- Two studies did not measure a validated surrogate endpoint of CVD (i.e., total cholesterol, LDL cholesterol, blood pressure) (Dullo et al., 1999; Samman et al., 2001).<a href="#hdng0">(More...)</a>
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Two studies did not measure a validated surrogate endpoint of CVD (i.e., total cholesterol, LDL cholesterol, blood pressure) (Dullo et al., 1999; Samman et al., 2001). These studies measured endpoints, such as LDL oxidation and antioxidant activity, that are not validated surrogate endpoints of CVD. Because these studies did not measure a validated surrogate endpoint, scientific conclusions about the relationship between green tea extract consumption and risk of CVD cannot be drawn. <a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> There was no significant difference in blood total cholesterol and LDL cholesterol levels between the green tea supplement group and the control group. FDA identified ten observational studies that evaluated the relationship between green tea consumption and risk of CVD. Scientific conclusions could not be drawn from six of these studies for the reasons discussed below.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> The petition requested that the agency authorize a qualified health claim characterizing the relationship between the consumption of green tea and a reduction of a number of risk factors associated with cardiovascular disease (CVD) for use in the labeling of conventional foods and dietary supplements.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Two studies did not conduct statistical analysis between the control and intervention group (Maron et al., 2003; Miura et al., 2000). Statistical analysis of the relationship is a critical factor because it provides the comparison between subjects consuming green tea extract and those not consuming green tea extract to determine whether there is a reduction in CVD risk.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Two studies did not use statistics to evaluate the specific relationship between green tea and CVD risk (statistics measured other parameters in each study) (Imani et al., 1995; Kono et al., 1992). Statistical analysis of the relationship is a critical factor because it provides the comparison between subjects consuming green tea and those not consuming green tea, to determine whether there is a reduction in CVD risk.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Four observational studies evaluated the relationship between green tea consumption and risk of CVD (Sasazuki et al., 2000; Kono et al., 1996; Tsubono and Tsugane, 1997; Tokunaga et al., 2002).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> When statistics are not performed on the specific substance/disease relationship, it cannot be determined whether there is a difference between the two groups. Because this study provided no information about whether green tea extract consumption reduces the risk of CVD, no scientific conclusions could be drawn from it.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Three intervention studies measured the effect of green tea extract consumption on risk of CVD. Young et al. (2002) was a three week randomized, double blind cross-over study of high quality with 16 Danish men (eight nonsmokers, eight smokers).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Four studies did not include a control group for comparing the relative effects of green tea extract consumption (Chantre and Lairon, 2002; Nakagawa et al., 1999; Kajimoto et al., 2003; Kajimoto et al., 2005). Therefore, it could not be determined whether changes in the endpoint of interest were due to green tea extract or to unrelated and uncontrolled extraneous factors. Scientific conclusions could not be drawn from these studies (Spilker, 1991).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Four studies provided no information as to whether the food frequency questionnaires in the studies, which were used for the collection of green tea consumption data from study subjects, had been validated (Nakachi et al., 2000; Nakachi et al., 2003; Hirano et al., 2002; Sano et al., 2004).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Two of the cross-sectional studies and the one hybrid study reported a correlation between green tea consumption and CVD (Kono et al., 1996; Tokunaga et al., 2002, Sasazuki et al., 2000).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Three cross-sectional studies of moderate methodological quality evaluated the relationship between green tea consumption and blood lipids (Kono et al., 1996; Tsubono and Tsugane, 1997; Tokunaga et al., 2002).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Four intervention studies evaluated the relationship between green tea consumption and reduced risk of CVD (Hodgson et al., 1999; Princen et al., 1998; van het Hof et al., 1997; Hirano-Ohmori et al., 2005).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> There were four intervention studies on green tea that established no evidence of an effect. Three of these four studies (Hodgson et al., 1999; Princen et al., 1998; Hirano-Ohmori et al., 2005) were randomized, controlled intervention studies.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> One cross-sectional study reported no correlation (Tsubono and Tsugane, 1997). Because of the presence of the intervention studies discussed above, which were designed and controlled to test the relationship and found no evidence, any potential hypotheses of a correlation between green tea and CVD that were generated by the observational studies here have not been borne out.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> One study examined dietary patterns of green tea drinkers (Tsubono et al., 1997) and one study examined dietary patterns associated with risk factors for CVD (Tsubono et al., 1997; Kerver et al., 2003).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> "Daily consumption of at least 5 fluid ounces (150 mL) of green tea as a source of catechins may reduce a number of risk factors associated with cardiovascular disease. FDA has determined that the evidence is supportive, but not conclusive, for this claim. (Green tea provides 125 mg catechins per serving when brewed from tea and 125 mg catechins as a pre-prepared beverage)."<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> FDA is under no obligation to go beyond the scope of the claim requested in the petition. Because much of the evidence submitted with the petition consisted of studies of green tea in extract form, the agency has decided to treat both forms of green tea, beverage and extract, as subjects of the proposed claim.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
