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PubMed2003

Effects of green tea on carcinogen-induced hepatic CYP1As in C57BL/6 mice.

Green tea (GT) drinking showed chemopreventive effects on various cancers. In addition, inhibition of CYP1A activity by green tea components--polyphenols--has been suggested as a chemoprevention against carcinogens that were bioactivated by CYP1As. Therefore, any changes in hepatic CYP1As may be considered as a biomarker for GT chemoprevention and clarify whether whole GT is chemopreventive for the population who are exposed to CYP1A specifically-bioactivated carcinogens. In this study, we investigated the changes in CYP1A levels by pre- and concurrent GT drinking against a CYP1A-inducing carcinogen, 3-methylcholanthrene (MC), in aryl hydrocarbon receptor responsive C57 BL/6 mice. We found that GT drinking itself induced hepatic CYP1As and enhanced MC-induced ethoxyresorufin-O-demethylase (EROD) activity (P<0.05). However, our studies of CYP1A monoclonal antibody and western blots revealed that the enhanced hepatic EROD activity by GT did not come from CYP1As. Therefore, our results suggest that GT may work to biotransform CYP1A inducing carcinogens into non-carcinogenic metabolites by modulation of other microsomal enzymes rather than CYP1As. In addition, the mechanism of GT chemoprevention may be different from that of GT components, such as polyphenols that reduce CYP1As activity.

Administration, Oral↗
PubMed1998

Conditioned flavour preference negatively reinforced by caffeine in human volunteers.

This study examined whether 100 mg caffeine could reinforce preference for the flavour of a novel drink in moderate caffeine users, both after overnight caffeine abstinence and 2 h after receiving 100 mg caffeine, using a two-stage between-groups procedure with 36 volunteers. In the first stage, liking for a test drink (fruit tea) was assessed at breakfast following overnight caffeine abstinence, with half the subjects receiving caffeine. Liking for the tea increased significantly over four trials for subjects receiving caffeine, and decreased significantly in those without caffeine. These effects were greatest in subjects who rated the drink as highly novel. In stage two, subjects evaluated a second drink (fruit-juice) 2 h after receiving the tea, and again half the subjects received caffeine Those subjects who received caffeine in stage two but not stage one showed a significant increase in liking for the fruit-juice over the 4 test days, whereas subjects who did not receive caffeine at either stage showed a progressive decrease in liking for this drink. In contrast, no significant change in liking for the fruit-juice was seen at stage two for subjects who had received caffeine in stage one, regardless of the presence or absence of caffeine at stage two. Caffeine at breakfast increased ratings of energetic and lively, and energetic ratings also increased following caffeine in the fruit-juice in subjects who had not had caffeine at breakfast. Overall, these data are consistent with a negative reinforcement model of caffeine reinforcement, and demonstrate further the utility of the conditioned flavour preference method for evaluating reinforcing effects of drugs in humans.

Adult↗
PubMed1992

Inhibitory effect of green tea on the growth of established skin papillomas in mice.

In 10 separate experiments, mice with established chemically induced or UV light-induced skin papillomas were treated continuously with green tea in the drinking water or with i.p. injections of a green tea polyphenol fraction or (-)-epigallocatechin gallate three times a week for 4-10 weeks. Partial tumor regression or > 90% inhibition of tumor growth, as measured by changes in tumor volume per mouse, was observed in 5 experiments, and marked inhibition of tumor growth (46-89%) was observed in 5 additional experiments. Treatment of the mice with green tea or green tea constituents had an inhibitory effect on body weight increases in several but not all of the studies. Examination of the data from all ten experiments revealed that complete tumor regression occurred in 14 of 346 papilloma-bearing mice (4%) that were treated with green tea in the drinking water or with i.p. injections of green tea constituents, whereas none of the 220 papilloma-bearing control mice treated with only vehicle exhibited complete tumor regression. These observations indicate that oral administration of green tea, i.p. administration of a green tea polyphenol fraction, or i.p. administration of (-)-epigallocatechin gallate inhibited the growth and/or caused the regression of established experimentally induced skin papillomas.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Modulation of cancer chemotherapy by green tea.

