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Green tea is a type of tea that is made from Camellia sinensis leaves that have not undergone the same withering and oxidation process used to make oolong teas and black teas.[rx] Green tea originated in China, but its production and manufacture have spread to many other countries in Asia. The normal black tea is obtained by fermenting the tea leaves. This changes its color and flavor while raising the level of caffeine and tannin in it. On the other hand, in the case of green tea, the tea leaves are dried or slightly steamed but not fermented. This is what makes it look green when it’s brewed.
Types of Green Tea
Green tea has four main varieties prepared in Japan, which depend upon its leaf-length, method of processing, and season of harvesting. They are as follows;
Gyokurocha – In this variety, the tea leaves are plucked from the tip of the branches. When brewed, the color is clear green. Being picked from the tip, this variety has the best taste and fragrance, and this variety is also considered the best in terms of health. Furthermore, it is less bitter, as it contains lesser tannin and caffeine since the plucked leaves are younger and still budding. The only drawback to gyokurocha is the high cost, but as we all know, truly high-quality solutions for health never come cheap![rx]
Sencha – Sencha comes from the same plant, but in this green tea variation, the leaves are from the middle of the branch and are bigger, older, and less tender than Gyokurocha. This variety gives a clear, light green tea when brewed as well. Naturally, it is more bitter and stronger than the former variety. Being of less noble origin (middle of the branch) and having more caffeine and tannin, it is cheaper and more popular than Gyokurocha.
Bancha – Bancha is made from the tender twigs of the tea plant which makes it very strong and bitter. When brewed, it gives a golden brown tea. This is an even cheaper version of green tea than the previous two.
Matcha – This is the leftover powder of green tea, also called “Dust”. It makes a beautifully green-colored tea and forms a lot of foam (froth), but has a weaker aroma than the leafy varieties. This variety of green tea is very popular in traditional ceremonies and is sometimes also called Ceremonial Green Tea. It is far less bitter than the other three varieties, so when you sip it, it seems to hold a natural sweetness, particularly if you are familiar with the other varieties.
Houjicha – Also spelled as “Hojicha”, this is not a pure or absolute green tea. Rather, it is a mixture of green tea and powdered roasted cereals such as wheat, barley, or rice. The quality and price of this variety depend upon the percentage or ratio of green tea to cereal content. The better ones, which have more green tea in them, are more expensive and have a greener look when brewed; on the other hand, those with higher grain contents yield a golden brown color and are cheaper.
Genmaicha – Like Houjicha, this is not a pure tea either. It is a mixture of green tea and roasted brown rice. Upon steeping, it yields a golden yellow tea, very pleasant in both taste and aroma due to the presence of roasted brown rice.
Decaffeinated Green Tea – This is not a specific variety, but it is worth mentioning here. Any of the above varieties can come in aform.
Other Varieties – The chief varieties mentioned above are blended in different combinations to produce much more varieties with different names, the number of which makes it pointless to list here. Basically, go to a tea shop and explore for yourself!
|Protein||Peptides and enzymes|
|Carbohydrates||Fructose, sucrose, cellulose, pectin, and glucose|
|Vitamins||Vitamins (B, C, and E)|
|Xanthic bases||Caffeine, Theophylline|
|Minerals and trace elements||Calcium, Magnesium, Sodium, Chromium, Manganese, Copper, Cobalt, Nickel, Iron, Molybdenum, Selenium, Phosphorus, Potassium, Fluoride, Zinc, Aluminum|
|Nutritional value per 100 g (3.5 oz)|
|Energy||4 kJ (0.96 kcal)|
|†Percentages are roughly approximated using US recommendations for adults.|
Health Benefits of Green Tea
- Excellent Antioxidants – Polyphenols have shown anti-oxidative activity by neutralization of free radicals in the body. They are also known to reduce or prevent their detrimental effects and restrain ROS generation to inhibit the lysosomal secretions. The hydrogen releasing property of catechin and epicatechin results in scavenging effects . Polyphenols have following processes that reduce oxidation level . Antioxidant capacity of human plasma, measured by the TEAC assay, was enhanced to a greater extent (1.4 %) by consumption of green tea polyphenols (461.9 mg/d) in tablet form compared to a green tea beverage (697.1 mg/d) , suggesting tablets may be an effective way to enhance plasma antioxidant capacity by green tea polyphenols. This difference may be due to pharmacokinetic differences in the delivery of polyphenols by tablet compared to the beverage. Polyphenols in beverage may be ingested and absorbed more slowly than in a tablet. The elevation in antioxidant power of human plasma could be the basis for a role of green tea in cancer preventive effects, yet the effects are likely to be due mainly to metabolites of green tea polyphenols [7–8].
