Green tea: Health benefits, side effects, and research

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People have hailed the health benefits of green tea for centuries. Studies suggest that consuming green tea may positively affect skin health, help with weight loss, and reduce the risk of cardiovascular disease, among other benefits.

Green tea comes from unoxidized leaves of the Camellia sinensis bush. It is one of the least processed types of tea, containing the most antioxidants and beneficial polyphenols.

Some research suggests green tea may positively affect weight loss, liver disorders, type 2 diabetes, Alzheimer&#;s disease, and more. However, more evidence is necessary for researchers to definitively prove these health benefits.

This article lists some potential health benefits and types of green tea, its nutrition content, and the potential side effects.

Cancer prevention

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In countries with high green tea consumption, some cancer rates tend to be lower. However, human studies have not shown consistent evidence that drinking green tea reduces the overall risk of cancer.

A database review of epidemiological and experimental studies in humans produced inconsistent results and limited evidence of green tea&#;s benefits for lowering cancer risk.

The researchers assessed 142 completed studies, including 1.1 million participants.

The topical application of green tea polyphenol extracts may have a role in protecting the skin from UVB radiation. A review of in vitro, in vivo, and human studies demonstrated the potential benefits of tea polyphenols in the chemoprevention of UVB-induced skin cancer.

A review suggests green tea catechins have some positive impacts on the following types of cancer:

• breast
• colorectal
• esophageal
• lung
• prostate
• liver

Overall, more research on humans is necessary to prove the benefit of green tea on the overall risk of cancer.

Weight loss

A review suggests green tea and the catechin epigallocatechin gallate (EGCG) it contains may help people with obesity to reduce their body weight.

A further meta-analysis of several different tea polyphenols-induced weight loss mechanisms suggested that catechins and caffeine synergistically produced weight loss effects, as opposed to them being the result of caffeine alone.

However, the impact of drinking green tea on weight loss is unlikely to be of clinical importance. Most studies that have shown small changes in metabolism used green tea extracts with extremely high concentrations of catechins.

Learn more about green tea and weight loss.

Inflammatory skin conditions

Green tea has anti-inflammatory properties. Research highlights the anti-inflammatory effects of green tea.

A analysis of tea extract use in cosmetics determined that solutions including tea extracts promoted anti-inflammatory responses when applied topically. The authors also found that skin microcirculation improved in the affected areas.

Lower cholesterol

A review concluded that green tea consumption can significantly lower total cholesterol and low-density lipoprotein cholesterol in people with moderate weight, overweight, or obesity.

However, the authors highlight the need for more research, particularly longer studies with more diverse populations.

Stroke risk

According to the American Heart Association (AHA), drinking large amounts of green tea without sugar may reduce the risk of stroke.

A review and meta-analysis supports this, associating moderate green tea consumption with a lower risk of stroke after evaluating five studies with 645,393 participants and 11,421 incidents of stroke.

Type 2 diabetes

Studies concerning the relationship between green tea and diabetes have been inconsistent.

Some have suggested a lower risk of type 2 diabetes in people who drink green tea than in those who consume no tea.

One study of people with and without diabetes in China associates daily green tea consumption with a lower risk of type 2 diabetes. It also associated daily green tea consumption with a lower risk of all-cause mortality in people with diabetes.

A further review of dietary polyphenol studies also associated green tea, as part of the Mediterranean diet, with a reduced risk of type 2 diabetes.

However, further research is necessary to fully determine the relationship between diabetes risk and green tea.

Working memory

A study of 264 adults in China associates regular green tea consumption with better cognitive function, particularly executive function and memory.

Several smaller studies support this. A study suggests acute green tea extract supplementation improved working memory capacity in 10 women ages 50&#;63, although there was no significant effect for younger adults.

Similarly, another study examined the effect of green tea catechins on adults ages 50&#;69 in Japan. The authors suggest daily green tea supplementation may benefit working memory.

According to a review, certain amino acids in green tea have an anti-stress element that helps to slow brain aging.

Alzheimer&#;s disease

According to a systematic review, current research generally supports the hypothesis that green tea may reduce the risk of Alzheimer&#;s disease and dementia.

