Human serum concentrations of all-trans beta- and alpha-carotene but not 9-cis beta-carotene increase upon ingestion of a natural isomer mixture obtained from Dunaliella salina (Betatene).

The uptake of all-trans and 9-cis beta-carotene and of alpha-carotene from a natural carotene preparation from Dunaliella salina, Betatene, was studied in humans. All-trans beta-carotene and alpha-carotene were absorbed well and showed the expected biokinetics with serum peak concentrations between 24 and 48 h. The mean increase in serum concentrations of alpha-carotene was 5.6% of the increase of all-trans beta-carotene, reflecting the composition of these carotenoids in Betatene. 9-cis beta-Carotene, however, was not detected in human serum, even after repeated doses. This could be due to preferential absorption of all-trans beta-carotene, rapid distribution of 9-cis beta-carotene into the tissue, or the presence of isomerase activity processing 9-cis to all-trans beta-carotene.