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Green Tea is one of the most extensively, and successfully, researched herbs in the world today. It was first noticed several decades ago, that people involved in presenting the green tea ceremonies had remarkably low incidence of cancer. Hundreds of studies later, we now know that green tea, and in fact all tea (Camellia sinensis) as a wide range of beneficial properties for reducing risks of cancer, heart disease and liver disease, plus antioxidant properties, benefits for the skin and much more. We hear present some of the recent research on tea and its antioxidant polyphenols.
For all the latest news on tea, click Tea under Categories to the right.
Green tea polyphenols such as EGCG have potent anti-inflammatory properties. Prior research had shown that EGCG inhibits tumor necrosis factor through a mechanism that was thought to have implications for inflammation generally. Epidemiological studies link regular consumption of tea with decreased cancer risk and a reduction in mortality during the 12 month period following a heart attack. “Considerably less is known regarding the mechanisms by which tea confers these health benefits.” The present research demonstrates one important mechanism Read more
The thermogenic effect of tea is generally attributed to its caffeine content. An article in Alternative Medicine Review reports that green tea extract stimulates brown adipose tissue thermogenesis to an extent which is much greater than can be attributed to its caffeine content alone. Read more
The incidence of late onset breast cancer has been increasing dramatically in the United States. Since genetic factors are believed to result primarily in early onset cases, accumulation of environmental toxins has been proposed as one factor in the increased incidence. Research reported in the Journal of Nutrition demonstrates that EGCG can protect mice against carcinogen induced breast tumors. The green tea polyphenol significantly decreased mammary tumor burden and invasiveness and significantly increased latency to the first tumor. The authors suggest “the ability of EGCG and other tea polyphenols to inhibit carcinogenesis make EGCG a good template for deriving small molecule drugs. Modifications and structure may improve the pharmacokinetics and effectiveness. As a readily available dietary substance, it holds promise for prevention of early-stage cancer.” FULL ARTICLE –> Read more
In studies conducted on human skin, green tea polyphenols prevented ultraviolet (UVB) induced chemical changes in the skin, which are considered to be mediators of UVB induced immunosuppression and skin cancer induction. GTP treated humans can prevented penetration of UV radiation, and protected against UVB-induced local as well as systemic immune suppression in laboratory animals. “These in vivo observations suggest that GTP is our photo protective and can be used as pharmacological agents for the prevention of solar UVB light induced skin disorders associated with immune suppression and DNA damage.”
Alternative Medicine Review April 1, 2002 Bergamo, BM; Elmets, CA; Katiyar, SK; Vyalil, PK
Green tea polyphenols: DNA photodamage and photoimmunology.(Abstract)
atiyar SK, Bergamo BM, Vyalil PK, Elmets CA. J Photochem Photobiol B 2001;6:109-114.
Green tea is a popular beverage consumed worldwide. The epicatechin derivatives, which are commonly called `polyphenols’, are the active ingredients in green tea and possess antioxidant, anti-inflammatory and anti-carcinogenic properties. Studies conducted by our group on human skin have demonstrated that green tea polyphenols (GTP) prevent ultraviolet (UV)-B-induced cyclobutane pyrimidine dimers (CPD), which are considered to be mediators of UVB-induced immune suppression and skin cancer induction. GTP treated human skin prevented penetration of UV radiation, which was demonstrated by the absence of immunostaining for CPD in the reticular dermis. The topical application of GTP or its most potent chemopreventive constituent (-)-epigallocatechin-3-gallate (EGCG) prior to exposure to UVB protects against UVB-induced local as well as systemic immune suppression in laboratory animals. Additionally, studies have shown that EGCG treatment of mouse skin inhibits UVB-induced infiltration of CD11b+ cells. CD11b is a cell surface marker for activated macrophages and neutrophils, which are associated with induction of UVB-induced suppression of contact hypersensitivity responses. EGCG treatment also results in reduction of the UVB-induced immunoregulatory cytokine interleukin (IL)-10 in skin as well as in draining lymph nodes, and an elevated amount of IL-12 in draining lymph nodes. These in vivo observations suggest that GTPs are photoprotective, and can be used as pharmacological agents for the prevention of solar UVB light-induced skin disorders associated with immune suppression and DNA damage.