Biochemical modulation has played an important role in the development of cancer chemotherapy. We have directed our attention to the intake of common beverages and investigated the effects of green tea and tea components on the antitumor activity of doxorubicin. We carried out the combined treatment of toxorubicin and green tea on Ehrlich ascites carcinoma tumor-bearing mice. The oral administration of green tea enhanced 2.5-fold the inhibitory effects of doxorubicin on tumor growth. The Doxorubicin concentration in the tumor was increased by the combination of green tea with doxorubicin. In contrast, the increase in doxorubicin concentration was not observed in normal tissues after green tea combination. Furthermore, the enhancement of antitumor activity of doxorubicin induced by green tea was observed in M5076 ovarian sarcoma, which has low sensitivity to doxorubicin. These results suggest that drinking green tea can encourage cancer chemotherapy and may improve the quality of life of clinical patients.

Animals↗
PubMed1994

Caffeinated coffee and tea intake and its relationship to cigarette smoking: an analysis of the Second National Health and Nutrition Examination Survey (NHANES II).

Recent studies have shown that smokers' intake of caffeine is higher than nonsmokers. This investigation evaluated the relationships between smoking status and self-reported caffeine intake from both coffee and tea. Subjects were adults who participated in the Second National Health and Nutrition Examination Survey (NHANES II). Results indicated that subjects who ingested caffeine from tea were more likely to be female, less educated, younger, non-Caucasian, and lighter drinkers. In contrast, those who ingested caffeine from coffee were more likely to be older, Caucasian, heavier drinkers, and have higher incomes. Smokers were not more likely to drink caffeinated tea. In contrast, smokers were much more likely to drink caffeinated coffee, and a dose-response relationship between caffeine from coffee and smoking intake was observed. These results clarify the relationship between smoking and caffeine intake. Implications for intervention efforts are discussed.

Adolescent↗
PubMed1989

Crude tea extracts decrease the mutagenic activity of N-methyl-N'-nitro-N-nitrosoguanidine in vitro and in intragastric tract of rats.

The effects of tea extracts and their ingredients, catechins and L-ascorbic acid (AsA), on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined in vitro and in the stomachs of rats using E. coli WP2 and S. typhimurium TA100. The extracts of green tea and black tea leaves decreased the mutagenic activity of MNNG to E. coli WP2 in vitro in a desmutagenic manner. Catechins such as (-)-epigallocatechin from green tea leaves and the low-molecular-weight tannin fraction isolated from black tea extract with HP-20 resin also exhibited inhibitory effects against the mutagenic activity of MNNG. A desmutagenic effect of AsA on MNNG-induced mutagenicity was observed depending on the dose, though it was complicated. The effects were also demonstrated in the stomachs of rats by assaying the bacterial mutagenic in vitro; the tea extracts previously given orally to rats reduced the mutagenic activity of MNNG remarkably, though simultaneous administration showed less effect. The effectiveness of tea extracts for the decrease of MNNG-induced mutagenesis in vitro and in vivo suggests that the habitual drinking of tea may reduce the tumor-initiating potency of MNNG-type nitrosoureido compounds if they are formed in the stomach.

Animals↗
PubMed2000

[Environmental fluorine level in Tibet].

The concentration of fluorine in water, soil, fuel, food, vegetable and tea in Tibetan habitats with different environmental characteristic were measured by ion-specific electrode potentiometer. The results showed that the fluorine concentration in water, soil, fuel, food vegetable, butter tea and Zanba both of them were made from brick teas was 0.06 mg.L-1, 0.45 mg.kg-1, 0.10 mg.kg-1, 0.06-0.33 mg.kg-1, 3.09 mg.L-1 and 3.61 mg.kg-1, respectively. The water-soluble fluorine content in brick tea which came from Sichuan and Yunnan Provinces reached up to 533.89-617.32 mg.kg-1. It is suggested that drinking brick tea may induce fluorosis in Tibetan habitats.

Environment↗
PubMed2003

Urinary concentrations of morphine after the administration of herbal teas containing Papaveris fructus in relation to doping analysis.

