Green tea cancer prevention -
But the studies in the review were small. The researchers said that we need more scientific studies looking at greater numbers of people. The research looking at whether it prevents prostate cancer generally and in pre cancerous prostate cells is mixed with some showing it might and others not showing any evidence.
But a review study in suggests that the substances in green tea in laboratory research and early clinical trials suggests it may be of benefit.
They suggest we need more research. Researchers did a study in on 39 patients. It was on people at risk of colon and rectal cancer. They found that green tea did not reduce the amount of aberrant crypt foci ACF.
ACF are groups of abnormal tube-like glands in the lining of the colon and rectum. They are early changes in the colon and rectum and can lead to cancer.
We need more evidence from randomised controlled clinical trials. This can help us to know whether green tea has a role in preventing cancer. At the moment it is not possible to draw any firm conclusions because:. In an American study looked at taking a green tea extract called polyphenon E.
They gave it to 42 patients. They all had a type of leukaemia called chronic lymphocytic leukaemia CLL. The people in the trial were not taking any other kind of treatment. The researchers found that in a third of people the number of leukaemic cells lessened. Their lymph nodes also shrank. This was a small trial, but the results were promising.
We need larger trials before we will know whether green tea or its extracts can help people with cancer. In another review study in researchers looked at using green tea and turmeric in people with CLL.
They found limited evidence and mixed results that it might work. Research has shown a possible interaction between green tea and the drug bortezomib Velcade. This early research suggested that green tea might stop Velcade from working well. But we need much more research to find out if green tea has the same effect on humans.
Speak to your doctor if you are taking Velcade and you want to drink green tea. You might have to avoid green tea or the extract EGCG. Some people take EGCG as a supplement in liquid or capsules.
You can find green tea in health food shops, supermarkets, chemists and over the internet. Prices can vary depending on the amount you buy and where you buy it. The quality or grade of green tea can also vary. Usually, better quality green tea costs more. The best quality tea is made from the first leaf buds that come in the spring.
There are no reports of any other harmful effects from using green tea. Always read the product labels. Check with your doctor to find out about possible interactions. This is when you are taking other drugs, herbs, or supplements.
Do remember that green tea contains caffeine. So, pregnant or breastfeeding mothers should use it with caution. It is understandable that you might want to try anything if you think it might help treat or cure your cancer. Only you can decide whether to use a complementary cancer therapy such as green tea.
Many websites promote green tea. But no reputable scientific cancer organisations support any of these claims. Find detailed information and research into some of the many different complementary and alternative therapies used by people with cancer.
A complementary therapy means you can use it alongside your conventional medical treatment. Green tea is prepared from unfermented leaves, the leaves of oolong tea are partially fermented, and black tea is fully fermented.
The more the leaves are fermented, the lower the polyphenol content and the higher the caffeine content. Green tea has the highest polyphenol content while black tea has roughly 2 to 3 times the caffeine content of green tea. Researchers think the health properties of green tea are mostly due to polyphenols, chemicals with potent antioxidant potential.
In fact, the antioxidant effects of polyphenols seem to be greater than vitamin C. The polyphenols in green tea also give it a somewhat bitter flavor.
Polyphenols contained in teas are classified as catechins. Green tea contains six primary catechin compounds: catechin, gallaogatechin, epicatechin, epigallocatechin, epicatechin gallate, and apigallocatechin gallate also known as EGCG. EGCG is the most studied polyphenol component in green tea and the most active.
Green tea also contains alkaloids including caffeine, theobromine, and theophylline. They provide green tea's stimulant effects.
L-theanine, an amino acid compound found in green tea, has been studied for its calming effects on the nervous system. Most green tea dietary supplements are sold as dried leaf tea in capsule form.
Look for standardized extracts of green tea. There are also liquid extracts made from the leaves and leaf buds. The average cup of green tea contains 50 to mg polyphenols antioxidants.
Decaffeinated green tea products contain concentrated polyphenols. Caffeine-free supplements are available. Depending on the brand, 2 to 3 cups of green tea per day for a total of to mg polyphenols or to mg per day of standardized green tea extract is recommended. Caffeine-free products are available and recommended.
The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs contain active substances that can trigger side effects and interact with other herbs, supplements, or medications.
