A study performed on 40 participants at Ohio State University found that green tea extract lowered blood sugar and decreased gut inflammation and permeability in both healthy people and people with metabolic syndrome. According to the American Heart Association , "Studies show tea consumption, along with a heart-healthy diet, may improve some brain function.

One study in Neuropharmacology revealed that "people who took milligrams of L-theanine made fewer errors in an attention task than those in the placebo group.

Drinking 50 mg of caffeine or combining the L-theanine and caffeine also improved people's focus. Green tea may help defend against heart disease by supporting healthy cholesterol.

Studies also show that green tea may reduce blood sugar levels and help prevent type 2 diabetes. Experts believe that catechins, one type of antioxidant found in green tea, may be responsible for this cholesterol-lowering effect. Green tea can help to soothe the symptoms of gastrointestinal disorders and relieve bloating by eliminating the buildup of gas in the intestine.

The results revealed the proportion of Bifidobacteria a type of good bacteria in your gut increased proportional to green tea consumption, which means that green tea consumption might help act as a prebiotic and improve the colon environment.

The antioxidants found in green tea, particularly polyphenols, aid in protecting cells from oxidative damage, a factor that contributes to several chronic illnesses and cancers. Polyphenols can help prevent the formation of free radicals that may cause damage to or the death of cells, which may ultimately reduce the risk of cancer.

While green tea, in its natural state, is much more beneficial to one's health than heavily sweetened beverages, a person may face negative side effects if they consume too much.

For example, drinking too much tea may lead to an iron deficiency because tea is rich in tannins, which can bind to iron and prevent it from being absorbed in the digestive tract. Many people enjoy a warm cup of tea after a meal to help encourage digestion. However, green tea can have the opposite effect.

If you follow up an iron-rich meal with a cup of green tea with the best of intentions, the tannins may prevent your body from absorbing this important mineral. It's important to remember that green tea is not caffeine-free , and similar to other caffeinated drinks, consuming too much green tea can cause symptoms such as anxiety, restlessness, jitters, headache, nausea, increased heart rate or trouble sleeping.

While everyone has different sensitivity levels to caffeine, the Food and Drug Administration cites milligrams per day —about 10 cups of green tea—as the maximum amount of caffeine healthy adults should consume each day.

The promising health benefits of green tea may be negated with the inclusion of added sugar or even an excess amount of honey.

Boiling water can potentially reduce the flavor properties in tea, and might make it taste bitter. Once warm, add the water to a mug and then add the tea leaves or tea bag. Steep for three minutes. Enjoy your green tea warm, but not piping hot.

For most people, drinking green tea in moderate amounts each day is safe. Drinking three to five cups per day is a safe zone for reaping all of the health benefits it offers, without entering a space of excess where potential risks exist.

The best time of day to drink green tea is in the morning or early afternoon so the caffeine will not impact a healthy sleep routine, and one to two hours after meals to help aid in digestion.

Several studies have found that green tea helps lower blood pressure. Scientists at the University of California found that antioxidants in tea help open ion channels, which can relax the muscles that line blood vessels. When the cells relax, the blood vessels dilate and, as a result, blood pressure is reduced.

Derocha says that the tannins, a class of polyphenol, may also give people an upset stomach , among other potential side effects. Finally, Derocha says that black tea can interfere with mental health drugs, and you should speak to your doctor if you are taking medication or trying a new tea.

Powerful antioxidants in green tea — especially one called epigallocatechin gallate, or EGCG — can help prevent atherosclerosis and plaque buildup in the arteries.

And drinking green tea is also associated with a lower risk of cardiovascular diseases, especially in habitual tea drinkers, according to a review published in May in Food Science and Human Wellness. After surveying , participants in China, scientists found drinking green tea was linked with approximately 25 percent lower risk of living with heart disease or after a stroke, the chance of dying from heart disease and stroke, and general death.

Participants were split between two groups: habitual tea drinkers three times or more a week or not. This might not be doable for everyone. Derocha says that people with caffeine sensitivity should watch how much green tea they drink, just like black tea.

A study published in Food Chemistry found that white tea may protect the DNA of normal cells against cell damage from colon cancer , acting as a potential chemotherapeutic agent by inhibiting colon cancer cells. Regarding heart health, research is limited.

White tea does contain caffeine, which can speed your heart rate or increase your risk for high blood pressure. Oolong tea is crushed tea leaves that have been oxidized for a period of time and then heated to stop the process.

