Health benefits of green tea
[Aticle translated by Google – Google Translate]
It is known that green tea has pleiotropic, pro-health, antioxidant properties.  The main active substances contained in green tea include EGCG, caffeine and l-theanine. Their combination results in a harmonious, stable stimulation after ingestion of the infusion. Epigallocatechin gallate (EGCG) is a compound from the flavonoid group, a plant-derived polyphenol, a catechin derivative. It occurs in a significant amount in green tea where it accounts for up to 1/3 of the dry matter.
The following benefits related to the consumption of green tea and its substances have been identified:
- It supports the brain through EGCG antioxidative activity, increasing cognitive abilities, relaxing the effects of l-theanine and stimulating the properties of caffeine. [6, 7, 8, 9, 10, 11] L-theanine is an amino acid contained in green tea. It increases the alpha brain waves responsible for calmness, relaxation and calmness. It is a weak antagonist of NMDA receptors, AMPA and kainate , it can inhibit synaptic release of glutamate, affect the level of GABA neurotransmitters, serotonin and dopamine and activate mRNA for neurotrophins.  In another post, I will break down the use of l-theanine itself as a dietary supplement.
- It works anti-cancer by launching a wide range of mechanisms – it is related to the antioxidant effect of these polyphenols. It reduces the risk of cancer in people with excessive oxidative stress [2, 3, 4, 5]. It is an inhibitor of DNMT [51, 52, 53] (DNA n-methyltransferase) which can inhibit tumor growth by blocking DNA hypermethylation. EGCG has epigenetic functions in chromosomes. Abnormal methylation of CpG islands causes “silencing” of genes which leads to changes in gene proliferation and their physiology. EGCG slows down DNMT – it should be remembered, however, that the deficiency of methyl groups may also be a factor in neoplasia and developmental disorders.
- Polyphenols contained in green tea protect neurons in Alzheimer’s and Parkinson’s disease 
- It shows strongly anti-inflammatory and anti-aging effects through the increase of nitric oxide, inhibition of angiotensin II, IL-6, IL-8 and IL-12. EGCG can be helpful in inflammatory, rheumatic and chemo-radiotherapy diseases. It works anti-aging, can prolong life, because it protects against telomere damage [13, 14, 15, 16, 17],
- It lowers blood pressure by increasing eNOS by phosphatidylinositol 3, PKA- and Akt kinases [18, 19, 20, 21]
- Increases insulin sensitivity and consequently lowers the blood sugar level in people with metabolic syndrome [18, 22, 23]
- May help reduce the symptoms of depression [11, 24]
- It is a COMT inhibitor [25, 26] (catecholamine n-methyltransferase), and therefore blocks the degradation of catecholamines dopamine, adrenaline, norepinephrine [25, 26].
- Promotes weight reduction, increases beta-oxidation of fatty acids and reduces appetite [25, 27, 28, 29, 30, 31]
- It shows a bactericidal effect, has the ability to destroy the protective membrane of bacteria [32, 33]
- Reduces the risk of liver disease and non-alcoholic steatosis 
- It has a beneficial effect on osteogenic processes – it reduces the risk of bone diseases, osteoporosis and promotes the preservation of oral cavity and teeth health [35, 36, 37]
- EGCG may be helpful in the prevention of hair loss 
- It has a positive effect on the condition of the skin. Reduces the risk of wrinkles and redness of the skin 
- It has a beneficial effect on the lipid profile, it lowers the level of LDL [40, 41, 42]
The only risk associated with drinking green tea may be symptoms of caffeine overdose and l-theanine [43, 44]. In practice, it is difficult to do this while drinking green tea. This risk occurs when supplementing high doses of the above substances. Both molecules mutually regulate their activity, giving a stable, harmonious stimulation resulting in improved mood, calmness (with vigilance) and increased mental abilities. So a stack of caffeine + l-theanine, ideally in the ratio of 1: 2, is the perfect safe connection for beginners in the world of nootropics. It is worth paying attention to the potential risk of EGCG supplementation with genetically determined COMT enzyme deficiency (COMT ++). Also in a situation where there is a shortage of methyl groups. With excessive COMT activity (catecholamine deficiency) EGCG is even indicated.
I recommend drinking green tea to people who can benefit from the above benefits of the substance contained in it (EGCG, l-theanine, caffeine). You can also supplement the green tea extract or the molecules contained therein separately. It is worth noting, however, that in the case of incompetent supplementation you can lead to potential side effects. Studies in mice treated with high doses of concentrated EGCG showed a correlation with liver damage and a slight decrease in testosterone level , but these studies are not reflected in humans with rational supplementation. EGCG, like many other flavonoids / polyphenols, is a potent inhibitor of topoisomerases [46, 47, 48]. Some chemotherapeutic drugs, e.g. etoposide and doxorubicin, work in a similar way. It can affect DNA. This property may be responsible for the anti-cancer effect. In one epidemiological study, it was found that high consumption of tea by pregnant women is associated with an increased risk of malignant brain tumors in a child  (these results require confirmation as another study did not find a similar relationship ). The attribution of the harmful effects of all flavonoids in food on human fetuses based on in vitro studies is controversial in the scientific community.
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