Meeting the Vitamin A Requirement: The Efficacy and Importance of β-Carotene in Animal Species
Table 2
Estimated efficiency of conversion of -carotene to vitamin A in animals, defined as g of -carotene required to form 1 RE (1 g retinol). The value given is the total number of animals in the study.
Species
Conversion ratio
Study design
References
Herbivorous mammals
Cow
8.33
Recommendation extrapolated from study in lambs [122].
Depletion/repletion study with BC supplement in water-soluble beadlet form; serum retinol and relative dose response test used to indicate VA status (). Supplementation with 215,00 g BC/d did not restore VA status, while 21,500 RE as retinyl palmitate did (though not completely).
Stable isotope study administering physiological doses of 13C-BC in oil to children for ≤10 wk (); concurrent administration of 13C-retinyl acetate allowed estimation of BC bioefficacy from serum response.
Stable isotope study administering single oral doses of 2H-BC to adults (); concurrent administration of 2H-retinyl acetate allowed estimation of BC bioefficacy from serum response.
Subjects consumed single meal of intrinsically labeled 2H-spinach and 2H-carrots (); concurrent reference dose of 13C-retinyl acetate allowed estimation of BC bioefficacy from serum response.
Gilts were fed low VA diet for only 4 weeks, and there was no indication that they were truly depleted (); supplemented with 100 mg BC in water-soluble beadlets; hepatic VA used to indicate status.
Depletion/repletion study in which chicks born from breeding pairs fed VA-devoid diet consumed VA or BC (synthetic) supplemented diets for 38 d (); hepatic VA used to indicate status.