Green teaeht tuobA aeT fo etutitsnI no

Green tea is widely consumed in Asia and is regarded as a health-promoting ssenerawa etombeverage. orp ot si noiThe ssimbeneficial s’aeT fo etueffects titsnI notpiL ehT of green tea are generally attributed to its polyphenol hcraeser ruO .puc ot hsub morf aet fo gnidnatsrednu dna content, particularly catechins. The aim of this factsheet .stfieneb htlaeh sti dna seitreporp sti ,edam si aet woh no sesucof is to provide an overview on the health benefits of fo stsisnoc etutitsnI eht ,KU ,koorbnrahS ni sretrauqdaeh htiW green tea. ni detacol sertnec hcraeser morf strepxe cfiitneics lanoitanretni egareveb yek ni dna ,ayneK & aidnI ,snoiger gniworg aet rojam anihC dna napaJ ,SU – stekram

Green tea: What is it? a) Green tea processing and composition Green tea, as black, oolong and white tea, is produced from the plant Camellia Sinensis. The difference between these teas lies in the way the tea leaves are processed after harvest. The major step in tea production is to stop the oxidation process at a predetermined stage, depending on the type of tea being aimed for (Figure 1). This process determines the quantity and type of flavonoids present in the tea, catechins being the main flavonoids produced by the Camellia Sinensis plant. During the oxidation process, enzymatic activity allows the catechins to be polymerised.

• As Green tea leaves are heated soon

after harvesting, the enzymatic activity is stopped in order to retain the majority of catechin flavonoids and its green colour.

• Black tea undergoes substantial oxidation, 

which results in the polymerisation of catechins into theaflavins and the arubigins flavonoids.

• Oolong tea is a result of oxidation being

stopped somewhere in between that of green and black tea and therefore contains flavonoids that are found in both green and black teas (Graham, 1992).

Figure 2. The type of flavonoids found in green vs black tea (compiled by the Lipton Institute of Tea)

Figure 1. Tea processing

ea processing

Catechins

Green Tea (% weight of extract solids) 30-42

Flavonols

5-10

Other flavonoids

2-4

Theogallin

2-3

Other depsides

1

Ascorbic Acid

1-2

Gallic Acid

0.5

Quinic acid

2

Other organic acids

4-5

Theanine

4-6

Other amino acids

4-6

Methylxanthines

7-9

Carbohydrates

10-15

Minerals

6-8

Volatiles

0.02

Table 1: Green tea composition (Graham et al, 1992)

Processing of the leaves, geographical location, growing conditions, type of green tea and preparation of infusion affect the amount of catechins in green tea (Cabrera, 2006). b) Green tea consumption Approximately 76-78% of the tea produced and consumed globally is black tea, 20-22% is green tea and less that 2% is oolong tea. Black tea is consumed principally in Europe, North America and North Africa while green tea is widely drunk in China, Japan, Korea, and Morocco. Oolong tea is popular in China and Taiwan (Cabrera, 2006).

1

Green tea catechins Green tea is widely considered as a healthpromoting beverage, and the beneficial effects generally associated with green tea have been attributed to its polyphenol content, particularly to catechins and their antioxidant activity. Catechins are a group of very active flavonoids that include epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC) and epigallocatechin gallate (EGCG), the latter being the most abundant. Catechins are colourless, water-soluble compounds that contribute to the bitterness and astringency of green tea. A typical green tea serving contains approximately 90mg catechins (Balentine et al, 1997). Other sources of catechins include apples, grapes, wine and cocoa. Tea catechins have been shown to be bioavailable in humans, with EGCG showing lower bioavailability than EGC and EC (Lee et al, 2002). Only a small percentage of the ingested catechins appear in the blood. In a study by Lee et al (2002), at the time point tmax (the time to reach maximum concentration), 0.16, 0.58, and 1.1% of the ingested doses of EGCG, EGC and EC from green tea administration were present in the

circulating plasma. According to different studies on catechin pharmacokinetics, EGCG are mostly present in the free form in the plasma, whereas EGC and EC are predominantly found as glucuronic acid and sulphate conjugates in plasma and urine. There is evidence that EGCG is only present in trace or non-detectable amounts in the urine and is excreted into bile (Lee et al, 2002; Chow et al, 2001; Williamson et al, 2005).

Possible mechanism of action Green tea extracts and catechins are known to have strong antioxidant properties in vitro (Higdon and Frei, 2003). In these in vitro tests catechins are able to protect biological molecules e.g. endogenous antioxidants, lipids, and proteins, against the adverse effects of reactive oxygen and reactive nitrogen species (Cherubini et al, 1999; Leung et al, 2001; Zhu et al, 1999). Moreover, there is consistent evidence that green tea consumption produces a significant increase in the overall plasma antioxidant capacity in humans (Serafini et al, 1996; Van Het Hof et al, 1997; Benzie et al, 1999; Leenen et al, 2000; Serafini et al, 2000; Sung et al, 2000; Hodgson et al, 2000). It is however not clear whether this effect is mediated by the sole action of tea flavonoids as these compounds are poorly bioavailable and extensively metabolised during absorption (Halliwell et al, 2005). Furthermore, the physiological relevance of increased plasma antioxidant capacity still needs to be determined. Direct evidence for a beneficial role of green tea consumption in reducing oxidative damage in humans can only be established in human intervention studies using validated biomarkers. The evidence for in vivo

