What green tea actually contains
Green tea is the most studied tea in the world, and the most overclaimed.
The gap between those two facts is where this subject gets confusing.
A dried green leaf is roughly 30 to 40 percent polyphenols by weight.
Most of that is catechins, and the best known of them is EGCG.
Caffeine sits at 3 to 4 percent, and free amino acids at around 2 percent.
L-theanine is the amino acid that matters here, and it is rare outside tea.
It is the reason a cup feels calmer than its caffeine figure suggests.
Everything else in the leaf is present in smaller or less interesting amounts.
Those numbers describe the dry leaf, and they are not what reaches the cup.
Extraction depends on water temperature, steeping time and the ratio of leaf to water.
A cup brewed at 80 °C for 2 minutes pulls a fraction of what the leaf holds.
The remainder stays behind in the leaf and goes into the compost.
Any claim that starts from the dry leaf and skips that step is not a claim about tea.
What has been measured in people
Two kinds of work get quoted, and they are not equally useful.
Cohort studies follow large groups for years and record what happens to them.
Japanese and Chinese cohorts have repeatedly reported lower cardiovascular risk among regular drinkers.
The associations are consistent, and they are modest.
A cohort cannot separate the tea from everything else those people did.
Regular drinkers in those studies differ in diet, income and other habits.
Randomised trials are the other kind, and there are far fewer of them.
Most of them use extracts rather than brewed tea, at doses no drinker reaches.
One trial might deliver 500 mg of EGCG a day in capsules.
Matching that from a pot would mean drinking most of it, every day.
Where trials do use brewed tea, the measured changes are small and often not significant.
The honest reading is that green tea is pleasant, mild and safe.
It is not the agent of change that the packaging describes.
Both kinds of work get quoted as though they said the same thing.
Where the claims outrun the evidence
The claims that travel furthest are the ones with the least behind them.
Body composition is the clearest example, and the effect is real but tiny.
Reviews of catechin trials find average differences measured in fractions of a kilogram.
That is across months, and it is smaller than most people would ever notice.
The antioxidant language is the second problem, and it is mostly empty.
A catechin behaves as an antioxidant in a test tube, and that says little about a person.
The word survives in marketing because it sounds technical while meaning nothing specific.
Cleansing claims are the third, and they have no content in either tradition.
No old text makes them, and no trial supports them.
The disease claims are the fourth, and they are the ones worth being firm about.
A drink is not a treatment, and green tea does not become one by being studied often.
Age is not evidence, and repetition across centuries changes nothing about that.
The pattern is always the same: a real measurement, stretched into a larger promise.
How to drink it without the marketing
None of this is a reason to stop drinking green tea.
It is a reason to buy it for the right reasons, which are taste and price.
Brew 3 g in 240 ml at 80 °C for 2 minutes, and drink it fresh.
The second and third infusions are usually better than the first.
Three or four cups a day suits most adults, and the number is not a target.
Drink it after food if your stomach objects to it on an empty morning.
Keep the last cup six hours before bed if sleep has ever been uncertain.
Buy from the current harvest, since green tea fades faster than any other category.
Store it sealed, cold and dark, and finish it within a few months.
Matcha is the same leaf ground up, and it delivers more of everything per cup.
That includes the caffeine, which surprises people who assume it is gentler.
Ignore any label that promises an outcome, and ignore the price that comes with it.
A good cup at a fair price is the whole benefit, and it is enough.
Freshness is worth more than any sentence printed on the tin.