Friday, September 26, 2008
New Findings Show Astounding Cancer Prevention Effects of Dark Berries and Green Tea
Three studies presented at the American Association for Cancer Research's Sixth Annual International Conference on Frontiers in Cancer Prevention Research in Philadelphia have demonstrated the powerful cancer-fighting benefits of dark berries, green tea and olive leaves, and suggest that gels and beverages may some day be used to prevent against cancer and tumor growth.
In the first study, researchers from Ohio State University discovered that a gel based on freeze-dried black raspberries helps prevent precancerous mouth tumors (lesions) from becoming malignant.
"This gel appears to be a valid means of delivering anthocyanins and other cancer-preventing compounds directly to precancerous cells, since it slowed or reduced lesion progression in about two-thirds of study participants," said researcher Susan Mallery.
According to the American Cancer Society, oral squamous cell carcinoma is one of the deadliest forms of cancer, causing 7,500 deaths each year in the United States. Because no chemopreventive agent or treatment method other than radical mouth surgery exists, even those who survive the cancer often emerge significantly disfigured. And even in many cases where tumors are fully removed, they still recur.
"Oral cancer is a debilitating disease and there is a desperate need for early detection and management of precancerous lesions," said Mallery.
Most mouth cancer begins as small, noncancerous lesions in the mouth that are difficult to detect. It was these lesions that were treated in the Ohio State University study.
Researchers carried out the study on 20 participants who had identifiable precancerous mouth lesions and 10 who were healthy to constitute a control group. Both groups were instructed to dry the sites of their lesions gently, or to dry a predetermined site in the control group. The black raspberry gel was then rubbed into the area after each meal and before bed, for a total of four applications daily.
The gel, made of 10 percent freeze-dried black raspberries, looks like jam, but does not contain the sugars that give berries their sweet taste.
After six weeks, a microscopic diagnosis of the lesions in the precancerous patients showed that 35 percent had improved, 45 percent had stabilized and 20 percent had worsened. No side effects were observed in either the experimental or control group.
Researchers also collected cell samples from participants' mouth lesions both before and after treatment. Before the treatment, the lesions showed elevated levels of two proteins, COX-2 and iNOS, that have been associated with increased inflammation and risk of malignancy. After treatment, the levels of these proteins decreased significantly.
In addition, many cells exhibited a genetic condition before treatment known as "loss of heterozygosity," in which a cell has lost one copy of a tumor-suppressing gene, leaving it with only one remaining copy. This condition greatly increases the chance that a cell will become cancerous, should the last copy of the tumor-suppressing gene be turned off for some reason or lost through mutation. After the treatment, however, many of the cells in the lesion sites were found to have regained a second copy of the gene.
"We speculate that the chemopreventive compounds in black raspberries assist in modulating cell growth by promoting programmed cell death or terminal differentiation, two mechanisms that help "reeducate" precancerous cells," Mallery said.
The researchers believe that much of the cancer-preventive effect of black raspberries can be attributed to naturally occurring plant chemicals called anthocyanins.
"Black raspberries are full of anthocyanins, potent antioxidants that give the berries their rich, dark color, and our findings show these compounds have a role in silencing cancerous cells," Mallery said.
In another study presented at the same conference, researchers from Rutgers University found that an extract of green tea may help prevent against the growth of colorectal tumors.
Researchers first induced colorectal cancer in mice with a toxin, azoxymethane, which is believed to cause mice to develop tumors similar to those found in human colorectal cancer. All of the rats were then placed on a high-fat diet intended to simulate a typical Western diet. In addition to this food, half of the rats were also given a 0.24 percent solution of Polyphenon E, a standardized green tea extract.
Polyphenon E contains four of the major polyphenols that occur in green tea. Sixty-five percent of the polyphenol concentration of the extract is epigallocatechin gallate (EGCG), which is believed to be the most active ingredient. Prior studies have shown that EGCG helps prevent the skin from the tumor-inducing effects of ultraviolet radiation.
After 34 weeks, the rats that had been given the green tea extract developed 55 percent fewer tumors than the rats on the high-fat diet alone. In addition, the treated rats had tumors that were 45 percent smaller and were less likely to be malignant. They also weighed approximately 5 percent less than the rats that had not been treated with the extract. Tests of the treated rats' blood and colorectal mucosa showed detectable concentrations of green tea polyphenols.
Green tea polyphenols are also believed to block the body's ability to absorb fats.
The researchers said that the amount of polyphenols used in the test could probably be achieved simply by drinking green tea.
"When you account for caloric consumption, 0.24 percent Polyphenon E in the diet gave the experimental rats the equivalent of about four to six cups of tea a day," said researcher Hang Xiao. "While I can't make any recommendations for how much green tea people should drink each day, it isn't uncommon for some to drink that much tea."
In the third study, researchers from the University of Sydney, Australia, found that a commercially available berry drink inhibited the growth of prostate cancer cells.
The drink, marketed as Blueberry Punch, contains a combination of extracts from blueberries, elderberries, red grapes, raspberries, grape skin, grape seed, citrus skin, green tea, olive leaf, olive pulp, tarragon, turmeric and ginger. The researchers tested each of these ingredients individually, and confirmed that all of them are antioxidants that effectively suppress the growth of cancerous cells in laboratory tests.
In order to determine how the effectiveness of a combination of the antioxidants compare with the sum of the individual ingredients, the researchers first exposed prostate cancer cells in the laboratory to increasing concentrations of Blueberry Punch. After 72 hours, the size and viability of the cells decreased relative to the dose of punch they had been given.
The researchers then tested the punch on mice that had been induced to develop prostate tumors similar to those found in humans. After two weeks, mice that had been consuming a 10 percent solution of Blueberry Punch had tumors 25 percent smaller than those in mice that had not been given the beverage.
Among the potential mechanisms of action for the beverage, the researchers cited the inhibition of inflammation and the inhibition of a protein called cyclin D1, which has been an observed effect of EGCG.
Because Blueberry Punch is a food product and not a drug, the researchers believe that there should be no health side effects to its use, excepting only people who have a food allergy to one or more of the ingredients. They hope to move on to trials in humans with prostate cancer.