The proposed claim in the petition identified the substance that is the subject of the claim as "green tea as a source of catechins." None of the scientific data evaluated by the agency measured the relationship of individual catechins and CVD. Therefore, the agency considered the relationship between green tea and green tea extract and a reduced risk of CVD.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> The extracts of green tea used in the studies cited by the petitioner were described as being mainly comprised of green tea catechins.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Validation of the food frequency questionnaire method is essential in order to be able to draw conclusions from the scientific data, as the failure to validate may lead to false associations between dietary factors and diseases or disease-related markers. As a result, these studies provided no information on the accuracy of how green tea intake was measured, and hence, no scientific conclusions could be drawn from them.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Nakachi K, Matsuyama S, Miyake S, Suganuma M, Imai K. Preventive effects of drinking green tea on cancer and cardiovascular disease: epidemiological evidence for multiple targeting prevention.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Imai K, Nakachi K. Cross-sectional study of effects of drinking green tea on cardiovascular and liver diseases.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Sano J, Inami S, Seimiya K, Ohba T, Sakai S, Takano T, Mizuno K. Effects of green tea intake on the development of coronary artery disease.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Hirano R, Momiyama Y, Takahashi R, Taniguchi H, Kondo K, Nakamura H, Ohsuzu F. Comparison of green tea intake in Japanese patients with and without angiographic coronary artery disease.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Hirano-Ohmori R, Takahashi R, Momiyama Y, Taniguchi H, Yonemura A, Tamai S, Umegaki K, Nakamura H, Kondo K, Ohsuzu F. Green tea consumption and serum malondialdehyde-modified LDL concentrations in healthy subjects.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Kono S, Shinchi K, Ikeda N, Yanai F, Imanishi K. Green tea consumption and serum lipid profiles: a cross-sectional study in northern Kyushu, Japan.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> The study identified a significant decrease in blood total and LDL cholesterol levels with the consumption of ten cups of green tea per day.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> There was a significant decrease in blood total cholesterol reported in men and women with increased consumption of green tea. Sasazuki et al. (2000) was a Japanese study described by its authors as a cross-sectional study. It appears to have used a hybrid design applying case-control analysis to data obtained through cross-sectional methods.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Freese et al. (1999) was a four week randomized, double blind, placebo controlled intervention study of moderate quality that provided Finnish women a diet rich in linoleic acid and a gelatin capsule containing 3 g of green tea extract or diet rich in linoleic acid and a placebo capsule. Ten additional control subjects who consumed their habitual diets were also used.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Hodgson et al. (1999) was an Australian randomized cross-over intervention study of moderate quality in which 13 men and women consumed water and caffeine (control group) or green tea (1,000 milliliters (mL)), each for seven days.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Princen et al. (1998) was a four week randomized, single blind, placebo controlled parallel design intervention study of high quality in which Dutch male and female smokers consumed 900 mL mineral water (control group, n 15), or 3.6 g green tea polyphenol supplement ( n 13) for four weeks.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Hirano-Ohmori et al. (2005) was a randomized Japanese crossover intervention study of moderate quality in which 22 men consumed 700 mL green tea or water (control group) each for two weeks.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Each group consumed a standardized diet low in flavonoids (control group) or a standardized diet with green tea extract added to meat patties for three weeks each.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> No significant difference in blood total cholesterol levels was found between the green tea extract group and control group.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> There was no association between green tea intake and blood total cholesterol concentration.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Tsubono and Tsugane (1997) correlated blood total cholesterol levels and green tea intake in 1,000 Japanese men and women.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Kono et al. (1996) correlated blood total and LDL cholesterol levels and green tea intake in 2,062 Japanese males.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Tokunaga et al. (2002) correlated blood total cholesterol and green tea intake in 13, 916 Japanese men and women.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> There was no significant association between green tea intake and coronary artery disease for the entire group.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> The agency concludes that green tea, in either beverage or extract form, is a specific food or component of food and thus meets the definition of substance in the health claim regulation (21 CFR 101.14(a)(2)). A disease or health-related condition means damage to an organ, part, structure, or system of the body such that it does not function properly, or a state of health leading to such dysfunctioning (21 CFR 101.14(a)(5)).<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Samman S, Sandstrom B, Toft MB, Bukhave K, Jensen M, Sorensen SS, Hansen M. Green tea or rosemary extract added to foods reduces nonheme-iron absorption.