This may be due to the neuroprotective effects, including anti-inflammation and anti-oxidative stress, of certain catechins in green tea.

However, further research is necessary to strengthen this evidence.

Other benefits

Green tea may also benefit other conditions. For example, the United States Food and Drug Administration (FDA) has approved a green tea extract ointment as a prescription treatment option for genital warts.

A review suggests green tea phytochemicals may reduce skin aging.

Other research suggests green tea may have the following effects:

• prevent tooth decay and cavities
• improve osteoarthritis pain
• antiallergic effect
• promote wound healing

However, further human clinical trials are necessary to firm up these theories.

Nutritional breakdown

Unsweetened brewed green tea contains fewer than 3 calories per cup.

Green tea contains a relatively small amount of caffeine, approximately 29 milligrams (mg) per 8-ounce cup, compared with black tea, which has around 47 mg per cup, and coffee, which has about 95 mg per cup.

The caffeine in a cup of tea can vary according to the duration of infusing time and the amount of tea infused.

Green tea contains one of the highest amounts of antioxidants of any tea. Green tea is about 30% polyphenols by weight, of which approximately 80% is EGCG.

Types

Green tea is available in many types and forms, including:

• bottled and sweetened with sugar or an artificial sweetener
• single tea bags
• loose leaf
• instant powder
• green tea supplements, in capsule form or as liquid extracts

Side effects and risks

In adults, there are few known side effects associated with drinking green tea. However, the following risks and complications are important to note:

• Caffeine sensitivity: People with severe caffeine sensitivities could experience insomnia, anxiety, irritability, nausea, or an upset stomach after drinking green tea.
• Liver damage: Consuming a high concentration of green tea extract may negatively impact liver health in rare cases.
• Other stimulants: If a person consumes green tea alongside stimulant drugs, it may increase their blood pressure and heart rate.

Most research suggests that the rare cases of liver injury from green tea extract consumption are idiosyncratic reactions. Reviews of these instances have yet to conclude direct causality.

The Food and Drug Administration (FDA) does not regulate green tea supplements. As a result, these supplements may contain other substances that are unsafe for health or have unproven health benefits.

Always check with a doctor before starting any herb or supplement regimen.

Frequently asked questions

Below are some common questions about green tea.

What is the best time to drink green tea?

Further research is necessary to determine the best time to drink green tea. However, since green tea contains caffeine, some people may prefer to drink it in the morning.

What happens if a person drinks green tea every day?

Research suggests it is safe for most adults to drink up to 8 cups of unsweetened green tea daily. However, people should be aware of the amount of caffeine in the brand they choose.

Very high quantities of green tea may lead to liver damage or interact with certain medications.

Does green tea reduce belly fat?

Some research suggests that regular tea consumption, including green tea, may help to reduce body weight and waist-to-hip ratios. However, several factors can influence fat loss, including total calorie intake and exercise levels.

Summary

Green tea may have several health benefits. For example, it may help with weight management, skin inflammation, and type 2 diabetes. Some research also links green tea consumption to improved cardiovascular health.

Green tea has one of the highest concentrations of antioxidants of any tea. It is naturally low in calories and contains less caffeine than black tea and coffee.

Most people can drink green tea daily with no side effects. However, some people may experience sleep disturbances due to the caffeine in green tea if they drink large amounts or consume it late in the day.

Everything you need to know about green tea extract supplements

For centuries, people have hailed the health benefits of green tea &#;and for good reason. Green tea contains potent antioxidant compounds called polyphenols that have been shown to support skin, brain, and heart health, enhance weight loss, and possibly even protect against cancer [

1

,

2

,

3

]. But are there any benefits to taking green tea extract?

In this guide, we will take a closer look at what green tea extract is, any science-backed benefits, what you should look for in a green tea supplement, and how much you should take. So, pour yourself a cup of green tea and dive in!

What is green tea extract?

