Research - Green Tea
Circulating Hypoxia Responsive microRNAs (HRMs) and Wound Healing Potentials of Green Tea in Diabetic and Nondiabetic Rat Models
Hadeel A. Al-Rawaf,1,2 Sami A. Gabr,1 and Ahmad H. Alghadir
Green tea (Camellia sinensis) has many biological activities and may promote diabetic wound healing by regulation of circulating hypoxia responsive microRNAs (HRMs) which triggers the wound repairing process in diabetic and nondiabetic wounds. Thus, in this study, the potential effects of green tea extract (GTE) on the expression of miRNAs; miR-424, miR-199a, miR-210, miR-21, and fibrogenitic markers; hydroxyproline (HPX), fibronectin (FN), and nitric oxide (NO) were evaluated in wounds of diabetic and nondiabetic rats. The animals were topically treated with vaseline, 0.6% GTE, and 5%w/w povidone iodine (standard control). HPX, FN, and NO levels and microRNAs, miR-424, miR-210, miR-199a, and miR-21, were estimated in wound tissues using colorimetric, immunoassay, and molecular PCR analysis. In vitro analysis was performed to estimate active constituents and their antioxidant activities in methanolic green teat extract (GTE). Wounds treated with green tea, a dose of 0.6, healed significantly earlier than those treated with standard vehicle and vaseline treated diabetic wounds. Higher expressions of HRMs, miR-199a, and miR-21, and lower expression of HRMs, miR-424 and miR-210, were significantly reported in tissues following treatment with green tea extract compared to standard control vehicle. The tissues also contained more collagen expressed as measures of HPX, FN, and NO and more angiogenesis, compared to wounds treated with standard control vehicle. Diabetic and nondiabetic wounds treated with green tea (0.6%) for three weeks had lesser scar width and greater re-epithelialization in shorter periods when compared to standard control vehicle. Expression of HRMs, miR-199a, miR-21, and HRMs and miR-424 and miR-210 correlated positively with HPX, fibronectin, NO, better scar formation, and tensile strength and negatively with diabetes. In addition to antidiabetic and antioxidant activities of green tea components, GTE showed angiogenesis promoting activity in diabetic wound healing. In conclusion, Camellia sinensis extracts in a dose of 0.6% significantly promote more collagen and fibronectin deposition with higher expression of NO, promoting angiogenesis process via molecular controlling of circulating hypoxia responsive microRNAs: miR-424, miR-210, miR-199a, and miR-21 in diabetic and nondiabetic wounds. Our results support a functional role of circulating hypoxia responsive microRNAs: miR-424, miR-210, miR-199a, and miR-21 as potential therapeutic targets in angiogenesis and vascular remodeling in diabetic wound healing.
Source : Journal Evidence Based Complementary and Alternative Medicine
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Epigallocatechin-3-Gallate Protects against Homocysteine-Induced Brain Damage in Rats
Lili Wang, Xuan Tian
High levels of homocysteine are implicated in many neurovascular and neurodegeneration diseases. Epigallocatechin 3-gallate (EGCG), one of green tea polyphenols, has potential anti-oxidative and anti-inflammatory activities. However, it has not been explored whether EGCG has an effect on homocysteine-induced neuro-inflammation and neurodegeneration. In this study, we investigated the effects of EGCG on memory deficit, oxidative stress, neuro-inflammation, and neurodegeneration in hyper-homocysteinemic rats after a 2 wk homocysteine injection by vena caudalis. We found that supplementation of EGCG could rescue deficit of spatial memory induced by homocysteine. Treatment of EGCG significantly reduced the expression of malondialdehyde, glial fibrillary acidic protein, tumor necrosis factor-α, and interleukin-1β and increased glutathione level in the homocysteine-treated group. In TdT-mediated dUTP nick end labeling (TUNEL) assay and Fluoro-Jade B staining, supplementation of EGCG could attenuate the apoptotic neurons and neurodegeneration. Interestingly, EGCG significantly ameliorated homocysteine-induced cerebrovascular injury. Our data suggest that EGCG could be a promising candidate for arresting homocysteine-induced neurodegeneration and neuro-inflammation in the brain.
Source : Planta Medica Journal
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Epigallocatechin-3-gallate (EGCG) inhibits imiquimod-induced psoriasis-like inflammation of BALB/c mice
- Shuangshuang Zhang†,
- Xiangdong Liu†,
- Lihong Mei,
- Hongfeng Wang and
- Fang Fang
Background Psoriasis is a chronic inflammatory immune disease with undefined pathogenesis. It is associated with T cells, and the IL-23/IL17 axis is believed to be crucial in the pathogenesis. The present treatments have side effects that influence the compliance of patients. Tea polyphenol is extracted from tea polyphenols, and its main active ingredient is Epigallocatechin-3-gallate (EGCG), which has been shown to have antioxidant, anti-tumor, and anti-ultraviolet radiation effects. Here, we aim to report that EGCG can inhibit imiquimod (IMQ)-induced psoriasis-like inflammation.
Methods We used BALB/c mice, which were topically treated with IMQ for 6 consecutive days, as a psoriasis mouse model. Topical application of EGCG and treatment with EGCG were conducted in the experiments. Then observed the effects of the two methods on psoriasis-like mice dermatitis. Statistics are presented as the means ± standard error of mean (SEM) and compared using unpaired two-tailed Student’s t tests or one-way ANOVA.
Results Topical application of EGCG alleviated psoriasiform dermatitis, improved the skin pathological structure by reduce the expression of epidermal PCNA, promoted the expression of caspase-14. Treatment with EGCG attenuated skin inflammation, accompanied by reduced infiltrations of T cells; reduced percentages of CD11c+DC in the composition of immunocytes of spleens; reduced levels of interleukin (IL)-17A, IL-17F, IL-22, IL-23 and malondialdehyde (MDA) in plasma; increased percentages of CD4+ T cells in the composition of immunocytes of spleens; and increased bioactivities of superoxide dismutase (SOD) and catalase (CAT) in plasma.
Conclusions All the results demonstrated that EGCG had anti-inflammatory, immune regulatory and antioxidant effects. It is a promising intervention in psoriasis in the future.
Source : BMC Complementary and Alternative Medicine
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Anti-cancer effect of (-)-epigallocatechin-3-gallate (EGCG) in head and neck cancer through repression of transactivation and enhanced degradation of β-catenin
- Yoo Seob Shina, b, 1,
- Sung Un Kanga, b, 1,
- Ju Kyeong Parka, b,
- Yang Eun Kima, b,
- Yeon Soo Kima,
- Seung Joon Baekc,
- Seong-Ho Leed,
- Chul-Ho Kima, b
Background and PurposeAberrant expression of β-catenin is highly associated with progression of various cancers including head and neck cancer (HNC). Green tea is most commonly used beverage in the world and one of the more bioactive compounds is the antioxidant epigallocatechin gallate (EGCG). This study was performed to investigate the mechanism by which EGCG inhibits the growth of HNC, focusing on the modulation of the expression and activity of β-catenin.
MethodsIn vitro effects of EGCG on the transcription, translation, or degradation of β-catenin were investigated. Antitumor effects of EGCG in vivo were evaluated in a syngeneic mouse model and β-catenin expression was checked in HNC patients’ samples.
Resultsβ-catenin expression was elevated in tumor samples of HNC patients. EGCG induced apoptosis in KB and FaDu cells through the suppression of β-catenin signaling. Knockdown of β-catenin using siRNA enhanced the proapoptotic activities of EGCG. EGCG decreased mRNA and transcriptional activity of β-catenin in p53 wild-type KB cells. EGCG also enhanced the ubiquitination and proteasomal degradation of β-catenin. The suppression of β-catenin and consequent apoptosis were observed in response to EGCG treatment in a syngeneic mouse model. In conclusion, we report that EGCG inhibits β-catenin expression through multiple mechanisms including decreased transcription and increased ubiquitin-mediated 26S proteasomal degradation.
ConclusionThis study proposes a novel molecular rationale for antitumor activities of green tea in HNCs.
Source : Journal Phytomedicine
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Dietary epicatechin intake and 25-y risk of cardiovascular mortality: the Zutphen Elderly Study1,2,3
- James I Dower4,5,
- Johanna M Geleijnse4,5,
- Peter CH Hollman4,5,*,
- Sabita S Soedamah-Muthu4, and
- Daan Kromhout4
Background: Prospective cohort studies have shown that the consumption of cocoa and tea is associated with lower risk of cardiovascular diseases (CVDs), and cocoa and tea have been shown to improve CVD risk factors in randomized controlled trials. Cocoa and tea are major dietary sources of the flavan-3-ol epicatechin.
Objective: We investigated the associations of dietary epicatechin intake with 25-y CVD mortality in elderly Dutch men.
Design: We used data from the Zutphen Elderly Study, which was a prospective cohort study of 774 men aged 65–84 y in 1985. Epicatechin intake was estimated 4 times in 15 y with the use of the crosscheck dietary history method. Time-dependent Cox proportional hazards models were used to investigate repeated measures of epicatechin intake in relation to 25-y CVD mortality.
