Theaceae
Camellia sinensis
Tea · Green tea · Black tea
- Part used
- leaf
- Native range
- Southwestern China, northern Myanmar and northeastern India
- Morphology
- An evergreen shrub or small tree, kept pruned to waist height in cultivation. Green, black, oolong and white tea are all this one species, differing only in how the picked leaf is handled.
- Also known as
- Thea sinensis
What is in it
Evidence
Enormously studied and persistently disappointing at the level of hard outcomes. Population studies associate tea drinking with modest cardiovascular benefit; trials of concentrated extracts for weight loss and cancer prevention have not delivered. Caffeine content accounts for much of the acute effect.
Safety
Tea as a drink is uncontroversial. Concentrated green tea extract is a different matter and is now among the most frequently identified causes of herb-induced liver injury in Western case series, with a recognised idiosyncratic hepatotoxicity that appears unrelated to dose. Tannins reduce non-haem iron absorption, which matters for anyone iron-deficient.
Interactions: Vitamin K content interacts with warfarin; Caffeine adds to other stimulants; Reduces absorption of iron and of some drugs taken at the same time
Regulatory: Permitted as a food. Extract products carry warning requirements in several jurisdictions including the EU.
How the traditions classify it
Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.
Historical use
Drunk in China for well over two thousand years, first as a medicinal decoction and then as an everyday beverage; carried to Japan by Buddhist monks, and to Europe in the seventeenth century. Traditional medicinal uses centre on alertness, digestion and headache.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Tea is in this collection to make one point, and it is a point about concentration rather than about tea.
Nobody has ever been hospitalised by drinking it. Green tea extract capsules put people in liver units. The plant did not change; the preparation did. That gap — between the leaf in hot water that a tradition actually used, and the standardised concentrate sold on the strength of that tradition — is where a large share of modern herbal harm now sits.
Nomenclature verified against GBIF backbone taxonomy.