Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Tea”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1999

Mechanistic findings of green tea as cancer preventive for humans.

Based on our initial work with green tea, in which repeated topical applications of (-)-epigallocatechin gallate (EGCG), the main green tea polyphenol, inhibited tumor promotion in a two-stage carcinogenesis experiment on mouse skin (Phytother Res 1, 44-47, 1987), numerous scientists have since provided so much additional evidence of the benefits of drinking green tea that it is now an acknowledged cancer preventive in Japan, and will possibly soon be recognized as such in other countries. Our work has so far produced several important results with EGCG and green tea: a wide range of target organs in animal experiments for cancer prevention, wide bioavailability of 3H-EGCG in various organs of mice, delayed cancer onset of patients with a history of consuming over 10 cups of green tea per day, and absence of any severe adverse effects among volunteers who took 15 green tea tablets per day (2.25 g green tea extracts, 337.5 mg EGCG, and 135 mg caffeine) for 6 months. This paper introduces three new findings: 1) EGCG interacted with the phospholipid bilayer membrane resulting in confirmation of the sealing effect of EGCG; 2) EGCG inhibited TNF-alpha gene expression in the cells and TNF-alpha release from the cells; 3) high consumption of green tea was closely associated with decreased numbers of axillary lymph node metastases among premenopausal Stage I and II breast cancer patients, and with increased expression of progesterone and estrogen receptors among postmenopausal ones. These results provide new insights into our understanding of the mechanisms of action of tea polyphenols and green tea extract as a cancer preventive.

Antineoplastic Agents↗
PubMed1991

The effect of tea on iron and aluminium metabolism in the rat.

Weanling male Wistar rats were fed for 28 d on a semi-synthetic diet containing normal (38 micrograms/g) or low (9 micrograms/g) levels of iron. They were given water or tea infusion (20 g leaves/l water) to drink. Two further groups were given a normal- or low-Fe diet containing added tea leaves (20 g/kg diet). At the end of the study period, all rats given the low-Fe diet were severely anaemic, as assessed by haemoglobin, packed cell volume and liver Fe. Those given tea or the diet with added tea leaves showed a greater degree of Fe depletion. The blood and liver aluminium levels were not increased as a result of consuming tea or tea leaves, despite the higher Al intakes. Fe deficiency per se had no effect on Al absorption or retention from tea. It was concluded that the Al in tea was very poorly absorbed but that tea, either in the form of an infusion or as tea leaves, had an adverse effect on Fe status.

Aluminum↗
PubMed2001

Tea consumption and risk of cancer of the colon and rectum.

The association between tea consumption and risk of colon and rectal cancers was investigated in a population-based case-control study conducted in Iowa (United States). Colon (n = 685) and rectal (n = 655) cancer cases age 40-85 yr were identified through the Iowa Surveillance, Epidemiology, and End Results (SEER) Cancer Registry (86% response rate); controls (n = 2,434) were frequency matched by sex and 5-yr age group (80% response rate). The usual adult consumption of tea (hot and iced), along with other information including dietary data, was self-reported using a mailed questionnaire. Total tea consumption (cups/day) was categorized as none (reference category), low (< 3.1), medium (3.1-5.0), and high (> 5.0), with cut points for tea consumers based on the 75th and 90th percentiles of use among controls. Unconditional logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals. There was no association between total tea consumption and colon cancer (ORs = 1.0, 1.1, 1.3, and 0.7) or rectal cancer (ORs = 1.0, 0.9, 1.4, and 1.0) after adjustment for age, sex, education, physical activity, smoking history, and intake of coffee, fiber, and fruits and vegetables. Results were similar when hot tea and iced tea were evaluated individually. Further adjustment for other colorectal cancer risk factors did not alter these results. There was no association with proximal or distal colon cancer. There was also no interaction between tea consumption and any of the dietary variables or total fluid on risk of colon or rectal cancer, with the exception of a suggestive positive association between an increasing frequency of tea consumption and colon cancer risk among current smokers (multivariate ORs = 1.0, 1.4, 2.0, and 1.8; P for trend = 0.1), but not among never smokers (multivariate ORs = 1.0, 1.0, 1.1, and 0.4; P for trend = 0.3). These data do not support an overall association, either positive or negative, between tea consumption and risk of colon or rectal cancer in this Mid-western US population.

