Black tea,green tea,and tea polyphenols

Previous studies have shown that tea consumption can impair trace element metabolism, particularly iron status, and increase the risk of anemia in humans and animals. More recently, however, evidence has been accumulating to show that, in animals, consumption of green tea or its polyphenols is associated with a reduction of the incidence and severity of a variety of experimentally induced cancers. In this study we have monitored the growth, trace element status, including hematological parameters of weanling rats given either (1) water, (2) 1% black tea, (3) 1% green, tea, or (4) 0.2% crude green tea extract as their sole drinking fluid while consuming diets containing either adequate or low amounts of iron. With the exception of manaanese, none of the trace elements studied (iron, copper, zinc, and manganese) or the hematological indices measured were affected by the type of beverage supplied, even though the polyphenol extract was shown to chelate metals in vitro and all the animals fed the low iron diet were shown to be anemic. There appeared to be an effect of black and green teas on manganese balance in, both the first and last weeks of the study. A lower level of brain managanese was associated with green tea consumption, and a higher level of this element in the kidneys of animals fed black tea. The results demonstrate that both black and green teas and a green tea polyphenol extract do not represent a risk to animals consuming the beverages as their sole fluid intake with respect to iron availability, although the interactions with manganese deserve further study.     

The prevention of lung cancer induced by a tobacco-specific carcinogen in rodents by green and black Tea

A growing body of evidence from studies in laboratory animals indicates that green tea protects against cancer development at various organ sites. We have previously shown that green tea, administered as drinking water, inhibits lung tumor development in A/J mice treated with 4-(methylnitrosamino)-1-(3-pyridyl)-l-butanone (NNK), a potent nicotine-derived lung carcinogen found in tobacco. The inhibitory effect of green tea has been attributed to its major polyphenolic compound, epigallocatechin gallate (EGCG), and, to a lesser extent, to caffeine. We have also demonstrated that while levels of O6-methylguanine, a critical lesion in NNK lung tumorigenesis, were not affected in lung DNA. However, the levels of 8-hydroxydeoxyguanosine (8-OH-dG), a marker of oxidative DNA damage, were significantly suppressed in mice treated with green tea or EGCG. These studies underscore the importance of the antioxidant activity of green tea and EGCG for their inhibitory activity against lung tumorigenesis. Unlike green tea, the effect of black tea on carcinogenesis has been scarcely studied, even though the worldwide production and consumption of black tea far exceeds that of green tea. The oxidation products found in black tea, thearubigins and theaflavins, also possess antioxidant activity, suggesting that black tea may also inhibit NNK-induced lung tumorigenesis. Indeed, bioassays in A/J mice have shown that black tea given as drinking water retarded the development of lung cancer caused by NNK. However, data on the relationship of black tea consumption with the lung cancer risk in humans are limited and inconclusive. There is a need for additional tumor bioassays in animal models to better examine the protective role of black tea against lung cancer. The development of adenocarcinomas and adenosquamous carcinomas in F344 rats upon chronic administration of NNK provides an important and relevant model for lung carcinogenesis in smokers. Thus far, no information was previously available regarding the effects of tea on this model. We conducted a 2-year lifetime bioassay in F344 rats to determine whether black tea and caffeine are protective against lung tumorigenesis induced by NNK. Our studies in both mice and rats have generated important new data that support green and black tea and caffeine as potential preventive agents against lung cancer, suggesting that a closer examination of the roles of tea and caffeine on lung cancer in smokers may be warranted.     

Comparative antimutagenic and anticlastogenic effects of green tea and black tea: a review

Tea is the most popular beverage next to water, consumed by over two-thirds of the world's population. It is processed in different ways in different parts of the world to give green, black or oolong tea. Experimental studies have demonstrated the significant antimutagenic and anticlastogenic effects of both green and black tea and its polyphenols in multiple mutational assays. In the present review, we have attempted to evaluate and update the comparative antimutagenic and anticlastogenic effects of green tea, black tea and their polyphenols in different test systems, based on available literature. Existing reports have suggested that the protective effects of black tea is as good as green tea, however, more studies on black tea and its polyphenols are needed before a final conclusion can be made.     