antioxidant effects of tea and its flavonoids is however so far confusing and equivocal (Halliwell et al, 2005; Lolito and Frei 2006). The antioxidant activity of tea flavonoids is often suggested as a mechanism of action for the health benefits associated with tea drinking. However a scientific consensus is now emerging that health benefits associated with tea drinking are not simply related to a general antioxidant protection due to the presence of flavonoids. Instead, tea flavonoids, even at the low levels found in plasma, may exert health benefits through other mechanisms such as modulation of cell signalling pathways or gene regulation, to influence biologically relevant end points (Williams et al, 2004). For example, there are now studies being performed which suggest that epicatechins are metabolised by catecholO-methyltransferase (COMT) and that these metabolites might have the potential to inhibit endothelial NADPH oxidase, consequently decreasing the loss of NO (Nitric Oxide). NO is a key endothelium-derived relaxing factor that plays a pivotal role in the maintenance of vascular tone and reactivity (Schewe et al, 2008). Other studies suggest that flavonoids are able to induce NO-synthase (Schroeter et al, 2006). These new research areas are now being explored.

Green tea and body weight/ body composition

In a context of increased incidence of obesity, green tea is thought to exert a beneficial impact on body composition and weight management. Being calorie-free, green tea consumed without sugar can be successfully incorporated into a weight control programme. Moreover, there is some evidence for a link between green tea catechin consumption and weight control or body shape. A number of human studies, mostly conducted in Asian populations, have shown a decrease in body weight and visceral fat after longterm consumption (usually 12 weeks) of high catechin green tea (400-900mg catechins) (Chantre et al, 2002; Hase et al, 2001; Nagao et al, 2001;2005; Tsuchida et al, 2002; Kajimoto et al, 2005; Kataoka et al, 2004). While a few studies did not find any effects of catechins on weight control, background caffeine intake seems to affect

the effectiveness of green tea and it is possible that green tea/catechins may be more effective in low to moderate caffeine users (Kovacs et al, 2004; Diepvens et al, 2005; Maron et al, 2003). In these studies, the effects of high catechin green tea on visceral fat have been observed more often than effects on body weight, suggesting that catechins have an effect on body composition and fat distribution rather than on body weight.

Green and oolong tea have also shown promising short-term effects on energy expenditure and fat oxidation (Dulloo et al, 1999; Rumpler et al, 2001; Bérubé-Patent et al, 2005) although it is not clear whether this effect is due to caffeine, catechins or both. Furthermore, acute and long-term studies have shown that catechin ingestion can increase fat oxidation during exercise (Venables et al, 2008; Ota et al, 2005; Takashima et al, 2004). This increase in fat oxidation could explain (partly) the beneficial long-term effect of high catechin green tea on body composition.

In addition to its calorie-free property, green tea can have a beneficial effect on body composition through its catechins.

Green tea and chronic diseases The antioxidant activity of tea flavonoids has been suggested as a mechanism of action for the health benefits associated with tea drinking, and has led considerable interest in the potential health benefits of green tea consumption against chronic diseases: Cardiovascular health Many epidemiological studies have investigated the association between green tea consumption and cardiovascular events as well as other surrogate markers of cardiovascular disease. Most of them have been conducted among Asian populations and suggest a cardioprotective effect of green tea consumption (Wolfram 2007; Stangl, 2006; Khan and Mukhtar, 2007). The mechanisms for these observations however remain uncertain. Several studies, mainly in vitro and animal models, have looked into potential mechanisms including: Anti-hypertensive effect: Results from epidemiological and human clinical studies on green tea consumption and blood pressure are not yet consistent (Cabrera 2006; Stangl, 2006; Cheng, 2006). Prevention of LDL oxidation: In contrast to the clear effects of tea flavonoids against LDL oxidation in vitro, the effects of green tea consumption on LDL oxidation in animal and human studies are more controversial (Stangl et al, 2006).

Anti-inflammatory /anti-thrombotic/ antiproliferative effects: Many animal and in vitro studies report promising anti-inflammatory, anti-thrombotic and antiproliferative effects of catechins (Stangl et al, 2006). To date, there is limited support for anti-inflammatory effects in randomised trials (Hodgson, 2008). For example, one human trial found that daily drinking for four weeks of green tea reduced plasma levels of soluble P-selectin, an endothelial adhesion molecule implicated in the process of atherogenesis (Lee et al, 2005). Lipid lowering effect: Despite the favourable results from animal experiments, results of human studies regarding the effects of green tea on plasma lipids are not uniform (Van het hof 1997, Tsubono 1997; Unno et al, 2005). The lipid lowering effects of tea in humans are for the most part, moderate. The discrepancies between experimental and clinical data may

be explained by the fact that most animal studies were performed with high doses of tea and tea components (Stangl, 2006). Improved endothelial function: Normal endothelial function regulates vasomotor tone, platelet activity, leukocyte adhesion and vascular smooth muscle cell proliferation via a release of several paracrine factors including NO. Experimental studies have demonstrated flavonoids to enhance the synthesis and release of endothelial derived NO. Also,

there is good evidence from human intervention trials that green tea consumption can improve endothelial function as assessed by flow-mediated dilation. This has been observed in four human trials, in healthy and diabetic subjects, after acute and chronic tea consumption (Alexopoulos et al, 2008; Nagaya et al, 2004; Kim et al, 2006; Jochmann et al, 2007). A recent study by Widlansky et al (2007) also showed that acute EGCG supplementation improves endothelial function in humans with coronary artery disease.

