Nutritional aspects of phytoene and phytofluene, carotenoid precursors to lycopene.

Epidemiological studies suggest an inverse relationship between tomato consumption and serum and tissue lycopene (LYC) levels with risk of some chronic diseases, including several cancers and cardiovascular disease. LYC, the red carotenoid found in tomatoes, is often considered to be the primary bioactive carotenoid in tomatoes that mediates health benefits, but other colorless precursor carotenoids, phytoene (PE) and phytofluene (PF), are also present in substantial quantities. PE and PF are readily absorbed from tomato foods and tomato extracts by humans. Animal models of carotenoid absorption suggest preferential accumulation of PE and PF in some tissues. The reasonably high concentrations of PE and PF detected in serum and tissues relative to the concentrations in foods suggest that absorption or metabolism of these compounds may be different from that of LYC. Experimental studies, both in vitro and in vivo, suggest that PE and PF exhibit bioactivity but little is known about their impact in humans. Methods for producing isotopically labeled PE, PF, and LYC tracers from tomato plant cell culture offer a unique tool for further understanding the differential bioavailability and metabolism of these 3 prominent tomato carotenoids and how they may affect health.