 You may have heard the expression knowledge is power. Well, today we're going to give you more power to control your diet and lifestyle by giving you the facts. Welcome to the Nutrition Facts Podcast. I'm your host, Dr. Michael Greger. Today we look at the surprising power of green tea, one of the healthiest beverages we can drink. It has been associated with about a 30% reduction in breast cancer risk and may protect against gynecological malignancies, such as ovarian cancer and endometrial cancer, as well as lower cholesterol, blood sugar, and body fat. In our first story we look at how green tea appears to work by boosting the immune system. The belief of green tea is a wonder weapon against diseases dates back thousands of years. I've talked about it in relation to chronic disease, but what about infectious disease? Interest in the antimicrobial activity of tea dates back to a military medical journal in 1906, suggesting that servicemen fill their canteens with tea to kill off the bugs that caused typhoid fever. However, this effect of tea was not studied further into the late 1980s when tea compounds were pitted against viruses and bacteria in test tubes and petri dishes, but what we care about is do they work in people? I had dismissed this entire field of inquiry as clinically irrelevant until genital warts. External genital warts caused by human wart viruses are one of the most common and fastest spreading venereal diseases worldwide. Patients with external genital warts present with one or several cauliflower-like growths on the gendals and or anal regions, considerably impairing people's emotional and sexual well-being, but rub some green tea ointment on and you can achieve complete clearance of all warts in more than 50% of cases. Wow, if it works so well for wart viruses, what about flu viruses? Works great in a petri dish, but what about in people? Tea-drinking school children do seem to be protected, but you don't know until it's put to the test. If you give healthcare workers green tea compounds, they come down with the flu about three times less often than those given placebo. In fact, just gargling with green tea may help. While a similar effect was not found in high school students, gargling with green tea may drop the risk of influenza infection 7 or 8-fold compared to gargling with water in elderly nursing home residents where flu can get really serious. Unlike antiviral drugs, green tea appears to help by boosting the immune system, enhancing the proliferation and activity of gamma-delta T cells, a type of immune cell that acts as a first-line defense against infection. Subjects who drank 6 cups of tea per day had up to a 15-fold increase in infection-fighting interferon production in as little as one week. But why? There's actually a molecular pattern shared by cancer cells and pathogens and with edible plant products such as tea, apples, mushrooms, and wine, so eating healthy foods may help maintain our immune cells on ready alert, effectively priming our gamma-delta T cells that can then provide natural resistance to microbial infections and perhaps tumors. I guess I shouldn't have been so surprised. Tea, after all, is a vegetable infusion, basically drinking a hot water extraction of a dark green leafy vegetable. Within 40 minutes of green tea consumption, we get a boost in antioxidant power in our bloodstreams, within 60 minutes in up-regulation of DNA repair. Tea consumption is associated with a reduced risk of heart disease, stroke, and premature death in general, with each additional cup of green tea a day associated with a 4% lower mortality risk. So maybe, drinking several cups of tea daily can keep the doctor away, as well as the mortician. But what about cancer? There is growing evidence from laboratory population and human interventional studies that tea can exert beneficial disease-preventive effects, and further may actually slow cancer progression. Let's review some of that evidence. Not only do those who drink a lot of tea appear to live years longer than those who drink less, drinking lots of tea may delay the onset of cancer. The women who did get cancer appeared to get it seven years later if they had been drinking lots of tea compared to those who consumed less, whereas men had a three-year delay, the difference male versus female, potentially due to smoking habits. Green tea may be able to interfere with each of the stages of cancer formation, the initiation of the first cancer cell, promotion into a tumor, and then the subsequent progression and spread. Cancer is often initiated when a free radical oxidizes our DNA, causing a mutation. But within 40 minutes of drinking green tea, you can get a nice spike in antioxidant power of your bloodstream. This increase, in turn, made lower oxidative damage to DNA and so decreased the risk of cancer. Furthermore, in terms of genome protective effects protecting our genes, pre-existing oxidation-induced DNA damage was lower after drinking green tea, suggesting that it can boost DNA repair as well. But we didn't know for sure, until now there's a DNA repair enzyme in our body called OGG1, and within one hour of drinking a single cup of green tea, we can boost its activity. Though after a week of tea drinking, we can boost it even higher, so regular intake of green tea may have additional benefits in the prevention and or repair of DNA damage. Tea is so DNA protective it can be used for sperm storage, for fresh samples, until it can be properly refrigerated. And so anti-inflammatory can be used for pain control as a mouthwash after wisdom tooth surgery. And in terms of controlling cancer growth at a dose of green tea compounds that would make it into someone's organs after drinking six cups of tea, it can cause cancer cells to commit suicide. Apoptus programs cell death while leaving normal cells alone. There's lots of chemo agents that can kill cancer through brute force, but that can make normal cells vulnerable too. So green tea appears to be potentially an ideal agent for cancer prevention. A little or no adverse side effects. Efficaceous for multiple cancers at achievable dose levels can be taken orally. We have a sense of how it works by stopping cancer cells from growing, causing them to off themselves. It's cheap and has a