Results: Mean intake of epicatechin was 15.2 ± 7.7 mg/d, and the major dietary sources were tea (51%), apples (28%), and cocoa (7%). During 25 y of follow-up, 329 men died from CVD, 148 died from coronary heart disease (CHD), and 72 men died from stroke. Risk of CHD mortality was 38% lower in men in the top tertile of epicatechin intake than in men in the bottom tertile of epicatechin intake (HR: 0.62; 95% CI: 0.39, 0.98). Epicatechin intake was also significantly associated with 46% lower risk of CVD mortality in men with prevalent CVD (HR: 0.54; 95% CI: 0.31, 0.96) but not in men who were free of CVD.
Conclusions: We show, for the first time to our knowledge, that epicatechin intake is inversely related to CHD mortality in elderly men and to CVD mortality in prevalent cases of CVD. More studies are needed before conclusions can be drawn.
Source : American Journal of Clinical Nutrition
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Effects of green tea (Camellia sinensis) mouthwash containing 1% tannin on dental plaque and chronic gingivitis: a double-blinded, randomized, controlled trial.
Radafshar G1,2, Ghotbizadeh M1, Saadat F3,4, Mirfarhadi N1.
AbstractAIM:The aim of the present study was to explore the effects of Iranian green tea mouthwash containing 1% tannin on dental plaque and chronic gingivitis.
METHODS:In this randomized, double-blinded, parallel, controlled clinical trial, 40 volunteer dental students with a gingival index ≥1 were enrolled. At baseline, gingival, plaque, and bleeding indices were recorded and all the participants received dental polishing. Based on random allocation, 20 participants used the test and 20 used chlorhexidine mouthwash with no change in regular toothbrushing methods. The participants were asked to use 15 mL of the respective mouthwash for 1 min, twice a day for 28 days. All indices, as well as stain index, were recorded after 1 and 4 weeks post-rinsing. Data were analyzed using repeated-measures ANOVA and Bonferroni tests.
RESULTS:Significant in-group differences, but not between-group differences, were observed in all indices after 1 and 4 weeks compared to baseline. The test mouthwash resulted in significantly less tooth staining than the control.
CONCLUSION:The 1% tannin green tea mouthwash could be a safe and feasible adjunct to mechanical plaque control. The tested green tea mouthwash could be considered a good alternative for chlorhexidine in contraindicating situations.
Source : J Investig Clin Dent.
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Epicatechin and Quercetin Affects Some Biomarkers of Endothelial Dysfunction and Inflammation in (Pre)Hypertensive Adults: A Randomized Double-Blind, Placebo-Controlled, Crossover Trial1,2
James I Dower3,4, Johanna M Geleijnse3,4, Lieke Gijsbers3,4,Casper Schalkwijk3,5, Daan Kromhout4, and Peter C Hollman3,4,*
Background: Consumption of flavonoid-rich foods such as cocoa and tea may reduce cardiovascular disease risk. The flavonoids epicatechin (in cocoa and tea) and quercetin (in tea) probably play a role by reducing endothelial dysfunction and inflammation, 2 main determinants of atherosclerosis.
Objective: We studied the effects of supplementation of pure epicatechin and quercetin on biomarkers of endothelial dysfunction and inflammation.
Methods: Thirty-seven apparently healthy (pre)hypertensive men and women (40–80 y) participated in a randomized, double-blind, placebo-controlled crossover trial. Participants ingested (-)-epicatechin (100 mg/d), quercetin-3-glucoside (160 mg/d), or placebo capsules for a period of 4 wk, in random order. Plasma biomarkers of endothelial dysfunction and inflammation were measured at the start and end of each 4-wk intervention period. The differences in changes over time between the intervention and placebo periods (Δintervention − Δplacebo) were calculated and tested with a linear mixed model for repeated measures.
Results: Epicatechin changed Δepicatechin − Δplacebo for soluble endothelial selectin (sE-selectin) by −7.7 ng/mL (95% CI: −14.5, −0.83; P = 0.03) but did not significantly change this difference (−0.30; 95% CI: −0.61, 0.01; P = 0.06) for thez score for endothelial dysfunction. Quercetin changed Δquercetin − Δplacebo for sE-selectin by −7.4 ng/mL (95% CI: −14.3, −0.56; P = 0.03), that for IL-1β by −0.23 pg/mL (95% CI: −0.40, −0.06; P = 0.009), and that for the z score for inflammation by −0.33 (95% CI: −0.60, −0.05; P = 0.02).
Conclusions: In (pre)hypertensive men and women, epicatechin may contribute to the cardioprotective effects of cocoa and tea through improvements in endothelial function. Quercetin may contribute to the cardioprotective effects of tea possibly by improving endothelial function and reducing inflammation.
Source : Journal Nutrition
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Differential prooxidative effects of the green tea polyphenol, (–)-epigallocatechin-3-gallate, in normal and oral cancer cells are related to differences in sirtuin 3 signaling
- Ling Tao1,
- Jong-Yung Park1 and
- Joshua D. Lambert1,2,*
We have previously reported that the green tea catechin, (–)-epigallocatechin-3-gallate (EGCG), can induce oxidative stress in oral cancer cells but exerts antioxidant effects in normal cells. Here, we report that these differential prooxidative effects are associated with sirtuin 3 (SIRT3), an important mitochondrial redox modulator.
Methods and results
EGCG rapidly induced mitochondria-localized reactive oxygen species in human oral squamous carcinoma cells (SCC-25, SCC-9) and premalignant leukoplakia cells (MSK-Leuk1), but not in normal human gingival fibroblast cells (HGF-1). EGCG suppressed SIRT3 mRNA and protein expression, as well as, SIRT3 activity in SCC-25 cells, whereas it increased SIRT3 activity in HGF-1 cells. EGCG selectively decreased the nuclear localization of the estrogen-related receptor α (ERRα), the transcription factor regulating SIRT3 expression, in SCC-25 cells. This indicates that EGCG may regulate SIRT3 transcription in oral cancer cells via ERRα. EGCG also differentially modulated the mRNA expressions of SIRT3-associated downstream targets including glutathione peroxidase 1 and superoxide dismutase 2 in normal and oral cancer cells.
SIRT3 represents a novel potential target through which EGCG exerts differential prooxidant effects in cancer and normal cells. Our results provide new biomarkers to be further explored in animal studies.
Source : Molecular Nutrition and Food Research
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Green tea and type 2 diabetes
Jae-Hyung Park, , Jae-Hoon Bae, Sung-Soon Im, Dae-Kyu Song
Department of Physiology, Keimyung University School of Medicine, Daegu, Korea
Green tea and coffee consumption have been widely popular worldwide. These beverages contain caffeine to activate the central nervous system by adenosine receptor blockade, and due to the caffeine, addiction or tolerance may occur. In addition to this caffeine effect, green tea and coffee consumption have always been at the center of discussions about human health, disease, and longevity. In particular, green tea catechins are involved in many biological activities such as antioxidation and modulation of various cellular lipid and proteins. Thus, they are beneficial against degenerative diseases, including obesity, cancer, cardiovascular diseases, and various inflammatory diseases. Some reports also suggest that daily consumption of tea catechins may help in controlling type 2 diabetes. However, other studies have reported that chronic consumption of green tea may result in hepatic failure, neuronal damage, and exacerbation of diabetes, suggesting that interindividual variations in the green tea effect are large. This review will focus on the effect of green tea catechins extracted from the Camellia sinensis plant on type 2 diabetes and obesity, and the possible mechanistic explanation for the experimental results mainly from our laboratory. It is hoped that green tea can be consumed in a suitable manner as a supplement to prevent the development of type 2 diabetes and obesity.
Source : Intergrative Medicine Journal
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Green Tea Consumption Affects Cognitive Dysfunction in the Elderly: A Pilot Study
Kazuki Ide 1, Hiroshi Yamada 1,* , Norikata Takuma 2, Mijong Park 1, Noriko Wakamiya 1, Junpei Nakase 3, Yuuichi Ukawa 3 and Yuko M. Sagesaka 3
Green tea is known to have various health benefits for humans. However, the effect of green tea consumption on cognitive dysfunction remains to be clinically verified. We conducted a clinical study to investigate the effects of green tea consumption on cognitive dysfunction. Twelve elderly nursing home residents with cognitive dysfunction (Mini-Mental State Examination Japanese version (MMSE-J) score: <28) participated in the study (2 men, 10 women; mean age, 88 years). The participants consumed green tea powder 2 g/day for 3 months. After three months of green tea consumption, the participants’ MMSE-J scores were significantly improved (before, 15.3 ± 7.7; after, 17.0 ± 8.2; p = 0.03). This result suggests that green tea consumption may be effective in improving cognitive function or reducing the progression of cognitive dysfunction; however, long-term large-scale controlled studies are needed to further clarify the effect.
