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General Health Articles
Tea & Its Health Benefits
All true tea comes from one species of plant, Camellia sinensis, an evergreen bush that grows in tropical and subtropical climates. The Chinese claim the first cultivated tea plant, about 3,200 years ago and a Chinese legend claims the discovery of tea over 4,700 years ago. Even in ancient times it was claimed as a cure for a variety of illnesses and medical conditions.
Black tea was an expensive commodity for thousands of years, and was compressed into bricks to be shipped throughout China and used in trade. At one time it became a kind of currency in other Asian countries trading with China.
Besides China, tea is has a long history of growth and cultivation in India and Sri Lanka (formerly Ceylon, as the type of tea is still called). It is also grown in Kenya, Turkey, Indonesia, Thailand and Taiwan.
Tea was originally very expensive when introduced to western Europe at the end the 17th century, but by the middle of the 18th century is was almost universal, especially in Britain. It was believed to have health properties then too, and the used leaves were even consumed with butter on toast. The earliest tea in Europe was green, and occasionally fermented, but black tea didn't become universal until the 19th century.
Different kinds of tea are made by using different processing methods, different parts of the leaf, and different harvesting times. The minute the leaf is picked it begins to oxidize. When this happens the chlorophyll releases tannins, which make the flavor stronger. This can be stopped by heating the leaves. The flavor of the tea can be further controlled by the length of time the leaves are allowed to oxidize, whether or not they're allowed to wilt before processing, and whether or not they're bruised, like mint leaves in iced tea, to make the flavor stronger.
Types of tea
• White tea is made from the smallest tip of the leaves, and is the most minimally processed of all teas. It is allowed to wilt slightly which makes it taste less grass-like. When brewed, the liquid can retain tiny hairs which float on the surface. It has the same health benefits as green tea (below). White tea has a long tradition of use in China and is graded into at least five categories, partly depending on variety and when it is harvested. Additionally, white tea is often brewed several times (3 is best) in China, allowing more time for each additional brewing. It is essential not to pour boiling water onto white tea leaves as this makes it bitter. The water should be about 180 °F.
• Green tea is made from leaves that have not been allowed to wilt or oxidize. Because of its minimal processing, green tea possesses the highest concentration of beneficial compounds like polyphenols (see below). Gunpowder tea is a Chinese variety of green tea where the leaves are rolled into pellets to protect them from damage and preserve their aroma. Gunpowder is the variety used to make Moroccan/ North African mint tea.
• Oolong is made from partially oxidized leaves that have been allowed to wilt and then bruised. Its oxidation puts it roughly between green and black tea in strength and characteristics. There are 6 to 8 varieties, all processed slightly differently and with different flavors. Some varieties of oolong are roasted and some are aged. One really important characteristic of oolong is that multiple brews can be made from the same leaves, which often improve in flavor and aroma. This is the type of tea that most Chinese restaurants use.
• Black tea is made from leaves that have been allowed to wilt, are fully oxidized, and usually crushed. In China black tea is called Crimson tea because of the actual color. In east Asia, especially in Thailand, black tea is called red tea. Black tea is classed in four categories:
• whole leaf, which is made from whole leaves and some tips
• broken leaves, considered the second grade, often sold as loose tea
• fannings, the loose fragments of leaves left over after processing the above types
• dust, the smallest particles left after processing everything else and used mostly in tea bags because the particles make a fast, strong cup of tea
• Red tea is also the name for a non-tea product made from the Rooibos plant, native to South Africa. It is also called South African red tea (see section on Herbal Infusions). Like tea, it contains antioxidants, but doesn't have caffeine. In traditional medicine in South Africa it is used to treat skin problems, indigestion and allergies.
• Herbal teas are not really tea at all because they're not made with leaves from the Camellia sinensis plant, but are infusions made from various plants often with long histories of folk remedy use. (See section on Herbal Infusions.) They are often made with other parts of the plant besides the leaves, including seeds, roots, stems, berries and flowers.
• The caffeine level of tea depends on the type, but tea has more caffeine than coffee if judged by weight; however much less tea is used than coffee when making a cup, which ends up meaning that drinking tea gives you less caffeine
• Tea also has a small amount of theobromine, a stimulant similar in nature to caffeine and also found in the cocoa bean
• The polyphenols and other beneficial compounds in tea are released by the heat of the water used to make tea (see Preparation below)
Blends and additions
• Many commercially marketed teas are blended, some at the place where they are grown, and others by importers. This keeps certain brands consistent by controlling strength and flavor as well as aroma.
• Additives can change the flavor of tea mildly or very strongly; for example, the addition of bergamot makes what is called Earl Gray; also jasmine is often added to green tea.
