom et al., 2002 Ribaya-Mercado, 2002 Tanumihardjo, 2002 Yeum and Russell, 2002). 

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During, A. and Harrison, E.H., Intestinal absorption and metabolism of carotenoids insights from cell culture. Arch. Biochem. Biophys., 430, 77, 2004. 

The U.S./Canadian Dietary Reference Values report (Institute of Medicine, 2001) introduced the term retinol activity equivalent to take account of the incomplete absorption and metabolism of carotenoids 1 RAE = 1 /xg of all-fra s-retinol, 12 /xg of /3-carotene, and 24 /xg of a-carotene or /3-crypto-xanthin. On this basis, 1 iu of vitamin A activity = 3.6 /xg of /3-carotene or... 

Schiedt, K., Absorption and metabolism of carotenoids in birds, fish and cmstaceans, in Carotenoids, Vol. 3 Biosynthesis and Metabolism, Britton, G., Liaaen-Jensen, S., and Pfander,... 

Finally, it should also be considered that flavonoid-rich foods contain a great diversity of compounds with bioactive properties (for e.g., carotenoids, other phenolics, fiber, and minerals), and multiple interactions occur among all of them. There is also great diversity in the ingestion, absorption, and metabolism of these compounds in different populations, and all of these circumstances could camouflage any effect of flavonoids on disease prevention or treatment. 

Olson, J. 1994. Absorption, transport, and metabolism of carotenoids in humans. Pure Appl. 

Astaxanthin has exhibited potent antioxidant, immunomodulating, and enzyme-inducing properties, all of which suggest a potential role for this carotenoid in the prevention of cancer. Moreover, its unique stractiual properties and its lack of prooxidant activity make it a prime candidate for further investigation. More research is needed on the absorption and metabolism of this promising anticancer agent in humans and on its interactions with other carotenoids and vitamins in the human system. 

Parker, RS, 1996. Absorption, metabolism, and transport of carotenoids. FASEB J 10, 542-551. 

Carotenoid absorption and metabolism have been comprehensively reviewed (Erdman et al., 1993 Parker, 1996 van Vliet, 1996 Furr and Clark, 1997 Yeum and Russell, 2002) and this chapter will focus only on recent advances in these areas. A particular emphasis will be placed on studies that used in vitro and cell culture models as tools to understand better the mechanisms of absorption on the molecular level. 

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