Green tea

Green tea/Drug Interactions:

  • GeneralGeneral: This section focuses on potential interactions with green tea. Most drug interactions associated with green tea are predominantly theoretical and generally based on the adverse effect profile of caffeine. For more potential interactions based on caffeine itself, the Natural Standard monograph on caffeine is available.
  • Angiotensin-converting enzyme (ACE) inhibitorsAngiotensin-converting enzyme (ACE) inhibitors: In vitro, green tea inhibited angiotensin-converting enzyme (58; 59).
  • Alzheimer's agentsAlzheimer's agents: Several preliminary studies have examined the effects of caffeine, tea, or coffee use on short and long-term memory and alertness (182; 183). Although it remains unclear if green tea is beneficial for this use, there is a potential for additive effects between green tea and Alzheimer's agents.
  • Antiacne agentsAntiacne agents: Clinical research suggests that epigallocatechin gallate (EGCG) improves acne in humans (65). Further clinical research is required to determine the effect of green tea and its extract.
  • Antiallergy agentsAntiallergy agents: In human research, benifuuki green tea containing O-methylated catechin reduced symptoms associated with Japanese cedar pollinosis (144).
  • AntiandrogensAntiandrogens: Theoretically, green tea may interact with antiandrogens.
  • AntiarthriticsAntiarthritics: In vitro, epigallocatechin gallate (EGCG), a component of green tea, inhibited IL-1beta-induced expression of matrix metalloproteinase-1 and -13 in human chondrocytes, as well as activated the mitogen-activated protein kinase subgroup c-Jun N-terminal kinase (184; 185). EGCG reduced the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as the production of NO and prostaglandin E(2), in human chondrocytes treated with interleukin (IL)-1beta (186; 187). Other in vitro (188) and animal studies (189) have also indicated anti-inflammatory properties of green tea.
  • AntiasthmaticsAntiasthmatics: Exposure to green tea dust has been suggested as increasing symptoms of asthma in some individuals (95), and green tea has also been suggested as inducing asthma (96).
  • AntibioticsAntibiotics: In vitro, antibiotic effects of green tea and its constituents have been shown (190; 10; 191; 192; 193; 194; 195; 196; 197; 198; 199; 105; 200).
  • Anticoagulants and antiplateletsAnticoagulants and antiplatelets: In in vitro and animal research, both catechins and caffeine in green tea exhibited antiplatelet activity (14; 15). In one case report, large amounts (one-half to one gallon) of green tea antagonized the effects of warfarin, possibly due to the small amounts of vitamin K in green tea (109; 110). In laboratory research, dry green tea leaves contained significantly more vitamin K than black tea leaves; green tea may contain 1,428mcg of vitamin K per 100g of leaf, while black tea may contain only 262mcg of vitamin K per 100g of leaf (111). Suboptimal anticoagulation control with warfarin was documented in patients that used common herbs (garlic, ginger, green tea, papaya) at least four times weekly (201). In a clinical trial, consumption of green tea did not inhibit platelet aggregation (202).
  • AntidiabeticsAntidiabetics: From available laboratory and human research, the effect of green tea or its constituents on blood glucose or other markers is mixed. Hypoglycemia was reported by one subject in a clinical trial (76). In human research, caffeine or green tea was shown to modulate blood sugar levels and affect levels of insulin and insulin resistance (203; 132), and EGCG decreased blood glucose and/or insulin in animal (204) and human research (205). However, in patients without diabetes, plasma glucose levels were higher two hours following ingestion of a meal, when the meal was consumed with green tea vs. water (99). Also, preliminary research suggests that green tea lacks an effect on blood sugar or insulin levels in many individuals (152; 76; 134; 151; 163; 132; 136; 129); however, the consumption of green tea was inversely associated with risk for diabetes in epidemiological research (206). Green tea extract decreased streptozotocin-induced increases in blood glucose in rats (100).
  • AntiestrogensAntiestrogens: According to epidemiological evidence, a relationship between green tea consumption and decreased estrogen levels in humans may exist (113). In human research, in combination with chasteberry, as well as with various vitamins, minerals, and amino acids, green tea has been associated with increased success in helping women to conceive (207). In human research, green tea in combination with other agents (such as black cohosh, soy, and kava) has been associated with relieving menopausal symptoms, including hot flashes and sleep disturbances (208).
  • AntihypertensivesAntihypertensives: In clinical research, green tea (49) and green tea extracts (50) increased systolic and diastolic blood pressure. Increases in blood pressure have been shown in further human research (51; 52; 53). However, there is controversy in this area, and several clinical trials have not shown these effects (209; 210; 211; 212; 213; 129) or have demonstrated blood pressure-lowering effects (160; 132), including one case of hypotension (54). In epidemiological research, habitual tea drinking, including green tea, reduced the prevalence of developing hypertension (214). In clinical research, L-theanine, a constituent of green tea, inhibited the increases in blood pressure observed in the high-response group (individuals whose blood pressure increased more than average during the mental task and after placebo intake) (215).
  • Anti-inflammatoriesAnti-inflammatories: In human research, effects of green tea or its constituents on inflammatory mediators were mixed. Significant effects of green tea were lacking on inflammatory mediators in the blood, such as CRP, adiponectin, IL-6, IL-1beta, soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), and leptin (128). However, in other human research, green tea reduced plasma levels of serum amyloid alpha (SAA) (128) and levels of IL-6, TNF-alpha, and/or CRP (150; 132). In vitro, EGCG, a component of green tea, inhibited the expression of matrix metalloproteinase-1 and -13 in human chondrocytes treated with interleukin (IL)-1beta, as well as activated the mitogen-activated protein kinase subgroup c-Jun N-terminal kinase (184; 185). EGCG also reduced the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as the production of NO and prostaglandin E(2), in human chondrocytes treated with IL-1beta (186; 187). Other in vitro (188) and animal studies (189) have also indicated anti-inflammatory properties of green tea.
  • AntilipemicsAntilipemics: Research available in systematic reviews and meta-analysis suggests that green tea has beneficial effects on blood lipids (158; 157; 66; 131); however, studies in patients with hyperlipidemia are limited. Also, in vitro (17), animal (216; 204), and human (217; 218; 77; 155; 159; 219; 157; 66; 158; 220; 205; 131; 132; 136; 135; 221) studies have demonstrated the antilipemic effects of green tea and green tea catechins. Most commonly, total cholesterol was reduced, although responses of LDL cholesterol and triglycerides (decrease) and HDL cholesterol (increase) varied between studies. A lack of effect on lipid profiles, however, has also been reported in human trials using green tea (222; 123; 129). In humans, theaflavin-enriched green tea decreased levels of total and LDL cholesterol (155).
  • AntineoplasticsAntineoplastics: Various reviews (223; 224; 225; 34; 226; 227; 228; 229; 230; 231; 232; 233; 234; 235; 236; 237; 238; 239; 240; 44), human clinical trials and population-based studies (241; 242; 243; 244; 245; 246; 247; 248; 249; 250; 175; 251; 252; 253; 254; 255; 256; 257; 258; 259; 260; 261; 124; 262; 263; 264; 265; 266; 267; 268; 269; 270; 271; 272; 273; 274; 275; 276; 277; 278; 279; 280; 281; 282; 283; 284; 285; 286; 287), other human studies (148; 47; 60; 48; 147; 72; 50; 255; 253; 254; 256; 257; 258; 259; 260; 261; 124; 262), and in vitro and in vivo studies (288; 289; 290; 291; 292; 293; 294; 295; 296; 297; 29; 298; 299; 300; 301; 302; 303; 125; 304; 305; 306; 307; 308; 309; 310; 311; 312; 313; 314; 315; 316; 317; 318; 319; 320; 321; 322; 323; 324; 325) have been undertaken to examine the possible association between green tea consumption and cancer incidence and have indicated mixed results in the reduction of cancer risk with use of green tea. The combination of green tea and doxorubicin induced a 37% reduction in tumor weight and a 2.5-fold increase in doxorubicin's inhibitory effect on tumor growth in mice (326). There was no increase in doxorubicin concentration in normal tissue. In vitro, EGCG modulated apoptosis induced by gemcitabine (GEM), mitomycin C, or 5-fluorouracil, and mitochondrial membrane depolarization, cytosolic cytochrome c expression, and apoptosis increased in cells incubated with EGCG and GEM compared with either agent alone in KMCH, CC-LP-1, and Mz-ChA-1 human cholangiocarcinoma cells (327). In laboratory research, green tea polyphenols blocked the anticancer effects of bortezomib and other boronic acid-based proteasome inhibitors (328). In one study, it was determined that among patients with cancer, green tea was included as an herbal remedy most often used that had potential interactions with the chemotherapy they were also receiving due to similar metabolism via cytochrome P450-metabolizing enzymes (CYPs) and/or the p-glycoprotein (P-gp) transporter (35). A possible association between green tea consumption and pancreatic cancer risk has been discussed (101).
