A review of the epidemiological evidence on tea, flavonoids, and lung cancer

Protective effects of green tea on intestinal ischemia-reperfusion injury

OBJECTIVE

The intestinal mucosa is known to be adversely affected by ischemia-reperfusion (I/R). Previously we showed that green tea protects the intestinal mucosa from fasting-induced damage. The aim of this study is to determine whether green tea has any protective role in I/R of the intestine.

METHODS

Three groups of male rats were used in this study. Group I (I/R) underwent I/R of the intestine (30 min of ischemia followed by 1 h of reperfusion). Group II (green tea + I/R) was given green tea for 2 wk before inducing I/R. Group III (control) had sham I/R. After the experiments, the jejunum was removed and the tissues were processed for histopathologic examination and immunohistochemical analysis for cell proliferation markers and antioxidant enzymes.

RESULTS

The intestinal mucosa in group II was preserved compared with that in group I. The expressions of cellular proliferation markers (proliferating cell nuclear antigen and Ki-67) and cellular antioxidants (superoxide dismutase and catalase) in group II were similar to those in group III and much less than in group I, reflecting the protective effects of green tea in group II animals.

CONCLUSION

In this animal model, administration of green tea before inducing I/R protects the intestinal mucosa from injury.

Association between green tea consumption and lung cancer risk

Green tea is a popular beverage and its health benefits are well known. However, inconsistent results have been reported in observational studies concerning the association between green tea consumption and the lung cancer risk. In this commentary, several methodological issues underlying the measurement of tea exposure are highlighted. The recommendations should be useful for designing and planning prospective cohort studies to ascertain the protective effect of green tea against lung cancer.

Descriptive analysis and U.S. consumer acceptability of 6 green tea samples from China, Japan, and Korea

In the past, green tea has been one of the least popular nonalcoholic beverages for U.S. consumers. However, green tea has been receiving attention because of its potential health benefits. Knowing which green tea flavor attributes contribute to consumer liking will help the fast growing green tea business including green tea importers, tea shops, and beverage companies to understand which characteristics are most accepted by U.S. consumers. The objectives of this study were (1) to examine differences in acceptability of commonly available loose leaf and bagged green teas available from the major exporters to the U.S. (Japan, Korea, and China) and (2) to determine which green tea flavor characteristics are related to consumers' liking. In the study, consumers from the U.S. evaluated 6 green tea samples from China, Japan, and Korea for acceptability. A highly trained panel also evaluated the green tea samples to provide descriptive sensory attributes that might be related to acceptability. We found that U.S. consumers liked green tea samples with lower flavor intensity and lower bitterness intensity. Consumers' acceptability of green tea was negatively correlated with spinach and animalic flavor and bitterness and astringency of green teas evaluated using descriptive sensory analysis, but the correlation was only moderate. To learn what green tea flavor characteristics influence consumers' liking, future studies using more green tea samples with different flavor profiles are needed.

Flavonoids in Cancer Prevention and Therapy: Chemistry, Pharmacology, Mechanisms of Action, and Perspectives for Cancer Drug Discovery

Among the numerous products available from plants, the flavonoid superfamily plays a central role by its large number of molecules (over 6000) and also by the role these products occupy in the normal physiology of plants. Flavonoids are secondary plant metabolites involved in several biological processes (e.g., germination, UV protection, insecticides) and are also involved in the attraction of pollinating agents via the vivid colors of the anthocyanin pigments found in flowers (e.g., blue, purple, yellow, orange, and red) [1–3]. Flavonoids are found in the normal human diet composed of green vegetables, onions, fruits (apples, grapes, strawberries, etc.), beverages (coffee, tea, beer, red wine) [4, 5], and isoflavonoids are mainly found in soya bean-derived products [6].

