Green tea, an ancient beverage, has garnered significant attention in recent years for its potential health benefits, evolving into what many consider a superfood. Originating from the Camellia sinensis plant, the same source as black tea, green tea stands out due to its unique processing method. Unlike black tea, green tea leaves are not oxidized, preserving the plant's beneficial antioxidants. For centuries, people have enjoyed green tea’s light flavor and multiple health benefits. Around the globe, green tea consumption is on the rise.
Understanding Green Tea
The Camellia sinensis bush is the origin of green tea, specifically from its unoxidized leaves. It is one of the least processed types of tea, containing the most antioxidants and beneficial polyphenols. This minimal processing ensures that green tea retains a high concentration of polyphenols, particularly catechins, which are known for their antioxidant properties.
Green Tea vs. Black Tea: What's the Difference?
Both green and black teas are derived from the same plant, Camellia sinensis. The key difference lies in how the leaves are treated post-harvest. Green tea leaves are heated and dried immediately, preventing fermentation and preserving their light color and taste. In contrast, black tea leaves are left to ferment, resulting in a darker color and stronger flavor. Both teas contain antioxidants and caffeine, but in different forms. Brewed green tea typically has less caffeine than black tea, with the exception of matcha, a concentrated form of green tea made from ground whole leaves.
Potential Health Benefits of Green Tea
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.
Cancer Prevention
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 2020 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 over 1 million participants.
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A 2020 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.
Skin Protection
The topical application of green tea polyphenol extracts may have a role in protecting the skin from UVB radiation. A 2018 review of in vitro, in vivo, and human studies demonstrated the potential benefits of tea polyphenols in the chemoprevention of UVB-induced skin cancer. Green tea's many antioxidant properties may also give you younger-looking, healthier skin. Nonhuman studies found that polyphenols in green tea increase collagen and elasticity in skin, helping combat wrinkles and other signs of aging. Other studies that looked at applying green tea extract to the skin suggest it can help prevent acne and spot-treat pimples when they occur. A 2019 review suggests green tea phytochemicals may reduce skin aging.
Weight Management
A 2021 review suggests green tea and the catechin epigallocatechin gallate (EGCG) it contains may help people with obesity to reduce their body weight. A further review 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.
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.
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There’s some speculation that catechins in green tea can break down body fat and may rev up your metabolism, contributing to weight loss. A recent study conducted in Korea found that females who drank four or more cups of green tea each day had 44% less abdominal fat than their male tea-drinking counterparts. Green tea can also help manage your appetite and blood sugar levels, which can ultimately help with weight management, too, if consumed regularly.
Anti-Inflammatory Properties
Green tea has anti-inflammatory properties. Research highlights the anti-inflammatory effects of green tea. A 2019 analysis of tea extract 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.
Cholesterol Reduction
A 2020 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. Several studies indicate that green tea can lower cholesterol levels, helping reduce your risk of heart disease, heart attacks and stroke. High cholesterol can clog your arteries and is a major risk factor for heart problems. Antioxidants in green tea, including EGCG and other catechins, lower “bad” cholesterol (low-density lipoprotein or LDL) and total cholesterol. Green tea also has other heart-protecting flavonoids called quercetin and theaflavins. “Flavonoids open blood vessels and keep them flexible, helping blood flow more freely,” adds Zumpano.
Cardiovascular Health
According to a 2021 study, drinking large amounts of green tea without sugar may reduce the risk of death after a stroke or heart attack. A 2023 review and meta-analysis also associates moderate green tea consumption with a lower risk of stroke after evaluating five studies with 645,393 participants and 11,421 incidents of stroke. Several studies indicate that green tea can lower cholesterol levels, helping reduce your risk of heart disease, heart attacks and stroke.
Diabetes Management
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 in China associated 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. However, another long-term study of 119,373 adults without diabetes in China suggests that people who drank green tea had a higher risk of type 2 diabetes than those who did not drink it. The researchers suggest the risk increased with the amount of tea and duration of drinking it.
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Regular green tea consumption could lower many risk factors of heart disease, such as blood pressure or lipids.
People with Type 2 diabetes or those at risk of developing it (prediabetes) may benefit from drinking more green tea. Research suggests that green tea’s high levels of L-theanine may prevent diabetes. Other studies show that green tea helps improve blood sugar (glucose) and the body’s sensitivity to insulin.
Cognitive Function
A 2022 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 2018 study suggests acute green tea extract supplementation improved working memory capacity in 10 females ages 50 to 63, although there was no significant effect for younger adults. Similarly, another study examined the effect of green tea catechins on adults ages 50 to 69 in Japan. The authors suggest daily green tea supplementation may benefit working memory.
