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Green Tea & Cancer, HIV
  Green Tea Blocks HIV in Test Tubes
Too Soon to Know if Green Tea Will Do the Same in People

By Miranda Hitti, WebMD Medical News
Reviewed By Ann Edmundson, MD, Thursday, May 25, 2006
May 25, 2006 -- An antioxidant in green tea may block HIV, the virus that causes AIDS, from attaching to an important molecule on immune system cells.
That finding is based on lab tests done on human blood cells, not people. The lab tests were done by Christina Nance, PhD, and colleagues. Nance works in Houston, at Texas Children's Hospital and Baylor College of Medicine.
In a nutshell, Nance's team wanted to see if epigallocatechin gallate (EGCG), a chemical found in green tea, might block HIV from attaching to the immune system's T-helper cells, thus protecting those T cells from HIV's damage. T-helper cells act as a "general" in directing and activating other immune cells in the fight against HIV.
The results show that EGCG might indeed help do that. It's not yet clear if the findings will have meaning beyond the lab. HIV has proven to be crafty against many different attempts to thwart it from latching onto immune system cells.
The test results were presented in Canada at the North American Research Conference on Complementary & Alternative Medicine, held in Edmonton, Alberta, Canada.
Lab Tests
Nance's team treated some human T cells with three doses of EGCG. For comparison, they didn't expose other T cells to EGCG.
Then they added an HIV component called gp120 to the T cells. The goal was to see if EGCG thwarted gp120 from binding to a certain molecule -- the CD4 molecule -- on T-helper cells.
When gp120 latches onto a T cell's CD4 molecule, it paves the way for HIV to enter -- and eventually disable and kill -- the T cell.
EGCG "markedly inhibited" gp120 from binding to the T cells' CD4 molecules, write Nance and colleagues. The highest EGCG dose had the strongest effect. The lowest dose had the mildest effect. The medium dose had a medium-sized effect.
However, none of the EGCG doses totally blocked gp120 from binding to the CD4 molecule, the study shows.
This isn't the first time that EGCG has been studied in HIV. In 1989, Japanese researchers reported that EGCG may help block an enzyme called reverse transcriptase that slips HIV's genetic material into the host cell's DNA.
SOURCES: North American Research Conference on Complementary & Alternative Medicine, Edmonton, Alberta, Canada, May 24-27, 2006. Nakane, H. Nucleic Acids Symposium Series, 1989. WebMD Public Information from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health: "How HIV Causes AIDS." News release, North American Research Conference on Complementary & Alternative Medicine.
Green Tea's Record Against Cancer Grows
Green Tea Extract Targets Cancer Without Hurting Healthy Cells

By Miranda Hitti, WebMD Medical News
Reviewed By Michael Smith, MD, Tuesday, February 15, 2005
Feb. 15, 2005 -- Green tea's reputation as a powerhouse against cancer keeps growing. Now, scientists have new insights on how green tea thwarts cancer.
Green tea extract has shown promise against cancer in numerous studies. Those findings came from animal studies and epidemiologic research, which tracks a disease's occurrence in a large population of people.
In other words, the human studies on green tea are mainly based on observation and don't prove that tea is responsible for results. But as one of the world's most popular drinks, tea is widely considered healthy, whether it's green, black, or white tea. However, green tea and green tea supplements generally contain higher amounts of disease-fighting antioxidants called polyphenols than black tea.
For instance, studies on mice showed that green tea helped prevent prostate cancer growth. Green tea extract is also reported to induce cancer cell death and starve tumors by curbing the growth of new blood vessels that feed them.
But exactly how that happens isn't clear. Tea's antioxidants may protect against some forms of cancer. They may also help prevent heart disease by relaxing blood vessels and preventing blood clots. But the precise ways green tea affects cancer aren't fully understood.
Uncovering a Clue to Green Tea's Power
University of California Los Angeles (UCLA) researchers used green tea extract on human bladder cells, some of which were cancerous. Their findings appear in the Feb. 15 issue of Clinical Cancer Research.
The green tea extract targeted the cancer cells without harming healthy cells, say the researchers. Taking a closer look, they noticed something unusual about the cancer cells.
The green tea extract apparently made the cancer cells more mature, making them bind together more closely. That made it harder for the cancer cells to become invasive and spread.
"In effect, the green tea extract may keep the cancer cells confined and localized, where they are easier to treat and the prognosis is better," says researcher JianYu Rao, MD, in a news release.
That's an important clue, but it's not the final verdict on how green tea works against cancer. More work is still needed to understand the process, say the scientists.
Meanwhile, if you're interested in trying green tea, be aware that the FDA hasn't evaluated claims about green tea's powers and that supplements are not regulated by the government. If you're watching your caffeine intake, green tea does contain some caffeine (but much less than coffee).
To get green tea's potential disease-fighting benefits, studies have suggested that you should drink four cups a day. Green tea supplements are also available, and at least one study has shown that you may actually get more powerful antioxidants from supplements than from drinking tea.
As always, let your doctor know about any over-the-counter health products you're taking.
SOURCES: Lu, Q. Clinical Cancer Research, Feb. 15, 2005; vol 11: pages 1-9. News release, UCLA's Jonsson Cancer Center. WebMD Medical News: "Green Tea May Stall Prostate Cancer Growth." WebMD Medical News: "The Green Tea Taste Test." WebMD Medical News: "Green Tea Capsules Loaded With Antioxidants."
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