Green Tea: Catechins and Its Health Benefits

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Green tea offers a satisfying array of delicious choices, but are they all equal in catechin content?
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Green tea has taken the Western world by storm. Once a favorite of Asian peoples alone, this ancient beverage now charms Westerners alike. As a health brew, green tea may inhibit several types of cancers; delay age-related cancer onset; boost immune function; reduce LDL cholesterol, blood sugar and risk of stroke; curb severity of rheumatoid arthritis; alleviate pain; and combat tooth decay.

It’s all about catechins, a specialized group of polyphenols. Catechins give green tea its astringent flavor and likely confer many of its health benefits by serving as antioxidants, antiseptics and detoxifiers. Green tea is the best dietary source of catechins and contains at least eight types, the major ones being epigallocatechin gallate and epigallocatechin. And unlike its fermented sisters, oolong and black tea, green tea retains more catechins—as much as 30 to 42 percent of dried leaf weight versus only 9 percent in black tea.

Different Kinds of Green Tea

Almost 90 percent of green teas are from China, but many from Japan and elsewhere also are popular. While all green teas are from the species Camellia sinensis, diverse types are available, depending on where they are grown and how they’re processed.

Chinese green teas include renowned names like Lung Ching, Pi Lo Chun, Mao Feng, Yin Zhen, Yun Wu, Mao Jian and Gua Pian. These regional teas are famous culturally for their individual leaf characteristics, color, aroma and flavor. Best-known is lung ching (or Dragon Well), from Zhejiang Province, whose flat leaf buds yield a pale jade tea with a floral aroma and fruity taste. Chinese teas range considerably in quality, but the most prized are those whose young leaves or leaf buds are plucked very early in spring and hand-rolled to final shape. Premium teas can cost more than $10 per ounce, lesser ones about $5.

More common Chinese green teas include Young Hyson, gunpowder and Chun Mee. Gunpowder and Young Hyson grades consist of leaves rolled into pellets, or twisted in a long thin style, respectively. These everyday teas typically cost less than $2 per ounce, and they are less complex and harsher in taste, especially gunpowder.

Flavored teas are a special treat. These teas bear the fragrance and flavor of jasmine, citrus, mint, rosebuds, vanilla and other botanicals. Chinese jasmine tea remains a favorite—the tea leaves are dried with jasmine flowers, which, when removed, leave behind a subtle fragrance and taste.

Japanese green teas are of two basic types: Sencha and Gyokuro. Sencha, composing 75 percent of Japanese production, is grown in the sun, while gyokuro is shaded a few weeks before harvest. Premium qualities use only the new spring leaves. Several teas are based on sencha, including an early-season tea called Shincha, a late-summer tea known as Bancha and a blend of sencha and toasted brown rice called Genmaicha. Bancha is a low-priced yellow tea with a brisk, harsh flavor. Genmaicha is also inexpensive, and its crispy, milder flavor goes well with meals.

Gyokuro makes a sweeter, darker-green tea than the grassy-flavored sencha and costs at least $5 per ounce (compared to senchas, which start around $2). Gyokuro also is the source for Matcha, the powdered tea used in the traditional Japanese tea ceremony. Matcha is ground from the soft inner gyokuro leaf, with stems and leaf veins removed. It should not be confused with ordinary powdered green tea, which is made from sencha and added to shakes, ice cream, breads and other foods.

Buds of either sencha or gyokuro can be used to make bud tea or Mecha, a hard-to-find yellow, aromatic infusion with a sharp, bitter aftertaste. The roasted stems and leaf stalks produce stalk tea or Kukicha, a reasonably priced tea with a nutty-woody aroma and mild, slightly astringent flavor.

A satisfying array of choices—but are they all equal in catechin content?

Getting the Healthiest Brew: Green Tea with Most Catechins

For beverage connoisseurs, the balance between astringency and sweetness is paramount, often at the expense of medicinal quality. Some tea varieties are being bred for lower content of the bitter polyphenols to enhance beverage appeal, but this may diminish tea’s health benefits. Catechins should be preserved throughout tea production, processing and brewing.

Teas harvested early in spring are the richest in catechins. As the season progresses, both catechins and sweetness-conferring amino acids decline, more so in unshaded teas such as senchas than in gyokuro teas. Late-harvested teas, such as bancha, are very astringent because they lose their amino acids more rapidly than catechins. Stalk teas are the lowest in polyphenols and other nutrients.

After harvest, Chinese green teas sometimes are allowed to wither in sunlight for dehydration and softening, prior to being heated to sterilize and inhibit fermentation. Then they are rolled and dried. Japanese teas are not withered but steamed at around 212 degrees right after picking to prevent fermentation, then rolled and dried. Hot-air withering may reduce polyphenols and other constituents because digestive enzymes are still active. Steaming better protects polyphenols, vitamins and amino acids, and helps retain a greener color.

Tea leaves that are rolled release their contents more readily during infusion than unrolled types. Rolling breaks up the structure of the tissues for easier release of contents. Teas that come as pellets, rolls or twists, and powdered forms may thus be good choices. Stalk tea must be simmered for several minutes in boiling water for proper extraction.

For bud, leaf or powdered teas, boiling water traditionally is shunned, because the brews are considered too astringent. Water temperatures between 165 and 185 degrees usually are recommended, while gyokuro teas typically are brewed at about 140 degrees. However, while amino acids dissolve in water at 140 degrees, catechins dissolve more readily at 176 degrees or higher, meaning much lower concentrations in cool-infused teas. Infusing longer than the usual two to three minutes has only a minor effect, so if you want the most catechin, use hotter water. When making iced tea, infuse with hot water for extraction, then chill the brew over ice.

Caffeine in green tea, while considered low at 11 to 20 mg per cup versus 120 mg per cup for coffee, still may be problematic for some. And powdered green tea, such as matcha, while permitting better absorption of catechins by the body, could concentrate caffeine. If a decaffeinated tea is desired, consider those from spring water or carbon dioxide methods, rather than ethyl acetate and methylene chloride, which can damage antioxidants. In Japan, decaffeinated green tea is almost unheard of except for a tea known as houjicha, which is bancha or kukicha pan-fried or oven-roasted for an agreeable, not-too-bitter taste. But houjicha, while low in caffeine, is unfortunately lower in catechins, amino acids and vitamins, too. Caffeine varies according to the part of the tea plant harvested. Teas from the buds and uppermost leaves have about four times the caffeine as in the lower stem, with a decreasing gradient in between.

For those worried about pesticides, organic green teas are available. Chinese teas especially have been a concern because of pesticide usage in some regions. China is now working to produce more teas that satisfy organic guidelines of such nations as the United States and the European Union. Organic teas from Japan and elsewhere also are available. Look for certification by a reputable organization, such as the Japan Organic & Natural Foods Association or another recognized body.

Drink Tea with Caution

Tea drinking can contribute to anemia in certain individuals. Tea polyphenols bind iron from such sources as plants, dairy products and iron supplements but not iron from meat, poultry and fish. Vegetarians are advised to drink tea at least one hour before or two hours after meals. Other effects of tea may include allergic reactions, nervousness, insomnia and interaction with the pharmaceutical blood-thinner warfarin.

Gina Mohammed, Ph.D., is a plant physiologist in Sault Ste. Marie, Canada. She is author of Catnip and Kerosene Grass—What Plants Teach Us About Life (Candlenut Books, 2002).

The reference list for this article is extensive. If you would like a copy, please send a self-addressed, stamped envelope to “Green Tea,” Herbs for Health, 1503 SW 42nd St., Topeka, KS 66609; or e-mail us at editor@herbs

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