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PubMed1999

Antimicrobial activity of tea as affected by the degree of fermentation and manufacturing season.

Bacillus subtilis, Escherichia coli, Proteus vulgaris, Pseudomonas fluorescens, Salmonella sp. and Staphylococcus aureus were used to test the antimicrobial activity of tea flush extract and extracts of various tea products. Among the six test organisms, P. fluorescens was the most sensitive to the extracts, while B. subtilis was the least sensitive. In general, antimicrobial activity decreased when the extents of tea fermentation increased. The antimicrobial activities of tea flush extract and extracts of tea products with different extents of fermentation varied with test organisms. Tea flush and Green tea, the unfermented tea, exerted the strongest antimicrobial activity followed by the partially fermented tea products such as Longjing, Tieh-Kuan-Ying, Paochung, and Oolong teas. On the other hand, Black tea, the completely fermented tea, showed the least antimicrobial activity. It was also noted that extracts of Oolong tea prepared in summer exhibited the strongest antimicrobial activity, followed by those prepared in spring, winter and fall.

Anti-Bacterial Agents↗
PubMed1999

Antimutagenic and anticarcinogenic activity of tea polyphenols.

Tea is the most popular beverage, consumed by over two thirds of the world's population. Tea is processed differently in different parts of the world to give green (20%), black (78%) or oolong tea (2%). Green tea is consumed mostly in Japan and China. The antimutagenic and anticarcinogenic activities of green tea are extensively examined. The chemical components of green and black tea are polyphenols, which include EC, ECG, EGC, EGCG and TFs. This article reviews the epidemiological and experimental studies on the antimutagenicity and anticarcinogenicity of tea extracts and tea polyphenols. In Japan, an epidemiological study showed an inverse relationship between habitual green tea drinking and the standardized mortality rates for cancer. Some cohort studies on Chanoyu (Japanese tea ceremony) women teachers also showed that their mortality ratio including deaths caused by malignant neoplasms were surprisingly low. The antimutagenic activity against various mutagens of tea extracts and polyphenols including ECG and EGCG has been demonstrated in microbial systems (Salmonella typhimurium and Escherichia coli), mammalian cell systems and in vivo animal tests. The anticarcinogenic activity of tea phenols has been shown in experimental animals such as rats and mice, in transplantable tumors, carcinogen-induced tumors in digestive organs, mammary glands, hepatocarcinomas, lung cancers, skin tumors, leukemia, tumor promotion and metastasis. The mechanisms of antimutagenesis and anticarcinogenesis of tea polyphenols suggest that the inhibition of tumors may be due to both extracellular and intracellular mechanisms including the modulation of metabolism, blocking or suppression, modulation of DNA replication and repair effects, promotion, inhibition of invasion and metastasis, and induction of novel mechanisms.

Animals↗
PubMed2002

Tea enhances insulin activity.

The most widely known health benefits of tea relate to the polyphenols as the principal active ingredients in protection against oxidative damage and in antibacterial, antiviral, anticarcinogenic, and antimutagenic activities, but polyphenols in tea may also increase insulin activity. The objective of this study was to determine the insulin-enhancing properties of tea and its components. Tea, as normally consumed, was shown to increase insulin activity >15-fold in vitro in an epididymal fat cell assay. Black, green, and oolong teas but not herbal teas, which are not teas in the traditional sense because they do not contain leaves of Camellia senensis, were all shown to increase insulin activity. High-performance liquid chromatography fractionation of tea extracts utilizing a Waters SymmetryPrep C18 column showed that the majority of the insulin-potentiating activity for green and oolong teas was due to epigallocatechin gallate. For black tea, the activity was present in several regions of the chromatogram corresponding to, in addition to epigallocatechin gallate, tannins, theaflavins, and other undefined compounds. Several known compounds found in tea were shown to enhance insulin with the greatest activity due to epigallocatechin gallate followed by epicatechin gallate, tannins, and theaflavins. Caffeine, catechin, and epicatechin displayed insignificant insulin-enhancing activities. Addition of lemon to the tea did not affect the insulin-potentiating activity. Addition of 5 g of 2% milk per cup decreased the insulin-potentiating activity one-third, and addition of 50 g of milk per cup decreased the insulin-potentiating activity approximately 90%. Nondairy creamers and soy milk also decreased the insulin-enhancing activity. These data demonstrate that tea contains in vitro insulin-enhancing activity and the predominant active ingredient is epigallocatechin gallate.