Green tea extract is extracted from the leaves of the Camellia sinensis plant and is a highly concentrated form of green tea. It contains potent antioxidants&#;such as flavonoids and polyphenols like epigallocatechin gallate (EGCG)&#;that protect against cell damage and offer a variety of health benefits [

1

,

4

,

5

].

Green tea extract benefits

Studies have shown that consuming green tea and green tea extract could have several positive effects on your health. From supporting weight loss to boosting energy, skin, and heart health and even protecting against cancer, here are the science-backed benefits of taking green tea extract. 

Green tea heart benefits

Drinking green tea is associated with a reduced risk of heart disease and a lower risk of heart disease-related death, particularly in males [

1

]. Green tea extract may also provide similar benefits and support heart health by helping to reduce blood pressure and improve cholesterol. 

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These benefits are associated with green tea&#;s anti-inflammatory compounds like EGCG, which have been shown to reduce inflammation and relax blood vessels, as well as lower levels of &#;bad&#; LDL cholesterol [

6

,

7

].

The optimal dose of green tea extract for cholesterol and blood pressure benefits is unknown, but one study in obese patients with hypertension found that taking 379 mg/day of green tea extract produced favorable improvements in both blood pressure and cholesterol numbers [

8

]. 

Improved alertness, attentiveness, and mood

When you need a little pick-me-up, consider green tea extract for energy. 

Green tea naturally contains caffeine, a stimulant that has been shown to boost alertness, energy levels, and reaction time, as well as improve mood and memory [

9

]. Research also shows that EGCG may reduce oxidative damage and inflammation and might help increase attentiveness while promoting calm and relaxation [

10

]. 

Before you take green tea extract, it&#;s good to know just how much caffeine you&#;re getting. Be sure to read our FAQ section for more information about green tea extract and caffeine and tips for safe consumption. 

Healthier skin and improved acne

Studies investigating the benefits of green tea extract show topical green tea extract may be beneficial for both acne and aging skin. 

If you suffer from acne, topical application of green tea solutions or EGCG has been shown to help reduce sebum production, blackheads, and inflammation associated with acne [

2

]. 

Studies have also proven that green tea extract improves skin moisture, reduces roughness, and neutralizes free radicals, making it very effective for treating and slowing the age-related deterioration of the skin [

11

].  

For skin benefits, topical application is more effective than the ingestion of green tea or green tea extract [

2

]. Concentrations between 1-6% ECGC and 2-3% green tea solutions have produced positive results related to acne, skin moisture, and smoothness [

2

,

11

].

It may boost weight loss

If you&#;re looking to lose weight, many studies exploring green tea extract for weight loss have shown that green tea may be worth considering. 

Green tea supplements, particularly those with caffeine, are associated with modest but statistically significant reductions in BMI, body weight, and waist circumference [

2

,

12

,

13

]. 

One study in obese women found taking 857 mg/day of green tea extract with EGCG produced more significant weight loss and waist circumference reductions than a placebo [

12

]. As a bonus, the green tea group also saw a decrease in total cholesterol and LDL cholesterol levels without any notable side effects [

12

]. 

Some researchers attribute green tea&#;s weight loss benefits to lower ghrelin production (the body&#;s primary hunger hormone) and an increase in adiponectin. This hormone helps with insulin sensitivity, inflammation, and fatty acid breakdown [

12

,

14

].

Despite some potential benefits on the scale, green tea extract is not a miracle weight loss pill. Evidence shows that by itself, green tea extract does not lead to reductions in key measurements like weight or waist circumference [

13

]. Therefore, to maximize its potential weight loss benefits, you will need to combine green tea extract with a healthy diet, plenty of physical activity, and healthy sleep and stress-management habits.

Anti-cancer benefits

Researchers are also exploring the potential benefit of green tea extract for cancer. Early clinical studies have shown that the polyphenols present in green tea may play an important preventative role in the following types of cancer [

1

,

15

,

16

]:

• Endometrial cancer: Green tea has been  linked to a reduced risk of developing cancer of the lining of the uterus [

  1

  ]. 

• Breast cancer: Drinking green tea may reduce the risk of breast cancer by 15% [

  17

  ].