A quantitative method for the analysis of morphine in human urine in the concentration range between 0.25 and 2 microg/ml is described and validated. Morphine was determined after enzymatic hydrolysis of the urine. After liquid-liquid extraction with dichloromethane-methanol (9:1) at pH 9.5, morphine was derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA) and analyzed with GC-MS (full scan). The limit of quantification of the method was 0.25 microg/ml. Two Papaveris fructus containing herbal teas were administered to five male volunteers and urine samples were taken quantitatively during the first 12 h after the administration. The morphine concentration in the tea was 10.4 and 31.5 microg/ml, respectively. Morphine was detected in the urine of all volunteers by 1 h after drinking the tea. Maximum morphine concentrations, 4.3 and 7.4 microg/ml, respectively, were obtained 4-6 h after administration. Doping positive urine samples were delivered for 1-9 h.

Adult↗
PubMed1992

Tea consumption. relationship to cholesterol, blood pressure, and coronary and total mortality.

BACKGROUND AND METHODS: The relation of tea to cholesterol, systolic blood pressure, and mortality from coronary heart disease and all causes was studied in 9,856 men and 10,233 women without history of cardiovascular disease or diabetes. All men and women 35-49 years of age from the county of Oppland (Norway) were invited to participate; the attendance rate was 90%. RESULTS: Mean serum cholesterol decreased with increasing tea consumption, the linear trend coefficient corresponded to a difference of 0.24 mmol/liter (9.3 mg/dl) in men and 0.15 mmol/liter (5.8 mg/dl) in women between drinkers of less than one cup and those of five or more cups/day, when other risk factors were taken into account. Systolic blood pressure was inversely related to tea with a difference between the same two tea groups of 2.1 mm in men and 3.5 mm in women. Altogether 396 men and 237 women died from all causes, and of these 141 and 18, respectively, died from coronary heart disease during the 12-year follow-up period. The mortality rate was higher (not statistically significant) among persons drinking no tea or less than one cup compared with persons drinking one or more cups/day. This applies to men and women and to coronary heart disease and all-cause mortality. For men, the relative risk (one or more versus less than one cup) for coronary death from Cox regression was 0.64 (95% CI:0.38, 1.07).

Adult↗
PubMed2001

A new function of green tea: prevention of lifestyle-related diseases.

In the normal human life span, there occur lifestyle-related diseases that may be preventable with nontoxic agents. This paper deals with the preventive activity of green tea in some lifestyle-related diseases. Green tea is one of the most practical cancer preventives, as we have shown in various in vitro and in vivo experiments, along with epidemiological studies. Among various biological effects of green tea, we have focused on its inhibitory effect on TNF-alpha gene expression mediated through inhibition of NF-kappaB and AP-1 activation. Based on our recent results with TNF-alpha-deficient mice, TNF-alpha is an endogenous tumor promoter. TNF-alpha is also known to be a central mediator in chronic inflammatory diseases such as rheumatoid arthritis and multiple sclerosis. We therefore hypothesized that green tea might be a preventive agent for chronic inflammatory diseases. To test this hypothesis, TNF-alpha transgenic mice, which overexpress TNF-alpha only in the lungs, were examined. The TNF-alpha transgenic mouse is an animal model of human idiopathic pulmonary fibrosis which also frequently develops lung cancer. Expressions of TNF-alpha and IL-6 were inhibited in the lungs of these mice after treatment with green tea in drinking water for 4 months. In addition, judging from the results of a prospective cohort study in Saitama Prefecture, Japan, green tea helps to prevent cardiovascular disease. In this study, a decreased relative risk of death from cardiovascular disease was found for people consuming over 10 cups of green tea a day, and green tea also had life-prolonging effects on cumulative survival. These data suggest that green tea has preventive effects on both chronic inflammatory diseases and lifestyle-related diseases (including cardiovascular disease and cancer), resulting in prolongation of life span.

Animals↗
PubMed1993

Social transmission of flavored tea preferences: facilitation by a vasopressin analog and oxytocin.

