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Vitamin A (VA)-fortified rice is a potential intervention strategy to prevent VA deficiency in at-risk populations. Hot- extruded, triple-fortified rice grains with added VA, zinc, and iron were produced by hot extrusion technology and their ability to improve VA status was tested in Thai schoolchildren. The fortification levels were 10 mg of iron, 9 mg of zinc, and 1.05 mg of VA/g extruded rice. A paired stable isotope dilution technique with labeled 13C2-retinyl acetate (13C-RID) was used to quantify VA pool size at the beginning and end of the feeding period. Fifty healthy schoolchildren with a serum retinol (SR) concentration of >0.7 µmol/L were randomly assigned to 2 groups to receive either triple-fortified rice (n = 25) or natural rice (n = 25) for 2 mo as part of the daily school meal. The fortified grains, mixed 1:50 with regular rice, were estimated to provide an extra 890 µg of VA/d, 5 d/wk. 13C2-retinyl acetate (1.0 µmol) was administered orally to each child before and at the end of the feeding period to estimate total body reserves (TBRs) of VA, which increased significantly (P < 0.05) in the intervention group from 153 ± 66 µmol retinol at baseline to 269 ± 148 µmol retinol after 2 mo of feeding. There was no change in the TBRs of VA in the control group (108 ± 67 vs. 124 ± 89 µmol retinol) (P = 0.22). Serum retinol remained unchanged in both groups. We conclude that VA-fortified, hot-extruded rice is an efficacious vehicle to provide additional VA to at-risk populations, and that the efficacy of VA-fortified foods can be usefully monitored by the 13C-RID measurement of TBRs of VA but not by changes in SR concentration. This trial was registered at clinicaltrials.gov as NCT01199445. [ABSTRACT FROM AUTHOR]

Vitamin A deficiency is a major global public health problem. Among the variety of techniques that are available for assessing human vitamin A status, evaluating the provitamin A nutritional values of foodstuffs and estimating human vitamin A requirements, isotope dilution provides the most accurate estimates. Although the relative expense of isotope dilution restricts its applications, it has an important function as the standard of reference for other techniques. Mathematical modelling plays an indispensable role in the interpretation of isotope dilution data. This review summarises recent applications of stable isotope methodology to determine human vitamin A status, estimate human vitamin A requirements, and calculate the bioconversion and bioefficacy of food carotenoids. [ABSTRACT FROM AUTHOR]