Tea has been cultivated for centuries, beginning in India and China. Today, tea is the most widely-consumed beverage in the world, second only to water. Hundreds of millions of people drink tea, and studies suggest that green tea (Camellia sinesis) in particular has many health benefits.
There are 3 main varieties of tea; green, black, and oolong. The difference is in how the teas are processed. Green tea is made from unfermented leaves and reportedly contains the highest concentration of powerful antioxidants called polyphenols, and nutrients that have powerful effects on the body.
In traditional Chinese and Indian medicine, practitioners used green tea as a stimulant, a diuretic (to help rid the body of excess fluid), an astringent (to control bleeding and help heal wounds), and to improve heart health. Other traditional uses of green tea include treating gas, regulating body temperature and blood sugar, promoting digestion, and improving mental processes.
Green tea is the healthiest beverage on earth. Of course, no one food will protect you from disease. Your health is wrapped up in your lifestyle and your genes, so even if you drink green tea all day long, you also need to take care of yourself in other ways, like not smoking, being active, and eating a healthy diet.
Here are some health benefits of green tea that have been confirmed in human research studies.
1. Green Tea Contains Bioactive Compounds That Improve Health
Green tea is more than just green liquid. Many of the bioactive compounds in the tea leaves do make it into the final drink, which contains large amounts of important nutrients.
It is loaded with polyphenols like flavonoids and catechins, which function as powerful antioxidants.
These substances can reduce the formation of free radicals in the body, protecting cells and molecules from damage. These free radicals are known to play a role in aging and all sorts of diseases.
One of the more powerful compounds in green tea is the antioxidant Epigallocatechin Gallate (EGCG), which has been studied to treat various diseases and may be one of the main reasons green tea has such powerful medicinal properties.
Try to choose a higher quality brand of green tea, because some of the lower quality brands can contain excessive levels of fluoride.
That being said, even if you choose a lower quality brand, the benefits still far outweigh any risk.
2. Compounds in Green Tea Can Improve Brain Function and Make You Smarter
Green tea does more than just keep you awake, it can also make you smarter.
The key active ingredient is caffeine, which is a known stimulant. It doesn’t contain as much as coffee, but enough to produce a response without causing the “jittery” effects associated with too much caffeine.
What caffeine does in the brain is to block an inhibitory neurotransmitter called Adenosine. This way, it actually increases the firing of neurons and the concentration of neurotransmitters like dopamine and norepinephrine.
Caffeine has been intensively studied before and consistently leads to improvements in various aspects of brain function, including improved mood, vigilance, reaction time and memory.
However… green tea contains more than just caffeine. It also has the amino acid L-theanine, which is able to cross the blood-brain barrier. L-theanine increases the activity of the inhibitory neurotransmitter GABA, which has anti-anxiety effects. It also increases dopamine and the production of alpha waves in the brain.
Studies show that caffeine and L-theanine can have synergistic effects. The combination of the two is particularly potent at improving brain function.
Because of the L-theanine and the smaller dose of caffeine, green tea can give you a much milder and different kind of “buzz” than coffee.
Many people report having more stable energy and being much more productive when they drink green tea, compared to coffee.
3. Green Tea Increases Fat Burning and Improves Physical Performance
If you look at the ingredients list for any fat burning supplement, chances are that green tea will be on there.
This is because green tea has been shown to increase fat burning and boost the metabolic rate, in human controlled trials, although not all studies agree to this.
Caffeine itself has also been shown to improve physical performance by mobilizing fatty acids from the fat tissues and making them available for use as energy.
4. Antioxidants in Green Tea May Lower Your Risk of Various Types of Cancer
Cancer is caused by uncontrolled growth of cells. It is one of the world’s leading causes of death.
It is well known that oxidative damage contributes to the development of cancer and that antioxidants can have a protective effect.
Green tea is an excellent source of powerful antioxidants, so it makes perfect sense that it could reduce your risk of cancer, which it appears to do:
Breast cancer: A meta-analysis of observational studies found that women who drank the most green tea had a 22% lower risk of developing breast cancer, the most common cancer in women.
Prostate cancer: One study found that men drinking green tea had a 48% lower risk of developing prostate cancer, which is the most common cancer in men.
Colorectal cancer: A study of 69,710 Chinese women found that green tea drinkers had a 57% lower risk of colorectal cancer.
Multiple other observational studies show that green tea drinkers are significantly less likely to get various types of cancer.
It is important to keep in mind that it may be a bad idea to put milk in your tea, because it can reduce the antioxidant value.
