🧬 Endogenous Glutathione Synthesis: The Role of NAC, Glycine, Glutamine and Selenium
The cell's main antioxidant — what it is built from and how to support it
Glutathione is one of the body's most important antioxidants. It is a tripeptide made of three amino acids: glycine, cysteine and glutamic acid. It protects cells from oxidative stress, participates in detoxification and supports immunity. Glutathione levels can decline with age and stress.
The body synthesizes glutathione itself — if it receives the needed "building blocks": cysteine (or its precursor NAC), glycine and glutamine, plus selenium as a component of the enzyme that uses glutathione. Let's look at the role of each.
What is glutathione and why it matters
Glutathione is a tripeptide present in every cell at high concentration. Its main functions:
Protection from radicals
Neutralizes reactive oxygen species and regenerates other antioxidants.
Neutralization
Participates in binding and removing toxins and heavy metals.
Cell support
Needed for immune cell function and division.
Metabolism
Participates in metabolism and redox balance regulation.
How the cell synthesizes glutathione
Glutathione synthesis is a two-step process involving enzymes. It needs three amino acids: cysteine, glycine and glutamic acid. The limiting step is most often cysteine availability.
| Step | What happens |
|---|---|
| 1 | Glutamate binds to cysteine (enzyme GCL) |
| 2 | Glycine is added (enzyme GS) — glutathione is formed |
NAC: a source of cysteine
N-acetylcysteine (NAC) is a form of the amino acid cysteine with an acetyl group. It is well absorbed and serves as a precursor of cysteine, needed for glutathione synthesis. NAC is also used as a mucolytic.
Glycine and glutamine
The other two "building blocks" of glutathione are glycine and glutamic acid (glutamine). With sufficient cysteine, their deficiency can also limit glutathione synthesis.
Selenium and glutathione peroxidase
Selenium is an important trace element that is part of the enzyme glutathione peroxidase. This enzyme uses glutathione to neutralize peroxides. Without sufficient selenium, the antioxidant function of glutathione is not fully realized.
Food sources
What gives the body "building blocks" for glutathione:
| Component | Sources |
|---|---|
| Cysteine | Meat, eggs, chicken, cottage cheese, legumes |
| Glycine | Collagen, meat, fish, legumes |
| Glutamine | Meat, fish, dairy, legumes |
| Selenium | Brazil nuts, tuna, eggs, meat |
Practical conclusions
How to support glutathione levels:
Complete protein
Meat, eggs, legumes provide cysteine, glycine and glutamine.
Adequate selenium
Brazil nuts, fish, eggs — for glutathione peroxidase function.
NAC if needed
As a cysteine precursor — as agreed with a doctor.
Lifestyle
Sleep, moderate exercise and stress reduction support the antioxidant system.
What is glutathione?
A tripeptide of glycine, cysteine and glutamic acid. The main intracellular antioxidant.
What is glutathione synthesized from?
From three amino acids: cysteine, glycine and glutamic acid. Cysteine usually limits it.
Why is NAC needed?
NAC is a cysteine precursor, the limiting "building block" of glutathione. It helps support its synthesis.
Can glutathione be taken directly?
Direct oral glutathione is poorly absorbed. Precursors (NAC, glycine) and selenium are more effective.
Why is selenium needed for glutathione?
Selenium is part of glutathione peroxidase, which uses glutathione to neutralize peroxides.
How to raise glutathione levels?
Complete protein, adequate selenium, if needed NAC and glycine, a healthy lifestyle.
Which foods provide cysteine?
Meat, chicken, eggs, cottage cheese, legumes.
Why do glutathione levels decline with age?
Because of rising oxidative stress, reduced synthesis and possible shortage of precursors and selenium.
Is NAC safe?
Generally yes, but it is an active substance; may affect some drugs. Discuss intake with a doctor.
Is glutathione a supplement?
There are glutathione supplements, but their absorption is limited. Better to support synthesis with precursors.