Glutathione peroxidase

Enzyme

What is it

Glutathione peroxidase (GPx) is a family of selenium-dependent antioxidant enzymes that reduce hydrogen peroxide and lipid peroxides using glutathione as a reducing agent. It is sometimes included in supplements as a 'preformed' antioxidant enzyme, though oral supplementation has questionable efficacy.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Antioxidant support

Mixed Evidence

Oral GPx enzyme supplements are unlikely to deliver intact functional enzyme. Supporting endogenous GPx via selenium and glutathione precursors is the practical approach.

How it works

Endogenous GPx is critical for cellular antioxidant defense, working alongside glutathione, catalase, and superoxide dismutase. Activity depends on selenium availability, as selenium forms the active site (as selenocysteine) of most GPx isoforms. Orally administered GPx enzyme is largely denatured and digested in the stomach and small intestine, releasing amino acids rather than functional enzyme. Supporting endogenous GPx activity through adequate selenium intake and glutathione precursors (NAC, cysteine) is more practical than supplementing the enzyme itself.

Dosage

No established RDA for GPx as a supplement. Selenium RDA: 55 mcg/day adults. GPx-rich algae extracts (e.g., from spirulina) are sometimes used as supplement sources.

When and how to take it

Not applicable as a standalone supplement. Support endogenous GPx through dietary selenium and glutathione precursors.

1 commercial form

Compare the main delivery options and what they’re best suited for.

GPx-containing extracts (e.g., algae)

Some supplements include these for marketing purposes.

Limited; enzyme likely degraded in GI tract

Safety

Oral GPx supplements are generally safe but of questionable utility. Adequate selenium intake supports natural GPx; selenium UL is 400 mcg/day.

Who should be cautious

People undergoing chemotherapy should discuss antioxidant supplementation with their oncologist. Selenium overdose can cause selenosis.

Interactions

Selenium status affects GPx; antioxidant supplements may have complex interactions with chemotherapy (timing-dependent).

Food sources

Brazil nuts (selenium for GPx synthesis)

Amount
1 nut = ~95 mcg selenium
%DV
173%

Seafood, meat, eggs

Amount
Variable selenium
%DV
—

Frequently asked questions

Can I supplement glutathione peroxidase?⌄

Direct oral supplementation is unlikely to be effective. Support your body's own GPx via adequate selenium intake and glutathione precursors.

How do I boost my body's glutathione peroxidase?⌄

Ensure adequate selenium (55 mcg/day RDA, easy with 1-2 Brazil nuts or seafood) and consider NAC or whey protein for glutathione precursor support.

References

Glutathione peroxidase on Wikidata — Wikidata link

Glutathione peroxidase on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Glutathione peroxidase (PubMed search) — PubMed link

Track Glutathione peroxidase with Pilora

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.