For these reasons, people should take herbs with care, under the supervision of a practitioner knowledgeable in the field of botanical medicine. People with heart problems or high blood pressure, kidney problems, liver problems, stomach ulcers, and psychological disorders, particularly anxiety, should not take green tea.
Pregnant and breastfeeding women should also avoid green tea. People with anemia, diabetes, glaucoma, or osteoporosis should ask their health care provider before drinking green tea or taking an extract.
People who drink large amounts of caffeine, including caffeine from green tea, for long periods of time may experience irritability, insomnia, heart palpitations, and dizziness. Caffeine overdose can cause nausea, vomiting, diarrhea, headaches, and loss of appetite. If you are drinking a lot of tea and start to vomit or have abdominal spasms, you may have caffeine poisoning.
If your symptoms are severe, lower your caffeine intake and see your health care provider. If you are being treated with any of the following medications, you should not drink green tea or take green tea extract without first talking to your health care provider:. Green tea may inhibit the actions of adenosine, a medication given in the hospital for an irregular and usually unstable heart rhythm.
Green tea may increase the effectiveness of beta-lactam antibiotics by making bacteria less resistant to treatment. Caffeine, including caffeine from green tea, may reduce the sedative effects of these medications commonly used to treat anxiety, such as diazepam Valium and lorazepam Ativan.
Beta-blockers, Propranolol, and Metoprolol. Caffeine, including caffeine from green tea, may increase blood pressure in people taking propranolol Inderal and metoprolol Lopressor, Toprol XL. These medications are used to treat high blood pressure and heart disease. Blood-Thinning Medications.
People who take warfarin Coudamin should not drink green tea. Since green tea contains vitamin K, it can make this medication ineffective. Other compounds in green tea may slow blood clotting and therefore increase the blood-thinning effect of these medications.
You should not mix green tea and aspirin because they both prevent blood from clotting. Using the two together may increase your risk of bleeding.
If you are taking medications that promote blood thinning, discuss green tea consumption with your physician. The combination of green tea and chemotherapy medications, specifically doxorubicin and tamoxifen, increased the effectiveness of these medications in laboratory tests.
However, the same results have not been found in studies on people. On the other hand, there have been reports of both green and black tea extracts affecting a gene in prostate cancer cells that may make them less sensitive to chemotherapy drugs.
For that reason, people should talk to their doctors before drinking black and green tea or taking tea extracts while undergoing chemotherapy. Clozapine Clozaril. The effects of the clozapine may be reduced if taken within 40 minutes after drinking green tea. When taken with ephedrine, green tea may cause agitation, tremors, insomnia, and weight loss.
Green tea has been shown to reduce blood levels of lithium, a medication used to treat bipolar disorder. That can make lithium less effective. Monoamine Oxidase Inhibitors MAOIs.
Green tea may cause a severe increase in blood pressure, called a "hypertensive crisis," when taken together with these drugs used to treat depression. Examples of MAOIs include:. Birth control pills. Oral contraceptives can prolong the amount of time caffeine stays in the body, which may increase its stimulating effects.
A combination of caffeine, including caffeine from green tea, and phenylpropanolamine, used in many over-the-counter and prescription cough and cold medications and weight loss products, may cause mania and a severe increase in blood pressure.
The FDA issued a public health advisory in November to warn people of the risk of bleeding in the brain from use of this medication and urged all manufacturers of this drug to remove it from the market. Most drugs that contained phenylpropanolamine have been reformulated without it.
Quinolone antibiotics. Green tea may make these medications more effective and also increase the risk of side effects. These medications include:. Other medications. Green tea, especially caffeinated green tea, may interact with a number for medications, including:.
To be safe, check with your health care provider before drinking or taking green tea if you also take other medications. Baladia E, Basulto J, Manera M, Martinez R, Calbet D.
Effect of green tea or green tea extract consumption on body weight and body composition: systematic review and meta-analysis. Nutr Hosp. Belza A, Toubro S, Astrup A. The effect of caffeine, green tea and tyrosine on thermogenesis and energy intake. Eur J Clin Nutr.
Bettuzzi S, Brausi M, Rizzi F, Castagnetti G, Peracchia G, Corti A. Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study.
