Glutathione (GSH) Synthesis in Healthy School-aged Children and Healthy Young and Old Adults

To measure the fractional and absolute synthesis rates of GSH, an antioxidant that protects cells from damage, in the erythrocytes of healthy school-aged children, young adults and old adults in response to graded intakes of protein in order to determine if increasing the protein intake above the current recommended DRI produces increases in the GSH synthesis rates in erythrocytes of these individuals. Participants will consume specially formulated diets with varying protein levels.