The investigators have previously reported that older patients with HIV are deficient in glutathione (GSH) due to decreased availability of cysteine and glycine, and that oral supplementation with cysteine (as n-acetylcysteine) and glycine for 2-weeks corrects their own levels, and improves concentrations of red-cell GSH. The investigators also found that when GSH deficient, subjects had impaired mitochondrial energetics and this improved with an increase in intracellular GSH concentrations. The current proposal will investigate if cysteine and glycine supplementation for a duration of 24 weeks will result in changes in : (a) GSH levels; (b) body composition/anthropometry; (c) strength and function; (d) quality of life; (e) mitochondrial energetics; (f) biochemistry (including dyslipidemia and oxidative stress); (g) protein and glucose metabolism; (h) cognition and memory. 3 months after completing supplementation, measurement of GSH concentrations, strength, function, mitochondrial energetics and neurocognitive tests will be done to determine the effects of washout.