5. Green Tea May Protect Your Brain in Old Age, Lowering Your Risk of Alzheimer’s and Parkinson’s
Not only can green tea improve brain function in the short term, it may also protect your brain in old age.
Alzheimer’s disease is the most common neurodegenerative disease in humans and a leading cause of dementia.
Parkinson’s disease is the second most common neurodegenerative disease and involves the death of dopamine producing neurons in the brain.
Multiple studies show that the catechin compounds in green tea can have various protective effects on neurons in test tubes and animal models, potentially lowering the risk of Alzheimer and Parkinson.
6. Green Tea Can Kill Bacteria, Which Improves Dental Health and Lowers Your Risk of Infection
The catechins in green tea have other biological effects as well.
Some studies show that they can kill bacteria and inhibit viruses like the influenza virus, potentially lowering your risk of infections.
Streptococcus mutans is the primary harmful bacteria in the mouth. It causes plaque formation and is a leading contributor to cavities and tooth decay.
Studies show that the catechins in green tea can inhibit the growth of streptococcus mutans. Green tea consumption is associated with improved dental health and a lower risk of caries.
Another awesome benefit of green tea… multiple studies show that it can reduce bad breath.
7. Green Tea May Lower Your Risk of Type II Diabetes
Type II diabetes is a disease that has reached epidemic proportions in the past few decades and now afflicts about 300 million people worldwide.
This disease involves having elevated blood sugar levels in the context of insulin resistance or an inability to produce insulin.
Studies show that green tea can improve insulin sensitivity and reduce blood sugar levels.
One study in Japanese individuals found that those who drank the most green tea had a 42% lower risk of developing type II diabetes.
According to a review of 7 studies with a total of 286,701 individuals, green tea drinkers had an 18% lower risk of becoming diabetic.
8. Green Tea May Reduce Your Risk of Cardiovascular Disease
Cardiovascular diseases, including heart disease and stroke, are the biggest causes of death in the world.
Studies show that green tea can improve some of the main risk factors for these diseases.
This includes total cholesterol, LDL cholesterol and triglycerides.
Green tea also dramatically increases the antioxidant capability of the blood, which protects the LDL cholesterol particles from oxidation, which is one part of the pathway towards heart disease.
Given the beneficial effects on risk factors, it is not surprising to see that green tea drinkers have up to a 31% lower risk of cardiovascular disease.
9. Green Tea Can Help You Lose Weight and Lower Your Risk of Becoming Obese
Given that green tea can boost the metabolic rate in the short term, it makes sense that it could help you lose weight.
Several studies show that green tea leads to decreases in body fat, especially in the abdominal area.
One of these studies was a randomized controlled trial in 240 men and women that went on for 12 weeks. In this study, the green tea group had significant decreases in body fat percentage, body weight, waist circumference and abdominal fat.
However, some studies don’t show statistically significant increases in weight loss with green tea, so this needs to be taken with a pinch of salt.
10. Green Tea May Decrease Your Risk of Dying and Help You Live Longer
Of course, we all have to die eventually. That is inevitable. However, given that green tea drinkers are at a lower risk of cardiovascular disease and cancer, it makes sense that it could help you live longer.
In a study of 40,530 Japanese adults, those who drank the most green tea (5 or more cups per day) were significantly less likely to die during an 11 year period:
Death of all causes: 23% lower in women, 12% lower in men.
Death from heart disease: 31% lower in women, 22% lower in men.
Death from stroke: 42% lower in women, 35% lower in men.
Another study in 14,001 elderly Japanese individuals aged 65-84 years found that those who drank the most green tea were 76% less likely to die during the 6 year study period.
11. Green Tea is Good for Relaxing
Sipping tea helps you slow down and relax, Reardon says. A natural chemical called theanine found in green tea can provide a calming effect.
But perhaps the biggest benefit, which you get right away, is just taking a tea break. Here’s how to make your next cup:
Don't add green tea to boiling water. It's bad for catechins, those healthy chemicals, in the tea. Better: 160-170 degree water.
Add lemon. Vitamin C makes the catechins easier to absorb. Dairy, on the other hand, makes it harder to absorb them.
Nutrient levels in green tea can vary. Pricier teas usually have more, and canned green-tea drinks generally have less.
Summarily, green tea improves mental alertness and thinking. It is also taken for depression, non-alcoholicfatty liver disease (NAFLD), inflammatory bowel disease (ulcerative colitis or Crohn's disease), weight loss and to treat stomach disorders, vomiting, diarrhea, headaches, and bone loss (osteoporosis).