Extraction behavior of caffeine and EGCG from green and black tea

A dipping method was developed to extract the catechins (EGCG) and alkaloids (caffeine) from green tea (Korea) and black tea (Sri Lanka). The effects of the solvent composition (water vs. ethanol), extraction time, temperatures, and solvent pH on the amount of catechins (EGCG) and alkaloids (caffeine) extracted from green and black tea were investigated. Reversedphase high-performance liquid chromatography (RP-HPLC) was used to analyze the catechins (EGCG) and alkaloids (caffeine) extracted. The content of EGCG and caffeine in green tea extracts was in the range of 2.04∼0.30 and 10.22∼0.85 mg/g, respectively. The amount of EGCG and caffeine in black tea extracts was in the range of 0.32∼0.24 and 5.26∼1.01 mg/g, respectively. The amount of caffeine extracted from green and black tea was greater than the amount of EGCG. Pure water is the best solvent for extracting EGCG and caffeine from green tea. The amount of caffeine extracted from green and black tea increased as the temperature, extraction time, and hydrogen ion concentration of the solvent increased. Although the amount of EGCG extracted from green tea increased as the temperature increased, the amount of EGCG extracted from black tea was not affected by temperature. The extraction of EGCG from both green and black tea was not affected by the hydrogen ion concentration of the solvent.     

Iron bioavailability and weight gains to iron-deficient rats fed a commonly consumed tunisian meal ‘bean seeds ragout’ with or without beef and with green or black tea decoction

The Fe bioavailability and the weight gains were evaluated in rats fed a commonly consumed Tunisian meal 'bean seeds ragout' (BSR), with or without beef and with black or green tea decoction. The Fe bioavailability was evaluated in Fe-deficient rats by the hemoglobin repletion method and the Fe stored in the liver. The addition of beef to the BSR significantly increased the Fe bioavailability from this meal by 147% and the reserve of Fe stored in the liver by 77% (P < 0.001). In contrast, both black and green tea decoctions caused a significant decrease of the Fe bioavailability from BSR meal (-19.6 +/- 4.9% and -14.9 +/- 4.1%, respectively). The reserve of Fe stored in the liver was significantly lower in the BSR, the black and the green tea groups than in the positive control group (FeSO4). The weight gains were significantly lower in the black and the green tea groups (3.9 +/- 5.7 g, 13 +/- 1.9 g, respectively) than in the BSR group (24.9 +/- 6 g). The addition of beef to BSR meal counteracted the inhibitory effect of the kidney bean and considerably improved the Fe bioavailability and the Fe stored in the liver of rats. The green tea decoction, which constitutes an important source of antioxidant factors, had the same inhibitory effect as the black tea decoction on the Fe bioavailability from BSR meal. In addition, both black and green teas significantly reduced the weight gains, where the black tea decoction has the most effect.     

Consumption of tea modulates the urinary excretion of mutagens in rats treated with IQ. Role of caffeine.

The present study was undertaken to investigate whether the consumption of green tea and black tea influences the excretion of mutagens and promutagens in rats treated orally with the food carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Rats were maintained on aqueous extracts (2.5%, w/v) of green tea, black tea or decaffeinated black tea as their sole drinking liquid. After 4 weeks, the animals received, by gastric intubation, a single dose of IQ (5 mg/kg), and urine was collected for 48 h. Direct and indirect mutagenicity, in the presence of an activation system derived from Aroclor 1254-treated rats, was determined in the urine samples using the Ames mutagenicity assay. Consumption of green tea and black tea, but not of decaffeinated black tea, markedly decreased the urinary excretion of mutagens and promutagens. In a further study, supplementation of decaffeinated black tea with caffeine suppressed the excretion of mutagens and promutagens in the urine of rats pretreated with IQ. It is concluded that both green tea and black tea modulate the bioactivation and metabolism of IQ, and that caffeine is largely responsible for this effect.     

Inhibition of human LDL lipid peroxidation by phenol-rich beverages and their impact on plasma total antioxidant capacity in humans

Mounting evidence shows that phenol-rich beverages exert strong antioxidant activity. However, in vivo evidence has produced conflicting results. In the present study, we studied the impact of the ingestion of 300 mL of black and green tea, alcohol-free red wine, alcohol-free white wine, or water on plasma total antioxidant capacity in five healthy volunteers. Red wine has the highest content of phenolics (3.63 +/- 0.48 g QE/L), followed by green tea (2.82 +/- 0.07 g QE/L), black tea (1.37 +/- 0.15 g QE/L), and white wine (0.31 +/- 0.01 g QE/L). Plasma total antioxidant capacity values of subjects who drank green tea rose at 30 min (P < 0.05). After black tea and red wine ingestion, the peaks were at 50 min (P < 0.05 and P < 0.01, respectively). No changes were observed in the control and white wine groups. Red wine and green tea were the most efficient in protecting low density lipoprotein from oxidation driven by peroxyl and ferril radicals, respectively. Phenol-rich beverages are a natural source of antioxidants; however, the phenolic content alone cannot be considered an index of their in vivo antioxidant activity.     