Recent research published in the American Journal of Physiology Endocrinology And Metabolism describes wide-ranging cardiovascular protective functions of a green tea polyphenol, EGCG. EGCG improved endothelial function and insulin sensitivity, reduced blood pressure and protected against myocardial ischemia and reperfusion injury. The addition of improvements in insulin sensitivity to the cardiovascular benefits indicates the benefit of green tea polyphenols against metabolic syndrome with hypertension, insulin resistance and overweight.
Am J Physiol Endocrinol Metab, 2007 Jan 16; [Epub ahead of print]Potenza MA, Marasciulo FL, Tarquinio M, et al.
Epigallocatechin gallate (EGCG), a bioactive polyphenol in green tea, may augment metabolic and vascular actions of insulin. We investigated effects of EGCG treatment to simultaneously improve cardiovascular and metabolic function in SHR rats (model of metabolic syndrome with hypertension, insulin resistance, and overweight). In acute studies, EGCG (1-100 microM) elicited dose-dependent vasodilation in mesenteric vascular beds (MVB) from SHR ex vivo, inhibitable by L-NAME (NOS antagonist) or wortmannin (PI 3-kinase inhibitor). In chronic studies, 9-wk old SHR were treated by gavage for 3 weeks with EGCG (200 mg/kg/d), enalapril (30 mg/kg/d), or vehicle. A separate group of SHR receiving L-NAME (80 mg/L in drinking water) was treated for 3 weeks with either EGCG or vehicle. Vasodilator actions of insulin were significantly improved in MVB from EGCG- or enalapril-treated SHR (compared with vehicle-SHR). Both EGCG and enalapril therapy significantly lowered systolic blood pressure (SBP) in SHR. EGCG therapy of SHR significantly reduced infarct size and improved cardiac function in Langendorff-perfused hearts exposed to ischemia/reperfusion injury (I/R). In SHR given L-NAME, effects of EGCG on SBP and I/R were not observed. Both enalapril and EGCG treatment of SHR improved insulin sensitivity and raised plasma adiponectin. We conclude that acute actions of EGCG to stimulate production of NO from endothelium using PI 3-kinase dependent pathways may explain, in part, beneficial effects of EGCG therapy to simultaneously improve metabolic and cardiovascular pathophysiology in SHR. These findings may be relevant to understanding potential benefits of green tea consumption in patients with metabolic syndrome.
The green tea flavonoid EGCG has potential therapeutic value for
treatment to for HIV-1 infection EGCG binds to the CD4 molecule on
T-cells according to research conducted in 2006. “We have
demonstrated clear evidence of high affinity binding of EGCG to the CD4
molecule. EGCG has potential use as an adjunctive treatment in HIV-1
J Allergy Cli, Immunol Williamson ME McCormick TG, Nance CL, Shearer WT. 2006;118:1369-1374.
Epigallocatechin gallate, the main polyphenol in green tea, binds to
the T-cell receptor, CD4: potential for HIV-1 therapy.(Recent
BACKGROUND: The green tea flavonoid, epigallocatechin gallate (EGCG),
has been proposed to have an anti-HIV-1 effect by preventing the
binding of HIV-1 glycoprotein (gp) 120 to the CD4 molecule on T cells.