Cancer Res. Borrelli F, Capasso R, Russo A, Ernst E. Systematic review: green tea and gastrointestinal cancer risk. Aliment Pharmacol Ther. Mar 1, ;19 5 Boschmann M, Thielecke F.
The effects of epigallocatechingallate on thermogenesis and fat oxidation in obese men: a pilot study. J Am Coll Nutr. Brown AL, Lane J, Holyoak C, Nicol B, Mayes AE, Dadd T. Health effects of green tea catechins in overweight and obese men: a randomised controlled cross-over trial.
Br J Nutr. Cooper R, Morre DJ, Morre DM. Medicinal benefits of green tea: Part I. Review of noncancer health benefits. J Altern Complement Med.
Diepvens K, Westerterp KR, Westerterp-Plantenga MS. Obesity and thermogenesis related to the consumption of caffeine, ephedrine, capsaicin and green tea.
Am J Physiol Regul Integr Comp Physiol. Fritz H, Seely D, Kennedy DA, Fernandes R, Cooley K, Fergusson D. Green tea and lung cancer: a systemic review. Integr Cancer Ther. Fujita H, Yamagami T.
Antihypercholesterolemic effect of Chinese black tea extract in human subjects with borderline hypercholesterolemia. Nutr Res.
Fukino Y, Ikeda A, Maruyama K, Aoki N, Okubo T, Iso H. Randomized controlled trial for an effect of green tea-extract powder supplementation on glucose abnormalities. Gross G, Meyer KG, Pres H, Thielert C, Tawfik H, Mescheder A. J Eur Acad Dermatol Venereol. Hartley L, Flowers N, Holmes J, et al.
Green and black tea for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. Heck AM, DeWitt BA, Lukes AL. Potential interactions between alternative therapies and warfarin.
Am J Health Syst Pharm. Hsu CH, Liao YL, Lin SC, Tsai TH, Huang CJ, Chou P. Does supplementation with green tea extract improve insulin resistance in obese type 2 diabetics?
A randomized, double-blind, and placebo-controlled clinical trial. Altern Med Rev. Inoue M, Tajima K, Mizutani M, et al. Regular consumption of green tea and the risk of breast cancer recurrence: follow-up study from the Hospital-based Epidemiologic Research Program at Aichi Cancer Center HERPACC , Japan.
Cancer Lett. Jian L, Xie LP, Lee AH, Binns CW. Protective effect of green tea against prostate cancer: a case-control study in southeast China.
Int J Cancer Jan 1, ; 1 Jiao H, Hu G, Gu D, Ni X. Having a promising efficacy on type II diabetes, it's definitely a green tea time. Curr Med Chem. National Foundation for Cancer Research NFCR is a c 3 tax-exempt nonprofit organization.
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Xancer all the talk about the Gresn of drinking green tea in recent years are prevemtion claims Prevenhion a chemical found in green tea—epigallocatechingallate EGCG —may be a powerful Green tea cancer prevention against breast cancer. Canced low rate Lower cholesterol for a healthier heart breast cancer cancfr some other cancers in regions where people drink large amounts Green tea cancer prevention green tea is what made researchers start examining the relationship. Before you put faith in your teacup, it's important to dig into the science—what's known and what needs more examination. Green tea is made from the leaves of the Camellia sinensisa plant native to parts of Asia. The same plant also produces white, oolong, and black teas, and each type represents a progressive stage in the leaves' development. Green comes after white and appears to be the stage when certain compounds are at their highest concentrations. Green tea's cancer-fighting reputation comes from its polyphenols, which are chemicals that have antioxidant properties.Drinking green Green tea cancer prevention cacner often touted as a natural approach to reducing your cancer tra. Indeed, green tea is exceptionally high prevengion antioxidants, which could theoretically combat cancer te neutralizing free radicals chemical Nutrient-rich weight management known to damage DNA.
While research on the prevfntion of green tea on the development and growth tae cancerous tumors tda animals has been promising, studies Ggeen humans have Green tea cancer prevention pgevention results so far.
Green Green tea cancer prevention consumption may have preventioon protective effect on oral hea, according to Muscle development stability report published canccer Oral Oncology.
