Green tea’s origin has been traced back to China more than four thousand years ago. It is widely used as a beverage, as well as for its medicinal purposes. Green tea has been claimed to have a range of health benefits, ranging from lowering cholesterol levels to reducing cancer risk, as well as helping to promote digestive health, energy and endurance. Green tea is available in tea, liquid, tablet, and capsule form.
The medicinal parts are the very young downy leaves, from which green or black tea is prepared according to the treatment being given.
Flower and Fruit
The flowers grow short-pedicled and singly or in clusters of a few flowers in the leaf axils. They are white or pale pink and have a diameter of 3 to 5 cm. The flowers have between 5 and 7 sepals and petals at a time. The petals are fused at the base with the numerous stamens. The ovary has 3 chambers. The fruit is a greenish-brown, woody capsule with a diameter of 1 to 1.5 cm and contains 1 to 3 smooth brown seeds.
Leaves, Stem, and Root
The plant is an evergreen, heavily branched shrub. The leaves are glossy dark green, alternate, short-petiolate, coreacious, lanceolate or elongate-ovate, and roughly serrate. The young leaves appear silver because of the covering of downy hairs on the surface.
The plant does not originate in the wild. It was originally cultivated in China and is grown as a tea plant today in India, China, Sri Lanka, Japan, Indonesia, Kenya, Turkey, Pakistan, Malawi, and Argentina.
Tea leaves are the fermented and/or dried leaves of Camellia sinensis. Harvesting takes place under stringent quality control. Green Tea is produced by steaming the fresh-cut leaf. Black Tea is produced by allowing the leaves to oxidize. During oxidation, enzymes present in the tea convert many of the polyphenolic therapeutic substances to less active compounds. Oxidation does not occur with Green Tea because the steaming process inactivates the enzymes responsible for oxidation. The anti-oxidant activity of Green Tea is six times greater than that of Black Tea.
Actions & Pharmacology
Purine alkaloids (methyl xanthines): caffeine (previously referred to as theine or teine; depending upon the development stage of the leaves, 2.9-4.2%, content declining with age), theobromine (0.15-0.2%), theophylline (0.02-0.04%)
Triterpene saponins (theafolia saponins): aglycones including, among others, barringtogenol C, R1-barringenol
Catechins: in unfermented (green) tea 10-25%, with fermentation partially changing over into oligomeric quinones with tannin character, into theaflavine, theaflavin acid, thearubigene, or into non-water soluble polymeric flavonoids including, among others, quercetin, kaempferol, myrecetin
Flavonoids: including quercetin, kaempferol, myricetin
Caffeic acid derivatives: including among others, chlorogenic acid, theogallin
Anorganic ions: high fluoride content (130-160 mg/kg), potassium and aluminum ions
Volatile oil: chief components linalool, in fermented tea also 2-methyl-hept-2-en-6-on, alpha-ionon and beta-ionon, more than 300 volatile compounds are involved in tea aroma
The primary clinical application for Green Tea is in the prevention of cancer and heart disease. Cohort and case-control studies indicate Green Tea exerts anticancer properties on cancers of the gastrointestinal tract, stomach, small intestine, pancreas, colon, lung, and estrogen-related cancers, including most breast cancers. Mouthwashes made with Green Tea have been shown to decrease dental plaque formation and inhibit the growth of caries-producing bacteria (Yamamoto et al, 1997). Green Tea displays thermogenic and fat-oxidizing properties and may thus be a useful adjunct in the treatment of obesity. Green Tea may be helpful in the prevention and treatment of Clostridial diarrhea disease and in helping to promote the growth of “friendly” bacteria (e.g., Lactobacillus and Bidifobacter species) in the gut microflora. Animal studies have demonstrated anti-inflammatory action in the treatment of colitis and cholesterol lowering effects.
