Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2009
Publication Date: 6/1/2009
Citation: Tang, G., Qin, J., Dolnikowski, G.G., Russell, R.M., Grusak, M.A. 2009. Golden Rice is an effective source for vitamin A. American Journal of Clinical Nutrition. 89:1776-1783.
Interpretive Summary: Golden Rice is a genetically modified rice that was developed to be able to make beta-carotene, a pro-vitamin A carotenoid, in the grain endosperm (that is, the normally white portion of the grain). This rice was designed to help rice-eating populations in developing countries, where vitamin A deficiency is often a serious nutritional problem. Until now, we have not known how effectively beta-carotene from Golden Rice was absorbed in the human gut, or how efficiently this beta-carotene was converted to vitamin A. This information is important for projecting the amount of Golden Rice consumption that might be needed in different population groups to satisfy their daily vitamin A requirements. In this study, we used a procedure whereby Golden Rice was grown with a special form of water (heavy water) that allowed us to tag the beta-carotene made in the rice grains, such that we could subsequently track the amount of beta-carotene absorbed by an individual and calculate how much of this was converted to vitamin A. We fed tagged Golden Rice to five adult volunteers and learned that the Golden Rice beta-carotene was readily absorbed and that it also was converted to vitamin A very efficiently. On average, four units of Golden Rice beta-carotene provided one unit of vitamin A. These results show that Golden Rice can be an effective source for vitamin A in developing world populations. This information will now allow us to calculate dietary intake amounts of Golden Rice for different age and gender groups, in order to provide adequate amounts of vitamin A.
Technical Abstract: Genetically engineered "Golden Rice" contains up to 35 ug Beta-carotene per gram of rice. It is important to determine the vitamin A equivalency of Golden Rice Beta-carotene to project the potential effect of this biofortified grain in rice-consuming populations that commonly exhibit low vitamin A status. The objective was to determine the vitamin A value of intrinsically labeled dietary Golden Rice in humans. Golden Rice plants were grown hydroponically with heavy water (deuterium oxide) to generate deuterium-labeled [2H]Beta-carotene in the rice grains. Golden Rice servings of 65–98 g (130–200 g cooked rice) containing 0.99–1.53 mg Beta-carotene were fed to 5 healthy adult volunteers (3 women and 2 men) with 10 g butter. A reference dose of [13C10]retinyl acetate (0.4–1.0 mg) in oil was given to each volunteer 1 wk before ingestion of the Golden Rice dose. Blood samples were collected over 36 d. Our results showed that the mean (+/- SD) area under the curve for the total serum response to [2H]retinol was 39.9 +/- 20.7 ug·d after the Golden Rice dose. Compared with that of the [13C10]retinyl acetate reference dose (84.7 +/- 34.6 ug·d), Golden Rice Beta-carotene provided 0.24–0.94 mg retinol. Thus, the conversion factor of Golden Rice Beta-carotene to retinol is 3.8 +/- 1.7 to 1 with a range of 1.9–6.4 to 1 by weight, or 2.0 +/- 0.9 to 1 with a range of 1.0–3.4 to 1 by moles. Beta-Carotene derived from Golden Rice is effectively converted to vitamin A in humans. This trial was registered at clinicaltrials.gov as NCT00680355.