9‐cis β‐carotene in human plasma and blood cells after ingestion of β‐carotene

Abstract

For 44 wk, thirty male volunteers were given daily either 60 mg of synthesized all-trans β-carotene, a naturally-occurring β-carotene derived fromDunaliella bardawil, or a placebo. Basal levels of 9-cis β-carotene in plasma, platelets, and mononuclear cells were 10, 20 and 25% of those of the all-trans form, respectively. The plasma levels reached a maximum after two weeks of administration and plateaued thereafter in the subjects who took the β-carotene preparations. The all-trans β-carotene level in the subjects given the synthesized all-trans form was almost twice that for theDunaliella preparation. The plasma 9-cis level was found to be higher in the all-trans β-carotene group than in theDunaliella group, despite no intake of the 9-cis form in the all-trans group and the higher intake of the 9-cis form in theDunaliella group. This finding suggests that isomerization of the all-trans form to the 9-cis form may occur in the body either during or after absorption.