The polyphenols in Green Tea are believed to be responsible for the majority of the chemoprotective, antiproliferative, and antioxidant activity of Green Tea. Recent studies on nonpolyphenolic constituents of Green Tea have demonstrated that pheophytins A and B have antigenotoxic and anti-inflammatory activities. Several mechanisms for antiproliferative activity and proapoptotic activity related to cancer and vascular disease chemoprevention have been proposed. The caffeine in the drug has a centrally stimulating and antidepressive effect (adenosine antagonism.) Adenosine antagonism leads to dilation of the renal vessels with a consecutive increase of the rate of filtration (diuresis). Caffeine is positively inotropic, promotes the secretion of gastric juices, glycolysis, and lipolysis. In animal tests, bradykinin and prostaglandin antagonism caused a capillary sealing and anti-inflammatory effect.
Activities of nonpolypyenol constituents in Green Tea
Pheophytins A and B extracted from the nonpolyphenolic fraction of Green Tea demonstrated potent suppressive activity against DNA (Okai & Higashi-Okai, 1997). Pheophytins A and B, extracted from the nonpolyphenolic fraction of Green Tea, demonstrated potent suppressive activity against the activation of polymorphonuclear neutrophils (PMNs) function (Higashi-Okai et al, 1998).
There is clinical evidence that Green Tea has cancer preventative effects. The types of cancer that Green Tea has been shown to prevent as demonstrated in well-controlled clinical studies include cancers of the pancreas, colon, small intestine, stomach, breast, and lung. Several in vitro studies have demonstrated a dose-dependent decreased proliferation and/or increased apoptosis in a variety of cancer cell lines (lung, epidermoid, keratinocyte, prostate, Ehrlich ascites, colon, stomach, oral, and breast). This occurs when exposed to Green Tea polyphenols or the specific polyphenol constituents, epigallocatechin-3-gallate (EGCG) and epigallocatechin (EGC) (Chen et al, 1998; Khafif et al, 1998; Mukhtar, 1998; Kennedy et al, 1998; Khafif et al, 1998a; Yang et al, 1998; Fujiki et al, 1998; Gotoh, 1998; Ahmad et al, 1997).
Other mechanisms of action have been proposed, such as stimulation of transcription of phase II detoxifying enzymes, blockade of growth factor associated signal transduction pathways, inhibition of protein expression of inducible nitric oxide, inhibition of nitric oxide production, and inhibition of activator protein-1 activity (Ahmad & Mukhtar, 1999). Two studies demonstrated that Green Tea caused growth arrest or apoptosis specifically in cancer cells and not in normal cells (Chen et al, 1998; Ahmad et al, 1997). Growth arrest of tumor cells by tea polyphenols occurred during the G1 phase of the cell cycle (Khafif et al, 1998; Khafif et al, 1998a; Ahmad et al, 1997).
Green Tea powder (1 g/kg/d for 4 days, administered orally) enhanced the antitumor activity of the chemotherapeutic agent doxorubicin (DOX) (2 mg/kg/d for 4 days, administered intraperitoneally) in mice transplanted with Ehrlich ascites carcinoma or M5076 ovarian sarcoma cells (Sadzuka et al, 1998). A decrease in total cholesterol, but not triglycerides or HDL, has been associated with drinking 9 cups of Green Tea per day (Kono et al, 1992).
Ethylacetate extracts of Green Tea were potent inhibitors of cavity-associated bacteria such as Escherichia coli, Streptococcus salivarius, and Streptococcus mutans that were isolated from the saliva and dental plaque of carious teeth of cariogenic patients (Rasheed & Haider, 1998). Green Tea had weak inhibitory activity on the growth of Proteus rettgeri and Proteus mirabilis bacteria using a bulk acoustic wave bacterial growth sensor (Yao et al, 1998). Green Tea was demonstrated to be a weak inhibitor of salivary amylase due to tannins and not catechins that are present in the tea (Zhang & Kashket, 1998). Green Tea polyphenols inhibit the growth of Porphyromonas gingivalis and its adherence to oral epithelial cells (Yamamoto et al, 1997).