Amino acids, such as L-theanine, and catechins, like EGCG, have brain-protective benefits. A study of middle-aged and older adults found that frequent green tea drinkers had a 64% lower risk of memory loss or concentration issues. This risk reduction was almost 20% higher than study participants who drank black tea.
According to a 2021 review, certain amino acids in green tea have an anti-stress element that helps to slow brain aging. This may be due to the neuroprotective effects, including anti-inflammation and anti-oxidative stress, of certain catechins in green tea.
Other Potential 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. Other research suggests green tea may have the following effects:
- Prevent tooth decay
- Improve osteoarthritis pain
- Antiallergic effect
- Promote wound healing
However, further human clinical trials are necessary to firm up these theories.
Bone Health
A meta-analysis of 17 different studies found that drinking tea can protect against osteoporosis and broken bones. Findings suggest that EGCG and other polyphenols in green tea can strengthen bones by improving bone density and reducing how much bone you lose as you age.
Prostate Health
Laboratory studies (nonhuman) suggest that polyphenols in green tea - especially EGCG - may prevent benign prostatic hyperplasia (BPH). BPH causes an enlarged prostate, leading to frequent urination and other issues. Findings suggest that EGCG stops prostate cells from multiplying and enlarging the gland. But human research is needed before we’ll know for sure.
Stress and Anxiety Reduction
The L-theanine in green tea can help ease stress and anxiety. “Worrying and stress can raise blood pressure, affect mood and sleep, and negatively affect your quality of life,” states Zumpano.
And research shows that L-theanine significantly impacts the effects of caffeine. It reduces its stimulating effects and improves cognitive function, mood and concentration.
Nutritional Information
Since green tea also contains small amounts of caffeine, some people may enjoy it as a substitute for coffee or other caffeinated drinks.
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 48 mg per cup, and coffee, which has 96 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 consists of about 90% polyphenols, which includes catechins like EGCG.
Vitamins and Minerals in Green Tea
Vitamins and minerals found in green tea are also minimal. A few that can be found in small quantities include:
- Calcium
- Iron
- Potassium
Forms of Green Tea
Green tea is available in many types and forms, including:
- Bottled and sweetened with sugar or an artificial sweeteners
- Single tea bags
- Loose leaf
- Instant powder
- Green tea supplements, in capsule form or as liquid extracts
Potential Side Effects and Risks
In adults, there are few known side effects of drinking green tea. However, the following risks and complications are important to note:
- Caffeine sensitivity: People with severe caffeine sensitivities could experience symptoms such as insomnia, anxiety, irritability, nausea, or an upset stomach after drinking green tea.
- Liver damage: Consuming a high concentration of green tea extract may adversely affect 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 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.
How Much Green Tea Should You Drink?
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. Research suggests adults may tolerate up to 24 cups of green tea daily, although this is not necessarily a recommended daily intake. 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.
There isn’t a perfect number of cups of green tea to drink each day for optimal health. “Most people can safely drink up to eight cups of green tea each day, or six cups if you’re pregnant or nursing,” shares Zumpano. The amount really depends on how your body responds to caffeine. And if you’re choosing matcha, Zumpano recommends no more than 2-4 teaspoons per day. That’s because research suggests that 338 milligrams of catechin and EGCG per day are safe for adults to consume. This is the amount in about 4 grams of matcha, or two level teaspoons.
Experts recommend that people who are pregnant or breastfeeding limit their caffeine intake to no more than 200 milligrams a day. And children under 12 shouldn’t have caffeine at all.
What Not to Take with Green Tea
Green tea, whether caffeinated or decaf, can reduce iron absorption. So, it’s best to take iron supplements separately. Green tea may interact with some medications, including those used to treat high blood pressure, heart problems, and osteoporosis. Ask your doctor what’s safe.
How to Enjoy Green Tea
If you love tea, consider adding green tea to your day. Thanks to quick harvesting and processing, green tea has a lighter look and is less bitter than black tea. Some people describe the taste as sweet, earthy or nutty.
You can also give matcha a try. This frothy beverage made from finely ground green tea leaves has an even stronger concentration of nutrients and antioxidants. But its stronger, bolder taste and chalkier drink texture might be a turn-off if you’re new to green tea.
Improper brewing can make green tea too bitter.
Green Tea Recipe
Use these ingredients to make green tea:
- 3 cups filtered water
- 4 green tea bags
- 1 tablespoon ginger root, peeled and thinly sliced
- 2 tablespoons fresh lemon juice, plus 4 slices for garnish
- 2 tablespoons honey
Then follow these directions:
- Bring water to just below boiling point. Remove from heat.
- Place tea bags in a pitcher, and add ginger slices. Pour hot water over the tea bags. Let them steep for 8-10 minutes. Remove the tea bags.
- Stir in lemon juice and honey.
- Serve warm or iced.