The enrichment of labeled ß-C and labeled retinol in human circulation will be determined using advanced liquid chromatography / mass spectrometry and gas chromatography / mass spectrometry. Through the applications of these novel technologies, we will be able to determine the relative biological activities of endogenous carotenoids; that is, the vitamin A value of spinach, Golden Rice, and ß-C in oil capsules for children with/without vitamin A malnutrition.