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

Inclusion Criteria in: 1. Healthy school-aged children * Body weight ≥ 22 kg * No history of anemia * Willingness to participate 2. Healthy Young Adults * Consent provided * Aged 19 - 40 years old * In good general health as evidenced by medical history, physical health and blood draw * Fasting blood glucose, hemoglobin A1c (HbA1c), urea, creatinine, vitamin-B6, vitamin-B12 and folate levels within normal ranges for age. * Willingness to participate in the study. * BMI \<25 kg/m2. 3. Healthy Old Adults * Consent provided * Aged 60- 90 years old * In good general health as evidenced by medical history, physical health and blood draw * Fasting blood glucose, hemoglobin A1c (HbA1c), urea, creatinine, vitamin-B6, vitamin-B12 and folate levels within normal ranges for age. * Willingness to participate in the study. * BMI \<30 kg/m2. Exclusion Criteria in: 1. Healthy school-aged children * HIV * Diabetes * Anaemia * Significant weight loss within 30 days of study * On weight loss diets * Body weight less that 22kg * Inability to tolerate diet * Unwilling to have blood drawn 2. Healthy Young and Old Adults: * Presence of chronic disease and/or acute illness known to affect GSH and/or protein/amino acid metabolism (e.g. HIV, diabetes, cancer, liver or kidney disease, acute cold or flu). * Anemia (15 - 20% outside lower limit of normal lab reference ranges) * Taking medications known to affect GSH and/or protein/AA metabolism (e.g. acetaminophen, steroids). * Significant weight loss during the past month or consumption of weight reducing diets. * Significant caffeine consumption (\>2 cups per day). * Significant consumption of alcohol (\>1 drink per day i.e. 1 beer or ½ glass of wine). * Inability to tolerate the diet * Unwilling to have blood drawn from a venous access during the isotope infusion day.