Cancer The role of green tea in cancer prevention has been hypothesised from a large number of studies in cell culture and animal models carried out over more than a decade, and mostly showing cancer preventive effects of green tea and catechins (Yang et al, 2007). Green tea has been shown to inhibit tumorigenesis in many animal models, including those for cancer of the skin, lung, oral cavity, oesophagus, stomach, small intestine, colon, liver, pancreas, bladder, and prostate (Cabrera et al, 2006). A large number of epidemiological studies have also investigated the association between green tea consumption and different types of cancer. The results of these studies are however inconsistent (Yang et al, 2007; FDA, 2005). This discrepancy between experimental and epidemiological studies may arise from several factors. Human population are not homogeneous in genetic background and lifestyle, and results are influenced by many confounding factors whereas experimental conditions are well controlled in animal studies. Cell culture or animal studies also usually use concentrations of tea compounds far exceeding those found in the human plasma. Moreover, free flavonoids are often used in cell culture studies while dietary flavonoids are extensively altered during first-pass metabolism (Lambert et al, 2003; Kroon et al, 2004). The most relevant data that would support a protective effect of green tea on cancer are human intervention trials. So far, the few human trials that have investigated the effects of green tea extracts and cancer are small and with conflicting results regarding the clinical benefits (Shanafelt et al, 2006; Choan et al, 2005; Laurie et al, 2005; Jatoi et al, 2003; Bettuzzi et al, 2006). Thus, despite promising work from experimental studies, the evidence is so far too contradictory to suggest a benefit of green tea on cancer prevention.

Neurodegenerative diseases Green tea consumption has been proposed to protect against Parkinson’s disease and Alzheimer’s disease. This hypothesis is based on studies carried out in animal models and cell cultures, in which green tea polyphenols have demonstrated neuroprotectant activity (Pan et al, 2003; Weinreb et al, 2004). However, evidence from human studies is so far lacking and epidemiological data are scarce and contradictory regarding the association between green tea consumption and Parkinson’s disease or Alzheimer’s disease risk (Checkoway et al, 2002; Tan et al, 2003; Tan et al, 2008; Weinreb et al, 2004).

Diabetes Epidemiological studies have suggested that green tea consumption is associated with a decreased risk of diabetes (Iso et al, 2006; Song et al, 2005) and a reduced level of fasting blood glucose in non-obese people (Polychronopoulos et al, 2008). Animal studies have also shown evidence for an improvement in glucose tolerance and insulin sensitivity with green tea extract consumption (Wu et al, 2004; Cabrera, 2006). Results from the few clinical studies conducted so far on this topic are more controversial (Mackenzie et al, 2007; Tsuneki et al, 2004; Fukino et al, 2005, 2007; Hase et al, 2001; Ryu et al, 2006) and further human studies are needed before drawing any conclusion on the effects of green tea and its ingredients on blood glucose control.

Epidemiological studies suggest a cardioprotective effect of green tea consumption, which might be explained by an improved endothelial function with green tea consumption. Evidence for a preventive effect of green tea against cancer, neurodegenerative disease or diabetes is so far too conflicting.

Green tea antibacterial activity Green tea flavonoids have well-established in vitro antibacterial, antimicrobial, antiviral, antifungal activities against a variety of infectious agents, e.g. Staphylococcus aureus, Vibrio cholerae, Escherichia coli, Helicobacter pylori, Legionella pneumophila, influenza virus, HIV type 1, Herpes simplex virus (Friedman, 2007; Song and Seong 2007; Hamilton-Miller, 1995). These studies have been conducted in vitro, sometimes in animal models, but they do not demonstrate bacteria or virus inhibition by tea in humans. A few human studies have investigated the antibacterial and antiviral effects of tea: three studies by Yamada et al (2003; 2006a; 2006b) found in elderly patients that catechins reduced the incidence of influenza infection and lowered MethicillinResistant Staphylococcus Aureus concentration in sputum. Moreover, Yee and colleagues (2002) investigated the relationship between Chinese tea consumption and Helicobacter pylori infection in 72 patients undergoing their first upper endoscopy. They found tea consumption to be inversely associated to Helicobacter pylori infection. These early investigations are promising for green tea’s role against infectious agents.

Oral health Earlier epidemiological studies reported that populations who drink tea on a regular basis have a reduced number of carious teeth (Ramsey et al, 1975; Onisi, 1981; 1985; Jones et al, 1999- Hamilton-Miller, 2001). In vivo animal studies have also provided evidence that green tea polyphenols can reduce dental caries (Otake et al, 1991). In a few human trials, tea (oolong and green) and catechins (without added sugar) have been shown to inhibit plaque deposition (Ooshima et al, 1994), reduce plaque and gingival index (Liu and Chi, 2000; You, 1993) and inhibit acid production in dental plaque bacteria (Hirasawa et al, 2006). Green tea is a rich natural source of fluoride in the diet (Wei, 1989), providing for example in the UK 85% of total fluoride intake (FSA 1997). Fluoride may have a beneficial effect on dental health (NHS CRD, 2000). However, it is suggested that tea polyphenols, including green tea flavonoids, rather than fluoride are responsible for the noted effects on oral health (Wu et al, 2002). Several mechanisms have been proposed for the observed anticariogenic properties of tea and its polyphenols, including inhibitory effect

on bacterial growth and bacterial viability, inhibition of glucosyl transferase which limits the biosynthesis of sticky glucan (glucan synthesis allows the bacteria to firmly attach to the tooth surface), and inhibition of salivary α-amylase activities and the consequent inhibition of starch hydrolysis (Wu et al, 2002). Moreover, tea components have been shown to increase acid resistance to tooth enamel (Yu et al, 1995). Also, it has been shown that green tea was very effective in reducing oral malodour temporarily because of its disinfectant and deodorant activities (Lodhia et al, 2008). Larger well-controlled clinical trials are required to confirm the promising benefits of green tea on oral health and against infectious agents in humans.