Green and black tea extracts inhibit HMG-CoA reductase and activate AMP kinase to decrease cholesterol synthesis in hepatoma cells

Recent studies have demonstrated that green and black tea consumption can lower serum cholesterol in animals and in man, and suppression of hepatic cholesterol synthesis is suggested to contribute to this effect. To evaluate this hypothesis, we measured cholesterol synthesis in cultured rat hepatoma cells in the presence of green and black tea extracts and selected components. Green and black tea decreased cholesterol synthesis by up to 55% and 78%, respectively, as measured by a 3-h incorporation of radiolabeled acetate. Inhibition was much less evident when radiolabeled mevalonate was used, suggesting that the inhibition was mediated largely at or above the level of HMG-CoA reductase. Both extracts directly inhibited HMG-CoA reductase when added to microsomal preparations, although the extent of inhibition was considerably less than the decrease in cholesterol synthesis observed in whole cells. As HMG-CoA reductase activity also can be decreased by enzyme phosphorylation by AMP kinase, the phosphorylation state of HMG-CoA reductase and AMP kinase, which is activated by phosphorylation, was determined in lysates from cells treated with tea extracts. Both extracts increased AMP-kinase phosphorylation and HMG-CoA reductase phosphorylation by 2.5- to 4-fold, but with different time courses: maximal phosphorylation with green tea was evident within 30 min of treatment, whereas with black tea phosphorylation was slower to develop, with maximal phosphorylation occurring > or =3 hours after treatment. These results suggest that both green and black tea decrease cholesterol synthesis in whole cells by directly inhibiting HMG-CoA reductase and by promoting its inactivation by AMP kinase.     

Green, oolong and black tea extracts modulate lipid metabolism in hyperlipidemia rats fed high-sucrose diet

The main goal of this study was to compare effects of ethanol-soluble fractions prepared from various types of teas on sucrose-induced hyperlipidemia in 5-week old male Sprague-Dawley rats. Rats (n = 6-8 per group) weighed approximately 200 g were randomly divided into control diet, sucrose-rich diet, green tea, oolong tea and black tea groups. Control-diet group was provided with modified AIN-93 diet while the others consumed sucrose-rich diet. Tea extracts (1% w/v) were supplied in the drink for green tea, oolong tea and black tea groups. Results indicated sucrose-rich diet induced hypertriglyceridemia and hypercholesterolemia. Food intake was reduced by oolong tea extract. Consuming oolong and black tea extracts also significantly decreased body weight gains and food efficiency. Hypertriglyceridemia was normalized by green and black tea drink on day 18 and by oolong tea extract on day 25, respectively. Hypercholesterolemia was normalized by green tea on day 18 and by oolong tea and black tea on day 25, respectively. Plasma HDL-cholesterol concentrations were not affected by any tea extract. The triglyeride content in the liver as well as the cholesterol content in the heart of rats fed sucrose-rich diet were elevated and were normalized by all types of tea drink tested. Although green and oolong tea extracts contained similar composition of catechin, our findings suggest green tea exerted greater antihyperlipidemic effect than oolong tea. Apparent fat absorption may be one of the mechanisms by which green tea reduced hyperlipidemia as well as fat storage in the liver and heart of rats consumed sucrose-rich diet.     

茶叶加工中的外源酶研究进展

从应用于茶叶加工中的外源酶种类,来源,作用机理及其在红茶,绿茶,黑茶,茶饮料,速溶茶的加工和检测上的应用等方面综述了近半个世纪以来茶叶加工中的外源酶研究成果与进展,并对外源酶在茶叶加工中的应用提出了思考与展望。     

Inhibitory effect of green and black tea on tumor growth

The administration of green tea, black tea, or (-)-epigallocatechin gallate inhibited the growth of established nonmalignant and malignant tumors in tumor-bearing mice. In experiments with black tea, we found that its oral administration inhibited DNA synthesis and enhanced apoptosis in both nonmalignant and malignant tumors in tumor-bearing mice.     