• Chai in North America refers to a spiced black tea, but in many other countries it is the word for tea. This is also true in some European countries where chai is used as an alternate or slang word for tea.
• As a rough guide, steamed and less-processed teas like green and white have more epigallocatechin gallate (EGCG) and other catechins, while dried, fermented and roasted teas like black tea, have more polyphenols like theaflavins and thearubigens.
• Recent research suggests that a compound in all tea, epigallocatechin gallate (EGCG), works with enzymes that control cell growth to hinder and sometimes stop certain types of cancer. It does this by controlling an enzyme that allows cancer cells to develop. EGCG is most concentrated in green tea because it is oxidized when black and other teas are processed. However, milk proteins attach to EGCG and stop it from having any effect.
• Research suggests that compounds found in black tea like theaflavins and thearubigens, both polyphenols with antioxidant properties that are created by the fermentation process, are equally beneficial. Studies suggest that theaflavins and thearubigens have an anti- dementia effect as well as interfering with HIV replication.
• A Dutch study suggested that men who drank black tea were at a lower risk for stroke, but significant protection came from drinking more than 4 cups a day.
• A study at the Boston School of Medicine showed that black tea also improved blood vessels.
• Research indicates that green tea protects a molecule called the aryl hydrocarbon receptor (AH) which, when interfered with by toxins from tobacco smoke and other sources, initiates cancer growth.
• Green tea is especially high in certain polyphenols, of which flavonoids are one type. They are thought to be effective against gastrointestinal tract disorders including colon cancer, as well as having antimicrobial properties.
• Studies suggest that green tea is strong enough to kill the bacteria that cause tooth decay as well as some of the bacteria that cause food poisoning.
• The National Cancer Institute published a study in 1994 showing that green tea reduced the risk of esophageal cancer in a study done in China.
• Other research shows that the polyphenols in green tea can reduce LDL cholesterol.
• Many of the health benefits have been noted in people who consume large amounts of green tea on a daily basis, but it is important to note the amount of caffeine in large doses of any tea.
• A study done at Boston University (2001) suggested that drinking black tea can reverse vein shrinkage in people with coronary artery disease.
• All tea has flavonoids, a type of polyphenol, which are strong antioxidants. Some researchers believe that these antioxidants, again most concentrated in green tea, are stronger than those in garlic and broccoli, and stronger than beta-carotene.
• It is possible that these flavonoids also protect DNA from damage by free radicals, and inhibit tumor growth.
• One flavanoid, catechin, is most concentrated in white and green teas.
• Tea also contains theanine, an amino acid derivative that helps reduce stress, both mental and physical, usually in conjunction with caffeine, and also has been shown to increase dopamine levels in the brain.
• Some research has suggested that the theanine in tea might also reduce the harmful effects of free radicals caused by glutamate, an excitotoxin.
• Another study suggests that theanine may also boost the immune system by increasing the strength of the white blood cells that fight infection.
• Green tea has been suggested as treatment for rheumatoid arthritis.
• Tea contains vitamins C, E and K
• Decaffeinated tea loses some of the polyphenols that make it healthy, but it depends on the process that is used. Chemical treatment by ethyl acetate destroys about 70% of the polyphenols, whereas a slower process called effervescence, involving water and carbon dioxide, keeps over 95%. If using a decaffeinated green tea for health reasons, make sure the product you're using is not chemically treated.
Preparation: making tea
For thousands of years it has been brewed in basically the same way, with boiling or very hot water. This creates what is referred to as the liquor, which is the basis for all other forms of tea used as a beverage. Herbal teas are not teas at all, but infusions of herbs, often with spices, and are an important source of natural remedies in their own right.
• Heat releases the compounds that make tea beneficial, so boiling water is essential (except for white tea).
• Tea is universally understood to be served hot, as it has been for several thousand years, and is only qualified when something is done later, for example adding ice to make iced tea. Ready-made mixes for iced tea require so much processing that the health benefits have been reduced considerably, so it is best to make real tea correctly and then ice it after it cools.
• The quality of the tea determines the length of time it should steep: high quality teas will only release their complex flavors when steeped 8 to 12 minutes, depending on type, and will not become bitter (because of tannins) or over-caffeinated. Lesser quality teas need 1 to 3 minutes and will develop bitterness and high caffeine concentrations quickly.
• Milk proteins, like casein, attach to EGCG (see above) and almost stop the beneficial effects completely, so if you're drinking any kind of tea for health reasons don't use milk or dairy-based substitutes.
• Sun tea, made by putting tea bags or leaves in a glass container in direct sunlight, does not achieve the correct temperature to fully release the polyphenols and other compounds that give tea its healthy properties. It also does not get hot enough to kill bacteria that is sometimes present in water.