Flavonoids from Artemisia annua L. as antioxidants and their potential synergism with artemisinin against malaria and cancer

Artemisia annua is currently the only commercial source of the sesquiterpene lactone artemisinin. Since artemisinin was discovered as the active component of A. annua in early 1970s, hundreds of papers have focused on the anti-parasitic effects of artemisinin and its semi-synthetic analogs dihydroartemisinin, artemether, arteether, and artesunate. Artemisinin per se has not been used in mainstream clinical practice due to its poor bioavailability when compared to its analogs. In the past decade, the work with artemisinin-based compounds has expanded to their anti-cancer properties. Although artemisinin is a major bioactive component present in the traditional Chinese herbal preparations (tea), leaf flavonoids, also present in the tea, have shown a variety of biological activities and may synergize the effects of artemisinin against malaria and cancer. However, only a few studies have focused on the potential synergistic effects between flavonoids and artemisinin. The resurgent idea that multi-component drug therapy might be better than monotherapy is illustrated by the recent resolution of the World Health Organization to support artemisinin-based combination therapies (ACT), instead of the previously used monotherapy with artemisinins. In this critical review we will discuss the possibility that artemisinin and its semi-synthetic analogs might become more effective to treat parasitic diseases (such as malaria) and cancer if simultaneously delivered with flavonoids. The flavonoids present in A. annua leaves have been linked to suppression of CYP450 enzymes responsible for altering the absorption and metabolism of artemisinin in the body, but also have been linked to a beneficial immunomodulatory activity in subjects afflicted with parasitic and chronic diseases.

Coffee consumption and risk of lung cancer: a meta-analysis

Epidemiologic studies have evaluated the potential association between coffee consumption and lung cancer risk. However, results were inconsistent. To clarify the role of coffee in lung cancer, we conducted a meta-analysis on this topic. We searched PubMed and EMBASE databases (from 1966 to January 2009) and the reference lists of retrieved articles. Study-specific risk estimates were pooled using random-effects model. Five prospective studies and 8 case-control studies involving 5347 lung cancer cases and 104,911 non-cases were included in this meta-analysis. The combined results indicated a significant positive association between highest coffee intake and lung cancer [relative risk (RR)=1.27, 95% confidence interval (CI)=1.04-1.54). Furthermore, an increase in coffee consumption of 2 cups/day was associated with a 14% increased risk of developing lung cancer (RR=1.14, 95% CI=1.04-1.26). In stratified analyses, the highest coffee consumption was significantly associated with increased risk of lung cancer in prospective studies, studies conducted in America and Japan, but borderline significantly associated with decreased risk of lung cancer in non-smokers. In addition, decaffeinated coffee drinking was associated with decreased lung cancer risk, although the number of studies on this topic was relative small. In conclusion, results from this meta-analysis indicate that high or an increased consumption of coffee may increase the risk of lung cancer. Because the residual confounding effects of smoking or other factors may still exist, these results should be interpreted with caution.

Chrysin sensitizes tumor necrosis factor-alpha-induced apoptosis in human tumor cells via suppression of nuclear factor-kappaB

Chrysin (5,7-dihydroxyflavone) is a natural flavonoid commonly found in many plants. The anti-cancer property of chrysin has been demonstrated although the molecular mechanisms remain to be further elucidated. In the present study, we found that, pretreatment with chrysin greatly sensitized various human cancer cells to tumor necrosis factor-alpha (TNFalpha)-induced apoptosis. In the search of the molecular mechanisms responsible for the sensitization effect of chrysin, we discovered that such sensitization is closely associated with the inhibitory effect of chrysin on TNFalpha-mediated nuclear transcription factor-kappaB (NF-kappaB) activation. Pretreatment with chrysin inhibited TNFalpha-induced degradation of Inhibitor of kappaB (IkappaB) protein and subsequent nuclear translocation of p65. As a result, chrysin suppressed the expression of NF-kappaB-targeted anti-apoptotic gene, c-FLIP-L. The role of c-FLIP-L was further confirmed by its ectopic expression, which significantly protected cell death induced by combined treatment with chrysin and TNFalpha. Data from this study thus reveal a novel function of chrysin and enhance the value of chrysin as an anti-cancer agent.