In vitro pretreatment of cells with the Green Tea extract epigallocatechin gallate significantly inhibited neutrophil adhesion to and migration through endothelial cell monolayers in a dose-dependent manner (p<0.05). Neutrophils play an important part in the inflammatory process. By adhering to the vascular endothelium and migrating into the tissue, invading microorganisms such as bacteria are eliminated (Hofbauer et al, 1999).
Several in vitro studies demonstrate that Green Tea polyphenols and the specific catechins in Green Tea polyphenols, catechin, and epicatechin inhibit LDL oxidation (Lotito & Fraga, 1998; Pearson et al, 1998; Vinson & Babbgh, 1998; Kaneko et al, 1998; Kannar et al, 1997). This activity may help to prevent the development of cardiovascular pathologies, such as atherosclerosis. Two human studies, one in smokers and one in nonsmokers, found no effect of Green Tea consumption (6 cups of Green Tea daily for 4 weeks) on LDL oxidation ex vivo or on plasma levels of antioxidants (vitamins C, E and B-carotene) and lipids (HDL and LDL cholesterol and triglycerides) (Princen et al, 1998; van het Hof et al, 1997).
Epigallocatechin-3-gallate (EGCG) was effective at inhibiting ultraviolet B exposure (Chen, 1998) and preventing ultraviolet-induced skin damage that correlated with reduced lipid peroxidation (Kim, 1998). In humans, pretreatment of skin with Green Tea extracts 30 minutes prior to ultraviolet B (UVB) exposure resulted in a dose-dependent protection against acute erythema formation (Zhao, 1998).
Cancer Preventative Effects
The results of a case control study for breast cancer in Japanese women suggest that increased consumption of Green Tea prior to clinical cancer onset is associated with improved prognosis in stage I and II breast cancer; this may be related to the modifying effects of Green Tea on the clinical characteristics of the cancer (Nakachi et al, 1998).
The consumption of Green Tea was investigated in a case control study on the risk of digestive tract cancers (esophagus, stomach, colon, and rectal). A lower risk for stomach cancer was associated with a high consumption of Green Tea (7+ cups/day) (Inoue et al, 1998). A case-control study in Shanghai, China, found a strong inverse association between Green Tea consumption and various cancers (Ji et al, 1997).
Chemopreventive effects of Green Tea were examined in cigarette smokers by assessing the levels of sister chromatid exchange in peripheral lymphocytes in nonsmokers, smokers, and smokers who consumed 2 to 3 cups of Green Tea daily for 6 months. Green Tea appeared to block the “smoking-induced” increase in sister chromatid exchange (Lee et al, 1997; Shim et al, 1995). al, 1997).
Effects on Gut Microflora and Diarrheal Disease
Green Tea extract (400 mg polyphenols 3 times daily) promoted the growth of Lactobacillus and Bifidobacter species while inhibiting the growth of Clostridium perfringens and C difficile. This effect is significant not only in preventing Clostridial diarrhea diseases but also in colon cancer (Yamamoto et al, 1997). Green Tea polyphenols exhibit significant antiviral activity against rotavirus, a common cause of viral gastroenteritis in children (Yamamoto et al, 1997). Extracts of Green Tea inhibited the growth of various bacteria-causing diarrheal diseases including Vibrio cholerae, Salmonella typhimurium, and Salmonella typhi (Shetty et al, 1994).
Fraction analysis of Green Tea showed that Fraction III, IV, and V had relatively strong effects on D-Galactosamine-induced liver injury. Fraction III contained tea saponins and flavonoids. Fraction IV contained water-soluble compounds of low molecular weights such as free sugars, amino acids, and oligosaccharides. Fraction V was relatively pure and consisted of soluble dietary fibers (polysaccharides) (Sugiyama et al, 1999).
Inhibition of Xanthine Oxidase
Green Tea may be indicated in the treatment of gout as Green Tea polyphenols showed levels of inhibition of the enzyme xanthine oxidase (involved in the conversion of purines to uric acid). This was similar to those achieved by the drug allopurinol in an in vitro model (Aucamp, 1997).