Adipocytes↗
PubMed2000

In vivo antioxidant effect of green tea.

OBJECTIVE: The object of this study was to investigate the in vivo antioxidant effect of green tea and dosage effect of green tea on antioxidant effect. DESIGN: We tested 10 healthy subjects (aged 23-25 y, five women and five men) with overnight fasting. The total antioxidant capacity of plasma was measured at baseline and 60 min and 120 min after ingestion of 150 ml green tea. Green tea was prepared by infusing 2.5 g of dried green tea leaves for 2 min at 80 degrees C in 150 ml of water. In the second week, they took 300 ml of tea (5.0 g of green tea leaves) and, in the third week, 450 ml of tea (7.5 g of green tea leaves). The total antioxidant capacities of plasma were determined with a Total Antioxidant Kit (Randox Laboratories Ltd, UK) using a Cobas Mira analyser (Roche Diagnostic Systems Inc., Switzerland). The mean intra-assay coefficient of variation was 1.2%. RESULTS: The total antioxidant capacity of plasma increased by 1.1% at 60 min and 2.1% at 120 min over baseline value in subjects consuming 150 ml of green tea, which was statistically not significant. However, total antioxidant capacity of plasma after consuming 300 ml of green tea showed a significant increase of 7.0% after 60 min and 6.2% after 120 min (P<0.0001), and after consuming 450 ml 12.0% after 60 min and 12.7% after 120 min over baseline value (P<0.0001). CONCLUSIONS: Total antioxidant capacity of plasma was significantly increased after taking green tea in amounts of 300 and 450 ml. A positive increment according to green tea dosage was also observed. SPONSORSHIP: This work was funded by the Pacific Corporation (Korea).

Adult↗
PubMed2005

Ethyl acetate extract from black tea prevents neuromuscular blockade by botulinum neurotoxin type A in vitro.

Botulinum neurotoxin produced by Clostridium botulinum is the strongest neurotoxin and causes botulism in mammals. The current study aimed to find an inactivator for botulinum neurotoxin in black, oolong, roasted, and green teas. The ability of the four teas to inactivate the neuromuscular blocking action of botulinum neurotoxin was determined. Water extracts from black, oolong, and roasted teas protected against the toxicity of botulinum neurotoxin type A in mouse phrenic nerve-diaphragm preparations. The order of potency of the water extracts was black tea > oolong tea > roasted tea > green tea (no effect). The effects of several organic solvent extracts of black tea water extract were examined, and the order of potency was ethyl acetate extract > butanol extract = remaining extract > chloroform extract (no effect). Ethyl acetate extracts from oolong, roasted, and green tea water extracts also exhibited a stronger protecting effect than chloroform, butanol, and remaining extracts from these teas, but they had weaker protective effect than ethyl acetate extract from black tea water extract. These protective effects occurred only when each extract was pre-mixed with the toxin before the assay, and they were not modified by mixing each extract with bovine serum albumin (BSA) before adding the toxin. These results indicate that ethyl acetate extract from black tea is the best source for searching for tea-derived inactivating substance(s) of botulinum neurotoxin.

Acetates↗
PubMed2001

Tea flavonoids: bioavailability in vivo and effects on cell signaling pathways in vitro.

The elucidation of the potential health benefits of tea beverage continues to be a focus of research in many laboratories. Beneficial effects of tea have been particularly evident in animal tumorigenesis models, with green and black tea frequently demonstrating similar effectivity. Human data are now emerging to support a beneficial role for tea in cardiovascular disease, but the data with respect to cancer risk at various sites remain inconclusive. The constituent flavonoids of green and black tea beverage are known to be potent antioxidants, and although this may be a major factor in explaining their biological activity, it appears that the gallated flavonoids in particular (e.g., epigallocatechin gallate and the gallated theaflavins) impact on a wide range of molecular targets that influence cell growth and more specifically pathways such as those involving angiogenesis. Data on the pharmacokinetic properties of tea flavonoids, primarily on the catechins and therefore related most closely to green tea, have provided indications of the plasma levels and circulating molecular forms that may be expected in humans following tea consumption. The structural complexity of black tea flavonoids, in particular the thearubigins, has hindered efforts to describe their bioavailability and to perform mechanistic studies. Recent studies on the effects of catechins and theaflavins on growth factor-, nuclear factor-kappaB-, and stress-mediated signal transductions are described in this review, where possible in relation to their bioavailability in vivo. These studies indicate that effects that may be relevant to both cancer and atherosclerosis are often observed at tea flavonoid levels that could realistically be encountered in vivo. However, more studies need to be performed using those molecular forms of tea flavonoids (methylated, sulfated, and glucuronidated conjugates) that are the major circulating species encountered following tea consumption. Such studies, combined with further human epidemiological and interventional data, should ultimately elucidate the full beneficial potential of tea beverage on human health.

