Green Tea

Synonym(s): EGCG, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, green tea

Nutrient group: plant extracts & active ingredients

Sources and physiological effects

Dietary sources
Green tea originally comes from China, where it was first mentioned about 4700 years ago. Since then, geen tea has not only reached the West as a popular drink, its leaf extract is also one of the most intensively researched phytotherapeutics.
Physiological effects
Metabolism	Metabolic stimulation by inhibition of norepinephrine degradation Stimulation of thermogenesis and oxidation of fatty acids
Antioxidant	As antioxidant protection against UV-induced damage

Detailed information

Green tea components

Green tea and its main components polyphenols, catechins and epigallocatechin gallate (EGG) are currently among the most intensively researched phytotherapeutics. The use of green tea extract in the adjuvant treatment of obesity and for stimulating the metabolism is now well documented and the preventive effects are continually confirmed by epidemiological studies.

Stimulation of metabolism and thermogenesis in weight control

Green tea is one of the few scientifically proven active ingredients used in the treatment of obesity. The polyphenols contained in green tea are effective independently of caffeine, which can also be used in this indication area. The catechins epicatechin, epicatechin gallate and the most pharmacologically active epigallocatechin gallate (EGCG) are described as essential active components. Catechins are sympathomimetic agents that activate the metabolism by inhibiting the breakdown of noradrenaline.¹ Catechins increase energy consumption by stimulating the thermogenesis and oxidation of fatty acids. Numerous studies have shown a reduction in body weight and body fat through green tea and its components.² An additional daily intake of 580 mg and 96 mg catechins in overweight diabetics over3 month showed a significant reduction in hip circumference compared to the control group.³ Catechins also play an important role in maintaining body weight after weight reduction diets (anti-yo-yo effect). EGCG can inhibit the increased adipogenesis in tissue at the cellular level, which usually occurs after weight reduction.⁴ This also seems to be due to an influence on gene expression, which leads to a reduced build-up of fatty tissue as well as to increased fat oxidation and thermogenesis.⁵ In general, however, it can be assumed that green tea extract supports and accompanies weight reduction diets and obesity therapies, but is not sufficient as a sole measure for reducing obesity.

EGCG for protection against early aging and UV-induced damage

Phenols are some of the strongest antioxidants among secondary plant substances. In this group, green tea epigallocatechin gallate is at the forefront.⁶ EGCG is an essential antioxidant for the epidermis and underlying tissue structures and protects the skin from UV damage. Polyphenols and catechins are particularly important for the preservation of skin properties and skin functions⁶ as well as for the prevention of UV-induced DNA damage to skin cells. Regular supplementation improves UV tolerance, reduces sunburn intensity and improves skin functions after intensive UV exposure.⁷ Clinical studies also show photoprotective effects on peripheral blood cells after UV exposure and epigallocatechin gallate supplementation.⁸

Green tea extract, the antioxidant alternative for smokers

The mutagenic, carcinogenic and degenerative properties of nicotine and cigarette smoke can be partly explained by the increased oxidative stress to which smokers are exposed. Green tea polyphenols appear to be suitable for strengthening antioxidant protection systems because they also have strong inhibitory effects on the carcinogenic potential of nicotine⁹ and can attenuate inflammatory processes in smoke-induced emphysema.¹⁰ Lunge tissue is especially protected by EGCG supplementation.¹¹ An intervention study in smokers showed that regular high consumption of green tea leads to a reduction in oxidative damage and thus provides protection against diseases caused by increased oxidative stress from smoking and nicotine.¹²

Strong antioxidant protection against free radical-associated diseases

Various clinical studies have shown the positive effects of green tea extracts in radical-associated diseases. The neuroprotective mechanisms underlying the use of green tea phenols in Alzheimer's and Parkinson's disease are ultimately caused by the reduction of oxidative damage.¹³ Inhibition of nitrosative stress also seems to be important for the neuroprotective properties of EGCG. EGCG suppresses the formation of peroxynitrites which have strong cytotoxic properties.¹⁴ Studies also show a close correlation between the regular intake of green tea polyphenols and a reduced incidence of cardiovascular diseases¹⁵ as well as a general positive effect on the oxidative capacity of body fluids.¹⁶

Green tea polyphenols and their positive effects on the gut flora

Polyphenols, which are also abundant in green tea, have anti-inflammatory properties, as also shown by a study in connection with the gut microbiota. According to this, the administration of a polyphenol-rich diet (including green tea) led to a change in the intestinal flora and to an increase in the metabolite indole-3-propionic acid, which has antioxidant, anti-inflammatory and neuroprotective properties, with a simultaneous decrease in inflammation levels.¹⁷

Reference values

Nutrigenetics
Characteristic gene sites and their effects on vitamin requirements

Gene	rsNumber	risk SNP	Description	Recommended nutrients
COMT	rs4633	T	Labeled the warrior gene. Reduced degradation of catecholamines such as dopamine and estrogen, more sensitive to the intake of green tea and Cannabidiol.	Green Tea, CBD