Green Tea demonstrated significant increased plasma antioxidant activity in vivo in 21 volunteers in a crossover study. Experimentation consisted of 6 treatments on 6 different dates with at least 2 days separating treatments. After overnight fasting, subjects were given either: 300 mL of green or black tea, 240 mL of green or black tea supplemented with 60 mL of full fat milk, 300 mL of mineral water with 60 mL of full fat milk, or 240 mL of mineral water with 60 mL of full fat milk. Blood samples were obtained at baseline and at 30, 60, 90, and 120 minute intervals. Green Tea resulted in a significant increase in plasma antioxidant activity (p<0.001) for all timed blood samples. Plasma antioxidant activity was increased about 1.5 times with Green Tea ingestion and the rise in plasma catechins was about 5 times higher (Leenen et al, 2000).
The antioxidant activity of Green Tea was tested on two groups of 5 healthy adults. Each group ingested 300 mL of black or Green Tea after an overnight fast. The experiment was repeated on a separate day, adding 100 mL whole milk to the tea (ratio 1:4). Five subjects acted as controls. The human plasma antioxidant capacity (TRAP) was measured before and 30, 50, and 80 minutes from the ingestion of tea. Both teas inhibited the in vitro peroxidation in a dose-dependent manner. Green Tea was sixfold more potent than black tea. The addition of milk to either tea did not appreciably modify their in vitro antioxidant potential. In vivo, the ingestion of tea produced a significant increase of TRAP (p<0.05), similar in both teas, which peaked at 30 to 50 minutes. When tea was consumed with milk, the in vivo activity was totally inhibited. The inhibition of this effect by milk is thought to occur due to the complexity of tea polyphenols by milk proteins (Serafini et al, 1996).
Human population studies point to anticancer activities for tea, with early research showing an inverse association between consumption of tea and development of cancers of the stomach, urinary bladder, color, esophagus, lung, and pancreas. An empirical link between Green Tea consumption and cancer-fighting effects was established in the late 1980s. A 2005 review cites the tea's unique set of catechins, with antioxidant, antiangiogenesis, and antiproliferative elements, as explanation for the anticancer actions of Green Tea. The major tea catechin, (-)-epigallocatechin, has anticancer and medicinal properties that are examined. Researchers working with cancer cell lines have linked Green tea's anticancer activity to growth inhibition—a possible explanation for its antitumor activity. Several animal studies point to tea catechins as aids to cancer therapy. Studies on people with severe head and neck cancers indicated a positive role for an herbal mixture containing a blend of decaffeinated green tea and red pepper (Capsicum sp). Overall, more research is needed to clearly elucidate Green Tea's promising potential role in preventing and treating cancer (Cooper, 2005).
A proof-of-principle clinical study was conducted to assess the efficacy and safety of green tea catechins (GTCs) for the prevention of prostate cancer in men with high-grade prostate intraepithelial neoplasia. In this double-blind, placebo-controlled study, daily treatment consisted of 3 GTC capsules, 200 mg each, or placebo. After one year, 1 tumor was diagnosed among the 30 GTC-treated men, whereas 9 cancers were found among the 30 placebo-treated men. GTC was found to be safe and effective for treating premalignant lesions before prostate cancer develops. The researchers also observed that GTCs also reduced lower urinary track symptoms (Bettzi et al, 2006).
In an earlier study, Green Tea demonstrated no improvement in subjects with androgen-dependent prostate cancer in a multi-institutional, phase II clinical trial. Forty-two males with progressive prostate specific antigen (PSA) elevation with hormone therapy received 1 g Green Tea orally, mixed in warm or cold water, 6 times daily. Subjects were able to continue use of LH-releasing hormone agonist and visited their oncologist monthly for PSA measurement. After 4 months of treatment, only one patient experienced a tumor response, demonstrated by a 50% decrease in PSA level from baseline (from 229 ng/dL to 105 ng/dL). The response was not maintained beyond 2 months (Jatoi et al, 2003).
