Tea | Research & Encyclopedia Articles

In the broadest sense, tea is a water extract of leaves, blossoms, roots, bark, or other parts of plants. The extraction can be done by soaking, boiling, and steeping (soaking in water below the boiling point). The extract can be an ordinary beverage or a medication.

The most common tea is from the leaves of the plant known as Camel-lia sinensis. Chinese legend attributes the accidental discovery (around 2700 B.C.E.) of drink made from this plant to King Shen Nong, who noticed tea leaves had blown into his kettle of boiling water. The tea that Shen Nong most probably drank is green tea, which quickly became the most popular beverage in China, Japan, Korea, and the countries of Southeast Asia. (Its popularity has continued, and in fact, tea brewed from Camellia sinensis is second only to water as the world's most popular beverage.) Unlike orange pekoe (a black tea, which is most identified as tea by consumers in the United States), fresh green tea beverage is tinted apple green, hence its name. Other teas from Camellia sinensis are broadly termed black, red, and yellow according to the appearance of either the dried leaf or its extract.

All Camellia sinensis teas are from the growing ends and buds (called the flushes) of the tea tree or shrub. Flushes that undergo a process called fermentation become black, red, or yellow teas. This process is not the one in

TEN LARGEST TEA-PRODUCING AND EXPORTING COUNTRIES, 1998
Principal Producers	Quantity Produced (in metric tons)	Quantity Exported (in metric tons)
India	870,400	225,000
China	687,675	219,325
Kenya	294,165	263,685
Sri Lanka	280,056	267,726
Indonesia	152,063	67,219
Turkey	120,300	17,526
Japan	91,000	752
Myanmar	66,808	N/A
Vietnam	51,000	33,000
Bangladesh	50,575	25,049
SOURCE: Food and Agriculture Organization of the United Nations.

which microbes are added to make alcohol-containing beverages, cheese, sauerkraut, and other foods. Rather, an enzyme (catalyst) changes molecules called polyphenols that are green into more complex polyphenols that are red and yellow. Both the enzyme and the polyphenols are in (and not added to) the tea leaf, and leaf fermentation is activated first by withering (slow drying of the leaves) and then by rolling (pressing the leaves so that the sap comes to the surface). Black tea is made when the fresh tea leaves are allowed to totally ferment (100 percent). Partial fermentation of 10 to 15 percent and 20 to 30 percent yields yellow and red (sometimes known as oolong) teas, respectively. Steaming or roasting the leaves to inactivate the enzymes soon after harvest prevents fermentation, and these are the first steps in green tea manufacture.

Tea has been called an elixir of life and is commonly used as an antidote to mental fatigue. This effect may in fact be caffeine-induced. Although there is less in tea than in coffee, enough caffeine is present in a cup of tea to dilate the brain's blood vessels. Tea seems to have a wide range of health benefits, as a survey of the scientific literature between 1998 and 2000 attests. The two principal active ingredients are the tea polyphenols (a group of six chemically and structurally related molecules) and theanine (an unusual amino acid found in green but not black tea beverage). (Amino acids are the building blocks of proteins.) Like vitamins C and E, the tea polyphenols are antioxidants that may slow the onset of atherosclerosis, some forms of cancer, and the onset and severity of arthritis. Nonantioxidant properties of tea polyphenols also may contribute to their overall effectiveness in disease prevention. Evidence is mounting to suggest theanine can help anti-cancer chemicals (such as doxorubicin) kill tumor cells more specifically, but how it does this is still unknown.

Worldwide tea production was over 3 million metric tons (worth about $8 billion to growers) in 1998. India and China produced about half of this output, most of it for internal consumption. Whereas China and Japan produce mainly green and partially fermented teas, the other growers supply mainly black teas. The world's largest importers of tea are the United Kingdom,

TEN LARGEST TEA-IMPORTING COUNTRIES, 1998
Principal Consumers	Quantity Imported (in metric tons)
United Kingdom	175,829
Russian Federation	150,225
Pakistan	111,559
United States	96,646
Egypt	65,457
Japan	45,442
Iran	40,000
Germany	38,664
Poland	36,569
Sudan	23,843
SOURCE: Food and Agriculture Organization of the United Nations.

the Russian Federation, Pakistan, and the United States. However, Ireland, the United Kingdom, Turkey, Syria, and Iran are the world's leading consumers on a per-capita basis.

The estimated wholesale value of the U.S. tea industry has risen from $1.84 billion in 1990 to $4.60 billion in 1999 and continues to rise, according to the U.S. Tea Association. The largest segment of that growth was due to the increased consumption of ready-to-drink teas, which rose from $0.2 billion to $1.65 billion dollars during this period.

Herbal teas, like regular tea, have been consumed for eons and for the same calming, stimulating, or medicinal reasons. Tea made from chamomile flowers steeped for more than thirty minutes in boiling water is said to be a sedative that also soothes indigestion. Tea made from the rootstock of comfrey was believed to heal broken bones and be a good gargle for sore throat and cure bleeding gums. Tea made from sassafras root bark or leaves may have the pleasant taste of root beer but will cause the drinker to perspire and urinate. This tea has been used for everything from a blood-thinner to a cure for rheumatism and syphilis. Indeed, teas can be made from many plants and may contain thousands of active compounds. The U.S. Food and Drug Administration recommends that herbal tea drinkers use caution. Chamomile can cause a severe allergic reaction in people with sensitivity to ragweed, asters, or chrysanthemums. Liver disease has been reported in drinkers of large amounts of comfrey tea (ten or more cups a day), and comfrey contains a chemical that causes cancer in rats. The major chemical components of sassafras tea, once used to flavor root beer, were banned thirty years ago because they caused cancer in rats. The use of caution means moderation—daily consumption of any particular herbal tea for not more than two to three days at a time—and avoidance—by children, pregnant women, or nursing mothers.

Coffee; Economic Importance of Plants; Herbals and Herbalists; Herbs and Spices; Medicinal Plants.

Gutman, Robert L., and Beung-Ho Ryu. "Rediscovering Tea: An Exploration of the Scientific Literature." HerbalGram 37 (1996): 33-48.

Snider, S. "Herbal Teas and Toxicity." FDA Consumer 25, no. 4 (1991): 30-33.

Tyler, Varro. The Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies. New York: Pharmaceutical Products Press, 1993.

Willson, Kenneth C., and Michael N. Clifford, eds. Tea: Cultivation and Consumption. London: Chapman & Hall, 1992.

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