Green Tea: Benefits, Side Effects, and Preparations

Green tea

Verywell / Alexandra Shytsman

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Green tea contains polyphenols (micronutrients), caffeine, and antioxidants shown to provide numerous health benefits. In fact, green tea is said to be richer in antioxidants compared to other forms of tea. The antioxidant-rich plant compounds making this drink so healthy are called flavonoids. The most common flavonoid in green tea is a catechin known as epigallocatechin gallate (EGCG). Green tea also contains theanine (L-theanine), an amino acid shown to reduce anxiety. Other antioxidants found in green tea leaves are called proanthocyanidins and may help reduce inflammation in the body.

Green tea contains trace amounts of vitamins but is a rich source of minerals including magnesium, potassium, and sodium. Other minerals found in green tea include chromium, calcium, zinc, and more. The concentration of these minerals is said to be dependent on the fermentation process, age, and size of the green tea leaves.

What Is Green Tea?

All green tea comes from the same plant called Camellia sinensis and is offered in several varieties. Green tea will vary in flavor and color depending on growing methods, harvesting, and processing.

Green tea differs from black or oolong because the green tea leaves are picked, steamed, and roasted raw. This halts oxidation to the leaves and preserves many of the essential nutrients and antioxidants.

Sencha is the most commonly drunk and well-known variety of Japanese green tea. The tea leaves are said to be the best quality because they come from the first harvest. The leaves are steamed, dried, and rolled, releasing the juices within the leaves for an intense flavor.

The harvesting process for Gyokuro green tea differs from Sencha as the green leaves are removed from sunlight about three weeks before harvest. Without direct sunlight, less photosynthesis occurs retaining strong-flavored amino acids. The tea leaves are steamed, dried, and rolled similar to Sencha; Gyokuro green tea has a richer flavor and is more costly given the additional steps to cultivate.

Tencha is used as the main ingredient to Matcha green tea. Similar to Gyokuro, the green leaves are removed from sunlight three weeks before harvest. The leaves are steamed but dried without being rolled. This gives the tea a pale green color and mellow flavor.

Matcha, which is stoneground Tencha, is Matcha green tea. Once the green tea leaves are steamed and air-dried, stems and veins are removed and ground into a powder ready for brewing. Matcha green tea is a light green color with an intensely rich taste with a lingering sweetness.

Funmatsucha ground tea leaves usually not high quality and cheaper in price. The harvesting is different than Matcha in that it receives no protection from the sunlight. The end product is a green tea with a bitter flavor.

Konacha green tea is made from the small leaves left behind after Sencha and Gyokuro processing. It is less expensive because it is a natural byproduct of other tea production and does not need to be cultivated by itself. This green tea has an intense green color and a strong bitter taste.

Shincha means “new tea” because it comes from the first harvest of Japanese green tea. Only the young, tender leaves are harvested by hand, steamed, dried, and rolled. This means the green tea leaves are of the highest quality and the most expensive. The flavor is light and refreshing.

A combination of Sencha, Gyokuro, and Kabusecha green tea leaves, Fukamushicha green tea leaves undergo a deep steaming process creating a deep color and rich flavored green tea.

Also referred to as a twig tea, Kukicha is made from the stems and veins of tea leaves initially harvested for Sencha and Matcha green teas. It contains minimal caffeine, is yellow in color, and has a mild, creamy sweet flavor.

Bancha is cultivated and processed the same way as Sencha, but comes from later harvests. This means the green tea is considered lower grade and because of that is more budget-friendly. It has a golden color and a nutty sweet flavor.

How to Prepare

There are many ways to make green tea, from iced to warm. Keep in mind that adding additional ingredients may alter the nutrition content. Check out these recipes for delicious ways to prepare this popular health drink.

Caffeine Content

In addition to valuable antioxidants, green tea contains about 25mg of caffeine per cup. This means it has stimulant properties, but much less than a cup of black coffee containing between 95 to 165mg of caffeine per cup. That said, experiencing the jitters typical with higher caffeine doses from a cup of coffee is usually not associated with drinking a cup of green tea.

Health Benefits

Green tea is a popular nutritious drink associated with a healthy lifestyle. Because green tea contains valuable phytochemicals, it is shown to play a valuable role in disease prevention. It also has minimal calories, provides superior antioxidants, and contains a fair amount of caffeine.

Many of the health benefits of green tea come from the antioxidants, and other valuable chemical compounds found in the green leaves. Research has indicated green tea to be associated with a wide range of medicinal properties.

