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Green tea is the world's most popular health drink

Green tea

Camellia sinensis

Theaceae

Green tea constituents work together to improve blood supply, brain performance, mood, and carbohydrate and fat metabolism.

Sustainability Status

Sustainability status

Not currently on risk lists but complete data may be missing on the status of the species. Read more about our sustainability guide.

Key benefits
  • A refreshing and uplifting beverage
  • Maintaining health and wellbeing
  • Preventing diabetes and circulatory disease
  • Reducing effects of ageing on brain performance

  • How does it feel?

    Look for the finest quality green tea, perhaps a matcha blend, and in a cup pour on water just off the boil. The colour of the water will move from an immediate greenish-yellow to a darker yellow-brown. Do not add milk or whitener. After five minutes take a sip and note the familiar dry, refreshing taste, only subtly aromatic. If you take this in hot weather, you will also feel the cooling effect of even a hot cup of green tea.

    Green tea is bitter, astringent, light and drying and safe to take regularly over many years.

    Green tea (Camellia sinensis)
    Green tea (Camellia sinensis)
    Green tea (Camellia sinensis)

  • What can I use it for?

    Green tea is a healthy and refreshing daily drink that can be a good replacement for coffee, and may be better tolerated than black tea. There is some suggestion that it can be a useful part of a weight-loss regime.

    For health problems it may best be seen as a long term health and wellbeing measure rather than a quick fix. It can be considered as a preventative against heart and circulatory disease, late-onset diabetes, and even dementia. Green tea’s actions are likely most beneficial in individuals with high cholesterol levels, high blood pressure, and/or raised BMI (body-mass index).

  • Into the heart of green tea

    Green tea, particularly its key ‘EGCG’ and other catechin constituents, have extraordinary antioxidant properties in the laboratory (stronger than vitamin C or E). However these are artificial environments and the real impact of antioxidants after consumption, digestion and metabolism in humans has been heavily over-promoted. Nevertheless the catechins in green tea appear to optimize the body’s own antioxidant defences, including via the ‘Nrf2 pathway’. This is likely to explain many of the health benefits of regular green tea consumption, particularly in reducing low-level inflammatory conditions. A very interesting area of benefit is in cases of ‘neuroinflammation’: recent observations that many brain and nervous problems may involve inflammation. A role here could justify the use of green tea, for example in chronic fatigue syndromes and to help prevent dementia.

    A key part of the benefits of green tea are linked to its observed effects on improving the health and integrity of the lining of the blood vessels, the endothelium. It is at this surface that almost all inflammatory processes commence and ‘endothelial dysfunction’ has been implicated in a wide range of inflammatory diseases, cardiovascular problems, dementia and diabetes. Endothelial stresses may even contribute to the effects of ageing on the brain and nervous system.

    Closely linked to this endothelial impact are likely benefits of green tea in reducing insulin resistance and improving glucose and fat metabolism. Modern lifestyles have dramatically increased insulin activity in the body, notably as a consequence of high carbohydrate diets and reduced exercise. Higher insulin levels eventually lead to endothelial and other cells becoming ‘insulin resistant’ with consequent disrupted sugar management and more fat storing. This ‘metabolic syndrome’ is associated with the onset of type 2 diabetes and associated cardiovascular problems, increased dementia risks and other long-term health consequences, and is perhaps the dominant health issue in modern developed societies.

    Green tea is also a moderate source of caffeine. Caffeine in this context enhances cognitive alertness and helps to overcome fatigue and lift mood.

  • Traditional uses

    Green tea has been an important part of Chinese, and later Japanese and Korean social life over almost two millennia. The earliest accounts of Tea Ceremonies come from China around 1200 years ago during the Tang Dynasty when the ritual of infusing and serving tea was part of a religious ceremony called cha dao or ‘The Way of the Tea’.