Cancer protective properties of cocoa: a review of the epidemiologic evidence

Due to their high concentration of catechins and procyanidins, bioactive compounds with distinct properties, cocoa and chocolate products may have beneficial health effects against oxidative stress and chronic inflammation, risk factors for cancer and other chronic diseases. This review focuses on the epidemiologic evidence for protective effects against cancer and overall mortality. The very small number of observational epidemiologic studies offers weak support for a reduction in mortality and little data related to cancer, whereas several intervention studies, despite their short duration, have reported some favorable changes in biomarkers assessing antioxidant status but very few findings related to inflammatory markers. In moderation, cocoa products may offer strong antioxidant effects in combination with a pleasurable eating experience. The benign profile of its fatty acids in combination with the low content of sugar of dark chocolate should lessen concerns about the adverse effects of cocoa products. Future nutritional trials need to assess a larger number of biomarkers that may be relevant for cancer risk, whereas epidemiologic studies require valid dietary assessment methods to examine the association of cocoa products with cancer risk in larger populations and to distinguish possible cancer protective effects of cocoa products from those due to other polyphenolic compounds.

Fern plant-derived protoapigenone leads to DNA damage, apoptosis, and G(2)/m arrest in lung cancer cell line H1299

Protoapigenone, isolated from the native fern plant Thelypteris torresiana, has anticancer activity against some cancer cells. However, the toxicological mechanism for protoapigenone is still unknown. Here, we investigated the anticancer effect of protoapigenone on human lung cancer cell lines. The comet assay showed that DNA damage induced by protoapigenone is dose-dependent. Trypan blue exclusion showed that the cell killing by protoapigenone is both time and dose dependent. The IC(50) of protoapigenone for 12, 24, and 48 h in H1299 cells is 6.11, 2.74, and 1.49 microM, respectively. Flow cytometry showed cell cycle perturbation such as sub-G(1) accumulation (at 1.57 microM for 48 h and at 3.57 microM for 12 and 24 h) and G(2)/M arrest (at 3.57 microM for 12 and 24 h) for protoapigenone. The sub-G(1) accumulation phenomena in the 3.57 microM for 24 h sample were shown to be apoptosis using Annexin V-immunofluorescence/propidium iodide staining. These results suggest protoapigenone is a potential chemotherapeutic agent for lung cancers.

Antioxidant mechanisms of Quercetin and Myricetin in the gas phase and in solution--a comparison and validation of semi-empirical methods

Flavonoids have long been recognized for their general health-promoting properties, of which their antioxidant activity may play an important role. In this work we have studied the properties of two flavonols, quercetin and myricetin, using semi-empirical methods in order to validate the application of the recent Parametric Model 6 and to understand the fundamental difference between the two molecules. Their geometries have been optimized and important molecular properties have been calculated. The energetic of the possible antioxidant mechanisms have also been analyzed. The two studied flavonols do not differ significantly in their molecular properties, but the antioxidant mechanisms by which they may act in solution can be rather different. Moreover, we also show that the Parametric Model 6 can produce reliable information for this type of compounds.

Can green tea do that? A literature review of the clinical evidence

OBJECTIVE

Habitual green tea consumption has long been associated with health benefits including chemoprevention and cardiovascular protection. This non-systematic literature review presents the clinical evidence to date.

METHOD

A literature review of peer-reviewed articles on observational and interventional studies was conducted to include green tea, its extract or its purified polyphenol (-)-epigallocatechin-3-gallate (EGCG). Electronic databases searched included PubMed (1966-2009) and the Cochrane Library (Issue 4, 2008).

RESULTS

Observational studies are inconclusive on the benefits of habitual consumption of green tea in the prevention of most cancers. However, there are trends towards prevention in breast and prostate cancers. Interventional studies have demonstrated reduction in relapses following surgical resection in colorectal adenomas and increased survival rates in epithelial ovarian cancer. Observational studies indicate that green tea may provide protection against hypertension and reduce the risk for stroke, and interventional studies are providing biochemical and physiological evidence.

CONCLUSION

Although the overall clinical evidence is inconclusive, habitual green tea consumption may be providing some level of chemoprevention in prostate and breast cancer. Green tea may also attenuate the risk factors association with the development of atherosclerosis thus reducing the incidence of cardiovascular events and stoke.