Adult↗
PubMed1998

Protection by tea against UV-A + B-induced skin cancers in hairless mice.

Consumption of tea, especially green tea, has been shown to reduce the incidence of ultraviolet (UV)-related skin tumors in hairless mice. Because milk is added to much of the tea consumed in Western cultures, we have studied the effects of including milk in the tea consumed by hairless mice receiving simulated solar radiation. Under these conditions, mice consuming tea with 10% whole milk had 30% fewer papillomas, 50% fewer tumors, and 55% smaller lesions than mice consuming water. Mice consuming tea alone had fewer papillomas and tumors than mice consuming tea with milk; however, the difference in area affected was not statistically significant. In separate experiments, there was a significant dose response to black tea as a preventive against UV-related skin lesions, and also consumption of black tea was associated with a small but significant reduction in the incidence of papillomas in mice previously exposed to UV radiation. The results of these studies demonstrate that, in hairless mice, black tea can inhibit the formation of UV-induced skin tumors in a dose-dependent manner and, even with the addition of milk, can still inhibit the growth of UV-related skin tumors.

Animals↗
PubMedDate not supplied

Inhibition of lung tumorigenesis by tea.

Tea and tea constituents have been shown by different investigators to inhibit lung tumorigenesis in different animal model systems. This includes lung tumorigenesis in A/J mice induced by 4-(methylnitrosamino)-1-(3pyridyl)-1-butanone (NNK), N-nitrosodiethylamine, benzo[a]pyrene, N-nitrosomethylurea, or cisplatin. Inhibition of lung tumorigenesis has also been demonstrated in C3H mice treated with N-nitrosodiethylamine. In most of these experiments, reduction in tumor number and tumor size has been observed in the tea-treated group, and in some experiments, decreased tumor incidence has also been observed. The green tea constituent, epigallocatechin-3-gallate (EGCG), and the black tea constituent, theaflavins, have also been shown to be effective. Black tea preparations have been shown to reduce the incidence and number of spontaneously generated lung adenocarcinomas and rhabdomyosarcoma in A/J mice, as well as inhibit the progression of lung adenoma to adenocarcinoma. The mechanisms for the inhibitory action have not been well elucidated. It may be related to the antiproliferative, proapoptotic, and antiangiogenic activities of tea constituents that have been demonstrated in some experiments. These activities may be a result of the inhibition of key protein kinases involved in signal transduction and cell cycle regulation. Tea catechins, such as EGCG, have been suggested to be the effective components. However, a study suggests that caffeine is the key effective constituent for the inhibitory activity of lung tumorigenesis in Fisher 344 rats by black tea. In many of the experiments, tea consumption resulted in the reduction of body fat and body weight; these factors may also contribute to the inhibition of tumorigenesis.

Adenocarcinoma↗
PubMed2006

Tea consumption and infarct-related ventricular arrhythmias: the determinants of myocardial infarction onset study.

BACKGROUND: Tea consumption is associated with lower post-infarct mortality among patients with acute myocardial infarction. We previously found preliminary evidence that tea consumption may also be associated with lower risk of infarct-related ventricular arrhythmias. METHODS: Between 1989 and 1996, 3882 subjects with AMI were enrolled in the two phases of the Determinants of Myocardial Infarction Onset Study a median of four days after admission. Trained interviewers assessed self-reported usual tea and coffee consumption during the year prior to infarction with a standardized questionnaire. We examined the prevalence of ventricular arrhythmias in the two phases of the study separately and together. RESULTS: Among the 1912 patients with complete information in the first phase, the prevalence of ventricular arrhythmias was 16% among abstainers from tea, 11% among moderate tea drinkers (<14 cups per week), and 14% among heavier tea drinkers (> or =14 cups per week) (p homogeneity = 0.03). Among the 1791 patients with comparable information in the second phase, the corresponding prevalence rates were 11%, 8%, and 8%, respectively (p = 0.06). When the phases were combined, the adjusted odds ratios for VA were 0.7 (95% confidence interval, 0.6-0.9) among moderate tea drinkers and 0.9 (95% confidence interval, 0.7-1.2) among heavier tea drinkers. The findings were of similar direction for both ventricular tachycardia and fibrillation. In contrast, there was higher risk of VA with increasing coffee intake (odds ratio for >14 cups per week 1.3; 95% confidence interval, 1.0-1.7; p trend 0.02). CONCLUSIONS: Moderate tea intake is associated with a lower prevalence, and higher coffee intake with a slightly higher prevalence, of ventricular arrhythmias among patients hospitalized with acute myocardial infarction. If the association with tea intake is confirmed, it may suggest new approaches to prevention of ischemia-related arrhythmias.