Cell Cycle↗
PubMed1995

Inhibition of N-nitrosomethylbenzylamine-induced esophageal tumorigenesis in rats by green and black tea.

In this study, we investigated the effects of green tea and black tea, when given either during or after carcinogen treatment, on esophageal tumorigenesis in male Sprague-Dawley rats. Rats were treated with N-nitrosomethylbenzylamine (NMBzA) (2.5 mg/kg, s.c., twice weekly) for 5 weeks; 39 weeks after the initial dose of NMBzA, 65% of the rats had esophageal tumors with an average of 1.4 +/- 0.3 tumors per rat. In the groups of rats receiving 0.6% of decaffeinated green tea (DGT) or decaffeinated black tea (DBT) (6 mg tea solids/ml) as the sole source of drinking fluid during the NMBzA-treatment period, esophageal tumor incidence and multiplicity were reduced by approximately 70%. When the tea preparations were given after the NMBzA treatment period, the esophageal papilloma incidence and multiplicity were reduced by approximately 50%. The volume per tumor was much smaller in rats that received black tea after the carcinogen treatment period. In a second experiment, NMBzA was given to rats at a dose of 3.5 mg/kg (s.c., twice weekly) for 5 weeks; after 16 weeks, the tumor incidence was 82% and tumor multiplicity was 6.7 +/- 1.2 tumors per rat. In the groups of rats receiving 0.9% regular green tea (RGT) or DGT after the NMBzA treatment period, tumor multiplicity was decreased by > 55%. The volume per tumor was reduced by approximately 60% in the rats receiving 0.9% RGT. Histological analysis indicated that both the incidence and multiplicity of esophageal carcinoma was decreased by either RGT or DGT. The blood and urine levels of green tea polyphenols due to tea administration were determined in rats, and the levels were comparable to those in humans after tea ingestion. The above results indicate that both green tea and black tea can inhibit the tumorigenic action of NMBzA during the period of carcinogen treatment and the subsequent molecular events important for esophageal tumorigenesis.

Animals↗
PubMed1997

Inhibitory effect of black tea on the growth of established skin tumors in mice: effects on tumor size, apoptosis, mitosis and bromodeoxyuridine incorporation into DNA.

Female CD-1 mice were initiated with a single topical application of 7,12-dimethylbenz[a]anthracene and promoted with 12-O-tetradecanoylphorbol-13-acetate. Mice with established papillomas were then treated with black tea or decaffeinated black tea (approximately 4 mg tea solids/ml) as the sole source of drinking fluid for 11-15 weeks. In four separate experiments, oral administration of black tea inhibited the growth of papillomas (increase in tumor volume/mouse) by an average of 35%, 37%, 41% and 48%, respectively. Studies with decaffeinated black tea gave inconsistent results. In one experiment, administration of decaffeinated black tea inhibited papilloma growth (increase in tumor volume/mouse) by 27%, but in two additional experiments papilloma growth was stimulated by 14% and 193%, respectively. In a separate experiment, skin tumors were generated by treating SKH-1 female mice with ultraviolet B light (UVB; 30 mJ/cm2) twice weekly for 22 weeks, after which UVB administration was stopped. Tumors were allowed to develop during the following 13 weeks, and tumor-bearing mice were then treated with black tea (6 mg/ml tea solids) as the drinking fluid for 11 weeks. In this experiment, tumor growth (increase in tumor volume/mouse) was inhibited by 70%. Histological examination revealed that tea-treated mice had a 58% decrease in the number of nonmalignant tumors (primarily keratoacanthomas)/mouse and a 54% decrease in the number of squamous cell carcinomas/mouse. In addition, administration of black tea decreased the volume per tumor by 60% for nonmalignant tumors and by 84% for carcinomas. Mechanistic studies with tumors from these mice revealed that administration of black tea decreased the bromodeoxyuridine labeling index in squamous cell papillomas, keratoacanthomas and squamous cell carcinomas by 56%, 45% and 35%, respectively, and the apoptosis index was increased by 44%, 100% and 95%, respectively. Administration of black tea decreased the mitotic index in keratoacanthomas and squamous cell carcinomas by 42% and 16%, respectively. The results indicate that oral administration of black tea to tumor-bearing mice inhibited proliferation and enhanced apoptosis in nonmalignant and malignant skin tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2002