Some people drink green tea to prevent various cancers, including breast cancer, prostate cancer, colon cancer, gastric cancer, lung cancer, liver cancer, solid tumor cancers, leukemia, and skin cancer related to exposure to sunlight. Some women use green tea to fight human papilloma virus (HPV), which can cause genital warts, the growth of abnormal cells in the cervix (cervical dysplasia), and cervical cancer.
Green tea is also taken for Parkinson's disease, diseases of the heart and blood vessels, diabetes, low blood pressure, chronic fatigue syndrome (CFS), dental cavities (caries), kidney stones, and skin damage.
Instead of drinking green tea, some people apply green tea bags to their skin to soothe sunburn and prevent skin cancer due to sun exposure. Green tea bags are also used to decrease puffiness under the eyes, as a compress for tired eyes or headache, and to stop gums from bleeding after a tooth is pulled. A green tea footbath is used for athlete's foot.
Some people gargle with green tea to prevent colds and flu. Green tea extract is also used in mouthwash to reduce pain after tooth removal. Green tea in candy is used for gum disease.
Green tea is used in an ointment for genital warts.
These are some of the many benefits but the reality is one cup of tea a day will not give you all the abundant gains. The jury is out on how many cups are necessary; some say as little as two cups a day while others five cups — and more still say you can drink up to ten cups a day. If you are thinking of going down this route, you may want to consider taking a green tea supplement instead (it would keep you out of the bathroom).
Another thing to point out is that there is caffeine in green tea — so if you are sensitive to caffeine then one cup should be your limit. Green tea also contains tannins (which can decrease the absorption of iron and folic acid), so if you are pregnant or trying to conceive then green tea may not be ideal for you. You can try mixing green tea with other healthy ingredients such as ginger.
How Does It Work?
Green tea is made from the Camellia sinensis plant. The dried leaves and leaf buds of Camellia sinensis are used to produce various types of teas. Green tea is prepared by steaming and pan-frying these leaves and then drying them. Other teas such as black tea and oolong tea involve processes in which the leaves are fermented (black tea) or partially fermented (oolong tea).
Several varieties of green tea exist, which differ substantially because of the variety of C. sinensis used, growing conditions, horticultural methods, production processing, and time of harvest.
The useful parts of green tea are the leaf bud, leaf, and stem. Green tea is not fermented and is produced by steaming fresh leaves at high temperatures. During this process, it is able to maintain important molecules called polyphenols, which seem to be responsible for many of the benefits of green tea.
Polyphenols might be able to prevent inflammation and swelling, protect cartilage between the bones, and lessen joint degeneration. They also seem to be able to fight human papilloma virus (HPV) infections and reduce the growth of abnormal cells in the cervix (cervical dysplasia). Research cannot yet explain how this works.
Green tea contains 2% to 4% caffeine, which affects thinking and alertness, increases urine output, and may improve the function of brain messengers important in Parkinson's disease. Caffeine is thought to stimulate the nervous system, heart, and muscles by increasing the release of certain chemicals in the brain called "neurotransmitters."
Antioxidants and other substances in green tea help protect the heart and blood vessels.
Green Tea Side Effects & Safety
Green tea is LIKELY SAFE for most adults when consumed as a drink in moderate amounts or when green tea extract is applied to the skin as a specific ointment (Veregen, Bradley Pharmaceuticals), short-term. Green tea extract is POSSIBLY SAFE for most people when taken by mouth for up to 2 years, when applied to the skin as other ointments short-term, or when used as a mouthwash short-term. In some people, green tea can cause stomach upset and constipation.
Green tea is POSSIBLY UNSAFE when taken by mouth long-term or in high-doses. It can cause side effects because of the caffeine. These side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhoea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion. Green tea seems to reduce the absorption of iron from food. Drinking very high doses of green tea is LIKELY UNSAFE and can actually be fatal. The fatal dose of caffeine in green tea is estimated to be 10-14 grams (150-200 mg per kilogram). Serious toxicity can occur at lower doses.
Special Precautions & Warnings:
Children: Green tea is POSSIBLY SAFE for children when used in amounts commonly found in foods and beverages or when used for gargling three times daily for up to 90 days.