Scavenging of hydrogen peroxide and inhibition of ultraviolet light-induced oxidative DNA damage by aqueous extracts from green and black teas

Aqueous extracts of green and black teas have been shown to inhibit a variety of experimentally induced animal tumors, particularly ultraviolet (UV) B light-induced skin carcinogenesis. In the present study, we compared the effects of different extractable fractions of green and black teas on scavenging hydrogen peroxide (H2O2), and UV irradiation-induced formation of 8-hydroxy 2'-deoxyguanosine (8-OHdG) in vitro. Green and black teas have been extracted by serial chloroform, ethyl acetate and n-butanol, and divided into four subfractions designated as GT1-4 for green tea and BT1-4 for black tea, respectively. The total extracts from green and black teas exhibited a potent scavenging capacity of exogenous H2O2 in a dose-dependent manner. It appeared that the total extracts from black tea scavenged H2O2 more potently than those from green tea. When tested individually, the potency of scavenging H2O2 by green tea subfractions was: GT2 > GT3 > GT1 > GT4, whereas the order of efficacy for black tea was: BT2 > BT3 > BT4 > BT1. In addition, we demonstrated that total fractions of green and black teas substantially inhibited the induction of 8-OHdG in calf thymus by all three portions of UV spectrum (UVA, B and C). Consistent with the capacity of scavenging H2O2, the subfractions from black tea showed a greater inhibition of UV-induced 8-OHdG than those from green tea. At low concentrations, the order of potency of quenching of 8-OHdG by green tea subfractions was: GT2 > GT3 > GT4 > GT1 and the efficacy of all subfractions became similar at high concentrations. All subfractions of the black tea except BT1 strongly inhibited UV-induced 8-OHdG and the order of potency was: BT2 > BT3 > BT4 > BT1. Addition of (-)-epigallocatechin gallate (EGCG), an ingredient of green tea extract, to low concentration of green and black tea extracts substantially enhanced the scavenging of H2O2 and quenching of 8-OHdG, suggesting the important role of EGCG in the antioxidant activities of tea extracts. The potent scavenging of oxygen species and blocking of UV-induced oxidative DNA damage may, at least in part, explain the mechanism(s) by which green/black teas inhibit photocarcinogenesis.     

Antimutagenic activity of green tea and black tea extracts studied in a dynamic in vitro gastrointestinal model

An in vitro gastrointestinal model, which simulates the conditions in the human digestive tract, was used to determine potential antimutagenic activity of extracts of black tea and green tea. In this paper, results are presented on the availability for absorption of potential antimutagenic compounds present in tea and on the influence of the food matrix on this activity. Between 60 and 180min after the tea was introduced into the model, antimutagenic activity was recovered from the jejunal compartment by means of dialysis: the dialysate appeared to inhibit the mutagenicity of the food mutagen MeIQx in the direct plate assay with Salmonella typhimurium (Ames test). The maximum inhibition was measured at 2h after the start of the experiment and was comparable for black tea and green tea extract. To determine the influence of food matrices on the antimutagenic activity of tea, the model was loaded with black tea together with milk or a homogenized standard breakfast. The maximum inhibition observed with black tea was reduced by 22, 42 and 78% in the presence of whole milk, semi-skimmed milk, and skimmed milk, respectively. Whole milk and skimmed milk abolished the antimutagenic activity of green tea by more than 90%; for semi-skimmed milk the inhibition was more than 60%. When a homogenized breakfast was added into the model together with the black tea extract, the antimutagenic activity was completely eliminated. When tea and MeIQx were added together into the digestion model, MeIQx mutagenicity was efficiently inhibited, with green tea showing a slightly stronger antimutagenic activity than black tea. In this case, the addition of milk had only a small inhibiting effect on the antimutagenicity.Antioxidant capacity and the concentration of catechins were also measured in the jejunal dialysates. The reduction in antimutagenic activity corresponded with reduction in antioxidant capacity and with a decrease of concentration of three catechins, viz. catechin, epigallocatechin gallate and epigallocatechin. The in vitro gastrointestinal model appears to be a useful tool to study the antimutagenicity of food components.     