Inhibition of 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral carcinogenesis in hamsters by tea and curcumin.

Tea is one of the most popular beverages consumed in the world. Curcumin, the major yellow pigment in turmeric, is used widely as a spice and food-coloring agent. In this study, we studied the effects of tea and curcumin on 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral carcinogenesis in hamsters. DMBA solution (0.5% in mineral oil, 0.1 ml) was applied topically to the left cheek pouch of male Syrian golden hamsters 3 times/week for 6 weeks. Two days after the last treatment of DMBA, the animals received green tea (6 mg tea solids/ml) as drinking fluid, or 10 mmol curcumin applied topically 3 times/week, or the combination of green tea and curcumin treatment, or no treatment for 18 weeks. The combination of tea and curcumin significantly decreased the oral visible tumor incidence from 92.3% (24/26) to 69.2% (18/26) and the squamous cell carcinoma (SCC) incidence from 76.9% (20/26) to 42.3% (11/26). The combination of tea and curcumin also decreased the number of visible tumors and the tumor volume by 52.4 and 69.8%, as well as the numbers of SCC, dysplasic lesions and papillomas by 62.0, 37.5 and 48.7%, respectively. Green tea or curcumin treatment decreased the number of visible tumors by 35.1 or 39.6%, the tumor volume by 41.6 or 61.3% and the number of SCC by 53.3 or 51.3%, respectively. Green tea also decreased the number of dysplasic lesions. Curcumin also significantly decreased the SCC incidence. Tea and curcumin, singly or in combination, decreased the proliferation index in hyperplasia, dysplasia and papillomas. Only the combination treatment decreased the proliferation index in SCC. Tea alone and in combination with curcumin significantly increased the apoptotic index in dysplasia and SCC. Curcumin, alone and in combination with tea, significantly inhibited the angiogenesis in papilloma and SCC. The results suggested that green tea and curcumin had inhibitory effects against oral carcinogenesis at the post-initiation stage and such inhibition may be related to the suppression of cell proliferation, induction of apoptosis and inhibition of angiogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

A comparison of the antimutagenic potential of green, black and decaffeinated teas: contribution of flavanols to the antimutagenic effect.

The present study was undertaken to compare the antimutagenic activity of aqueous extracts, at the concentrations used for human consumption, from green, black and decaffeinated black tea. Antimutagenic potential was evaluated against three indirect-acting dietary carcinogens, Glu-P-1, benzo(a)pyrene and nitrosopyrrolidine. All three types of tea gave rise to strong and concentration-dependent suppression of the mutagenicity of the three premutagens in the presence of an activation system. No major difference in the antimutagenic potential of the three types of tea could be discerned. Black tea, decaffeinated black tea and, to a lesser extent, green tea also antagonized the mutagenicity of the direct-acting mutagen 9-aminoacridine. All three types of tea inhibited markedly the NADPH-dependent reduction of cytochrome c and the O-dealkylations of ethoxy-, methoxy- and, to a much lesser extent, pentoxy-resorufin. When the microsomal metabolism was terminated, after the metabolic activation of the premutagens, incorporation of the aqueous tea extracts into the activation system caused a concentration-dependent suppression of mutagenic response. No significant difference in the antimutagenic activity of the three types of tea in this system was evident. Bearing in mind the much higher concentration of flavanols in green tea compared with the black teas, it may be concluded either that these compounds are unlikely to be the major tea components responsible for the antimutagenic, and possibly anticarcinogenic, properties of tea or that their fermentation products are similarly active.