- Works as An A-cancer – Much attention has been paid to the anti-cancer activity of green tea and tea catechins with animal and cell experiments. In 1993, we reported that EGCG, the major catechins in green tea, inhibited the adhesion of cancer cells to endothelial cell layers. We also found that EGCG prevented cancer cells from attaching to fibronectin and laminin two components of the endothelial basement membrane.[12 ]These findings suggested green tea to have an anti-metastatic effect. Indeed, we found that a green tea infusion was effective at preventing cancer cell metastasis using in vivo and in vitro models. The peroral administration of green tea infusion reduced the number of lung colonies of mouse Lewis lung carcinoma cells in a spontaneous metastasis system. The experiments with artificially reconstituted basement membrane indicated that the green tea infusion and its constituent catechins prevented cancer cells from the penetration through the basement membrane. These findings were consistent with those of Taniguchi et al. who reported that EGCG inhibited lung metastasis in mouse B16 melanoma cell lines.
- Anti-inflammatory Effect – It is now recognized that atherosclerosis is a chronic inflammatory disease and inflammation-induced monocyte adhesion to ECs followed by transmigration into the subendothelial space is one of the key events in the development of atherosclerosis [14,15]. Adhesion of leukocytes to ECs is critically regulated by both chemotactic cytokines and vascular adhesion molecules. Chemokine interleukin-8 (IL-8) and monocyte chemoattractant protein -1 (MCP-1) are demonstrated to be the key factors in the firm adhesion of monocytes to activated ECs and in monocyte recruitment into the sub-endothelial lesion in atherosclerosis . Various adhesion molecules that are involved in this event such as endothelial leukocyte adhesion molecule-1 (E-selectin), intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1), which are regulated by NF-kB and play a pivotal role in attracting binding and transmigration of leukocytes into sites of inflammation [17, 18].
- Best for Skin Health – Summary of effects of green tea polyphenols on the skin.
|GTPP protective effect||Cellular and/molecular response||References|
|UV protection||Inhibits UVB-induced MAPK activation and phosphorylation of ERK1/2, JNK and p38.|||
|Attenuates nuclear transcription factors, c-Jun p53, and c-for|
|Antioxidant||Free radical scavenging activity|||
|Inhibits NOS, H2O2 production|
|Prevents UVB-induced depletion of antioxidant enzymes: catalase, glutathione peroxidase, superoxide dismutase, and glutathione|
|Inhibits UVB-induced LPO and protein oxidation|
|Anti-inflammation||Prevents UV-induced depletion of CD1a + LC and APC Inhibits UV-induced infiltration of monocytes, macrophages, neutrophils|||
|Protects UVB-induced immunosuppression via IL-12 production|
|↓ in histamine release by mast cells|
|Anticarcinogenesis||Inhibits DNA damage.|||
|Inhibits UV-induced CPD, 8-OHdG formation|
|DNA repair enzyme activation|
|Modulates transcriptions factors AP1, NFKB|
|Inhibits tumor growth, progression, and angiogenesis|
LC: Langerhans cells; LPO: lipid peroxidase; MAPK: mitogen-activated protein kinase; NOS: nitric oxide synthase.
- Therapeutic Effects on Periodontal and Gingival Health – The gingival crevice is a physiological zone surrounded by gingiva and tooth margins. A colony of microorganisms resides in this space and most common of that are anaerobes. In pathological conditions, these spaces extend and periodontal pockets filled with serum exudates and large colonies of polymorphs. Additionally, oxidative stress supports the development of diseased conditions. The microbes commonly present in such conditions are Prevotella spp and Porphyromonas gingivalis (black pigmented anaerobes) . Periodontal health is inversely related to consumption of green tea, an epidemiological study proves that people have better periodontal health if they drink green tea very often for example during meals or at breaks from work . Green tea plays a supportive role in the maintenance of periodontal health, as suggested by an in vitro study catechins (e.g. EGCG) restrict the development and colonization of harmful bacteria such as Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens . These bacteria cause severe harm to periodontal tissues for example Porphyromonas gingivalis develop adhesion to buccal mucosa and cause destruction . Recently, Nadeem et al.  studied the influence of green tea consumption versus black tea on periodontal health of 240 dental students and noticed that students who were consuming green tea had good periodontal health status with minimal plaque accumulation in comparison with consumers of black tea. Literature exhibited that better periodontal health status of regular green tea using individuals is mainly due to catechins, as these are steric structures of 3-galloyl radial, ECG, EGCG and gallocatechin gallate (GCG) (major polyphenols) and responsible for restrain release of toxic end metabolites from Porphyromonas gingivalis .
