In brief: Green tea comes from Camellia sinensis and contains catechins such as EGCG as well as caffeine. Brewed tea can fit a balanced diet, while concentrated extracts need separate safety consideration.
Brewed tea versus extract
| Form | Practical note |
|---|---|
| Brewed tea | Usually much lower catechin exposure |
| Matcha | More leaf material is consumed |
| Extract capsules | Can provide high EGCG doses |
| Low-caffeine tea | Often easier for sensitive people |
What affects flavour?
Hotter water and longer steeping usually extract more bitter substances and caffeine. A milder brew is often achieved with a shorter steeping time or a slightly lower temperature.
Caffeine and sleep
Caffeine can improve alertness but may also cause palpitations, restlessness or sleep problems. Sensitive people should limit green tea in the late afternoon and evening.
Extracts and liver safety
EFSA considers brewed green tea generally safe, while concentrated catechin supplements raise more concern; intakes at or above 800 mg EGCG/day have been associated with early signs of liver injury.[1]
FAQ
Is green tea a cancer treatment?
No. Laboratory findings on catechins do not establish a cancer treatment.
Is matcha automatically healthier?
No. It provides different amounts of leaf constituents and caffeine.
Can green tea affect iron absorption?
Yes, polyphenols can reduce non-haem iron absorption. In iron deficiency, leaving a gap between green tea and iron-rich meals is sensible.
Are extracts the same as tea?
No. Extracts can deliver much higher EGCG doses.
Conclusion
Green tea is primarily a beverage. Extracts deserve greater attention to dose, product quality and liver risk.
