Green tea

Cammellia sinensis

Green Tea-the prepared leaves and leaf buds of Camellia sinensis (L.) O. Kuntze (family Theaceae), a large shrub with evergreen leaves native to eastern Asia and extensively cultivated there. Black tea is prepared by an initial slow drying of the fresh leaves that allows them to begin to ferment. For green tea, a less popular beverage in the United States, the leaves are quickly dried. Because of these different methods of preparation and the many different varieties of the cultivated plant, the average caffeine content of tea ranges widely, from about 1 to more than 4 percent.

Green Tea drinking in some Asian countries has evolved into quite a delicate art, much as wine sampling or tasting has done in France. There are connoisseurs of finely brewed tea, who can tell what type of water was used, what kind of utensils were involved and the approximate conditions under which a particular tea is made. In mainland China, some teas are so incredibly strong to the palate that they're served in (literally) thimble-sized cups. Black and green teas both contain caffeine (1-5%). Since caffeine constricts the blood vessels in the head, it's able to calm the pain caused when they throb and swell.

University of California scientists have discovered that tea drinkers experience a lot less hardening of the arteries than coffee drinkers do. It seems that the caffeine in coffee is bound with some heavy oils, which tend to elevate serum cholesterol levels quite a bit. But not so with either dark or green teas. In fact, it's believed that the caffeine content in both teas may actually help to cut cholesterol somewhat. Besides this, the tea's polyphenols act in concert with the vitamins C and P present, helping to strengthen the blood vessel walls of the heart.

Green Tea (Camillia sinensis), evergreen shrub, related to the camellia; also, the leaves of the plant and the beverage made from the leaves. The drink is prepared by pouring boiling water over dry processed tea leaves. Types of tea drunk include green, black (which is fermented), and oolong (which is partly fermented). Tea has been drunk in China since early times, but it was not until the early 1600s that the Dutch introduced it into Europe. Although expensive, it soon became fashionable. In the United Kingdom and the British colonies, the East India Company enjoyed a monopoly of the China tea trade until 1833; it was the attempt of the British government to levy a tax on tea imports into the American colonies that led to the Boston Tea Party of 1773. Today, the chief producers are India and Sri Lanka (Ceylon). Tea contains the stimulant caffeine. The term tea is also used to describe many other local drinks produced from the leaves of a vast array of plants.

Parts used

Leaves and buds.

Uses

Tea is useful in treating infections of the digestive tract. In Ayurveda, tea is considered astringent, sweat-inducing, and a nerve tonic, and is used for eye problems, hemorrhoids, tiredness, and fever. Tea leaves may be used  externally to soothe insect bites and sunburn.

Habitat & cultivation

Cultivated principally in India, Sri Lanka, and China, tea has been grown since the earliest times.

Research

Research-in China suggests that green tea can help hepatitis. Research in Japan in 1990 showed that tea contains constituents that inhibit tooth decay.

How much to take

Much of the research documenting the health benefits of green tea is based on the amount of green tea typically drunk in Asian countries-about three cups per day (providing 240-320 mg of polyphenols). To brew green tea, 1 teaspoon of green tea leaves are combined with 250 ml (1 cup) of boiling water and steeped for three minutes. Tablets and capsules containing standardized extracts of polyphenols, particularly EGCG, are available; some are decaffeinated and provide up to 97% polyphenol content-which is equivalent to drinking four cups of tea.

Side effects

Green tea is extremely safe. The most common adverse effect reported from consuming large amounts of green tea is insomnia, anxiety, and other symptoms caused by the caffeine content in the herb.

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