- Lowering Your Risk of Alzheimer’s and Parkinson’s – Not only can green tea improve brain function in the short term, but it may also protect your brain in old age. Alzheimer’s disease is the most common neurodegenerative disease in humans and a leading cause of dementia. Parkinson’s disease is the second most common neurodegenerative disease and involves the death of dopamine-producing neurons in the brain. Multiple studies show that the catechin compounds in green tea can have various protective effects on neurons in test tubes and animal models, potentially lowering the risk of Alzheimer’s and Parkinson’s [29, 30].
- Help in Dental Caries – Dental carries is a pathological condition resulting due to demineralization of tooth structure because of bacterial infections and/or deficiency of nutrients. Oral microbes are responsible for carries development, out of which mainly streptococcus mutants are most active . The oral antimicrobial peptides are known to reduce the bacterial activity . Green tea leaves are known to be rich in fluoride and other components such as polyphenols (catechins) that play a supportive role in resisting dental carried as reported in many studies [33, 34]. The beneficial role of fluoride is well known as it inhibits the bacterial growth and helps re-mineralization of dental tissues [,35]. Cariogenic bacteria release glucans with the help of glucosyltransferase (GTase) which are branched and facilitate adherence of microbes to tooth surface . GC and EGC are the catechins that restrict the growth of 10 types of carries causing bacteria. Otake et al.  showed that total amount of catechins, mainly EGCG and its epimer gallocatechin, EC and ECG present in one cup of green tea prevent streptococcus mutants from adhering to tooth surfaces. The catechins were extracted from green tea with concentration of 100mg/L and their effects on bacterial adhesion to salivary coated hydroxyapatites were observed. Other studies also exhibit that consumption of tea constrains the release of the salivary enzyme, amylase as observed by Kashket and Paolino . Later it was supported by Zhang and Kashket  proving that tea, either black or green restrains the enzymatic activity of Streptococcus mutans’ amylase on tooth structure preventing deminerlization.
- Bad Breath (halitosis) Reducer – The main reagents responsible for halitosis (bad breath) are volatile sulfide compounds such as hydrogen sulfide (H2S), dimethylsulfide [(CH3)2S] and methyl mercaptan (CH3SH). These reagents degrade in the oral cavity by proteolytic reactions primarily by anaerobic gram negative bacteria consuming numerous sulfur-containing substrates including saliva, food debris, epithelial cells and blood . Green tea is well known for antibacterial properties against anaerobic microorganisms. Green tea can abolish bad breath by suppressing anaerobic bacteria and eliminating the production of volatile sulfur compounds . Deodorant action of ingredients decreases in the following order: EGCG > EGC > ECG > EC. The deodorizing action of EGCG is based on a chemical reaction of EGCG and MSH and introducing methylsulfinyl/methylthio group into the B ring of EGCG. During this reaction, a methylthio group is supplemented in the orthoquinone form of the catechin produced by oxidation, hence eliminating the halitosis .
- Anti-Platelet Activity and Anti-Thrombotic Effect – Platelet activation and aggregation also play an integral role in the development of CVD. The alterations in platelet sensitivity and platelets-vessel wall interaction are associated with the development of cardiovascular events. In the presence of vascular endothelial injury, platelets rapidly aggregate to form hemostatic plugs and arterial thrombi which could trigger the acute vascular events such as myocardial infarction . Indeed, there is extensive evidence that anti-platelet therapy can reduce CVD risk .
- Cure Fever – The effectiveness of green tea in treating any type of diarrhea and typhoid has been known in Asia since ancient times [44–45]. Green tea catechins have an inhibitory effect on Helicobacter pylori infection [46,47]. Effects of green tea against the influenza virus, especially in its earliest stage, as well as against the Herpes simplex virus have also been demonstrated . Furthermore, Weber et al.  observed that adenovirus infection is inhibited in vitro by green tea catechins.
