 The serum concentration and isotope ratio of ß-C and retinol will be determined. Serum enrichment curve following each oral dose will be studied. The area under the curve AUC of retinol-d4 and labeled retinol from the reference dose in serum samples will be determined and compared. The equivalence of a high ß-C corn meal to vitamin A will be calculated based on the isotope reference method to determine the efficiency of corn ß-C to provide vitamin A. 