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Green Tea: Health Benefits, Safety, and More

By Markita Lewis, MS, RD

Medically Reviewed by Ana Reisdorf, MS, RD

Published on February 16, 2022

Green tea is a nutrient-dense tea with many potential health benefits. Learn what these benefits are and how to get the most out of drinking green tea.

Written by
Markita Lewis, MS, RD
Registered Dietitian Nutritionist
Markita Lewis is a registered dietitian with over 5 years of experience in the field of nutrition and health. Prior to her professional career, Markita completed a combined masters and dietetic internship program at the University of Georgia. She obtained her undergraduate degree at Louisiana State University in Nutrition and Foods Sciences, concentrating in dietetics with a minor in Psychology.
Medically Reviewed by
Ana Reisdorf, MS, RD
Registered Dietitian Nutritionist
Ana Reisdorf is a registered dietitian nutritionist with 14 years of experience in the field of nutrition and dietetics. She graduated from UCLA in 2002 with a degree in psychology and women’s studies and completed her master’s degree from Central Michigan University in 2010
Green Tea: Health Benefits, Safety, and More
Photo credit: iStock.com/FreshSplash

What Is Green Tea?

Green tea comes from the leaves of the Camellia sinensis plant. This is the same plant that produces white, yellow, black, purple, oolong, and Pu-erh teas, which are considered “true” teas.

The differences between these types of teas are in how they are processed. Varieties of tea undergo different steps that may or may not include withering, drying, fermenting, rolling or cutting, and heating.

Green tea is quickly processed compared to darker teas. After the leaves are plucked, they are quickly dried or steamed, shaped, and sent out for sale.

Tea is traditionally grown in areas like China, India, and Sri Lanka due to the climate, acidic soil, and rainfall needed for tea plants to grow optimally. However, these days, dozens of countries are producing varieties of tea.

Beneficial Compounds of Green Tea

Green tea has been used in Traditional Chinese Medicine and other Asian traditional medicine systems for thousands of years. (1)

Tea was used for its anti-inflammatory properties against a wide variety of conditions.

Today, we know that green tea is packed with beneficial compounds for health that make this beverage a superfood. (2)

Here are some of the major beneficial components of green tea.

Polyphenols

Green tea contains several types of polyphenols, compounds with strong antioxidant activity.

This means that they are able to reduce the activity of reactive oxygen species (ROS), molecules that cause oxidative stress and inflammation and increase the risk of chronic diseases. You may also know ROS by the name of “free radicals.”

The majority of green tea’s polyphenols come from the group called “catechins.” Catechin antioxidants were named after the plant they were first discovered in, the Acacia catechu tree. (3)

The major catechins in green tea include epicatechin, epigallocatechin, epicatechin-3-gallate, and epigallocatechin gallate (EGCG).

Compared to black or oolong tea, green tea has greater amounts of catechins.

Amino Acids

Green tea contains several amino acids, but most importantly, L-theanine.

L-theanine is an amino acid primarily found in tea and can affect the brain by increasing brain chemicals like GABA, dopamine, serotonin, and alpha waves (a type of brain wave associated with relaxation). (4)

Vitamins and Minerals

Green tea is filled with nutrients (including vitamins, minerals, and trace elements), such as magnesium, iron, copper, phosphorus, potassium, calcium, selenium, zinc, and chromium.

Approximately 5% of the dry weight of green tea is made up of minerals and trace elements.

Caffeine

Green tea tends to have a lower caffeine concentration per cup than black teas or coffee, but can still provide caffeine-related benefits.

Health Benefits of Green Tea

People can experience the benefits of green tea both as a beverage and as a concentrated extract.

Here’s what the research says about green tea, its major components, and how it can benefit your health.

Can Support Mental Focus and Calm

Green tea extract, EGCG, and L-theanine have been studied for their abilities in reducing anxiety and psychological stress.

A 2017 review examined the effects of green tea on cognition, mood, and brain function. Studies examining green tea, green tea extract, EGCG, L-theanine, and caffeine were included in this review. (5)

Researchers found that these compounds enhanced memory and attention, improved executive function, information processing speed, reduced tension and anxiety, and reduced mental fatigue either alone or in combination with other components of green tea (e.g., L-theanine and caffeine).

Daily doses of L-theanine (200 mg to 600 mg) or intake of between 100 mL to 500 mL (approximately 0.5 to 2 cups) of green tea supported these benefits, though more research needs to be done.

Summary 

The compounds found in green tea are able to support cognition, mood, and brain function in the short and long term with daily intake.

Related: The Best Supplements for Brain Health

May Reduce Heart Disease Risk

The catechins in green tea can reduce your risk for cardiovascular disease.