Indications

Effect	Indication	Dosage
Physiological effects at a low intake	For general preventive use	300 - 400 mg/d
	Complementary thearpy for weight control, in obesity therapy and to reduce the yo-yo effect of dieting	1000 – 1500 mg/d
	To stimulate metabolism in states of metabolic imbalance	1000 – 1500 mg/d
	To improve antioxidant status and treat oxidative stress, especially in smokers	1000 – 1500 mg/d
	To improve skin appearance, to protect against UV-related skin aging and to maintain skin functions after UV exposure	1000 – 1500 mg/d

Administration

General mode of administration
When	Green tea should be taken between meals to avoid affecting the absorption of other minerals.
Side effects
Green tea contains natural tannins, which can lead to reversible gastrointestinal complaints (nausea) in sensitive persons. Hint: Green tea extract is decaffeinated and therefore does not cause any caffeine-associated side effects.
Contraindications
No contraindications are known to date.

Interactions

Drug interactions
None	No relevant interactions are known to date.
Nutrient interactions
Trace elements	The absorption of iron is inhibited with simultaneous ingestion of green tea.

References

¹ Dulloo. A. G. et al. 2000. Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity. Int J Obes Relat Metab Disord. 24(2):252-8.
² Hursel, R. et al. 2009. The effects of green tea on weight loss and weight maintenance: a meta-analysis. Int J Obes (Lond).
³ Nagao, T. et al. 2009. A catechin-rich beverage improves obesity and blood glucose control in patients with type 2 diabetes. Obesity (Silver Spring). 17(2):310-7.
⁴ Diepvens, K. et al. 2007. Obesity and thermogenesis related to the consumption of caffeine, ephedrine, capsaicin, and green tea. Am J Physiol Regul Integr Comp Physiol.
⁵ Lee, M. S. et al. 2009. Green tea (-)-epigallocatechin-3-gallate reduces body weight with regulation of multiple genes expression in adipose tissue of diet-induced obese mice. Ann Nutr Metab. 54(2):151-7
⁶ Watzl, B., Leitzmann, C. 1999. Bioaktive Substanzen in Lebensmitteln.
⁷ Jeon, H. Y. et al. 2009. Effects of oral epigallocatechin gallate supplementation on the minimal erythema dose and UV-induced skin damage. Skin Pharmacol Physiol. 22(3):137-41.
⁸ Morley, N. et al. 2005. The green tea polyphenol epigallocatechin gallate and green tea can protect human cellular DNA from ultraviolet and visible radiation-induced damage. Photodermatol Photoimmunol Photomed. 21(1):15-22.
⁹ Santhosh, K. T. et al. 2005. Potent suppressive effect of green tea polyphenols on tobaccoinduced mutagenitiy. Phytomedicine 12(3):216-20.
¹⁰ March, T. H. et al. 2006. Modulators of cigarette smoke-induced pulmonary emphysema in A/J mice. Toxicol.
¹¹ Chan, K. H. et al. 2009. Chinese green tea ameliorates lung injury in cigarette smoke-exposed rats. Respir Med.
¹² Hakim, I. et al. 2003. Effect of increased tea consumption on oxidative DNA damage among smokers: a randomized controlled study. J Nutr. 133(10):3303S-9S.
¹³ Weinreb, O. et al. 2004. Neurological mechanisms of green tea polyphenols in Alzheimer’s and Parkinson’s diseases. J Nutr Biochem.15(9):506-16.
¹⁴ Kim, C. Y. et al. 2009. Neuroprotective effect of epigallocatechin-3-gallate against beta-amyloidinduced oxidative and nitrosative cell death via augmentation of antioxidant defense capacity. Arch Pharm Res. 32(6):869-81.
¹⁵ Kuriyama, S. 2008. The relation between green tea consumption and cardiovascular disease as evidenced by epidemiological studies. J Nutr. 138(8):1548S-1553S.
¹⁶ Peluso, I., and Serafini, M. 2016. Antioxidants from black and green tea: from dietary modulation of oxidative stress to pharmacological mechanisms. British Journal of Pharmacology.
¹⁷ Peron, G. et al. 2022. A Polyphenol-Rich Diet Increases the Gut Microbiota Metabolite Indole 3-Propionic Acid in Older Adults with Preserved Kidney Function. Mol Nutr Food Res. e2100349.

References Interactions
Stargrove, M. B. et al. Herb, Nutrient and Drug Interactions: Clinical Implications and Therapeutic Strategies, 1. Auflage. St. Louis, Missouri: Elsevier Health Sciences, 2008.
Gröber, U. Mikronährstoffe: Metabolic Tuning –Prävention –Therapie, 3. Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2011.
Gröber, U. Arzneimittel und Mikronährstoffe: Medikationsorientierte Supplementierung, 3. aktualisierte und erweiterte Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2014.