A clinical study published in the British Journal of Nutrition found that oolong tea may help lower cholesterol levels in the study population from Shantou, China. While the results showed that oolong tea was able to increase HDL cholesterol , it was inconsistent with previous studies.

Derocha cautions that oolong has a laxative effect and to be wary about what that can do to the body. Like other teas, it can contradict medications like blood thinners.

This herbal tea is notorious for helping people sleep at night because it contains flavanoids, per research. Sleep is also one of the best tools for dealing with inflammation or healing from an injury, she notes. Getting restful sleep is necessary too.

A study published in March in the Journal of the American Heart Association found that poor sleep quality was associated with increased risk of major cardiovascular diseases. Sometimes the tea works so well that doctors tell patients not to drink chamomile before surgery because it can cause them to be too relaxed and have an adverse effect with anesthesia, says Derocha.

Patients with a coronary artery stent or who are taking aspirin or warfarin blood thinners should consult their doctor before drinking chamomile tea because it may increase the risk for internal bleeding.

Though ginseng has not been officially evaluated by the U. Studies in animals and test tubes suggest that polyphenols in green tea inhibit the growth of breast cancer cells. In one study of women with various stages of breast cancer, researchers found that women who drank the most green tea had the least spread of cancer.

It was especially true in premenopausal women in the early stages of breast cancer. They also found that women with early stages of the disease who drank at least 5 cups of tea daily before being diagnosed with cancer were less likely to experience a recurrence after they finished treatment.

However, women with late stages of breast cancer had little or no improvement from drinking green tea. There is no clear evidence one way or the other about green tea and breast cancer prevention.

In one very large study, researchers found that drinking tea, green or any other type, was not associated with a reduced risk of breast cancer. Ovarian cancer. In a study done with ovarian cancer patients in China, researchers found that women who drank at least one cup of green tea per day lived longer with the disease than those who did not drink green tea.

In fact, those who drank the most tea, lived the longest. But other studies found no beneficial effects. Colorectal cancer. Studies on the effects of green tea on colon or rectal cancer have showed conflicting results.

Some studies show decreased risk in those who drink the tea, while others show increased risk. In one study, women who drank 5 or more cups of green tea per day had a lower risk of colorectal cancer compared to non-tea-drinkers. However, there was no protective effect for men. Other studies show that drinking tea regularly may reduce the risk of colorectal cancer in women.

More research is needed before researchers can recommend green tea for the prevention of colorectal cancer. Esophageal cancer. Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells. However, studies in people have produced conflicting findings.

For example, one large-scale population-based study found that green tea offered protection against the development of esophageal cancer, particularly among women.

Another population-based study found just the opposite, green tea consumption was associated with an increased risk of esophageal cancer. In fact, the stronger and hotter the tea, the greater the risk.

Given these conflicting results, more research is needed before scientists can recommend green tea for the prevention of esophageal cancer. Lung cancer. While green tea polyphenols have been shown to inhibit the growth of human lung cancer cells in test tubes, few clinical studies have looked at the link between drinking green tea and lung cancer in people, and the studies that have been done show conflicting results.

One population-based study found that Okinawan tea, similar to green tea but partially fermented, was associated with lower lung cancer risk, particularly among women.

But a second study found that green tea and black tea increased the risk of lung cancer. More studies are needed before researchers can draw any conclusions about green tea and lung cancer. Green tea should not be used by patients on bortezomib therapy. Pancreatic cancer. In one large-scale clinical study researchers compared green tea drinkers with nondrinkers and found that those who drank the most tea were less likely to develop pancreatic cancer.

This was particularly true for women, those who drank the most green tea were half as likely to develop pancreatic cancer as those who drank less tea. However, it is not clear from this population-based study whether green tea is solely responsible for lowering pancreatic cancer risk.

More studies are needed before researchers can recommend green tea for the prevention of pancreatic cancer. Prostate cancer. Laboratory studies have found that green tea extracts prevent the growth of prostate cancer cells in test tubes. A large clinical study in Southeast China found that the risk of prostate cancer went down with increasing frequency, duration, and quantity of green tea consumption.

However, both green and black tea extracts also stimulated genes that cause cells to be less sensitive to chemotherapy drugs. 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.

However, it is not possible to know for sure from these studies whether green tea actually prevents cancer in people. Early clinical studies suggest that the polyphenols in tea, especially green tea, may play an important role in the prevention of cancer.