Atherosclerosis is the process in which plaque formed by cholesterol and other substances hardens and narrows your arteries. Atherosclerosis can lead to cardiovascular conditions like heart attacks, strokes, and coronary heart disease. (6)

A 2020 study on tea consumption and cardiovascular risk found that Chinese adults who regularly drank green tea had a reduced risk of coronary heart disease and stroke. (7)

In the study, regular tea drinkers were observed to live without cardiovascular disease for longer and had an overall longer life expectancy.

Research suggests that there are several mechanisms thought to support the use of green tea for heart health.

In animal and human studies, polyphenols and catechins in tea can help reduce inflammation, improve the relaxation of the aorta, reduce blood pressure, reduce blood clot formation, and inhibit cholesterol absorption in the body. (8)

Summary 

Regular consumption of green tea may reduce the risk of coronary heart disease and stroke due to the activity of its polyphenol antioxidants.

Related: Foods That Can Lower High Cholesterol

May Support Healthy Gut Microbiota

A growing body of research supports green tea for supporting a healthy gut.

As you may recall, catechins are a type of polyphenol antioxidant. Polyphenol compounds like catechins can inhibit the activity of harmful bacteria and assist with balancing the gut microbiota.

Polyphenols are considered prebiotics and feed the beneficial bacteria in your gut. When beneficial bacteria are fed, they can reduce the concentration of inflammatory bacteria in the gut and reduce overall gut inflammation. (9)

These bacteria also produce short-chain fatty acids like butyrate and propionate, which are fats that can be used by cells in the gut or in the body to reduce inflammation, support regular metabolism, and reduce disease risk. (10)

A 2021 review found that green tea could help reduce dysbiosis (imbalances in gut bacteria) induced by cancer and high-fat diets, and may reduce symptoms of Parkinson’s disease previously made worse by dysbiosis. (11)

Summary

The polyphenols in green tea can help restore balance to gut bacteria, reduce inflammation, and promote the production of short-chain fatty acids in the gut.

People with cancer, high-fat diets, or Parkinson’s disease may experience gut benefits from drinking green tea.

Related: 10 Evidence-Based Ways to Improve Your Gut Health

May Increase Metabolism and Weight Loss

Green tea is not only a low-calorie beverage, but its active compounds may also increase metabolism and decrease fat gain.

While all green tea catechins appear to contribute to metabolic benefits, EGCG is the main catechin that supports metabolism. Caffeine present in green tea can also support fat burning, weight loss, and appetite reduction. (12, 13)

A 2019 review found that green tea can increase thermogenesis (fat burning), reduce the formation of fat cells, and limit the absorption of fats. (14)

Animal studies suggest that EGCG from green tea can stimulate leptin (a satiety hormone) and reduce food intake.

Together, EGCG and caffeine have a synergistic response in promoting fat burning and metabolic rate. This means that when EGCG and caffeine are added together, they have an even greater effect than either ingredient alone. (15)

Summary 

EGCG and caffeine from green tea can help with weight loss, appetite control, limiting the absorption of fats, and metabolism of fat tissue.

Related: Evidence-Based Ways to Boost Metabolism

May Protect Against Oxidative Stress Caused by Exercise

Many researchers have examined whether green tea or green tea extract is able to improve athletic performance.

Currently, research does not consistently support using green tea for increasing endurance or exercise performance. (16)

The major benefit of green tea for athletes and people who exercise may be to protect against oxidative stress (an imbalance between ROS and antioxidants) and muscle damage caused by exercise.

A 2014 study had young men perform resistance exercise and drink 200 mL of a green tea beverage three times per day for a week to see how green tea protected against oxidative stress. (17)

Compared to drinking plain water (200mL 3x/day), the men who drank green tea had reduced oxidative stress caused by exercise and greater levels of antioxidants in their blood.

A 2018 study found that taking green tea extract (500 mg/day) for 15 days reduced muscle damage and oxidative stress, and preserved the brain-muscle connection compared to a placebo. (18)

Summary 

Green tea and green tea extract may protect against oxidative stress and muscle damage caused by exercise.

Reduced muscle damage and lower oxidative stress may have a positive impact on exercise performance and recovery.

Related: Pre-Workout Meal: What to Eat Before a Workout

May Reduce Cancer Risk

Green tea may be a good support to cancer prevention and may enhance the activity of anti-cancer drugs.

EGCG primarily helps reduce cancer progression by increasing the activation of antioxidants and inhibiting inflammation.

Inhibition of certain inflammatory cell-signaling molecules can decrease the initiation, progression, and spread of cancer.