Tea crude extracts effectively inactivate severe acute respiratory syndrome coronavirus 2

It is well known that black and green tea extracts, particularly polyphenols, have antimicrobial activity against various pathogenic microbes including viruses. However, there is limited data on the antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged rapidly in China in late 2019 and which has been responsible for coronavirus disease 2019 (COVID-19) pandemic globally. In this study, 20 compounds and three extracts were obtained from black and green tea and found that three tea extracts showed significant antiviral activity against SARS-CoV-2, whereby the viral titre decreased about 5 logs TCID₅₀ per ml by 1·375 mg ml⁻¹ black tea extract and two-fold diluted tea bag infusion obtained from black tea when incubated at 25°C for 10 s. However, when concentrations of black and green tea extracts were equally adjusted to 344 µg ml⁻¹, green tea extracts showed more antiviral activity against SARS-CoV-2. This simple and highly respected beverage may be a cheap and widely acceptable means to reduce SARS-CoV-2 viral burden in the mouth and upper gastrointestinal and respiratory tracts in developed as well as developing countries.     

Antimutagenic and anticarcinogenic activity of tea polyphenols

Tea is the most popular beverage, consumed by over two thirds of the world's population. Tea is processed differently in different parts of the world to give green (20%), black (78%) or oolong tea (2%). Green tea is consumed mostly in Japan and China. The antimutagenic and anticarcinogenic activities of green tea are extensively examined. The chemical components of green and black tea are polyphenols, which include EC, ECG, EGC, EGCG and TFs. This article reviews the epidemiological and experimental studies on the antimutagenicity and anticarcinogenicity of tea extracts and tea polyphenols. In Japan, an epidemiological study showed an inverse relationship between habitual green tea drinking and the standardized mortality rates for cancer. Some cohort studies on Chanoyu (Japanese tea ceremony) women teachers also showed that their mortality ratio including deaths caused by malignant neoplasms were surprisingly low. The antimutagenic activity against various mutagens of tea extracts and polyphenols including ECG and EGCG has been demonstrated in microbial systems (Salmonella typhimurium and Escherichia coli), mammalian cell systems and in vivo animal tests. The anticarcinogenic activity of tea phenols has been shown in experimental animals such as rats and mice, in transplantable tumors, carcinogen-induced tumors in digestive organs, mammary glands, hepatocarcinomas, lung cancers, skin tumors, leukemia, tumor promotion and metastasis. The mechanisms of antimutagenesis and anticarcinogenesis of tea polyphenols suggest that the inhibition of tumors may be due to both extracellular and intracellular mechanisms including the modulation of metabolism, blocking or suppression, modulation of DNA replication and repair effects, promotion, inhibition of invasion and metastasis, and induction of novel mechanisms.     

Keemun black tea extract contains potent fatty acid synthase inhibitors and reduces food intake and body weight of rats via oral administration

The inhibitory effects of a black tea extract on fatty acid synthase were measured through inhibition kinetics. The Keemun black tea extract showed more potent inhibitory activity on fatty acid synthase than green tea extract. Additionally, the inhibitory ability of the black tea extract depended on the extracting solvent and the conditions used. Only 10-23% of the inhibitory activity from the black tea was extracted by the general method of boiling with water. The results suggested that the main fatty acid synthase inhibitors in black tea might be theaflavins. Which were more potent than epigallocatechin gallate or C75. The reaction site on the fatty acid synthase and the inhibition kinetics for the extract were different from those of epigallocatechin gallate or C75. In addition, Keemun black tea extract significantly reduced food intake, body weight and blood triglyceride of diet-induced obesity SD rats via oral administration.     

Effects of green, oolong and black teas and related components on the proliferation and invasion of hepatoma cells in culture