• Ovarian cancer: Regularly drinking green tea seems to reduce the risk of ovarian cancer [

  1

  ].

• Colorectal cancer: Some studies have shown that green tea drinkers have a 30&#;40% lower chance of developing colorectal cancer [

  18

  ].

Researchers also believe that polyphenols may help kill cancerous cells and stop them from growing. For example, laboratory studies have found that green tea extracts prevent the growth of prostate cancer cells in test tubes. Still, more research is needed to explore whether these benefits can be replicated in a clinical setting and whether green tea extract has any treatment benefit [

3

].

While these results seem promising, much of the research has involved green tea drinkers, not supplements, and many other studies have produced conflicting results. More research is needed to explore green tea's potential anti-cancer benefits, specifically using green tea extract.

What to look for in green tea extract supplements

When it comes to choosing a green tea extract supplement, it&#;s important to know that not all supplements are created equal. For example, some green tea supplements contain only dry green tea leaves, while others contain isolated forms of one or more polyphenols, like EGCG.

Here are some things to consider when choosing a green tea supplement.

• Know what you&#;re getting: Because supplements are not government-regulated, they should be evaluated for purity and quality by a reputable testing organization.

• The form of green tea and potency: You&#;ll want to know whether your supplement  contains only dry green tea leaves or isolated forms of antioxidants. Supplements made with isolated antioxidants will be more potent and potentially provide more significant benefits. 

• Whether it contains EGCG: You will find antioxidants listed as polyphenols, catechins, or EGCG on a green tea supplement label. Since EGCG is the most widely researched green tea antioxidant and is closely linked to its health benefits, you should look for a supplement that contains this polyphenol [

  2

  ]. 

• How much caffeine the supplement contains: Green tea extract supplements can contain vastly different amounts of caffeine, from zero to mega doses of 200 mg or more. Consuming too much caffeine can leave you feeling jittery, cause heart palpitations, and interfere with sleep, so it&#;s good to know how much your supplement contains.  

What is the best green tea extract?

If you&#;re not sure about which green tea extract supplement is right for you, there&#;s no need to worry. At Elo, we provide science-backed

personalized smart supplements

made just for you based on

at-home blood testing

,

biomarkers

, a questionnaire, and data from wearables. Depending on your goals, your personalized blend may contain green tea extract, along with a variety of other targeted supplements to help you feel your best. 

We also offer 1:1 dietitian support with our Elo Health coaches so you can stay accountable, reach your goals, and better understand your health. 

How to take green tea extract

Green tea extract supplements come in liquid, powder, and capsule form and are typically standardized to the amount of polyphenols or antioxidants they provide [

1

]. For topical applications, green tea extract can also be found in certain creams or skincare products. 

Green tea extract pills (capsules) are popular because they are convenient and don&#;t have as strong a taste as liquid and powder forms can. If you like the taste of green tea, you can dilute green tea extract liquid in a glass of water and blend green tea extract powder into smoothies. 

How much should you take?

While there are no official green tea extract dosing guidelines, studies have shown favorable effects with a green tea extract intake of 300-800 mg/day [

2

]. Intake of EGCG from supplements (which typically make up about 40-50% of the polyphenols in green tea extract) appears safe at 338 mg/day [

2

,

19

]. 

Green tea extract side effects

While green tea supplements are generally well tolerated, consuming large doses of green tea extract can increase the risk of side effects due to the caffeine content [

1

]. The side effects of green tea extract are comparable to caffeine and include restlessness, jitters, heart palpitations, and difficulty sleeping, and it may also worsen anxiety [

1

]. 

Green tea extract also contains a chemical linked with liver injury when used in high doses [

1

]. In humans, the maximum tolerated dose is around 4.2 g/m2 once daily, or 1.0 g/m2 thrice daily. For someone who is 5 feet 10 inches tall and weighs 150 pounds, acute toxicity would occur at a daily dose of 7.9 g/day or 1.9g 3x/day [

1

]. 

If you suddenly stop using green tea extract, you may experience caffeine withdrawal symptoms, such as headaches, irritability, and nervousness. To help prevent withdrawal, lower your dose slowly. Withdrawal is more likely if you have used green tea extract for a long time or in high doses [

20

].