    Outside China tea was brought to Europe in the 16th century and became popular in Britain, with black tea overtaking green tea to become its most popular drink during the 18th century. It was initially promoted through ‘tea houses’ as a tonic and health drink before becoming a popular beverage. The British East India Company introduced tea production, as well as tea consumption, to India, in order to compete with the Chinese monopoly on tea.

  • Traditional actions

    Herbal actions describe therapeutic changes that occur in the body in response to taking a herb. These actions are used to express how a herb physiologically influences cells, tissues, organs or systems. Clinical observations are traditionally what have defined these actions: an increase in urine output, diuretic; improved wound healing, vulnerary; or a reduction in fever, antipyretic. These descriptors too have become a means to group herbs by their effects on the body — herbs with a nervine action have become the nervines, herbs with a bitter action are the bitters. Recognising herbs as members of these groups provides a preliminary familiarity with their mechanisms from which to then develop an understanding of their affinities and nuance and discern their clinical significance.

    Western actions

    Chinese actions

  • Traditional energetic actions

    Herbal energetics are the descriptions Herbalists have given to plants, mushrooms, lichens, foods, and some minerals based on the direct experience of how they taste, feel, and work in the body. All traditional health systems use these principles to explain how the environment we live in and absorb, impacts our health. Find out more about traditional energetic actions in our article “An introduction to herbal energetics“.

  • What practitioners say

    All the evidence and traditional usage points to the benefits of green tea being from drinking it regularly as part of a healthy lifestyle. This beverage habit, rather than supplements or practitioner prescriptions, is probably the most practicable option too. However the evidence points to some benefits being seen in only a few weeks and practitioners are likely to recommend drinking more green tea for the following purposes.

    Brain performance

    Consumption of green tea, preferably as a life-long habit, is particularly helpful to reduce the effects of ageing and illness on cognitive function, memory retention and and other performance. The L-theanine in green tea increases serotonin, dopamine and gamma-aminobutyric acid (GABA) in the brain, all of which significantly boost mood, indicating it also in anxiety and depression.

    Metabolic

    Green tea is recommended where there is a slow or under-active metabolic rate associated with higher BMI (body-mass index), belt size and other indicators of ‘metabolic syndrome’ all of which may point to late-onset diabetes and fatty liver problems.

    Cardiovascular

    The EGCG’s present in green tea protect the integrity of the blood vessels, so regular consumption is useful in any cardiovascular problem.

    Skin

    It has traditionally been used in inflammatory skin conditions associated with hormonal imbalance.

  • Research

    There is considerable evidence for the effects of long-term green tea intake in improving cognitive performance. In a major systematic review of the evidence (3), involving over 66,000 subjects, there were significant improvements in memory and cognition in those who drank one or more daily cups of green tea regularly.

    Given the likely role of endothelial dysfunction in the origins of inflammatory processes, cardiovascular problems, and ageing, it is noteworthy that there are clinical studies (4,5) that reinforce the laboratory observations that green tea does improve endothelial function, with wider benefits on the cardiovascular system (6).

    It is also interesting to note that regular green tea consumption seems to help reduce associated problems of insulin resistance and disrupted glucose and fat metabolism. In a cross-sectional survey of almost five thousand healthy adults in China, between 1-30 cups of green tea per week was associated with lower rates of blood sugar impairment (7). In one systematic review involving almost two thousand subjects green tea was found significantly to lower fasting blood glucose levels (8). In another study, green tea was found significantly to improve measures linked to metabolic syndrome: to decrease weight, BMI (body-mass index), total and low density cholesterol, fat mass, and waist and hip circumference (9).

    In a double-blind randomised controlled clinical trial of 60 individuals with raised cholesterol levels 600ml catechin-rich green and oolong tea taken daily for 12 weeks significantly reduced antioxidant enzymes and other measures of oxidative stress, with reductions also in body weight, fat levels and BMI. Markers of fatty liver levels were also improved (10). Green tea was seen in another systematic review of 600 patients with type 2 diabetes, to reduce C-reactive protein levels, one of the classic markers of inflammatory stress (11).