Aminacrine↗
PubMed1998

Inhibition of salivary amylase by black and green teas and their effects on the intraoral hydrolysis of starch.

Tea decoctions prepared from a number of black and green teas inhibited amylase in human saliva. Black teas gave higher levels of inhibition than green teas, and removal of tea tannins with gelatin led to the loss of inhibitory activity from all decoctions. Streptococcal amylase was similarly inhibited by tea decoctions. Fluoride was without effect on amylase. Since salivary amylase hydrolyzes food starch to low molecular weight fermentable carbohydrates, experiments were carried out to determine whether tea decoctions would interfere with the release of maltose in food particles that became entrapped on the dentition. Subjects consumed salted crackers and rinsed subsequently for 30 s with black or green tea decoctions, or water. Maltose release was reduced by up to about 70% after rinsing with the teas. Black tea decoction was significantly more effective than green tea, in agreement with the in vitro data. The observations supported the hypothesis that tea consumption can be effective in reducing the cariogenic potential of starch-containing foods such as crackers and cakes. Tea may reduce the tendency for these foods to serve as slow-release sources of fermentable carbohydrate.

Adult↗
PubMed1998

No effect of consumption of green and black tea on plasma lipid and antioxidant levels and on LDL oxidation in smokers.

Intake of flavonoids is associated with a reduced cardiovascular risk. Oxidation of LDL is a major step in atherogenesis, and antioxidants may protect LDL from oxidation. Because tea is an important source of flavonoids, which are strong antioxidants, we have assessed in a randomized, placebo-controlled study the effect of consumption of black and green tea and of intake of isolated green tea polyphenols on LDL oxidation ex vivo and on plasma levels of antioxidants and lipids. Healthy male and female smokers (aged 34+/-12 years, 13 to 16 per group) consumed during a 4-week period 6 cups (900 mL) of black or green tea or water per day, or they received as a supplement 3.6 grams of green tea polyphenols per day (equivalent to the consumption of 18 cups of green tea per day). Consumption of black or green tea had no effect on plasma cholesterol and triglycerides, HDL and LDL cholesterol, plasma vitamins C and E, beta-carotene, and uric acid. No differences were found in parameters of LDL oxidation. Intake of green tea polyphenols decreased plasma vitamin E significantly in that group compared with the control group (-11% P=.016) but had no effect on LDL oxidation ex vivo. We conclude that consumption of black or green tea (6 cups per day) has no effect on plasma lipids and no sparing effect on plasma antioxidant vitamins and that intake of a high dose of isolated green tea polyphenols decreases plasma vitamin E. Although tea polyphenols had a potent antioxidant activity on LDL oxidation in vitro, no effect was found on LDL oxidation ex vivo after consumption of green or black tea or intake of a green tea polyphenol isolate.

Adult↗
PubMed2002

Tea consumption and mortality after acute myocardial infarction.

BACKGROUND: Some studies have suggested that tea consumption may be associated with lower mortality among individuals with cardiovascular disease, but the effects of tea consumption on mortality after acute myocardial infarction are unknown. METHODS AND RESULTS: As part of the Determinants of Myocardial Infarction Onset Study, we performed a prospective cohort study of 1900 patients hospitalized with a confirmed acute myocardial infarction between 1989 and 1994, with a median follow-up of 3.8 years. Trained interviewers assessed self-reported usual weekly caffeinated tea consumption during the year before infarction with a standardized questionnaire. We compared long-term mortality according to tea consumption using Cox proportional hazards regression. Of the 1900 patients, 1019 consumed no tea (nondrinkers), 615 consumed <14 cups per week (moderate tea drinkers), and 266 consumed 14 or more cups per week (heavy tea drinkers). Compared with nondrinkers, age- and sex-adjusted mortality was lower among moderate tea drinkers (hazard ratio, 0.69; 95% CI, 0.53 to 0.89) and heavy tea drinkers (hazard ratio, 0.61; 95% CI, 0.42 to 0.86). Additional adjustment for clinical and sociodemographic characteristics did not appreciably alter this association (hazard ratio, 0.72; 95% CI, 0.55 to 0.94 for moderate tea drinkers; hazard ratio, 0.56; 95% CI, 0.37 to 0.84 for heavy tea drinkers). The association of tea and mortality was similar for total and cardiovascular mortality. CONCLUSIONS: Self-reported tea consumption in the year before acute myocardial infarction is associated with lower mortality after infarction.