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Freese R, Basu S, Hietanen E, Nair J, Nakachi K, Bartsch H, Mutanen M. Green tea extract decreases plasma malondialdehyde concentration but does not affect other indicators of oxidative stress, nitric oxide production, or hemostatic factors during a high-linoleic acid diet in healthy females.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Miura Y, Chiba T, Miura S, Tomita I, Umegaki K, Ikeda M, Tomita T. Green tea polyphenols (flavan 3-ols) prevent oxidative modification of low density lipoproteins: an ex vivo study in humans.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Nagaya N, Yamamoto H, Uematsu M, Itoh T, Nakagawa K, Miyazawa T, Kangawa K, Miyatake K Green tea reverses endothelial dysfunction in healthy smokers.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Young JF, Dragstedt LO, Haraldsdottir J, Daneshvar B, Kal MA, Loft S, Nilsson L, Nielsen SE, Mayer B, Skibsted LH, Huynh-Ba T, Hermetter A, Sandstrom B. Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> 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 theaflavin-enriched green tea extract: a randomized controlled trial.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Gomikawa S, Ishikawa Y. Effects of catechins and ground green tea drinking on the susceptibility of plasma and LDL to the oxidation in vitro and ex vivo.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> 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.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Sung H, Nah J, Chun S, Park H, Yang SE, Min WK. In vivo antioxidant effect of green tea.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Sung H, Min WK, Lee W, Chun S, Park H, Lee YW, Jang S, Lee DH. The effects of green tea ingestion over four weeks on atherosclerotic markers.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> 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.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
In a subgroup analysis which excluded subjects that were under dietary or drug therapy for diabetes (126 cases of coronary artery disease and 323 controls), there was a significant association between the consumption of four or more cups of green tea per day and decreased incidence of coronary artery disease in men.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Erba D, Riso P, Bordoni A, Foti P, Biagi PL, Testolin G. Effectiveness of moderate green tea consumption on antioxidative status and plasma lipid profile in humans.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> There was no significant difference in systolic or diastolic blood pressure between the group who consumed green tea and control group.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> The petition identified green tea as the substance that is the subject of the proposed claim.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Tsubono Y, Tsugane S. Green tea intake in relation to serum lipid levels in Middle-aged Japanese men and women.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Tsubono Y, Takahashi T, Iwase Y, Iitoi Y, Akabane M, Tsugane S. Dietary differences with green tea intake among middle-aged Japanese men and women.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Chantre P, Lairon D. Recent findings of green tea extract AR25 (Exolise) and its activity for the treatment of obesity.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Green tea is a brewed beverage made by infusing hot water with the dried natural tea leaves of Camellia sinensis (also referred to as Thea sinensis ). Green tea differs from other types of tea, such as black or oolong, in that green tea is made with unfermented tea leaves, while black and oolong tea are made with fermented leaves.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Animal study reports that tannin fractions from tea plants may increase the risk of cancer, although it is not clear that the tannin present in green tea has significant carcinogenic effects in humans. Drinking tannin-containing beverages such as tea may contribute to iron deficiency, and in infants, tea has been associated with impaired iron metabolism and microcytic anemia.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Laboratory studies, animal studies, and limited human research suggest possible effects of green tea on cholesterol levels. Better human evidence is necessary in this area.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Green tea has been shown to increase or have no effect on blood pressure in several studies in humans.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Green tea may contain vitamin K, which when used in large quantities can reduce the blood thinning effects of warfarin (Coumadin®), a phenomenon that has been reported in a human case.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a>
Overall, the relationship of green tea consumption and human cancer remains inconclusive.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Gao YT, McLaughlin JK, Blot WJ, et al. Reduced risk of esophageal cancer associated with green tea consumption.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Laurie SA, Miller VA, Grant SC., et al. Phase I study of green tea extract in patients with advanced lung cancer.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> A study conducted in healthy postmenopausal women showed that a morning/evening menopausal formula containing green tea was effective in relieving menopausal symptoms including hot flashes and sleep disturbance. Further studies are needed to confirm these results.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> There are several small human studies addressing the use of green tea extract (GTE) capsules for weight loss or weight maintenance in overweight or average weight individuals.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Berube-Parent S, Pelletier C, Dore J, et al. 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.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Maron DJ, Lu GP, Cai NS, et al. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Fukino Y, Shimbo M, Aoki N, et al. Randomized controlled trial for an effect of green tea consumption on insulin resistance and inflammation markers.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> In preliminary research, green tea has been associated with decreased levels of estrogens in the body. It is not clear if significant side effects such as hot flashes may occur.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Lowering of blood sugar levels from drinking green tea has also been reported in preliminary research. Additional study is needed in this area.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> An increase in blood sugar levels may occur. Caffeine-containing beverages such as green tea should be used cautiously in patients with diabetes.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a>