Analysis of Variance↗
PubMedDate not supplied

Prevention of carcinogenesis by tea polyphenols.

Tea, an extract of the leaves of the plant Camellia sinensis, has been considered a medicine and healthful beverage for ages. The beneficial effects of tea are thought to be due to its polyphenolic components. Herein, we discuss the present status of tea as a possible cancer chemopreventive agent, covering basic chemistry and biochemical activity of tea, pharmacokinetics of major tea components, studies in animal and cell lines, epidemiological investigations, and future challenges. Tea is one of the few chemopreventive agents known to have protective effects at different stages of the carcinogenic process. Tea constituents may inhibit this process by modulating signal transduction pathways leading to the inhibition of cell proliferation and transformation and enhancement of apoptosis. These activities may or may not be due to the antioxidative activity of tea polyphenols. The bioavailability and tissue levels of tea polyphenols is a key topic to be studied in order to understand the mechanisms of action of tea and its possible protection against cancer in humans.

Animals↗
PubMed2000

Tea polyphenols: prevention of cancer and optimizing health.

The tea plant Camellia sinesis is cultivated in >30 countries. Epidemiologic observations and laboratory studies have indicated that polyphenolic compounds present in tea may reduce the risk of a variety of illnesses, including cancer and coronary heart disease. Most studies involved green tea, however; only a few evaluated black tea. Results from studies in rats, mice, and hamsters showed that tea consumption protects against lung, forestomach, esophagus, duodenum, pancreas, liver, breast, colon, and skin cancers induced by chemical carcinogens. Other studies showed the preventive effect of green tea consumption against atherosclerosis and coronary heart disease, high blood cholesterol concentrations, and high blood pressure. Because the epidemiologic studies and research findings in laboratory animals have shown the chemopreventive potential of tea polyphenols in cancer, the usefulness of tea polyphenols for humans should be evaluated in clinical trials. One such phase 1 clinical trial is currently under way at the MD Anderson Cancer Center in collaboration with Memorial Sloan-Kettering Cancer Center. This study will examine the safety and possible efficacy of consuming the equivalent of > or =10 cups (> or =2.4 L) of green tea per day. The usefulness of tea polyphenols may be extended by combining them with other consumer products such as food items and vitamin supplements. This "designer-item" approach may be useful for human populations, but it requires further study.

Animals↗
PubMed1998

Inhibition of growth and induction of apoptosis in human cancer cell lines by tea polyphenols.

In order to study the biological activities of tea preparations and purified tea polyphenols, their growth inhibitory effects were investigated using four human cancer cell lines. Growth inhibition was measured by [3H]thymidine incorporation after 48 h of treatment. The green tea catechins (-)-epigallocatechin-3-gallate (EGCG) and (-)-epigallocatechin (EGC) displayed strong growth inhibitory effects against lung tumor cell lines H661 and H1299, with estimated IC50 values of 22 microM, but were less effective against lung cancer cell line H441 and colon cancer cell line HT-29 with IC50 values 2- to 3-fold higher. (-)-Epicatechin-3-gallate, had lower activities, and (-)-epicatechin was even less effective. Preparations of green tea polyphenols and theaflavins had higher activities than extracts of green tea and decaffeinated green tea. The results suggest that the growth inhibitory activity of tea extracts is caused by the activities of different tea polyphenols. Exposure of H661 cells to 30 microM EGCG, EGC or theaflavins for 24 h led to the induction of apoptosis as determined by an annexin V apoptosis assay, showing apoptosis indices of 23, 26 and 8%, respectively; with 100 microM of these compounds, the apoptosis indices were 82, 76 and 78%, respectively. Incubation of H661 cells with EGCG also induced a dose-dependent formation of H2O2. Addition of H2O2 to H661 cells caused apoptosis in a manner similar to that caused by EGCG. The EGCG-induced apoptosis in H661 cells was completely inhibited by exogenously added catalase (50 units/ml). These results suggest that tea polyphenol-induced production of H2O2 may mediate apoptosis and that this may contribute to the growth inhibitory activities of tea polyphenols in vitro.

