Twice the amount of α-carotene isolated from carrots is as effective as β-carotene in maintaining the vitamin A status of Mongolian gerbils

Abstract

The vitamin A (VA) value of carotenoids from fruits and vegetables is affected by many factors. This study determined the VA value of α-carotene isolated from carrots compared with β-carotene and retinyl acetate supplements fed to Mongolian gerbils (Meriones unguiculatus). Gerbils (n = 38) were fed a VA-free diet for 4 wk. At baseline, 6 gerbils were killed to determine liver VA. Gerbils were divided into 3 treatment groups (n = 9/group) and given 35, 35, or 17.5 nmol retinyl acetate, α-carotene or β-carotene, respectively, in 2 divided doses 5 h apart each day. The remaining 5 gerbils received oil vehicle. Gerbils were killed after 3 wk of supplementation. Serum samples and livers were collected and analyzed for VA. Liver extracts were subsequently saponified to quantify α-retinol. Serum retinol concentrations did not differ among the groups. Liver retinyl palmitate concentrations were significantly higher in the retinyl acetate treatment group (0.198 ± 0.051 μmol/g; P < 0.05) than in all other groups. The α- and β-carotene treatments resulted in similar retinyl palmitate concentrations, i.e., 0.110 ± 0.026 and 0.109 ± 0.051 μmol/g, respectively, which did not differ from the concentrations in gerbils killed at baseline (0.123 ± 0.024 μmol/g). The oil group had significantly less retinyl palmitate (0.061 ± 0.029 μmol/g; P < 0.05) than all other groups. α-Retinol was detected in livers of the α-carotene group (0.062 ± 0.013 μmol/g). Thus, twice the amount of purified α-carotene maintained VA status as well as β-carotene in VA-depleted gerbils. Conversion factors were ∼5.5 μg α-carotene or ∼2.8 μg β-carotene to 1 μg retinol. © 2005 American Society for Nutrition.