Social transmission of information was tested in a procedure in which a rat (Observer) could demonstrate preference for a flavored tea as drinking solution that a con-specific (Demonstrator) had consumed just prior to a period of social interaction between the two animals. The cue in this procedure, probably olfactory in nature, was remembered for a relatively short period of time. It was prolonged when the Observers were treated with dresglycinamide[Arg8]-vasopressin (DGAVP) or oxytocin immediately after the encounter with the Demonstrator. DGAVP was effective after the injection of 15 micrograms.kg-1 but not of 1.5 ng.kg-1. Oxytocin induced the effect in doses ranging from 1.5 ng.kg-1 to 15 micrograms.kg-1. A dose of 0.15 ng.kg-1 was inactive. The influence of the peptides was cue specific. It is concluded that DGAVP and oxytocin facilitate social transmission of information, as previously found for social recognition.

Animals↗
PubMed2000

Consumption of black tea elicits an increase in plasma antioxidant potential in humans.

Epidemiological studies suggest that the consumption of tea flavonoids may be associated with reduced risk of coronary heart disease, stroke and cancer-related deaths. The flavonoids are polyphenols which in vitro exhibit antioxidant properties. Tea flavonoids are known to be rapidly absorbed into the circulation following oral ingestion. To date few studies have demonstrated that these bioavailable flavonoids retain antioxidant properties in vivo. Nine healthy subjects aged between 26 and 59 (one male and eight females) took part in 3 study days. On 1 day subjects consumed no tea and on the other 2 days subjects drank either black tea with milk, or black tea alone at hourly intervals between 9.00 a.m. and 14.00 p.m. Blood was sampled at 9.00 a.m. and at 12.00 p.m. and 15.00 p.m. The antioxidant potential of plasma was determined using the ferric reducing antioxidant power (FRAP) assay. Subjects consuming no tea exhibited no significant change in FRAP across the 6 hours of the study day. Similarly consumption of milky tea produced no change in FRAP between 9.00 a.m. and 12.00 p.m. and the 50% increase in FRAP noted between 12.00 p.m. and 15.00 p.m. was not statistically significant. When the subjects consumed black tea without milk FRAP increased by 65% between 9.00 a.m. and 12.00 p.m. (P = 0.02) and at 15.00 p.m. was 76% higher than at 9.00 a.m. (P = 0.002). Heavy consumption of black tea thus appears to elevate circulating antioxidant potentials in vivo. This is an effect which appears to be totally negated by the drinking of tea with milk. Although tea may thus represent an important source of dietary antioxidants in many societies, the role of tea in reducing risk of major disease states needs to be investigated in more detail.

Adult↗
PubMed2001

The influence of green tea on the activity of proteases and their inhibitors in plasma of rats after ethanol treatment.

Ethanol oxidation in the liver is accompanied by formation of acetaldehyde and free radicals. These compounds can react with biologically active proteins, including proteolytic enzymes and their inhibitors. The aim of this paper was to determine the influence of green tea on the activity of cathepsin G and elastase and their inhibitors such as alpha-1-antitrypsin and alpha-2-macroglobulin, total antioxidant status and lipid peroxidation in plasma of young rats chronically intoxication with ethanol. The activity of cathepsin G and elastase was increased, while the activity of their inhibitors was reduced after ethanol treatment. AT the same time, the total antioxidant status was significantly decreased while lipid peroxidation measured as malondialdehyde and 4-hydroxynonenal was significantly increased. Giving green tea to rats did not change the proteases and their inhibitors activity, but significantly increased total antioxidant status and decreased lipid peroxidation. Drinking green tea with ethanol partially prevents the changes observed after ethanol intoxication.

Alcoholism↗
PubMed2003

Effect of green tea in the prevention and reversal of fasting-induced intestinal mucosal damage.