Adenocarcinoma↗
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↗
PubMed1999

Teas and other beverages suppress D-galactosamine-induced liver injury in rats.

We compared the effects of various types of beverages (teas, coffee, and cocoa) on D-galactosamine-induced liver injury by measuring plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in 7-wk-old male Wistar rats. The effects of five fractions extracted with different organic solvents from green tea, different types of dietary fibers, and some short chain fatty acids were also investigated. All of the beverages tested significantly suppressed D-galactosamine-induced enhancement of plasma enzyme activities when powdered beverages were added to the diet (30 g/kg) and fed to rats for 2 wk. Plasma ALT activities were 1155 +/- 82 [micromol/(min.L), control], 289 +/- 61 (green tea), 626 +/- 60 (roasted green tea), 471 +/- 84 (puerh tea), 676 +/- 69 (oolon tea), 423 +/- 76 (black tea), 829 +/- 53 (coffee), and 885 +/- 89 (cocoa). The profile of AST activities was similar. The caffeine-containing fraction from green tea had no significant effect, whereas the other four fractions, including the soluble fiber fraction, significantly suppressed liver injury. In addition to tea fibers, many other types of dietary fiber (hemicellulose, chitin, chitosan, alginate, pectin, guar gum, glucomannan, and inulin, but not cellulose) had liver injury-preventive effects when added to the diet (30 g/kg), suggesting that liver injury-prevention may be one of the general effects of dietary fibers. Of three short-chain fatty acids tested (acetate, propionate, and butyrate), only acetate prevented liver injury when added to the diet (15 g/kg), supporting the possibility that the liver injury-preventive effect of dietary fibers may be mediated at least in part by certain organic acids. These results suggest that several beverages possess preventive effects on certain types of liver injury, such as that induced by D-galactosamine, and that different constituents of high and low molecular weights contribute to the liver injury-preventive effects of green tea.

Alanine Transaminase↗
PubMed2003

Antioxidant effects of tea: evidence from human clinical trials.

Tea remains the most consumed drink in the world after water, well ahead of coffee, beer, wine and carbonated soft drinks. An accumulated number of population studies suggests that consumption of green and black tea beverages may bring positive health effects (1). One hypothesis explaining such effects is that the high levels of flavonoids in tea can protect cells and tissues from oxidative damage by scavenging oxygen-free radicals. Chemically, the flavonoids found in green and black tea are very effective radical scavengers. The tea flavonoids may therefore be active as antioxidants in the digestive tract or in other tissues after uptake. A substantial number of human intervention studies with green and black tea demonstrates a significant increase in plasma antioxidant capacity in humans approximately 1 h after consumption of moderate amounts of tea (1-6 cups/d). There are initial indications that the enhanced blood antioxidant potential leads to reduced oxidative damage to macromolecules such as DNA and lipids. However, the measurement of oxidative damage through biomarkers needs to be further established. In conclusion, tea flavonoids are potent antioxidants that are absorbed from the gut after consumption. Tea consumption consistently leads to a significant increase in the antioxidant capacity of the blood. Beneficial effects of increased antioxidant capacity in the body may be the reduction of oxidative damage to important biomolecules. The scientific support is strongest for the protection of DNA from oxidative damage after black or green tea consumption. However, the quality of the studies now available is insufficient to draw firm conclusions. Therefore, further evidence from human intervention studies is required.

Antioxidants↗
PubMed2003

Effect of increased tea consumption on oxidative DNA damage among smokers: a randomized controlled study.

