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Is tea a healthy source of hydration?

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Abstract

After water, tea is the most commonly consumed beverage worldwide, with over 80% of adults drinking tea in the UK. Lay concerns about caffeine have led to questions about the suitability of tea as a source of hydration. Several controlled trials have examined the effect of moderate caffeine consumption on fluid balance, from tea or other sources, concluding that intakes of up to 400 mg of caffeine, or six to eight servings of tea daily, are consistent with normal hydration. Unlike water, or other caffeinated beverages, tea is rich in flavonoids: plant compounds associated with health. There is now a growing body of evidence linking regular tea consumption with heart health, cognitive health, dental benefits and bodyweight management suggesting that tea may offer a healthy source of hydration. These studies are discussed in the context of typical tea intakes in the UK.

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... Tea is a popular and widely consumed beverage around the world [1]. In Nigeria, it is a traditional and common beverage taken by most families. ...
... One of the pharmacologically active constituent and quality indicators of tea is caffeine, a methylated xanthine alkaloid structurally identified as 1,3,7-trimethyl xanthine ( Figure 1) [6]. Caffeine is reported to have many beneficial pharmacological effects on the body including antioxidant, antiinflammatory, antimicrobial, anticancer, diuretic properties and lower risk of neurodegenerative diseases development but also not without some attendant risk factors [1,7]. The food based dietary guidelines (FBDG) of Nigeria, in considering dietary caffeine sources, discouraged high tea intake because of inhibition of iron bioavailability and increase phosphorus levels [8]. ...
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Tea is commonly consumed in Nigeria. Caffeine, a major constituent in tea, has some beneficial pharmacological properties, but can negatively affect human health if consumed excessively. The objective of the study was to evaluate some physicochemical properties and caffeine content of teas marketed in FCT, Abuja, Nigeria. Ten commercial brands of teas (8 black teas and 2 green teas) were assessed for weight variation, moisture content and pH tests using standard methods. Extraction of caffeine was carried out and the identity determined by thin layer chromatography and melting points, respectively. High performance liquid chromatography (HPLC) method for analysis of caffeine was developed, validated, and applied to determine caffeine content in the tea brands. Results of the weight, moisture content and pH tests of the samples ranged from 2.07–2.33 g, 5.65–11.0 % and 4.9–5.5, respectively. Caffeine was isolated from all the samples and showed same Rf value (0.46) with that of the reference standard. Melting points ranged from 236.0–238.5 °C. Caffeine content ranged from 12.25–21.76 mg/g for black teas and 13.35–15.05 mg/g for green teas. The study provides information on the stability, acidity and caffeine content in some commercially available tea brands.
... However, we did find among Daasanach that daily milk consumption was associated with lower current thirst, while greater amount of tea/coffee consumption in the prior day was associated with lower pleasantness of drinking water (indicating less of a desire to consume water). Since the tea/coffee they drink is lower in caffeine than in Western settings as it is made with coffee husks, it would not reach the level needed to cause diuresis and serves as an important hydration source (Killer et al., 2014;Ruxton et al., 2015). These findings imply that those specific hydration strategies may be useful to lower thirst and the desire to imbibe water. ...
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... Since tea is important to human life, a vast number of researches have investigated the function of tea. It has been found that tea has beneficial effects on both physical health (Ruxton, Phillips, & Bond, 2015;Shen & Chyu, 2016;Hayat, Iqbal, Malik, Bilal, & Mushtaq, 2015) and cognition (Einöther & Martens, 2013;Dietz & Dekker, 2017;Kuriyama et al., 2006). Recent research for tea's effect on cognition is examining the relationship between drinking tea and creativity (Einöther, Baas, Rowson, & Giesbrecht, 2015). ...
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Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies was asked to deliver a scientific opinion on the safety of caffeine, providing advice on caffeine intakes, from all dietary sources that do not give rise to concerns about adverse health effects for the general healthy population and subgroups thereof. Possible interactions between caffeine and other constituents of so-called “energy drinks”, alcohol, p-synephrine and physical exercise should also be addressed. Single doses of caffeine up to 200 mg (about 3 mg/kg bw for a 70-kg adult) do not give rise to safety concerns. The same amount does not give rise to safety concerns when consumed < 2 hours prior to intense physical exercise under normal environmental conditions. Other constituents of “energy drinks” at typical concentrations in such beverages (about 300–320, 4 000 and 2 400 mg/L of caffeine, taurine and d-glucurono-γ-lactone, respectively), as well as alcohol at doses up to about 0.65 g/kg bw, would not affect the safety of single doses of caffeine up to 200 mg. Habitual caffeine consumption up to 400 mg per day does not give rise to safety concerns for non-pregnant adults. Habitual caffeine consumption up to 200 mg per day by pregnant women does not give rise to safety concerns for the fetus. Single doses of caffeine and habitual caffeine intakes up to 200 mg consumed by lactating women do not give rise to safety concerns for breastfed infants. For children and adolescents, the information available is insufficient to derive a safe caffeine intake. The Panel considers that caffeine intakes of no concern derived for acute caffeine consumption by adults (3 mg/kg bw per day) may serve as a basis to derive single doses of caffeine and daily caffeine intakes of no concern for these population subgroups.
