Green tea and cancer

March 8, 2011 - 0:0

Green tea has been a medicinal potion for thousands of years. Laden with plant chemicals called flavonoids known for their powerful antioxidant abilities, green tea is touted to protect against two of the biggest of human scourges—coronary disease and cancer. But just how green tea works its wonders in the prevention or treatment of individual disease remains a mystery. Thomas Gasiewicz, researcher in the Department of Environmental Medicine at the University of Rochester Medical Center, presented evidence for some of its magic at an international conference on diet and cancer held in Washington, D.C., today. His laboratory demonstrated that the prime antioxidant component of green tea, which is in the family of plant chemicals called catechins—or epigallocatechin-3-gallate (EGCG) to be precise—zooms in on a key target in the cancer cell. And the target is a big one: a normal stress protein, known as heat shock protein 90 (HSP90). Heat shock or stress proteins are critical to survival of all cells, cancerous or otherwise. Stress proteins abound in both plants and animals. Think of them as protectors that chaperone the thousands of worker-bee proteins that interact in and on the surface of our cells in the course of any one cell's life. Growth, performance, communication, you name it, and some form of HSP is a key player. When cells are threatened by a treacherous environment such as heat (from which we get the name HSP), proteins curl up and then clump up. We now know it also happens with damaging cold, low oxygen, or poisons. Heat shock protein protectors quickly rev up and come to the rescue to both repair injured proteins and to carry the irreversibly damaged ones to a disposal dump for an out-of-the-way burial so new ones can take their place. Cancer hijacks the stress protein network in its efforts to overtake the body. Cancer cells are fast growing and on the march wherever they set up shop—breast, prostate, colon, bone marrow. And in that superstressed state of attack, cancer cells produce abnormally high levels of HSP90 to protect their cancer-producing proteins. Even in the face of toxic radiation and chemotherapy, some cancer cells survive because of these natural potent protectors. What Gasiewicz and his colleagues have shown is that the age-old EGCG does battle with HSP90. A few months ago, his laboratory reported for the first time that EGCG binds to this protective stress protein important to cancer growth and survival and essentially takes it out of commission. One caveat: You have to drink a lot of tea to get enough EGCG to do any good. Just how much is not known, but it is somewhere between three to 10 cups a day. Because of its bitterness and the caffeine load of that much tea, that's hard to do. No wonder that after a detailed analysis of numerous studies of green tea and cancer involving tens of thousands of patients, the Food and Drug Administration announced only two weeks ago that there is ""no credible evidence"" to support green tea's health claims when it comes to cancer. And for the two cancers where the studies are the most promising, namely prostate cancer and breast cancer, the FDA calls it ""highly unlikely"" that green tea reduces the risk of either. However—and there's always a however in clinical medicine—studies are underway to look at cancer and concentrated green tea extract, which is rich in ECGC but free of the side effects of overdosing on the full tea brew. (Source: Health.usnews)

- Delaying AIDS Bottom of Form Many people who are infected with HIV go on for years without developing AIDS. A few studies have found that people with HIV who take vitamins have a more slowly progressing disease, and a lot of people with HIV routinely take vitamins. But no one actually knows if you can influence the disease with vitamins. In this study, researchers from the Harvard School of Public Health and Muhimbili University College of Health Sciences set out to test this idea with pregnant, HIV-positive women in Tanzania. What the researchers wanted to know: Do vitamins help slow the progress of HIV? What they did: For two years in the mid-1990s, researchers enrolled 1,078 pregnant women with HIV in Dar es Salaam, Tanzania. Women were randomly assigned to one of four treatments: vitamin A alone, a multivitamin that left out vitamin A, a multivitamin including vitamin A, and a placebo. Neither the women nor the people treating them knew what vitamins they were on. All of them also received the usual folic acid and iron that women should have before giving birth. All children were given vitamin A once every six months, which is standard in Tanzania. Most women did not have access to antiretroviral drugs against HIV. The women visited a study clinic every month until the study ended in August 2003. Of the 1,078 HIV-positive women, 299 progressed to AIDS or died of AIDS-related causes. What they found: Women who took vitamin C, vitamin E, and the B vitamins had a slower disease progression. (Vitamin A didn't help much.) They were significantly less likely to develop AIDS or to die of AIDS-related causes and less likely to develop the mouth and intestinal problems of HIV than women who took placebo. Women on vitamins also had a significantly lower viral load. What it means to you: Taking vitamins, for pennies a day, could delay the start of symptoms—the time U.S. guidelines recommend starting antiretroviral drugs—which would save a lot of money and discomfort. Caveats: This study was relatively small and on a very specific population: young women in a developing country. It's hard to say how well it would apply to, say, middle-aged American men who eat a healthy diet. Find out more: How the World Health Organization defines stages of HIV in developing countries: http://hivinsite.ucsf.edu Read the article: Fawzi, W.W. et al. ""A Randomized Trial of Multivitamin Supplements and HIV Disease Progression and Mortality."" New England Journal of Medicine. July 1, 2004, Vol. 351, No. 1, pp. 23–80. (Source: Health.usnews)
- From prayer to herbs: Alternative medicine goes mainstream Bottom of Form Alternative medicine is looking more mainstream than alternative. According to a new government survey, over a third of American adults use some form of nontraditional medicine. What the researchers wanted to know: How many Americans use complementary and alternative medicine? What therapies do they use? And why? What they did: This is government work, so there are a lot of long titles involved. Researchers at the National Center for Complementary and Alternative Medicine (part of the National Institutes of Health) and the Centers for Disease Control and Prevention analyzed part of the 2002 data from the National Health Interview Survey, for which more than 30,000 adults answered questions about their health and healthcare. The survey, which is designed to get a representative sample of Americans, has been going on for decades, collecting reams of data on the health of Americans. What they found: Over a third of adults had used some form of nontraditional medicine in the previous 12 months. If you count people who use prayer specifically for better health, the proportion goes up to 62 percent. Forty-three percent of adults pray specifically for their own health, and nearly 25 percent have someone else pray for them. After prayer, the most commonly used therapies were natural products (including herbs), 19 percent; deep breathing, 12 percent; taking part in a health prayer group, 10 percent; meditation, 8 percent; chiropractic, 8 percent; yoga, 5 percent; massage, 5 percent; and diet-based therapies (including Atkins and Zone diets), 4 percent. Most people who use complementary and alternative therapies say they do so because they think that combining those therapies with conventional medicine will help; half of all people try alternative medicine because they think it's interesting to try. Who cares: I do. Don't you? Doctors should care that nearly 20 percent of U.S. adults are taking ""natural products""—and remember to ask their patients if they're taking any dietary supplements, which may interact with prescription or over-the-counter drugs. The caveats: The data come from a survey, so people could be lying about the treatments they've tried. Also, these data are only about one point in time; they don't say anything about how alternative medicine usage is changing over time. Find out more: The National Center for Complementary and Alternative Medicine (http://nccam.nih.gov) has this study and health resources on complementary and alternative medicine. (Source: Health.usnews)