Tea drinking has been associated with decreased occurrence of cancer and heart disease. One potential mechanism for these findings is the strong antioxidant effect of tea polyphenols. A phase II randomized controlled tea intervention trial was designed to study the effect of high consumption (4 cups/d) of decaffeinated green or black tea on oxidative DNA damage as measured by urinary 8-hydroxydeoxyguanosine (8-OHdG) among smokers over a 4-mo period. A total of 143 heavy smokers, aged 18-79 y, were randomized to drink either green or black tea or water. Levels of plasma and urinary catechins and urinary 8-OHdG were measured monthly. A total of 133 of 143 smokers completed the 4-mo intervention. Multiple linear regression models were used to estimate the main effects and interaction effect of green and black tea consumption on creatinine-adjusted urinary 8-OHdG, with or without adjustment for potential confounders. Plasma and urinary levels of catechins rose significantly in the green tea group compared with the other two groups. Assessment of urinary 8-OHdG after adjustment for baseline measurements and other potential confounders revealed a highly significant decrease in urinary 8-OHdG (-31%) after 4 mo of drinking decaffeinated green tea (P = 0.002). No change in urinary 8-OHdG was seen among smokers assigned to the black tea group. These data suggest that regular green tea drinking might protect smokers from oxidative damages and could reduce cancer risk or other diseases caused by free radicals associated with smoking.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2003

The epidemiology of tea consumption and colorectal cancer incidence.

This manuscript provides a brief synopsis of 30 studies aimed at examining tea consumption as a factor in the incidence of colon and rectal cancers. The 30 papers examine populations in 12 countries and provide data on consumption of both black and green tea. These studies do not provide consistent evidence to support the theory from animal studies and basic research that tea is a potent chemopreventive agent. Details of the studies are presented, and the potential impact of measurement error, publication bias, the form of tea consumed, the appropriateness of the outcomes studied and the adjustment of confounders related to both tea consumption and risk of colorectal cancer or polyps in various countries are explored. In general, the data are not more consistent for green than for black tea. Particularly with green tea, the doses consumed do get into a perceived protective range in a significant subset of the population. A negative association is stronger in observational epidemiologic studies of rectal cancer than in colon cancer. There is no consistent adjustment for important potential confounders of any tea relationship, such as coffee and alcohol consumption and physical activity levels. Finally, the assessment of tea in most of these studies was based on a single question and therefore may have significant measurement error compared with more recent studies specifically aimed at assessing tea consumption.

Anticarcinogenic Agents↗
PubMed2003

Tea intake is inversely related to blood pressure in older women.

Tea is rich in polyphenols, which have activities consistent with blood pressure-lowering potential. The effects of long-term regular ingestion of tea on blood pressure remain uncertain. We investigated the relationships of tea intake and a biomarker of exposure to tea-derived polyphenols (4-O-methylgallic acid) with blood pressure in a cross-sectional study of 218 women > 70 y old. Clinic blood pressures were measured and tea intake was assessed using a 24-h dietary recall; 4-O-methylgallic acid was measured for the same period in a 24-h urine sample. Mean (95% CI) daily tea intake was 525 (475, 600) mL. Mean systolic and diastolic blood pressures were 138.1 (135.6, 140.6) and 73.5 (72.1, 74.9) mm Hg. Higher tea intake and higher 4-O-methylgallic acid excretion were associated with significantly lower systolic (P = 0.002 and P = 0.040, respectively) and diastolic (P = 0.027 and P < 0.001, respectively) blood pressures. A 250 mL/d (1 cup) increase in tea intake was associated with a 2.2 (0.8, 3.6) mm Hg lower systolic blood pressure and a 0.9 (0.1, 1.7) mm Hg lower diastolic blood pressure. The observed associations for both tea intake and 4-O-methylgallic acid are consistent with the hypothesis that long-term regular ingestion of tea may have a favorable effect on blood pressure in older women.

Aged↗
PubMed1993

Tea and cancer.

