By Dr. Mercola
Aside from pure water, green tea is arguably one of the
healthiest beverages around, with research pointing to
impressive health benefits for your heart, bones, weight,
vision, and even your brain.
Tea comes from the evergreen plant called Camellia
sinensis. It's the processing that gives it its color and
taste. For green tea, the leaves are unoxidized (not exposed to
oxygen), and this minimal processing may help to keep the
beneficial antioxidants intact.
If you're interested in improving your health, and
specifically your brain health, green tea is definitely
worth considering.
Green Tea Boosts Brain Health
In a new study of 12 healthy volunteers, those who received a
beverage containing 27.5 grams of green tea extract showed
increased connectivity between the parietal and frontal cortex
of the brain compared to those who drank a non-green tea
beverage.1
The increased activity was correlated with improved
performance on working memory tasks, and the researchers believe
the results suggest green tea may be useful for treating
cognitive impairments, including dementia. According to the
study authors:2
"Our findings provide first evidence for the putative
beneficial effect of green tea on cognitive functioning, in
particular, on working memory processing at the neural
system level by suggesting changes in short-term plasticity
of parieto-frontal brain connections.
Modeling effective connectivity among frontal and
parietal brain regions during working memory processing
might help to assess the efficacy of green tea for the
treatment of cognitive impairments in psychiatric disorders
such as dementia."
In this case, the researchers also suggested that the effects
might have been strengthened if the volunteers had consumed a
pure green tea extract, as opposed to a green tea-fortified
beverage. And that is one of the great things about tea – if you
don't enjoy it as a beverage (or if you only drink it on
occasion), you can still get the health benefits by consuming it
in supplemental extract form.
How Else Might Green Tea Benefit Your Health?
Your brain is only one part of your body that might benefit
from green tea, which is recognized as an abundant source of
epigallocatechin-3-gallate (EGCG), a catechin polyphenol, and
other antioxidants. So
what else
is green tea good for?
Reduced Mortality and Chronic Inflammation
Drinking green tea is associated with reduced mortality
due to all causes, as well as mortality due to heart
disease. Research also shows holistic benefits to green tea
consumption, including lower blood pressure, oxidative
stress, and chronic inflammation.3
Heart Health
Green tea improves both blood flow and the ability of
arteries to relax, with research suggesting a few cups of
green tea each day may help prevent
heart disease.4
Type 2 Diabetes
One study found people who consume six or more cups of
green tea daily had a 33 percent lower risk of developing
type 2 diabetes
than those who consumed less than one cup per week.5
Weight Loss
There is some evidence that long-term consumption of
green tea catechins is beneficial for burning fat and may
work with other chemicals to increase levels of fat
oxidation and thermogenesis. According to research in
Physiology & Behavior:
"Positive effects on body-weight management have
been shown using green tea mixtures. Green tea, by
containing both tea catechins and caffeine, may act
through inhibition of catechol O-methyl-transferase, and
inhibition of phosphodiesterase. Here the mechanisms may
also operate synergistically.
A green tea-caffeine mixture improves weight
maintenance, through thermogenesis, fat oxidation, and
sparing fat free mass… Taken together, these functional
ingredients have the potential to produce significant
effects on metabolic targets such as thermogenesis, and
fat oxidation."
Bone Health
Green tea polyphenols combined with a form of vitamin D
called alfacalcidol could boost bone structure and strength,
according to a new study in mice. The mixture may reverse
damage to bones caused by lipopolysaccharide (LPS) induced
chronic inflammation, which could in turn reduce the risk of
osteoporosis.6
Green tea is a relative newcomer in the
bone-health arena, but previous studies have also found
that epigallocatechin-3-gallate (EGCG), a component of green
tea, blocks the activity of two molecules, IL-6 and
cyclooxygenase-2 (Cox-2), which play a role in breaking down
bone.
Vision Health
Catechins in green tea could help protect you against
glaucoma and other eye diseases, as research found that the
compounds travel from your digestive system into the tissues
of your eyes. During the study, the catechins found in green
tea were absorbed into various parts of the eyes anywhere
from 30 minutes to 12 hours after rats were given tea.7
Cancer
Green tea components have been shown to downregulate the
expression of proteins involved in inflammation, cell
signalization, cell motility, and angiogenesis, while an
association between green tea intake and decreased risk of
cancers (including
ovarian and breast8)
has been reported.9
Buyer Beware: Some Green Tea Contains Hardly Any EGCG
If you're drinking green tea hoping to increase your
antioxidant levels, you should know that some green tea brands
contain very little antioxidants. An analysis of the strength
and purity of more than 20 green tea products by ConsumerLab.com
found that EGCG levels in bottled green tea can range from just
four milligrams (mg) per cup to 47 mg, while brewable green tea
(from tea bags, loose tea or a K-cup) contained levels ranging
from 25 mg to 86 mg per serving.10
One variety, bottled Diet Snapple Green Tea, reportedly
contained almost no EGCG, while Honest Tea Green Tea with Honey
contained only about 60 percent of the 190 mg of catechins
claimed on the label.11
Green tea brewed from loose tea leaves appeared to offer the
most potent source of antioxidants like EGCG. One variety,
Teavana, contained 250 mg of catechins per serving; green tea
sold in bags from brands like Lipton and Bigelow contained lower
levels, although represented a more cost-effective alternative.