OBJECTIVE: Epidemiologic studies have suggested that high consumption of green tea protects against the development of chronic active gastritis and decreases the risk of stomach cancer. The effect of green tea on the intestinal mucosa was not studied previously, so we examined the effects of green tea on the intestinal mucosa of fasting rats in a controlled experimental setting. METHODS: Two sets of experiments were performed. In the recovery set, rats were fasted for 3 d, after which they were allowed free access to water, black tea, green tea, or vitamin E for 7 d. On day 8, the animals were killed, and small bowels were removed for histologic examination. In the pretreatment set, rats were allowed a normal diet, but the water supply was replaced with green tea, black tea, or vitamin E for 14 d. They were subsequently fasted for 3 d. On day 4, the rats were killed, and small bowels were removed for histologic examination. RESULTS: In the recovery set, fasting for 3 d caused shortening of villi, atrophy, and fragmentation of mucosal villous architecture, with a significant (P < 0.0001) reduction in the length and surface area of the villi. Ingestion of green tea and, to a lesser extent, vitamin E for 7 d helped in the recovery of villi to normal. In the pretreatment set, drinking green tea, black tea, or vitamin E for 14 d before fasting protected intestinal mucosa from damage. CONCLUSION: The mucosal and villous atrophy induced by fasting was reverted to normal by the ingestion of green tea and, to a lesser extent, vitamin E. Black tea ingestion had no effect. In addition, ingestion of black tea, green tea, and vitamin E before fasting protected the intestinal mucosa against atrophy.

Animals↗
PubMed2006

Green tea and the prevention of breast cancer: a case-control study in Southeast China.

Breast cancer is the most common malignancy in women worldwide. Tea has anticarcinogenic effects against breast cancer in experimental studies. However, epidemiologic evidence that tea protects against breast cancer has been inconsistent. A case-control study was conducted in Southeast China between 2004 and 2005. The incidence cases were 1009 female patients aged 20-87 years with histologically confirmed breast cancer. The 1009 age-matched controls were healthy women randomly recruited from breast disease clinics. Information on duration, frequency, quantity, preparation, type of tea consumption, diet and lifestyle were collected by face-to-face interview using a validated and reliable questionnaire. Conditional logistic regression analyses were used to estimate odds ratios (ORs) and associated 95% confidence intervals. Compared with non-tea drinkers, green tea drinkers tended to reside in urban, have better education and have higher consumption of coffee, alcohol, soy, vegetables and fruits. After adjusting established and potential confounders, green tea consumption was associated with a reduced risk of breast cancer. The ORs were 0.87 (0.73-1.04) in women consuming 1-249 g of dried green tea leaves per annum, 0.68 (0.54-0.86) for 250-499 g per annum, 0.59 (0.45-0.77) for 500-749 g per annum and 0.61 (0.48-0.78) for >or=750 g per annum, with a statistically significant test for trend (P < 0.001). Similar dose-response relationships were observed for duration of drinking green tea, number of cups consumed and new batches prepared per day. We conclude that regular consumption of green tea can protect against breast cancer. More research to closely examine the relationship between tea consumption and breast cancer risk is warranted.

Adult↗
PubMed2000

Acute effects of ingestion of black and green tea on lipoprotein oxidation.

BACKGROUND: Tea has been associated with a reduced risk of cardiovascular disease. One proposed mechanism of this risk reduction involves inhibition of lipoprotein oxidation in vivo by antioxidant polyphenolic compounds derived from tea. However, controlled interventions uniformly failed to show that ingestion of tea can inhibit LDL oxidation ex vivo. The absence of effects in previous studies may be due to the isolation of LDL particles from polyphenolic compounds that are present in the aqueous phase of serum. OBJECTIVE: The objective of this study was to examine the acute effects of ingestion of black and green tea on ex vivo Cu(2+)-induced lipoprotein oxidation without prior isolation of lipoproteins from serum. DESIGN: The acute effects of 4 hot drinks-green tea and black tea (each at a dose equivalent to 4 standard cups), water matched to the teas for caffeine content, and water-were assessed in 20 healthy men by using a Latin-square design. The lag time to lipoprotein diene formation, slope of the propagation phase of the oxidation curve, and area under the oxidation curve were calculated. Urinary concentrations of 4-O-methylgallic acid were used as a marker of uptake and metabolism of polyphenolic compounds from tea. RESULTS: Significant increases in urinary 4-O-methylgallic acid for black and green tea (P < 0. 0001) were observed. Caffeine did not significantly influence lipoprotein oxidation. Compared with the water control, there was a greater lag time for black tea (5.4 +/- 2.9 min; P = 0.05) that was of borderline significance and a similar trend for green tea (4.4 +/- 2.8 min; P = 0.17). Slope and area under the oxidation curve were not altered. CONCLUSION: Black tea has a mild acute effect on ex vivo lipoprotein oxidation in human serum. 2000;71:-7.