Lowers the Risk of Diabetes

Green tea contains the catechin epigallocatechin gallate (EGCG) and polyphenols. Several studies indicate EGCG in green tea may help regulate blood glucose (sugar) in the body helping to prevent or control diabetes. A few other studies claim green tea to improve metabolic function directly related to a lowered risk of diabetes. There is conflicting evidence to support these claims but most research represents green tea as an attractive alternative to promoting human health, including a lowered risk of diabetes.

Supports Heart Health

Several studies indicate green tea may have beneficial effects on cardiovascular health. The catechins in green tea, especially EGCG decrease the absorption of triglycerides (fat) and cholesterol. The reduction of fat in the blood helps to prevent plaque buildup (atherosclerosis) reducing the risk of heart attack or stroke.

Improves Digestive Health

The catechins (antioxidants) found in green tea are well absorbed in the gastrointestinal tract, according to research. After drinking green tea, intracellular antioxidants were found to be activated in the gastrointestinal tract to improve digestive health. Drinking green tea is said to be one of the most simple and beneficial ways to prevent gastrointestinal disorders.

Lowers Risk of Certain Cancers

The catechins and polyphenols in green tea may reduce the risk of various types of cancer, according to research. These powerful antioxidants are shown to activate detoxification enzymes that may help reduce tumor development. Green tea research is ongoing and has shown promising results to lower the risk of certain cancers including prostate, lung, breast, colon, and liver cancers.

Decreases Inflammation

Green tea contains a unique set of catechins with significant antioxidant and anti-inflammatory properties, according to studies. Inflammation is a normal bodily response to injury, infection, or destruction where the body is trying to destroy invading organisms, remove irritants, and set the stage for tissue repair. Antioxidants contained in green tea are shown to significantly help with this repair and reduce inflammation.

Stimulates Weight and Fat Loss

Studies indicate green tea may help reduce body weight, mainly body fat. According to a small human study, green tea rich in EGCG has the potential to increase fat oxidation (burning) and contribute to the anti-obesity effects of green tea. Caffeine in green tea is also shown to increase fat oxidation and improve metabolic function, another contributing factor to weight loss.

Lowers the Risk of Neurological Disorders

Several studies have found green tea to have beneficial effects on neurodegenerative impairment, including cognitive dysfunction and memory loss. Brain disorders such as Parkinson’s Disease have also shown positive results with green tea consumption. It appears that the catechin EGCG in green tea helps prevent fibrous proteins associated with neurological disease to accumulate in the brain. Studies also suggest green tea has the potential to be used in the prevention and treatment of neurodegenerative diseases.

Reduces Stress and Anxiety

Green tea contains theanine (L-theanine), an amino acid shown to reduce anxiety and stress. According to a pilot study, the anti-stress effects are best consuming low-caffeine green tea. Some studies indicate green tea with combined theanine and caffeine at normal levels still produced a reduction in anxiety. Either way, it appears green tea has a positive effect on lowering stress and anxiety.

Helps Anti-Aging

Green tea phytochemicals contain potent antioxidants that may reduce premature aging of the skin. Several studies suggest green tea consumption increases the collagen and elastin fiber content and suppresses collagen degrading enzyme (MMP-3) production. Although the exact mechanism behind the anti-aging effects is unclear, green tea appears to promote an anti-wrinkle effect.

Improves Oral and Dental Health

Green tea polyphenols protect against bacterial tooth decay and plaque buildup, according to studies. The plant compounds in green tea are said to control bacteria and lower acidity levels in saliva and dental plaque. Because of these results, research indicates drinking green tea as a useful tool in cavity prevention. Green tea is also shown to reduce halitosis (bad breath) since EGCG provides a deodorizing effect by reducing odorant sulfur components.

Side Effects

Green tea is shown to have numerous health benefits when consumed in moderate amounts. However, research indicates higher doses may have the potential to cause some known and unknown adverse effects.

The catechin EGCG can be toxic to living cells in higher doses. For example, higher consumption of green tea above 800mg daily may pose a potential risk of liver damage. A single cup of brewed green tea typically contains between 50-100mg EGCG.

The caffeine content in green tea has stimulant properties with the potential to cause adverse health effects in certain people. Research indicates green tea should not be consumed by patients suffering from heart conditions or major cardiovascular problems. Pregnant women or those who are nursing should drink no more than one or two cups daily because caffeine can cause increased heart rhythm.

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  1. Chacko SM, Thambi PT, Kuttan R, Nishigaki I. Beneficial effects of green tea: a literature review. Chin Med. 2010;5:13.

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