history of safe acceptable use. But this was all based on in vitro studies in a test tube. It needs to be evaluated in human trials. Give people with cancer green tea to see if it helps. Finally today we examine the results of studies that use green tea to try to stop or reverse the progression of oral cancer, lung cancer, cervical cancer, and colon cancer cells. Tea consumption may reduce the risk of getting oral cancer. Not only may the consumption of tea boost the antioxidant power of our bloodstream within minutes of consumption, and decrease the amount of free radical DNA damage throughout our systems over time, can also increase the antioxidant power of our saliva, and decrease the DNA damage within the inner cheek cells of smokers, though not as much as stopping smoking altogether. So might this help precancerous oral lesions from turning into cancerous oral lesions? More than 100,000 people develop oral cancer annually worldwide, with a five-year overall survival rate of less than the flip of a coin. Oral cancer frequently arises from precancerous lesions in the mouth, which each have a few percent chance every year from turning cancerous, so what a perfect opportunity to see if green tea can help. 59 patients with precancerous oral lesions were randomized into a tea group, in which capsules of powdered tea extract are given, as well as having the lesions painted with the green tea powder, versus a control group that essentially got sugar pills and were painted with nothing. Within six months, lesions in 11 of the 29 in the tea group shrunk, compared to only 3 out of 30 in the placebo group. The results indicate that tea treatment can improve the clinical manifestations of the oral lesions. The important question, though, is did it prevent them from turning cancerous? But because the trial only lasted a few months, they couldn't tell, but when they scraped some cells off of the lesions, there was a significant drop in DNA-damaged cells within three months in the treatment group, suggesting that things were going in the right direction. Ideally, though, we'd do a longer study to see if they ended up with a less cancer, and while we're at it, how about a study where they just used swallowed tea components, since most people don't finger paint with tea in their mouths? We didn't have such a study, though, until we did. Same extraordinary clinical results with some precancerous lesions shrinking away, and the study lasted long enough to see if fewer people actually got cancer, but there was just as much new cancer in the green tea group as the placebo group. So, a higher response rate—I mean, the lesions looked better, but no improvement in cancer-free survival, which is the whole point. Now, these studies were done mostly on smokers and formal smokers. What about lung cancer? Population studies suggest tea may be protective, but let's put it to the test. 17 patients with advanced lung cancer given up to the equivalent of like 30 cups of green tea a day, but no objective responses were seen. Another study, 49 cancer patients, 21 with lung cancer got between 4 and 25 cups worth of green tea compounds a day, and again, no benefits were found. The only benefit green tea may be able to offer lung cancer patients is to help lessen the burns from the radiation treatments when applied on the skin, as green tea compresses may be able to shorten the duration of the burns. The protective effects of green tea applied topically was also seen in pre-cancerous cervical lesions, where the twice a day direct application of a green tea ointment showed a beneficial response in nearly three quarters of the patients. We heard only about a 10% response in the untreated control group, which is consistent with the anti-cancer effects of green tea compounds on cervical cancer cells in a petri dish. But when women just got green tea extract pills to take, the pills didn't seem to help. I've talked about the potential benefit of green tea wraps for skin cancer, and is there any other cancer where green tea actually comes in direct contact? Yes, colon cancer, which grows from the inner surface of the colon that comes in contact with food and drink. In the colon, tea compounds are fermented by a good gut bacteria into compounds like 3-4-DHPA, which appears to wipe out colon cancer cells, while leaving normal colon cells relatively intact in vitro. So 136 patients with a history of polyps were randomized to get green tea extract pills or not. Now this was a study in Japan, so everyone was already drinking green tea, so effectively this was comparing those who drank 3 cups a day to 4 cups a day. But a year later on colonoscopy, the added green tea group had only half the polyp reoccurrence, and the polyps that did grow were 25% smaller. Why hasn't a larger follow-up study been done since? Perhaps due to the difficulty in raising funds for the study, because green tea is a cheap beverage, not a pharmaceutical. But the good news is that thanks to a major cancer charity in Germany, researchers are currently recruiting for the largest green tea cancer trial to date, in which more than 2,000 patients will be randomized. That's pretty exciting. We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to nutritionfacts.org slash testimonials. We may share it on our social media to help inspire others. To see any graphs, charts, graphics, images, or studies mentioned here, please go to the Nutrition Facts podcast landing page. There you'll find all the detailed information you need, plus links to all the sources we cite for each of these topics. For a vital timely text on the pathogens that cause pandemics, you can order the e-book, audio book, or hard copy of my book, How to Survive a Pandemic. For recipes, check out my new How Not to Diet Cookbook. It's beautifully designed with more than 100 recipes for delicious and nutritious meals. And all proceeds I receive from all my books go to charity. NutritionFacts.org is a non-profit science-based public service where you can sign up for free daily updates on the latest in nutrition research via bite-sized videos and articles. Everything on the website is free. There's no ads, no corporate sponsorships, strictly non-commercial, not selling anything. 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