FROM
MSNBC NEWS SCIENCE: April 26, 2003
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Tea may sharpen immune system |
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Study finds chemical in beverage boosts body’s defenses |
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ASSOCIATED PRESS |
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WASHINGTON, April 22 —
An
ordinary cup of tea may be a powerful infection fighter, a study
suggests. Researchers report in the Proceedings of the National Academy
of Sciences that they have found in tea a chemical that boosts the
body’s defense fivefold against disease. |
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‘This
is potentially a very significant finding. We’re seeing multiple benefits
from tea.’
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PENNY KRIS-ETHERTON
Nutrition specialist, Pennsylvania State University |
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THEY SAID the
chemical primes immune system cells to attack bacteria, viruses and fungi
and could, perhaps, be turned into a disease-fighting drug someday.
Dr. Jack F. Bukowski of Brigham and Women’s Hospital in Boston and
Harvard Medical School said Monday that he and his co-authors isolated the
chemical in the laboratory and then proved with a group of volunteers that
it did protect against germs.
5 CUPS PER DAY
“We worked out the molecular aspects of this tea component in the
test tube and then tested it on a small number of people to see if it
actually worked in human beings,” said Bukowski. The results, he said, gave
clear proof that five cups of tea a day sharpened the body’s defenses
against disease. |
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Penny Kris-Etherton, a nutrition specialist at Pennsylvania State
University, said Bukowski’s study adds to a growing body of evidence that
tea is an effective disease fighter.
“This is potentially a very significant finding,” she said. “We’re
seeing multiple benefits from tea.”
But she said the work needs to be confirmed in a much larger study,
involving more people.
In the study, Bukowski and his co-authors isolated from ordinary
black tea a substance called L-theanine. He said the substance is found as
well in green and oolong tea, which also are processed from traditional tea
tree leaves.
Bukowski said L-theanine is broken down in the liver to ethylamine, a
molecule that primes the response of an immune blood cell called the
gamma-delta T cell.
“We know from other studies that these gamma-delta T cells in the
blood are the first line of defense against many types of bacteria, viral,
fungal and parasitic infections,” he said. “They even have some anti-tumor
activity.”
A DISEASE-FIGHTING DRUG?
The T cells prompt the secretion of interferon, a key part of the
body’s chemical defense against infection, Bukowski said.
“We know from mouse studies that if you boost this part of the immune
system it can protect against infection,” he said. |
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To further test
the finding, the researchers had 11 volunteers drink five cups a day of tea,
and 10 others drink coffee. Before the test began, they drew blood samples
from all 21 test subjects.
After four weeks, they took more blood from the tea drinkers and then
exposed that blood to the bacteria called E-coli. Bukowski said the immune
cells in the specimens secreted five times more interferon than did blood
cells from the same subjects before the weeks of tea drinking. Blood tests
and bacteria challenges showed there was no change in the interferon levels
of the coffee drinkers, he said.
Bukowski said it may be possible to further isolate and refine L-theanine
from tea and use that as a drug to boost the infection defense of the body.
The health effects of tea have been extensively studied. It has been
linked to lower heart disease and cancer risk through the action of
flavonoids, a type of antioxidant. Other studies have linked tea to helping
combat osteoporosis, the brittle bone disease, and to relieving some allergy
symptoms.
© 2003 Associated Press. All rights reserved. This material may
not be published, broadcast, rewritten or redistributed.
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Coffee or tea?.... Science investigates...
Rosie Schwartz at
50PLUS.COM
Coffee or tea? Scientific investigations on coffee and tea are reported at a
dizzying pace, for the most part focussing on coffee and its impact on our
health. While it now appears tea is getting some attention, coffee keeps coming
up smelling like roses - or at least chock full of aromatic health-promoting
substances.
Gradually, the waters have become less muddied. For example, coffee is a major
source of caffeine. And it was thought caffeine caused a loss of calcium from
bones resulting in osteoporosis. But a well-conducted study of over 35,000
post-menopausal women done by the University of Minnesota vindicated caffeine as
not a bone-thinning substance.
But before you celebrate by brewing up a big pot of java, there are other
considerations:
Caffeine Facts:
Caffeine is found in both coffee and tea, as well as other beverages, such as
soft drinks. The amount in coffee, however, can be significantly more than in
tea, but much depends upon preparation:
- Drip coffee contains 140 milligrams of caffeine per five-ounce cup.
- Instant has just 60 milligrams.
- Tea provides only 30 milligrams if brewed for one minute and 45 milligrams for a
five-minute steep for a five-ounce cup.
- Decaffeinated varieties of both coffee and tea are almost caffeine-free.
Alternating decaffeinated brews with regular ones can help you keep within the
recommended caffeine quotas - the amount contained in three to four five-ounce
cups of coffee.
Caffeine affects people in different ways, and reactions to its stimulant effect
are greatly influenced by a person's weight and body size. This explains why,
for one person, a cup of coffee in the afternoon can lead to a sleepless night,
while for another an after-dinner double espresso can be a bedtime beverage.