Larger well-controlled clinical trials are required to confirm the promising benefits of green tea on oral health and against infectious agents in humans.

Green tea and skin A number of animal studies have shown that topical treatment or oral consumption of green tea can protect skin against UV radiation damage (Katiyar, 2003; Yusuf et al, 2007). Moreover, there is some evidence that catechins might have photoprotective effects against UV-induced erythema (sunburn) and also might improve skin condition in women (Heinrich et al 2006). However, there is only limited evidence that has shown a direct effect of drinking green tea: A randomised controlled trial from Chiu et al (2005) found histologic improvement in elastic tissue content, but no effect on photoaging after a combination of topical cream and oral green tea supplementation for eight weeks compared to placebo. In a small study Morley et al (2005) found that 540ml green tea consumption can offer a photoprotective effect: samples of peripheral blood cells taken after green tea consumption

showed lower levels of DNA damage than those taken prior to ingestion when exposed to 12 minutes of ultraviolet A (UVA) radiation. Moreover, there is growing evidence that flavanol-rich cocoa chronically and acutely increases microcirculation in human skin (Heinrich et al, 2006; Neukam et al, 2007). In both studies, the major flavanol monomers in the drinks were epicatechin or catechins, flavonoids that are also present in green

tea. In the first study (Heinrich et al, 2006), in addition to improved dermal blood circulation, flavanols had a photoprotective effect - reducing UV-induced erythema - and increased skin thickness and hydration after 12 weeks consumption. In the second study (Neukam et al, 2007), flavanol-rich cocoa consumption acutely increased dermal blood flow and oxygen saturation.

There is not enough evidence yet to link green tea consumption and skin protection. Research on flavanols and microcirculation however seems to be a promising area for future investigations.

Green tea and hydration Tea is the most consumed beverage in the world after water and a cup of tea is 99.5% water. Thus, tea contributes significantly to daily fluid requirements and body’s hydration status. A guidance system for beverage consumption has been published in the American Journal of Clinical Nutrition (Popkin et al, 2006) to provide consumers with an easy guide to select healthier beverages, based on their energy density, nutrient density and health benefits. These guidelines rank tea as second to water as an ideal beverage choice for hydration. The authors recommend

consumption of up to eight cups of tea (green or black) per day, caffeine being the limiting factor. Tea drinking thus contributes to fluid intake and can be an important source of fluid especially in certain groups, such as the elderly (National Drinks Survey UK, 2003). Hydration is fundamental to a number of vital roles, such as removal of waste products from the body, and to physical and mental performances - concentration, alertness, memory, speed and sports performance.

Tea is second only to water as an ideal beverage choice for hydration and significantly contributes to body’s hydration.

Conclusion Green tea has been consumed for centuries for its health properties that are generally attributed to its catechin content. Green tea is a hydrating calorie-free beverage whose consumption is recommended up to eight cups per day. While research on green tea is very promising in certain areas such as cardiovascular health, body weight control, oral health and skin, future studies are needed to fully understand its contribution to some other benefits like cancer or neurodegenerative diseases prevention.

References Alexopoulos N Vlachopoulos C, Aznaouridis K, Baou K, Vasiliadou C, Pietri P, Xaplanteris P, Stefanadi E, Stefanadis C. The acute effect of green tea consumption on endothelial function in healthy individuals. Eur J Cardiovasc Prev Rehabil. 2008 Jun;15(3):300-5 Astill C, Birch MR, Dacombe C, Humphrey PG, Martin PT. Factors Affecting the Caffeine and Polyphenol Contents of Black and Green Tea Infusions. J. Agric. Food Chem. 2001, 49, 5340-5347 Astley SB, Lindsay DG. European Research on the Functional Effects of Dietary Antioxidants (EUROFEDA). Conclusions. Mol Aspects Med. 2002; 23: 287-291. Balentine DA, Wiseman SA, Bouwens LC. The chemistry of tea flavonoids. Crit Rev Food Sci Nutr 1997, 37, 693-704. Benzie IFF, Szeto YT, Strain JJ, Tomlinson B. Consumption of green tea causes rapid increase in plasma antioxidant power in humans. Nutrition and Cancer- An International Journal 1999;34(1):83-87. Bérubé-Parent S, Pelletier C, Dore J, Tremblay A. Effects of encapsulated green tea and Guarana extracts containing a mixture of epigallocatechin-3- gallate and caffeine on 24 h energy expenditure and fat oxidation in men. Br J Nutr 2005;94:432-436. Bettuzzi S et al. Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from one-year proof-of-principle study. Cancer Res 2006, 15, 66(2), 1234-40 Bors, W.; Michel, C.; Stettmaier, K. Structure–activity relationships governing antioxidant capacities of plant polyphenols. Methods Enzymol.335:166–180; 2001. Cabrera C, Artacho R, Gimenez R. Beneficial effects of green tea- a review. Journal of American college of nutrition, 25, 2, 79-99, 2006. Chantre P, Lairon D. Recent findings of green tea extract AR25 (Exolise) and its activity for the treatment of obesity. Phytomedicine 2002;9:3-8. Checkoway H, Powers K, Smith-Weller T, Franklin GM, Longstreth WT Jr, Swanson PD. Parkinson’s disease risks associated with cigarette smoking, alcohol consumption, and caffeine intake. Am J Epidemiol 2002;155:732–8. Cheng TO. All teas are not created equal. The Chinese green tea and cardiovascular health. International Journal of cardiology 108 (2006) 301-308. Cherubini A, Beal MF, Frei B. Black tea increases the resistance of human plasma to lipid peroxidation in vitro, but not ex vivo. Free Radical Biology and Medicine 1999;27(3-4):381-387. Chiu AE, Chan JL, Kern DG, Kohler S, Rehmus WE, Kimball AB. Double-blinded, placebo-controlled trial of green tea extracts in the clinical and histologic appearance of photoaging skin. Dermatol Surg. 2005 Jul;31(7 Pt 2):855-60; discussion 860 Choan E et al. A prospective clinical trial of green tea for hormone refractory prostate cancer: and evaluation of the com-