Bioactive components of tea: cancer, inflammation and behavior

Tea is one of the most widely consumed beverages worldwide. Several studies have suggested that catechins and theaflavins found in tea may reduce the risk of various types of cancers. Major advances have been made to understand the molecular events leading to cancer prevention; however, the evidence is not conclusive. Evidence from pre-clinical and clinical studies also suggests that persistent inflammation can progress to cancer. Several possible mechanisms of action may explain the cancer preventive aspects of tea components specifically anti-inflammatory effects. In regards to brain health, green tea catechins have been recognized as multifunctional compounds for neuroprotection with beneficial effects on vascular function and mental performance. Theanine, a unique amino acid in tea, enhances cognition in humans and has neuroprotective effects. Human interventional studies with well characterized tea products are needed.

Increase of theaflavin gallates and thearubigins by acceleration of catechin oxidation in a new fermented tea product obtained by the tea-rolling processing of loquat ( Eriobotrya japonica ) and green tea leaves

In a project to produce a new fermented tea product from non-used tea leaves harvested in the summer, we found that kneading tea leaves ( Camellia sinensis ) with fresh loquat leaves ( Eriobotrya japonica ) accelerated the enzymatic oxidation of tea catechins. The fermented tea obtained by tea-rolling processing of tea and loquat leaves had a strong, distinctive flavor and a plain aftertaste, which differed from usual black, green, and oolong teas. The phenolic constituents were similar to those of black tea. However, the concentrations of theaflavin 3-O-gallate, theaflavin 3,3'-di-O-gallate, and thearubigins were higher in the tea leaves kneaded with loquat leaves than in tea leaves kneaded without loquat leaves. The results from in vitro experiments suggested that acceleration of catechin oxidation was caused by the strong oxidation activity of loquat leaf enzymes and a coupled oxidation mechanism with caffeoyl quinic acids, which are the major phenolic constituents of loquat leaves.

Tea polyphenols decrease serum levels of prostate-specific antigen, hepatocyte growth factor, and vascular endothelial growth factor in prostate cancer patients and inhibit production of hepatocyte growth factor and vascular endothelial growth factor in vitro

The purpose of this study was to determine the effects of short-term supplementation with the active compounds in green tea on serum biomarkers in patients with prostate cancer. Twenty-six men with positive prostate biopsies and scheduled for radical prostatectomy were given daily doses of Polyphenon E, which contained 800 mg of (-)-epigallocatechin-3-gallate (EGCG) and lesser amounts of (-)-epicatechin, (-)-epigallocatechin, and (-)-epicatechin-3-gallate (a total of 1.3 g of tea polyphenols), until time of radical prostatectomy. Serum was collected before initiation of the drug study and on the day of prostatectomy. Serum biomarkers hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF)-I, IGF binding protein-3 (IGFBP-3), and prostate-specific antigen (PSA) were analyzed by ELISA. Toxicity was monitored primarily through liver function enzymes. Changes in serum components were analyzed statistically using the Wilcoxon signed rank test. Cancer-associated fibroblasts were treated with EGCG, and HGF and VEGF protein and mRNA levels were measured. HGF, VEGF, PSA, IGF-I, IGFBP-3, and the IGF-I/IGFBP-3 ratio decreased significantly during the study. All of the liver function tests also decreased, five of them significantly: total protein, albumin, aspartate aminotransferase, alkaline phosphatase, and amylase. The decrease in HGF and VEGF was confirmed in prostate cancer-associated fibroblasts in vitro. Our results show a significant reduction in serum levels of PSA, HGF, and VEGF in men with prostate cancer after brief treatment with EGCG (Polyphenon E), with no elevation of liver enzymes. These findings support a potential role for Polyphenon E in the treatment or prevention of prostate cancer.

Catechin induced longevity in C. elegans: from key regulator genes to disposable soma

The flavanol catechin is a ubiquitous metabolite within the plant kingdom. Several health benefits have previously been reported, however, to date, most attention has been devoted to gallated forms of catechin. This study utilized the nematode Caenorhabditis elegans to assess potential life expanding effects of non-gallated catechin. Longevity was observed at three different catechin concentrations, an effect that was neither linked to a specific temperature nor to the viability of the feeding bacteria. Taken all tests into account, hormesis, calorie restriction, as well as the presence of simple antioxidative or antibacterial effects could be excluded. Likewise, the insulin/IGF-1 like signaling pathway and the calmodulin kinase II pathway were not considered to play a major mechanic role. Moreover, stress resistance was enhanced without a marked alteration in reproductive behavior. In addition, lifespan tests with various stress and lifespan relevant mutant strains revealed that the life span extending phenotype was absent in mev-1, daf-2, akt-2 and nhr-8. Finally, catechin elicited a significant reduction in body length, a finding that is in line with the "Disposable Soma Theory". It is proposed that catechin modulates an energy-intensive stress response and repair system that results in reduced body length and an enhanced lifespan.