Tea is one of the most popular beverages consumed worldwide. The relationship between tea consumption and human cancer incidence is an important concern. This topic has been studied in different populations by many investigators, but no clear-cut conclusion can be drawn. Whereas some studies have shown a protective effect of tea consumption against certain types of cancers, other studies have indicated an opposite effect. Our purpose is to provide a critical review of this topic, covering basic chemistry and biochemical activity of tea, epidemiologic investigations, and laboratory studies, as well as possible directions for future research. Studies have demonstrated either a lack of association between tea consumption and cancer incidence at specific organ sites or inconsistent results. On the other hand, many laboratory studies have demonstrated inhibitory effects of tea preparations and tea polyphenols against tumor formation and growth. This inhibitory activity is believed to be mainly due to the antioxidative and possible antiproliferative effects of polyphenolic compounds in green and black tea. These polyphenolics may also inhibit carcinogenesis by blocking the endogenous formation of N-nitroso compounds, suppressing the activation of carcinogens, and trapping of genotoxic agents. The effect of tea consumption on cancer is likely to depend on the causative factors of the specific cancer. Therefore, a protective effect observed on a certain cancer with a specific population may not be observable with a cancer of a different etiology. On the basis of this concept, we suggest future laboratory and epidemiologic studies to elucidate the relationship between tea consumption and human cancer risk.

Animals↗
PubMed1996

Tea consumption and cancer incidence in a prospective cohort study of postmenopausal women.

Tea has consistently been shown to inhibit the occurrence of tumors in experimental animals. The evidence for such a beneficial effect in humans, however, is limited. The authors examined the association between non-herbal tea consumption and cancer incidence in a prospective cohort study of 35,369 postmenopausal Iowa women. In this cohort, information on the frequency of tea drinking and other dietary and lifestyle factors was collected by mailed survey in 1986. After 8 years of follow-up, 2,936 incident non-skin cancer cases were ascertained in this cohort through the State Health Registry of Iowa. Proportional hazards regressions were used to derive adjusted relative risks and 95% confidence intervals for the association between tea consumption and cancer incidence. After controlling for confounding factors, the authors found that regular tea consumption was related to a slight, but not statistically significant, reduced incidence of all cancers combined. Inverse associations with increasing frequency of tea drinking were seen for cancers of the digestive tract (p for trend, 0.04) and the urinary tract (p for trend, 0.02). For women who reported drinking > or = 2 cups (474 ml) of tea per day, compared with those who never or occasionally drank tea, the relative risk for digestive tract cancers was 0.68 (95% confidence interval (CI) 0.47-0.98) and for urinary tract cancers, 0.40 (95% CI 0.16-0.98). Similar inverse associations were seen for specific digestive and urinary tract cancers, although site-specific analyses were not statistically significant. No appreciable association of tea drinking was found with melanoma, non-Hodgkin's lymphoma, or cancers of the pancreas, lung, breast, uterine corpus, or ovary. This study suggests that tea, one of the most popular beverages consumed worldwide, may protect against some cancers in postmenopausal women.

Aged↗
PubMed2005

Acute effects of tea on fasting and postprandial vascular function and blood pressure in humans.

BACKGROUND: Effects of regular exposure to polyphenolic compounds found in tea, leading to improved endothelial function and blood pressure, may reduce cardiovascular disease risk. Controlled trials in humans have found that ingestion of tea can improve endothelial function, but also cause a rapid onset acute increase in blood pressure. OBJECTIVE: To examine the acute effects of tea consumption on fasting and postprandial vascular function and blood pressure. METHODS: Endothelium-dependent dilatation of the brachial artery, assessed using ultrasound and blood pressure were measured in 20 participants with a history of coronary artery disease. Measurements were performed at baseline and at 3.5 h (blood pressure) and 4 h (endothelial function) after drinking three cups of black tea or hot water (consumed at time = 0, 1.5 and 3 h) with and without a high-fat (50 g) meal: a total of four treatments administered in random order. RESULTS: The high-fat meal did not impair endothelial function. In comparison to water alone, endothelium-dependent dilatation was increased by the meal with tea (1.7 (0.4, 3.0)%, P = 0.02), but was not significantly altered by the tea alone (0.7 (-0.6, 2.0)%, P = 0.32). Systolic blood pressure was significantly increased by tea alone in comparison to each of the other three groups: water alone (9.3 (4.5, 14.1) mmHg, P = 0.0003), meal with water (9.8 (5.0, 14.6) mmHg, P = 0.0001) and meal with tea (7.2 (2.4,12.0) mmHg, P = 0.004). Consumption of a meal negated the acute increase in systolic blood pressure found with tea in the fasting state. CONCLUSION: Consumption of food may alter the acute effects of tea on vascular function and blood pressure.

Aged↗