Green and black tea come from the same leaf. The difference is oxidation. Green tea leaves are heated right after picking, which stops the oxidising enzymes and leaves the catechins โ especially EGCG โ intact.
Add to that L-theanine, an amino acid that is unusually abundant in green tea. Caffeine's alertness plus theanine's calm is why people describe green tea as a different kind of focus from coffee.
Key benefits
- 1
It nudges LDL cholesterol and blood pressure down
Pooled randomised trials show significant, if modest, reductions in total and LDL cholesterol with green tea, plus small drops in blood pressure. This applies to people drinking three or more cups a day consistently.
- 2
It produces focus and calm at the same time
L-theanine increases alpha wave activity in the brain, a state of relaxed alertness. Taken together with caffeine, it outperformed caffeine alone on attention tasks in trials. That is the source of green tea's steadier, less jittery lift.
- 3
It slightly increases fat oxidation
The EGCG-plus-caffeine combination modestly raises daily energy expenditure and fat oxidation. Over weeks, though, the weight-loss effect is small. Green tea supports a diet; it is not a method of losing weight.
- 4
It helps oral health
Catechins suppress the bacteria behind tooth decay, and the fluoride naturally present in tea benefits enamel. This holds for tea drunk without sugar.
How to eat it well
- Brew at 70โ80ยฐC. Boiling water pulls out too much bitterness from catechins and caffeine, and less of the savoury notes.
- Steep the first cup for one to two minutes. Longer gets astringent. The same leaves are good for two or three infusions.
- Three to five cups a day is the range most often used in research.
- Avoid strong tea right after a meal. Tannins interfere with the absorption of non-heme iron; between meals is better.
- Matcha means consuming the whole leaf, so both catechins and caffeine come in higher.
What to watch out for
- A cup contains 20โ45 mg of caffeine. If you are caffeine-sensitive or sleep poorly, skip it late in the day.
- Strong tea on an empty stomach can cause heartburn.
- With iron-deficiency anaemia, leave at least an hour between tea and meals.
- Concentrated green tea extract supplements have been linked to rare cases of liver injury. That risk is not the same as drinking the tea.
- In pregnancy, count cups against a total caffeine limit of about 200 mg a day.
Nutrition
Approximate values for one brewed cup (about 240 ml).
- Calories
- 2 kcal
- Catechins
- 50โ150 mg
- Potassium
- 20 mg
- Manganese
- 0.4 mg
Key nutrients
- Catechins
- Potassium
- Manganese