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Life Extension Magazine

LE Magazine December 2001

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Green tea polyphenols inhibit prostate cancer in mouse model

According to study findings published in the August 28, 2001 issue of the Proceedings of the National Academy of Sciences [PNAS 2001 Aug;98(18):10350-10355], green tea polyphenols—the equivalent found in about six cups of green tea per day in humans—helped to significantly reduce the risk of prostate cancer in a mouse model.

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In one pair of experiments, the researchers divided 28-week-old male mice into two groups, and administrated a 1% green tea polyphenol infusion for a period of 24 weeks, while the control group received tap water. The mouse model used in the experiments was designed to spontaneously develop metastatic prostate cancer, mimicking the progression of the disease in humans. Prostate gland removal and subsequent MRI (magnetic resonance imaging) showed that green tea polyphenols almost completely inhibited metastases to distant sites (i.e. lymph nodes, lung, liver and bone) while increasing tumor-free survival. In addition, 36 eight-week-old mice underwent the same procedure in a third experiment, and were allowed to live into old age to conclude the study. Follow-up, using MRI, at 20 and 30 weeks showed that the entire control group had developed tumors at 20 weeks, and had fully developed growths by 30 weeks. Contrarily, the polyphenol group showed an average 44% reduction in prostate cancer growth at 20 weeks and a 42% reduction at 30 weeks.

The study authors believe that the polyphenols’ efficacy could relate to their ability to induce apoptosis of prostate cancer cells, which may have inhibited tumor development and metastases, although further evidence would have to confirm this. Currently, they suggest that “regular consumption of green tea may prolong life expectancy and quality of life in prostate cancer patients.” Moreover, given that prostate cancer is often diagnosed in older men, say the authors, any delay in disease development—as afforded by green tea polyphenols, for example—could substantially reduce the number of prostate cancer patients.


Sunscreens should contain antioxidant, study finds

Sunscreens that do not contain topical antioxidants fail to provide adequate protection against ultraviolet radiation, according to Dr. Kerry Hanson, a researcher at the University of Illinois. Using a two-photon laser fluorescence-imaging microscope, Dr. Hanson used fluorescent tags to show the presence of free radicals. She also examined skin cells for signs of damage.

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Dr. Hanson found that sunscreens with SPF of 15 can block up to 94% of UV radiation. The radiation that does get through, however, still produces significant damage. One result of long-term UV exposure is photoaging. But wrinkles and age spots are relatively minor consequences of UV-induced damage; the main danger is skin cancer, including basal and squamous skin cancer, and melanoma, which is invasive and often deadly. Typical sunscreens offer no antioxidant protection.

Previous studies have shown that topical antioxidants, both natural and synthetic, provide significant photoprotection when used before UV exposure. Dr. Hanson examined the effectiveness of sodium ascorbyl phosphate, a stable form of vitamin C, and two forms of vitamin E: the acetate form and tocopherol, the alcohol form. Vitamin C as sodium ascorbyl phosphate turned out to be the most effective free radical quencher.

According to Dr. Hanson, skin enzymes cleave the phosphate group, forming a reservoir of vitamin C. Dr. Hanson discovered that multiple application of the stable form of vitamin C provided the best protection, presumably because of a larger reservoir of vitamin C in the skin cells. Dr. Hanson’s findings emphasize the importance of using sunscreens that contain antioxidants, especially vitamin C in a stable form.

Study shows antioxidants play vital role in protecting skin. EurekAlert 08-30-2001.

—Ivy Greenwell


Greener pastures for cancer prevention

After mounting evidence that CLA (conjugated linoleic acid), a fat found in cows’ milk, may battle cancer, a team of British scientists is embarking on the first human trials to see whether CLA’s anti-cancer properties may relate to CLA bolstering the immune system to search out and destroy tumors. The experimentation by researchers at Southampton and Reading universities will involve administering two forms of CLA to people in three increasing doses over a six-month period. Results could help the dairy industry to devise ways to produce cow’s milk with the right kind and amount of CLA, and lead to the development of CLA-enhanced milk or “supermilk,” butter and cheese products.

Earlier research suggests that the best way to increase CLA concentration in cow’s milk is to let them graze on fresh grass. A study in the Journal of Dairy Science [Dhiman TR, et al. 1999;82(10): 2146-56] showed that cows feeding on fresh pastures produce up to five times more CLA than those raised on different diets. Yet only 10% to 12% of US dairy cows are currently grazed, their diet typically comprised of corn and alfalfa.

Lab animals feeding on CLA-enriched diets showed a reduction of several kinds of cancer and slower progression of atherosclerosis. Human studies have so far demonstrated that 3.4 grams of CLA per day can reduce body fat and preserve muscle tissue [Blankson H, et al. J Nutr 2000;130:2943-2948].

Given CLA’s purported immune-enhancing and cancer-fighting abilities, and the fact that our bodies don’t produce the substance on its own, having readily available CLA-rich foods in our diet and taking supplemental CLA would prove a boon to preventive health.

—Angela Pirisi


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