  • Antiobesity agentsAntiobesity agents: There are mixed results concerning the effect of green tea on obesity (161; 160; 329; 136; 137; 135; 134; 129; 77), although endpoints lack consistency and a meta-analysis suggested a lack of effect on weight loss or weight maintenance (53); in a separate analysis, effects were small when caffeine was included (165). In human research, green tea in combination with other herbal agents, such as bitter orange and guarana, increased carbohydrate oxidation (330).
  • AntipsychoticsAntipsychotics: Coffee and tea withdrawal does not appear to increase the bioavailability of chlorpromazine, haloperidol, fluphenazine, and trifluoperazine or affect the individual variation in plasma levels (331).
  • AntiviralsAntivirals: Polyphenols from green tea have demonstrated antiviral activity in vitro (332; 333; 334; 335; 336), and in human research, daily intake of capsulated green tea for five months diminished the human T cell lymphocytic virus (HTLV-1) provirus load (154). In humans, preliminary data suggest that specific formulations of green tea may help prevent cold and flu symptoms (69), and in children, consumption of 1-5 cups of green tea daily was associated with a reduced risk of developing influenza (337). Various clinical trials have suggested a benefit of green tea constituent topical treatments for anogenital warts (168; 62; 61; 63; 64).
  • AnxiolyticsAnxiolytics: Human research suggests some evidence of benefit of L-theanine, a constituent of green tea, for anxiety (338; 215).
  • Athletic performance enhancersAthletic performance enhancers: Overall evidence is mixed with respect to the effect of green tea or its constituents on exercise performance in human research (127; 145; 146). In human research, green tea polyphenols improved muscular endurance (142) and prevented a rise in plasma creatine kinase activity seen in the placebo group following exercise (339).
  • BenzodiazepinesBenzodiazepines: In animal research, one week of treatment with green tea extract increased C(max) and AUC(0-infinity) of orally administered midazolam without changing the half-life (340).
  • CaffeineCaffeine: Green tea is a source of caffeine. Theoretically, there may be additive side effects with other products containing caffeine. A combination product containing bitter orange, caffeine, and green tea lacked an effect on heart rate or blood pressure (341).
  • Cardiovascular agentsCardiovascular agents: According to various reviews (342; 41; 343; 219) and animal and human research, green tea and/or its constituents increased or decreased blood pressure, reduced LDL oxidation, inhibited platelet activation and aggregation, decreased lipid and lipoprotein levels, and modified endothelial activity (344; 345; 346; 347; 348; 349; 350; 351; 51; 52; 53; 160; 54; 49; 50). Evidence from randomized controlled trials with cardiovascular risk marker outcomes is mixed (74; 132; 150; 128; 129; 352; 220; 353). Reported cardiovascular adverse effects to products containing green tea have included atrial fibrillation (55) and thrombotic thrombocytopenic purpura (56). In human research, EGCG decreased heart rate during rest; however, effects were lacking during exercise (145). Effects of green tea alone or in combination with other agents were lacking in other human research (134; 341).
  • ClozapineClozapine: In animal research, administration of green tea extract did not alter the elimination half-life of clozapine; however, the time to reach peak concentration was increased and the maximal peak plasma concentration of clozapine was lower following green tea extract administration (354).
  • ContraceptivesContraceptives: In human research, a product containing green tea catechins and other ingredients reduced oxidative stress in individuals treated with low-estrogen contraceptives (355; 356). In preliminary epidemiological research, green tea was associated with decreased levels of estrogens in the body (113).
  • COX-2 inhibitorsCOX-2 inhibitors: In human research, effects of green tea or its constituents on inflammatory mediators were mixed. EGCG, a component of green tea, reduced the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as the production of NO and prostaglandin E(2), in human chondrocytes treated with IL-1beta (186; 187). Other in vitro (188) and animal studies (189) have also indicated anti-inflammatory properties of green tea.
  • Cytochrome P450metabolized agentsCytochrome P450-metabolized agents: According to reviews, tea has been reported to induce cytochrome P450 enzymes 1A1, 1A2, 2B1, and 3A4 (116; 117; 118). However, in one study in healthy humans, green tea extract did not alter the pharmacokinetics of two cytochrome P450 3A4 or 2D6 probe drugs, dextromethorphan, and alprazolam (119). Another study also showed that green tea extract did not affect the activity of CYP1A2, CYP2D6, CYP2C9, and CYP3A4 (118). In vitro, green tea extract, but not epigallocatechin gallate, induced CYP1A2 mRNA expression, whereas CYP1A1 and CYP3A4 mRNA expression may not be affected (357).
  • Dental and periodontal agentsDental and periodontal agents: Researchers have mentioned that fluoride from green tea may interact with oral tissue (139). EGCG has been shown to reduce the progression of dental erosion in a clinical trial, possibly mediated through its ability to inhibit MMP enzymes (358). In another clinical trial, green tea was examined as a rinsing aid to prevent bacteria in the oral cavity (359). In human research, green tea decreased plaque (360) and salivary and plaque Streptococcus mutans, as well as salivary pH (139). In epidemiological research, intake of green tea decreased clinical signs of periodontal disease (361). Green tea protected against mineral loss from an intraoral appliance after an acid challenge and fluoride levels in the surface layers improved (140).
  • Dermatologic agentsDermatologic agents: Dermatologic adverse effects related to topical use of green tea ointments have included cervical and vaginal inflammation, vaginal irritation, pustular vulvovaginitis, and vulval burning, as well as local skin reactions, erythema, rash, burning, hives, itching, edema, dryness, irritation, sun sensitivity, and erosion (60; 61; 62; 63; 64; 65; 66; 67; 68; 69). According to secondary sources, topical exposure to tannins may play a role in exacerbations of pemphigus (a chronic bullous skin disorder seen in people who are genetically predisposed). Pigmented contact cheilitis has been indicated as a result of exposure to green tea (70). There has been limited human research on green tea in photoaging, with mixed evidence of benefit (68; 94; 362; 138; 363; 67).
  • DiureticsDiuretics: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • DoxorubicinDoxorubicin: In animal research, the combination of green tea and doxorubicin induced a reduction in tumor weight and an increase in doxorubicin's inhibitory effect on tumor growth in Ehrlich ascites carcinoma tumor-bearing mice (326). There was no increase in doxorubicin concentration in normal tissue. Theanine, a component of green tea, has been suggested to reduce the adverse reactions of doxorubicin (364).
  • Drugs that may lower seizure thresholdDrugs that may lower seizure threshold: In a case report, seizure activity and unresponsiveness was suggested to be due to Hydroxycut? ingestion; however, the role of green tea is unclear, as the formulation of Hydroxycut? has changed over the years (112).
  • Drugs used for osteoporosisDrugs used for osteoporosis: Using bone biomarkers, green tea polyphenols appear to offer benefit for bone health (142) and may be safe and possibly improve quality of life in osteopenic women (91); however, clinical evidence on bone mass is lacking.
  • Fertility agentsFertility agents: Early research using a combination product containing green tea, called FertilityBlend, has been associated with some success in helping women to conceive (207). However, there is a lack of available research investigating the use of green tea alone for fertility.
  • FluorideFluoride: Researchers have mentioned that fluoride from green tea may interact with oral tissue (139). According to secondary sources, green tea, a source of fluoride, may cause skeletal fluorosis.
  • Gastrointestinal agentsGastrointestinal agents: Gastrointestinal adverse effects (excess gas, upset stomach, nausea, vomiting, constipation, diarrhea, heartburn, stomach ache, and abdominal pain) have been associated with the consumption of green tea or green tea and constituent supplements (71; 72; 73; 74; 75; 66; 76; 53; 54; 77; 50; 78). In epidemiological research, factors associated with gastroesophageal reflux disease included drinking green tea (79).
  • Genitourinary tract agentsGenitourinary tract agents: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • Heart rate-regulating agentsHeart rate-regulating agents: In human research, EGCG decreased heart rate during rest; however, effects were lacking during exercise (145). Effects of green tea alone or in combination with other agents were lacking in other human research (134; 341). In a case report, the EGCG component of Hydroxycut? was thought to be responsible for atrial fibrillation (55).
  • Hematological agentsHematological agents: In clinical research, impaired iron metabolism and microcytic anemia occurred in infants (102). In a case study, green tea containing 250mg of ascorbic acid per 100g of tea induced transient acceleration of intravascular hemolysis in a 67 year-old man with paroxysmal nocturnal hemoglobinuria (107). The daily consumption of an average of 250mL of tea by infants has been shown to impair iron metabolism, resulting in a high incidence of microcytic anemia (180). Green tea extract has been shown to inhibit the formation of dense red blood cells in vitro (365).
