Bioavailability of a Natural Isomer Mixture as Compared with Synthetic all-trans-β-Carotene in Rats and Chicks

Abstract

The unicellular halotolerant alga Dunaliella bardawil was previously shown to contain high concentrations of β-carotene composed of about equal amounts of the all-trans and 9-cis isomers. One-d-old chicks and 7-wk-old male rats were fed diets supplemented with synthetic all-trans-β-carotene or dry D. bardawil at equivalent levels of β-carotene. The chicks were fed diets containing up to 0.025% β-carotene for 2 mo, and the rats up to 0.1% β-carotene for 2 wk. Liver analyses at the end of these periods indicated that both species showed at least a tenfold higher accumulation of the algal β-carotene isomer mixture than of the synthetic all-trans-β-carotene. The ratio of 9-cis-β-carotene to the all-trans isomer in the livers of the algae-fed rats and chicks was similar to or higher, respectively, than that present in the algae. Retinol plus retinyl ester accumulated to a similar extent in the rats and chicks fed diets supplemented with synthetic all-trans or the natural isomer mixture of β-carotene. The preferable accumulation of the natural isomer mixture of β-carotene suggests that attention should be paid to the different sources of β-carotene when testing their efficacy in effects other than providing retinol, such as in their possible role in the prevention of some types of cancer.