Impact on heart
Besides being linked to irritability and sleeplessness, caffeine-containing
beverages may lead to:
- Irregular heart rhythms, such as tachycardia
- Indigestion (both regular and decaffeinated varieties of coffee contain
potentially irritating acids).
- Tea, on the other hand, is considered by many to be a soothing beverage - but
caffeine counts quickly add up for those who sip all day long.
- Using both regular and decaf tea may be preferable for caffeine-sensitive
drinkers.
When it comes to heart-health, coffee and tea have been the subject of
numerous scientific studies. A scientific review of a number of studies,
published in the journal Hypertension, looked at the effect of regular
consumption of coffee and its effect on blood pressure and found that:
As coffee consumption increased, so did blood-pressure levels.
Age, hypertension link
An Australian study evaluated what happened to blood pressure levels after two
weeks on a caffeine-free diet for people with normal blood pressure and others
with hypertension:
- In subjects with normal blood pressure readings, there was no difference.
- In those with high blood pressure, especially older subjects, readings were
higher after the coffee.
- Consequently, researchers were able to recommend that coffee intake be reduced
for older individuals, particularly those with hypertension.
Rheumatoid arthritis link
Recent research also shows a connection between coffee and the risk of
rheumatoid arthritis. In the 15-year study, reported in the Annals of the
Rheumatic Diseases, the amount of coffee consumed on a daily basis was strongly
associated with the presence in the blood of a substance called rheumatoid
factor.
This compound can usually be detected in the blood years before the actual
development of rheumatoid arthritis.
Researchers found that four or more cups of coffee a day doubled the likelihood
of testing positive for rheumatoid arthritis. While scientists don't as yet know
what compounds in coffee are responsible for this effect, they do suggest it's
yet another good reason to practice moderation.
Tea as antioxidant
As for tea, it has shown great potential on the health-front due to the
antioxidant effects of compounds called flavonoids. These substances are also
abundant in fruits and vegetables.
They help prevent cholesterol from being deposited in the arteries and reduce
the tendency of blood to clot.
Scientists have even suggested drinking a cup of tea a day could provide the
equivalent antioxidant quota as a full serving of vegetables.
The much talked about French Paradox, which promotes red wine's ability to
protect against heart disease, is mainly about the flavonoids found in that
beverage.
Although many people turn to their medicine chest for antioxidant supplements,
brewing up a pot of tea may be more effective - and cheaper.
Heart and homocysteine
High blood levels of a substance called homocysteine have recently emerged as a
major risk factor for heart disease and stroke.
Tea contains lower levels of homocysteine.
Coffee has not fared as well. In a study of over 16,000 Norwegian adults,
increased homocysteine readings were found in coffee, whether filtered, boiled
or instant.
There was no association between decaffeinated coffee and blood levels of
homocysteine.
Because tea can also contain caffeine without boosting homocysteine levels, it's
thought the trick lies within the decaffeination process. The offending
substance, which may boost homocysteine readings, is likely removed as well.
The study also found that drinking coffee and smoking cigarettes seems to be a
particularly potent combination associated with boosting homocysteine levels.
Cancer study
A recent study from the University of Toronto published in the International
Journal of Cancer looked at both coffee and tea consumption and beverages such
as alcohol and cola, to see if there was a connection to prostate cancer.
Only tea showed a relationship.
Men who drank more than two cups a day had a lower risk of prostate cancer.
Research has also indicated other benefits to consuming tea. A study group
involving post-menopausal women in Iowa showed that as tea consumption rose,
rates of certain cancers - such as that of the stomach, mouth and kidney -
actually fell.
Women who drank more than two cups of tea a day were 60 per cent less likely to
have cancers of the urinary tract than those who consumed none.
At Rutgers University, black and green tea and their decaffeinated counterparts
have all demonstrated an ability to suppress skin tumour growth in mice. Other
research showed the protective effect of black tea against both the onset and
progress of lung cancer in mice.
While more research into tea's effects on humans is needed, studies from China
show promising results. Subjects diagnosed with pre-cancerous lesions in the
mouth appeared to benefit from tea. In one study, tea was both consumed and
applied topically and seemed to delay the progression of the lesions into oral
cancer.
Milk in tea
Some research shows that when tea contains milk, the beneficial compounds or
flavonoids are likely absorbed in smaller amounts. This may explain why green
tea has traditionally had a more healthful reputation.
In countries such as Britain, where black teas are thought of as a national
beverage, they're usually served with milk. Research on black tea and its link
to disease rates may have been clouded by the addition of milk.
That's not to say you have to have your tea without milk, but if you're seeking
tea's healthful benefits, vary how you drink it.
Rosie Schwartz, Contributing Editor of 50Plus.com, is a Toronto-based consulting
dietician in private practice and is author of the 10th anniversary edition of
The Enlightened Eater (Macmillan 1998).
© February 2001 CARPNews FiftyPlus
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