Source : Journal Nutrients
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Interaction of Some Commercial Teas with Some Carbohydrate Metabolizing Enzymes Linked with Type-2 Diabetes: A Dietary Intervention in the Prevention of Type-2 Diabetes
Ganiyu Oboh,1 Omodesola O. Ogunruku,1,2 Funke O. Ogidiolu,1 Adedayo O. Ademiluyi,1 Bukola C. Adedayo,1 and Ayokunle O. Ademosun1
1Functional Foods and Nutraceuticals Unit, Biochemistry Department, Federal University of Technology, PMB 704, Akure, Nigeria
2Biochemistry Department, Obafemi Awolowo University, Ile-Ife, Nigeria
This study is aimed at assessing the inhibitory effect of teas on key enzymes (alpha-amylase and alpha-glucosidase) linked with type-2 diabetes and their antioxidant properties. Four samples of three brands were used; infusions of green tea (GT), 2 brands of black tea (BT), and a formulated herbal preparation for diabetes (ADT) (white tea, Radix Puerariae, Radix ophiopogonis, hawthorn berry, Chinese yam, and fragrant Solomon seal rhizome) were prepared and subsequently analyzed for their total phenol, ascorbic acid contents, antioxidant properties (2,2-Azizobis (3-Ethylbenzo-Thiazoline~6-sulfonate) “ABTS” scavenging ability and ferric reducing antioxidant property), and inhibition of pancreatic-alpha-amylase and intestinal-alpha-glucosidase in vitro. The study revealed that GT had the highest total phenol content, ascorbic acid content, ABTS* scavenging ability, and ferric reducing ability. Furthermore, all the teas inhibited Fe2+ and sodium nitroprusside induced lipid peroxidation in pancreas, with GT having the highest inhibitory effect. Conversely, there was no significant difference ( P>0.05) in the inhibitory effects of the teas on alpha-amylase and alpha-glucosidase. The antidiabetic property of the teas could be attributed to their inhibitory effect on carbohydrate hydrolyzing enzymes implicated in diabetes and their antioxidant activities.
Source : Evidence Based Complementary and Alternative Medicine
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Three Herbs for Cognition
Three HerbClips in this issue focus on cognition. HC 011456-496 covers a meta-analysis of bacopa (Bacopa monnieri; Scrophulariaceae).1 Bacopa has been used in Ayurvedic medicine for centuries to improve memory and intellect. Nine clinical trials were included in the meta-analysis, with a total of 231 subjects receiving bacopa and 206 subjects receiving placebo. Memory function (6 studies) and attention (7 studies) were the outcome effects. The authors conclude that bacopa may aid in improving cognitive function, particularly attention speed, but that more study is needed, especially a "head to head" trial with a proven existing medication and standardized bacopa extract. As mentioned in the previous HC News, a green tea (Camellia sinensis; Theaceae) extract was found to enhance working memory between the frontal and parietal brain regions in 12 healthy subjects (See HC 041431-496).2 The authors suggest that green tea extract could be used to treat cognitive impairments, such as dementia, by creating short-term plasticity between the brain regions. This increased connectivity could provide enhanced cognitive function for both healthy individuals as well as those with cognitive impairment. The study used a whey-based soft drink. Additionally studies with a standardized green tea extract are warranted. HC 121314-496 reviews a pilot study on pomegranate (Punica granatum; Lythraceae) supplement POMx™ (POM Wonderful; Los Angeles, California) which demonstrated that the supplement may improve postoperative cognitive dysfunction (POCD) for patients who have had heart surgery.3 Memory retention can be mildly to severely affected after heart surgery, possibly due to anesthesia or lack of oxygen/glucose to the brain. In this small study (5 active; 5 placebo), the researchers found that the pomegranate group was protected against POCD and even improved their memory retention compared to baseline.
Cognition domains include "motor functioning, attention, language, memory, executive control, vision, emotion, sensory functions, and consciousness."1 With an increased aging population, evidence of cognitive decline has also increased. Other impairments among the younger generations, such as attention deficit hyperactivity disorder, have had a notable escalation as well. Finding ways to enhance brain activity, such as word puzzles, studying new subjects, exercising to increase oxygen capacity, and some form of meditation to relax the mind, can maintain and even enhance cognitive function. Bacopa, green tea, and pomegranate, among other herbs, can also support the brain's various processes.
1Kongkeaw C, Dilokthornsakul P, Thanarangsarit P, Limpeanchob N, Scholfield CN. Meta-analysis of randomized controlled trials on cognitive effects of Bacopa monnieri extract. J Ethnopharmacol. 2014;151(1):528-535.
2Schmidt A, Hammann F, Wölnerhanssen B, et al. Green tea extract enhances parieto-frontal connectivity during working memory processing. Psychopharmacology. 2014; [epub ahead of print]. doi: 10.1007/s00213-014-3526-1.
3Ropacki SA, Patel SM, Hartman RE. Pomegranate supplementation protects against memory dysfunction after heart surgery: A pilot study. Evid Based Complement Alternat Med. 2013;2013:932401. doi: 10.1155/2013/932401.
Source : HerbClip-ABC
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Green tea could reduce pancreatic cancer risk: Study explains how
Green tea and its extracts have been widely touted as potential treatments for cancer, as well as several other diseases. But scientists have struggled to explain how the green tea and its extracts may work to reduce the risk of cancer or to slow the growth of cancer cells. A study recently published online by the journal, Metabolomics, offers an explanation that researchers say could open a new area of cancer-fighting research. The study reports that EGCG, the active biologic constituent in green tea, changed the metabolism of pancreatic cancer cells by suppressing the expression of an enzyme associated with cancer, LDHA.
The researchers also found an enzyme inhibitor, oxamate, which is known to reduce LDHA activity, operated in the same manner: It also disrupted the pancreatic cancer cells metabolic system.
"Scientists had believed they needed a molecular mechanism to treat cancer, but this study shows that they can change the metabolic system and have an impact on cancer," said Wai-Nang Lee, MD, corresponding author of the study and a Los Angeles Biomedical Research Institute (LA BioMed) lead researcher. "By explaining how green tea's active component could prevent cancer, this study will open the door to a whole new area of cancer research and help us understand how other foods can prevent cancer or slow the growth of cancerous cells."
Using sophisticated metabolic profiling methods, the researchers found EGCG disrupted the balance of "flux" throughout the cellular metabolic network. Flux is the rate of turnover of molecules through a metabolic pathway. The researchers found the EGCG disrupted this balance in the same manner that oxamate, a known LDHA inhibitor, did.
Based on this finding, they concluded that both EGCG and oxamate reduced the risk of cancer by suppressing the activity of LDHA, a critical enzyme in cancer metabolism, thereby disrupting the balance in the cancer cells metabolic functions.
"This is an entirely new way of looking at metabolism," said Dr. Lee. "It is no longer a case of glucose goes in and energy comes out. Now we understand how cancer cell metabolism can be disrupted, and we can examine how we can use this knowledge to try to alter the course of cancer or prevent cancer."
Source : Science Daily
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(+)-Catechin protects dermal fibroblasts against oxidative stress-induced apoptosis
Tomoko Tanigawa, Shigeyuki Kanazawa, Ryoko Ichibori, Takashi Fujiwara, Takuya Magome, Kenta Shingaki, Shingo Miyata, Yuki Hata, Koichi Tomita, Ken Matsuda, Tateki Kubo, Masaya Tohyama, Kenji Yano and Ko Hosokawa
Oxidative stress has been suggested as a mechanism underlying skin aging, as it triggers apoptosis in various cell types, including fibroblasts, which play important roles in the preservation of healthy, youthful skin. Catechins, which are antioxidants contained in green tea, exert various actions such as anti-inflammatory, anti-bacterial, and anti-cancer actions. In this study, we investigated the effect of (+)-catechin on apoptosis induced by oxidative stress in fibroblasts.
Fibroblasts (NIH3T3) under oxidative stress induced by hydrogen peroxide (0.1 mM) were treated with either vehicle or (+)-catechin (0-100 muM). The effect of (+)-catechin on cell viability, apoptosis, phosphorylation of c-Jun terminal kinases (JNK) and p38, and activation of caspase-3 in fibroblasts under oxidative stress were evaluated.
Hydrogen peroxide induced apoptotic cell death in fibroblasts, accompanied by induction of phosphorylation of JNK and p38 and activation of caspase-3. Pretreatment of the fibroblasts with (+)-catechin inhibited hydrogen peroxide-induced apoptosis and reduced phosphorylation of JNK and p38 and activation of caspase-3.
(+)-Catechin protects against oxidative stress-induced cell death in fibroblasts, possibly by inhibiting phosphorylation of p38 and JNK. These results suggest that (+)-catechin has potential as a therapeutic agent for the prevention of skin aging.
Source : BMC Complementary and Alternative Medicine
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Green tea extract enhances parieto-frontal connectivity during working memory processing
André Schmidt1, 2, Felix Hammann3, Bettina Wölnerhanssen3, Anne Christin Meyer-Gerspach3, Jürgen Drewe3, Christoph Beglinger3 and Stefan Borgwardt1, 2, 4
(1)Department of Psychiatry (UPK), University of Basel, Wilhelm Klein Str. 27, 4012 Basel, Switzerland
(2)Medical Image Analysis Center, Schanzenstrasse 55, 4031 Basel, Switzerland
(3)Department of Gastroenterology, University Hospital Basel, 4031 Basel, Switzerland
(4)Department of Psychosis Studies, Institute of Psychiatry, King’s College London, London, UK
It has been proposed that green tea extract may have a beneficial impact on cognitive functioning, suggesting promising clinical implications. However, the neural mechanisms underlying this putative cognitive enhancing effect of green tea extract still remain unknown.
Objectives This study investigates whether the intake of green tea extract modulates effective brain connectivity during working memory processing and whether connectivity parameters are related to task performance.
Material and methods Using a double-blind, counterbalanced, within-subject design, 12 healthy volunteers received a milk whey-based soft drink containing 27.5 g of green tea extract or a milk whey-based soft drink without green tea as control substance while undergoing functional magnetic resonance imaging. Working memory effect on effective connectivity between frontal and parietal brain regions was evaluated using dynamic causal modeling.
Results Green tea extract increased the working memory induced modulation of connectivity from the right superior parietal lobule to the middle frontal gyrus. Notably, the magnitude of green tea induced increase in parieto-frontal connectivity positively correlated with improvement in task performance.