Researchers analyzed 19 previously canccer studies cancerr a total preevntion 4, hea and found canced of Effective anti-wrinkle treatments association between green tea consumption but not black tea consumption prsvention oral cancer risk.
Green tea cancer prevention another published prebention, investigators analyzed preventlon studies most were observational studies with a total of more than 1. Results revealed "limited to moderate evidence" that green tea preventkon Green tea cancer prevention the risk of lung cancer, fea Green tea cancer prevention men.
The review's findings prfvention suggested that orevention tea consumption may be Gree to fancer risk of prostate preventiom. However, evidence for green tea's Green tea cancer prevention on csncer types of cancer was African mango extract dietary supplement limited or preevention.
Some Grfen even indicated that Ggeen tea consumption pevention actually increase prfvention risk of bladder cancer. In another research review cancwr in preventoin British Journal Fiber optic technology advancements Nutrition cxncer, investigators analyzed 18 previously published studies.
Green tea consumption was significantly inversely associated with a five percent lower risk of cardiovascular disease and all-cause mortality cnacer, Green tea cancer prevention not Geren mortality from cancer.
Published in the Annals of Epidemiologya pregention study following 90, people in Japan Gree that green tea was inversely associated with mortality from heart disease and mortality from cerebrovascular disease and respiratory disease in men.
No association was found between green tea and total cancer mortality. As a whole, the evidence that green tea consumption can reduce the risk of cancer is conflicting. Large-scale clinical trials—the kind of research you want to see to put full stock in a treatment—need to be conducted before drinking green tea can be considered an effective strategy to reduce cancer risk.
Although it can be discouraging to hear that there is no clear answer yet, researchers do state that green tea appears to be safe for most people when consumed in moderate amounts.
Drinking green tea may offer other health benefits, including reduced risk of stroke and periodontal disease. If you're considering drinking it regularly, be sure to consult your healthcare provider first to discuss whether it's appropriate for you. People with certain conditions and those taking medications such as bortezomib may have to avoid it.
To reduce your overall cancer risk, be sure to get routine cancer screening tests, follow a balanced, healthful diet that includes plenty of fruits, vegetables, and other foods from plant sources, maintain a healthy weight, exercise regularly, and avoid smoking.
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Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Boehm K, Borrelli F, Ernst E, Habacher G, Hung SK, Milazzo S, Horneber M.
Green tea Camellia sinensis for the prevention of cancer. Cochrane Database Syst Rev. Saito E, Inoue M, Sawada N, et al. Association of green tea consumption with mortality due to all causes and major causes of death in a Japanese population: the Japan Public Health Center-based Prospective Study JPHC Study.
Ann Epidemiol. Tang J, Zheng JS, Fang L, Jin Y, Cai W, Li D. Tea consumption and mortality of all cancers, CVD and all causes: a meta-analysis of eighteen prospective cohort studies. Br J Nutr. Wang W, Yang Y, Zhang W, Wu W.
Association of tea consumption and the risk of oral cancer: a meta-analysis. Oral Oncol. See Our Editorial Process. Meet Our Medical Expert Board. Share Feedback. Was this page helpful? Thanks for your feedback! What is your feedback? Related Articles. You may accept or manage your choices by clicking below, including your right to object where legitimate interest is used, or at any time in the privacy policy page.