  • HepatotoxinsHepatotoxins: According to various case reports and a review, hepatotoxicity (80; 81; 82; 83; 27) and acute or fulminant hepatitis (84; 85; 86; 87; 88; 89) has been associated with use of green tea products. In clinical trials, slightly elevated alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) occurred (the relationship to green tea or constituents is unclear) (90; 91). However, one systematic review found that an increased consumption of green tea may reduce the risk of liver disease (366), and in a clinical trial, an increased consumption of green tea, especially more than 10 cups daily, was related to decreased concentrations of hepatological markers in serum, AST (p=0.06), ALT (p=0.07), and ferritin (p=0.02), indicating that green tea may act protectively against disorders of the liver (367). In human research, green tea or its constituents lacked an effect on AST, ALT, or blood urea nitrogen (BUN) (91).
  • Hormonal agentsHormonal agents: Epidemiological research suggests a relationship between green tea consumption and decreased estrogen levels in humans (113). In animal research, green tea reduced blood levels of testosterone, estradiol, leptin, luteinizing hormone, and insulin-like growth factor (204); however, in human research, Polyphenon E? lacked consistent effects on testosterone, estradiol, and estrone levels (205). In human research, in combination with chasteberry, as well as with various vitamins, minerals, and amino acids, green tea was associated with increased success in helping women to conceive (207), and green tea in combination with other agents (such as black cohosh, soy, and kava) was associated with relieving menopausal symptoms, including hot flashes and sleep disturbances (208).
  • Hormone replacement therapyHormone replacement therapy: Epidemiological research suggests a relationship between green tea consumption and decreased estrogen levels in humans (113). In animal research, green tea reduced blood levels of testosterone, estradiol, leptin, luteinizing hormone, and insulin-like growth factor (204); however, in human research, Polyphenon E? lacked consistent effects on testosterone, estradiol, and estrone levels (205). In human research, in combination with chasteberry, as well as with various vitamins, minerals, and amino acids, green tea was associated with increased success in helping women to conceive (207), and green tea in combination with other agents (such as black cohosh, soy, and kava) was associated with relieving menopausal symptoms, including hot flashes and sleep disturbances (208).
  • ImmunosuppressantsImmunosuppressants: In human research, increased proliferation of gamma-delta T cells from subjects taking green tea, and secretion of IFN-gamma occurred (69). In isolated CD19+ B cells, EGCG decreased the expression of CD11b and suppressed CD11b-mediated migration and adhesion of B cells to endothelial cells (181).
  • Iron saltsIron salts: In human research, impaired iron metabolism and microcytic anemia occurred in infants (102). In clinical research, in thalassemia major and intermedia patients, tea caused an inhibition of iron absorption (103). Decreased nonheme absorption has been shown in young women consuming foods with green tea added (104). However, it has also been suggested that green tea does not inhibit iron absorption (368; 369). According to a review, it is recommended that vegetarians drink tea between meals, as tea binds to dietary iron found in plant sources and decreases the availability (absorption) of iron (105). In an epidemiological review, tea consumption was associated with a reduced iron status only in groups with a high prevalence of deficiency (106). Also, one study included in the review suggested that in middle-aged men at risk of iron overload, tea consumption may lower serum ferritin concentrations.
  • Musculoskeletal agentsMusculoskeletal agents: In a clinical trial, oral consumption of EGCG from green tea or a decaffeinated green tea polyphenol mixture for four weeks resulted in mild muscle pain (71). According to secondary sources, green tea, a source of fluoride, may cause skeletal fluorosis.
  • Neurologic agentsNeurologic agents: Theoretically, the caffeine constituent of green tea may cause nervousness, agitation, habituation, and psychological dependence, with withdrawal symptoms. In human research, use of green tea or constituents of green tea such as caffeine, has resulted in dizziness, headache, and nervous system stimulation resulting in symptoms such as delirium, confusion, restlessness, and insomnia (71; 72; 73; 92; 61; 75; 54; 93; 50). In vitro and in animal research, EGCG exerted neuroprotective effects in models of Alzheimer's and Parkinson diseases (370; 371; 372). In a clinical trial involving EGCG, beneficial effects on cognitive performance, mood, and localized cerebral blood flow were lacking in healthy adults (141); however, EGCG increased alpha, beta, and theta activity, mainly in the frontal and medial frontal gyrus (133) and brain theta waves in the temporal, frontal, parietal, and occipital areas (373).
  • NicotineNicotine: Additive effects on cardiovascular parameters may occur with nicotine (57). In a systematic review and meta-analysis, a subgroup analysis found a potential interaction with green tea and smoking that produced a moderate increased risk of bladder cancer (242).
  • Ophthalmic agentsOphthalmic agents: Watery and puffy eyes were reported by one subject in a clinical trial (69). In a clinical trial of oral green tea polyphenols (GTPs), retinal detachment occurred six months into the study; however, it was uncertain whether this was related to the study agent (94).
  • P-glycoprotein regulated drugsP-glycoprotein regulated drugs: The involvement of green tea in p-glycoprotein regulation has been reviewed (374; 37). In vitro, green tea polyphenols inhibited p-glycoprotein activity (120; 121). In human research, it was determined that among patients with cancer, green tea was included as an herbal remedy most often used that had potential interactions with the chemotherapy they were also receiving due to similar metabolism via cytochrome P450-metabolizing enzymes (CYPs) and/or the p-glycoprotein (P-gp) transporter (35).
  • Renal agentsRenal agents: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • Renally eliminated agentsRenally eliminated agents: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • Respiratory agentsRespiratory agents: Exposure to green tea dust has been suggested as increasing symptoms of asthma in some individuals (95), and green tea has also been suggested as inducing asthma (96). In a case report, hypersensitivity pneumonitis was associated with inhalation of catechin-rich green tea extracts (98). A 67 year-old woman, who for 15 years used infusions of green tea to wash her nasal cavities, was diagnosed with granulomatous alveolitis with lymph follicles (97). Green tea consumption was associated with a lower risk of death from pneumonia in women in epidemiological research (375); however, green tea was less effective than CYSTUS052? for upper respiratory tract symptoms (54).
  • Sulfotransferase 1A3 (SULT1A3) substratesSulfotransferase 1A3 (SULT1A3) substrates: In vitro, green tea inhibited the sulfation of dopamine and ritodrine, two substrates of SULT1A3 (376).
  • TacrolimusTacrolimus: Increased plasma levels of tacrolimus following the consumption of green tea have been discussed (377). Further details are lacking.
  • TamoxifenTamoxifen: In vitro, a combination of green tea and tamoxifen inhibited the proliferation of estrogen receptor-positive breast cancer cells compared to tamoxifen alone (378).
  • VasodilatorsVasodilators: In clinical research of endothelial function in patients with chronic renal failure, green tea significantly improved flow-mediated dilation (353).
  • VasopressorsVasopressors: In clinical research of endothelial function in patients with chronic renal failure, green tea significantly improved flow-mediated dilation (353).
  • Wound-healing agentsWound-healing agents: EGCG has been shown to affect the role that TGF-beta1 plays in fibroblast populated collagen gel contraction, an effect that is possibly mediated through myofibroblast differentiation and connective tissue growth factor gene expression (379). Additional details, however, are lacking.

    • Green tea/Herb/Supplement Interactions:

  • GeneralGeneral: This section focuses on potential interactions with green tea. Most herb-supplement interactions associated with green tea are predominantly theoretical and generally based on the adverse effect profile of caffeine. For more potential interactions based on caffeine itself, the Natural Standard monograph on caffeine is available.
  • Angiotensin-converting enzyme (ACE) inhibitorsAngiotensin-converting enzyme (ACE) inhibitors: In vitro, green tea inhibited angiotensin-converting enzyme (58; 59).
  • Alzheimer's agentsAlzheimer's agents: Several preliminary studies have examined the effects of caffeine, tea, or coffee use on short and long-term memory and alertness (182; 183). Although it remains unclear if green tea is beneficial for this use, there is a potential for additive effects between green tea and Alzheimer's agents.
  • Antiacne agentsAntiacne agents: Clinical research suggests that EGCG improves acne in humans (65). Further clinical research is required to determine the effect of green tea and its extract.
  • Antiallergy agentsAntiallergy agents: In human research, benifuuki green tea containing O-methylated catechin reduced symptoms associated with Japanese cedar pollinosis (144).
  • AntiandrogensAntiandrogens: Theoretically, green tea may interact with antiandrogens.