Conclusions Our findings provide first evidence for the putative beneficial effect of green tea on cognitive functioning, in particular, on working memory processing at the neural system level by suggesting changes in short-term plasticity of parieto-frontal brain connections. Modeling effective connectivity among frontal and parietal brain regions during working memory processing might help to assess the efficacy of green tea for the treatment of cognitive impairments in psychiatric disorders such as dementia
Source : Psychopharmacology
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A systematic review of anti-obesity medicinal plants - an update
Shirin Hasani-Ranjbar 1,2, Zahra Jouyandeh2 and Mohammad Abdollahi3*
1 Obesity & Eating Habits Research Center, Endocrinology & Metabolism Research Institute, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran
2 Endocrinology & Metabolism Research Center, Endocrinology & Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran
3 Faculty of Pharmacy, and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran, Iran
Obesity is the most prevalent health problem affecting all age groups, and leads to many complications in the form of chronic heart disease, diabetes mellitus Type 2 and stroke. A systematic review about safety and efficacy of herbal medicines in the management of obesity in human was carried out by searching bibliographic data bases such as, PubMed, Scopus, Google Scholar, Web of Science, and IranMedex, for studies reported between 30th December 2008 to 23rd April 2012 on human or animals, investigating the beneficial and harmful effects of herbal medicine to treat obesity. Actually we limited our search to such a narrow window of time in order to update our article published before December of 2008. In this update, the search terms were “obesity” and (“herbal medicine” or “plant”, “plant medicinal” or “medicine traditional”) without narrowing or limiting search items. Publications with available abstracts were reviewed only. Total publications found in the initial search were 651. Total number of publications for review study was 33 by excluding publications related to animals study.
Studies with Nigella Sativa, Camellia Sinensis, Crocus Sativus L, Seaweed laminaria Digitata, Xantigen, virgin olive oil, Catechin enriched green tea, Monoselect Camellia, Oolong tea, Yacon syrup, Irvingia Gabonensi, Weighlevel, RCM-104 compound of Camellia Sinensis, Pistachio, Psyllium fibre, black Chinese tea, sea buckthorn and bilberries show significant decreases in body weight. Only, alginate-based brown seaweed and Laminaria Digitata caused an abdominal bloating and upper respiratory tract infection as the side effect in the trial group. No other significant adverse effects were reported in all 33 trials included in this article.
In conclusion, Nigella Sativa, Camellia Synensis, Green Tea, and Black Chinese Tea seem to have satisfactory anti-obesity effects. The effect size of these medicinal plants is a critical point that should be considered for interpretation. Although there was no report for side effect in these trials, we believe that safety of these plants still remains to be elucidated by further long-term studies.
Source : BMC Complementary and Alternative Medicine
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Combination of Selenium and Green Tea Improves the Efficacy of Chemoprevention in a Rat Colorectal Cancer Model by Modulating Genetic and Epigenetic Biomarkers
Ying Hu mail, Graeme H. McIntosh, Richard K. Le Leu, Laura S. Nyskohus, Richard J. Woodman,Graeme P. Young
Dietary supplementation of selenium and green tea holds promise in cancer prevention. In this study, we evaluated the efficacies of selenium and green tea administered individually and in combination against colorectal cancer in an azoxymethane (AOM)-induced rat colonic carcinogenesis model and determined the underlying mechanisms of the protection. Four-week old Sprague-Dawley male rats were fed with diets containing 0.5% green tea extract, 1ppm selenium as selenium-enriched milk protein, or combination of 1ppm selenium and 0.5% green tea extract. Animals received 2 AOM (15 mg/kg) treatments to induce colonic oncogenesis. Rats were killed 8 or 30 wk later after the last AOM to examine the effect of dietary intervention on aberrant crypt foci (ACF) formation or tumor development. On sacrifice, colons were examined for ACF and tumors, the mRNA levels of SFRP5 and Cyclin D1, and the proteins levels of ß-catenin, COX-2, Ki-67, DNMT1 and acetyl histone H3. The combination of selenium and green tea resulted in a significant additive inhibition of large ACF formation, this effect was greater than either selenium or green tea alone, P<0.01; the combination also had a significant additive inhibition effect on all tumor endpoints, the effect of the combination diet on tumor incidence, multiplicity and size was greater than selenium or green tea alone, P<0.01. Rats fed the combination diet showed marked reduction of DNMT1 expression and induction of histone H3 acetylation, which were accompanied by restoration of SFRP5 mRNA in normal-appearing colonic crypts. The combination diet also significantly reduced ß-catenin nuclear translocation, Cyclin D1 expression and cell proliferation. These data show, for the first time, that combination of selenium and green tea is more effective in suppressing colorectal oncogenesis than either agent alone. The preventive effect is associated with regulation of genetic and epigenetic biomarkers implicated in colonic carcinogenesis.
Source : Plos One
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On the Fatigue-Reducing Effects of Green Tea
Eri WATANABE1), Mari KIMURA1), Jiro IMANISHI2)
1) Department of Immunology, Kyoto Prefectural University of Medicine
2) MUIM Center for Integrative Medicine, Meiji University of Integrative Medicine
Objective: On the psychological, physiological and immunological parameters, the effects of green tea drink were comprehensively investigated.
Design: This study used a randomized cross-over design.
Methods: After a 120-minute computer fatigue task, participants were randomized into two groups: one tasked to drink green tea and the other water. Blood collection, measurement of the P300 event related potential and questionnaire were executed three times: before and after the computer fatigue task and then, 30 minute after drinking green tea or water. These data were then compared. High Frequency (HF) and average Low Frequency/High Frequency Ratio (LF/HF) were calculated.
Result: In a state of fatigue, drinking green tea showed dominance of the parasympathetic nervous system, an improvement in their attentiveness, and elevation of NK activity; thereby, reducing fatigue, particularly, mental fatigue.
Conclusion: This study comprehensively showed the fatigue-reducing eggect of green tea in psychological, physiological and immunological parameters. It is hereby, suggested that green tea is indeed, helpful in reducing fatigue.
Source : Japanese Journal of Complementary and Alternative Medicine
Link to Abstract (full study in Japanese)
Inhibition of planktonic and biofilm growth of Candida albicans reveals novel antifungal activity of caffeine
Jayant S. Raut, Nitin M. Chauhan, Ravikumar B. Shinde and S. Mohan Karuppayil*
Infections associated with drug resistant strains and biofilms of Candida albicans have necessitated search for novel molecules with antifungal properties. Caffeine, a major component of the most widely consumed beverages, coffee and tea, is known to possess various biological properties. To evaluate antifungal potential, its effect on growth and virulence attributes of C. albicans was studied using standard methodologies. Caffeine showed fungistatic effect on planktonic growth of two strains of C. albicans (including a fluconazole resistant strain), exhibiting minimum inhibitory concentration (MIC) at 12.5 mM concentration. Around 30% decrease in the adhesion of cells in the presence of caffeine indicated considerable anti-adhesion activity. Caffeine prevented formation of biofilms (which are drug resistant forms), in a concentration dependent manner. Analysis by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) metabolic assay and microscopic observations showed inhibition of biofilm development at 25 mM concentration. This study, for the first time demonstrates dietary chemical, caffeine, as a potential inhibitor of growth, adhesion and biofilm formation by C. albicans.
Source : Journal of Medicinal Plant Research
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Green Tea and cancer Prevention
Chung S. Yanga & Xin Wanga
Extracts of green tea and green tea polyphenols have exhibited inhibitory effects against the formation and development of tumors at different organ sites in animals. These include animal models for skin, lung, oral cavity, esophagus, stomach, intestine, colon, liver, pancreas, bladder, mammary gland, and prostate cancers. In addition to suppressing cell proliferation, promoting apoptosis, and modulating signaling transduction, green tea polyphenols, especially (-)-epigallocatechin-3-gallate, also inhibit cell invasion, angiogenesis, and metastasis. This article reviews data on the cancer preventive activities of green tea polyphenols, possible mechanisms involved, and the relationship between green tea consumption and human cancer risk.
The inhibitory activities of tea and tea catechins against carcinogenesis have been demonstrated in different animal models. Studies in cell lines have also showed that tea catechins can affect a variety of signaling and metabolic pathways. These molecular events could result in cancer cell growth inhibition, apoptosis, and inhibition of invasion, angiogenesis, and metastasis. These activities and the prevention of carcinogenesis have been demonstrated in animal model, but the cancer preventive activity of tea has not been consistently observed in human studies. This may be due to the relatively lower levels of tea consumption by some human populations (than animal studies) and the various confounding factors in epidemiological studies in different populations. The low bioavailability of tea polyphenols, such as EGCG, is also an issue. For agents with low systematic bioavailability, their direct contact with the digestive tract could be important for their cancer preventive activity. This point should be applicable to the activities of EGCG and polyphenols in many other foods or beverages. This information, as well as the biological properties and activities of tea polyphenols reviewed here, may be useful in design of prospective studies and in the selection of the agent, dosage, and biomarkers for intervention trials. The results of such well-designed studies will provide more definitive information on the possible use of tea for the reduction of cancer risk in different populations.
Source : Nutrition and cancer
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Coffee, Green Tea, May Help Lower Stroke Risk
Green tea and coffee may help lower your risk of having a stroke, especially when both are a regular part of your diet, according to research published in Stroke: Journal of the American Heart Association.
