Your body's master antioxidant crashes after 40 — and most supplements can't fix it

The antioxidant your body makes — and stops making

Most people are familiar with antioxidants as something you get from food — berries, dark chocolate, green tea. But the most powerful antioxidant your body uses isn't something you eat directly. Glutathione is synthesised internally from three amino acids (glycine, cysteine, and glutamate), and it operates on a different scale from dietary antioxidants: it directly neutralises reactive oxygen species, regenerates vitamins C and E, supports liver detoxification, and modulates immune function. The problem is that glutathione synthesis drops significantly after your late thirties, and oral glutathione supplements have notoriously poor bioavailability — they're largely broken down in the digestive tract before reaching the cells.

Why the precursor approach works better

If you can't effectively supplement glutathione directly, the alternative is to supplement its building blocks. Glycine and N-acetyl cysteine (NAC) are the two rate-limiting precursors for glutathione synthesis — meaning they're the bottleneck. When you provide both in combination, the cells have what they need to produce more glutathione endogenously. This precursor strategy has been validated in human studies, with measurable increases in intracellular glutathione levels observed at clinically relevant doses.

GlyNAC: the combination that restores what age reduces

Aeternum's GLYNAC Powder combines glycine and NAC in a balanced ratio designed for daily supplementation. The powder format allows easy mixing into water, juice, or smoothies, and delivers a precise dose without the absorption limitations of encapsulated glutathione. Beyond glutathione, the GLYNAC combination has shown additional effects in published research: improved mitochondrial function, reduced markers of inflammation, better cognitive performance in older adults, and faster muscle recovery post-exercise. It's a compound intervention that targets multiple aging pathways simultaneously through a single mechanism.

Practical use

One scoop of GLYNAC powder daily, preferably in the morning, is the standard protocol. Effects on energy and recovery are typically noticeable within 4 to 8 weeks. Those with higher oxidative load — regular exercisers, smokers, people under chronic stress, or anyone with significant environmental exposures — tend to see the most pronounced response. The powder can also be taken post-workout, as NAC has well-documented benefits for exercise-induced oxidative stress.

The bottom line

Glutathione depletion is one of the most consistently observed features of biological aging, and it's one that most people are entirely unaware of. Restoring it through precursor supplementation is one of the more scientifically validated strategies in the longevity toolkit. If you're prioritising cellular health and immune resilience as you age, addressing glutathione is a logical first step.