Green Tea offers a Healthy Brew

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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.

The key is catechins, a specialized group of polyphenols that
gives green tea its astringent flavor and confers many of its
health benefits by serving as antioxidants, antiseptics and
detoxifiers. Green tea, the best dietary source of catechins,
contains at least eight types, mainly epigallocatechin gallate and
epigallocatechin. Compared to 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.

NOT ALL GREEN TEAS ARE EQUAL

Almost 90 percent of green teas are from China, but types from
Japan and elsewhere also are popular. While all green teas are of
the species Camellia sinensis, differences in origin and processing
create many varieties.

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. The best known is a tea
from China’s Zhejiang province, Lung Ching, 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 varieties 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 taste
harsher and less complex than the more expensive varieties. This is
especially true of gunpowder tea.

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 (Senchas
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?

BREWS FOR HEALTH

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

A tea’s harvest time is a strong indicator of its catechin
levels. Teas harvested in early spring are the richest in
catechins. As the season progresses, 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, producers sometimes allow Chinese green teas to
wither in sunlight for dehydration and softening, prior to heating
them to sterilize and inhibit fermentation. Then the tea is rolled
and dried. Japanese teas are not withered but are steamed at about
212 degrees right after harvest 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.

Rolled tea leaves release their nutrients more readily during
infusion than unrolled types because rolling breaks up the
structure of the tissues. 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.

To brew bud, leaf or powdered teas, connoisseurs traditionally
shun boiling water because the resulting brews are considered too
astringent. The recommended water temperature is between 165 and
185 degrees though gyokuro teas typically are brewed at about 140
degrees. Amino acids dissolve in water at 140 degrees, but
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 catechins, use hotter water. When making iced
tea, infuse the hot water for extraction, then chill the brew over
ice.

Caffeine levels vary 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. Caffeine in green tea, though considered low at 11 to
20 mg per cup versus 120 mg per cup for coffee, still may be
problematic for some people. And powdered green tea, such as
matcha, while permitting better absorption of catechins by the
body, can concentrate caffeine. If a decaffeinated tea is desired,
consider those decaffeinated by the 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.

For those worried about pesticides, organic green teas are
available. Chinese teas especially have been a concern because of
pesticide use in some regions. China is now working to produce more
teas that satisfy organic guidelines of nations such 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.

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).

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