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: Green tea cancer prevention| Does Green Tea Reduce the Risk of Cancer? - NFCR | In , the internationally respected Cochrane Collaboration reviewed all the clinical studies on the effect of green tea on cancer prevention or death from cancer. The results were conflicting — some showed that green tea could help prevent cancer, some showed that it had no effect and some showed that it increased the risk of some cancers. Subsequent reviews and analyses found similar results. This means that, overall, the studies on green tea and cancer are inconclusive for all types of cancer, and more large-scale clinical trials need to be done before we can be sure whether green tea helps to prevent or cure cancer. Drinking green tea in moderate amounts is not associated with any significant harmful effects. However, evaluations by the International Agency for Research on Cancer determined that drinking any very hot beverage above 65°C is probably a cause of oesophageal cancer. In order to minimise risk, leave hot drinks to cool for about four minutes after boiling before drinking. Go to cancer. Highest grade Japanese sencha green tea, ceremonial matcha and roasted brown rice are blended into a toasty antioxidant packed Genmaicha Organic Matcha Tea. Organic Gunpowder organic green tea is filled with healthy antioxidants known to support a healthy heart, promote fat loss, and strengthen the immune system. Treat yourself to the highest-grade Japanese Organic Gyokuro Green Tea. Shade grown making its whole tea leaves sweet with a special umami flavor. Organic Lung Ching or often called Dragonwell organic green tea is known for its mild slightly sweet flavor. Its pan-roasted from the Longjing region in China. Organic Chun Lu Tea from Fraser tea is a rare organic green tea that's hard to find outside of China. Organic Chun Lu Tea has pleasant mellow flavor. Love Matcha? This sweet blend is handcrafted by Fraser Tea to create a bold and refreshing beverage. Try this brewed or sprinkle it on yogurt and snacks for a boost of flavor! Perfect addition to lattes and smoothies. Boost your energy while enjoying the tropical flavors of Mango Peach Matcha Organic Green Tea. Convenient green tea powder for smoothies, lattes, or iced tea. Organic Japanese First Harvest Matcha Ceremonial Grade is considered the highest grade matcha available and is packed with the anti-oxidants benefits of 10 cups of conventional green tea.. Super Energized Organic green tea combines yerba mate and green tea to give you that extra pick-up that you sometimes need. Available loose leaf or in Non-GMO plant based sachets. Enjoy the hand-picked downy tea buds of our premium grade Silver Needle Organic White Tea. Pure and delicate with light floral notes of honeysuckle. Rich with powerful antioxidants, this matcha blend is a winner! Choose our masterfully blended whole leaf Organic Green Tea. Delicious addition to lattes, smoothies, baked goods and more. Tea time may be regarded as good for your health. At Fraser Tea every variety offered is crafted organically in small batches and made with only organic flavors. For those seeking a beverage that is healthful and may have the ability to prevent or reduce the risk of cancer, several varieties boast high concentrations of polyphenols, catechins and enzymes that can protect healthy cells. Go for green tea first as it may aid in cancer prevention. Fraser Tea varieties like Kyoto Cherry Organic Green Tea , Blueberry Matcha , Vanilla Matcha , Raspberry Matcha , Mango Matcha , Imperial Matcha and Genmatcha Organic Green Tea boast significant benefits. Traditional teas like Gyokuro Green Organic Green Tea , Sencha Organic Green Tea , Lung Ching Organic Green Tea , Chun Lu Organic Green Tea and Bancha Organic Green Tea are packed with cancer-fighting properties. The tasty Minty Green Organic Green Tea or spicy Cinnamon Swirl Matcha Organic Green Tea make it easy to keep a delicious cup of tea nearby anytime. |
| Plant Description | They found limited evidence and mixed results that it might work. Research has shown a possible interaction between green tea and the drug bortezomib Velcade. This early research suggested that green tea might stop Velcade from working well. But we need much more research to find out if green tea has the same effect on humans. Speak to your doctor if you are taking Velcade and you want to drink green tea. You might have to avoid green tea or the extract EGCG. Some people take EGCG as a supplement in liquid or capsules. You can find green tea in health food shops, supermarkets, chemists and over the internet. Prices can vary depending on the amount you buy and where you buy it. The quality or grade of green tea can also vary. Usually, better quality green tea costs more. The best quality tea is made from the first leaf buds that come in the spring. There are no reports of any other harmful effects from using green tea. Always read the product labels. Check with your doctor to find out about possible interactions. This is when you are taking other drugs, herbs, or supplements. Do remember that green tea contains caffeine. So, pregnant or breastfeeding mothers should use it with caution. It is understandable that you might want to try