Not all cancer types show the same degree of responsiveness to EGCG, but a 2020 review shows that EGCG can positively impact overall inflammation and prevent the spread of cancer in cell studies. (19)

Clinical trials so far find that EGCG plays a role in cancer prevention in cancers of the prostate, urinary bladder, head and neck, breast, ovaries, and lungs. These benefits are promising but are not consistently seen in clinical studies. (20)

In addition, some anticancer medications have an increased effect when combined with EGCG and other tea polyphenols. While more research needs to be done, there is potential for EGCG to be used in cancer treatment and prevention. (19)

Summary 

EGCG and other green tea polyphenols may reduce inflammation and the spread of cancer cells, and can increase the activity of certain anticancer medications.

Can Support Longevity

While green tea alone may not cause you to live longer, it can be a contributing factor to a longer lifespan.

One multi-year study with over 100,000 adult participants examined the risks that contribute to cardiovascular disease and all-cause mortality. (7)

In the study, adults who drank green tea three times or more weekly were likely to have a longer life expectancy (about 15 months longer) than those who drank tea fewer than three times per week.

Another multi-year study in China found that older adults aged 80 or older who drank tea daily had a 10% reduction in mortality compared to infrequent tea drinkers. (21)

Summary

Drinking tea at least three times per week or more frequently can support a longer lifespan.

Recommended Dosages

Across studies for different conditions, drinking 3 to 5 cups of green tea per day is sufficient to experience the benefits of green tea.

Currently, there is no optimal dosing of EGCG.

A scientific panel noted that average intake of EGCG from green tea beverages ranged from 90 to 300 mg/day, but there is little information on what an optimal dose is. (22)

Side Effects and Safety

Although tea is the second most consumed beverage in the world, there are still some risks to drinking green tea.

The risks are generally dose-dependent, so it is important to pay attention to your intake of green tea and green tea extract.

The most commonly reported side effects from drinking green tea or taking capsules of green tea extract include abdominal pain, abdominal discomfort, diarrhea, indigestion, and elevated liver enzymes (a sign of liver toxicity). (23)

In some studies, less common symptoms of green tea intake included vomiting, constipation, gas, and belching.

While some side effects from tea are attributed to the EGCG concentration of green tea products, some side effects are from the caffeine present in green tea. These side effects include anxiety, insomnia, and nervousness.

The FDA warns against excessive amounts of caffeine and recommends limiting caffeine intake to no more than 400 mg daily (approximately 14 cups of green tea). (24)

Depending on the region, daily intake of tea typically ranges between 3 to 10 cups. To determine the right amount of tea for you, monitor your reactions to tea and when you feel any adverse effects.

Studies support that green tea is better tolerated in beverage form, and green tea extract capsules should be taken with a meal or after eating to reduce symptoms. (23)

Intake of 800 mg of EGCG or more as a supplement is associated with increased liver enzymes. (22)

Medication Interactions

Green tea and EGCG can interact with several types of medications. Some medications are made more bioavailable (more absorbable by the body), while others are decreased in bioavailability and activity. (25, 26)

EGCG and other tea polyphenols can increase the activity of certain anticancer medications, blood pressure medications (calcium channel blockers), aspirin, warfarin, antibiotics, and estrogen modulators (e.g., hormonal treatments for breast cancer).

EGCG and green tea extract can reduce the bioavailability or interaction with certain antipsychotic medications, anticancer medications, mood medications, sedatives, and beta-blockers

Nutrient Interactions

Excessive green tea intake may impact the absorption of certain minerals. Catechins in green tea are able to bind to zinc and iron and reduce blood concentrations of these minerals. (27)

People with a history of iron deficiency should take caution with the timing of iron-containing foods or supplements and drink tea at least an hour after meals.

Conversely, excessive green tea can also increase manganese concentration in the blood.

Green Tea and Pregnancy

Though green tea is low in caffeine, pregnant people should avoid intake of caffeine as much as possible.

A 2021 review of meta-analyses and observational studies found that any caffeine intake during pregnancy increased the risk for miscarriage, stillbirth, low birth weight, and childhood acute leukemia. (28)

Speak with your doctor before starting a green tea extract, EGCG supplement, or if you’re drinking large quantities of tea daily to be sure that you can do so safely.

If you experience any significant symptoms, including symptoms that indicate liver injury (e.g., jaundice, dark urine, or abdominal pain), stop immediately and consult your physician.

Tips on Using Green Tea

Green tea is widely available, and it can be overwhelming to choose the right kind for you.

It’s available as extracts, powders, individual tea bags, loose leaves, and even pre-brewed bottles for your convenience.