Adult↗
PubMed2002

Beverage choices of young females: changes and impact on nutrient intakes.

OBJECTIVE: To examine trends in beverage consumption and evaluate the impact of beverage choices on the nutrient intakes of females ages 12 to 19 years. DESIGN: Dietary intake data from the USDA's Nationwide Food Consumption Surveys, including the Continuing Survey of Food Intakes by Individuals (CSFII), were assessed for trends in beverage consumption. The CSFII 1994-1996 data was used to examine the diets of young females grouped based on their milk and soda consumption status. Mean energy, nutrient, and beverage intakes were compared. SUBJECTS: Females with complete dietary intake information on Day 1 of the survey were included in the study. There were 732 females ages 12 to 19 years in the CSFII 1994-1996. Statistical Analysis Percentages of females consuming specific beverages were estimated. Pairwise mean comparisons were made between groups based on milk and soda consumption status. RESULTS: Milk intakes decreased by 36% whereas that of sodas and fruit drinks almost doubled from the late 1970s to the mid 1990s. The CSFII 1994-1996 data showed that between ages 12 and 19 years, intakes of fruit juices, soda, tea, fruit drinks, and alcoholic beverages either increased or remained relatively steady, while milk intakes decreased with an increase in age. At age 12 years, 78% drank milk and had the lowest soda intake (276g), while at age 19-years, only 36% drank milk and drank a high amount of soda (423g). Those who did not drink milk had inadequate intakes of vitamin A, folate, calcium, phosphorus, and magnesium. APPLICATION: A rapid decrease in milk intake during the early adolescent years indicates a need for interventions at this age. Dietitians should identify barriers to drinking milk and recommend strategies for including appropriate food sources to increase calcium intakes during growing years. Nutrition educators should provide parents of adolescent children with ideas for ensuring the adequacy of their children's calcium intakes. J Am Diet Assoc. 2002; 102: 1234-1239.

Adolescent↗
PubMed2001

Tea catechins prevent the development of atherosclerosis in apoprotein E-deficient mice.

Green tea contains various antioxidative flavan-3ols (tea catechins), such as (-)-epigallocatechin gallate (EGCg, the major catechin), which exert potent inhibitory effects on LDL oxidation in vitro and ex vivo in humans. In this study, the antiatherogenic effects of tea catechins were examined in atherosclerosis-susceptible C57BL/6J, apoprotein (apo)E-deficient mice. Male apoE-deficient mice (10 wk old) were fed an atherogenic diet for 14 wk; during that time, one group (tea) was supplied drinking water supplemented with green tea extract (0.8 g/L), and another group (control) was offered the vehicle only. The tea extract consisted of the following (g/100 g): EGCg, 58.4; (-)-epigallocatechin (EGC), 11.7; (-)-epicatechin (EC), 6.6; (-)-gallocatechingallate (GCg), 1.6; (-)-epicatechin gallate (ECg), 0.5; and caffeine, 0.4. The estimated actual intake of tea catechin was 1.7 mg/(d. mouse). Tea ingestion did not influence plasma cholesterol or triglyceride concentrations. Plasma lipid peroxides were reduced in the tea group at wk 8, suggesting that the in vivo oxidative state is improved by tea ingestion. Atheromatous areas in the aorta from the arch to the femoral bifurcation and aortic weights were both significantly attenuated by 23% in the tea group compared with the control group. Aortic cholesterol and triglyceride contents were 27 and 50% lower, respectively, in the tea group than in the control group. These results suggest that chronic ingestion of tea extract prevents the development of atherosclerosis without changing the plasma lipid level in apoE-deficient mice, probably through the potent antioxidative activity of the tea.

Animals↗