  • AntiarthriticsAntiarthritics: In vitro, epigallocatechin gallate (EGCG), a component of green tea, inhibited IL-1beta-induced expression of matrix metalloproteinase-1 and -13 in human chondrocytes, as well as activated the mitogen-activated protein kinase subgroup c-Jun N-terminal kinase (184; 185). EGCG reduced the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as the production of NO and prostaglandin E(2), in human chondrocytes treated with interleukin (IL)-1beta (186; 187). Other in vitro (188) and animal studies (189) have also indicated anti-inflammatory properties of green tea.
  • AntiasthmaticsAntiasthmatics: Exposure to green tea dust has been suggested as increasing symptoms of asthma in some individuals (95), and green tea has also been suggested as inducing asthma (96).
  • AntibacterialsAntibacterials: In vitro, antibiotic effects of green tea and its constituents have been shown (190; 10; 191; 192; 193; 194; 195; 196; 197; 198; 199; 105; 200).
  • Anticoagulants and antiplateletsAnticoagulants and antiplatelets: In in vitro and animal research, both catechins and caffeine in green tea exhibited antiplatelet activity (14; 15). In one case report, large amounts (one-half to one gallon) of green tea antagonized the effects of warfarin, possibly due to the small amounts of vitamin K in green tea (109; 110). In laboratory research, dry green tea leaves contained significantly more vitamin K than black tea leaves; green tea may contain 1,428mcg of vitamin K per 100g of leaf, while black tea may contain only 262mcg of vitamin K per 100g of leaf (111). Suboptimal anticoagulation control with warfarin was documented in patients that used common herbs (garlic, ginger, green tea, papaya) at least four times weekly (201). In a clinical trial, consumption of green tea did not inhibit platelet aggregation (202).
  • AntiestrogensAntiestrogens: According to epidemiological evidence, a relationship between green tea consumption and decreased estrogen levels in humans may exist (113). In human research, in combination with chasteberry, as well as with various vitamins, minerals, and amino acids, green tea has been associated with increased success in helping women to conceive (207). In human research, green tea in combination with other agents (such as black cohosh, soy, and kava) has been associated with relieving menopausal symptoms, including hot flashes and sleep disturbances (208).
  • Anti-inflammatoriesAnti-inflammatories: In human research, effects of green tea or its constituents on inflammatory mediators were mixed. Significant effects of green tea were lacking on inflammatory mediators in the blood, such as CRP, adiponectin, IL-6, IL-1beta, soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), and leptin (128). However, in other human research, green tea reduced plasma levels of serum amyloid alpha (SAA) (128) and levels of IL-6, TNF-alpha, and/or CRP (150; 132). In vitro, EGCG, a component of green tea, inhibited the expression of matrix metalloproteinase-1 and -13 in human chondrocytes treated with interleukin (IL)-1beta, as well as activated the mitogen-activated protein kinase subgroup c-Jun N-terminal kinase (184; 185). EGCG also reduced the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as the production of NO and prostaglandin E(2), in human chondrocytes treated with IL-1beta (186; 187). Other in vitro (188) and animal studies (189) have also indicated anti-inflammatory properties of green tea.
  • AntilipemicsAntilipemics: Research available in systematic reviews and meta-analysis suggests that green tea has beneficial effects on blood lipids (158; 157; 66; 131); however, studies in patients with hyperlipidemia are limited. Also, in vitro (17), animal (216; 204), and human (217; 218; 77; 155; 159; 219; 157; 66; 158; 220; 205; 131; 132; 136; 135; 221) studies have demonstrated the antilipemic effects of green tea and green tea catechins. Most commonly, total cholesterol was reduced, although responses of LDL cholesterol and triglycerides (decrease) and HDL cholesterol (increase) varied between studies. A lack of effect on lipid profiles, however, has also been reported in human trials using green tea (222; 123; 129). In humans, theaflavin-enriched green tea decreased levels of total and LDL cholesterol (155).
  • AntineoplasticsAntineoplastics: Various reviews (223; 224; 225; 34; 226; 227; 228; 229; 230; 231; 232; 233; 234; 235; 236; 237; 238; 239; 240; 44), human clinical trials and population-based studies (241; 242; 243; 244; 245; 246; 247; 248; 249; 250; 175; 251; 252; 253; 254; 255; 256; 257; 258; 259; 260; 261; 124; 262; 263; 264; 265; 266; 267; 268; 269; 270; 271; 272; 273; 274; 275; 276; 277; 278; 279; 280; 281; 282; 283; 284; 285; 286; 287), other human studies (148; 47; 60; 48; 147; 72; 50; 255; 253; 254; 256; 257; 258; 259; 260; 261; 124; 262), and in vitro and in vivo studies (288; 289; 290; 291; 292; 293; 294; 295; 296; 297; 29; 298; 299; 300; 301; 302; 303; 125; 304; 305; 306; 307; 308; 309; 310; 311; 312; 313; 314; 315; 316; 317; 318; 319; 320; 321; 322; 323; 324; 325) have been undertaken to examine the possible association between green tea consumption and cancer incidence and have indicated mixed results in the reduction of cancer risk with use of green tea. The combination of green tea and doxorubicin induced a 37% reduction in tumor weight and a 2.5-fold increase in doxorubicin's inhibitory effect on tumor growth in mice (326). There was no increase in doxorubicin concentration in normal tissue. In vitro, EGCG modulated apoptosis induced by gemcitabine (GEM), mitomycin C, or 5-fluorouracil, and mitochondrial membrane depolarization, cytosolic cytochrome c expression, and apoptosis increased in cells incubated with EGCG and GEM compared with either agent alone in KMCH, CC-LP-1, and Mz-ChA-1 human cholangiocarcinoma cells (327). In laboratory research, green tea polyphenols blocked the anticancer effects of bortezomib and other boronic acid-based proteasome inhibitors (328). In one study, it was determined that among patients with cancer, green tea was included as an herbal remedy most often used that had potential interactions with the chemotherapy they were also receiving due to similar metabolism via cytochrome P450-metabolizing enzymes (CYPs) and/or the p-glycoprotein (P-gp) transporter (35). A possible association between green tea consumption and pancreatic cancer risk has been discussed (101).
  • Antiobesity agentsAntiobesity agents: There are mixed results concerning the effect of green tea on obesity (161; 160; 329; 136; 137; 135; 134; 129; 77), although endpoints lack consistency and a meta-analysis suggested a lack of effect on weight loss or weight maintenance (53). In a separate analysis, effects were small when caffeine was included (165). In human research, green tea in combination with other herbal agents, such as bitter orange and guarana, increased carbohydrate oxidation (330).
  • AntioxidantsAntioxidants: In human, animal, and in vitro research, green tea, alone or in combination with other agents, increased antioxidant potential and decreased oxidative stress (156; 219; 380; 232; 30; 381; 382; 339; 153; 383; 384; 129; 150; 132; 385; 218; 303; 386; 202; 11; 387; 388).
  • AntipsychoticsAntipsychotics: Coffee and tea withdrawal does not appear to increase the bioavailability of chlorpromazine, haloperidol, fluphenazine, and trifluoperazine or affect the individual variation in plasma levels (331).
  • AntiviralsAntivirals: Polyphenols from green tea have demonstrated antiviral activity in vitro (332; 333; 334; 335; 336), and in human research, daily intake of capsulated green tea for five months diminished the human T cell lymphocytic virus (HTLV-1) provirus load (154). In humans, preliminary data suggest that specific formulations of green tea may help prevent cold and flu symptoms (69), and in children, consumption of 1-5 cups of green tea daily was associated with a reduced risk of developing influenza (337). Various clinical trials have suggested a benefit of green tea constituent topical treatments for anogenital warts (168; 62; 61; 63; 64).
  • AnxiolyticsAnxiolytics: Human research suggests some evidence of benefit of L-theanine, a constituent of green tea, for anxiety (338; 215).
  • Ascorbic acidAscorbic acid: In human research, single doses of tea catechins decreased ascorbate levels briefly (122); however, effects of green tea extract on ascorbic acid levels were lacking in a separate study (123). In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389). In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation all improved.
  • Athletic performance enhancersAthletic performance enhancers: Overall evidence is mixed with respect to the effect of green tea or its constituents on exercise performance in human research (127; 145; 146). In human research, green tea polyphenols improved muscular endurance (142) and prevented a rise in plasma creatine kinase activity seen in the placebo group following exercise (339).
  • Bitter orangeBitter orange: Theoretically, bitter orange may add to the possible hypertensive effects of green tea. A combination product containing bitter orange, caffeine, and green tea lacked an effect on heart rate or blood pressure (341).
  • Caffeine containing agentsCaffeine containing agents: Green tea is a source of caffeine. Theoretically, there may be additive side effects with other products containing caffeine. A combination product containing bitter orange, caffeine, and green tea lacked an effect on heart rate or blood pressure (341).