Article
Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) derived Dietary Reference Values (DRVs) for fluoride, which are provided as Adequate Intake (AI) from all sources, including non-dietary sources. Fluoride is not an essential nutrient. Therefore, no Average Requirement for the performance of essential physiological functions can be defined. Nevertheless, the Panel considered that the setting of an AI is appropriate because of the beneficial effects of dietary fluoride on prevention of dental caries. The AI is based on epidemiological studies (performed before the 1970s) showing an inverse relationship between the fluoride concentration of water and caries prevalence. As the basis for defining the AI, estimates of mean fluoride intakes of children via diet and drinking water with fluoride concentrations at which the caries preventive effect approached its maximum whilst the risk of dental fluorosis approached its minimum were chosen. Except for one confirmatory longitudinal study in US children, more recent studies were not taken into account as they did not provide information on total dietary fluoride intake, were potentially confounded by the use of fluoride-containing dental hygiene products, and did not permit a conclusion to be drawn on a dose-response relationship between fluoride intake and caries risk. The AI of fluoride from all sources (including non-dietary sources) is 0.05 mg/kg body weight per day for both children and adults, including pregnant and lactating women. For pregnant and lactating women, the AI is based on the body weight before pregnancy and lactation. Reliable and representative data on the total fluoride intake of the European population are not available.
Article
OBJECTIVE: To examine the association of maternal caffeine intake with fetal growth restriction. DESIGN: Prospective longitudinal observational study. SETTING: Two large UK hospital maternity units. PARTICIPANTS: 2635 low risk pregnant women recruited between 8-12 weeks of pregnancy. Investigations Quantification of total caffeine intake from 4 weeks before conception and throughout pregnancy was undertaken with a validated caffeine assessment tool. Caffeine half life (proxy for clearance) was determined by measuring caffeine in saliva after a caffeine challenge. Smoking and alcohol were assessed by self reported status and by measuring salivary cotinine concentrations. MAIN OUTCOME MEASURES: Fetal growth restriction, as defined by customised birth weight centile, adjusted for alcohol intake and salivary cotinine concentrations. RESULTS: Caffeine consumption throughout pregnancy was associated with an increased risk of fetal growth restriction (odds ratios 1.2 (95% CI 0.9 to 1.6) for 100-199 mg/day, 1.5 (1.1 to 2.1) for 200-299 mg/day, and 1.4 (1.0 to 2.0) for >300 mg/day compared with <100 mg/day; test for trend P<0.001). Mean caffeine consumption decreased in the first trimester and increased in the third. The association between caffeine and fetal growth restriction was stronger in women with a faster compared to a slower caffeine clearance (test for interaction, P=0.06). CONCLUSIONS: Caffeine consumption during pregnancy was associated with an increased risk of fetal growth restriction and this association continued throughout pregnancy. Sensible advice would be to reduce caffeine intake before conception and throughout pregnancy.
Article
There are concerns that tea could provide fluoride (F-) intakes that exceed safe limits. However, F- intakes at the recommended daily allowance (RDA) can support dental health. Benefits and risks were explored in an analysis of UK retail teas. Samples of 49 tea bags and infusions (black blended, speciality/single estate, decaffeinated) were analysed for F-/kg dry weight using an ion selective electrode. Standardised infusions were prepared and analysed as for dry tea. Daily F- from tea was estimated by combining estimated UK tea consumption with F- in black blended tea. Findings showed that mean F-/kg dry weight was 1164 mg black blended, 877 mg speciality and 1464 mg decaffeinated. Infusions contained 4.91 mg/l black blended, 3.0 mg/l speciality and 7 mg/l decaffeinated equating to 0.72–1.68 mg of F- per serving. Based on population means and 95th percentile intakes of tea, including non-consumers, daily F- intakes from tea were less than the RDA and adequate intake (AI) (except for adults with intakes > 95th percentile) but also within age-appropriate tolerable upper intake levels (UL) at both mean and 95th percentile tea intakes. After excluding non-consumers, intakes of F- remained less than UL for all groups except those aged 1.5–3 years or ≥65 years with tea intakes > 95th percentile. In addition, mean F- intakes of all consumers aged less than 65 years were below AI, while F- intakes of those at the 95th centile of tea intake were above AI. This suggests tea can be consumed safely from age of 4 years. Some brands contained sufficient F- for a European Union (EU) health claim relating to strengthening and maintaining tooth enamel. In conclusion, typical tea consumption in the UK delivers F- within UL for most age groups not taking into account other sources of F-, but greater dental health benefits might be achieved if average adult consumption were to rise to 4–5 servings per day.
