GlyNAC — The Glutathione Precursor Duo

Glutathione (GSH) is the most abundant endogenous intracellular antioxidant, but its levels decline with age due to reduced availability of its precursor amino acids. GlyNAC provides equimolar amounts of glycine and cysteine (via NAC) to fuel the two-step enzymatic synthesis of GSH catalyzed by glutamate-cysteine ligase and glutathione synthetase. Elevated intracellular GSH neutralizes reactive oxygen species (ROS), protecting mitochondrial membranes and genomic DNA from oxidative damage. This reduction in oxidative stress downstream improves mitochondrial glucose and fatty-acid oxidation, lowers systemic inflammation, and positively influences nutrient sensing pathways such as AMPK and insulin signaling.

Multiple randomized clinical trials in older adults have demonstrated that GlyNAC supplementation significantly improves intracellular glutathione levels, mitochondrial function, and physical performance. A notable 16-week double-blind RCT (Kumar et al., 2021) showed that GlyNAC corrected GSH deficiency, reduced oxidative stress, and increased gait speed and muscle strength in older adults, with benefits reversing upon cessation. Further trials indicate improvements in insulin resistance, systemic inflammation, and multiple hallmarks of aging.

Clinical trials in older adults typically use weight-based dosing of 100 mg/kg/day each of glycine and NAC, which translates to roughly 7–8 grams of each per day for an average adult. Over-the-counter supplements often provide lower doses, such as 1,000–2,000 mg of each per day. It is typically taken orally in divided doses.

GlyNAC is generally recognized as safe and well-tolerated in clinical trials up to 24 weeks. Mild adverse effects may include gastrointestinal discomfort, nausea, or diarrhea, primarily driven by the NAC component. Due to its potential to modulate immune function and detoxification pathways, caution is advised for individuals on immunosuppressive medications or those with cystinuria.

Key Papers