An increased intake of fruits and vegetables has been shown to be associated with reduced risk of cancer. In epidemiological studies, supplements of β-carotene, which is abundant in fruits and vegetables, were not found to be beneficial in reducing the incidence of lung cancer in high-risk groups. Epoxycarotenoids are abundant in nature. 5,6-Epoxy-β-carotene was much more active than β-carotene in the induction of differentiation of NB4 cells [Duitsman, Becker, Barua and Olson (1996) FASEB J. 10, A732]. Epoxycarotenes may, therefore, have protective effects against cancer. In order to do this, however, epoxycarotenoids must be absorbed by the human body. There is no evidence that epoxycarotenoids, despite their abundance in dietary fruits and vegetables, are absorbed by humans. In this paper, it is demonstrated that orally administered dietary or synthetic epoxy-β-carotenes are absorbed by humans, as indicated by their appearance in the circulating blood.

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