Article
Caffeine is a bitter substance and it is naturally found in coffee beans, cacao beans, kola nuts, guarana berries, and tea leaves including yerba mate. It has many effects on the body’s metabolism including stimulating the central nervous system. Caffeine ranks as one of the topmost commonly consumed dietary ingredients throughout the world. The total daily intake, as well as the major source of caffeine varies globally; however, coffee, tea and soft drinks are the 3 most prominent sources. Caffeine is part of a group of compounds known as methylxanthines, and is extremely widespread in nature. Two other methylxanthines, theophylline and the bromine, are also found in varying proportions in caffeine-containing foods and beverages. Both have similar effects to caffeine although the effects of the bromine are much weaker.
Article
This meta-analysis of tea consumption in relation to stroke, myocardial infarction, and all coronary heart disease is based on 10 cohort studies and seven case-control studies. The study-specific effect estimates for stroke and coronary heart disease were too heterogeneous to be summarized (homogeneity p < 0.02 for stroke, p < 0.001 for coronary heart disease). Only the relative risk estimates for myocardial infarction (seven studies) appeared reasonably homogeneous (homogeneity p = 0.20). The incidence rate of myocardial infarction is estimated to decrease by 11% with an increase in tea consumption of 3 cups per day (fixed-effects relative risk estimate = 0.89, 95% confidence interval: 0.79, 1.01) (1 cup = 237 ml). However, evidence of bias toward preferential publication of smaller studies that suggest protective effects urges caution in interpreting this result. The geographic region where the studies were conducted appeared to explain much of the heterogeneity among coronary heart disease, myocardial infarction, and probably stroke results. With increasing tea consumption, the risk increased for coronary heart disease in the United Kingdom and for stroke in Australia, whereas the risk decreased in other regions, particularly in continental Europe. Am J Epidemiol 2001;154:495-503.
Conference Paper
Tea provides around 70% of adult fluoride (F −) intakes in the UK, with mean intakes estimated as 540 ml daily for all adults, and 662 ml for older adults (1). A recent analysis (2) concluded that the F-content of some economy tea bags was too high, risking F-intakes which may exceed safe limits, assuming a daily tea intake of 1L. However, the infusions were made up using 2 g of tea in 100 ml, whereas a typical serving of tea is generally 3·125 g of tea in 240 ml (3). This, plus the long brewing time of 2–30 minutes may have overestimated F-content. Therefore, the present study set out to investigate the F-content of UK tea bags using a more typical infusion method and based on average tea intakes. Retail samples of tea bags, i.e. 28 black, 10 decaffeinated and 11 speciality (white, green, single estate black), were obtained from UK-based tea manufacturers and retailers. For total F-, three tea bags were selected at random from each lot and, after combining, were ashed at 600°C. The ash was cooled, acid digested and the solution cooled to approximately 20°C. A total ionic strength adjustment buffer was added to correct the pH and the sample was measured for Fusing an ion selective electrode. For infused F-, three tea bags were added separately to individual beakers after which 240 ml of freshly boiled de-ionized water was added. 40 seconds later, the tea bags were squeezed gently against the sides of the beakers and removed. The three individual brews were combined, stirred and cooled to approximately 20°C before aliquots were taken and F-content measured as for total F-. The entire process was carried out in triplicate. The results are shown below. Compared with the previous analysis (2) , our study found higher F-levels per kg but similar F-levels per L, despite the different brewing method. However, estimates of F-intake, based on 540 ml or 662 ml tea per d, were lower and remained below the EU Upper Limit of 7 mg per day (4) even assuming use of fluoridated water in the brew. This suggests that typical tea drinking in the UK does not pose a risk for health and, indeed, may provide benefits for dental health given EU approved health claims for fluoride (5)
Article
Studies that investigated the association between tea consumption and the risk of major cardiovascular events have reported inconsistent results. We conducted a meta-analysis of prospective observational studies in order to summarize the evidence regarding the association between tea consumption and major cardiovascular outcomes or total mortality. In July 2014, we performed electronic searches in PubMed, EmBase, and the Cochrane Library, followed by manual searches of reference lists from the resulting articles to identify other relevant studies. Prospective observational studies that reported effect estimates, with 95 % confidence intervals (CIs), for coronary heart disease (CHD), stroke, cardiac death, stroke death, or total mortality for more than two dosages of tea consumption were included. A random-effects meta-analysis was performed to determine the risk of major cardiovascular outcomes associated with an increase in tea consumption by 3 cups per day. Of the 736 citations identified from database searches, we included 22 prospective studies from 24 articles reporting data on 856,206 individuals, and including 8,459 cases of CHD, 10,572 of stroke, 5,798 cardiac deaths, 2,350 stroke deaths, and 13,722 total deaths. Overall, an increase in tea consumption by 3 cups per day was associated with a reduced risk of CHD (relative risk [RR], 0.73; 95 % CI: 0.53-0.99; P = 0.045), cardiac death (RR, 0.74; 95 % CI: 0.63-0.86; P < 0.001), stroke (RR, 0.82; 95 % CI: 0.73-0.92; P = 0.001), total mortality (RR, 0.76; 95 % CI: 0.63-0.91; P = 0.003), cerebral infarction (RR, 0.84; 95 % CI: 0.72-0.98; P = 0.023), and intracerebral hemorrhage (RR, 0.79; 95 % CI: 0.72-0.87; P < 0.001), but had little or no effect on stroke mortality (RR, 0.93; 95 % CI: 0.83-1.05; P = 0.260). The findings from this meta-analysis indicate that increased tea consumption is associated with a reduced risk of CHD, cardiac death, stroke, cerebral infarction, and intracerebral hemorrhage, as well as total mortality.