There is early suggestive evidence that regular intake of green tea may reduce the risk of heart attack or atherosclerosis (clogged arteries). Further well-designed clinical trials are needed before a firm recommendation can be made in this area.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Based on preliminary data, theanine, a specific glutamate derivative in green tea, may reduce the adverse reactions caused to the heart and liver by the prescription cancer drug doxorubicin. Further research is needed to confirm these results.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> L-theanine is a predominant amino acid found in green tea. Preliminary research exists on the effects of this amino acid in comparison with the prescription drug alprazolam on experimentally induced anxiety.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Cola nut, guarana ( Paullina cupana ), and yerba mate ( Ilex paraguariensis ) are also sources of caffeine, and may add to the effects and side effects of caffeine in green tea.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Chow HH, Hakim IA, Vining DR, et al. Effects of dosing condition on the oral bioavailability of green tea catechins after single-dose administration of Polyphenon E in healthy individuals.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Kuntze, Camellia tea, catechins, Chinese tea, EGCG, epigallocatechin-3-gallate, Exolise®, flavonol, GTE, green tea extract, Matsu-cha Tea, polyphenols, Polyphenon E, Thea bohea, Thea sinensis, Thea viridis, Theanine, Theifers.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> One clinical trial showed minimal benefit using green tea extract capsules for the treatment of hormone refractory prostate cancer.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Chiu AE, Chan JL, Kern DG, et al. Double-blinded, placebo-controlled trial of green tea extracts in the clinical and histologic appearance of photoaging skin.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> In capsule form, there is considerable variation in the amount of green tea extract (GTE); there may be anywhere from 100 to 750 milligrams per capsule.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Most studies have examined green tea in the form of a brewed beverage, rather than in capsule form.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> More studies are required to determine if green tea and polyphenols have any therapeutic benefit for diabetes prevention or treatment.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> There is limited animal and human study of green tea as a protective agent of skin from ultraviolet light skin injury.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> In humans, preliminary date suggests that a specific formulation of green tea may help prevent cold and flu symptoms. Further well-designed clinical trials are needed to confirm these results.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Early research using a combination product called FertilityBlend has been associated with some success in helping women to conceive. Further well-designed research on green tea alone for this use is needed before a strong conclusion can be drawn.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Research indicates that green tea may benefit arthritis by reducing inflammation and slowing cartilage breakdown.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Additional well-designed controlled research is needed before a recommendation can be made for or against green tea in the treatment of HTLV-1 carriers.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Preliminary research suggests green tea decreases viral load in carriers of the HTLV-1 virus.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Limited, low-quality research reports that the use of green tea may improve cognition and sense of alertness.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Green tea is a source of caffeine, for which multiple interactions have been documented. The combination of caffeine with ephedrine, an ephedra alkaloid, has been implicated in numerous severe or life-threatening cardiovascular events such as very high blood pressure, stroke, or heart attack.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Westerterp-Plantenga MS, Lejeune MP, Kovacs EM. Body weight loss and weight maintenance in relation to habitual caffeine intake and green tea supplementation.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Large amounts of green tea should be used cautiously in pregnant women, as caffeine crosses the placenta and has been associated with spontaneous abortion, intrauterine growth retardation, and low birth weight.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Green tea is a source of caffeine, for which multiple interactions have been documented.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Green tea is a source of caffeine, for which multiple reactions are reported.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Green tea is not recommended for infants or children due to caffeine content.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> People with known allergy/hypersensitivity to caffeine or tannin should avoid green tea.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Based on preliminary data, ingestion of green tea may lower LDL ("bad") cholesterol, and thus may theoretically interact with other cholesterol-lowering herbs and supplements.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Based on preliminary data, ingestion of green tea may lower LDL cholesterol and thus may theoretically interact with other cholesterol-lowering drugs. Other potential interactions may include drugs such as adenosine, alcohol, anticoagulants, antidiabetics, antipsychotics, fluconazole, hydrocortisone, levodopa, MAOI antidepressants, methoxsalen, phenytoin, proton pump inhibitors (PPIs), riluzole, terbinafine, theophylline, and timolol.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Choan E, Segal R, Jonker D, et al. A prospective clinical trial of green tea for hormone refractory prostate cancer: an evaluation of the complementary/alternative therapy approach.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a>