Green tea, black tea consumption and risk of lung cancer: a meta-analysis

Studies investigating the association of green tea and black tea consumption with lung cancer risk have reported inconsistent findings. To provide a quantitative assessment of this association, we conducted a meta-analysis on the topic. Studies were identified by a literature search in PubMed from 1966 to November 2008 and by searching the reference lists of relevant studies. Summary relative risk (RR) estimates and their corresponding 95% confidence intervals (CIs) were calculated based on random-effects model. Our meta-analysis included 22 studies provided data on consumption of green tea or black tea, or both related to lung cancer risk. For green tea, the summary RR indicated a borderline significant association between highest green tea consumption and reduced risk of lung cancer (RR=0.78, 95% CI=0.61-1.00). Furthermore, an increase in green tea consumption of two cups/day was associated with an 18% decreased risk of developing lung cancer (RR=0.82, 95% CI=0.71-0.96). For black tea, no statistically significant association was observe through the meta-analysis (highest versus non/lowest, RR=0.86, 95% CI=0.70-1.05; an increment of two cups/day, RR=0.82, 95% CI=0.65-1.03). In conclusion, our data suggest that high or an increase in consumption of green tea but not black tea may be related to the reduction of lung cancer risk.

Tea and health: preventive and therapeutic usefulness in the elderly?

PURPOSE OF REVIEW

To update the growing literature suggesting that tea and its constituent flavonoids are inversely related to the risk of chronic diseases common among the elderly.

RECENT FINDINGS

Results are provided from recent observational studies and clinical trials on the relationship of tea and tea catechins to body weight control and energy metabolism, impaired glucose tolerance and diabetes, cardiovascular disease, bone mineral density, cognitive function and neurodegenerative disease, and cancer. The evidence for the efficacy and potency of tea and tea extracts in benefiting these outcomes ranges from compelling for cardiovascular disease to equivocal at best for some forms of cancer.

SUMMARY

Although randomized clinical trials of tea have generally been of short duration and with small sample sizes, together with experimental and epidemiological studies, the totality of the data suggests a role for tea in health promotion as a beverage absent in calories and rich in phytochemicals. Further research is warranted on the putative benefits of tea and the potential for synergy among its constituent flavonoids, L-theanine, and caffeine.

Electrospray ionization tandem mass spectrometry fragmentation of protonated flavone and flavonol aglycones: a re-examination

Flavonoids are important phytochemicals which have been intensively studied in the last decades in view of their antioxidant activity, which is of particular importance in the case of flavones and flavonols, that differ in a single 3-OH group. Mass spectrometry has been used to elucidate the structures of many types of flavonoids and their metabolites. The work we present here is focused on the electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of flavone and flavonols aglycones. Their fragmentation mechanisms in the positive ion mode are described and compared with previously reported mechanisms. We analyzed flavonoid derivatives produced by reaction of the flavonoids with chemically synthesized hypohalous acids (HOCl, HOBr and HOI) and peroxynitrite, reactive species involved in the inflammatory response. All the proposed pathways have been analyzed using computational chemistry methods in order to seek for possible variations and establish the most plausible ones. We observed that the losses of one and two CO molecules can be useful in terms of antioxidant activity prediction. Losses of one and two C(2)H(2)O groups are also informative in terms of structure and activity predictions. The retro-Diels-Alder fragmentations, and subsequent neutral losses, were reviewed and, according to our calculations, the most plausible structures for the product ions were established. These fingerprints will be of great value for differentiating flavonoids from other compounds in complex biological mixtures and for a thorough structural identification of flavonoid aglycones and their in vivo metabolites.