    The suggested role of green tea in preventing cancer has been boosted by recent research into mechanisms of action of EGCG (12).

  • Did you know?

    Tea is the most commonly consumed beverage in the world after water, with total annual sales exceeding US$43 billion globally in 2015, more than $11 billion of which is accounted for by green tea.

Additional information

  • Botanical description

    Green tea, black tea and white tea are all produced from the same plant, Camellia sinensis. Two varieties are widely used as sources of most of the tea around the world, Camellia sinensis var sinensis which is commonly known as Chinese tea and C. sinensis var. assamica or Assam tea. Tea is an evergreen shrub native to East Asia and possibly originating in the borderlands of northern Burma and southern China. It has hybridized over at least 20,000 years and now most original wild varieties have disappeared. It is now mainly cultivated in China, India and Vietnam. It can grow to heights of 17 metres and is a tree in some locations. The leaves are a distinct bright and shiny green with a hairy underside.

    The flowers are a creamy white with a light scent and grow in clusters of two or four. The fruits of the tea plant are a brownish-green and can contain up to four seeds.  The Chinese variety is considered to be slightly more ‘hardy’ and its leaves are generally smaller and more narrow. It is primarily this variety that is used to produce Green tea.

  • Common names

    • Grüner Tee (Ger)
    • Thé vert (Fr)
    • Tè verde (Ital)
    • Té verde (Sp)
    • Haree chaay (Hindi)

  • Safety

    Moderate consumption of green tea as a beverage is safe and very widespread. There are concerns with taking high doses of green tea extract, with some cases of liver damage reported. Levels of EGCG are accepted as being a useful determinant of safety and this is more concentrated in extracts: a review of toxicological and human safety data suggests a safe intake level of up to 700 mg EGCG/day for adults when green tea is taken as a beverage. The estimated daily intakes of EGCG can reach approximately 560 mg/day if consuming three 8 oz. cups of green tea per day (13).

  • Dosage

    1-3 teaspoons dried leaf infused in hot (not boiling) water, one to three times a day.

  • Constituents

    Green tea has similar constituents to the fresh leaf (1):

    • Flavanols up to 30% dry weight including catechins (epigallocatechin gallate (EGCG), epicatechin (EC),  gallocatechin (GC), epigallocatechin (EGC), epicatechin gallate (ECG), and gallocatechin gallate (GCG)); also chlorogenic acid, coumarylquinic acid, theogallin (3-galloylquinic acid)
    • Methylxanthines caffeine (2.5-4.5%), theobromine, theophylline (only traces)
    • Amino acids incl. L- theanine (5-nethylglutamine)

    According to the United States Department of Agriculture (USDA) brewed green tea contains an average of 126.6 mg total catechins and 77.8 mg EGCG per 100 ml, on the basis of 1 g leaf/100 mL infusion.

    Black tea involves the oxidation of the catechins, enzymatically producing various condensation quinone compounds, including thearubigens, bisflavanols, theaflavins, epitheaflavic acids, which impart the characteristic taste and colour properties of black tea, as well as proanthocyanidins. Most of these compounds readily form complexes, including with caffeine. These complexes are erroneously given the name ‘tannins’: in fact there is no tannic acid in black tea.

    The catechin EGCG translates its powerful antioxidant properties in the laboratory into real benefits by reducing inflammatory damage in the body (2).

Green tea (Camellia sinensis)

  • Recipe

    Natural Balance Tea

    When our digestive fire is low and our metabolism feels sluggish it cannot transform food into nourishing energy. Instead, food can get stored as fat, starting a vicious cycle where digestion becomes weaker and weaker, leading to steady weight gain. This delicious tea helps to stimulate the metabolism and supports your body to find your natural and balanced weight.

