Bessen, frambozen en groene thee tegen kanker*
Uit twee studies blijkt het belang van voeding met regelmatig fruit zoals bessen,
frambozen en groene thee belangrijk is in het voorkomen en behandelen van kanker. In de eerste studie werd gekeken naar patiënten met een beginnende vorm van een Plaveiselcelcarcinoom. Mondkanker van dit type carcinoom is een van dodelijkste vormen van kanker. 20 patiënten met beginnende weefselschade werden vergeleken met 10 gezonde personen. Bij de patiënten werd 4x per dag een speciale gel op de wonden in de mond gesmeerd. De speciale
gel bestond voor 10% uit gevriesdroogde zwarte frambozen. Na 6 weken bleek dat de weefselschade duidelijk verminderd was zoals ook twee ontstekingsmarkers (Cox-2 en iNOS) duidelijk afgenomen waren en dat zonder enige bijwerking.
In de tweede studie, weliswaar met ratten blijkt dat groene thee extracten darmkanker wellicht kunnen tegengaan zo niet flink vertragen. Ratten voorbestemd om darmkanker te ontwikkelen kregen een vergelijkbaar westers dieet of eenzelfde dieet aangevuld met groene
thee-extracten. Na 34 weken hadden de "groene thee" ratten 55% minder tumoren, tumoren die bijna de helft kleiner en ook minder kwaadaardig waren. De hoeveelheid groene thee is te vergelijken met
4-6 koppen per dag voor mensen.
New Findings Show Astounding Cancer Prevention Effects of Black Raspberries, Blueberries, Olive Leaves and Green Tea
Two 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."
(November
2008)