Article
The effect of tea intake on blood pressure (BP) is controversial. We performed a meta-analysis of randomised controlled trials to determine the changes in systolic and diastolic BP due to the intake of black and green tea. A systematic search was conducted in MEDLINE, EMBASE and the Cochrane Controlled Trials Register up to May 2014. The weighted mean difference was calculated for net changes in systolic and diastolic BP using fixed-effects or random-effects models. Previously defined subgroup analyses were performed to explore the influence of study characteristics. A total of twenty-five eligible studies with 1476 subjects were selected. The acute intake of tea had no effects on systolic and diastolic BP. However, after long-term tea intake, the pooled mean systolic and diastolic BP were lower by - 1·8 (95 % CI - 2·4, - 1·1) and - 1·4 (95 % CI - 2·2, - 0·6) mmHg, respectively. When stratified by type of tea, green tea significantly reduced systolic BP by 2·1 (95 % CI - 2·9, - 1·2) mmHg and decreased diastolic BP by 1·7 (95 % CI - 2·9, - 0·5) mmHg, and black tea showed a reduction in systolic BP of 1·4 (95 % CI - 2·4, - 0·4) mmHg and a decrease in diastolic BP of 1·1 (95 % CI - 1·9, - 0·2) mmHg. The subgroup analyses showed that the BP-lowering effect was apparent in subjects who consumed tea more than 12 weeks (systolic BP - 2·6 (95 % CI - 3·5, - 1·7) mmHg and diastolic BP - 2·2 (95 % CI - 3·0, - 1·3) mmHg, both P< 0·001). The present findings suggest that long-term ( ≥ 12 weeks) ingestion of tea could result in a significant reduction in systolic and diastolic BP.
Article
Fluoride is a naturally occurring mineral that can be obtained from foods and fluids originating from soils containing fluoride, as well as by drinking water that has been fluoridated. While consuming adequate fluoride intake can deliver benefits for dental and bone health, there have been concerns that excessive fluoride intake could lead to dental fluorosis, or even cause harm to bones. This article considers the balance of evidence in this area, and discusses the benefits and potential risks of fluoride in the UK diet. The role of tea as a major contributor to normal fluoride intake is highlighted, alongside some positive implications of this. Information is also provided to help nurses and midwives communicate the latest advice and guidance on fluoride to their patients.
Article
Type 2 diabetes mellitus and cardiovascular disease represent major causes of morbidity, which impact greatly on healthcare expenditure. Clinical studies suggest that ingestion of black tea, which contains a range of bioactive compounds, can inhibit oxidative damage and improve endothelial function. The objectives of this review are to: (1) evaluate observational evidence linking black tea consumption with the prevalence of cardiovascular diseases and type 2 diabetes; (2) consider the mechanisms by which black tea may have a protective effect; and (3) examine the potential role of tea drinking in relation to public health. The findings from epidemiological studies suggested a significant association between regular black tea consumption and a reduced risk of coronary heart disease at around three or more cups per day. For diabetes risk, the data are restricted to a few large cohort studies that suggested a beneficial association at one to four cups daily. These findings need to be confirmed by intervention trials. While some studies suggest that drinking black tea may reduce the risk of stroke, likely mechanisms remain unclear, highlighting the need for more human intervention studies. Disparities found involving studies may have been influenced by variations in reported tea intakes, limited sample sizes in intervention trials and inadequate control of confounders. In conclusion, drinking black tea may have a role in lowering the risk of coronary heart disease and type 2 diabetes. Future research should focus on controlled trials and studies to elucidate likely mechanisms of action.