Nongallated compared with gallated flavan-3-ols in green and black tea are more bioavailable

Green tea and black tea (BT) contain gallated [(-)-epigallocatechin-3-gallate (EGCG), (-)-epicatechin-3-gallate] and nongallated [(-)-epicatechin, (-)-epigallocatechin (EGC)] tea polyphenols (PP). During BT production, PP undergo oxidation and form larger polymers such as theaflavins (THE) and thearubigins, which contribute to the health benefit of BT. This article gives an overview of the role of chemical characteristics and endogenous metabolism of tea PP and their bioavailability in humans and describes attempts to increase their bioavailability. At pH close to neutral, EGCG and EGC form homo- and heterodimers generating hydrogen peroxide. To confirm the pH instability of EGCG, EGC, and THE in cell culture medium, their antiproliferative activity was determined in the presence and absence of catalase. The antiproliferative activity in LNCaP prostate cancer cells was decreased when incubated with catalase prior to EGCG, EGC, and THE treatment. In addition, new findings demonstrated that the formation of methyl-EGC increased the stability at neutral pH compared with EGC. Approaches to increase the bioavailability of flavan-3-ols are reviewed, which include the administration of tea in combination with fruit juices, coadministration with piperine, and peracetylation of EGCG. Future intervention studies will need to focus on the bioactivity not only of green tea and BT PP but also of their metabolites and biotransformation products.

Tea, flavonoids, and nitric oxide-mediated vascular reactivity

Epidemiological evidence supports the concept that diets rich in fruits and vegetables promote health and attenuate or delay the onset of cardiovascular disease (CVD). Although a variety of factors contribute to the beneficial effects of plant foods, much attention has been addressed to plant polyphenols. In this regard, in the daily Western diet, both black and green teas contribute to a relevant proportion of total phenol intake. The more abundant class of flavonoids that is present in teas is represented by flavanols, i.e., catechin, epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate. Studies using animal models of atherosclerosis indicate that dietary flavonoid consumption delays atherosclerotic plaque development. Accordingly, an inverse association between tea intake and CVD has been demonstrated. Further, flavonoids can reduce endothelial dysfunction, i.e., the key step in the development of atherosclerosis. Concordantly, human data suggest that tea may reduce blood pressure levels. Despite this, although they often show that tea may have cardiovascular protective effects, results from epidemiological studies exploring the association between tea and health are controversial. Conflicting results may be caused by disparate study designs and flavonoid contents in different kinds of tea. Thus, because tea is a popular beverage worldwide, and several studies have shown that it is protective against CVD, further studies are needed to determine the role of tea in primary and secondary cardiovascular prevention.

Tea consumption may improve biomarkers of insulin sensitivity and risk factors for diabetes

Diabetes mellitus and its sequelae are a major and growing public health problem. The prevalence of diabetes worldwide is 194 million persons, or 5.1% of the population, and is projected to increase to 333 million, or 6.3% of the population, by 2025. Type 2 diabetes accounts for approximately 90-95% of those with diabetes in the United States and other developed countries. Tea is the most widely consumed beverage in the world, second only to water. Tea contains polyphenols and other components that may reduce the risk of developing chronic diseases such as cardiovascular disease and cancer. Some evidence also shows that tea may affect glucose metabolism and insulin signaling, which, as a result, has spurred interest in the health effects of tea consumption on diabetes. Epidemiologic studies suggest some relation between tea consumption and a reduced risk of type 2 diabetes, although the mechanisms for these observations are uncertain. Findings from in vitro and animal models suggest that tea and its components may influence glucose metabolism and diabetes through several mechanisms, such as enhancing insulin sensitivity. Some human clinical studies evaluating tea and its components show improvement in glucoregulatory control and endothelial function. However, further controlled clinical trials are required to gain a better understanding of the long-term effects of tea consumption in persons with diabetes.