There are not enough reliable data to determine whether green tea can aid in weight loss, lower blood cholesterol levels, or protect the skin from sun damage. NCCAM is supporting studies to learn more about the components in green tea and their effects on conditions such as cancer, diabetes, and heart disease.<a href="
http://nccam.nih.gov/health/greentea/" TARGET="_blank"
[3]</a> Laboratory studies suggest that green tea may help protect against or slow the growth of certain cancers, but studies in people have shown mixed results. Some evidence suggests that the use of green tea preparations improves mental alertness, most likely because of its caffeine content.<a href="
http://nccam.nih.gov/health/greentea/" TARGET="_blank"
[3]</a> Green tea and green tea extracts, such as its component EGCG, have been used to prevent and treat a variety of cancers, including breast, stomach, and skin cancers.<a href="
http://nccam.nih.gov/health/greentea/" TARGET="_blank"
[3]</a> Green tea and green tea extracts have also been used for improving mental alertness, aiding in weight loss, lowering cholesterol levels, and protecting skin from sun damage.<a href="
http://nccam.nih.gov/health/greentea/" TARGET="_blank"
[3]</a> Green tea extracts can be taken in capsules and are sometimes used in skin products.<a href="
http://nccam.nih.gov/health/greentea/" TARGET="_blank"
[3]</a> Caffeine can also raise blood pressure, and in very high doses, it can cause seizures, delirium, or irregular heart rhythms. Green tea contains small amounts of vitamin K, which can make anticoagulant drugs, such as warfarin, less effective. Tell your health care providers about any herb A plant or part of a plant used for its flavor, scent, or potential therapeutic properties.<a href="
http://nccam.nih.gov/health/greentea/" TARGET="_blank"
[3]</a> Includes flowers, leaves, bark, fruit, seeds, stems, and roots. or dietary supplement A product that contains vitamins, minerals, herbs or other botanicals, amino acids, enzymes, and/or other ingredients intended to supplement the diet. The U.S. Food and Drug Administration has special labeling requirements for dietary supplements and treats them as foods, not drugs. you are using, including green tea. This helps to ensure safe and coordinated care.<a href="
http://nccam.nih.gov/health/greentea/" TARGET="_blank"
[3]</a> ' High salt intake and the incidence H. Pylori infection are more prevalent in Japan than in the United States (Hoenberger et al., 2003; Key et al., 2004). High salt intake and H. Pylori infection are forms of bias for the green tea and gastric cancer relationship in Japan in that they each affect the risk of developing gastric cancer independent of green tea consumption."<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> The remaining study, a case control, received a high methodological quality rating (Le Marchand et al., 2000).' Le Marchand et al. (2000) conducted a case-control study in Hawaii with 582 lung cancer cases and 582 controls.' Green tea intake had no association with lung cancer incidence, and the adjusted odds ratio for the highest quartile of green tea intake was 0.9 (95% CI 0.5-1.6) compared to the lowest quartile of green tea intake.<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Zhong L., Goldberg MS., Gao Y., Hanley JA., Perent M., Jin F.' "A population-based case control study of lung cancer and green tea consumption among women living in Shanghai, China."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Nagano J., Kono S., Preston DL., Mabuchi K.' "A prospective study of green tea consumption and cancer incidence, Hiroshima and Nagsaki Japan."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Studies from the U.S. or other applicable countries (countries with H. Pylori infection rates and salt intake that are similar to the United States) are needed as part of the total body of evidence to evaluate green tea consumption and gastric cancer risk."<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Koizumi Y., Tsubono Y., Nakaya N., Nishino Y., Shibuya D., Matsuoka H., Tsuji I.' "No association between green tea and the risk of gastric cancer: pooled analysis of two prospective studies in Japan."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Inoue M., Tajima K., Mizutani M., Iwata H., Iwase T., Miura S., Hirose K., Hamajima N., Tominaga S.' "Regular consumption of green tea and the risk of breast cancer recurrence:' follow-up study from the hospital based epidemiologic research program at Aichi Cancer Center, Japan."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Wu et al. (2003) was a case-control study that evaluated green tea intake and breast cancer risk in female Asian Americans living in Southern California, and used 501 cases and 504 controls.' Drinking 85.7 milliliters of green tea per day was significantly associated with a decreased risk of breast cancer; odds ratio 0.47 (95% CI 0.25-0.85).<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Mu LN., Zhou XF., Ding BG., Wang RH.,' Zhang ZF., Chen CW., Wei GR., Zhou XM., Jian QW., Yu SZ.' "A case-control study on drinking green tea and decreasing risk of cancers in the alimentary canal among cigarette smokers and alcohol drinkers."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Gao YT., McLaughlin JK., Blot WJ., Ji BU., Dai Q., Fraumeni JF.' "Reduced risk of esophageal cancer associated with green tea consumption."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Ji, B., Chow, W., Yang, G., McLaughlin, J.K., Gao, R., Zheng, W., Shu, X., Jin, F., Fraumeni, J.F., Gao, Y.' "The influence of cigarette smoking, alcohol, and green tea consumption on the risk of carcinoma of the cardia and distal stomach in Shanghai, China."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Setiawan VW., Zhang ZF., Yu GP., Lu QY., Li YL., Lu ML., Wang MR., Guo CH., Yu SZ., Kurtz RC., Hsieh CC.' "Protective effect of green tea on the risks of chronic gastritis and stomach cancer."