Article
A systematic review and meta-analysis was conducted on 11 randomized placebo-controlled human studies of acute effects of tea constituents L-theanine and epigallocatechin gallate, administered alone or in combination with caffeine, on cognitive function and mood. The outcome measures of mood were alertness, calmness, and contentedness, derived from the Bond-Lader scales, and state anxiety, from the State-Trait Anxiety Inventory. Cognitive measures assessed were attentional switch, intersensory attention, and rapid visual information processing. Standardized mean differences between placebo and treatment groups are presented for each study and outcome measure. Meta-analysis using a random-effects model was conducted when data were available for three or more studies. Evidence of moderate effect sizes in favor of combined caffeine and L-theanine in the first 2 hours postdose were found for outcome measures Bond-Lader alertness, attentional switching accuracy, and, to a lesser extent, some unisensory and multisensory attentional outcomes. Moderator analysis of caffeine and L-theanine doses revealed trends toward greater change in effect size for caffeine dose than for L-theanine dose, particularly during the first hour postdose.
Article
Background: Fluid intake, especially water, is essential for human life and also necessary for physical and mental function. The present study aimed to assess beverage consumption across age groups. Methods: A systematic review was conducted. Original research in English language publications and available studies (or abstracts in English) from 2000 to 2013 was searched for by using the medical subheading (MeSH) terms: ('beverage' OR 'fluid' [Major]) AND ('consumption' [Mesh] OR 'drinking' [Mesh] OR 'intake' [Mesh]) AND ('child' [Mesh] OR 'adolescent' [Mesh] OR 'adult' [Mesh]). Article selection was restricted to those papers covering healthy populations of all age groups in a nationwide sample, or from a representative sample of the population of a city or cities, which examined the trends or patterns of beverage intake and the determinants of beverage intake. Sixty-five studies were identified with respect to beverage consumption across age groups. The papers were screened by thoroughly reading titles or abstracts. Full-text articles were assessed by three investigators. Results: Total beverage intake varied between 0.6 and 3.5 L day(-1) among all age groups (males more than females). Plain water contributed up to 58%, 75% and 80% of the total beverage intake in children, adolescents and adults, respectively. Milk consumption was higher among children; consumption of soft drinks was higher among adolescents; and the consumption of tea, coffee and alcoholic beverages was higher among adults. Conclusions: Plain water is the main water source for all age groups and the consumption of other beverages varies according to age.
Article
Background The increased availability of caffeinated drinks raises questions about the level of caffeine that is appropriate for children, as well as the benefits and risks associated with their consumption. Methods Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, this systematic review evaluates evidence from randomised controlled trials investigating the effects of caffeine on cognition, behaviour, mood and exercise performance in children. Observational studies and expert panel guidelines are also discussed. ResultsOne hundred and nine studies were found, with 11 randomised controlled trials and 13 observational studies meeting the criteria. High caffeine intakes (e.g. >5 mg kg–1 body weight day–1) were associated with an increased risk of anxiety and withdrawal symptoms. However, smaller amounts were not linked with such effects and may benefit cognitive function and sports performance based on adult studies. The evidence suggests that children and adolescents should limit daily caffeine consumption to 2.5 mg kg–1 body weight day–1, equating to one or two cups of tea or one small cup of coffee. Lower contributors of caffeine, such as tea, may be more appropriate for children because they contribute to daily fluid intakes and provide flavonoids. By contrast, caffeinated soft drinks may be less suitable options for children as a result of their acidity, higher caffeine content, presence of added sugar (in some cases) and absence of bioactive compounds. Conclusions More studies are needed to determine the intakes that represent a risk and whether there may be benefits for alertness and sports performance with moderate intakes of caffeine.
Article
In contrast to the consistent results of an inhibitory effect of green tea extracts and tea polyphenols on the development and growth of carcinogen-induced tumors in experimental animal models, results from human studies are mixed. Both observational and intervention studies have provided evidence in support of a protective role of green tea intake in the development oral-digestive tract cancer or an inhibitory role of oral supplementation of green tea extract on a precancerous lesion of oral cavity. Evidence in support of green tea intake against the development of liver cancer risk is limited and inconsistent. An inverse association between green tea intake and lung cancer risk has been observed among never smokers but not among smokers. Although observational studies do not support a beneficial role of tea intake against the development of prostate cancer, several phase 2 clinical trials have shown an inhibitory effect of green tea extract against the progression of prostate premalignant lesions to malignant tumors. Prospective epidemiologic studies so far have not provided evidence for a protective effect of green tea consumption on breast cancer development. Current data neither confirm nor refute a definitive cancer-preventive role of green tea intake. Large randomized intervention trials on the efficacy of green tea polyphenols or extracts are required before a recommendation for green tea consumption for cancer prevention should be made.
Article
Maintaining the level of daily energy expenditure during weight loss and weight maintenance is as important as maintaining satiety while decreasing energy intake. In this context, different catechin- and caffeine-rich teas (CCRTs), such as green, oolong, and white teas, as well as caffeine have been proposed as tools for maintaining or enhancing energy expenditure and for increasing fat oxidation. Tea polyphenols have been proposed to counteract the decrease in metabolic rate that is usually present during weight loss. Their effects may be of particular importance during weight maintenance after weight loss. Although the thermogenic effect of CCRT has the potential to produce significant effects on these metabolic targets as well as on fat absorption and energy intake, possibly via its impact on the gut microbiota and gene expression, a clinically meaningful outcome also depends on compliance by the subjects. Limitations to this approach require further examination, including moderating factors such as genetic predisposition, habitual caffeine intake, and catechin composition and dose. Nevertheless, CCRTs may be useful agents that could help in preventing a positive energy balance and obesity.