Targeting multiple neurodegenerative diseases etiologies with multimodal-acting green tea catechins

Green tea is currently considered a source of dietary constituents endowed with biological and pharmacological activities relevant to human health. Human epidemiological and new animal data suggest that the pharmacological benefits of tea drinking may help to protect the brain as we age. Indeed, tea consumption is inversely correlated with the incidence of dementia and Alzheimer's and Parkinson's diseases. In particular, its main catechin polyphenol constituent (-)-epigallocatechin-3-gallate has been shown to exert neuroprotective/neurorescue activities in a wide array of cellular and animal models of neurological disorders. The intense efforts dedicated in recent years to shed light on the molecular mechanisms participating in the brain protective action of green tea indicate that in addition to the known antioxidant activity of catechins, the modulation of signal transduction pathways, cell survival/death genes, and mitochondrial function all contribute significantly to the induction of neuron viability. Because of the multietiological character of neurodegenerative disease pathology, these natural compounds are receiving significant attention as therapeutic cytoprotective agents that simultaneously manipulate multiple desired targets in the central nervous system. This article elaborates on the multimodal activities of green tea polyphenols with emphasis on their recently described neurorescue/neuroregenerative and mitochondrial stabilization actions.

L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance

Recent neuropharmacological research has suggested that certain constituents of tea may have modulatory effects on brain state. The bulk of this research has focused on either L-theanine or caffeine ingested alone (mostly the latter) and has been limited to behavioral testing, subjective rating, or neurophysiological assessments during resting. Here, we investigated the effects of both L-theanine and caffeine, ingested separately or together, on behavioral and electrophysiological indices of tonic (background) and phasic (event-related) visuospatial attentional deployment. Subjects underwent 4 d of testing, ingesting either placebo, 100 mg of L-theanine, 50 mg of caffeine, or these treatments combined. The task involved cued shifts of attention to the left or right visual hemifield in anticipation of an imperative stimulus requiring discrimination. In addition to behavioral measures, we examined overall, tonic attentional focus as well as phasic, cue-dependent anticipatory attentional biasing, as indexed by scalp-recorded alpha-band (8-14 Hz) activity. We found an increase in hit rate and target discriminability (d') for the combined treatment relative to placebo, and an increase in d' but not hit rate for caffeine alone, whereas no effects were detected for L-theanine alone. Electrophysiological results did not show increased differential biasing in phasic alpha across hemifields but showed lower overall tonic alpha power in the combined treatment, similar to previous findings at a larger dosage of L-theanine alone. This may signify a more generalized tonic deployment of attentional resources to the visual modality and may underlie the facilitated behavioral performance on the combined ingestion of these 2 major constituents of tea.

The relation between green tea consumption and cardiovascular disease as evidenced by epidemiological studies

Although substantial evidence from in vitro and animal studies indicates that green tea preparations inhibit cardiovascular disease processes, the possible protective role of green tea consumption against this disease in humans remains unclear. We conducted a population-based prospective cohort study (the Ohsaki Study) to examine the association between green tea consumption and mortality from cardiovascular disease (CVD), cancer, and all causes with 40,530 persons in Miyagi prefecture, in northern Japan. Previously published work has shown that green tea consumption was inversely associated with mortality from CVD and all causes. The inverse association of mortality from CVD was more pronounced in women (P = 0.08 for interaction with sex). In women, the multivariate hazard ratios (95% confidence intervals) of CVD mortality across increasing green tea consumption categories were 1.00, 0.84 (0.63-1.12), 0.69 (0.52-0.93), 0.69 (0.53-0.90) (P for trend = 0.004). Within CVD mortality, the stronger inverse association was observed for stroke mortality. Because our observational study has found the inverse association, I report here the results of a review of epidemiological evidence from randomized controlled trials (RCT) of the association between green tea or green tea extracts and CVD risk profiles. More than half of the RCT have demonstrated the beneficial effects of green tea on CVD risk profiles. These results from RCT suggest a plausible mechanism for the beneficial effects of green tea and provide substantial support for our observations.