plementary/alternative therapy approach. Urol Oncol 2005, 23(2), 108-13. Chow HHS, Cai Y, Alberts DS, Hakim I, Dorr R, Shahi F, Crowell JA, Yang CS, Hara Y (2001). Phase I pharmocokinetics study of tea polyphenols following single-dose administration of epigallocatechin gallate and polyphenon E. Cancer Diepvens K, Kovacs EM, Nijs IM, Vogels N, Westerterp-Plantenga MS. Effect of green tea on resting energy expenditure and substrate oxidation during weight loss in overweight females. Br J Nutr. 2005 Dec;94(6):1026-34. Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J. 1999. Efficacy of a green tea extract rich in catechinpolyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr 70: 1040-5 Friedman M. Overview of antibacterial, antitoxin, antiviral, and antifungal activities of tea flavonoids and teas. Mol Nutr Food Res 2007, 51, 116-134. Food Standard Agency (2001). Committee on Toxicity of Chemicals in Food, Consumer. Fukino Y, Ikeda A, Maruyama K, Aoki N, Okubo T, Iso H. Randomized controlled trial for an effect of green tea-extract powder supplementation on glucose abnormalities. Eur J Clin Nutr. 2007 Jun 6. [Epub ahead of print] Fukino Y, Shimbo M, Aoki N, Okubo T, Iso H. Randomized controlled trial for an effect of green tea consumption on insulin resistance and inflammation markers. J Nutr Sci Vitaminol (Tokyo). 2005 Oct;51(5):335-42 Gomez-Ramirez A et al. Effects of L-theanine on the Deployment of Intersensory Selective Attention; A High-density Electrical Mapping Study. Accepted for Publication, Neuropharmacology 2006 Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med. 1992 May;21(3):334-50. Halliwell B, Rafter J, Jenner A. Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not? Am J Clin Nutr. 2005; 81: 268S-276S. Halliwell B. Oxidative stress, nutrition and health. Experimental strategies for optimization of nutritional antioxidant intake in humans. Free Radical Research 1996;25(1):57-74. Hamilton-Miller JMT. Anti-cariogenic properties of tea (Camellia Sinensis). J Med Microbiol 2001, 50, 299-302. Hamilton-Miller JMT. Antimicrobial properties of tea. Antimicrobial agents and chemotherapy 1995, 2375-2377. Hase TK, Mguro S, Takeda Y, Takahashi H. Anti-obesity effects of tea catechins in humans. J Oleo Sci 50, 599-605, 2001 Heinrich U, Neukam K, Tronnier H, Sies H, Stahl W. Long-term ingestion of high flavanol cocoa provides photoprotection against UV-induced erythema and improves skin condition in women. J Nutr. 2006 Jun;136(6):1565-9 Higdon JV, Frei B. Tea Catechins and Polyphenols: Health Ef-