Pregnancy and breast-feeding: If you are pregnant or breast-feeding, green tea in small amounts - about 2 cups per day - is POSSIBLY SAFE. This amount of green tea provides about 200 mg of caffeine. However, drinking more than 2 cups of green tea per day is POSSIBLY UNSAFE. Consuming more than 2 cups of green tea daily has been linked to an increased risk of miscarriage and other negative effects due to the caffeine content. Also, green tea might increase the risk of birth defects associated with folic acid deficiency. In women who are nursing, caffeine passes into breast milk and can affect a nursing infant. Don't drink an excessive amount of green tea if you are pregnant or breast-feeding.
"Tired blood" (anaemia): Drinking green tea may make anaemia worse.
Anxiety disorders: The caffeine in green tea might make anxiety worse.
Bleeding disorders: Caffeine in green tea might increase the risk of bleeding. Don't drink green tea if you have a bleeding disorder.
Heart conditions: Caffeine in green tea might cause irregular heartbeat if taken excessively.
Diabetes: Caffeine in green tea if excessively taken might affect blood sugar control. If you drink green tea and have diabetes, monitor your blood sugar carefully.
Diarrhea: Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea.
Glaucoma: Drinking green tea increases pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes.
High blood pressure: The caffeine in green tea might increase blood pressure in people with high blood pressure if taken excessively. However, this does not seem to occur in people who regularly drink green tea or other products that contain caffeine.
Irritable bowel syndrome (IBS): Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.
Liver disease: Green tea extract supplements have been linked to several cases of liver damage. Green tea extracts might make liver disease worse.
Weak bones (osteoporosis): Drinking green tea can increase the amount of calcium that is flushed out in the urine. Caffeine should be limited to less than 300 mg per day (approximately 2-3 cups of green tea). It is possible to make up for some calcium loss caused by caffeine by taking calcium supplements.
GREEN TEA Interactions
Do not take this combination
Amphetamines interacts with GREEN TEA
Stimulant drugs such as amphetamines speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in green tea might also speed up the nervous system. Taking green tea along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Cocaine interacts with GREEN TEA
Stimulant drugs such as cocaine speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in green tea might also speed up the nervous system. Taking green tea along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Ephedrine interacts with GREEN TEA
Stimulant drugs speed up the nervous system. Caffeine (contained in green tea) and ephedrine are both stimulant drugs. Taking green tea along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems. Do not take caffeine-containing products and ephedrine at the same time.
To be safe, check with your health care provider before drinking or taking green tea if you also take other medications.
GREEN TEA Dosing
The following doses have been studied in scientific research:
For high cholesterol: Green tea or green tea extracts containing 150 to 2500 mg catechins, taken in single or 2 divided doses daily for up to 24 weeks, has been used.
For abnormal development of cells of the cervix (cervical dysplasia): 200 mg of green tea extract, taken by mouth daily along with a green tea ointment applied twice weekly for 8-12 weeks, has been used.
For high blood pressure: A green tea drink, made by boiling a 3 gram tea bag with 150 mL water, has been used three times daily about 2 hours after each meal for 4 weeks. Also, 379 mg of a specific product containing green tea extract (Olimp Labs, Debica, Poland), taken daily with the morning meal for 3 months, has been used.
For low blood pressure: 400 mL of green tea taken before lunch has been used.
For thick, white patches on the gums (oral leukoplakia): 3 grams of mixed green tea taken by mouth and applied to the skin for 6 months has been used.
For osteoporosis: Capsules containing 500 mg of green tea polyphenols, taken twice daily alone or while practicing tai chi for 60 minutes three times weekly for 24 weeks, has been used.
APPLIED TO THE SKIN:
For genital warts: A specific green tea extract ointment (Veregen, Bradley Pharmaceuticals; Polyphenon E ointment 15%, MediGene AG) applied three times daily to warts for up to 16 weeks, has been used. This product is FDA-approved for treating this condition.
For abnormal development of cells of the cervix (cervical dysplasia): A green tea ointment has been used alone twice weekly, or in combination with 200 mg of green tea extract taken by mouth daily for 8-12 weeks.
For thick, white patches on the gums (oral leukoplakia): 3 grams of mixed green tea taken by mouth and applied to the skin for 6 months has been used.
Nutritional Breakdown of Green Tea
Unsweetened brewed green tea is a zero calorie beverage. The caffeine contained in a cup of tea can vary according to length of infusing time and the amount of tea infused.
In general, green tea contains a relatively small amount of caffeine (approximately 20-45 milligrams per 8 oz cup), compared with black tea which contains about 50 milligrams and coffee with 95 milligrams per cup.
Green tea is considered one of the world's healthiest drinks and contains one of the highest amount of antioxidants of any tea. Researchers commonly speak highly of green tea.