Title: Tea as an antioxidant
Key words: heart disease, cancer, cataracts, black tea, antioxidants, flavonols
Date: April 2001
Tea as an antioxidant
If you want to avoid heart disease, cancer and cataracts, drink tea. That's the message from British researchers who have studied the health-giving potential of nine beneficial substances in black tea. Known as flavonols, these chemicals mop up oxidising agents which can otherwise damage the body's tissues.
Earlier this year, Michael Graziano and his colleagues at the Brigham and Women's Hospital in Boston found in a study of 680 people that those who drank black tea had a 44 per cent reduction in the risk of heart attack compared to non-tea drinkers (American Journal of Epidemiology, vol 149, p 162).
Now, Gary Williamson, Geoff Plumb and Keith Price of the Institute of Food Research in Norwich have probed some of the flavonols that might explain these effects. They studied six common varieties, including Lapsang Souchong, Assam and Darjeeling, and found that all are rich sources of flavonols. "Tea is the best source of these compounds in the British diet," says Williamson.
The nine flavonols investigated by the Norwich team are all chemically related to either quercitin or kaempferol, substances that protect tea plants from injury and infection.
To gauge their potency as antioxidants, the researchers measured each flavonol's capacity to prevent oxidation of standard test compounds. In the journal Redox Report (vol 4, p 13) they say that the five most potent antioxidants are variants of quercitin. Each carried between one and three sugar units-and the fewer the sugars, the better the antioxidant activity.
The next job is to investigate how well each flavonol is digested and absorbed in the gut.
From New Scientist magazine, vol 163 issue 2195, 17/07/1999, page 5
© Copyright New Scientist, RBI Ltd 2000