Researchers also believe that polyphenols help kill cancerous cells and stop them from growing. Bladder cancer. In one study that compared people with and without bladder cancer, researchers found that women who drank black tea and powdered green tea were less likely to develop bladder cancer.

A follow-up clinical study by the same group of researchers revealed that people with bladder cancer, particularly men, who drank green tea had a better 5-year survival rate than those who did not drink green tea.

People with cancer should consult with their doctor before adding tea to their regimen. Breast cancer. Studies in animals and test tubes suggest that polyphenols in green tea inhibit the growth of breast cancer cells.

In one study of women with various stages of breast cancer, researchers found that women who drank the most green tea had the least spread of cancer. It was especially true in premenopausal women in the early stages of breast cancer.

They also found that women with early stages of the disease who drank at least 5 cups of tea daily before being diagnosed with cancer were less likely to experience a recurrence after they finished treatment.

However, women with late stages of breast cancer had little or no improvement from drinking green tea. There is no clear evidence one way or the other about green tea and breast cancer prevention. In one very large study, researchers found that drinking tea, green or any other type, was not associated with a reduced risk of breast cancer.

Ovarian cancer. In a study done with ovarian cancer patients in China, researchers found that women who drank at least one cup of green tea per day lived longer with the disease than those who did not drink green tea. In fact, those who drank the most tea, lived the longest.

But other studies found no beneficial effects. Colorectal cancer. Studies on the effects of green tea on colon or rectal cancer have showed conflicting results. Some studies show decreased risk in those who drink the tea, while others show increased risk.

In one study, women who drank 5 or more cups of green tea per day had a lower risk of colorectal cancer compared to non-tea-drinkers. However, there was no protective effect for men.

Other studies show that drinking tea regularly may reduce the risk of colorectal cancer in women. More research is needed before researchers can recommend green tea for the prevention of colorectal cancer. Esophageal cancer. Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells.

However, studies in people have produced conflicting findings. For example, one large-scale population-based study found that green tea offered protection against the development of esophageal cancer, particularly among women.

Another population-based study found just the opposite, green tea consumption was associated with an increased risk of esophageal cancer.

In fact, the stronger and hotter the tea, the greater the risk. Given these conflicting results, more research is needed before scientists can recommend green tea for the prevention of esophageal cancer. Lung cancer. While green tea polyphenols have been shown to inhibit the growth of human lung cancer cells in test tubes, few clinical studies have looked at the link between drinking green tea and lung cancer in people, and the studies that have been done show conflicting results.

One population-based study found that Okinawan tea, similar to green tea but partially fermented, was associated with lower lung cancer risk, particularly among women.

But a second study found that green tea and black tea increased the risk of lung cancer. More studies are needed before researchers can draw any conclusions about green tea and lung cancer. Green tea should not be used by patients on bortezomib therapy.

Pancreatic cancer. In one large-scale clinical study researchers compared green tea drinkers with nondrinkers and found that those who drank the most tea were less likely to develop pancreatic cancer.

This was particularly true for women, those who drank the most green tea were half as likely to develop pancreatic cancer as those who drank less tea. However, it is not clear from this population-based study whether green tea is solely responsible for lowering pancreatic cancer risk.

More studies are needed before researchers can recommend green tea for the prevention of pancreatic cancer. Prostate cancer. Laboratory studies have found that green tea extracts prevent the growth of prostate cancer cells in test tubes. A large clinical study in Southeast China found that the risk of prostate cancer went down with increasing frequency, duration, and quantity of green tea consumption.

However, both green and black tea extracts also stimulated genes that cause cells to be less sensitive to chemotherapy drugs. 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.

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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.

Go ahead - eat more of these! As for your cup, you can feel great about filling it up with green tea more often. Significant science shows green tea promotes heart health, but how does it do that? In laboratories, scientists have found that green tea contains natural compounds that can help with some major cardiovascular issues, such as high bad cholesterol, inflammation, and the health of heart cells.

Famous for the amazing health-promoting catechins they contain, green tea leaves have long been seen as a beneficial plant to include in your day. In fact, green tea is one of the most consumed drinks on the planet, second only to water.

EGCG appears to improve how well the lining of blood vessels works. When blood vessels function at their best, the highways all the way to the tiny side-streets of your cardiovascular system can flow well, meaning all parts of your body can get the oxygen and nutrients they need to work.

Interestingly, EGCG from green tea leaves encourages healthy growth and formation of blood vessel cells, all while protecting the smooth muscle cells of blood vessels from homocysteine.