OBJECTIVE: To demonstrate that EGCG binds to the CD4 molecule at the
gpl20 attachment site and inhibits gp120 binding at physiologically
relevant levels, thus establishing EGCG as a potential therapeutic
treatment for HIV-1 infection. METHODS: Nuclear magnetic resonance
spectroscopy was used to examine the binding of EGCG and control,
(-)-catechin, to CD4-IgG2 (PRO 542). Gp120 binding to human CD4+ T
cells was analyzed by flow cytometry. RESULTS: Addition of CD4 to EGCG
produced a linear decrease in nuclear magnetic resonance signal
intensity from EGCG but not from the control, (-)-catechin. In
saturation transfer difference experiments, addition of 5.8 micromol/L
CD4 to 310 micromol/L EGCG produced strong saturation at the aromatic
rings of EGCG, but identical concentrations of (-)-catechin produced
much smaller effects, implying EGCG/CD4 binding strong enough to reduce
gp120/ CD4 binding substantially. Molecular modeling studies suggested
a binding site for EGCG in the D1 domain of CD4, the pocket that binds
gpl20. Physiologically relevant concentrations of EGCG (0.2 micromol/L)
inhibited binding of gp120 to isolated human CD4+ T cells. CONCLUSION:
We have demonstrated clear evidence of high-affinity binding of EGCG to
the CD4 molecule with a Kd of approximately 10 nmol/L and inhibition
ofgpl20 binding to human CD4+ T cells. CLINICAL IMPLICATIONS:
Epigallocatechin gallate has potential use as adjunctive therapy in
Green tea is the fourth most commonly used dietary supplement in the
United States. After the publication of adverse event case reports
involving green tea products and potential liver toxicity, the US
Pharmacopeia reviewed safety information for green tea products. 216
case reports on green tea products were analyzed including 34 reports
concerning liver damage. 27 reports pertaining to liver damage were
categorized as possible causality and seven as probable causality.
Pharmacokinetic and animal toxicological studies indicate that
consumption of green tea concentrated extracts on an empty stomach is
more likely to lead to adverse effects than consumption in the fed
state. USP concluded “when dietary supplement products containing
green tea extracts are used in formulated appropriately the Committee
is unaware of significant safety issues that would prohibit monograph
development, provided that caution statement is included in the
Safety of Green Tea Extracts : A Systematic Review by the US Pharmacopeia.
Drug Saf. 2008;31(6):469-84.. Sarma DN, Barrett ML, Chavez ML, Gardiner
P, Ko R, Mahady GB, Marles RJ, Pellicore LS, Giancaspro GI, Low Dog T.
Green tea [Camellia sinensis (L.) Kuntze] is the fourth most
commonly used dietary supplement in the US. Recently, regulatory
agencies in France and Spain suspended market authorization of a
weight-loss product containing green tea extract because of
hepatotoxicity concerns. This was followed by publication of adverse
event case reports involving green tea products. In response, the US
Pharmacopeia (USP) Dietary Supplement Information Expert Committee (DSI
EC) systematically reviewed the safety information for green tea
products in order to re-evaluate the current safety class to which
these products are assigned. DSI EC searched PubMed (January 1966-June
2007) and EMBASE (January 1988-June 2007) for clinical case reports and
animal pharmacological or toxicological information. Reports were also
obtained from a diverse range of other sources, including published
reviews, the US FDA MedWatch programme, USP’s MEDMARX((R))
adverse event reporting system, the Australian Therapeutic Goods
Administration, the UK Medicines and Healthcare products Regulatory
Agency, and Health Canada’s Canadian Adverse Drug Reaction
Monitoring Program. Case reports pertaining to liver damage were
evaluated according to the Naranjo causality algorithm scale. In
addition, the Committee analysed information concerning historical use,
regulatory status, and current extent of use of green tea products. A
total of 216 case reports on green tea products were analysed,
including 34 reports concerning liver damage. Twenty-seven reports
pertaining to liver damage were categorized as possible causality and
seven as probable causality. Clinical pharmacokinetic and animal
toxicological information indicated that consumption of green tea
concentrated extracts on an empty stomach is more likely to lead to
adverse effects than consumption in the fed state. Based on this safety
review, the DSI EC determined that when dietary supplement products
containing green tea extracts are used and formulated appropriately the
Committee is unaware of significant safety issues that would prohibit
monograph development, provided a caution statement is included in the
labelling section. Following this decision, USP’s DSI ECs may
develop monographs for green tea extracts, and USP may offer its
verification programmes related to that dietary ingredient.
