The Health Benefits of Green Tea (2024)

Green tea contains antioxidants and other health-promoting compounds that may boost brain health, support heart health, protect against certain cancers, and more.

Green tea is made from the leaves of the Camellia sinensis plant. Though all varieties of tea come from the same plant, green tea is considered the healthiest because of how it is processed.

This article covers the known and potential health benefits of green tea, possible side effects, and what to look for when buying green tea for consumption or use as a dietary supplement.

The Health Benefits of Green Tea (1)

Nutritional Benefits of Green Tea

Green tea contains high levels of natural polyphenols, and antioxidants called catechins (a family of potentially beneficial plant chemicals).

Epigallocatechin-3-gallate (EGCG) is the most abundant catechin in green tea. Studies show ECGC has:

  • Improved cardiovascular health
  • Enhanced cognitive function
  • Promoted weight loss
  • Regulated blood sugar levels
  • Supported digestive health
  • Protected against certain types of cancer

A one-cup serving of unsweetened green tea has about two to three calories. It also contains trace amounts of minerals like potassium, magnesium, and iron.

Adding milk, sugar, or honey may enhance the flavor of green tea. However, these additions alter tea's nutritional content.

Some studies suggest that adding milk to tea may reduce its antioxidant benefits.

Caffeine in green tea

Green tea contains about 28 mg of caffeine per 8-ounce cup. However, certain factors can affect the caffeine content, including water temperature and brewing time. Hot water (vs. cold brewing) and longer steeping time will extract more caffeine. The Food and Drug Administration (FDA) suggests limiting caffeine to 400 mg per day for adults.

What Are the Benefits of Green Tea?

Green tea has a long history in China, where it has been enjoyed as a richly flavored beverage and used for medicinal purposes for thousands of years. It has gained popularity and is consumed worldwide for its many acclaimed health benefits.

To make green tea, young leaves of the plant are harvested, withered, steamed, or pan-fried, then dried. This process helps prevent fermentation and preserves many beneficial compounds in tea leaves.

The research below highlights the health benefits of green tea and green tea extract.

Provides Antioxidants

Green tea has a high concentration of antioxidants, which are responsible for the beverage's health benefits. Tea is rich in a type of antioxidant called polyphenols—natural compounds that reduce inflammation, protect against oxidative stress, and prevent cell damage.

Protects Cardiovascular Health

Drinking green tea might protect against cardiovascular diseases and lower the risk of heart attack and stroke. A review of 31 research studies found that green tea is associated with significant reductions in total cholesterol and low-density lipoprotein (LDL), or "bad" cholesterol.

Green tea's anti-inflammatory compounds, like EGCG, have been proven to relax blood vessels and reduce vascular inflammation (inflammation of the blood vessels).

The optimal amount of daily green tea intake for heart health benefits is unknown. Still, evidence suggests that drinking three to five cups of green tea daily, alongside a healthy diet, is associated with a 41% lower risk of dying from cardiovascular disease.

Boosts Brain Health

Green tea benefits brain health by:

  • Improving mood
  • Reducing stress
  • Enhancing cognitive function
  • Protecting against age-related cognitive decline and neurodegenerative diseases.

Green tea contains caffeine, a stimulant that boosts mood, energy levels, reaction time, and memory. Along with caffeine, green tea contains L-theanine, an amino acid that positively affects mood, lowers stress, and boosts dopamine and serotonin production. Caffeine and L-theanine work together to improve mood, reaction time, attention, and memory.

Research shows that the catechins in green tea, such as EGCG, fight free radicals, protect neurons (brain cells) from damage, and delay or prevent the death of these cells. Catechins may protect against neurodegenerative diseases such as Alzheimer’s disease, dementia, and Parkinson’s disease.

One study found that drinking green tea may lower the risk of age-related cognitive decline by 64% after adjusting for risk factors that can impact cognitive function, like age, lifestyle behaviors, and underlying disease.

Promotes Weight Loss

Several studies investigating the connection between green tea consumption and weight loss have found that the caffeine and catechins in green tea may speed up metabolism and help burn fat.

One study exploring the effects of green tea extract (GTE) on weight loss found that 12 weeks of 856.8 milligrams of GTE supplementation daily led to significant weight loss and lower body mass index (BMI) for study participants.

A holistic plan for healthy weight loss and management is essential. Be sure to contact your healthcare provider or registered dietitian nutritionist (RD/RDN) to evaluate your current dietary patterns, stress management, body composition, and other factors. A balanced diet rich in fiber, lean protein, fruit, and non-starchy vegetables is key, as is regular movement.

BMI is a dated, flawed measure. It does not take into account factors such as body composition, ethnicity, sex, race, and age. Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.

Regulates Blood Sugar Levels

Type 2 diabetes is associated with elevated blood sugar levels, which occurs when the body doesn't produce enough insulin or use it correctly. Studies show that green tea may protect against type 2 diabetes by regulating blood sugar levels and improving insulin resistance.