The different tea brands also varied significantly in the amount
of caffeine the products contained. While some contained
virtually none, others contained 86 mg per serving, which is
similar to the amount of caffeine in a regular cup of coffee.
You Need to Be Careful About Pollutants in Green Tea
Similar to the problem with seafood (where the beneficial
nutrients are all but cancelled out due to high levels of
pollution), tea may also contain an inordinate amount of
toxicants. Green tea plants are known to be especially effective
at absorbing lead from the soil, which is then taken up into the
plant's leaves. Areas with excessive industrial pollution, such
as China (where nearly 90 percent of the world's green tea is
produced),12
may therefore contain substantial amounts of lead.13
According to the ConsumerLab.com analysis, tea from brands
like Lipton and Bigelow contained up to 2.5 micrograms of lead
per serving compared to no measurable amounts in Teavana brand,
which gets its tea leaves from Japan. While the lead in the tea
leaves is not thought to leach very effectively into the tea you
end up drinking, if you're consuming Matcha green tea, one of my
favorites, it's especially important that it comes from Japan
instead of China. Matcha tea contains the entire ground tea
leaf, and can contain over 100 times the EGCG provided from
regular brewed green tea. You just need to be sure that the
radiation levels of the product are checked.
That said, because you're consuming the entire leaf, you want
to be sure it comes from a non-polluted, high-quality source.
The best Matcha green tea comes from Japan and is steamed,
rather than roasted or pan-fried. As a result, Matcha green tea
retains all the nutrient-rich value possible from the tea leaf,
without additives or contaminants. Both black and green teas are
naturally high in fluoride, even if organically grown without
pesticides. This is because the plant readily absorbs fluoride
thorough its root system, including naturally occurring fluoride
in the soil.
According to
fluoride expert Jeff Green, there are reports of people who
have developed crippling skeletal fluorosis from drinking high
amounts of iced tea alone.14
If you live in an area with fluoridated drinking water, as the
majority of Americans do, then you could be getting a double
dose of fluoride when you drink tea. When selecting tea of any
kind, it should preferably be organic (to avoid pesticides) and
grown in a pristine environment because, as mentioned, tea is
known to accumulate fluoride, heavy metals, and other toxins
from soil and water, so a clean growing environment is essential
to producing a pure, high-quality tea.
Even a Few Cups a Day Is Healthy
There is a misconception that it takes pot upon pot of green
tea to add up to any significant benefits. In reality, much of
the research on green tea has been based on about three cups
daily, which is easily attainable for most people. A cup of
green tea will give you anywhere from 20-35 mg of EGCG, so three
in a day will supply you with 60-105 mg. There are some studies
that have used much higher doses than this -- upwards of 1,500
mg a day -- but as of now there's clear-cut evidence of exactly
how much is best.
If you're new to tea brewing, you'll discover it's a bit of
an art, just like brewing the perfect cup of coffee. Many enjoy
using loose tea leaves, which ConsumerLab.com found may offer
even more antioxidants (while also avoiding potential
toxicants in tea bags). Once you find your "sweet spot" you
may never go back to bagged tea again. Here are a few simple
guidelines for making the "perfect" cup of tea:
- Bring water to a boil in a tea kettle (avoid using a
non-stick pot, as this can release harmful chemicals when
heated).
- Preheat your teapot or cup to prevent the water from
cooling too quickly when transferred. Simply add a small
amount of boiling water to the pot or tea up that you're
going to steep the tea in. Ceramic and porcelain retain heat
well. Then cover the pot or cup with a lid. Add a tea cozy
if you have one, or drape with a towel. Let stand until
warm, then pour out the water.
- Put the tea into an infuser, strainer, or add loose into
the tea pot. Steeping without an infuser or strainer will
produce a more flavorful tea. Start with one heaped teaspoon
per cup of tea, or follow the instructions on the tea
package. The robustness of the flavor can be tweaked by
using more or less tea.
- Add boiling water. Use the correct amount for the amount
of tea you added (i.e. for four teaspoons of tea, add four
cups of water). The ideal water temperature varies based on
the type of tea being steeped:
- White or green teas (full leaf):
Well below boiling (170-185°F or 76-85°C). Once the
water has been brought to a boil, remove from heat and
let the water cool for about 30 seconds for white tea
and 60 seconds for green tea before pouring it over the
leaves
- Oolongs (full leaf): 185-210°F or
85-98°C
- Black teas (full leaf) and
Pu-erhs: Full rolling boil (212°F or 100°C)
- Cover the pot with a cozy or towel and let steep. Follow
steeping instructions on the package. If there are none,
here are some general steeping guidelines. Taste frequently
as you want it to be flavorful but not bitter:
- Oolong teas: 4-7 minutes
- Black teas: 3-5 minutes
- Green teas: 2-3 minutes
- Once the desired flavor has been achieved, you need to
remove the strainer or infuser. If you're using loose
leaves, pour the tea through a strainer into your cup and
any leftover into another vessel (cover with a cozy to
retain the heat).
Copyright 1997- 2014 Dr. Joseph Mercola. All Rights Reserved.