March 25, 2008

Just one cup of green tea per day cuts ovarian cancer risk in half 

A short communication published in the March, 2008 issue of the American Association for Cancer Research journal Cancer Epidemiology, Biomarkers and Prevention reported the outcome of a study conducted by researchers at Fred Hutchinson Cancer Research Center and the University of Washington in Seattle which found that women who drank one or more cups per day of green tea experienced a 54 percent reduction in the risk of epithelial ovarian cancer. Because the disease is difficult to detect in its early, treatable stages, and a reliable screening test is still not available to the public, an effective means of preventing the disease “remains the only feasible approach to reduce ovarian cancer mortality,” according to the authors.

Mary Anne Rossing and her colleagues set out to evaluate the relationship between caffeine-containing beverages and ovarian cancer risk by comparing 781 women diagnosed with a primary invasive or borderline epithelial ovarian cancer between 2002 and 2005, and 1,263 women without the disease. Interviews with the participants obtained demographic and lifestyle characteristics, medical, family and reproductive history, and beverage consumption data five years prior to ovarian cancer diagnosis (or prior to an assigned reference date for the control subjects). Caffeine-containing drinks were reported as brewed coffee, instant coffee, espresso or espresso drinks, green tea, black tea, colas and root beer, diet colas and diet root beer, and caffeinated soft drinks. Decaffeinated beverages were reported separately.

In agreement with previous studies, women who had been diagnosed with ovarian cancer were less likely to have used hormonal contraception, had a greater frequency of childlessness, or were likelier to have a family history of the disease. While the frequent intake of colas or root beer, whether regular or decaffeinated, was associated with a moderately increased risk of ovarian cancer, none of the other beverages were associated with increased or decreased risk, with the exception of green tea. Women who consumed one or more cups of green tea per day experienced a 54 percent reduction in ovarian cancer risk compared to those who did not drink green tea. Those who reported drinking an average of less than one cup per day experienced a smaller reduction in risk. Elimination of Asian women from the analysis (who are often frequent consumers of green tea), analysis of the data by tumor type, and separation of the women according to age or menopausal status failed to modify the finding.

The relatively high levels of epigallocatechin-3-gallate in green tea have been shown to help inhibit the growth of ovarian cancer in cell cultures according to two studies cited by the authors. Additionally, green tea drinking has been associated with a reduced risk of several other cancers. “Green tea, which is commonly consumed in countries with low ovarian cancer incidence, should be further investigated for its cancer prevention properties,” the authors conclude.

Cancer treatment: the critical factors

The family of proteins known as Ras plays a central role in the regulation of cell growth. It fulfills this fundamental role by integrating the regulatory signals that govern the cell cycle and proliferation.

Defects in the Ras-Raf pathway can result in cancerous growth. Mutant Ras genes were among the first oncogenes identified for their ability to transform cells to a cancerous phenotype, that is, a cell observably altered because of distorted gene expression. Mutations in one of three genes (H, N, or K-Ras) encoding Ras proteins are associated with upregulated cell proliferation and are found in an estimated 30-40% of all human cancers. The highest incidences of Ras mutations are found in cancers of the pancreas (80%), colon (50%), thyroid (50%), lung (40%), liver (30%), melanoma (30%), and myeloid leukemia (30%) ( Duursma et al. 2003; Minamoto et al. 2000 ; Vachtenheim 1997; Bartram 1988 ; Bos 1989; Minamoto et al. 2000 ).

According to information in Scientific American, the differences between oncogenes and normal genes are slight. The mutant protein that an oncogene ultimately creates may differ from the healthy version by only a single amino acid, but this subtle variation can radically alter the protein's functionality.

Researchers at Rutgers University investigated the ability of different green and black tea polyphenols to inhibit H-Ras oncogenes. The Rutgers team found that all the major polyphenols contained in green and black tea except epicatechin showed strong inhibition of cell growth (Chung et al. 1999). Texas A&M University also found that fish oil decreased colonic Ras membrane localization and reduced tumor formation in rats. In view of the central role of oncogenic Ras in the development of colon cancer, the finding that omega-3 fatty acids modulate Ras activation likely explains why dietary fish oil protects against colon cancer (Collett et al. 2001).

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Life Extension Update

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Dayna Dye
Editor, Life Extension Update
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