  • Cardiovascular agentsCardiovascular agents: According to various reviews (342; 41; 343; 219) and animal and human research, green tea and/or its constituents increased or decreased blood pressure, reduced LDL oxidation, inhibited platelet activation and aggregation, decreased lipid and lipoprotein levels, and modified endothelial activity (344; 345; 346; 347; 348; 349; 350; 351; 51; 52; 53; 160; 54; 49; 50). Evidence from randomized controlled trials with cardiovascular risk marker outcomes is mixed (74; 132; 150; 128; 129; 352; 220; 353). Reported cardiovascular adverse effects to products containing green tea have included atrial fibrillation (55) and thrombotic thrombocytopenic purpura (56). In human research, EGCG decreased heart rate during rest; however, effects were lacking during exercise (145). Effects of green tea alone or in combination with other agents were lacking in other human research (134; 341).
  • CatechinsCatechins: Theoretically, the bioavailability of catechins, constituents of green tea, may decrease when ingested with food.
  • CitrusCitrus: In epidemiological research, reduced cancer incidence in individuals consuming citrus was further reduced in individuals also consuming green tea (391).
  • Cola nutCola nut: Theoretically, caffeine from green tea may add to the effects of caffeine from cola nut.
  • ContraceptivesContraceptives: In human research, a product containing green tea catechins and other ingredients reduced oxidative stress in individuals treated with low-estrogen contraceptives (355; 356). In preliminary epidemiological research, green tea was associated with decreased levels of estrogens in the body (113).
  • COX inhibitorsCOX inhibitors: In human research, effects of green tea or its constituents on inflammatory mediators were mixed. EGCG, a component of green tea, reduced the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as the production of NO and prostaglandin E(2), in human chondrocytes treated with IL-1beta (186; 187). Other in vitro (188) and animal studies (189) have also indicated anti-inflammatory properties of green tea.
  • Cytochrome P450metabolized agentsCytochrome P450-metabolized agents: According to reviews, tea has been reported to induce cytochrome P450 enzymes 1A1, 1A2, 2B1, and 3A4 (116; 117; 118). However, in one study in healthy humans, green tea extract did not alter the pharmacokinetics of two cytochrome P450 3A4 or 2D6 probe drugs, dextromethorphan and alprazolam (119). Another study also showed that green tea extract did not affect the activity of CYP1A2, CYP2D6, CYP2C9, and CYP3A4 (118). In vitro, green tea extract, but not epigallocatechin gallate, induced CYP1A2 mRNA expression, whereas CYP1A1 and CYP3A4 mRNA expression may not be affected (357).
  • Dental and periodontal agentsDental and periodontal agents: Researchers have mentioned that fluoride from green tea may interact with oral tissue (139). EGCG has been shown to reduce the progression of dental erosion in a clinical trial, possibly mediated through its ability to inhibit MMP enzymes (358). In another clinical trial, green tea was examined as a rinsing aid to prevent bacteria in the oral cavity (359). In human research, green tea decreased plaque (360) and salivary and plaque Streptococcus mutans, as well as salivary pH (139). In epidemiological research, intake of green tea decreased clinical signs of periodontal disease (361). Green tea protected against mineral loss from an intraoral appliance after an acid challenge and fluoride levels in the surface layers were improved (140).
  • Dermatologic agentsDermatologic agents: Dermatologic adverse effects related to topical use of green tea ointments have included cervical and vaginal inflammation, vaginal irritation, pustular vulvovaginitis, and vulval burning, as well as local skin reactions, erythema, rash, burning, hives, itching, edema, dryness, irritation, sun sensitivity, and erosion (60; 61; 62; 63; 64; 65; 66; 67; 68; 69). According to secondary sources, topical exposure to tannins may play a role in exacerbations of pemphigus (a chronic bullous skin disorder seen in people who are genetically predisposed). Pigmented contact cheilitis has been indicated as a result of exposure to green tea (70). There has been limited human study of green tea in photoaging, with mixed evidence of benefit (68; 94; 362; 138; 363; 67).
  • DiureticsDiuretics: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • Fertility agentsFertility agents: Early research using a combination product containing green tea, called FertilityBlend, has been associated with some success in helping women to conceive (207). However, there is a lack of available research investigating the use of green tea alone for fertility.
  • Fluoride-containing agentsFluoride-containing agents: Researchers have mentioned that fluoride from green tea may interact with oral tissue (139). According to secondary sources, green tea, a source of fluoride, may cause skeletal fluorosis.
  • Folic acidFolic acid: In human research, researchers noted a potential interaction between tea and folic acid, with even low concentrations (0.3g of extract/250mL) of green and black tea extracts yielding decreased bioavailabilities of folic acid (115). In vitro, catechins and tea extracts inhibited folic acid uptake (114).
  • Gastrointestinal agentsGastrointestinal agents: Gastrointestinal adverse effects (excess gas, upset stomach, nausea, vomiting, constipation, diarrhea, heartburn, stomach ache, and abdominal pain) have been associated with the consumption of green tea or green tea and constituent supplements (71; 72; 73; 74; 75; 66; 76; 53; 54; 77; 50; 78). In epidemiological research, factors associated with gastroesophageal reflux disease included drinking green tea (79).
  • Genitourinary tract agentsGenitourinary tract agents: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • GrapefruitGrapefruit: Theoretically, concomitant administration of green tea with grapefruit juice may increase caffeine levels and the risk of adverse effects.
  • GrapeGrape: In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389).
  • GuaranaGuarana: Theoretically, caffeine from green tea may add to the effects of caffeine from guarana.
  • Heart rate-regulating agentsHeart rate-regulating agents: In human research, EGCG decreased heart rate during rest; however, effects were lacking during exercise (145). Effects of green tea, alone or in combination with other agents, were lacking in other human research (134; 341). In a case report, the EGCG component of Hydroxycut? was thought to be responsible for atrial fibrillation (55).
  • HematologicsHematologics: In clinical research, impaired iron metabolism, and microcytic anemia occurred in infants (102). In a case study, green tea containing 250mg of ascorbic acid per 100g of tea induced transient acceleration of intravascular hemolysis in a 67 year-old man with paroxysmal nocturnal hemoglobinuria (107). The daily consumption of an average of 250mL of tea by infants has been shown to impair iron metabolism, resulting in a high incidence of microcytic anemia (180). Green tea extract has been shown to inhibit the formation of dense red blood cells in vitro (365).
  • HepatotoxinsHepatotoxins: According to various case reports and a review, hepatotoxicity (80; 81; 82; 83; 27) and acute or fulminant hepatitis (84; 85; 86; 87; 88; 89) has been associated with use of green tea products. In clinical trials, slightly elevated alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) occurred (the relationship to green tea or constituents is unclear) (90; 91). However, one systematic review found that an increased consumption of green tea may reduce the risk of liver disease (366), and in a clinical trial, an increased consumption of green tea, especially more than 10 cups daily, was related to decreased concentrations of hepatological markers in serum, AST (p=0.06), ALT (p=0.07), and ferritin (p=0.02), indicating that green tea may act protectively against disorders of the liver (367). In human research, green tea or its constituents lacked an effect on AST, ALT, or blood urea nitrogen (BUN) (91).
  • Hormonal agentsHormonal agents: Epidemiological research suggests a relationship between green tea consumption and decreased estrogen levels in humans (113). In animal research, green tea reduced blood levels of testosterone, estradiol, leptin, luteinizing hormone, and insulin-like growth factor (204); however, in human research, Polyphenon E? lacked consistent effects on testosterone, estradiol, and estrone levels (205). In human research, in combination with chasteberry, as well as with various vitamins, minerals, and amino acids, green tea was associated with increased success in helping women to conceive (207), and green tea in combination with other agents (such as black cohosh, soy, and kava) was associated with relieving menopausal symptoms, including hot flashes and sleep disturbances (208).
  • Hormone replacement therapyHormone replacement therapy: Epidemiological research suggests a relationship between green tea consumption and decreased estrogen levels in humans (113). In animal research, green tea reduced blood levels of testosterone, estradiol, leptin, luteinizing hormone, and insulin-like growth factor (204); however, in human research, Polyphenon E? lacked consistent effects on testosterone, estradiol, and estrone levels (205). In human research, in combination with chasteberry, as well as with various vitamins, minerals, and amino acids, green tea was associated with increased success in helping women to conceive (207), and green tea in combination with other agents (such as black cohosh, soy, and kava) was associated with relieving menopausal symptoms, including hot flashes and sleep disturbances (208).
  • Huperzine AHuperzine A: In in vitro research, EGCG enhanced the inhibitory effect of huperzine A on acetylcholinesterase (392).