Article
Tea (Camellia sinensis) is a widely consumed beverage and has been extensively studied for its cancer-preventive activity. Both the polyphenolic constituents as well as the caffeine in tea have been implicated as potential cancer-preventive compounds; the relative importance seems to depend on the cancer type. Green tea and the green tea catechin have been shown to inhibit tumorigenesis at a number of organ sites and to be effective when administered either during the initiation or postinitiation phases of carcinogenesis. Black tea, although not as well studied as green tea, has also shown cancer-preventive effects in laboratory models. A number of potential mechanisms have been proposed to account for the cancer-preventive effects of tea, including modulation of phase II metabolism, alterations in redox environment, inhibition of growth factor signaling, and others. In addition to the laboratory studies, there is a growing body of human intervention studies suggesting that tea can slow cancer progression and modify biomarkers relevant to carcinogenesis. Although available data are promising, many questions remain with regard to the dose-response relations of tea constituents in various models, the primary mechanisms of action, and the potential for combination chemoprevention strategies that involve tea as well as other dietary or pharmaceutical agents. The present review examines the available data from laboratory animal and human intervention studies on tea and cancer prevention. These data were evaluated, and areas for further research are identified.
Article
There is a need to evaluate the evidence about the health effects of tea flavonoids and to provide valid, specific, and actionable tea consumption information to consumers. Emerging evidence suggests that the flavonoids in tea may be associated with beneficial health outcomes, whereas the benefits and risks of tea extracts and supplements are less well known. The next steps in developing tea science should include a focus on the most promising leads, such as reducing the risk of cardiovascular disease and stroke, rather than pursuing smaller, more diffuse studies of many different health outcomes. Future tea research should also include the use of common reference standards, better characterization of intervention products, and application of batteries of biomarkers of intakes and outcomes across studies, which will allow a common body of evidence to be developed. Mechanistic studies should determine which tea bioactive constituents have effects, whether they act alone or in combination, and how they influence health. Clinical studies should use well-characterized test products, better descriptions of baseline diets, and validated biomarkers of intake and disease risk reduction. There should be more attention to careful safety monitoring and adverse event reporting. Epidemiologic investigations should be of sufficient size and duration to detect small effects, involve populations most likely to benefit, use more complete tea exposure assessment, and include both intermediary markers of risk as well as morbidity and mortality outcomes. The construction of a strong foundation of scientific evidence on tea and health outcomes is essential for developing more specific and actionable messages on tea for consumers.
Article
Osteoporosis is a major health problem in the aging population worldwide. Cross-sectional and retrospective evidence indicates that tea consumption may be a promising approach in mitigating bone loss and in reducing risk of osteoporotic fractures among older adults. Tea polyphenols enhance osteoblastogenesis and suppress osteoclastogenesis in vitro. Animal studies reveal that intake of tea polyphenols have pronounced positive effects on bone as shown by higher bone mass and trabecular bone volume, number, and thickness and lower trabecular separation via increasing bone formation and inhibition of bone resorption, resulting in greater bone strength. These osteoprotective effects appear to be mediated through antioxidant or antiinflammatory pathways along with their downstream signaling mechanisms. A short-term clinical trial of green tea polyphenols has translated the findings from ovariectomized animals to postmenopausal osteopenic women through evaluation of bioavailability, safety, bone turnover markers, muscle strength, and quality of life. For future studies, preclinical animal studies to optimize the dose of tea polyphenols for maximum osteoprotective efficacy and a follow-up short-term dose-response trial in postmenopausal osteopenic women are necessary to inform the design of randomized controlled studies in at-risk populations. Advanced imaging technology should also contribute to determining the effective dose of tea polyphenols in achieving better bone mass, microarchitecture integrity, and bone strength, which are critical steps for translating the putative benefit of tea consumption in osteoporosis management into clinical practice and dietary guidelines.