"This is the first large-scale study to examine the combined effects of both green tea and coffee on stroke risks," said Yoshihiro Kokubo, M.D., Ph.D., F.A.H.A., F.A.C.C., F.E.S.C., lead author of the study at Japan's National Cerebral and Cardiovascular Center. "You may make a small but positive lifestyle change to help lower the risk of stroke by adding daily green tea to your diet."
Researchers asked 83,269 Japanese adults about their green tea and coffee drinking habits, following them for an average 13 years. They found that the more green tea or coffee people drink, the lower their stroke risks.
- People who drank at least one cup of coffee daily had about a 20 percent lower risk of stroke compared to those who rarely drank it.
- People who drank two to three cups of green tea daily had a 14 percent lower risk of stroke and those who had at least four cups had a 20 percent lower risk, compared to those who rarely drank it.
- People who drank at least one cup of coffee or two cups of green tea daily had a 32 percent lower risk of intracerebral hemorrhage, compared to those who rarely drank either beverage. (Intracerebral hemorrhage happens when a blood vessel bursts and bleeds inside the brain. About 13 percent of strokes are hemorrhagic.)
During the 13-years of follow-up, researchers reviewed participants' hospital medical records and death certificates, collecting data about heart disease, strokes and causes of death. They adjusted their findings to account for age, sex and lifestyle factors like smoking, alcohol, weight, diet and exercise.
Green tea drinkers in the study were more likely to exercise compared to non-drinkers.
Previous limited research has shown green tea's link to lower death risks from heart disease, but has only touched on its association with lower stroke risks. Other studies have shown inconsistent connections between coffee and stroke risks.
Initial study results showed that drinking more than two cups of coffee daily was linked to increasing coronary heart disease rates in age- and sex-adjusted analysis. But researchers didn't find the association after factoring in the effects of cigarette smoking -- underscoring smoking's negative health impact on heart and stroke health.
A typical cup of coffee or tea in Japan was approximately six ounces. "However, our self-reported data may be reasonably accurate, because nationwide annual health screenings produced similar results, and our validation study showed relatively high validity." Kokubo said. "The regular action of drinking tea, coffee, largely benefits cardiovascular health because it partly keeps blood clots from forming."
Tea and coffee are the most popular drinks in the world after water, suggesting that these results may apply in America and other countries.
It's unclear how green tea affects stroke risks. A compound group known as catechins may provide some protection. Catechins have an antioxidant anti-inflammatory effect, increasing plasma antioxidant capacity and anti-thrombogenic effects.
Some chemicals in coffee include chlorogenic acid, thus cutting stroke risks by lowering the chances of developing type 2 diabetes.
Further research could clarify how the interaction between coffee and green tea might help further lower stroke risks, Kokubo said.
Source : Science Daily
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Green tea holds promise against Alzheimer's
Researchers at the University of Michigan have found that a molecule in green tea can prevent misfolding of specific proteins in the brain, which is associated with amyloid plaques in Alzheimer's disease.
The aggregation of these proteins, called metal-associated amyloids, is also associated with other neurodegenerative conditions.
U-M Life Sciences Institute faculty member Mi Hee Lim and an interdisciplinary team of researchers used green tea extract to control the generation of metal-associated amyloid-beta aggregates associated with Alzheimer's disease in the lab.
The specific molecule in green tea, epigallocatechin-3-gallate, also known as EGCG, prevented aggregate formation and broke down existing aggregate structures in the proteins that contained metalsâ€”specifically copper, iron and zinc.
"A lot of people are very excited about this molecule," said Lim, noting that the EGCG and other flavonoids in natural products have long been established as powerful antioxidants.
"We used a multidisciplinary approach. This is the first example of structure-centric, multidisciplinary investigations by three principal investigators with three different areas of expertise," the researcher added.
The research team included chemists, biochemists and biophysicists.
While many researchers are investigating small molecules and metal-associated amyloids, most are looking from a limited perspective, said Lim, assistant professor of chemistry and research assistant professor at the Life Sciences Institute, where her lab is located and her research is conducted.
"But we believe you have to have a lot of approaches working together, because the brain is very complex," she said.
Lim and her team's next step is to "tweak" the molecule and then test its ability to interfere with plaque formation in fruit flies.
"We want to modify them for the brain, specifically to interfere with the plaques associated with Alzheimer's," she said.
The study was published recently in the Proceedings of the National Academy of Sciences.
Source : The Times of India
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Tea, wine extracts disable Alzheimer’s ‘clumps’
Chemicals from green tea and red wine may disrupt a key step in the progression of Alzheimer’s disease, a new study shows.
In early-stage laboratory experiments, the researchers identified the process that allows harmful clumps of protein to latch on to brain cells, causing them to die. They were able to interrupt this pathway using the purified extracts of EGCG from green tea and resveratrol from red wine.
The findings, published in the Journal of Biological Chemistry, offer potential new targets for developing drugs to treat Alzheimer’s disease, which affects some 800,000 people in the UK alone, and for which there is currently no cure.
“This is an important step in increasing our understanding of the cause and progression of Alzheimer’s disease,” says lead researcher Professor Nigel Hooper of the University of Leeds. “It’s a misconception that Alzheimer’s is a natural part of aging; it’s a disease that we believe can ultimately be cured through finding new opportunities for drug targets like this.”
Alzheimer’s disease is characterized by a distinct build-up of amyloid protein in the brain, which clumps together to form toxic, sticky balls of varying shapes. These amyloid balls latch onto the surface of nerve cells in the brain by attaching to proteins on the cell surface called prions, causing the nerve cells to malfunction and eventually die.
“We wanted to investigate whether the precise shape of the amyloid balls is essential for them to attach to the prion receptors, like the way a baseball fits snugly into its glove,” says co-author Jo Rushworth. “And if so, we wanted to see if we could prevent the amyloid balls binding to prion by altering their shape, as this would stop the cells from dying.”
The team formed amyloid balls in a test tube and added them to human and animal brain cells. “When we added the extracts from red wine and green tea, which recent research has shown to re-shape amyloid proteins, the amyloid balls no longer harmed the nerve cells,” says Hooper. “We saw that this was because their shape was distorted, so they could no longer bind to prion and disrupt cell function.
“We also showed, for the first time, that when amyloid balls stick to prion, it triggers the production of even more amyloid, in a deadly vicious cycle,” he adds.
Hooper says that the team’s next steps are to understand exactly how the amyloid-prion interaction kills off neurons. “I’m certain that this will increase our understanding of Alzheimer’s disease even further, with the potential to reveal yet more drug targets,” he says.
“Understanding the causes of Alzheimer’s is vital if we are to find a way of stopping the disease in its tracks,” says Simon Ridley, head of research at Alzheimer’s Research UK, the UK’s leading dementia research charity, which partly funded the study.
“While these early-stage results should not be a signal for people to stock up on green tea and red wine, they could provide an important new lead in the search for new and effective treatments. With half a million people affected by Alzheimer’s in the UK, we urgently need treatments that can halt the disease—that means it’s crucial to invest in research to take results like these from the lab bench to the clinic.”
The Wellcome Trust, Alzheimer’s Research UK, and the Medical Research Council funded the study.
Source : Futurity via Leeds University
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Green Tea, but Not Black Tea, May Protect against Bladder Cancer
Wang X, Lin Y-W, Wang S, et al.
A meta-analysis of tea consumption and the risk of bladder cancer. Urol Int. 2012; [epub ahead of print]. doi: 10.1159/000342804.
Bladder cancer is the 11th most commonly diagnosed cancer in the world.1 Genetic and environmental factors, as well as aging and smoking, are considered risk factors for bladder cancer. Previous research has suggested that tea (Camellia sinensis) may help protect against several types of cancer, including bladder cancer. Epidemiological studies on the association between tea consumption and bladder cancer have yielded mixed results. A 2001 meta-analysis found no correlation between tea consumption and the occurrence of bladder cancer.2 This new meta-analysis includes more recent multicenter and large sample studies which provide greater statistical power.
The authors identified papers published in English between 1980 and March 2012 by searching PubMed, Web of Science, the Cochrane Library, cited references, and previous meta-analyses. The publications were cohort or case-control studies assessing the association between tea consumption and bladder cancer risk, with results including the relative risk (RR) or odds ratio (OR) and its 95% confidence interval (CI), or with sufficient information to calculate the values.
A total of 17 studies with 8,225 cases were included in the analysis; 4 cohort studies and 13 case-control studies. Seven evaluated Asian populations and the remaining 10 assessed Caucasians. Five studies examined black tea consumption, 4 focused on green tea intake, and the other 8 studies did not distinguish the type of tea.
No significant association was detected between tea consumption and bladder cancer risk in the crude data analysis (OR=0.825; 95% CI, 0.652-1.043). However, as a statistically significant heterogeneity was detected (I2=93.3%), a random-effect analysis was conducted. Similar results were found when potentially confounding variables such as age, gender, and smoking status were excluded (OR=1.12; 95% CI, 0.88-1.43), and there was still significant heterogeneity (I2=64.6%). Sensitivity analysis indicated that no single study could influence the results and no publication bias was found among the studies.
Stratified analyses (by gender, study design, ethnicity, and smoking status) indicated that tea consumption was associated with a decreased risk for bladder cancer, although the results were not significant. However, green tea consumption in Asian countries was associated with a statistically significant protective effect against bladder cancer (OR=0.814; 95% CI, 0.678-0.976), while no such association was noted for black tea.