  • Hypertensives and hypotensivesHypertensives and hypotensives: In clinical research, green tea (49), and green tea extracts (50) increased systolic and diastolic blood pressure. Increases in blood pressure have been shown in further human research (51; 52; 53). However, there is controversy in this area, and several clinical trials have not shown these effects (209; 210; 211; 212; 213; 129) or have demonstrated blood pressure-lowering effects (160; 132), including one case of hypotension (54). In epidemiological research, habitual tea drinking, including green tea, reduced the prevalence of developing hypertension (214). In clinical research, L-theanine, a constituent of green tea, inhibited the increases in blood pressure observed in the high-response group (individuals whose blood pressure increased more than average during the mental task and after placebo intake) (215).
  • HypoglycemicsHypoglycemics: From available laboratory and human research, the effect of green tea or its constituents on blood glucose or other markers is mixed. Hypoglycemia was reported by one subject in a clinical trial (76). In human research, caffeine or green tea was shown to modulate blood sugar levels and affect levels of insulin and insulin resistance (203; 132), and EGCG decreased blood glucose and/or insulin in animal (204) and human research (205). However, in patients without diabetes, plasma glucose levels were higher two hours following ingestion of a meal, when the meal was consumed with green tea vs. water (99). Also, preliminary research suggests that green tea lacks an effect on blood sugar or insulin levels in many individuals (152; 76; 134; 151; 163; 132; 136; 129); however, the consumption of green tea was inversely associated with risk for diabetes in epidemiological research (206). Green tea extract decreased streptozotocin-induced increases in blood glucose in rats (100).
  • ImmunomodulatorsImmunomodulators: In human research, increased proliferation of gamma-delta T cells from subjects taking green tea, and secretion of IFN-gamma occurred (69). In isolated CD19+ B cells, EGCG decreased the expression of CD11b and suppressed CD11b-mediated migration and adhesion of B cells to endothelial cells (181).
  • IronIron: In human research, impaired iron metabolism and microcytic anemia occurred in infants (102). In clinical research, in thalassemia major and intermedia patients, tea caused an inhibition of iron absorption (103). Decreased nonheme absorption has been shown in young women consuming foods with green tea added (104). However, it has also been suggested that green tea does not inhibit iron absorption (368; 369). According to a review, it is recommended that vegetarians drink tea between meals, as tea binds to dietary iron found in plant sources and decreases the availability (absorption) of iron (105). In epidemiological review, tea consumption was associated with a reduced iron status only in groups with a high prevalence of deficiency (106). Also, one study included in the review suggested that in middle-aged men at risk of iron overload, tea consumption may lower serum ferritin concentrations.
  • L-theanineL-theanine: Preliminary human research exists on the effects of L-theanine, a predominant amino acid found in green tea, indicating benefits of L-theanine in the treatment of anxiety under specific conditions (338; 215).
  • Lipoic acidLipoic acid: According to a review of cell culture and animal models, lipoic acid may combine synergistically to decrease oxidative stress, inflammation, Abeta levels, and Abeta plaque load when administered with (-)-epigallocatechin gallate (from green tea), and thus may provide a combined benefit in the treatment of Alzheimer's disease (393).
  • Musculoskeletal agentsMusculoskeletal agents: In a clinical trial, oral consumption of EGCG from green tea or a decaffeinated green tea polyphenol mixture for four weeks resulted in mild muscle pain (71). According to secondary sources, green tea, a source of fluoride, may cause skeletal fluorosis.
  • MushroomsMushrooms: Zhang et al. conducted a case-control study to examine the relationship between dietary intake of mushrooms and green tea on the risk of breast cancer in Chinese women (252). A significant effect was observed for the combination of mushroom and green tea intake (p<0.001).
  • N-acetyl cysteineN-acetyl cysteine: In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389).
  • Neurologic agentsNeurologic agents: Theoretically, the caffeine constituent of green tea may cause nervousness, agitation, habituation, and psychological dependence, with withdrawal symptoms. In human research, use of green tea or constituents of green tea, such as caffeine, has resulted in dizziness, headache, and nervous system stimulation resulting in symptoms such as delirium, confusion, restlessness, and insomnia (71; 72; 73; 92; 61; 75; 54; 93; 50). In vitro and in animal research, EGCG exerted neuroprotective effects in models of Alzheimer's and Parkinson diseases (370; 371; 372). In a clinical trial involving EGCG, beneficial effects on cognitive performance, mood, and localized cerebral blood flow were lacking in healthy adults (141); however, EGCG increased alpha, beta, and theta activity, mainly in the frontal and medial frontal gyrus (133) and brain theta waves in the temporal, frontal, parietal, and occipital areas (373).
  • Omega-3Omega-3: In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • OnionOnion: In animal research, EGCG when administered as part of a nutrient mixture containing quercetin, increased EGCG levels in plasma vs. EGCG alone (394). The plasma C(max) was raised from 55.29 ? 1.70 to 61.94 ? 1.70ng/mL and 94.44 ? 1.59ng/mL, respectively, and the area under the curve over 24 hours increased. In human research, red onion (containing quercetin) increased plasma levels of EGCG.
  • Ophthalmic agentsOphthalmic agents: Watery and puffy eyes were reported by one subject in a clinical trial (69). In a clinical trial of oral green tea polyphenols (GTPs), retinal detachment occurred six months into the study; however, it was uncertain whether this was related to the study agent (94).
  • Osteoporosis agentsOsteoporosis agents: Using bone biomarkers, green tea polyphenols appear to offer benefit for bone health (142) and may be safe and possibly improve quality of life in osteopenic women (91); however, clinical evidence on bone mass is lacking.
  • P-glycoprotein modulatorsP-glycoprotein modulators: The involvement of green tea in p-glycoprotein regulation has been reviewed (374; 37). In vitro, green tea polyphenols inhibited p-glycoprotein activity (120; 121). In human research, it was determined that among patients with cancer, green tea was included as an herbal remedy most often used that had potential interactions with the chemotherapy they were also receiving due to similar metabolism via cytochrome P450-metabolizing enzymes (CYPs) and/or the p-glycoprotein (P-gp) transporter (35).
  • ProbioticsProbiotics: In human research, consumption of a yogurt containing Bifidobacterium animalis subsp. lactis BB-12 and Lactobacillus acidophilus LA-5, as well as green tea extract, increased specific fecal probiotic levels (395). The effect of green tea itself is not clear.
  • QuercetinQuercetin: In human research, a combination of quercetin, isoquercetin, vitamin C, omega-3 fatty acids, and EGCG increased levels of plasma quercetin (396). In animal research, EGCG when administered as part of a nutrient mixture containing quercetin, increased EGCG levels in plasma vs. EGCG alone (394). The plasma C(max) was raised from 55.29 ? 1.70 to 61.94 ? 1.70ng/mL and 94.44 ? 1.59ng/mL, respectively, and the area under the curve over 24 hours increased. In human research, red onion (containing quercetin) increased plasma levels of EGCG.
  • Renal agentsRenal agents: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • Renally eliminated agentsRenally eliminated agents: Green tea containing caffeine may produce a diuretic effect. Dysuria has been reported in secondary sources.
  • Respiratory agentsRespiratory agents: Exposure to green tea dust has been suggested as increasing symptoms of asthma in some individuals (95), and green tea has also been suggested as inducing asthma (96). In a case report, hypersensitivity pneumonitis was associated with inhalation of catechin-rich green tea extracts (98). A 67 year-old woman, who for 15 years used infusions of green tea to wash her nasal cavities, was diagnosed with granulomatous alveolitis with lymph follicles (97). Green tea consumption was associated with a lower risk of death from pneumonia in women in epidemiological research (375); however, green tea was less effective than CYSTUS052? for upper respiratory tract symptoms (54).
  • ResveratrolResveratrol: In vitro, resveratrol and EGCG inhibited angiogenesis in endometrial tumors (397). In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Seizure threshold-lowering agentsSeizure threshold-lowering agents: In a case report, seizure activity and unresponsiveness were suggested to be due to Hydroxycut? ingestion; the role of green tea is unclear as the formulation of Hydroxycut? has changed over the years (112).
  • SeleniumSelenium: In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389).
  • Sulfotransferase 1A3 (SULT1A3) substratesSulfotransferase 1A3 (SULT1A3) substrates: In vitro, green tea inhibited the sulfation of dopamine and ritodrine, two substrates of SULT1A3 (376).
  • TanninsTannins: In human and animal research, tannins from tea have been linked to a high rate of esophageal cancer in regions of heavy tea consumption, although other studies suggest a protective effect of green tea in relation to esophageal cancer (124; 125). Caution is advised with concomitant use of other tannin-containing herbs and supplements.