Just to keep things in perspective, the previous item about green
tea extracts potentially causing liver problems must be balanced
against research showing that green tea is protective against liver
disease. Chinese researchers a value weighted interventional and
observational studies in both Western countries and in China published
between 1989 and 2007. They found “a significant protective role
of green tea against various liver diseases” and “a
positive correlation between green tea intake and attenuation of liver
disease.” Their conclusion? “An increased consumption of
green tea may reduce the risk of liver disease.”
Green tea consumption and liver disease: a systematic review. Liver Int. 2008 May 14. [Epub ahead of print]
Jin X, Zheng RH, Li YM.
Objectives: To present the effect of green tea consumption against
liver disease. Data sources: Interventional and observational studies
both in Western countries and in China and published between the years
1989 and December 2007. Review Methods: The articles were retrieved
from Medline, Embase database, Chinese biomedicine web database and
Chinese scientific journal’s database using proper MESH headings
and assessed by two independent investigators according to established
inclusion criteria. The characteristics and outcomes of the chosen
articles were displayed for further analysis and the quality of each
study was also evaluated according to the widely acknowledged criteria.
P<0.05 was defined as statistically significant in all enrolled
trials. Results: Ten qualified studies (eight from China, one from
Japan and the other from the USA) with various outcomes such as liver
cancer, cirrhosis and fatty liver disease were finally chosen. Among
them, study designs differed in that there were four
randomized-controlled clinical trials, two cohort, one case-control and
three cross-sectional studies. The heterogeneity in the study design,
outcomes, cofounders and amount of tea consumption precluded further
meta-analysis. Nevertheless, eight studies showed a significant
protective role of green tea against various liver diseases as
determined by relative risk/odds ratio or P-value and among them, four
studies showed a positive correlation between green tea intake and
attenuation of liver disease. Moreover, the other two studies also
presented the protective tendency of green tea against liver disease.
Conclusions: An increased consumption of green tea may reduce the risk
of liver disease.
Japanese researchers explored the effect of tea catechins and
regular exercise and the aging associated declining physical
performance in mice. The endurance capacity of mice as measured by
running time decreased by 17% in control mice, while those fed green
tea catechins (0.35%) suffered no decline in endurance. The authors
concluded “long-term intake of catechins, together with habitual
exercise, is beneficial for suppressing the age-related decline in
physical performance and energy metabolism, and these effects are due,
at least in part, to improved mitochondrial function in skeletal
Tea catechin ingestion combined with habitual exercise suppresses
the aging-associated decline in physical performance in
Am J Physiol Regul Integr Comp Physiol. 2008 May 14. Murase T, Haramizu S, Ota N, Hase T.
Catechins, which are abundant in green tea, possess a variety of
biologic actions, and their clinical application has been extensively
investigated. In this study, we examined the effects of tea catechins
and regular exercise on the aging-associated decline in physical
performance in senescence-accelerated prone mice (SAMP1) and
age-matched senescence-accelerated resistant mice (SAMR1). The
endurance capacity of SAMR1 mice, measured as the running time to
exhaustion, tended to increase over the 8-week experimental period,
whereas that of SAMP1 mice decreased by 17%. On the other hand, the
endurance capacity of SAMP1 mice fed 0.35% (w/w) catechins remained at
the initial level and was significantly higher than that of SAMP1 mice
not fed catechins. In SAMP1 mice fed catechins and given exercise,
oxygen consumption was significantly increased, and there was an
increase in skeletal muscle fatty acid beta-oxidation. The mRNA levels
of mitochondria-related molecules, such as peroxisome
proliferator-activated receptor-gamma coactivator-1, cytochrome c
oxidase-II, III, and IV in skeletal muscle were also higher in SAMP1
mice given both catechins and exercise. Moreover, oxidative stress
measured as thiobarbituric reactive substances was lower in SAMP1
groups fed catechins than in the SAMP1 control group. These results
suggest that long-term intake of catechins, together with habitual
exercise, is beneficial for suppressing the aging-related decline in
physical performance and energy metabolism, and that these effects are
due, at least in part, to improved mitochondrial function in skeletal
muscle. Key words: energy metabolism, exercise, green tea,
mitochondria, oxidative stress.