The purpose of this study is to determine the level of sulfur amino acids in the diet that is needed to maintaining glutathione antioxidant status. This information could prove very useful in medicine because it could allow identification of an optimal diet for control of antioxidant levels. This diet could be used in conjunction with other therapies in order to prevent or delay oxidative stress and any diseases that may result from this. Total study participation will include a screening visit and a 14-day study period where dietary intake of sulfur amino acids will be controlled. We aim to enroll 12 normal subjects at Emory University Hospital.The primary hypothesis is that steady-state GSH/GSSG and CYS/CYSS redox in human plasma will become oxidized due to SAA intake at 0% of the RDA and reduced due to SAA intake at 3X the RDA.