  • TobaccoTobacco: Additive effects on cardiovascular parameters may occur with nicotine (57). In a systematic review and meta-analysis, a subgroup analysis found a potential interaction with green tea and smoking that produced a moderate increased risk of bladder cancer (242).
  • Tomato extractTomato extract: In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation all improved.
  • VasoconstrictorsVasoconstrictors: In clinical research of endothelial function in patients with chronic renal failure, green tea significantly improved flow-mediated dilation (353).
  • VasodilatorsVasodilators: In clinical research of endothelial function in patients with chronic renal failure, green tea significantly improved flow-mediated dilation (353).
  • Vitamin CVitamin C: In human research, single doses of tea catechins decreased ascorbate levels briefly (122); however, effects of green tea extract on ascorbic acid levels were lacking in a separate study (123). In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389). In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Vitamin EVitamin E: In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Vitamin KVitamin K: In human research, large amounts (one-half to one gallon) of green tea antagonized the effects of an anticoagulant, particularly Coumadin? therapy, possibly due to the small amounts of vitamin K in green tea (109; 110). Dry green tea leaves contain significantly more vitamin K than black tea leaves; green tea may contain 1,428mcg of vitamin K per 100g of leaf, while black tea may contain only 262mcg of vitamin K per 100g of leaf (111).
  • Wound-healing agentsWound-healing agents: EGCG has been shown to affect the role that TGF-beta1 plays in fibroblast populated collagen gel contraction, an effect that is possibly mediated through myofibroblast differentiation and connective tissue growth factor gene expression (379). Additional details, however, are lacking.
  • Yerba mateYerba mate: Theoretically, caffeine from green tea may add to the effects of caffeine from yerba mate.
  • Zizyphus jujubeZizyphus jujube: In vitro, a combination of Zizyphus jujube and green tea extracts had cytotoxic activity in HepG2 cells (398).

    • Green tea/Food Interactions:

  • GeneralGeneral: This section focuses on potential interactions with green tea. Most food interactions associated with green tea are predominantly theoretical and generally based on the adverse effect profile of caffeine. For more potential interactions based on caffeine itself, the Natural Standard monograph on caffeine is available.
  • Ascorbic acid-containing foodsAscorbic acid-containing foods: In human research, single doses of tea catechins decreased ascorbate levels briefly (122); however, effects of green tea extract on ascorbic acid levels were lacking in a separate study (123). In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389). In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation all improved.
  • BreadBread: In human research, modification of the absorption, metabolism, and excretion of flavan-3-ols was lacking during coingestion of the green tea extract, Polyphenon E?, with bread (399).
  • Caffeinecontaining foodsCaffeine-containing foods: Green tea is a source of caffeine. Theoretically, there may be additive side effects with other products containing caffeine. A combination product containing bitter orange, caffeine, and green tea lacked an effect on heart rate or blood pressure (341).
  • CatechinsCatechins: Theoretically, the bioavailability of catechins, constituents of green tea, may decrease when ingested with food.
  • CheeseCheese: In human research, modification of the absorption, metabolism, and excretion of flavan-3-ols was lacking during coingestion of the green tea extract, Polyphenon E?, with cheese (399).
  • CitrusCitrus: In epidemiological research, reduced cancer incidence in individuals consuming citrus was further reduced in individuals also consuming green tea (391).
  • Folic acid-containing foodsFolic acid-containing foods: In human research, researchers noted that a potential interaction may exist between tea and folic acid, with even low concentrations (0.3g of extract/250mL) of green and black tea extracts yielding decreased bioavailabilities of folic acid (115). In vitro (114) and in humans (115), tea components decreased folic acid bioavailability.
  • Grapefruit juiceGrapefruit juice: Theoretically, concomitant administration of green tea with grapefruit juice may increase caffeine levels and the risk of adverse effects.
  • GrapeGrape: In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389).
  • Iron-containing foodsIron-containing foods: In human research, impaired iron metabolism and microcytic anemia occurred in infants (102). In clinical research, in thalassemia major and intermedia patients, tea caused an inhibition of iron absorption (103). Decreased nonheme absorption has been shown in young women consuming foods with green tea added (104). However, it has also been suggested that green tea does not inhibit iron absorption (368; 369). According to a review, it is recommended that vegetarians drink tea between meals, as tea binds to dietary iron found in plant sources and decreases the availability (absorption) of iron (105). In an epidemiological review, tea consumption was associated with a reduced iron status only in groups with a high prevalence of deficiency (106). Also, one study included in the review suggested that in middle-aged men at risk of iron overload, tea consumption may lower serum ferritin concentrations.
  • L-theanine-containing foodsL-theanine-containing foods: Preliminary human research exists on the effects of L-theanine, a predominant amino acid found in green tea, indicating benefits of L-theanine in the treatment of anxiety under specific conditions (338; 215).
  • MilkMilk: Milk does not reduce polyphenol bioavailability. Polyphenols have a strong affinity for proline rich proteins (casein, milk, gelatin, saliva). However, the addition of milk to green or black tea does not appear to affect the polyphenol concentration in blood (386; 400; 303; 105). Some studies have found the tannin component to be protein bound by adding milk, thereby preventing its potential detrimental effects (386), although other studies present conflicting results (401; 303). In human research, the addition of milk to green tea inhibited the effect of green tea on diet-induced thermogenesis (402).
  • MushroomsMushrooms: Zhang et al. conducted a case-control study to examine the relationship between dietary intakes of mushrooms and green tea on the risk of breast cancer in Chinese women (252). A significant effect was observed for the combination of mushroom and green tea intake (p<0.001).
  • Omega-3-containing foodsOmega-3-containing foods: In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Probiotic-containing foodsProbiotic-containing foods: In human research, consumption of a yogurt containing Bifidobacterium animalis subsp. lactis BB-12 and Lactobacillus acidophilus LA-5, as well as green tea extract, increased specific fecal probiotic levels (395). The effect of green tea itself is not clear.
  • Quercetin-containing foodsQuercetin-containing foods: In human research, a combination of quercetin, isoquercetin, vitamin C, omega-3 fatty acids, and EGCG increased levels of plasma quercetin (396). In animal research, EGCG, when administered as part of a nutrient mixture containing quercetin, increased EGCG levels in plasma vs. EGCG alone (394). The plasma C(max) was raised from 55.29 ? 1.70 to 61.94 ? 1.70ng/mL and 94.44 ? 1.59ng/mL, respectively, and the area under the curve over 24 hours increased. In human research, red onion (containing quercetin) increased plasma levels of EGCG.
  • Red onionRed onion: In animal research, EGCG, when administered as part of a nutrient mixture containing quercetin, increased EGCG levels in plasma vs. EGCG alone (394). The plasma C(max) was raised from 55.29 ? 1.70 to 61.94 ? 1.70ng/mL and 94.44 ? 1.59ng/mL, respectively, and the area under the curve over 24 hours increased. In human research, red onion (containing quercetin) increased plasma levels of EGCG.
  • Resveratrol-containing foodsResveratrol-containing foods: In vitro, resveratrol and EGCG inhibited angiogenesis in endometrial tumors (397). In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Selenium-containing foodsSelenium-containing foods: In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389).
  • Tannin-containing foodsTannin-containing foods: There is evidence that tannins in tea are linked to a high rate of esophageal cancer in regions of heavy tea consumption, although other studies suggest a protective effect of green tea in relation to esophageal cancer (124; 125).
  • TomatoesTomatoes: In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Vitamin C-containing foodsVitamin C-containing foods: In human research, single doses of tea catechins decreased ascorbate levels briefly (122); however, effects of green tea extract on ascorbic acid levels were lacking in a separate study (123). In a crossover study, supplementation with a nutrient mixture normally prescribed to cancer patients containing ascorbic acid, selenium, N-acetyl cysteine, black grapes, and other nutrients resulted in an increase of systemic availability of EGCG by 27% (389). In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Vitamin E-containing foodsVitamin E-containing foods: In human research, a dietary mix containing resveratrol, green tea extract, alpha-tocopherol, vitamin C, omega-3 fatty acids, and tomato extract modulated inflammation and reduced oxidative and metabolic stress (390). The authors suggested that plasma adiponectin concentrations increased by 7% and that effects on CRP were lacking. Inflammation of adipose tissue, endothelial function, oxidative stress, and liver fatty acid oxidation were all improved.
  • Vitamin K-containing foodsVitamin K-containing foods: In human research, large amounts (one-half to one gallon) of green tea antagonized the effects of an anticoagulant, particularly Coumadin? therapy, possibly due to the small amounts of vitamin K in green tea (109; 110). Dry green tea leaves contain significantly more vitamin K than black tea leaves; green tea may contain 1,428mcg of vitamin K per 100g of leaf, while black tea may contain only 262mcg of vitamin K per 100g of leaf (111).

