Sunday, February 1, 2009

A Cup Of Green Tea

You have to imagine it –a steaming, fragrant cup of green tea. The clear, pale green liquid gives off a delicious aroma somewhat like wet hay mixed with the scent of apples or pears. You lift the cup to your lips and take the first sip. The comforting liquid rolls over your tongue and eases down your throat, brightening and warming as it goes. Its slight astringency freshens your mouth, making it feel naturally clean. This warm, delightful beverage is soothing, especially if you take a moment to sit and sip it slowly. But at the same time, it’s also stimulating, giving you a much needed pick-me-up in the morning or the middle of the long afternoon. Is it any wonder that tea has been enjoyed for nearly 5,000 years – and that it’s the world’s most widely consumed beverage, next to water?

Yet green tea is a lot more than just a delicious and satisfying drink -- it also has medicinal properties that are nothing short of amazing. Way back in the year 1211 the Japanese monk Eisai wrote that "Tea is a miraculous medicine for the maintenance of health. Tea has an extraordinary power to prolong life." And today, scientific are confirming that what Eisai said may be true, finding that green tea can boost the immune system, inhibit the cancer process at virtually every stage, regulate cholesterol levels, assist in weight loss, fight free radical damage, and ward off viruses, fungi and food-borne bacteria. It also helps inhibit dental plaque formation, lower the risk of type 2 diabetes, slow cognitive decline, and may even help increase the lifespan. Virtually no other substance on earth can claim such a wide range of health benefits!

I’m Nadine Taylor, a Registered Dietitian with a great interest in the healing power of foods. I have been so impressed by the science behind green tea’s health benefits that I started collecting green tea studies and information about ten years ago and eventually wrote a book about it. My aim in this column is to bring that knowledge to you, explaining how green performs its health-promoting "miracles," telling about the fascinating history and customs of tea drinking, and revealing some interesting new tea tidbits. (Did you know that green tea extract can grow hair?) My articles and question-and-answer column will appear monthly, and I hope you’ll join me. And don’t forget to bring along a nice hot cup of green tea!
What is Green Tea, Anyway?

Green, black, oolong, herbal – what’s the difference? Well, first of all the word "tea" is correctly used only when it refers to leaves taken from the Camellia sinensis bush. And that means that herbal teas really aren’t tea – only green, black and oolong tea are the "real thing." That said, the way the Camellia sinensis leaves are processed will determine which of these three choices the end product becomes.
To make black tea, the freshly picked tea leaves must be fermented. Fermenting occurs when an enzyme in the tea leaf called polyphenol oxidase combines with oxygen, so the leaves are left in the sun to wither and dry for 18-24 hours, then broken up to encourage further fermentation.. Then firing the leaves stops the fermentation and dries them. Making oolong tea is similar, although the withering and fermenting processes are shorter, resulting in a partially-fermented leaf. But to make green tea the leaf isn’t fermented at all – in fact, just the opposite! The tea leaves are steamed almost immediately after picking in order to stop the fermentation process, after which they are rolled and dried.
The health benefits of the resulting tea will largely be determined by whether or not the tea leaf has been fermented. The fresh tea leaf contains large amounts of catechins (pronounced "CAT-i-kins"), powerful disease fighters and potent antioxidants that give green tea its health-enhancing abilities. But when exposed to air and polyphenol oxidase, the catechins change into completely different compounds called theaflavins and thearubigens. The theaflavins and thearubigens, which give black tea its distinctive taste, aroma and dark color, do have some health benefits, but not the same wide-ranging antioxidant and disease-fighting prowess seen in the catechins.

So in green tea manufacturing, it’s extremely important to rush the freshly picked leaves from the field to the manufacturing plant, being careful not to break or bruise them. There, the leaves are steamed or pan-fired immediately to inactivate the polyphenol oxidase. Afterwards, it’s safe to roll, twist, dry and package the leaves without worrying about obliterating the catechins. Yet even after the manufacturing process has been completed, green tea catechins can be destroyed if exposed to oxygen for too long. That’s why you should always keep your green tea in an air-tight container, even if it’s already in tea bag form. Remember: oxygen is the catechins’ worst enemy.

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