The effects of teas and related components on the proliferation and invasion of cancer cells were examined by employing both in vitro proliferation and invasion assay systems. Powdered green, oolong and black tea extracts dose-dependently inhibited proliferation and invasion of a rat ascites hepatoma cell line of AH109A but did not affect the proliferation of the normal mesentery-derived mesothelial cells (M-cells) isolated from rats; higher concentrations of powdered oolong and black teas could restrain the proliferation of another tumor cell line of L929. The AH109A cells were found to penetrate underneath the monolayer of M-cells in the presence of 10% calf serum. When each rat serum obtained at 0.5, 1, 2, 3 and 5 h after oral intubation of each tea extract was added to the culture media instead of calf serum at a concentration of 10%, both the invasion and proliferation of AH109A were significantly suppressed. These ex vivo results suggest the potential bioavailability of effective tea components in rats. Furthermore, (–)-epigallocatechin gallate, (–)-epicatechin gallate and (–)-epigallocatechin from green tea as well as the mixture of theaflavin and theaflavin gallates from black tea were shown to be the most effective components against the invasion and proliferation of AH109A. These results show that the inhibitory effects of the teas and related components against AH109A cells are due to the cell-specific and higher sensitivity of the cell line to tea components. This revised version was published online in August 2006 with corrections to the Cover Date.     

Host suitability of various stored food products for the cigarette beetle, <Emphasis Type="Italic">Lasioderma serricorne</Emphasis> (Coleoptera: Anobiidae)

We investigated the attraction to, and ovipositional activity and egg-to-adult survival rate on, 11 stored products of Lasioderma serricorne (F.). These products included polished rice, unpolished rice, wheat flour, corn flour, cocoa powder, roasted coffee beans, green tea leaves, black tea leaves, soybean flour, flue-cured tobacco leaves, and dried small sardines. Tobacco, cocoa, soybean flour, black tea, and wheat flour significantly attracted the beetles. Corn flour, green tea, and coffee tended to attract the beetles. Ovipositional activity of beetle was higher on the food materials than on nonfood materials. The highest ovipositional activity was observed on coffee, followed by cocoa. Ovipositional activity on black tea, unpolished rice, and green tea was also relatively high. Methanol extracts of coffee beans showed oviposition-stimulatory activity. Therefore, the high ovipositional activity observed on coffee beans could be attributed to oviposition stimulants contained in the beans. In the egg-to-adult survival test, all eggs laid on polished rice or tobacco leaves developed successfully into adults, whereas none of the eggs laid on black tea, green tea, or coffee beans developed into adults. These findings suggest that suitability as an attractive target, suitability as an oviposition site, and suitability as larval food are not always compatible.     

Studies of cocoa tea, a wild tea tree containing theobromine

Camellia ptilophylla Chang is a wild tea tree containing theobromine and is caffeine-flee. Lots of researches have been conducted for its domestication since it was discovered to contain theobromine in its shoots. First, its pharmacological and physiological effects have been studied, demonstrating that it can be used as a new resource of tea as daily and healthy beverage. Cocoa tea differs from traditional tea in that it does not excite the nervous system. Second, various ways of propagation have been investigated, and sexless cutting has been the method adopted currently. Third, through selection and breeding, plantation of cocoa tea can be set up to cultivate new varieties, and cocoa tea of different flavors such as green cocoa tea, oolong cocoa tea, and black cocoa tea can be processed. Thus, cocoa tea will become a choice in the tea market.     

Consumption of Green Tea,but Not Black Tea or Coffee,Is Associated with Reduced Risk of Cognitive Decline

Our objective was to determine whether the consumption of green tea, coffee, or black tea influences the incidence of dementia and mild cognitive impairment (MCI) in older people. We conducted a population-based prospective study with Japanese residents aged >60 years from Nakajima, Japan (the Nakajima Project). Participants received an evaluation of cognitive function and blood tests. The consumption of green tea, coffee, and black tea was also evaluated at baseline. Of 723 participants with normal cognitive function at a baseline survey (2007–2008), 490 completed the follow up survey in 2011–2013. The incidence of dementia during the follow-up period (mean ± SD: 4.9±0.9 years) was 5.3%, and that of MCI was 13.1%. The multiple-adjusted odds ratio for the incidence of overall cognitive decline (dementia or MCI) was 0.32 (95% CI: 0.16–0.64) among individuals who consumed green tea every day and 0.47 (95% CI: 0.25–0.86) among those who consumed green tea 1–6 days per week compared with individuals who did not consume green tea at all. The multiple-adjusted odds ratio for the incidence of dementia was 0.26 (95% CI: 0.06–1.06) among individuals who consumed green tea every day compared with those who did not consume green tea at all. No association was found between coffee or black tea consumption and the incidence of dementia or MCI. Our results indicate that green tea consumption is significantly associated with reduced risk of cognitive decline, even after adjustment for possible confounding factors.