- Cigarette Smoke Induced Inflammation – Smoking affects the homeostasis and injurious to oral health . The effects of smoking range from simple mucosal erythema to premalignant conditions and oral cancer. Smoking intensifies oral malignancies in response to oral inflammatory diseases due to the compromised status of salivary antioxidants . Diminished activity of numerous salivary enzymes is observed during smoking hence compromising the protection against oxidative damage . In addition, smoke coming from tobacco comprised of reactive oxygen species (ROS) including superoxides, hydroxyl radical/hydrogen peroxide. The toxicity is further added due to the formation of nitric oxide (NO). Superoxide reacts chemically with NO to form peroxynitrite (ONOO). The inflammatory transcription factor pathway (NFkB) is triggered by ONOO due to activation of IkB kinase (IKK). The cascade of changes results in the intensification of expressions, iNOS activity and chronic inflammation in tissues even by exposing to a very minute dose of smoke 
- Help in Smoking Cessation – Catechins present in green tea is capable of scavenging superoxide oxide, NO, and ONOO [54, 55]. In addition, EGCG has the ability to suppress activation of NF-kB that leads to inhibition of phosphorylation. It can further trigger the collapse of the inhibitory sections IkB-a in human pulp cells. The IkBa is also accountable for overturning nuclear transfer of NF-kB operating subunits (p65 and p50) and stimulation of pro-inflammatory genes [56, 57]. EGCG resulted in decreased NF-kB expression and reduction of proteins facilitated including matrix metalloproteinase9 (MMP-9). The MMP-9 is implicated in the breakdown of extracellular matrix, nterleukin-8 (IL-8) and iNOS present in bronchial epithelium . There are more than 4700 oxygen/nitrogen species and reactive chemical compounds in the cigarette smoke. Nicotine is the main chemical compound released from cigarettes that affects gingival and periodontal health . Nicotine stimulates apoptosis across ROS generations of human gingival fibroblasts (HuGF) . The metabolites of nicotine such as tobacco-specific nitrosamines (TSNAs) are considered major carcinogens.
- Anti-allergenic agents – Leukaemia cells are sustained in part by secreting a small protein molecule called vascular endothelial growth factor (VEGF). This binds to protein receptors embedded in the membrane of the leukemia cells and can promote the resistance to cell death typical of this type of cancer.[
- Green Tea Can Improve Brain Function and Make You Smarter – Green tea does more than just keep you awake, it can also make you smarter. The key active ingredient is caffeine, which is a known stimulant. It doesn’t contain as much as coffee, but enough to produce a response without causing the “jittery” effects associated with too much caffeine. What caffeine does in the brain is to block an inhibitory neurotransmitter called Adenosine. This way, it actually increases the firing of neurons and the concentration of neurotransmitters like dopamine and norepinephrine [61, 62]. Caffeine has been intensively studied before and consistently leads to improvements in various aspects of brain function, including improved mood, vigilance, reaction time and memory . However, green tea contains more than just caffeine. It also has the amino acid L-theanine, which is able to cross the blood-brain barrier . L-theanine increases the activity of the inhibitory neurotransmitter GABA, which has anti-anxiety effects. It also increases dopamine and the production of alpha waves in the brain . Studies show that caffeine and L-theanine can have synergistic effects. The combination of the two is particularly potent at improving brain function [66, 67].
- Fat Burning and Improves Physical Performance – If you look at the ingredients list for any fat burning supplement, chances are that green tea will be on there. This is because green tea has been shown to increase fat burning and boost the metabolic rate, in human controlled trials [68, 69].In one study in 10 healthy men, green tea increased energy expenditure by 4% . Another study showed that fat oxidation was increased by 17%, indicating that green tea may selectively increase the burning of fat (. However, some studies on green tea don’t show any increase in metabolism, so the effects may depend on the individual . Caffeine itself has also been shown to improve physical performance by mobilizing fatty acids from the fat tissues and making them available for use as energy [73, 74]. In two separate review studies, caffeine has been shown to increase physical performance by 11-12%, on average [ 75].
- Effect on Obesity – The effects of tea on obesity and diabetes have received increasing attention. Tea catechins, especially EGCG, appear to have antiobesity and antidiabetic effects . African black tea extract has been shown to suppress the elevation of blood glucose during food intake and reduce the body weight in KK-A(y)/TaJcl diabetic mice . Although few epidemiological and clinical studies have shown the health benefits of EGCG on obesity and diabetes, the mechanisms of its actions are emerging based on various laboratory data. These mechanisms may be related to certain pathways, such as through the modulations of energy balance, endocrine systems, food intake, lipid and carbohydrate metabolism, and redox status .
- Anti-atherosclerotic Effects – In the book “Yojokun” published in the Edo period, Ekiken Kaibara described that according to the ancient Chinese medical doctor, long-term drinking of green tea would result in a lean body by removing body fat. Evidence has accumulated to show that the ingestion of green tea and tea catechins leads to a reduction in body fat as described in recent reviews. The stimulation of hepatic lipid metabolism might be a factor responsible for the anti-obesity effects of tea catechins. Tea catechins are suggested to inhibit cell growth by suppressing lipogenesis in human MCF-7 breast cancer cells through down-regulation of fatty acid synthase gene expression in the nucleus and stimulation of cell energy expenditure in the mitochondria.The experimental data indicated that the suppression of fatty acid synthase gene expression by tea polyphenols may lead to down-regulation of signal transduction.