A review and analysis of 19 studies involving over 1 million adults across eight countries found that drinking at least four cups of black, green, or oolong tea per day over 10 years may contribute to a reduced risk of type 2 diabetes. The review and analysis researchers noted that the study's data was subjective and potentially skewed by additional lifestyle factors.

A study of Chinese adults showed that daily green tea consumption is associated with a lower risk of type 2 diabetes and a reduced risk of diabetes-related health complications and mortality in people with diabetes.

Protects Against Certain Types of Cancer

Green tea is rich in polyphenols, which help fight free radicals and may help protect cells and DNA from damage and oxidative stress. These antioxidant properties also play a role in cancer prevention.

Oxidative stress can cause chronic inflammation, which can lead to cancer development. Research shows that antioxidants in green tea may help lower the risk of certain types of cancers, including:

  • Breast cancer: Drinking green tea may reduce the risk of breast cancer by 15%.
  • Colorectal cancer: Studies show that green tea drinkers have a 30–40% lower chance of developing colorectal cancer.
  • Oral cancer: Research suggests long-term tea consumption is associated with a lower risk of developing oral cancer.

Remember that green tea alone does not reduce your risk of these cancers. Maintaining healthy lifestyle behaviors is essential to improving your overall health.

Relieves Inflammatory Skin Conditions

One study examined the effects of black, green, and white tea extracts on psoriatic skin inflammation in mice. The study authors concluded all three tea extracts prevented skin inflammation by reducing the expression of inflammatory markers.However, it is not known whether the tea extracts would have the same effect in humans.

Animal models and in vitro studies have shown that topical treatment with green tea polyphenols reduces skin inflammation, and external application of EGCG decreases inflammatory markers. However, clinical trials on human skin are necessary to confirm green tea's therapeutic benefits.

Improves Oral Health

A 2017 review of the effects of green tea on oral health concluded that the polyphenols in green tea have a beneficial role in preventing periodontal (gum) and oral diseases. The antioxidant, anti-inflammatory, and antibacterial properties of green tea and green tea extract are thought to improve oral health. It is important to note that most of the studies in this review were conducted in the laboratory, not in humans.

A 2021 review concluded that although study results are encouraging, there is insufficient evidence to recommend green tea as a first-choice treatment forgingivitis, periodontitis, and dental cavities.

What Are the Side Effects of Green Tea?

Green tea can be consumed every day. In fact, up to 8 cups per day is considered safe.

Green tea contains about 28 mg of caffeine per cup. The Food and Drug Administration (FDA) suggests limiting caffeine to 400 mg per day for adults. Eight cups of green tea would have around 220 mg of caffeine.

Drinking more tea than the recommended amount may cause side effects associated with too much caffeine, such as:

  • Jitteriness/restlessness
  • Insomnia
  • Headache
  • Dizziness
  • Rapid heart rate
  • Dehydration
  • Frequent urination

Talk to your healthcare provider before consuming green tea or green tea extracts if you:

  • Are pregnant: Pregnant people can safely consume up to six cups of green tea daily. However, green tea may increase the risk of congenital disorders in infants whose pregnant parent has a folic acid deficiency.
  • Have liver disease: There are some reports that green tea can cause liver injury. Signs of liver injury can include abdominal pain, dark-colored urine, and jaundice.
  • Take beta-blockers: At high doses, green tea may reduce blood levels and inhibit the effectiveness of a prescription drug called Corgard (nadolol)—a beta-blocker prescribed to treat high blood pressure and some heart diseases.

If you are nursing, green tea is safe for consumption, but remember that caffeine passes through breast milk and can affect your baby.

Selection and Storage

Green tea is available in bags, sachets, loose-leaf, or a powder form known as matcha. Green tea extracts are available in capsule, liquid, and powder forms.

Green tea can be enjoyed as an iced or hot beverage. It is typically prepared by brewing the tea in hot water at 90 degrees Celsius or 194 degrees Fahrenheit (just below boiling) and steeping for two to five minutes. The longer you steep, the more robust the flavor and the more components your beverage will contain (L-theanine, caffeine, etc.).

Store green tea products in an airtight container in a cool, dry, dark place. Some research suggests that storing tea at a low temperature may help prolong its shelf life and protect it from oxidation.

In the United States, the Food and Drug Administration (FDA) does not regulate supplements like prescription drugs. This means some supplement products may not contain what the label says.

Whenchoosing a supplement, look for third-party tested products and consult a healthcare provider, registered dietitian nutritionist (RDN or RD), or pharmacist.

Summary

Green tea provides several science-backed health benefits. The antioxidants in green tea can help protect your heart, improve brain health, promote weight loss, regulate blood sugar, and more. Green tea is generally safe in moderation, and most adverse side effects are related to its caffeine content. People who are pregnant or lactating, taking beta-blockers, or have liver disease should consult their healthcare provider before adding green tea to their daily routines.

The Health Benefits of Green Tea (2024)

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