Tea is the major source of flavan-3-ol and flavonol in the U.S. diet

Flavonoid intake is inversely associated with the incidence of chronic diseases, but the sources of flavonoid intake in free-living U.S. adults have not yet been reported. We tested hypotheses that tea is the major dietary source of flavonoids in U.S. adults; tea consumers differ from those of tea nonconsumers in sociodemographics, health-related behaviors, and dietary and beverage sources of flavonoid intake. We matched the flavonoid contents of the USDA Flavonoid Databases with dietary intake data of adults (n = 8809) included in NHANES of 1999-2002. Only 21.3% of U.S. adults reported drinking tea daily. Daily total flavonoid intake of tea consumers was over 20 times that of tea nonconsumers (697.9 vs. 32.6 mg/d); per capita flavonoid intake from tea was 157 mg/d. Tea consumers are more likely to be older, female, white, and to have higher income than tea nonconsumers (P < 0.001); to have lower nonleisure-time physical activity level (P < 0.01); and to take dietary supplements (P < 0.001) than tea nonconsumers. Intake of flavonols and flavan-3-ols, the major tea flavonoids, differed between the 2 groups (P < 0.01). Other dietary flavonoid sources after tea were citrus juice, wine, and citrus fruits for both tea consumer and nonconsumer groups. For tea nonconsumers, flavonoid intake from wine, fruitades, and fruit drinks was higher than that in tea consumers. Flavonoid intake differs among subgroups, mainly because of the percentage of tea consumers and the prevalence of tea consumption within each subgroup.

Green tea consumption is associated with decreased DNA damage among GSTM1-positive smokers regardless of their hOGG1 genotype

The levels of tobacco-related DNA adducts in human tissues reflect a dynamic process that is dependent on the intensity and time of exposure to tobacco smoke, the metabolic balance between activation of detoxification mechanisms, and the removal of adducts by DNA repair and/or cell turnover. Urinary 8-hydroxydeoxyguanosine (8-OHdG) is probably 1 of the most abundant DNA lesions formed during oxidative stress and is proposed as a sensitive biomarker of the overall oxidative DNA damage and repair. We performed this study to determine whether there were differences in increased oxidative stress susceptibility to smoking within the combined GSTM1 and hOGG1 genotypes and the impact of green tea drinking on this. We completed a Phase II randomized, controlled, 3-arm tea intervention trial to study the effect of high consumption of decaffeinated green or black tea or water on urinary 8-OHdG among heavy smokers and to evaluate the roles of GSTM1 and hOGG1 genotypes as effect modifiers. Assessment of urinary 8-OHdG after adjustment for baseline measurements and other potential confounders revealed a significant effect of green tea consumption (P = 0.001). The change from baseline was significant in all GSTM1-positive smokers regardless of their hOGG1 genotype. Our data show that consumption of 4 cups (960 mL) of tea/d is a feasible and safe approach and was associated with a significant decrease in urinary 8-OHdG among green tea consumers. Our finding also suggests that green tea intervention might be effective in decreasing DNA damage in the subgroup of smokers who are GSTM1 positive regardless of their hOGG1 genotype.

Bioavailability of polyphenon E flavan-3-ols in humans with an ileostomy

To investigate the degree of absorption of flavan-3-ols in the small intestine, human subjects with an ileostomy ingested 200 mg of Polyphenon E, a green tea extract, after which ileal fluid and urine, collected over a 24-h period, were analyzed by high-performance liquid chromatography with photodiode array and mass spectrometric detection. The data obtained indicated that although approximately 40% of flavan-3-ol intake is recovered in ileal fluid, substantial quantities are absorbed in the small intestine. Moreover, 14 urinary metabolites, comprising sulfates, glucuronide, and methylated derivatives, were identified and quantified. All were metabolites of (epi)catechin or (epi)gallocatechin, representing 47 +/- 2% and 26 +/- 9%, respectively, of the ingested parent compound. These high recoveries indicate that these flavan-3-ols absorbed in the small intestine are much more bioavailable than most dietary flavonoids. No 3-O-galloylated flavan-3-ols or their metabolites were detected in urine. The absence of urinary flavan-3-ol metabolites after ingestion of 200 mg of (-)-epigallocatechin gallate indicates that there is no removal of the 3-O-galloyl group in vivo, and hence, this does not account for the high urinary recovery of (epi)gallocatechin metabolites after ingestion of Polyphenon E. Increasing the intake of Polyphenon E, by feeding doses of 200, 500, and 1500 mg, led to increased urinary excretion of (epi)catechin metabolites but not metabolites of (epi)gallocatechin. Coingestion of 200 mg of Polyphenon E with bread, cheese, or glucose did not significantly modify the absorption, metabolism, and excretion of flavan-3-ols. It does not necessarily follow, however, that the same would occur when flavan-3-ols are ingested with more complex food matrices.