fects, Metabolism, and Antioxidant Functions. Critical Reviews in Food Science and Nutrition, 43(1):89–143 (2003) Hirasawa M, Takada K, Otake S. Inhibition of acid production in dental plaque bacteria by green tea catechins. Caries Res. 2006;40(3):265-70 Hodgson JM. Tea flavonoids and cardiovascular disease. Asia Pac J Clin Nutr 2008, 17, 288-290 Hodgson JM, Puddey IB, Croft KD, Burke V, Mori TA, Caccetta RA, Beilin LJ. Acute effects of ingestion of black and green tea on lipoprotein oxidation. American Journal of Clinical Nutrition 2000;71(5):1103-1107. Iso H Date C, Wakai K, Fukui M, Tamakoshi A; JACC Study Group.The relationship between green tea and total caffeine intake and risk for self-reported type 2 diabetes among Japanese adults. Ann Intern Med. 2006 Apr 18;144(8):554-62 Jatoi A et al. A phase II trial of green tea in the treatment of patients with androgen independent metastatic propstate carcinoma. Cancer 2003, 15, 97(6), 1442-6. Jochmann N, Lorenz M, von Krosigk A, Martus P, Böhm V et al. The efficacy of black tea in ameliorating endothelial function is equivalent to that of green tea. British Journal of Nutrition, 2007 Jones C, Woods K, Whittle G, Worthington H, Taylor G Sugar, drinks, deprivation and dental caries in 14-year-old children in the north west of England in 1995. Community Dent Health. 1999 Jun;16(2):68-71. Juneja LR et al. L-theanine, A Unique Amino Acid of Green Tea and its Relaxation Effects in Humans. Trends Food Sci Tech 1999 10:199- 204 Kajimoto O, Kajimoto Y, Yabune M, Nakamura T, Kotani K, Suzuki Y, Nozawa A, Nagata K, Unno T, Sagesaka YM, Kakuda T, Yoshikawa T. Tea Catechins with a galloyl moiety reduce body weight and fat. J Health Sci 2005;1:161-171. Kataoka K, Takashima S, Shibata E , Hoshino E. Body fat reduction by the long term intake of catechins and the effects of physical activity. Prog Med 2004, 24, 3358-3370 Katiyar SK. Skin photoprotection by green tea: antioxidant and immunomodulatory effects. Curr Drug Targets Immune Endocr Metabol Disdord 2003, 3(3), 234-42 Khan N, Mukhtar H. Tea polyphenols for health promotion. Life sciences 81 (2007) 519-533. Kim W, Jeong MH, Cho SH, Yun JH, Chae HJ, Ahn YK, Lee MC, Cheng X, Kondo T, Murohara T, Kang JC. Effect of green tea consumption on endothelial function and circulating endothelial progenitor cells in chronic smokers. Circ. J. 2006; 70: 10521057. Kovacs EMR, Lejeune MPGM, Nijs I, Westerterp-Plantenga MS. Effects of green tea on weight maintenance after body-weight loss. Br J Nutr 2004;91(3):431-437. Kroon PA, Clifford MN, Crozier A, Day AJ, Donovan JL, Manach C, Williamson G (2004). How should we assess the effects of exposure to dietary polyphenols in vitro? Am J Clin Nutr, 80, 15-21. Lambert JD, Yang CS. Cancer chemopreentive activity and bioavailability of tea and tea polyphenols. Mutation research 2003, 523-524, 201-208 Laurie SA et al. Phase I study of green tea extract in patients with advanced lung cancer. Cancer chemother Pharmacol 2005, 55(1), 33-8 Lee W, Min WK, Chun S, Lee YW, Park H, Lee DH, Lee YK, Son JE. Long-term effects of green tea ingestion on atherosclerotic biological markers in smokers. Clin Biochem. 2005 Jan;38(1):84-7 Lee MJ, Malialal P. Chen L, Meng X, Bondoc FY, Prabhu S, Lambert G, Mohr S, Yang CS (2002). Pharmacokinetics of tea catechins after ingestion of green tea and epigallocatechin-3-gallate by humans: Formation of different metabolites and individual variability. Cancer epidemiology, Biomarkers and Prevention, 11, 1025-1032. Leenen R, Roodenburg AJC, Tijburg LBM, Wiseman SA. A single dose of tea with or without milk increases plasma antioxidant activity in humans. European Journal of Clinical Nutrition 2000;54(1):87-92. Liu T, Chi Y. Experimental study on polyphenol anti-plaque effect in human. Zhonghua Kou Qiang Yi Xue Za Zhi. 2000 Sep;35(5):383-4 Lodhia P; Yaegaki K, Khakbazhejad A, Imai T, Sato T, Tanaka T, Murata T, Kamada T. Effect of green tea on volatil sulfur compounds in mouth air. J Nutr Sci Vitaminol, 2008, 84, 89-94. Lolito SB, Frei B. Consumption of flavonoid-rich foods and increased plasma antioxidant capacity in humans: cause, consequence, or epiphenomenon? Free Radic Biol Med. 2006 Dec 15;41(12):1727-46. Epub 2006 Jun 3. Review. Leung LK, Su YL, Chen RY, Zhang ZH, Huang Y, Chen ZY. Thea-

