Golden Rice Is An Effective Source of Vitamin A.

Golden Rice (GR) is a transgenic product that is engineered to produce beta-carotene in the rice endosperm. It has been developed as a means to combat vitamin A malnutrition, which unfortunately exists throughout much of the developing world. To determine the vitamin A value (i.e., beta-carotene conversion efficiency) of this rice, GR beta-carotene was intrinsically labeled with deuterium, a non-radioactive stable isotope of hydrogen, by growing plants in a nutrient solution containing 23% heavy water (deuterium oxide). The GR beta-carotene was enriched with deuterium with the highest abundance isotopomer peak at M+9.  Healthy adult subjects were given a known amount of an oil capsule of ¹³C₁₀-retinyl acetate as a reference dose, in addition to deuterium-labeled GR.  Serum samples collected from the subjects were analyzed using GC/ECNCI-MS for the enrichments of labeled retinol by monitoring the isotopomers M+5 (derived from GR) and M+10 (derived from ¹³C₁₀-retinyl-acetate).  By using the response to the dose of ¹³C₁₀-retinyl acetate as reference, one completed study (n = 5) showed that the conversion efficiency of GR beta-carotene was 3.8 ± 1.7 to 1 (Mean ± SD) by weight (GR beta-carotene dose of ~1 mg).  More results of various vitamin A equivalency studies with Golden Rice and a non-transgenic high-beta-carotene maize are ongoing. Results of these studies will be presented and will be discussed in the context of Golden Rice's potential contribution to population-based vitamin A adequacy. (Funded by USAID, NIH DK60021, USDA 58-1950-7-707, 1950-51000-065-04, 6250-2150-042, and Syngenta Foundation).