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Imai K., Litt D., Suga K., Nakachi K.' "Cancer preventive effect of drinking green tea among a Japanese population."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Jian L., Xie LP., Lee AH., Binns CW.' "Protective effect of green tea against prostate cancer: a case-control study in southeast China."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> We considered but rejected use of a disclaimer or qualifying language to accompany the proposed claims for green tea and cancers other than breast cancer and prostate cancer. We concluded that neither a disclaimer nor qualifying language would suffice to prevent consumer deception in these instances, where there is no credible evidence to support the claims.<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> ' Sonoda et al. (2004) included 140 Japanese prostate cancer cases and controls.' Drinking two to ten cups of green tea per day was not significantly associated with prostate cancer risk; odds ratio 0.67 (95% CI 0.27-1.64).<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Nakachi K., Suemasu K., Suga K., Takeo T., Imai K., Higashi Y.' "Influence of drinking green tea on breast cancer malignancy among Japanese patients."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> NCI, DCPC Chemoprevention Branch and Agent Development Committee.' "Clinical development plan: tea extracts, green tea polyphenols, epigallocatechin gallate."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a>
The study concluded drinking green tea has limited antitumor benefit for prostate cancer patients (5). Other ongoing NCI studies are testing green tea as a preventive agent against skin cancer. One is investigating the protective effects of a pill form of green tea against sun-induced skin damage while another explores the topical application of green tea in shrinking precancerous skin changes.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> One recently completed but unpublished NCI trial studied the antitumor effect of green tea among prostate cancer patients.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> The 42 patients drank 6 grams of green tea, or about 4 cups, daily for four months. Only one patient experienced a short-lived improvement, and nearly 70 percent of the group experienced unpleasant side effects such as nausea and diarrhea.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> For more information about NCI-sponsored studies on green tea, go to
http://www.cancer.gov/clinical_trials/ <a href="
http://cancer.gov/clinical_trials/">
http://www.cancer.gov/clinical_trials/</a> <a href="
http://cancer.gov/clinical_trials/">
http://www.cancer.gov/clinical_trials/</a>.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> Two studies in China, where green tea is a mainstay of the diet, resulted in promising findings.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> Possibly because it is less processed, green tea contains higher levels of antioxidants than black tea. Although tea is consumed in a variety of ways and varies in its chemical makeup, one study showed steeping either green or black tea for about five minutes released over 80 percent of its catechins.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> National Cancer Institute (NCI) researchers are also investigating the therapeutic use of green tea.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a>
A 2005 statement appearing on the FDA website asserts, "Existing evidence does not support qualified health claims for green tea consumption and a reduced risk of any other type of cancer." Katiyar suggests that some epidemiologic and clinical studies on green tea and cancer may have failed to adequately control for variables such as climate, race, diet and frequency of tea consumption, which can dramatically influence green tea's effects.<a href="
http://www.research.va.gov/news/features/green_tea.cfm" TARGET="_blank"
[6]</a> A native of India who became a U.S. citizen in the 1990s, Katiyar drinks two cups a day of green tea. He says people with fairer skin, who are at higher risk for skin cancer, may need to drink up to six cups per day to derive benefit. For the perfect cup of tea, he advises that people boil water, remove it from the heat, and then steep the leaves, covered, for four or five minutes.<a href="
http://www.research.va.gov/news/features/green_tea.cfm" TARGET="_blank"
[6]</a> For many centuries, green tea has been consumed and used medicinally in India, China, Japan and other Asian countries. Today, millions worldwide not only drink green tea but look for it in their sunscreen, shampoo and even toothpaste.<a href="
http://www.research.va.gov/news/features/green_tea.cfm" TARGET="_blank"
[6]</a>
"Anecdotal evidence over time, particularly in China, points to a relationship between green tea consumption and weight loss," says Rumpler. "But until we do a really comprehensive study in which we have humans drink tea and see whether they lose weight, we can't actually say that green tea makes people lose weight.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> Some are looking at the effect of green tea on slowing development of abnormal blood vessels in lab mice.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> "Over the last 4 years, green tea consumption increased tremendously, going from 3 to 4 percent of total tea consumed in the United States to about 9 percent today," says Joe Simrany, president of the New York City-based Tea Council of the U.S. Simrany says the council is seeking a standardized system for measuring and labeling commercial teas' antioxidants.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a>
Princen HM, van DW, Buytenhek R, Blonk C, Tijburg LB, Langius JA, Meinders AE, Pijl H. No effect of consumption of green and black tea on plasma lipid and antioxidant levels and on LDL oxidation in smokers.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Hodgson JM, Puddey IB, Burke V, Beilin LJ, Jordan N. Effects on blood pressure of drinking green and black tea.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Serafini M, Ghiselli A, Ferro-Luzzi A. In vivo antioxidant effect of green and black tea in man.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