Article
Epidemiologic studies have convincingly associated consumption of black tea with reduced cardiovascular risk. Research on the bioactive molecules has traditionally been focused on polyphenols, such as catechins. Black tea polyphenols (BTPs), however, mainly consist of high-molecular-weight species that predominantly persist in the colon. There, they can undergo a wide range of bioconversions by the resident colonic microbiota but can in turn also modulate gut microbial diversity. The impact of BTPs on colon microbial composition can now be assessed by microbiomics technologies. Novel metabolomics platforms coupled to de novo identification are currently available to cover the large diversity of BTP bioconversions by the gut microbiota. Nutrikinetic modeling has been proven to be critical for defining nutritional phenotypes related to gut microbial bioconversion capacity. The bioactivity of circulating metabolites has only been studied to a certain extent. Bioassays dedicated to specific aspects of gut and cardiovascular health have been used, although often at physiologically irrelevant concentrations and with limited coverage of relevant metabolite classes and their conjugated forms. Evidence for cardiovascular benefits of BTPs points toward antiinflammatory and blood pressure-lowering properties and improvement in platelet and endothelial function for specific microbial bioconversion products. Clearly, more work is needed to fill in existing knowledge gaps and to assess the in vitro and in vivo bioactivity of known and newly identified BTP metabolites. It is also of interest to assess how phenotypic variation in gut microbial BTP bioconversion capacity relates to gut and cardiovascular health predisposition.
Article
Background: There is increasing evidence that both green and black tea are beneficial for cardiovascular disease (CVD) prevention. Objectives: To determine the effects of green and black tea on the primary prevention of CVD. Search methods: We searched the following databases on 12 October 2012 without language restrictions: CENTRAL in The Cochrane Library, MEDLINE (OVID), EMBASE (OVID) and Web of Science (Thomson Reuters). We also searched trial registers, screened reference lists and contacted authors for additional information where necessary. Selection criteria: Randomised controlled trials (RCTs) lasting at least three months involving healthy adults or those at high risk of CVD. Trials investigated the intake of green tea, black tea or tea extracts. The comparison group was no intervention, placebo or minimal intervention. The outcomes of interest were CVD clinical events and major CVD risk factors. Any trials involving multifactorial lifestyle interventions or focusing on weight loss were excluded to avoid confounding. Data collection and analysis: Two review authors independently selected trials for inclusion, abstracted data and assessed the risk of bias. Trials of green tea were analysed separately from trials of black tea. Main results: We identified 11 RCTs with a total of 821 participants, two trials awaiting classification and one ongoing trial. Seven trials examined a green tea intervention and four examined a black tea intervention. Dosage and form of both green and black tea differed between trials. The ongoing trial is examining the effects of green tea powder capsules.No studies reported cardiovascular events.Black tea was found to produce statistically significant reductions in low-density lipoprotein (LDL) cholesterol (mean difference (MD) -0.43 mmol/L, 95% confidence interval (CI) -0.56 to -0.31) and blood pressure (systolic blood pressure (SBP): MD -1.85 mmHg, 95% CI -3.21 to -0.48. Diastolic blood pressure (DBP): MD -1.27 mmHg, 95% CI -3.06 to 0.53) over six months, stable to sensitivity analysis, but only a small number of trials contributed to each analysis and studies were at risk of bias.Green tea was also found to produce statistically significant reductions in total cholesterol (MD -0.62 mmol/L, 95% CI -0.77 to -0.46), LDL cholesterol (MD -0.64 mmol/L, 95% CI -0.77 to -0.52) and blood pressure (SBP: MD -3.18 mmHg, 95% CI -5.25 to -1.11; DBP: MD -3.42, 95% CI -4.54 to -2.30), but only a small number of studies contributed to each analysis, and results were not stable to sensitivity analysis. When both tea types were analysed together they showed favourable effects on LDL cholesterol (MD -0.48 mmol/L, 95% CI -0.61 to -0.35) and blood pressure (SBP: MD -2.25 mmHg, 95% CI -3.39 to -1.11; DBP: MD -2.81 mmHg, 95% CI -3.77 to -1.86). Adverse events were measured in five trials and included a diagnosis of prostate cancer, hospitalisation for influenza, appendicitis and retinal detachment but these are unlikely to be directly attributable to the intervention. Authors' conclusions: There are very few long-term studies to date examining green or black tea for the primary prevention of CVD. The limited evidence suggests that tea has favourable effects on CVD risk factors, but due to the small number of trials contributing to each analysis the results should be treated with some caution and further high quality trials with longer-term follow-up are needed to confirm this.
Article
Thearubigins (TR) are polymeric flavanol-derived compounds formed during the fermentation of tea leaves. Comprising ∼70% of total polyphenols in black tea, TR may contribute majorly to its beneficial effects on health. To date, there is no appropriate food composition data on TR, although several studies have used data from the US Department of Agriculture (USDA) database to estimate TR intakes. We aimed to estimate dietary TR in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort and assess the impact of including TR or not in the calculation of the total dietary flavonoid intake. Dietary data were collected using a single standardized 24-h dietary recall interviewer-administered to 36 037 subjects aged 35-74 years. TR intakes were calculated using the USDA database. TR intakes ranged from 0.9 mg/day in men from Navarra and San Sebastian in Spain to 532.5 mg/day in men from UK general population. TR contributed <5% to the total flavonoid intake in Greece, Spain and Italy, whereas in the UK general population, TR comprised 48% of the total flavonoids. High heterogeneity in TR intake across the EPIC countries was observed. This study shows that total flavonoid intake may be greatly influenced by TR, particularly in high black tea-consuming countries. Further research on identification and quantification of TR is needed to get more accurate dietary TR estimations.European Journal of Clinical Nutrition advance online publication, 24 April 2013; doi:10.1038/ejcn.2013.89.