Interestingly, in the subgroup analysis of ethnicity, tea consumption was not associated with a reduced risk of bladder cancer in Asians. The authors suggest that this may be due to the fact that 2 of the 7 Asian population studies only assessed black tea consumption.
The authors noted that none of the studies conducted in Western countries analyzed the correlation between green tea consumption and bladder cancer risk. They acknowledged that the majority of the included studies analyzed "tea" consumption in general rather than the specific type of tea, which may have resulted in inaccurate estimates. Selection bias, recall bias, and ethnic differences in bladder cancer risk cannot be ruled out. Also, the differences in study design may have biased the results since both cohort and case-control studies were included. Other limitations of this analysis are the exclusion of non-English language publications and studies that the authors deemed to have provided insufficient information.
The authors conclude that their analysis "indicated that green tea may have a protective effect on bladder cancer in Asian people," but that "no such correlation was detected between black tea and bladder cancer."
1Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D. Global cancer statistics. CA Cancer J Clin. 2011;61(2):69-90.
2Zeegers MP, Tan FE, Goldbohm RA, van den Brandt PA. Are coffee and tea consumption associated with urinary tract cancer risk? A systematic review and meta-analysis. Int J Epidemiol. 2001;30(2):353-362.
Source : American Botanical Council
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Drinking Green Tea With Starchy Food May Help Lower Blood Sugar Spikes
An ingredient in green tea that helps reduce blood sugar spikes in mice may lead to new diet strategies for people, according to Penn State food scientists.
Mice fed an antioxidant found in green tea -- epigallocatechin-3-gallate, or EGCG -- and corn starch had a significant reduction in increase in their blood sugar -- blood glucose -- levels compared to mice that were not fed the compound, according to Joshua Lambert, assistant professor of food science in agricultural sciences.
"The spike in blood glucose level is about 50 percent lower than the increase in the blood glucose level of mice that were not fed EGCG," Lambert said.
The dose of EGCG fed to the mice was equivalent to about one and a half cups of green tea for a human.
Lambert, who worked with Sarah C. Forester, postdoctoral fellow, and Yeyi Gu, graduate student, both in food science, said EGCG was most effective when the compound was fed to the mice simultaneously with corn starch. For humans, this may mean that green tea could help them control the typical blood sugar increases that are brought on when they eat starchy foods, like breads and bagels that are often a part of typical breakfasts.
"If what you are eating with your tea has starch in it then you might see that beneficial effect," Lambert said. "So, for example, if you have green tea with your bagel for breakfast, it may reduce the spike in blood glucose levels that you would normally get from that food."
The EGCG had no significant effect on blood sugar spikes in mice that were fed glucose or maltose, according to the researchers who released their findings in the online version of Molecular Nutrition and Food Research. Lambert said that the reason blood sugar spikes are reduced when the mice ate starch, but not these sugars, may be related to the way the body converts starch into sugar.
An enzyme called alpha-amylase that is produced in both the mouth and by the pancreas helps break down starch into maltose and glucose. EGCG may inhibit the enzymes ability to break down the starch, the researchers indicated, since they also found that EGCG reduced the activity of alpha amylase in the pancreas by 34 percent.
If the mechanism holds in humans, this may mean that people who want to limit the blood sugar spike should skip adding sugar to their cup of green tea.
"That may mean that if you add sugar into your green tea, that might negate the effect that the green tea will have on limiting the rise in blood glucose level," Lambert said.
Lambert added that the green tea and the starch would need to be consumed simultaneously. For example, drinking a cup of tea well after eating a piece of toast would probably not change the blood sugar spike.
For the study, researchers separated mice into several groups based on body weight. After a fasting period, the mice were given common corn starch, maltose, or sucrose. One group of mice received EGCG along with the feed, while a control group was not fed the compound.
The researchers then tested the blood sugar levels of both groups.
Lambert said the researchers next step is to test the compound on people.
"The relatively low effective dose of EGCG makes a compelling case for studies in human subjects," the researchers said.
Source : Science Daily
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Green Tea Could Modify the Effect of Cigarette Smoking On Lung Cancer Risk
Drinking green tea could modulate the effect of smoking on lung cancer.
Results of this hospital-based, randomized study conducted in Taiwan were presented at the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer, Jan. 11-14, 2010.
"Lung cancer is the leading cause of all cancer deaths in Taiwan," said I-Hsin Lin, M.S., a student at Chung Shan Medical University in Taiwan. "Tea, particularly green tea, has received a great deal of attention because tea polyphenols are strong antioxidants, and tea preparations have shown inhibitory activity against tumorigenesis."
However, previous studies of green tea have been inhibited by the flaws of the epidemiologic model with its inherent biases.
Lin and colleagues enrolled 170 patients with lung cancer and 340 healthy patients as controls. The researchers administered questionnaires to obtain demographic characteristics, cigarette smoking habits, green tea consumption, dietary intake of fruits and vegetables, cooking practices and family history of lung cancer. They also performed genotyping on insulin-like growth factors as polymorphisms on the following insulin-like growth factors: IGF1, IGF2 and IGFBP3, which have all been reported to be associated with cancer risk.
Among smokers and non-smokers, those who did not drink green tea had a 5.16-fold increased risk of lung cancer compared with those who drank at least one cup of green tea per day. Among smokers, those who did not drink green tea at all had a 12.71-fold increased risk of lung cancer compared with those who drank at least one cup of green tea per day.
Lin and colleagues suspect genetics may play a role in this risk differential. Green tea drinkers with non-susceptible IGF1 (CA)19/(CA)19 and (CA)19/X genotypes reported a 66 percent reduction in lung cancer risk as compared with green tea drinkers carrying the IGF1 X/X genotype.
Heavy smokers carrying susceptible IGF1, IGF2 and IGFBP3 genotypes also had a higher risk of lung cancer compared with nonsmokers carrying non-susceptible IGF1, IGF2 and IGFBP3 genotypes.
"Our study may represent a clue that in the case of lung cancer, smoking-induced carcinogenesis could be modulated by green tea consumption and the growth factor environment," said Lin.
Source : Science Daily
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Green Tea Found to Reduce Rate of Some GI Cancers
Women who drink green tea may lower their risk of developing some digestive system cancers, especially cancers of the stomach/esophagus and colorectum, according to a study led by researchers from Vanderbilt-Ingram Cancer Center.
The study by lead author Sarah Nechuta, Ph.D., MPH, assistant professor of Medicine, was published online in advance of the Nov. 1 edition of the American Journal of Clinical Nutrition. Wei Zheng, M.D., Ph.D., MPH, professor of Medicine, chief of the Division of Epidemiology and director of the Vanderbilt Epidemiology Center, was the principal investigator for the study.
To determine green tea's impact on cancer risk, the investigators surveyed women enrolled in the Shanghai Women's Health Study, a population-based study of approximately 75,000 middle-aged and older Chinese women. During the initial interview participants were asked if they drank tea, the type of tea consumed and how much they consumed. Most of the Chinese women reported drinking primarily green tea.
The researchers found that regular tea consumption, defined as tea consumption at least three times a week for more than six months, was associated with a 17 percent reduced risk of all digestive cancers combined. A further reduction in risk was found to be associated with an increased level of tea drinking. Specifically, those who consumed about two to three cups per day (at least 150 grams of tea per month) had a 21 percent reduced risk of digestive system cancers.
The trend toward fewer digestive cancers was strongest for stomach/esophageal and colorectal cancers.
"For all digestive system cancers combined, the risk was reduced by 27 percent among women who had been drinking tea regularly for at least 20 years," said Nechuta. "For colorectal cancer, risk was reduced by 29 percent among the long-term tea drinkers. These results suggest long-term cumulative exposure may be particularly important."
Tea contains polyphenols or natural chemicals that include catechins like EGCG and ECG. Catechins have antioxidant properties and may inhibit cancer by reducing DNA damage and blocking tumor cell growth and invasion.
The researchers also asked about other lifestyle factors including the kinds of food eaten regularly, exercise habits, education level and occupation. Women who had ever smoked or who drank alcohol were excluded from the study.
Regular tea drinkers in the study were younger, had higher education, exercised more and consumed more fruits and vegetables. While the researchers adjusted for these factors, they could not rule out an effect from these and other unmeasured lifestyle habits.
The study was conducted in nonsmoking and nondrinking Chinese women to minimize the potential influence of these two risk factors on the results for tea consumption and digestive system cancer risk.
Source : Science Daily
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Green Tea Reduced Inflammation, May Inhibit Prostate Cancer Tumor Growth, Research Finds
Men with prostate cancer who consumed green tea prior to undergoing prostatectomy had reductions in markers of inflammation, according to data presented at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, held in Anaheim, Calif., Oct. 16-19, 2012.
"Our study showed that drinking six cups of green tea affected biomarkers in prostate tissue at the time of surgery," said Susanne M. Henning, Ph.D., R.D., adjunct professor at the David Geffen School of Medicine at the University of California Los Angeles. "This research offers new insights into the mechanisms by which green tea consumption may reduce the risk for prostate cancer by opposing processes such as inflammation, which are associated with prostate cancer growth."
Prior epidemiological data have been inconclusive about the relationship between green tea and prostate cancer. However, one recent intervention study conducted in Italy revealed that men with a precursor to prostate cancer called prostatic intraepithelial neoplasia who consumed a green tea extract reduced their risk for progression to prostate cancer.
