Levels of glutathione will be measured in plasma, lymphocytes, and red blood cells as well as in exfoliated buccal mucosal cells. Biomarkers of oxidative stress will include blood levels of glutathionylated proteins and 8-isoprostanes and urine levels of 8-hydroxydeoxyguanosine. Glutamylcystine ligase and GST activities, and C-reactive protein will be determined in blood. Immune function biomarkers will be analyzed including t-natural killer cell cytotoxicity, lymphoproliferation, neutrophils phagocytosis, neutrophil respiratory burst assays.