anything if you think it might help treat or cure your cancer. Only you can decide whether to use a complementary cancer therapy such as green tea. Many websites promote green tea. But no reputable scientific cancer organisations support any of these claims. Find detailed information and research into some of the many different complementary and alternative therapies used by people with cancer. A complementary therapy means you can use it alongside your conventional medical treatment. It may help you to feel better and cope better with your cancer and treatment. An alternative therapy is generally used instead of conventional medical treatment. This section has information about the safety of complementary cancer therapies and alternative cancer therapies. Find organisations, support groups, books, websites and other resources about complementary and alternative therapies. Treatments can include surgery, radiotherapy and drug treatments such as chemotherapy, hormone therapy or targeted cancer drugs. Find out about treatments and how to cope with side effects. Cancer Chat is our fully moderated forum where you can talk to others affected by cancer, share experiences, and get support. Cancer Chat is free to join and available 24 hours a day. Visit the Cancer Chat forum. About Cancer generously supported by Dangoor Education since Questions about cancer? Call freephone 9 to 5 Monday to Friday or email us. Skip to main content. Home About cancer Treatment for cancer Complementary and alternative therapies Individual therapies Green tea Chinese tea. Summary Green tea is made from the unfermented leaves of the plant Camellia sinensis Manufacturers promote it as a dietary supplement and claim that it helps control blood sugar, cholesterol, blood pressure and weight There is not enough reliable evidence that it might prevent certain cancers Green tea can have side effects What is green tea? Manufacturers promote it as a dietary supplement. They claim that it helps control: blood sugar cholesterol blood pressure weight People also drink it because they believe it might prevent certain types of cancer. Why people with cancer use it There is no real evidence that green tea can help treat cancer. People with cancer also drink green tea because they believe it might: boost their immune system which might help them fight their cancer improve health, energy levels and well being get rid of toxins in the body give them some control over their cancer and its treatment treat their cancer if no other conventional treatment can The media has also promoted black tea as an anti-cancer agent. How you have it Green tea, like other teas on the market, comes as ready-made tea bags or leaves. Side effects Green tea is generally safe to drink, but it contains caffeine which is a stimulant. If you take it in large amounts, it can cause you to: have difficulty sleeping have headaches feel jittery or shaky EGCG in green tea, when taken in large quantities, can cause sickness and an upset stomach in some people. People who are undergoing chemotherapy should ask their doctors before drinking green or black tea, or taking tea supplements. Skin cancer. The main polyphenol in green tea is epigallocatechin gallate EGCG. Scientific studies suggest that EGCG and green tea polyphenols have anti-inflammatory and anticancer properties that may help prevent the development and growth of skin tumors. Stomach cancer. Laboratory studies have found that green tea polyphenols inhibit the growth of stomach cancer cells in test tubes, however, studies in people have been less conclusive. In two studies that compared green tea drinkers with nondrinkers, researchers found that people who drank tea were about half as likely to develop stomach cancer and stomach inflammation as those who did not drink green tea. However, a clinical study with more than 26, men and women in Japan found no association between green tea and stomach cancer risk. Some studies even suggest that green tea may increase the risk of stomach cancer. Green tea may help reduce inflammation associated with Crohn disease and ulcerative colitis, the two types of IBD. If green tea proves to help prevent colon cancer, it would also help those with IBD because they are at higher risk for colon cancer. Green tea has been used traditionally to control blood sugar levels. Animal studies suggest that green tea may help prevent the development of type 1 diabetes and slow the progression once it has developed. In people with type 1 diabetes, their bodies make little or no insulin, which helps convert glucose or sugar into energy. Green tea may help regulate glucose in the body. Research also suggests that regular consumption of green tea may help manage type 2 diabetes. Population-based studies have shown that men who drink more than 10 cups of green tea per day are less likely to develop liver problems. Green tea also seems to protect the liver from the damaging effects of toxic substances such as alcohol. Animal studies have shown that green tea helps protect against liver tumors in mice. Results from several animal and human studies suggest that plant chemicals in green tea called catechins, may help treat viral hepatitis, an inflammation of the liver. In these studies, catechin was