The best green tea to get would have to be loose leaf tea. It is less processed than other teas, meaning its antioxidant content is likely higher than other forms.

If you’re unable to get loose leaf teas or prefer the convenience of prepackaged tea, then be sure to look for high-quality tea brands.

Qualities in a good green tea brand include using hand-picked tea leaves, transparency about where the tea was grown, organic tea leaves, unbleached tea bags, third-party testing, and the use of whole leaves.

The flavor and antioxidant content tend to be better in certain brands, making the additional cost worth the investment.

Higher quality teas are also less likely to be tampered with, contaminated with dangerous chemicals, or contain unnecessary ingredients.

Third-party testing entities like ConsumerLab test the EGCG content of popular green tea supplements and tea leaves.

Some companies will also provide information about the antioxidant content of their products.

Types of Green Tea

Not all green tea is made the same. Some common varieties of green tea include matcha, sencha, and gunpowder green tea, though there are many other Chinese and Japanese varieties of green tea.

You can also commonly find green teas infused with mint, jasmine, and other flavors.

Matcha tends to have a higher concentration of EGCG, and gunpowder green tea has more caffeine due to its processing, but all green tea varieties have benefits.

When it comes down to it, sometimes the biggest deciding factor in choosing a tea is the flavor. Jasmine and mint-flavored green teas tend to be easier on the palate, while matcha green tea has a distinct green, somewhat bitter flavor.

Storage

To get the longest shelf life and best antioxidant potential out of your tea, you should store it in a cool, dark area that isn’t exposed to much humidity.

If you are purchasing loose leaf teas, store them in air-tight containers to extend their life.

Loose green teas may have up to a two-year shelf life when stored in an air-tight container, but may only stay fresh for 4–6 months if stored in a paper bag.

Tea can expire and lose its flavor and antioxidant potential over time, so plan your tea hoarding accordingly.

Preparation

Most teas will have instructions on how to prepare them properly. Depending on the style, a tea may require different temperature settings, steeping times, or request that you use two packets of tea instead of one.

For loose leaf tea, a serving of tea is about 2 grams of loose tea for every 8 ounces of hot water. If you’re measuring your tea, about 1–2 teaspoons of tea are enough for a richly-flavored cup.

When you’re steeping your tea, remember to remove your tea bag (or tea infuser) after the recommended time. Leaving your tea steeping for too long increases the concentration of tannins, which increases the bitter taste of tea.

To get the most antioxidant power out of your tea, avoid adding milk or too much sweetener to your cup.

Green tea can be used for other culinary purposes if you’re feeling adventurous. Green tea and matcha powder are commonly used in baked goods, lattes, smoothies, oatmeal, soups, salads, and other recipes.

According to some food science research, the antioxidant activity of green tea is still active when added to other foods. However, there is a lack of research concerning if green tea’s benefits are as effective when added to other foods. (29)

To err on the side of caution, it may be best to either drink your tea plain or choose a green tea supplement.

Frequently Asked Questions

What are the benefits of drinking green tea?

Drinking green tea or taking green tea extract can support heart health, support your brain health, help improve your mood, balance gut health, reduce cancer risk, increase metabolism and weight loss, control appetite, decrease post-exercise muscle stress, and increase longevity.

What makes green tea different from other tea?

Because it does not have the fermentation process, it is higher in catechin antioxidants like EGCG compared to darker teas.

When is the best time of day to drink green tea?

Green tea can be enjoyed at any time of the day, though people sensitive to caffeine may want to avoid drinking green too late at night.

What are the risks from drinking green tea?

Green tea and green tea extract can cause abdominal pain, abdominal discomfort, diarrhea, indigestion, elevated liver enzymes, vomiting, constipation, gas, and belching.

Can pregnant people drink tea?

Current guidelines state that pregnant people can have up to 200 mg of caffeine daily, but recent research suggests that any tea or caffeine intake may increase the risk of adverse events during pregnancy.

The Bottom Line

Green tea is one of the oldest medicinal herbs in history, and modern research confirms its benefits for the body.

Its antioxidant and nutrient capacity make it a kind of “superfood” with many health benefits, including increased lifespan.

While there is still more to learn about green tea and its individual components, the current research is promising.

As with most things, moderation is key. Green tea is one of the most commonly consumed beverages around the world, but excess green tea or extracts from tea can result in negative effects on the gastrointestinal system or liver.

There are also additional risks for pregnant people, people who take certain medications, and those who are sensitive to caffeine.

Before increasing your tea intake or starting a green tea supplement, please speak with your healthcare provider to confirm that it is safe for your personal use.

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At WellnessVerge, we only use primary references for our articles, including peer reviewed medical journals or well-respected academic institutions.

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