    • Green tea/Lab Interactions:

  • GeneralGeneral: This section focuses on potential interactions with green tea. Most lab interactions associated with green tea are predominantly theoretical and generally based on the adverse effect profile of caffeine. For more potential interactions based on caffeine itself, the Natural Standard monograph on caffeine is available.
  • Ascorbic acidAscorbic acid: In human research, single doses of tea catechins decreased ascorbate levels briefly (122); however, effects of green tea extract on ascorbic acid levels were lacking in a separate study (123).
  • AdiponectinAdiponectin: In epidemiological research, green tea consumption was not significantly associated with adiponectin levels (403).
  • Blood pressureBlood pressure: In clinical research, green tea (49) and green tea extracts (50), increased systolic and diastolic blood pressure. Increases in blood pressure have been shown in further human research (51; 52; 53). However, there is controversy in this area, and several clinical trials have not shown these effects (209; 210; 211; 212; 213; 129) or have demonstrated blood pressure-lowering effects (160; 132), including one case of hypotension (54). In epidemiological research, habitual tea drinking, including green tea, reduced the prevalence of developing hypertension (214). In clinical research, L-theanine, a constituent of green tea, inhibited the increases in blood pressure observed in the high-response group (individuals whose blood pressure increased more than average during the mental task and after placebo intake) (215).
  • Body weightBody weight: There are mixed results concerning the effect of green tea on obesity (161; 160; 329; 136; 137; 135; 134; 129; 77), although endpoints lack consistency and a meta-analysis suggested a lack of effect on weight loss or weight maintenance (53), and in a separate analysis, effects were small when caffeine was included (165).
  • Coagulation panelCoagulation panel: In in vitro and animal research, both catechins and caffeine in green tea exhibited antiplatelet activity (14; 15). In one case report, large amounts (one-half to one gallon) of green tea antagonized the effects of warfarin, possibly due to the small amounts of vitamin K in green tea (109; 110). In laboratory research, dry green tea leaves contained significantly more vitamin K than black tea leaves; green tea may contain 1,428mcg of vitamin K per 100g of leaf, while black tea may contain only 262mcg of vitamin K per 100g of leaf (111). Suboptimal anticoagulation control with warfarin was documented in patients that used common herbs (garlic, ginger, green tea, papaya) at least four times weekly (201). In a clinical trial, consumption of green tea did not inhibit platelet aggregation (202).
  • C-reactive protein (CRP)C-reactive protein (CRP): In human research, green tea, alone or in combination products, reduced or lacked effects on CRP (128; 150; 132; 390).
  • Creatine kinaseCreatine kinase: In human research, green tea extract prevented a rise in plasma creatine kinase activity seen in the placebo group following exercise (339).
  • CytokinesCytokines: In human research, green tea reduced interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha levels (150; 132).
  • ElectrolytesElectrolytes: According to secondary sources, green tea containing caffeine may produce a diuretic effect.
  • Exercise stress testExercise stress test: According to a review, most patients know to avoid tea prior to a pharmacologic or exercise stress test (404).
  • Folic acidFolic acid: In animal research, green tea extracts at very high dietary concentrations lowered serum folate in rats; however, similar effects were not observed in humans (405).
  • GlucoseGlucose: From available laboratory and human research, the effect of green tea or its constituents on blood glucose or other markers is mixed. Hypoglycemia was reported by one subject in a clinical trial (76). In human research, caffeine or green tea was shown to modulate blood sugar levels and affect levels of insulin and insulin resistance (203; 132), and EGCG decreased blood glucose and/or insulin in animal (204) and human research (205). However, in patients without diabetes, plasma glucose levels were higher two hours following ingestion of a meal, when the meal was consumed with green tea vs. water (99). Also, preliminary research suggests that green tea lacks an effect on blood sugar or insulin levels in many individuals (152; 76; 134; 151; 163; 132; 136; 129); however, the consumption of green tea was inversely associated with risk for diabetes in epidemiological research (206). Green tea extract decreased streptozotocin-induced increases in blood glucose in rats (100).
  • Heart rateHeart rate: In human research, EGCG decreased heart rate during rest; however, effects were lacking during exercise (145). Effects of green tea, alone or in combination with other agents, were lacking in other human research (134; 341). In a case report, the EGCG component of Hydroxycut? was thought to be responsible for atrial fibrillation (55).
  • Hemostatic factorsHemostatic factors: In human research, relative to cocoa, green tea decreased concentrations of fibrinogen (406).
  • HormonesHormones: Epidemiological research suggests a relationship between green tea consumption and decreased estrogen levels in humans (113). In animal research, green tea reduced blood levels of testosterone, estradiol, leptin, luteinizing hormone, and insulin-like growth factor (204); however, in human research, Polyphenon E? lacked consistent effects on testosterone, estradiol, and estrone levels (205).
  • Immune panelImmune panel: In human research, increased proliferation of gamma-delta T cells from subjects taking green tea, and secretion of IFN-gamma occurred (69). In isolated CD19+ B cells, EGCG decreased the expression of CD11b and suppressed CD11b-mediated migration and adhesion of B cells to endothelial cells (181).
  • Iron statusIron status: In human research, impaired iron metabolism and microcytic anemia occurred in infants (102). In clinical research, in thalassemia major and intermedia patients, tea caused an inhibition of iron absorption (103). Decreased nonheme absorption has been shown in young women consuming foods with green tea added (104). However, it has also been suggested that green tea does not inhibit iron absorption (368; 369). According to a review, it is recommended that vegetarians drink tea between meals, as tea binds to dietary iron found in plant sources and decreases the availability (absorption) of iron (105). In epidemiological review, tea consumption was associated with a reduced iron status only in groups with a high prevalence of deficiency (106). Also, one study included in the review suggested that in middle-aged men at risk of iron overload, tea consumption may lower serum ferritin concentrations.
  • Lipid profileLipid profile: Research available in systematic reviews and meta-analysis suggests that green tea has beneficial effects on blood lipids (158; 157; 66; 131); however, studies in patients with hyperlipidemia are limited. Also, in vitro (17), animal (216; 204), and human (217; 218; 77; 155; 159; 219; 157; 66; 158; 220; 205; 131; 132; 136; 135; 221) studies have demonstrated the antilipemic effects of green tea and green tea catechins. Most commonly, total cholesterol was reduced, although responses of LDL cholesterol and triglycerides (decrease) and HDL cholesterol (increase) varied between studies. A lack of effect on lipid profiles, however, has also been reported in human trials using green tea (222; 123; 129). In humans, theaflavin-enriched green tea decreased levels of total and LDL cholesterol (155).
  • Liver function testsLiver function tests: According to various case reports and a review, hepatotoxicity (80; 81; 82; 83; 27) and acute or fulminant hepatitis (84; 85; 86; 87; 88; 89) have been associated with use of green tea products. In clinical trials, slightly elevated alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) occurred (relationship to green tea or constituents unclear) (90; 91). However, one systematic review found that an increased consumption of green tea may reduce the risk of liver disease (366), and in a clinical trial, an increased consumption of green tea, especially more than 10 cups daily, was related to decreased concentrations of hepatological markers in serum, AST (p=0.06), ALT (p=0.07), and ferritin (p=0.02), indicating that green tea may act protectively against disorders of the liver (367). In human research, green tea or its constituents lacked effect on AST, ALT, or blood urea nitrogen (BUN) (91).
  • QuercetinQuercetin: In human research, a combination of quercetin, isoquercetin, vitamin C, omega-3 fatty acids, and EGCG increased levels of plasma quercetin (396). In animal research, EGCG, when administered as part of a nutrient mixture containing quercetin, increased EGCG levels in plasma vs. EGCG alone (394). The plasma C(max) was raised from 55.29 ? 1.70 to 61.94 ? 1.70ng/mL and 94.44 ? 1.59ng/mL, respectively, and the area under the curve over 24 hours increased. In human research, red onion (containing quercetin) increased plasma levels of EGCG.
  • Serum amyloid alpha (SAA)Serum amyloid alpha (SAA): In human research, green tea reduced plasma levels of SAA (128).
  • Skin elastinSkin elastin: In human research, green tea improved levels of skin elastin (67).
  • UrinalysisUrinalysis: According to human evidence, consumption of tea, which contains large amounts of ascorbic acid, may induce a false negative result during occult blood and sugar tests with urinalysis reagent strips (407). In one case, green tea containing 250mg of ascorbic acid per 100g of tea induced transient acceleration of intravascular hemolysis in a 67 year-old man with paroxysmal nocturnal hemoglobinuria (107).