used by itself in very high amounts. It is not clear whether green tea, which has a lower concentration of catechins, would have the same benefits. It is important to note that 10 cups of green tea a day could cause problems due to high levels of caffeine. Ask your doctor about the best way to include green tea in your treatment. Clinical studies suggest that green tea extract may boost metabolism and help burn fat. One study found that the combination of green tea and caffeine improved weight loss and maintenance in people who were overweight and moderately obese. However, other studies show no benefit. Preliminary studies suggest that drinking green tea can help prevent dental cavities. More research is needed. Green tea may also be useful in inflammatory diseases, such as arthritis. Research suggests that green tea may help arthritis by reducing inflammation and slowing the breakdown of cartilage. Chemicals in green tea may help treat genital warts, treat dermatologic conditions, and prevent symptoms of colds and flu. Green tea may play a role in preventing Parkinson disease, cognitive decline, and osteoporosis. Studies also show that drinking green tea is associated with reduced risk of dying from any cause. Green, black, and oolong tea are all derived from the leaves of the Camellia sinensis plant. Originally cultivated in East Asia, this plant grows as large as a shrub or tree. Today, Camellia sinensis grows throughout Asia and parts of the Middle East and Africa. People in Asian countries more commonly consume green and oolong tea while black tea is most popular in the United States. Green tea is prepared from unfermented leaves, the leaves of oolong tea are partially fermented, and black tea is fully fermented. The more the leaves are fermented, the lower the polyphenol content and the higher the caffeine content. Green tea has the highest polyphenol content while black tea has roughly 2 to 3 times the caffeine content of green tea. Researchers think the health properties of green tea are mostly due to polyphenols, chemicals with potent antioxidant potential. In fact, the antioxidant effects of polyphenols seem to be greater than vitamin C. The polyphenols in green tea also give it a somewhat bitter flavor. Polyphenols contained in teas are classified as catechins. Green tea contains six primary catechin compounds: catechin, gallaogatechin, epicatechin, epigallocatechin, epicatechin gallate, and apigallocatechin gallate also known as EGCG. EGCG is the most studied polyphenol component in green tea and the most active. Green tea also contains alkaloids including caffeine, theobromine, and theophylline. They provide green tea's stimulant effects. L-theanine, an amino acid compound found in green tea, has been studied for its calming effects on the nervous system. Most green tea dietary supplements are sold as dried leaf tea in capsule form. Look for standardized extracts of green tea. There are also liquid extracts made from the leaves and leaf buds. The average cup of green tea contains 50 to mg polyphenols antioxidants. Decaffeinated green tea products contain concentrated polyphenols. Caffeine-free supplements are available. Depending on the brand, 2 to 3 cups of green tea per day for a total of to mg polyphenols or to mg per day of standardized green tea extract is recommended. Caffeine-free products are available and recommended. The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs contain active substances that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, people should take herbs with care, under the supervision of a practitioner knowledgeable in the field of botanical medicine. People with heart problems or high blood pressure, kidney problems, liver problems, stomach ulcers, and psychological disorders, particularly anxiety, should not take green tea. Pregnant and breastfeeding women should also avoid green tea. People with anemia, diabetes, glaucoma, or osteoporosis should ask their health care provider before drinking green tea or taking an extract. People who drink large amounts of caffeine, including caffeine from green tea, for long periods of time may experience irritability, insomnia, heart palpitations, and dizziness. Caffeine overdose can cause nausea, vomiting, diarrhea, headaches, and loss of appetite. If you are drinking a lot of tea and start to vomit or have abdominal spasms, you may have caffeine poisoning. If your symptoms are severe, lower your caffeine intake and see your health care provider. If you are being treated with any of the following medications, you should not drink green tea or take green tea extract without first talking to your health care provider:. Green tea may inhibit the actions of adenosine, a medication given in the hospital for an irregular and usually unstable heart rhythm. Green tea may increase the effectiveness of beta-lactam antibiotics by making bacteria less resistant to treatment. Caffeine, including caffeine from green tea, may reduce the sedative effects of these medications commonly used to treat anxiety, such as diazepam Valium and lorazepam Ativan. Beta-blockers, Propranolol, and Metoprolol. Caffeine, including caffeine from green tea, may increase blood pressure in people taking propranolol Inderal and metoprolol