Henning and colleagues examined potential mechanisms by which green tea may have beneficial effects among 67 men with prostate cancer scheduled to undergo prostatectomy. The researchers randomly assigned the men to either six cups of brewed green tea or water daily for three to eight weeks, depending on the timing of their surgery. They collected blood and urine samples before and after the green tea or water consumption and collected prostate tissue following the pathology exam.
The data showed that serum prostate-specific antigen (PSA) concentrations were significantly lower at the end of the study compared with baseline levels in men consuming green tea. In addition, prostate tissue PSA protein expression was lower in men assigned to green tea consumption compared with the control group at the end of the study.
Further, immunostaining analysis revealed that nuclear factor kappa B, a marker of inflammation, was significantly reduced in those men assigned to green tea compared with those in the control group. A urinary marker of oxidative DNA damage was significantly decreased in urine from men consuming green tea compared with controls.
The researchers found no differences in markers of tumor cell proliferation between the two treatment groups.
Henning and her colleagues are further evaluating the association between green tea and prostate cancer by trying to enhance its activity. Currently, they are exploring the possibility of combining green tea with other natural products in mouse studies.
Source : Science Daily
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Mechanisms of Action for Green Tea Extract in Breast Cancer Prevention Identified
An oral green tea extract, Polyphenon E, appears to inhibit vascular endothelial growth factor and hepatocyte growth factor, both of which promote tumor cell growth, migration and invasion.
Researchers made this discovery during a secondary analysis of a phase Ib randomized, placebo-controlled study of Polyphenon E in a group of 40 women with hormone receptor-negative breast cancer. Katherine D. Crew, M.D., assistant professor of medicine and epidemiology at Columbia University Medical Center in New York, N.Y., presented the data at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, held in Anaheim, Calif., Oct. 16-19, 2012.
"Many preclinical studies have looked at epigallocatechin-3-gallate, or EGCG, which is one of the main components of green tea, and the various possible mechanisms of its action against cancer, but it is very difficult to do those same kinds of studies in humans," Crew said. "This study was too small to say for sure if green tea will prevent breast cancer, but it may move us forward in terms of understanding antitumor mechanisms."
In the primary analysis, presented at last year's Frontiers in Cancer Prevention Research meeting, 40 women were randomly assigned to 400 mg, 600 mg or 800 mg of Polyphenon E or to placebo twice daily for six months. During that time, researchers collected blood and urine samples from participants at baseline and at two, four and six months.
In this secondary analysis, Crew and colleagues used the blood and urine samples to examine biologic endpoints, such as inflammatory proteins, growth factors and lipid biomarkers, which might point to the mechanism of action behind green tea extract. Biomarker data were available for 34 of the 40 patients.
Women assigned to the extract had an average 10-fold increase in green tea metabolites compared with placebo. In addition, they had a significant reduction in hepatocyte growth factor levels at two months compared with women assigned to placebo. However, at the four-month and six-month follow-ups, the difference was no longer statistically significant.
The researchers also identified a trend toward decreased total serum cholesterol and decreased vascular endothelial growth factor in women assigned to the extract.
According to Crew, it is still too early to recommend green tea extract to prevent breast cancer. Currently, researchers are conducting several ongoing studies to explore the use of oral green tea extract in high-risk women for the primary prevention of breast cancer.
Source : Science Daily
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Brainy Beverage: Study Reveals How Green Tea Boosts Brain Cell Production to Aid Memory
It has long been believed that drinking green tea is good for the memory. Now researchers have discovered how the chemical properties of China's favorite drink affect the generation of brain cells, providing benefits for memory and spatial learning.
The research is published in Molecular Nutrition & Food Research.
"Green tea is a popular beverage across the world," said Professor Yun Bai from the Third Military Medical University, Chongqing, China. "There has been plenty of scientific attention on its use in helping prevent cardiovascular diseases, but now there is emerging evidence that its chemical properties may impact cellular mechanisms in the brain."
Professor Bai's team focused on the organic chemical EGCG, (epigallocatechin-3 gallate) a key property of green tea. While EGCG is a known anti-oxidant, the team believed it can also have a beneficial effect against age-related degenerative diseases.
"We proposed that EGCG can improve cognitive function by impacting the generation of neuron cells, a process known as neurogenesis," said Bai. "We focused our research on the hippocampus, the part of the brain which processes information from short-term to long-term memory."
The team found that EGCG boosts the production of neural progenitor cells, which like stem cells can adapt, or differentiate, into various types of cells. The team then used laboratory mice to discover if this increased cell production gave an advantage to memory or spatial learning.
"We ran tests on two groups of mice, one which had imbibed EGCG and a control group," said Bai. "First the mice were trained for three days to find a visible platform in their maze. Then they were trained for seven days to find a hidden platform."
The team found that the EGCG treated mice required less time to find the hidden platform. Overall the results revealed that EGCG enhances learning and memory by improving object recognition and spatial memory.
"We have shown that the organic chemical EGCG acts directly to increase the production of neural progenitor cells, both in glass tests and in mice," concluded Bai. "This helps us to understand the potential for EGCG, and green tea which contains it, to help combat degenerative diseases and memory loss."
- Yanyan Wang, Maoquan Li, Xueqing Xu, Min Song, Huansheng Tao, Yun Bai. Green tea epigallocatechin-3-gallate (EGCG) promotes neural progenitor cell proliferation and sonic hedgehog pathway activation during adult hippocampal neurogenesis. Molecular Nutrition & Food Research, 2012; 56 (8): 1292 DOI: 10.1002/mnfr.201200035
Source : Science Daily
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Green Tea Compound Shows Promise for Tackling Cancer
A compound found in green tea could be a weapon in treatments for tackling cancer, according to newly published research at the University of Strathclyde.
The extract, known as epigallocatechin gallate, has been known to have preventative anti-cancer properties but fails to reach tumours when delivered by conventional intravenous administration.
However, in initial laboratory tests at the Universities of Strathclyde and Glasgow, researchers used an approach which allowed the treatment to be delivered specifically to the tumours after intravenous administration. Nearly two-thirds of the tumours it was delivered to either shrank or disappeared within one month and the treatment displayed no side effects to normal tissues.
The tests are thought to be the first time that this type of treatment has made cancerous tumours shrink or vanish.
In the tests, on two different types of skin cancer, 40% of both types of tumour vanished, while 30% of one and 20% of another shrank. A further 10% of one of the types were stabilised.
The researchers encapsulated the green tea extract in vesicles that also carried transferrin, a plasma protein which transports iron through the blood. Receptors for transferrin are found in large amounts in many cancers.
Dr Christine Dufès, a senior lecturer at the Strathclyde Institute of Pharmacy and Biomedical Sciences, led the research. She said: "These are very encouraging results which we hope could pave the way for new and effective cancer treatments.
"When we used our method, the green tea extract reduced the size of many of the tumours every day, in some cases removing them altogether. By contrast, the extract had no effect at all when it was delivered by other means, as every one of these tumours continued to grow.
"This research could open doors to new treatments for what is still one of the biggest killer diseases in many countries."
Source : Science Daily via Antitumor activity of the tea polyphenol epigallocatechin-3-gallate encapsulated in targeted vesicles after intravenous administration. Nanomedicine, 2012; DOI: 10.2217/nnm.12.83
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The Effects of Green Tea Consumption on Cardiometabolic Alterations Induced by Experimental Diabetes
Patricia Fiorino,1 Fabiana Sant'Anna Evangelista,2 Fernando Santos,1 Fátima Maria Motter Magri,1 Jan Carlo Morais O. B. Delorenzi,1 Milton Ginoza,1 and Vera Farah1
1Renal, Cardiovascular and Metabolic Physiopharmacology Laboratory, Health and Biological Science Center, Mackenzie University, 01302-907 São Paulo, Brazil
2School of Arts, Science and Humanities, University of Sao Paulo, Sao Paulo, Brazil
We evaluated cardiac autonomic modulation by heart rate (HRV), and arterial pressure variability (APV), and metabolic response in streptozotocin diabetic rats treated with green tea. Male Wistar rats were separated in groups: control, drinking tap water (C), green tea-treated (GT) group, diabetic, drinking tap water (D), and diabetic, treated with green tea (DGT). Kidney mass was greater in D and DGT than in C and GT, but reduced in DGT compared to D. Green tea prevented the increase in creatinine clearance and reduced hyperglycemia in DGT compared to D. Arterial pressure was increased in GT and decreased in D compared to C. HRV was reduced in D compared with all groups. APV was decreased in D compared to C and recovery in DGT. Sympathetic modulation of APV was decreased in D compared with all groups. Green tea reduced hyperglycemia, prevented renal injury and autonomic dysfunction, suggesting reduced cardiovascular risk and target organ damage in diabetes.
Source: Experimental Diabetes Research Volume 2012 (2012), Article ID 309231, 7 pages doi:10.1155/2012/309231
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Green Tea Review Suggests Ability to Control Obesity and Diabetes among Many Other Health Benefits
Source : HerbalGram. 2010; American Botanical Council
Reviewed: Chacko SM, Thambi PT, Kuttan R, Nishigaki I. Beneficial effects of green tea: a literature review. Chinese Medicine. 2010;5:13-21.