Components in Green Tea appear to have effective biochemical modulators for resistant tumors. Ehrlich ascites carcinoma cells were transplanted intraperitoneally into 6-week-old mice. Ascitic fluid was collected 7 days later and Doxorubicin (DOX), an antitumor medium, was introduced to the Ehrlich cancer cells. Theanine, an amino acid and (-)-epigallocatechin gallate (EGCG), both found in Green Tea, affected DOX tumor-cell activity. Theanine and EGCG inhibited DOX cellular efflux by 30.5% (p<0.05) and 19.5% (p<0.05), respectively. Combining theanine with DOX in P388 leukemia tumor treatment reduced tumor weight by 63% (p<0.01). It is believed that Green Tea exhibits few side effects when taken with an antitumor agent and appears to improve cancer chemotherapy (Sadzuka et al, 2000).
The consumption of Green Tea was investigated in a case control study for breast cancer in Japanese women. In stage I and II breast cancer, increased consumption of Green Tea was closely associated with decreased numbers of metastasized axillary lymph nodes among premenopausal patients and increased expression of PgR and ER among postmenopausal women. Long-term consumption of Green Tea (>5 cups daily) prior to clinical cancer onset was associated with significantly lower recurrence in stage I and II breast cancer. These results suggest that increased consumption of Green Tea prior to clinical cancer onset is associated with improved prognosis in stage I and II breast cancer and this may be related to the modifying effects of Green Tea on the clinical characteristics of the cancer (Nakachi et al, 1998).
A large (n = 2226) case-control study was conducted in China where recently diagnosed cancer cases (pancreatic, colon, and rectum) among residents between the ages of 30 and 74 years were included. Controls (n = 1552) were selected and matched to cases by age and gender and adjustments were made for age, income, education and cigarette smoking. As tea consumption increased, the incidence of all three cancers decreased. Women with the highest tea consumption (or = 200 g/month) had a 33% reduced risk for colon cancer, 43% reduced risk of rectal cancer and 47% reduction in the risk for pancreatic cancer (p= 0.07, 0.001, and 0.008 respectively). For men who consumed ≥ 300 g/month of Green Tea, the risk of colon cancer was reduced by 18%, for rectal cancer there was a 28% reduction of risk, and for pancreatic cancer the risk reduction was 37% (p= 0.38, 0.04, and 0.04, respectively) (Ji, 1997).
Catechins from Green Tea extract demonstrated anti-inflammatory action in Trinitrobenzene sulfonic acid (TNBS)-induced colitis in Sprague-Dawley rats. Experimentally induced TNBS colitis is histopathologically similar to Crohn's disease in humans. A significant reduction in macroscopic damage of the colon was observed in rats supplemented with catechins; no perforations of the distal colon or adhesions were found, suggesting inhibition of inflammatory processes (Sato et al, 1998).
Dental Caries Prevention
In a double-blind study, 26 adult males (mean age 26.5 years) demonstrated an inhibition rate on plaque development of 30% to 43% when given a solution containing 0.05%, 0.1%, 0.2%, and 0.5% of Green Tea polyphenols as a mouthwash compared to controls. The concentration of caries-promoting bacteria and lactic acid were also reduced (Yamamoto et al, 1997). An extract of oolong tea (semifermented tea leaves of Camellia sinensis) containing polymerized polyphenols in 0.2% ethanol was administered to 35 volunteers between 18 and 29 years of age to test the inhibitory effect of the extract on dental plaque deposition. The study was repeated 1 week after the first trial using 0.2% ethanol without the tea extract. The oolong tea cohort showed significant inhibition of plaque deposition (Ooshima, 1994).
Diabetes, Type 2
A retrospective 5-year cohort study in 6,277 men and 10, 686 women from 25 communities in Japan was done to examine the relationship between consumption of tea (Green Tea, black tea, and oolong tea) and risk of developing Type 2 diabetes. The participants were 40 to 65 years old and healthy at study start. Analysis revealed that people who (according to questionnaire answers) frequently drank green tea (more than 6 cups daily) or coffee (more than 3 cups daily) were less likely to develop Type 2 diabetes than people who drank less than 1 cup of either beverage per week (33% lower risk for diabetes with Green Tea and 42% lower risk with coffee). This association was particularly strong for women and overweight men. Consumption of black and oolong teas did not appear to reduce diabetes risk, however. The authors conclude that while it is possible that other factors influenced these results, the higher intake of caffeine—whether from Green Tea or coffee—was significantly associated with a lower risk of developing Type 2 diabetes (Iso, 2006).