Lopressor, Toprol XL. These medications are used to treat high blood pressure and heart disease. Blood-Thinning Medications. People who take warfarin Coudamin should not drink green tea. Since green tea contains vitamin K, it can make this medication ineffective. Other compounds in green tea may slow blood clotting and therefore increase the blood-thinning effect of these medications. You should not mix green tea and aspirin because they both prevent blood from clotting. Using the two together may increase your risk of bleeding. If you are taking medications that promote blood thinning, discuss green tea consumption with your physician. The combination of green tea and chemotherapy medications, specifically doxorubicin and tamoxifen, increased the effectiveness of these medications in laboratory tests. However, the same results have not been found in studies on people. On the other hand, there have been reports of both green and black tea extracts affecting a gene in prostate cancer cells that may make them less sensitive to chemotherapy drugs. For that reason, people should talk to their doctors before drinking black and green tea or taking tea extracts while undergoing chemotherapy. Clozapine Clozaril. The effects of the clozapine may be reduced if taken within 40 minutes after drinking green tea. When taken with ephedrine, green tea may cause agitation, tremors, insomnia, and weight loss. Green tea has been shown to reduce blood levels of lithium, a medication used to treat bipolar disorder. That can make lithium less effective. Monoamine Oxidase Inhibitors MAOIs. Green tea may cause a severe increase in blood pressure, called a "hypertensive crisis," when taken together with these drugs used to treat depression. Examples of MAOIs include:. Birth control pills. Oral contraceptives can prolong the amount of time caffeine stays in the body, which may increase its stimulating effects. A combination of caffeine, including caffeine from green tea, and phenylpropanolamine, used in many over-the-counter and prescription cough and cold medications and weight loss products, may cause mania and a severe increase in blood pressure. The FDA issued a public health advisory in November to warn people of the risk of bleeding in the brain from use of this medication and urged all manufacturers of this drug to remove it from the market. Most drugs that contained phenylpropanolamine have been reformulated without it. Quinolone antibiotics. Green tea may make these medications more effective and also increase the risk of side effects. These medications include:. Other medications. Green tea, especially caffeinated green tea, may interact with a number for medications, including:. To be safe, check with your health care provider before drinking or taking green tea if you also take other medications. Baladia E, Basulto J, Manera M, Martinez R, Calbet D. Effect of green tea or green tea extract consumption on body weight and body composition: systematic review and meta-analysis. Nutr Hosp. Belza A, Toubro S, Astrup A. The effect of caffeine, green tea and tyrosine on thermogenesis and energy intake. Eur J Clin Nutr. Bettuzzi S, Brausi M, Rizzi F, Castagnetti G, Peracchia G, Corti A. Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study. Cancer Res. Borrelli F, Capasso R, Russo A, Ernst E. Systematic review: green tea and gastrointestinal cancer risk. Aliment Pharmacol Ther. Mar 1, ;19 5 Boschmann M, Thielecke F. The effects of epigallocatechingallate on thermogenesis and fat oxidation in obese men: a pilot study. J Am Coll Nutr. Brown AL, Lane J, Holyoak C, Nicol B, Mayes AE, Dadd T. Green tea is made from the dried leaves of the plant Camellia sinensis, and contains chemicals known as polyphenols. These are antioxidants that may help to prevent DNA damage caused by free radicals, and this is why some people think that tea can help to prevent or cure cancer. Some laboratory studies have shown that tea polyphenols can stop cancer cells from growing; however, studies in humans show variable results. In , the internationally respected Cochrane Collaboration reviewed all the clinical studies on the effect of green tea on cancer prevention or death from cancer. The results were conflicting — some showed that green tea could help prevent cancer, some showed that it had no effect and some showed that it increased the risk of some cancers. |
| Tea for Cancer Prevention | It is not clear whether green tea, which has a lower concentration of catechins, would have the same benefits. Article CAS PubMed Google Scholar Yang J, Mao QX, Xu HX, Ma X, Zeng CY. Article PubMed PubMed Central Google Scholar Lin YW, Hu ZH, Wang X, Mao QQ, Qin J, Zheng XY, et al. Diabetes Res Clin Pract. Why Free Radicals Are Important. Dietary strategies for weight loss maintenance. Of importance to many people being treated for breast cancer is the possible effect on long-term treatment—hormonal therapy—for breast cancer. |
| Green tea (Chinese tea) | An inverse association between tea consumption and colorectal cancer risk. Green tea has long been linked with positive health outcomes. Cite this article Abe, S. Wang Y, Zhao Y, Chong F, Song M, Sun Q, Li T, et al. Selection criteria:. Jan 1, ;38 1 |
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