High homocysteine levels can damage arteries, and increase the risk of blockages in blood vessels. High cholesterol can refer to two things: high low-density lipoprotein cholesterol LDL cholesterol , and high total cholesterol. In a review of research, published in the Nutrition Journal, green tea consumption lowers LDL cholesterol and total cholesterol.

Sometimes people call LDL cholesterol, bad cholesterol. Cholesterol is a waxy substance that can build up in the walls of arteries, a process called atherosclerosis. Plaques can build-up and restrict blood flow, cause inflammation, or even burst, triggering a blood clot.

Ultimately, plaque increases the risk of heart attack and stroke. Researchers say, green tea appears to slow bad cholesterol LDL cholesterol from being oxidized, a process that leads to plaque formation in blood vessels, that leads to atherosclerosis. What a great reason to heart green tea — it may help prevent plaque from forming in blood vessels.

Of note, studies show plaque appears to also play a role in the development of cognitive impairment that can occur with age. Hypertension occurs when the cardiovascular system is working harder than it should, putting extra stress on it.

Several studies have found frequently drinking green tea was linked to lower blood pressure, including a group of obese hypertensive women, who saw a beneficial effect after drinking green tea for just 4 weeks.

In one study , the systolic blood pressure and diastolic blood pressure significantly lowered in a randomized control study with 79 hypertensive adults ages 20 — 55 years attributed to the addition to their diets of the healthy compounds, called epicatechins, found in green tea.

One of the biggest studies on green tea for heart health , involving over 40, adults in Japan. For 11 years researchers watched to see if drinking tea benefited heart health. Looking at all of the research, in what scientists call a meta-analysis, it was concluded that drinking 1 to 3 cups of green tea per day was the best at reducing the risk of cardiovascular disease.

Interestingly, in the studies, green tea leaves with higher amounts of flavonols healthy compounds in the leaves had greater heart-healthy benefits.

We heart green tea leaves here at Millennia Tea. We organically grow our tea plants, carefully handpick the leaves, and wash them before quickly flash freezing them to ensure your freezer contains leaves with the most EGCG and flavonols possible.

Our Millennia Tea fresh tea leaves contain 15x more antioxidants than found in a cup of steeped dried green tea. With so many heart-healthy benefits, providing you with the most nutrient-rich, pesticide-free green tea leaves is our passion.

Effect of green tea consumption on blood lipids: a systemic review and meta-analysis of randomized controlled trials. Nutrition Journal Sep;19 Effects and mechanisms of tea and its bioactive compounds for the prevention and treatment of cardiovascular diseases: an updated review.

Antioxidants ; 8 6 Green tea Camellia sinensis catechines and vascular function.

Research suggests green tea is a useful beverage for helping to reduce the risk of heart disease and associated conditions, such as stroke. One way it may help is in its beneficial effects on cholesterol management. However, there is limited evidence to suggest these products are effective.

If you are hoping to use green tea for medicinal purposes, refer to your GP to ensure you may do so without risk to your health. If you are sensitive to caffeine, it is advisable to limit the total number of caffeinated drinks you drink in a day.

Too much caffeine may disrupt sleep and, in some people, increases anxiety ; if this is relevant to you, look to reduce your intake and aim to have your last caffeinated drink at about 12 noon. Looking for more information on how much caffeine is in tea? Our in-depth guide compares different types of tea and discusses which factors affect the caffeine content.

All our health benefits guides What are anthocyanins and why are purple foods so healthy? More health and nutrition tips. Jo Lewin is a registered nutritionist RNutr with the Association for Nutrition with a specialism in public health.

All health content on bbcgoodfood. com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional.

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Xiang Gao, director of the Nutritional Epidemiology Lab at Pennsylvania State University. Though experts say tea is a safe, natural beverage that is a better choice than processed, sweetened beverages, there can be negative side effects if a person consumes too much.

For example, drinking too much tea could lead to an iron deficiency because tea is rich in tannins, which can bind to iron and keep it from being absorbed in the digestive tract.

Tea drinkers also face the same caffeine-related dangers that coffee drinkers face; too much can cause anxiety, restlessness or trouble sleeping.

Still, tea makes for a healthier beverage choice than juice or soda, provided it's in its natural form with no added ingredients. It is possible to go to a coffee shop and get plain unsweetened coffee, plain unsweetened tea — or plain green tea for that matter — but you have to really be careful what you're consuming.

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