 The study will use stable isotope labeled high ß-C yellow maize and vitamin A in a well-nourished population by utilizing stable isotope dilution techniques. In this project, deuterium labeled vitamin A that is derived from the labeled ß-C yellow maize will be traced after being eaten by a human subject. Eight men 40 years and 70 y who are healthy, non-smoking,body weight within 20 of standard weight for height Metropolitan and not having taken vitamin A or ß-C supplements within the last month will be recruited as volunteers. This study will last for 50 days during which at day 1, cooked labeled yellow maize paste porridge equal to a total of 2 bowls cooked yellow maize from 100 - 200 g dry weight containing 1 mg ß-C will be taken by each volunteer. On day 8, a labeled vitamin A 1 mg of 13C retinyl acetate in oil dose will be used in evaluation of liver storage of vitamin A. Forty six blood samples 460 cc will be taken during the study which will be analyzed for serum carotenoids and retinoids using HPLC and mass spectrometry techniques. 