Black tea gets the green light

The good old cup of English tea is presenting scientists with a chemical mystery which may well have a happy ending.

Until now nutritionists have dismissed black tea, used mostly in European brews, as non-beneficial to human health.

But now scientists at Surrey University have found evidence that the British "cuppa" could have cancer preventing properties at least as good as those of green tea, which is traditionally used in oriental brews. Green leaves become black through a process of crushing and fermentation.

Mike Clifford, reader in food science, said: "The average tea consumption in the UK is about three and a half cups a day. But we don't know what is in it."

Brewing up gallons of tea at a time, researchers have removed substances they know about, such as caffeine, flavanols and flavonols, and are working to identify the remaining substances, which they have called thearubigins.

The team is trying to further isolate structures from within the thearubigins. They have already found a completely new family of canary yellow pigments.

"We have no idea if these theacitrins as we have called them are of biological significance," said Dr Clifford. "They are quite exciting in isolation, structurally different from other pigments.

"We are beginning to form ideas about the thearubigins," he said. "There might be up to half a dozen unique families of pigments in these. Crude thearubigins are anti-mutagenic and protective in much the same way as components from green tea. So far as we can tell it is wrong to say that only green tea is good. The English cup of tea should not be dismissed."

See Perspective, page 13