    Ingredients:

    • Cinnamon bark 4g
    • Ginger root powder 2g
    • Orange peel 2g
    • Green tea 2g
    • Turmeric root powder 1g
    • Black pepper 1g
    • Orange essential oil a drop per cup

    This will serve 2–3 cups of digestion enhancing, weight-balancing tea that works together with lots of exercise.

    Method:

    • Put all of the ingredients in a pot (except for the orange essential oil).
    • Add 500ml (18fl oz) freshly boiled filtered water. Leave to steep for 10–15 minutes, then strain.
    • Add one drop of orange essential oil to each cup

  • References

    1. Graham HN (1992) Green tea composition, consumption, and polyphenol chemistry. Preventive Medicine, 21, 3: 334-350
    2. Kanlaya R, Thongboonkerd V. (2019) Molecular Mechanisms of Epigallocatechin-3-Gallate for Prevention of Chronic Kidney Disease and Renal Fibrosis: Preclinical Evidence. Curr Dev Nutr. 2019;3(9):nzz101
    3. Mancini E, Beglinger C, Drewe J, et al (2017). Green tea effects on cognition, mood and human brain function: A systematic review. Phytomedicine. 34: 26-37
    4. Alexopoulos N, Vlachopoulos C, Aznaouridis K, et al. (2008) The acute effect of green tea consumption on endothelial function in healthy individuals. Eur J Cardiovasc Prev Rehabil. 15(3): 300–305
    5. Lorenz M, Rauhut F, Hofer C, et al. (2017) Tea-induced improvement of endothelial function in humans: No role for epigallocatechin gallate (EGCG). Sci Rep. 7(1): 2279
    6. Wasilewski R, Ubara EO, Klonizakis M. (2016) Assessing the effects of a short-term green tea intervention in skin microvascular function and oxygen tension in older and younger adults. Microvasc Res. 107:65–71
    7. Huang H, Guo Q, Qiu C, et al. (2013) Associations of green tea and rock tea consumption with risk of impaired fasting glucose and impaired glucose tolerance in Chinese men and women. PLoS One. 8(11): e79214
    8. Kondo Y, Goto A, Noma H, et al. (2018)  Effects of Coffee and Tea Consumption on Glucose Metabolism: A Systematic Review and Network Meta-Analysis. Nutrients. 11(1): 48
    9. Payab M, Hasani-Ranjbar S, Shahbal N, et al. (2020) Effect of the herbal medicines in obesity and metabolic syndrome: A systematic review and meta-analysis of clinical trials. Phytother Res. 34(3): 526-545
    10. Venkatakrishnan K , Chiu HF , Cheng JC , et al. (2018) Comparative studies on the hypolipidemic, antioxidant and hepatoprotective activities of catechin-enriched green and oolong tea in a double-blind clinical trial. Food Funct. 9(2): 1205-1213
    11. Asbaghi O, Fouladvand F, Gonzalez MJ, et al. (2019) The effect of green tea on C-reactive protein and biomarkers of oxidative stress in patients with type 2 diabetes mellitus: A systematic review and meta-analysis. Complement Ther Med. 46: 210-216
    12. Almatroodi SA, Almatroudi A, Khan AA, et al. (2020) Potential Therapeutic Targets of Epigallocatechin Gallate (EGCG), the Most Abundant Catechin in Green Tea, and Its Role in the Therapy of Various Types of Cancer. Molecules. 25(14): E3146
    13. Hu J, Webster D, Cao J, Shao A. (2018) The safety of green tea and green tea extract consumption in adults – Results of a systematic review. Regul Toxicol Pharmacol. 95: 412-433