flavins in black tea and catechins in green tea are equally effective antioxidants. Journal of Nutrition 2001;131(9):2248-2251. Mackenzie T, Leary L, Brooks WB. The effect of an extract of green and black tea on glucose control in adults with type 2 diabetes mellitus: double-blind randomized study. Metabolism. 2007 Oct;56(10):1340-4 Maron DJ, Lu GP, Cai NS, Wu ZG, Li YH, Chen H, Zhu JQ, Jin XJ, Wouters BC, Zhao J. Cholesterol-lowering effect of a theaflavinenriched green tea extract: a randomized controlled trial. Arch Intern Med 2003;163:1448-1453. Maughan and Griffin (2003). Caffeine ingestion and fluid balance: a review. J Hum Nutr Dietet, 16, 411-420. Morley N, Clifford T, Salter L, Campbell S, Gould D, Curnow A. The green tea polyphenol (-)-epigallocatechin gallate and green tea can protect human cellular DNA from ultraviolet and visible radiation-induced damage. Photodermatol Photoimmunol Photomed. 2005 Feb;21(1):15-22 Nagao T, Komine Y, Soga S, Meguro S, Hase T, Tanaka Y, Tokimitsu I. Ingestion of a tea rich in catechins leads to a reduction in body fat and malondialdehydemodifiedLDL in men. Am J Clin Nutr 2005;81:122-129. Nagao T, Meguro S, Soga S, Otsuka A, Tomonobu K, Fumoto S, Chikama A, Mori K, Yuzawa M, Watanabe H, Hase T, Tanaka H, Tokimitsu I, Shimasaki H, Itakura H. Tea catechins suppress accumulation of body fat in humans. J Oleo Sci 2001;50:717-728. Nagaya N, Yamamoto H, Uematsu M, Itoh T, Nakagawa K, Miyazawa T, Kangawa K, Miyatake K. Green tea reverses endothelial dysfunction in healthy smokers. Heart 2004; 90: 14851486 Neukam K, Stahl W, Tronnier H, Sies H, Heinrich U. Consumption of flavanol-rich cocoa acutely increases microcirculation in human skin. Eur J Nutr. 2007 Feb;46(1):53-6. Epub 2006 Dec 11 NHS CRD (2000). A systematic Review of PublicWater Fluoridation (CRD Report No 18). NHS Centre for Review and Dissemination, University of York: York, UK. Nobre AC , Rao AR, Owen GN. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr 2008, 17, 167-168. Ooshima T, Minami T, Aono W, Tamura Y, Hamada S. Reduction of dental plaque deposition in humans by oolong tea extract. Caries Res. 1994;28(3):146-9 Ota N, Soga S, Shimotoyodome A, Haramizu S, Inaba M, Murase T, Tokimitsu I. Effects of combination of regular exercise and tea catechins intake on energy expenditure in humans. Journal of health science 2005, 51(2), 233-236 Otake S, Makimura M, Kuroki T, Nishihara Y, Hirasawa M Anticaries effects of polyphenolic compounds from Japanese green tea. Caries Res. 1991;25(6):438-43 Pan T, Jankovic J, Le W., Potential therapeutic properties of green tea polyphenols in Parkinson’s disease. Drugs aging, 2003, 20(10), 711-21. Polychronopoulos E, Zeimbekis A, Kastorini CM, Papairakleous N, Vlachou I, Bountziouka V, Panagiotakos DB. Effects of black and green tea consumption on blood glucose levels in non-obese elderly men and women from Mediterranean Islands (MEDIS epidemiological study). Eur J Nutr. 2008 Feb;47(1):10-6. Epub 2008 Jan 18 Popkin BM, Armstrong LE, Bray GM, Caballero B, Frei B, Willett WC, (2006). A new proposed guidance system for beverage consumption in the United States. Am J Clin Nutr, 83, 529-542. Ramsey AC, et al (1975) Fluoride intakes and caries increments in relation to tea consumption by British children. Caries Res 9; 312 Rumpler W, Seale J, Clevidence B, Judd J, Wiley E, Yamamoto S, Komatsu T, Sawaki T, Ishikura Y, Hosoda K. Oolong tea increases metabolic rate and fat oxidation in men. J Nutr 2001;131:28482852. Ryu OH, Lee J, Lee KW, Kim HY, Seo JA, Kim SG, Kim NH, Baik SH, Choi DS, Choi KM. Effects of green tea consumption on inflammation, insulin resistance and pulse wave velocity in type 2 diabetes patients. Diabetes Res Clin Pract. 2006 Mar;71(3):3568. Epub 2005 Sep 19 Schewe T, Steffen Y, Sies H. How do dietary flavanols improve vascular function? A position paper. Archives of biochemistry and biophysics, 2008, 476, 102-106. Schroeter H, Heiss C, Balzer J, Kleinbongard P, Keen CL, Hollenberg NK, et al, (−)-Epicatechin mediates beneficial effects of flavanol-rich cocoa on vascular function in humans.Proc Natl Acad Sci USA 103:1024–1029 (2006). Serafini M, Ghiselli A, FerroLuzzi A. In vivo antioxidant effect of green and black tea in man. European Journal of Clinical Nutri-

tion 1996;50(1):28-32. Serafini M, Laranjinha JAN, Almeida LM, Maiani G. Inhibition of human LDL lipid peroxidation by phenol-rich beverages and their impact on plasma total antioxidant capacity in humans. Journal of Nutritional Biochemistry 2000;11(11-12):585-590. Shanafelt TD et al. Clinical effects of oral green tea extracts in four patients with low grade B-cell malignancies. Leuk Res 2006, 30 (6): 707-12 Smith A (2002). Effects of caffeine on human behaviour. Food and chemical toxicology, 40, 1243-1255. Smit HJ, Rogers PJ. Effects of low doses of caffeine on cognitive performance, mood and thirst in low and higher caffeine consumers. Psychopharmacology (Berl). 2000 Oct;152(2):167-73 Song Y, Manson JE, Buring JE, Sesso HD, Liu S. Associations of dietary flavonoids with risk of type 2 diabetes, and markers of insulin resistance and systemic inflammation in women: a prospective study and cross-sectional analysis. J Am Coll Nutr. 2005 Oct;24(5):376-84. Song JM, Seong BL. Tea catechins as a potential alternative antiinfectious agent. Expert Rev Anti Infect Ther 2007, 5(3), 497506. Stangl V, Lorenz M, Stangl K. The role of tea and tea flavonoids in cardiovascular health. Mol Nutr Food res 2006, 50, 218-228. Sung H, Nah J, Chun S, Park H, Yang SE, Min WK. In vivo antioxidant effect of green tea. European Journal of clinical Nutrition 2000;54(7):527-529. Takashima S, Kataoka K, Shibata E , Hoshino E. The long term intake of catechins improves lipid catabolism during exercise. Prog Med 2004, 24, 3371-3379 Tan EK, Tan C, Fook-Chong SM, Lum SY, Chai A, Chung H, Shen H, Zhao Y, Teoh ML, Yih Y, Pavanni R, Chandran VR, Wong MC. Dose-dependent protective effect of coffee, tea, and smoking in Parkinson’s disease: a study in ethnic Chinese. J Neurol Sci 2003; 216:163– Tan LC, Koh WP, Yuan JM, Wang R, Au WL, Tan JH, Tan EK, Yu MC. Differential effects of black versus green tea on risk of Parkinson’s disease in the Singapore Chinese Health Study. Am J Epidemiol. 2008 Mar 1;167(5):553-60. Epub 2007 Dec 20 Tsubono Y, Tsugane S. Green tea intake in relation to serum lipid levels in Middle-aged Japanese men and women. Ann Epidemiol. 1997 May;7(4):280-4 Tsuchida T, Itakura H, Nakamura H. Reduction of body fat humans by longterm ingestion of catechins. Prog Med 2002;22:21892203. Tsuneki H, Ishizuka M, Terasawa M, Wu JB, Sasaoka T, Kimura IEffect of green tea on blood glucose levels and serum proteomic patterns in diabetic (db/db) mice and on glucose metabolism in healthy humans. BMC Pharmacol. 2004 Aug 26;4:18 Unno T, Tago M, Suzuki Y, Nozawa A, Sagesaka YM, Kakuda T, Egawa K, Kondo K. Effect of tea catechins on postprandial plasma lipid responses in human subjects. Br J Nutr. 2005 Apr;93(4):543-7 US FDA. Letter responding to health claim petition dated January 27, 2004: Green tea and reuced risk of cancer health claim. http://www.cfsan.fda.gov/~dms/qhc-gtea.html VanhetHof KH, deBoer HSM, Wiseman SA, Lien N, Weststrate JA, Tijburg LBM. Consumption of green or black tea does not increase resistance of low-density lipoprotein to oxidation in humans. American Journal of Clinical Nutrition 1997;66(5):11251132. Venables MC, Hulston CJ, Cox HR, Jeukendrup AE. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans. Am J Clin Nutr. 2008 Mar;87(3):778-84.