To study the effects of the intake of green tea and polyphenols on insulin resistance and systemic inflammation, a randomized, controlled trial was conducted on 66 patients with borderline diabetes or diabetes over a period of two months. Subjects in the intervention group were asked to take a packet of green tea extracts/powder containing 544 mg polyphenols (456 mg catechins) daily, and to divide the green tea extracts/powder in a packet into 3 or 4 portions, each to be dissolved in hot water. Daily supplementary intake of approximately 500 mg green tea polyphenols did not show a clear effect on blood glucose levels, HbA1c levels, insulin resistance, or inflammation markers. However, a positive correlation between the level of polyphenols intake and insulin level was demonstrated, warranting further investigation (Fukino et al, 2006).
In October 2006, the Food and Drug Administration approved the use of kunecatechins (Veregen) from Green Tea for the treatment of external genital and perianal warts based on the pooled results of two randomized, double-blind, phase III clinical trials that involved 1,000 individuals who were immunocompromised. The participants applied the ointment 3 times daily for up to 16 weeks, or until the warts completely cleared. Of the participants treated with the Green Tea compound in the 2 studies, 53.6% had complete clearance of the warts by week 16, while only 35.3% of those who applied a placebo did (Centerwatch, 2006).
To clarify the effect of Green Tea consumption on cardiovascular disease and cancer, a large, population-based cohort study was conducted as part of the Ohsaki National Health Insurance Cohort Study in Japan. The cause of mortalities was tracked in these participants for up to 11 years (and for up to 7 years for cause-specific mortalities). In this time frame, 4,209 people died. Analysis revealed that consumption of Green Tea was associated with a lower risk of death from cardiovascular disease, as well as from other causes with the exception of cancer. The strongest inverse association between Green Tea intake and reduced risk of death was for death caused by stroke. Specifically, compared with women who consumed less than 1 cup daily of Green Tea, those who drank 5 or more cups daily had a 42% lower risk of death due to stroke and a 62% lower risk of death due to this cause. The authors attribute the cardioprotective-effects of Green Tea to a threshold effect rather than a dose-response relationship, meaning that a person who typically consumed at least 1 cup of Green Tea daily did accrue some benefit. Future clinical trials will need to be done to confirm GreenTea's apparent protective effect against death from cardiovascular disease and other causes (Kuriyama, 2006).
Green Tea extract enriched with theaflavin reduced serum total cholesterol and LDL-C in adults with mild to moderate hypercholesterolemia in a 12-week double-blind trial. Two hundred twenty subjects were randomized to receive 1 capsule orally daily that contained either a theaflavin-enriched Green Tea extract (75 mg theaflavins, 150 mg Green Tea catechins, and 150 mg other tea polyphenols) or placebo. Subjects were asked to maintain their traditional Chinese diet and tea intake. Dietary intake was assessed using 3-day food records. Lipid and lipoprotein concentrations were evaluated at week -2, week 0, week 4, and week 12. The theaflavin-enriched Green Tea extract decreased serum total cholesterol and LDL-C by 11.3% (p=0.01) and 16.4% (p=0.01), respectively. There was no statistical difference for nutrient intake between the treatment and placebo groups at baseline or at 8 weeks for any dietary variable (Maron et al, 2003).
Green Tea may decrease the risk of coronary heart disease by inhibiting the development of atherosclerosis, protecting LDL against oxidation and foam cell formation. Cholesterol was dose-dependently reduced by Green Tea in human umbilical cord vascular endothelial cells (HUVEC). Cellular content of cholesterol in HUVEC treated with 5 and 10 mcg/mL of Green Tea was lower than control oxidized LDL (p<0.001 and p<0.01, respectively). Catechins found in Green Tea suppressed endothelial cellular LDL oxidation, suggesting catechins may be the primary antioxidant (Yang & Koo, 2000a).