Green tea extract precautions

Consult your doctor or pharmacist before taking green tea extract if you have any of the following conditions [

20

]: 

• Anemia (iron deficiency anemia)

• Bleeding problems

• Diabetes

• Glaucoma

• Heart problems such as irregular heartbeat or recent heart attack

• Stomach or intestinal problems such as ulcers or reflux disease (GERD)

• Liver problems

• Mental/mood disorders (such as anxiety and panic attacks)

• Low levels of calcium in the blood 

• Bone problems such as osteoporosis

Here are some other things to keep in mind before adding green tea extract to your routine.

May inhibit iron absorption

Green tea catechins, primarily EGCG, have been shown to inhibit iron absorption. To avoid this, consider taking green tea supplements two hours before or after eating iron-rich foods like meat, poultry, shellfish, beans, tofu, and fortified breakfast cereals. You can also reduce this interaction and enhance iron absorption by pairing your plant-based iron-rich foods with vitamin C [

2

]. 

Might reduce blood levels

Green tea has been shown to reduce blood levels and the effectiveness of certain blood pressure and heart medicines at high doses. Consult your healthcare provider before taking high doses of green tea extract [

20

]. 

May not be appropriate for pregnancy

If you are pregnant, consult your doctors about the risks and benefits of green tea extract supplements before taking them. As previously mentioned, most green tea supplements contain caffeine, and it is recommended that women limit caffeine during pregnancy. This product may also decrease folic acid, and low levels of folic acid are associated with an increased risk of neural tube defects [

20

].

Frequently asked questions about green tea extract

Is green tea extract safe?

Research repeatedly shows green tea extract is safe when taken in doses up to 800 mg/day, possibly for up to two years [

1

,

2

]. Individual studies have shown single doses from 1,200-1,600 mg EGCG can be tolerated; however, as dose size increases, so does the incidence of side effects [

2

]. 

Toxicity can occur from very high doses of green tea extract. In humans, the maximum tolerated dose is around 4.2g/m2 once daily, or 1.0g/m2 thrice daily. For example, for someone who is 5 feet 10 inches tall and weighs 150 pounds, acute toxicity would occur at a daily dose of 7.9 g/day or 1.9g 3x/day [

1

]. 

How long does green tea extract take to work? 

While you may experience benefits sooner, many studies have shown green tea extract benefits in as little as 8-12 weeks of supplementation [

2

]. 

Where does green tea extract come from?

Green tea extract comes from the leaves of the Camellia sinensis plant. For green tea, young leaves of the plant are harvested, withered, steamed, or pan-fried, then dried. This process preserves many beneficial compounds in green tea, which can then be extracted and consumed as a supplement.

Does green tea extract have caffeine? 

Green tea extract often has caffeine. The amount of caffeine in green tea extract can vary widely, from mild (2-50 mg caffeine) to mega-dose (>200 mg caffeine). 

If you&#;re new to green tea supplements or don&#;t regularly consume caffeine, it&#;s best to start with a supplement that contains a more modest amount of caffeine (30-50 mg) and adjust your intake accordingly. Up to 400 mg of caffeine daily appears safe for most healthy adults [

21

]. Taking green tea extract earlier in your day will also minimize the risk of its caffeine affecting your sleep.

If you prefer to avoid caffeine, decaffeinated green tea supplements contain little to no caffeine. 

Summary

Green tea extract is a highly concentrated form of green tea that contains potent antioxidants. Green tea has several health benefits, from supporting weight loss to boosting energy, skin, and heart health and even protecting against cancer. Moderate intake of green tea extract in the 300-800 mg/day range appears safe and effective, possibly for up to two years [

1

,

2

]. To get the most out of your green tea supplements, choose one that has been quality tested and contains EGCG. At Elo, our expert dietitians can help you determine whether green tea extract supplements might benefit you.

Disclaimer: The text, images, videos, and other media on this page are provided for informational purposes only and are not intended to treat, diagnose, or replace personalized medical care.

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