Cohort Studies↗
PubMed2001

Tea consumption modulates hepatic drug metabolizing enzymes in Wistar rats.

The antioxidant, antimutagenic and anticarcinogenic activities of green tea and its polyphenols have been reported. As bioactivation of the precarcinogens and detoxification of ultimate carcinogens are mainly carried out by hepatic metabolizing enzymes, we have investigated the modulation of these enzyme activities subsequent to tea consumption in rats. Female Wistar rats were divided into eight groups (n = 5). Six groups were given aqueous solutions (2%, w/v) of six different teas (New Zealand green tea, Australian green tea, Java green tea, Dragon green tea, Gunpowder green tea or English Breakfast black tea) as the sole source of fluid. One group was given a standard green tea extract (0.5%, w/v) while the control group had free access to water. At the end of four-weeks treatment, different cytochrome P450 (CYP) isoform and phase II enzyme activities were determined by incubation of the liver microsomes or cytosols with appropriate substrates. CYP 1A2 activity was markedly increased in all the tea treatment groups (P < 0.05). CYP 1A1 activity was increased significantly in most of the groups except for the Madura, Gunpowder, and Java green tea-treatment groups. Cytosolic glutathione-S-transferase activity was significantly increased (P< 0.05) in the New Zealand, Gunpowder, and Java green tea-treatment groups. The microsomal UDP-glucuronosyl transferase activity remained unchanged or was moderately increased in most of the groups. The balance between the phase I carcinogen-activating enzymes and the phase II detoxifying enzymes could be important in determining the risk of developing chemically-induced cancer.

Administration, Oral↗
PubMed2002

Antimutagenic activity of selenium-enriched green tea toward the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline.

Both selenium and green tea have been reported to exhibit antigenotoxic and cancer chemopreventive properties. We compared the antimutagenic activities of regular green tea and selenium-enriched green tea obtained from Hubei Province, China, toward the heterocyclic amine, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in the Salmonella assay. Selenium-enriched green tea obtained by foliar application of selenite exhibited concentration-dependent inhibition of IQ-induced mutagenesis in the presence of rat liver S9 and was significantly more effective than regular green tea tested under the same conditions. Analytical studies revealed no major differences in the polyphenol or caffeine content between regular green tea and selenium-enriched green tea, but the latter tea contained approximately 60-fold higher concentrations of selenium compared with regular green tea. The only soluble form of selenium was identified as selenite. The antimutagenic effects of certain individual tea constituents, such as epicatechin gallate and catechin, were enhanced by the addition of selenite to the Salmonella assay. Sodium selenite, sodium selenate, seleno-DL-cysteine, seleno-L-methionine, and L-Se-methylselenocysteine were not antimutagenic toward IQ when tested alone, but augmented significantly the inhibitory potency of green tea. The results suggested an enhancing ("coantimutagenic") effect of selenium in combination with green tea in vitro, but in vivo studies are needed to assess whether there is a synergistic effect of tea and selenium to protect against heterocyclic amine-induced mutagenesis and carcinogenesis.

Animals↗
PubMed2004

[A study on the association between tea consumption and stroke].

OBJECTIVE: The aim of the study was to investigate the association between tea consumption and stroke. METHODS: A cross sectional study was conducted in autumn, 1998. The subjects were from 12 provinces in China. 15 groups of populations were selected by cluster randomized sampling and each group had about 1000 persons, aged from 35 to 60 years old. 14 212 subjects had complete data for analysis. Data regarding tea drinking would include drinking status, dose and type of teas. Logistic regression was used to analyze the association between tea consumption and stroke. RESULTS: There was a strong inverse correlation between tea drinking and stroke after adjusting other risk factors of stroke (P < 0.05). The odds ratio (OR) of stroke was 0.60 [95% confidence interval (CI): 0.42 - 0.85] for subjects who drank tea compared to those who did not. Increased amount of tea consumption per month was associated with decreased stroke prevalence. The association for tea consumption over 150 gram per month and stroke was statistically significant (P < 0.05) with an OR value of 0.56 (95% CI: 0.36 - 0.89). Analytical results indicated that the OR value was 0.24 (95% CI: 0.06 - 1.01) for black tea and other tea (P = 0.05). The OR value was 0.35 (95% CI: 0.18 - 0.72) for green tea (P < 0.01), and 0.75 (95% CI: 0.51 - 1.11) for jasmine tea (P > 0.05). CONCLUSION: Tea drinking was independently associated with prevalence of stroke which might play a role in the prevention of the disease.

