Green tea, black tea, oolong tea, even white tea - they all come from the same tea plant, Camellia sinensis. What is the difference between them is the processing. Green tea leaves are not fermented, but withered and steamed. Black tea and oolong tea leaves undergo a crushing and fermenting process, although oolong leaves are fermented only half the time compared to black tea leaves. White tea is made of buds and young leaves only and is only steamed.
Green tea has been well studied for its health benefits, but it turns out that black tea is also very healthy.
BOTH green AND black teas by one estimate have 10 times the amount of antioxidants that are found in fruits and vegetables. John Weisburger, PhD, senior researcher at the Institute for Cancer Prevention in Valhalla, N.Y., was the first American researcher to show that tea modifies the metabolism to detoxify harmful chemicals. He states that whether green or black, tea has about eight to ten times the polyphenols, a type of antioxidant, found in fruits and vegetables. Both types of tea blocked DNA damage associated with tobacco and other toxic chemicals. In animal studies, tea-drinking rats have less cancer.
A study in the Netherlands found a connection between regular consumption of black tea and reduced risk of stroke. Researchers concluded that the health benefits of black tea include the reduction of LDL - the type of cholesterol that can lead to stroke and heart attacks. They also found that men who drank over four cups of black tea per day were at lower risk of stroke than men who drank only two to three cups per day.
Another study in Saudi Arabia showed that regular consumption of black tea can reduce the risk of coronary heart disease by fifty percent. A four month study in the US concluded that black tea helped to reverse an abnormal functioning of blood vessels that can contribute to stroke or heart attack. This improvement could be observed within two hours of drinking just one cup of black tea!
A study at the Charite Hospital of the Berlin Universities showed that adding milk to tea (black or green) will block the normal, healthful effects that tea has in protecting against cardiovascular disease. Casein, a protein from the milk, binds to the molecules in the tea that causes the arteries to relax. Milk may also block tea's effect on other things, such as cancers. So the British habit of adding milk to tea is not really a healthy idea.
Studies, including a study from Purdue University in 2007, found that most of the antioxidant catechins are not absorbed into the bloodstream when tea is drunk by itself. The study found that adding citrus to the tea lowers the pH in the small intestine and causes more of the catechins to be absorbed. So squeeze a little lemon in that cup of tea, whether black or green (or oolong or white).
And what about Rooibus Tea? Well, that one IS a different plant! And a different article...
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