Green Tea & Breast Cancer
Other researchers reported that an extract from green tea, Polyphenon E, may help inhibit breast cancer by affecting substances called growth factors. Growth factors are involved in the signals that tell breast cancer to grow.
In earlier research, Katherine Crew, MD, assistant professor of medicine and epidemiology at Columbia University Medical Center in New York, had assigned 40 women already treated for breast cancer to take 400, 600, or 800 milligrams of the extract or to take a placebo twice daily for six months.
That was a study to examine any toxic effects of the extract. For the current study, she evaluated blood and urine samples from 34 of the women to see how the extract might work as a cancer fighter.
“We wanted to better understand the biological effects,” she says.
“After two months of Polyphenon E, there was a reduction in hepatocyte growth factor,” she says. This is one of the growth factors that affect breast cancer cell growth, spread, and invasion. That reduction declined and was not different from the placebo group at four months, however.
It’s still too early to recommend green tea extract as a way to prevent breast cancer, Crew says.
Green Tea & Breast Cancer: Perspective
The new research on green tea and breast cancer adds to growing evidence of its benefits, according to Joanne Mortimer, MD, director of the Women’s Cancer Program at the City of Hope Comprehensive Cancer Center.
What Do the Antioxidants in Green Tea Do?
One of the antioxidants found almost exclusively in green tea is epigallocatechin-3-gallate (EGCG), which has been at the heart of recent green tea headlines. Overall, research has yielded conflicting results on whether green tea can fight or prevent cancer.
However, one particularly interesting study, presented at a medical conference in 2008, has shown promising results. Researchers at the University of Mississippi Medical Center added EGCG to the drinking water of 10 female mice. An equal number were given plain drinking water. All were later injected with breast cancer cells. In the mice that had ingested EGCG, tumors were 66% smaller than those in the untreated mice. Their tumors also appeared to have less blood supply, suggesting that the EGCG works by inhibiting blood supply to cancer cells.
While green tea has been the subject of other studies, most of these have focused on whether it prevents cancer (among lifelong tea drinkers in Asia, for example), not whether it slows an existing disease process. Results have been mixed, but more controlled and randomized studies on humans are currently in the works.
What Does this Study Mean for Me?
First, it’s important to note that the amount of EGCG these mice were given translates to an awful lot of tea for the average human, that is, about 15 to 30 cups each day for 5 weeks. Although that may not be a pace you can keep up with, there’s little harm in adding a few cups of green tea to your daily routine.
Aside from its cancer-fighting potential, there is some evidence that green tea lowers cholesterol and improves function of the immune system. In a 2007 study, researchers at the University of Michigan Health System found that EGCG inhibits production of molecules in the immune system that are blamed for inflammation and joint damage in arthritis sufferers.
As its popularity grows in the Western world, green tea is getting easier to find; if it’s not on the shelf at your local supermarket, check with a nearby health food store or Asian market.
Green tea does contain caffeine. Be on the lookout for potential side effects, such as heart palpitations and nervousness, and adjust consumption as needed.
“There really does seem to be something there,” she says. The new study provides a potential explanation for why green tea may help, she says.
So should women drink green tea with an eye to prevention of breast cancer?
An oral green tea extract, Polyphenon E, appears to inhibit vascular endothelial growth factor and hepatocyte growth factor, both of which promote tumor cell growth, migration and invasion.
Researchers made this discovery during a secondary analysis of a phase Ib randomized, placebo-controlled study of Polyphenon E in a group of 40 women with hormone receptor-negative breast cancer. Katherine D. Crew, M.D., assistant professor of medicine and epidemiology at Columbia University Medical Center in New York, N.Y., presented the data at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, held in Anaheim, Calif., Oct. 16-19, 2012.
“Many preclinical studies have looked at epigallocatechin-3-gallate, or EGCG, which is one of the main components of green tea, and the various possible mechanisms of its action against cancer, but it is very difficult to do those same kinds of studies in humans,” Crew said. “This study was too small to say for sure if green tea will prevent breast cancer, but it may move us forward in terms of understanding antitumor mechanisms.”
In the primary analysis, presented at last year’s Frontiers in Cancer Prevention Research meeting, 40 women were randomly assigned to 400 mg, 600 mg or 800 mg of Polyphenon E or to placebo twice daily for six months. During that time, researchers collected blood and urine samples from participants at baseline and at two, four and six months.
In this secondary analysis, Crew and colleagues used the blood and urine samples to examine biologic endpoints, such as inflammatory proteins, growth factors and lipid biomarkers, which might point to the mechanism of action behind green tea extract. Biomarker data were available for 34 of the 40 patients.
Women assigned to the extract had an average 10-fold increase in green tea metabolites compared with placebo. In addition, they had a significant reduction in hepatocyte growth factor levels at two months compared with women assigned to placebo. However, at the four-month and six-month follow-ups, the difference was no longer statistically significant.
The researchers also identified a trend toward decreased total serum cholesterol and decreased vascular endothelial growth factor in women assigned to the extract.
“I don’t think we are quite ready to make that leap,” Mortimer says. “But it is pretty interesting.”
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These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the “peer review” process, in which outside experts scrutinize the data prior to publication in a medical journal.
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Ahmed, Salah-uddin. “Epigallocatechin-3-gallate Inhibits IL-1-Induced IL-6 Production and Cyclooxygenase-2 Expression in Rheumatoid Arthritis Synovial Fibroblasts in Vitro.” Experimental Biology 2007. 120th Annual Meeting of the American Physiological Society, Washington, D.C. 29 Apr 2007.
American Cancer Society Staff, “Green Tea.” Cancer.org. 29 Jun 2007. American Cancer Society. 30 Apr .2008.
Gu, Jian-Wu. “Oral Administration of EGCG, an Antioxidant Found in Green Tea, Inhibits Tumor Angiogenesis and Growth of Breast Cancer in Female Mice.” Experimental Biology 2008. 121st Annual Meeting of the American Physiological Society, San Diego , Calif. 7 Apr 2008.