Adult↗
PubMed2004

[The green tea, a good choice for cardiovascular disease prevention?].

Tea (Camellia sinensis) has been used for centuries as a medical drink. Around two-thirds of the world's population drink tea. It is originated from southern China and entensive cultivated in Asia and in central African countries. Tea can be grouped into three main types, black, oolong, and green tea. Green tea is not fermented and is a major beverage consumed in Asian countries. Green tea is produced from freshly harvest leaves of the tea plant and they contain water, proteins, carbohydrates, minerals, vitamins and polyphenols of the flavonoid type. The major flavonoids in green tea are catechins which constitute about one third of its total dry weight. The major catechin present is epigallocatechin gallate (>50%). New data have increased the interest in green tea or its catechins and its role in treatment of cardiovascular disease (CHD) risk factors. The aim of the present paper is to review some studies that have found a relationship between green tea and CHD risk factors. From some of them it can be summarized that of green tea and its catechins consumptions (i) decrease body weight by interfering within the sympathoadrenal system and fatty acid synthesis, (ii) decrease cholesterol absorption and plasma levels, (iii) have strong free radical-scavenging activity inhibiting LDL oxidation, (iv) reduce the adhesion molecule expression, (v) have antitrombotic activities by inhibiting platelet aggregation and (vi) decrease systolic and diastolic blood pressures. The positive effects found suggest that a daily intake of 7 cups of green tea (3.5 g catechins) is a good choose for CHD prevention; however, it is still necessary more studies to check the action of the green tea and its catechins in humans in order to recommended its use in the general population or only in target subjects.

Antioxidants↗
PubMed1992

Inhibitory effect of green tea in the drinking water on tumorigenesis by ultraviolet light and 12-O-tetradecanoylphorbol-13-acetate in the skin of SKH-1 mice.

Green tea was prepared by extracting 12.5 g of green tea leaves twice with 500 ml of boiling water, and the extracts were combined. This 1.25% green tea extract (1.25 g of tea leaves/100 ml of water) contained 4.69 mg of green tea extract solids per ml and was similar in composition to some green tea beverages consumed by humans. A 2.5% green tea extract (2.5 g of tea leaves/100 ml of water) was prepared similarly. Treatment of female SKH-1 mice with 180 mJ/cm2 of ultraviolet B light (UVB) once daily for 7 days resulted in red sunburn lesions of the skin. The intensity of red color and area of these lesions were inhibited in a dose-dependent fashion by the administration of 1.25 or 2.5% green tea extract as the sole source of drinking water before and during UVB treatment. Treatment of female SKH-1 mice with 180 mJ/cm2 of UVB once daily for 10 days followed 1 wk later by twice weekly application of 12-O-tetradecanoylphorbol-13-acetate for 25 wk resulted in the development of skin tumors. The formation of skin tumors was inhibited by administration of 1.25% green tea extract as the sole source of drinking water prior to and during the 10 days of UVB treatment and for 1 wk after UVB treatment. In additional experiments, female SKH-1 mice were treated with 200 nmol of 7,12-dimethylbenz(a)anthracene followed 3 wk later by irradiation with 180, 60, or 30 mJ/cm2 of UVB twice weekly for 30 wk. UVB-induced formation of skin tumors and increased spleen size were inhibited by administration of 1.25% green tea extract as the sole source of drinking water prior to and during the 30 wk of UVB treatment. In these experiments, treatment of the animals with the green tea extract not only decreased the number of skin tumors but also decreased substantially the size of the tumors. In additional studies, SKH-1 mice were initiated by topical application of 200 nmol of 7,12-dimethylbenz(a)anthracene followed by twice weekly application of 12-O-tetradecanoylphorbol-13-acetate for 25 wk. Administration of 1.25% green tea extract as the sole source of drinking water during promotion with 12-O-tetradecanoylphorbol-13-acetate reduced the number and incidence of skin tumors.

9,10-Dimethyl-1,2-benzanthracene↗