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Section Contents:<a name="top"></a>
- When statistics are not performed on the specific substance/disease relationship, it cannot be determined whether there is a difference between the two groups.<a href="#hdng3">(More...)</a>
<a name="hdng3"></a>
When statistics are not performed on the specific substance/disease relationship, it cannot be determined whether there is a difference between the two groups. Because this study provided no information about whether green consumption reduces the risk of CVD, no scientific conclusions could be drawn from it. <a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Arts IC, Hollman PC, Feskens EJ, Bueno de Mesquita HB, Kromhout D. Catechin intake might explain the inverse relation between tea consumption and ischemic heart disease: the Zutphen Elderly Study.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Kajimoto O, Kaijmoto Y, Yabune M, Nozawa A, Nagata K, Kakuda T. Tea catechins reduce serum cholesterol levels in mild borderline hypercholesterolemic patients.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Kajimoto O, Kajimoto Y, Yabune M, Nakamura T, Kotani K, Suzuki Y, Nozawa A, Nagata K, Unno T, Sagesaka Y, Kakuda T, Yoshikawa T. Tea Catechins with a galloyl moiety reduce body weight and fat.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Nakagawa K, Ninomiya M, Okubo T, Aoi N, Juneja LR, Kim M, Yamanaka K, Miyazawa T. Tea catechin supplementation increases antioxidant capacity and prevents phospholipid hydroperoxidation in plasma of humans.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Leenen R, Roodenburg AJ, Tijburg LB, Wiseman SA. A single dose of tea with or without milk increases plasma antioxidant activity in humans.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Hodgson JM, Croft KD, Mori TA, Burke V, Beilin LJ, Puddey IB. Regular ingestion of tea does not inhibit in vivo lipid peroxidation in humans.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Yang YC, Lu FH, Wu JS, Wu CH, Chang CJ. The protective effect of habitual tea consumption on hypertension.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Mukamal KJ, Maclure M, Muller JE, Sherwood JB, Mittleman MA. Tea consumption and mortality after acute myocardial infarction.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a> Geleijnse JM, Launer LJ, Hofman A, Pols HA, Witteman JC. Tea flavonoids may protect against atherosclerosis: the Rotterdam Study.<a href="
http://www.cfsan.fda.gov/~dms/qhcgtea2.html" TARGET="_blank"
[1]</a>
Several preliminary studies have examined the effects of caffeine, tea, or coffee use on short and long-term memory and cognition. It remains unclear if tea is beneficial for this use.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Tannin in tea can cause constipation. Certain doses of caffeine can increase heart rate and blood pressure, although people who consume caffeine regularly do not seem to experience these effects in the long-term.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Research has shown caffeine to cause improvements in airflow to the lungs (bronchodilation). It is not clear if caffeine or tea use has significant benefits in people with asthma. Better research is needed in this area before a strong conclusion can be drawn.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> One cup of tea contains approximately 50 milligrams of caffeine and 80 to 100 milligrams of polyphenol content, depending on the strength of the tea and the size of cup.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a>
There is limited study of tea as a gargle (mouthwash) for the prevention of dental cavities (caries). It is not clear if this is a beneficial therapy.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a> Historically, tea has been served as a part of various ceremonies and has been used to stay alert during long meditations. A legend in India describes the story of Prince Siddhartha Gautama, the founder of Buddhism, who tore off his eyelids in frustration at his inability to stay awake during meditation while journeying through China. A tea plant is said to have sprouted from the spot where his eyelids fell, providing him with the ability to stay awake, meditate, and reach enlightenment.<a href="
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html" TARGET="_blank"
[2]</a>
Some epidemiological studies comparing tea drinkers to non-tea drinkers support the claim that drinking tea prevents cancer; others do not. Dietary, environmental, and population differences may account for these inconsistencies.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> Instant iced tea, on the other hand, contains negligible amounts of catechins (1). In the laboratory, studies have shown tea catechins act as powerful inhibitors of cancer growth in several ways: They scavenge oxidants before cell injuries occur, reduce the incidence and size of chemically induced tumors, and inhibit the growth of tumor cells.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> Like other antioxidants, the catechins found in tea selectively inhibit specific enzyme activities that lead to cancer. They may also target and repair DNA aberrations caused by oxidants (1).<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> NCI researchers are investigating the therapeutic and preventive use of tea catechins against a variety of cancers (see Question 5).<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> BMC Derm 2001; 1 (3). (3) Sun CL, Yuan JM, Lee MJ, Yang CS, Gao YT, Ross RK, Yu MC. Urinary tea polyphenols in relation to gastric and esophageal cancers: a prospective study of men in shanghai, china.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> Tea drinking is an ancient tradition dating back 5,000 years in China and India. Long regarded in those cultures as an aid to good health, researchers now are studying tea for possible use in the prevention and treatment of a variety of cancers.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a>
Although tea has long been identified as an antioxidant in the laboratory, study results involving humans have been contradictory.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> Carcin 2002; 23 (9): 1497-1503. (4) Goldbohm RA, Hertog MG, Brants HA, van Poppel G, van den Brandt PA. Consumption of black tea and cancer risk: a prospective cohort study.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a>