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Aromatic
An ‘aromatic’ remedy, high in volatile essential oils, was most often associated with calming and sometimes ‘warming’ the digestion. Most kitchen spices and herbs have this quality: they were used both as flavouring and to ease the digestion of sometimes challenging pre-industrial foods. Many aromatics are classed as ‘carminatives’ and are used to reduce colic, bloating and agitated digestion.They also often feature in respiratory remedies for colds, chest and other airway infections. They are also classic calming inhalants and massage oils, and are the basis of aromatherapy for their mental benefits.
Astringent
The astringent taste you get with many plants (the most familiar is black tea after being stewed too long, or some red wines) is produced by complex polyphenols such as tannins. Tannins are used in concentrated form (eg from oak bark) to make leather from animal skins. The process of ‘tanning’ involves the coagulation of relatively fluid proteins in living tissues into tight clotted fibres (similar to the process of boiling an egg). Tannins in effect turn exposed surfaces on the body into leather. In the case of the lining of mouth and upper digestive tract this is only temporary as new mucosa are replenished, but in the meantime can calm inflamed or irritated surfaces. In the case of open wounds tannins can be a life-saver – when strong (as in the bark of broadleaved trees) they can seal a damaged surface.One group of tannins, the reddish-brown ‘condensed tannins’ are procyanidins, which can reduce inflammation and oxidative damage.
Bitter
Bitters are a very complex group of phytochemicals that stimulate the bitter receptors in the mouth. They were some of the most valuable remedies in ancient medicine. They were experienced as stimulating appetite and switching on a wide range of key digestive functions, including increasing bile clearance from the liver (as bile is a key factor in bowel health this can be translated into improving bowel functions and the microbiome). Many of these reputations are being supported by new research on the role of bitter receptors in the mouth and elsewhere round the body.Bitters were also seen as ‘cooling’ reducing the intensity of some fevers and inflammatory diseases.
Cooling
Traditional ‘cold’ or cooling’ remedies often contain bitter phytonutrients such a iridoids (gentian), sesiquterpenes (chamomile), anthraquinones (rhubarb root), mucilages (marshmallow), some alkaloids and flavonoids. They tend to influence the digestive system, liver and kidneys. Cooling herbs do just that; they diffuse, drain and clear heat from areas of inflammation, redness and irritation. Sweet, bitter and astringent herbs tend to be cooling.
Hot
Traditional ‘hot’ or ‘heating’ remedies, often containing spice ingredients like capsaicin, the gingerols (ginger), piperine (black or long pepper), curcumin (turmeric) or the sulfurous isothiocyanates from mustard, horseradich or wasabi, generate warmth when taken. In modern times this might translate as thermogenic and circulatory stimulant effects. There is evidence of improved tissue blood flow with such remedies: this would lead to a reduction in build-up of metabolites and tissue damage.Heating remedies were used to counter the impact of cold, reducing any symptoms made worse in the cold..
Mucilaginous
Mucilages are complex carbohydrate based plant constituents with a slimy or ‘unctuous’ feel especially when chewed or macerated in water. Their effect is due simply to their physical coating exposed surfaces. From prehistory they were most often used as wound remedies for their soothing and healing effects on damaged tissues. Nowadays they are used more for these effects on the digestive lining, from the throat to the stomach, where they can relieve irritation and inflammation such as pharyngitis and gastritis. Some of the prominent mucilaginous remedies like slippery elm, aloe vera and the seaweeds can be used as physical buffers to reduce the harm and pain caused by reflux of excess stomach acid.Mucilages are also widely used to reduce dry coughing. Here the effect seems to be by reflex through embryonic nerve connections: reduced signals from the upper digestive wall appear to translate as reduced activity of airway muscles and increased activity of airway mucus cells.Some seed mucilages, such as in psyllium seed, flaxseed (linseed) or guar bean survive digestion to provide bulking laxative effects in the bowel. These can also reduce rate of absorption of sugar and cholesterol..
Pungent