Tea (Camellia sinensis, Theaceae), which is usually consumed as green (unfermented), black (fully fermented), or Oolong (partially fermented) tea, is associated with many health benefits. The most significant beneficial effects have been reported with the consumption of green tea.1 Among those health benefits are the risk reduction and prevention of several types of cancer and prevention of cardiovascular diseases, as well as anti-inflammatory, antiarthritic, antibacterial, antiangiogenic, antioxidative, antiviral, neuroprotective, and cholesterol-lowering effects. The authors of this article researched the available literature to highlight the efficacy, mechanisms of action, and adverse side effects of green tea and its constituent catechins.
Green tea is composed of proteins (15-20% dry weight), amino acids (1-4% dry weight), carbohydrates (5-7% dry weight), minerals and trace elements (5% dry weight), and trace amounts of lipids, sterols, vitamins, xanthic bases, pigments, and volatile compounds. The health benefits of green tea are attributed primarily to its polyphenol content. Most of the polyphenols are flavonols, commonly known as catechins (epicatechin, epigallocatechin, epicatechin-3-gallate, and (-)-epigallocatechin-3-gallate [EGCG]).
For this review, the authors searched PubMed, EMBASE, AMED, and China Academic Journals Full Text Database. They included articles about green tea’s health benefits in humans and animals, absorption of metal ions and drug-metabolizing enzymes, antioxidation and inhibition of oxidative stress, carbohydrate metabolism and diabetes mellitus, and adverse effects. The authors selected 105 peerreviewed articles in English for this review.
Cited in this review are animal studies reporting that green tea catechins provide some protection against degenerative diseases, that green tea has an antiproliferative activity on hepatoma cells and hyperlipidemic activity in hepatoma-treated rats, that green tea catechins could act as antitumorigenic agents and as immune modulators in immunodysfunction caused by transplanted tumors or by carcinogen treatment, and that green tea is effective in preventing oxidative stress and neurological problems.
Green tea has been linked to the prevention of certain types of cancer. The antioxidant, antimutagenic, and anticarcinogenic effects of green tea could offer protection against cancer caused by environmental agents. Green tea’s anticarcinogenic effects against breast cancer have been reported in experimental studies; however, according to the authors, epidemiologic evidence is inconsistent. Several epidemiological studies and clinical trials have shown that green tea may reduce the risk of chronic diseases, particularly hypertension and coronary heart disease. Other cited animal and human studies report an inhibitory effect of green tea on Helicobacter pylori infection and on the influenza virus, as well as an antifungal activity against Candida albicans.
Green tea consumption has also been associated with increased bone mineral density and protection against hip fractures.
The authors report that tea catechins can affect iron absorption, particularly in those at risk for iron deficiency. Noting that the catechins’ effects on other ions are not well understood, the authors suggest that they may affect absorption and metabolism of ions because flavonoids interact with various metal ions.
Green tea catechins, along with the antioxidant vitamins C and E and certain enzymes (e.g., superoxide dismutase and catalase), are hypothesized to contribute to the total antioxidant defense system. In vivo studies have reported that green tea catechins increase total plasma antioxidant activity. The content of the oxidative stress marker malondialdehyde has been shown to decrease after green tea intake. One cited study of 25 patients with different gastrointestinal complaints measured the tolerance of green tea tablets and their effect on antioxidant status indices; a decreased level of oxidative stress was seen in the treatment group.
Tea catechins, especially EGCG, appear to have antiobesity and antidiabetic effects. Recent data from human studies indicate that the consumption of green tea or green tea extracts may help reduce body weight, mainly body fat, by increasing postprandial thermogenesis and fat oxidation. One cited study of 6 overweight men given 300 mg EGCG daily for 2 days suggests that EGCG alone has the potential to increase fat oxidation in men and may thereby contribute to the antiobesity effects of green tea.
Cited studies in animal models of diabetes reported reductions in serum glucose levels with the administration of green tea polyphenols. In normal rats, green tea catechins reduced plasma triglyceride levels in an oral glucose-tolerance test. Green tea and green tea extracts have been demonstrated to modify glucose metabolism beneficially in experimental models of type 2 diabetes mellitus. A human study reported that green tea promoted glucose metabolism in healthy human volunteers as shown in oral glucose-tolerance tests.
The authors point out that the effects of green tea and its constituents may be beneficial up to a certain dose and may cause some as yet unrecognized adverse effects at higher doses (this is the authors’ conjecture; potentially adverse higher dose levels were not specified). Also, the effects of green tea catechins may vary from person to person. The harmful effects of too much tea are mainly due to its caffeine content, the possible presence of aluminum in some teas (which is problematic for patients with renal failure), and the effects of tea polyphenols on iron bioavailability.
The authors conclude that long-term consumption of tea catechins could be beneficial to high-fat diet-induced obesity and type 2 diabetes and could reduce the risk for coronary disease. Further research should focus on the pharmacological and clinical effects of green tea and its mechanisms of action.
1. Cabrera C, Artacho R, Gimenez R. Beneficial effects of green tea: a review. J Am Coll Nutr. 2006;25:79-99.
Source : Herbal Gram
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Green tea has been consumed for over 4,000 years, Chinese and Japanese cultures have long known the health benefits of this wonderful beverage and only recently has the western world taken heed with recent scientific studies beginning to establish the potential health benefits of drinking green tea.
The protective effects of green tea are due chiefly to catechins. Catechin is a tannin peculiar to green tea, it is a powerful, water soluble polyphenol and antioxidant that is easily oxidized. Tea contains four main catechin substances: EC, ECG, EGC and EGCG, all of which are inclusively called catechin. EGCG is the most powerful; as an antioxidant it is about 25-100 times more potent than vitamins C and E and one cup of green tea has antioxidant effects greater than a serving of broccoli, spinach, carrots, or strawberries. Catechin reacts with toxins created by harmful bacteria and also harmful metals such as lead, mercury, chrome, and cadmium.Scientists report in the Journal of Nutrition that regular consumption of green tea reduces the risk of breast cancer by approximately 12% compared with non green tea drinkers. Results from an animal study suggest that EGCG from green tea may stop the growth and spread of breast cancer cells by impacting on the tumour's blood vessels. A study of 69,710 Chinese women aged between 40 and 70 published in the journal Cancer Epidemiology Biomarkers & Prevention suggests that regular green tea consumption may reduce the risk of colon and rectal cancer in women by 50%. Also, on the subject of women and cancer: a study, published in the Annals of Epidemiology, found that drinking five or more cups of green tea a day may reduce a woman's risk of mouth cancer, however, men may not experience similar benefits, suggests the study from Japan.
Green tea catechins were found to be chemopreventive in a clinical trial involving men diagnosed with high-grade prostatic intraepithelial neoplasia (which often develops into prostate cancer within 1 year). After one year, in those who consumed tablets containing catechins (600 mg/day) there was a 3% incidence of prostate cancer, compared to 30% among men treated with a placebo.
Studies also show evidence that green tea provides immunoprotective qualities, particularly in the case of patients undergoing radiation or chemotherapy. White blood cell count, essential for fighting infection, appear to be maintained more effectively in patients consuming green tea compared to non-supplemented patients.
A study published in the Journal of Periodontology report that green tea promotes healthy gums and teeth. Researchers observed that for every one cup of green tea consumed per day, there was a decrease in periodontal disease in those subjects who regularly drank green tea. Periodontal disease is a chronic inflammatory disease that affects the gums and bone supporting the teeth, and has been associated with the progression of other diseases such as cardiovascular disease and diabetes.
Research from Greece reveal that regular consumption of green tea may improve the function of endothelial cells - cells lining the walls of blood vessels - and boost cardiovascular health. The study published in the European Journal of Cardiovascular Prevention and Rehabilitation concluded that consumption of green tea reduced cardiovascular disease and death.
Researchers report in Nutrition that daily supplements of green tea extract reduced both systolic and diastolic blood pressure and also LDL cholesterol (bad cholesterol) “Camellia sinensis compounds may be an option for people who have mild to moderate high BP, elevated LDL cholesterol, elevated markers of inflammation, or a combination of these three Cardiovascular risk factors,” wrote the researchers. “It may be helpful for individuals whose health care providers suggest a trial of diet and exercise before resorting to prescription medication,” they concluded.
A study in the journal Stroke, reported from pooled data from nine different studies that drinking three cups or more of tea (green or black tea) may reduce the risk of a stroke by 21%. Theanine (an amino acid found in tea) is almost 100% absorbed. "It gets across the blood-brain barrier and it looks a lot like a molecule that's very similar to glutamate, and glutamate release is associated with stroke. It could be that theanine and glutamate compete for the glutamate receptor in the brain," said lead author Lenore Arab.
The Journal of Neuroscience, report that EGCG may prevent Alzheimer’s-like damage in the brains of mice genetically programmed to develop the neurodegenerative disease process. EGCG decreases production of the Alzheimer’s-related protein, beta-amyloid, which can accumulate abnormally in the brain and lead to nerve damage and memory loss.
In The Journal of Nutrition a study recruited just over 100 adults aged between 21 and 65. The participants were all healthy and “normally sedentary”, During the study, the participants committed to 180 minutes of “moderate-intensity” physical activity per week, and to attend a minimum of three supervised exercise sessions per week. The participants drank either 500ml per day of a beverage providing 625mg catechins, or a control beverage containing added caffeine to match the caffeine content of the catechin beverage. At the end of the study period, people in the catechin group had lost more body weight compared to the control group. And so it was suggested that antioxidant compounds in green tea could help promote exercise-induced abdominal fat loss