Vendemiale G, Grattagliano I, Altomare E. An update on the role of free radicals and antioxidant defense in human disease. International Journal of Clinical & Laboratory Research 1999;29(2):49-55. Wei SH, Hattab FN, Mellberg JR. Concentration of fluoride and selected other elements in teas. Nutrition. 1989 JulAug;5(4):237-40 Weinreb O, Mandel S, T Amit, M.B.H. Youdim. Neurological mechanisms of green tea polyphenols in Alzheimer’s and Parkinson’s diseases. Journal of Nutritional Biochemistry 15 (2004) 506–516 Widlansky ME, Hamburg NM, Anter E, Holbrook M, Kahn DF, Elliott JG, Keaney JF, Vita JA. Acute EGCG Supplementation Reverses Endothelial Dysfunction in Patients with Coronary Artery Disease. J Am Coll Nutr. 2007; 26: 95-102 Williams RJ, Spencer JPE, Rice-Evans C. Serial review: Flavonoids and isoflavones (phytoestrogens): Absorption, Metabolism and bioactivity. Free radical biology & medicine, 36, 7, 838-849. Williamson G, Manach C. Bioavailability and bioefficacy of polyphenols in humans. II. Review of 93 intervention studies. Am J Clin Nutr 2005, 81, 243-255. Wolfram S. Effects of green tea and EGCG on cardiovascular and metabolic health. Journal of the American College of nutrition,2007, 26,4, 373-388 Wu CD, Wei, GX. Tea as a functional food for oral health. Nutrition 18, 443-444, 2002. Wu LY, Juan CC, Ho LT, Hsu YP, Hwang LS. Effect of green tea supplementation on insulin sensitivity in Sprague-Dawley rats. J Agric Food Chem. 2004 Feb 11;52(3):643-8 Yamada H, Tateishi M, Harada K, Ohashi T, Shimizu T, Atsumi T, Komagata Y, Iijima H, Komiyama K, Watanabe H, Hara Y, Ohashi K. A randomized clinical study of tea catechin inhalation effects on methicillin-resistant Staphylococcus aureus in disabled elderly patients. J Am Med Dir Assoc. 2006 Feb;7(2):79-83. Epub 2005 Jul 22 Yamada H, Takuma N, Daimon T, Hara Y. Gargling with tea catechin extracts for the prevention of influenza infection in elderly nursing home residents: a prospective clinical study. J Altern Complement Med. 2006 Sep;12(7):669-72 Yamada H, Ohashi K, Atsumi T, Okabe H, Shimizu T, Nishio S, Li XD, Kosuge K, Watanabe H, Hara Y. Effects of tea catechin inhalation on methicillin-resistant Staphylococcus aureus in elderly patients in a hospital ward. J Hosp Infect. 2003 Mar;53(3):22931. Yang CS, Lambert JD, Ju J, Lu G, Sang S. Tea and cancer prevention: molecular mechanisms and human relevance. Toxicology and applied pharmacology 2007, 224, 265-273 Yee YK, Koo MW, Szeto ML. Chinese tea consumption and lower risk of Helicobacter infection. J Gastroenterol Hepatol. 2002 May;17(5):552-5 You SQ. Study on feasibility of Chinese green tea polyphenols (CTP) for preventing dental caries. Zhonghua Kou Qiang Yi Xue Za Zhi. 1993 Jul;28(4):197-9, 254 Yu H, Oho T, Xu LX. Effects of several tea components on acid resistance of human tooth enamel. Journal of Dentistry Vol. 23. No. 2. pp. 101-105. 1995 Yusuf N, Irby C, Katiyar SK, Elmets CA. Photoprotective effects of green tea polyphenols. Photodermatol Photoimmunol Photomed 2007, 23(1), 48-56 Zhu QY, Huang Y, Tsang D, Chen ZY. Regeneration of alpha-tocopherol in human low-density lipoprotein by green tea catechin. Journal of Agricultural and Food Chemistry 1999;47(5):20202025.

liptoninstituteoftea.org

Published February 2009 All information correct at time of going to press For health care professionals only