Zhang M., Binns CW., Lee AH.' "Tea consumption and ovarian cancer risk: a case-control study in China."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a> Inoue M., Tajima K., Hirose N., Hamajima N., Takezaki T., Kuroishi T., Tominaga S.' "Tea and coffee consumption and the risk of digestive tract cancers: data from a comparative case-referent study in Japan."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a>
Hakim, I.A., Harris, R.B., Weisgerber, U.M.' "Tea intake and squamous cell carcinoma of the skin:' influence of type of tea beverages."'<a href="
http://www.cfsan.fda.gov/~dms/qhc-gtea.html" TARGET="_blank"
[4]</a>
J. Nutri Biochem 2001; 12 (7): 404-421. (2) Hakim IA, Harris RB. Joint effects of citrus peel use and black tea intake on risk of squamous cell carcinoma of the skin.<a href="
http://www.cancer.gov/newscenter/pressreleases/tea" TARGET="_blank"
[5]</a> Some have studied the relationship between tea and metabolism, and some have looked at the effect of tea on blood glucose and cholesterol levels. Others are studying tea's impact on the ability of the body's cells to handle oxidative stress.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> Ernst J. Schaefer, director of the HNRCA's Lipid Metabolism Laboratory, recently completed a pilot study during which 8 volunteers with type II diabetes had lower blood sugar levels by 15 to 20 percent after drinking 6 cups of tea per day for 8 weeks.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> Perhaps most interesting was that fat oxidation was a significant 12 percent higher after the full-strength tea treatment than after the water treatment. "Our data suggested that a component of tea other than caffeine might have promoted preferential use of fat as an energy source," says Beverly Clevidence, a study coauthor and head of the DHPL. "But the information is tentative, and we need more studies to confirm it," she adds.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> "Some studies are simply not sensitive enough to eliminate confounding factors," says ARS chemist Joseph T. Judd, who is with DHPL. In the case of tea studies, it could be as simple as a volunteer's getting the same flavonoids that are in tea from other foods consumed during the study.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> Judd is now conducting a study on the antioxidant effects of tea phytonutrients on smokers.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> "There has been only one study that showed that adding milk decreased the bioavailability of catechins in tea," says Blumberg. "Those results were not replicated in any of several subsequent studies."<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> In a third study period, caffeine was added to the tea-flavored water in an amount similar to that found in the tea.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> During a tea nutrition study, physiologists David J. Baer and David Paul (in the background, Baer is on the left) review calorimetry data from a study volunteer inside a calorimeter. It is universally accepted that caffeinated tea raises metabolic rate because caffeine is a stimulant.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> To measure how tea influences energy expenditure (EE), Rumpler and colleagues gave each of 12 male volunteers 4 separate beverage formulas for 3 consecutive days. Before the study, the volunteers refrained from consuming caffeine and had their 24-hour EE measured.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> "The interesting part of our study, which agreed with findings from a similar study in England, was that when you drink tea you turn on the fat-burning spigot a little bit more than when you drink caffeinated water," says Rumpler.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a>
In September 2002, ARS and other researchers met at the U.S. Department of Agriculture in Washington, D.C., for the Third International Scientific Symposium on Tea and Human Health.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> For some 5,000 years, people have been getting a lift from brewing tea leaves. It's only been in the last three decades that researchers have immersed themselves in the science behind tea's purported health benefits.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> "Brewing Up the Latest Tea Research" was published in the September 2003 September 2003 issue of Agricultural Research magazine.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a>
Some scientists speculate that caffeine and EGCG - a highly active catechin in tea - may act together to increase fat oxidation.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> The treatments consisted of full-strength tea, colored water with caffeine equal to full-strength tea, half-strength tea, and colored water. The results showed that the EE of volunteers was about 3 percent higher after they drank either the caffeinated water or the full-strength tea than after they drank the colored water. On average, the volunteers burned an additional 67 calories a day when they drank tea instead of an equal amount of water.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a>
Many factors can affect the way tea compounds are absorbed, metabolized, and excreted, according to Blumberg.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> Milk protein, for example, when added to tea, had previously been reported to possibly bind to, and therefore reduce, the flavonoid concentrations.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a> To achieve a variety of taste profiles, manufacturers carefully control whether, and for how long, tea leaves are exposed to air, a process called fermentation.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a>
Judd's recent study assessed the effects of black tea consumption on blood lipid and lipoprotein concentrations in adults with mildly high cholesterol. He carefully controlled the volunteers' diet and weight.<a href="
http://www.ars.usda.gov/is/AR/archive/sep03/tea0903.htm" TARGET="_blank"
[7]</a>
Research suggests that each type of tea may possess unique beneficial compounds.<a href="
http://www.research.va.gov/news/features/green_tea.cfm" TARGET="_blank"
[6]</a>
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