Thirty-four obese women with polycystic ovary syndrome (PCOS), an endocrine disorder, were randomized into treatment with Green Tea capsules (Lung Chen tea powder prepared by brewing tea leaves of 2% weight/volume in freshly boiled water for 30 minutes and then filtered and freeze-dried) or placebo over the course of 3 months. During this time, numerous measurements of hormonal, biochemical, and anthropomorphic condition were taken and compared. The group receiving Green Tea showed a nonsignificant drop in body weight (2.4%), while the body mass index and body fat content for the women taking placebo became significantly higher. Analysis revealed that the Green Tea supplement failed to significantly reduce body weight in these obese individuals with PCOS. Nor did the Green Tea change glucose or lipid metabolism, hormone levels, or menstrual regularity (Chan, 2005).
In contrast, moderate weight loss after ingestion of green tea (GT) was found in a double-blind, placebo-controlled study. Forty-six female subjects were fed in energy balance from day 1 to 3, followed by a low-energy diet (LED) with GT or placebo from day 4 to 87. The LED-period consisted of a 4-week phase I, followed by an 8-week phase II. No significant differences were observed between blood parameters of the two groups; however, modest weight loss improved HDL cholesterol and blood pressure (Diepvens et al, 2006).
A randomized, parallel, placebo-controlled study was performed to investigate whether Green Tea improves weight maintenances by preventing or limiting weight regain after weight loss of 5 to 10% in overweight and moderately obese subjects. A total of 104 participants received a 4-week, very low-energy diet intervention, followed by a weight-maintenance period of 13 weeks including either Green Tea or placebo. Body weight regain was not significantly different between the two groups. In the Green Tea group treatment, habitual high caffeine consumption was in fact associated with a higher weight regain compared with habitual low caffeine consumption (Kovacs et al, 2004).
An earlier double-blind trial demonstrated thermogenic properties of Green Tea and its fat oxidizing capabilities. Ten healthy male subjects received Green Tea extract (90 mg epigallocatechin gallate and 50 mg caffeine), 50 mg caffeine, or placebo 3 times daily on 3 separate 24-hour stays in a respiratory chamber. Green Tea extract produced a significantly higher diurnal (p<0.01) and total 24-hour energy expenditure (EE; p<0.01) compared to caffeine and placebo; nocturnal EE was not significantly affected. The respiratory quotients decreased significantly more during treatment with Green Tea during diurnal, nocturnal, and total 24-hour periods compared to caffeine and placebo (p<0.01 in 8/10 subjects compared to placebo). This effect was attributed to an increase in thermogenesis and in fat oxidation since urinary nitrogen losses did not differ between the 3 groups. Compared to placebo, carbohydrate oxidation significantly decreased (p<0.001) and fat oxidation significantly increased (41.5% vs 31.6% for placebo; p<0.001) with the consumption of Green Tea extract. Investigators concluded that these metabolic effects resulted from Green Tea components other than caffeine (Dulloo et al, 1999).
The combination regimen of topical and oral Green Tea supplementation on the clinical and histologic characteristic of photoaging was evaluated using 10% green tea cream and 300 mg twice-daily Green Tea oral supplementation or a placebo for 8 weeks. Forty women with moderate photoaging were enrolled into the double-blind, placebo-controlled study. No significant differences in clinical grading were found between the treatment groups. Histologic grading of skin biopsies did show significant improvement in the elastic tissue content of treated specimens in the Green Tea group (p<0.05) (Chiu et al, 2005).
Indications & Usage
Though no Commission E monograph exists for Green Tea, there is clinical evidence that it is likely to be useful as a cancer preventive and as a preventive for dental caries.
Internal application: Green Tea is used for stomach disorders, migraine, symptoms of fatigue, vomiting and diarrhea when taken as a beverage. It can be used to increase performance (stimulant effect).
Camellia sinensis is used for cardiac and circulatory conditions, headaches, states of agitation, states of depression, and stomach complaints.