The pungent flavour refers to the powerful taste of hot spices including mustard (Brassica spp.), ginger (Zingiber officinale), horseradish (Amoracia rusticana), chilli (Capsicum spp.), and garlic (Allium sativum). These herbs act to enliven and invigorate the senses, and they often also have heating qualities. Unlike other tastes, the effect is not linked to a specific receptor on the tongue and instead acts through direct irritation of tissues and nerve endings. Energetically, pungent herbs are known to disperse energy (qi) throughout the body. Pharmacologically, pungent herbs dry excess moisture and mucus, as well as stimulate digestion and metabolism.
Resinous
Resins are most familiar as tacky discharges from pine trees (and as the substance in amber, and rosin for violin bows). They were most valued however as the basis of ancient commodities like frankincense and myrrh (two of the three gifts of the Three Wise Men to the baby Jesus) and getting access to their source was one benefit to Solomon for marrying the Queen of Sheba (now Ethiopia). Resins were the original antiseptic remedies, ground and applied as powders or pastes to wounds or inflamed tissues, and were also used for mummification.With alcohol distillation it was found that they could be dissolved in 90% alcohol and in this form they remain a most powerful mouthwash and gargle, for infected sore throats and gum disease. They never attracted much early research interest because they permanently coat expensive glassware! For use in the mouth, gums and throat hey are best combined with concentrated licorice extracts to keep the resins in suspension and add extra soothing properties. It appears that they work both as local antiseptics and by stimulating white blood cell activity under the mucosal surface. They feel extremely effective!
Salty
The salty flavour is immediately distinctive. A grain dropped onto the tongue is instantly moistening and a sprinkle on food enkindles digestion. This easily recognisable flavour has its receptors right at the front of the tongue. The salty flavor creates moisture and heat, a sinking and heavy effect which is very grounding for the nervous system and encourages stability. People who are solid and reliable become known as ‘the salt of the earth'.
Sharpness
The sharp taste of some fruits, and almost all unripe fruits, as well as vinegar and fermented foods, is produced by weak acids (the taste is generated by H+ ions from acids stimulating the sour taste buds). Sour taste buds are hard-wired to generate immediate reflex responses elsewhere in the body. Anyone who likes the refreshing taste of lemon or other citrus in the morning will know that one reflex effect is increased saliva production.Other effects are subjective rather than confirmed by research but there is a consistent view that they include increased digestive activity and contraction of the gallbladder.
Sour
The sour taste occurs because of the stimulation of hydrogen ions which trigger the sour taste receptors on the tongue. The more acidic a substance, the more hydrogen ions will be released. The sour taste comes from acidic substances including citrus, fermented foods, tannins, and vinegars. Sour foods and herbs absorb excess moisture, whilst also increasing the production of saliva. Energetically, sour substances tonify the lungs, playing a role in disease prevention. Excessive use, however, can result in malabsorption of nutrients. Examples of sour herbs include, rosehips (Rosa canina), raspberry (Rubus idaeus), rhubarb (Rheum palmatum), schisandra (Schisandra chinensis), hawthorn (Crataegus monogyna) and ginkgo (Ginkgo biloba).
Sweet
In the days when most people never tasted sugar, ‘sweetness’ was associated with the taste of basic foods: that of cooked vegetables, cereals and meat. In other words sweet was the quality of nourishment, and ‘tonic’ remedies. Describing a remedy as sweet generally led to that remedy being used in convalescence or recovery from illness.Interestingly, the plant constituents most often found in classic tonics like licorice, ginseng are plant steroids including saponins, which also have a sweet taste.
Umami
The umami taste was originally discovered in 1985 in Japan and is directly translated from the Japanese as a ‘pleasant savoury taste’. It is referred to as the ‘fifth taste’ and is a salty, rich, and meaty flavour. The umami flavour is produced by amino acids (glutamic acid and aspartic acid) found in many food and plant sources including tomatoes, mushrooms, seaweeds and soy-based foods. Umami foods can improve nutritional absorption and digestion as there are also umami receptors in the gut as well as the mouth. Examples of umami herbs include green tea (Camellia sinensis), reishi (Ganoderma lucidum), nettle (Urtica dioica), cordyceps (Ophiocordyceps sinensis), shitake (Lentinula edodes) and bladderwrack (Fucus vesiculosus).

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