Two amino acids — glycine and N-acetylcysteine — combined and dosed correctly produced striking improvements in glutathione levels, mitochondrial function, insulin resistance, and walking speed in older adults at Baylor. Here's the protocol and how to do it.
In 2021, a research team at Baylor College of Medicine published a small but striking randomized trial of an intervention they called GlyNAC — a combination of glycine and N-acetylcysteine (NAC) — in older adults. The 16-week trial showed substantial improvements in glutathione synthesis, mitochondrial function, insulin resistance, body composition, walking speed, cognition, and several inflammatory markers. The effect size was unusual for a nutritional intervention, particularly for the functional outcomes in older adults.
The GlyNAC protocol has since gained traction in longevity practice, both as a standalone intervention and as a component of broader stacks. This article explains what GlyNAC is, what the Baylor trials showed, the precise dosing protocol used, the supplement options, and how to integrate it.
Glutathione is the body's most abundant intracellular antioxidant, critical for detoxification, cellular redox balance, and mitochondrial function. Glutathione is synthesized from three amino acids: glutamate, cysteine, and glycine. Cysteine availability is typically the rate-limiting step in younger adults; glycine becomes increasingly limiting in older adults.
Older adults have substantially lower glutathione levels and reduced glutathione synthesis capacity. The Baylor team hypothesized that providing both rate-limiting precursors — cysteine (as NAC) and glycine — would restore glutathione synthesis to younger levels.
NAC alone provides cysteine but does not address the glycine bottleneck. Glycine alone provides glycine but doesn't address potential cysteine limitations. Combined, the two amino acids correct both bottlenecks simultaneously.