Clear evidence. Transparent sources. Practical guidance. Our evidence policyContact
Food Health Lab
Home › Supplements › Antioxidants › Green tea (EGCG)

Green tea extract / EGCG

Concentrated catechins — mild metabolic perks, but a real high-dose liver caution.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsAntioxidantsMetabolicCaution

Green tea’s catechins, chiefly EGCG, are potent antioxidants. Brewed tea is wonderfully safe; concentrated extracts are a different story, and worth respecting.

Key takeaways

  • The active antioxidants are catechins, mainly EGCG.
  • Modest effects on fat oxidation and metabolic markers, often small and caffeine-dependent.
  • Brewed green tea is very safe; but high-dose extracts (≥800 mg EGCG/day, especially fasted) are linked to liver injury.1
  • If used, take with food and don’t megadose.

What it is

Green tea extract concentrates the catechins from Camellia sinensis. EGCG is the most abundant and biologically active, with antioxidant and mild metabolic effects.

The evidence

Human data show small effects on fat oxidation and cardiometabolic markers — real but not dramatic, and partly driven by caffeine. The more important story is safety: a European (EFSA) review concluded that catechin doses ≥800 mg EGCG/day can raise liver enzymes, with rare cases of serious liver injury.1

Dose & how to use

Keep to modest, food-accompanied doses; avoid fasted high-dose EGCG. For most people, drinking green tea is the safer way to get catechins.

Safety & who benefits

Stop and seek advice if you notice signs of liver trouble (dark urine, jaundice, abdominal pain). Avoid high-dose extracts if you have liver issues or take hepatotoxic drugs.

Bottom line: mild metabolic perks at most — and the concentrated extract deserves caution: take it with food, keep the dose modest, or just drink the tea.

References

Adult research summary for education, not a prescription. These are food supplements, not treatments for disease.

  1. EFSA. Scientific opinion on the safety of green tea catechins. EFSA Journal 2018. efsa.onlinelibrary.wiley.com

This article summarises nutrition science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.