In India, tea preparations are used for diarrhea, loss of appetite, hyperdypsia, migraine, cardiac pain, fever, and fatigue.
In China Green Tea is used to treat migraine, nausea, diarrhea resulting from malaria, and digestion problems. It is also used as a cancer preventive.
Precautions & Adverse Reactions
Side effects of tea consumption are possible with persons who have sensitive stomachs, chiefly due to the chlorogenic acid and tannin content. Hyperacidity, gastric irritation, reduction of appetite, as well as obstipation or diarrhea, could be the result of intense tea consumption. These side effects can be generally avoided by the addition of milk (reduction of the chlorogenic acid and other tannins).
Care should be taken with patients that have weakened cardiovascular systems, renal diseases, thyroid hyperfunction, elevated susceptibility to spasm and certain psychic disorders, such as panicky states of anxiety. With long-term intake of dosages above 1.5 g caffeine per day, nonspecific symptoms occur, such as restlessness, irritability, sleeplessness, palpitations, vertigo, vomiting, diarrhea, loss of appetite, and headache.
Green Tea caused reduction of blood testosterone, estradiol, leptin, insulin, insulin-like growth factor I, and LH levels in Sprague-Dawley rats injected intraperitoneally with (-)-epigallocatechin gallate (EGCG). Food consumption and body weight were reduced as well as glucose, cholesterol, and triglyceride levels. Organ weight of accessory sexual organs (prostate, uterus, and ovaries) also decreased (Kao Yung-Hsi et al, 2000).
Reports of mycrocytic anemia in infants consuming an average of 250 mL of Green Tea per day have been reported. This effect may be due to impaired iron metabolism (Dombek, 1993; Merhav et al, 1985).
It is recommended that women who are pregnant avoid consumption of Green Tea due to the caffeine content (10 to 50 mg per cup depending on variety and method of preparation), or at least avoid large quantities of Green Tea (Yamamoto et al, 1997).
Infants whose nursing mothers consume beverages containing caffeine could suffer from sleep disorders.
Concurrent use may result in reduced anticoagulant effectiveness. Clinical Management: It appears that the quantity of Green Tea consumed and the method of production affect the amount of vitamin K in Green Tea. Patients who choose to drink Green Tea should be advised to consume a consistent amount and use a consistent brand and method of brewing.
Reabsorption can be delayed because of chemical bonding with the tannins in tea.
Overdosage (quantities corresponding to more than 300 mg caffeine, or 5 cups of tea as a beverage) can lead to restlessness, tremor, and elevated reflex excitability. The first signs of poisoning are vomiting and abdominal spasm. Fatal poisonings are not possible with tea beverages.
Mode of Administration
Green Tea is administered as an infusion or in capsule form for internal use.
The usual concentration of total polyphenols in dried Green Tea leaf is around 8% to 12%. One cup of Green Tea normally contains 50 to 100 mg polyphenols (Murray & Pizzorno, 1998; Yamamoto, 1997).
- Capsules – 100 mg, 150 mg, 175 mg, 333 mg, 383 mg, 500 mg
- Liquid – 1:1
- Tablets – 100 mg
- Dried extract (instant tea) — Processed using steam extraction followed by drying
- Filter tea bags — Available commercially containing 1.8 to 2.2 g tea
To prepare a tea, boiling water is poured over a heaped teaspoon of leaf tea, a level teaspoon of crushed leaves or a tea bag and left to steep for 3 to 10 minutes as required. The caffeine is almost completely drawn after approximately 3 minutes. The tannin-containing substance (and with it the antidiarrheal action) increases when the tea is left to brew.
A daily dose of 300 to 400 mg of polyphenols is typical. The amount of polyphenols in 3 cups of Green Tea is between 240 and 320 mg.
5 to 10 drops, 1 tablet, or 5 to 10 globules 1 to 3 times daily or 1 mL injection solution sc twice weekly (HAB1).
Store tightly sealed and dried; store separately from other chemicals and aromatic substances.