Article
Purpose The purpose of this paper is to review evidence on the impact of black tea on health, highlighting the role of flavonoids. Design/methodology/approach This review builds on previous systematic reviews by incorporating new studies on black tea and health published between 2004 and 2009. Findings Black tea was strongly associated with heart disease prevention by plausible mechanisms linked to flavonoid bioactivity. In vitro studies suggest that tea has anti‐cancer properties, but this needs to be confirmed by additional long‐term human studies. Emerging research indicates that tea may benefit cognitive function and weight management, although more studies are needed. Tea flavonoids are bioavailable with or without milk. Originality/value The benefits of tea drinking are of relevance to public health as tea is the main contributor to dietary flavonoids in Western countries. Consuming one to eight cups of black tea per day is associated with a reduced risk of chronic disease. Caffeine intakes at this level are moderate.
Article
Summary The reputed benefits of moderate caffeine consumption include improvements in physical endurance, cognitive function, particularly alertness and vigilance, mood and perception of fatigue. In contrast, there are concerns that excessive intakes increase the risks of dehydration, anxiety, headache and sleep disturbances. This paper is a review of double-blind, placebo-controlled trials published over the past 15 years to establish what range of caffeine consumption would maximise benefits and minimise risks for cognitive function, mood, physical performance and hydration. Of the 41 human studies meeting the inclusion criteria, the majority reported benefits associated with low to moderate caffeine intakes (37.5 to 450 mg per day). The available studies on hydration found that caffeine intakes up to 400 mg per day did not produce dehydration, even in subjects undergoing exercise testing. It was concluded that the range of caffeine intake that appeared to maximise benefit and minimise risk is 38 to 400 mg per day, equating to 1 to 8 cups of tea per day, or 0.3 to 4 cups of brewed coffee per day. The limitations of the current evidence base are discussed.
Article
After consumption of tea, L-theanine enters systemic circulation and is assumed to enter the brain. Several human studies indicate that L-theanine influences brain functioning. Knowledge about the pharmacokinetics of L-theanine facilitates further study of this health effect. Volunteers received 25–100 mg of L-theanine as tea, as L-theanine-enriched tea, and as biosynthetic L-theanine in aqueous solutions. Plasma was analysed for L-thea-nine content after which data were fitted with a 1-compartment model. For all interven-tions, the lag time was approximately 10 min and half-lives of absorption and elimination were approximately 15 and 65 min respectively. After approximately 50 min, maximum plasma concentrations of between 1.0 and 4.4 mg/L were achieved. Maximum plasma concentration and area under the plasma-concentration–time curve were dose-proportional. This knowledge allows prediction of plasma concentrations for various dose regimens supporting further study of a health benefit of L-theanine.
Article
Water is essential for life and maintaining optimal levels of hydration is important for humans to function well. Water makes up a large proportion of our body weight (60% on average), distributed between the intracellular (inside cells) and extracellular (water in the blood and in between cells) compartments. Water is the major component of body fluids, such as blood, synovial fluid (fluid in the joints), saliva and urine, which perform vital functions in the body. The concentration of solutes (osmolality) in body fluids is closely controlled, and even very small changes in osmolality trigger a physiological response; either to increase body water by reducing urinary output and stimulating thirst; or to excrete excess water as urine. Generally, body water is maintained within narrow limits. However, if water losses are not sufficiently replaced, dehydration occurs. Extreme dehydration is very serious and can be fatal. More mild dehydration (about 2% loss of body weight) can result in headaches, fatigue and reduced physical and mental performance. It is also possible to consume too much water and in rare cases this can result in hyponatraemia (low levels of sodium in the blood).
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Summary Tea is the second most consumed beverage in the world after water. Health benefits have been associated with tea drinking, including a lower risk of coronary heart disease (CHD) and cancer, and protection against dental caries and bone loss. It is likely that these benefits relate to the high polyphenol content of tea and how these polyphenols are metabolised and used by the body. In contrast, concern has arisen about the impact of tea on hydration and iron status, and the role of tea as a source of caffeine. This article updates an earlier systematic review by including more recent published evidence on the potential role of black tea in human health. While it is clear from in vitro and animal research that tea polyphenols act as antioxidants and have a beneficial effect on many biochemical processes in the body via a range of complex mechanisms, findings from epidemiological studies and the few available human intervention studies have been contradictory. Reasons for this are explored, including the influence of lifestyle factors other than tea consumption on cancer or CHD risk. The clearest consistent evidence points to an association between tea consumption, in excess of three cups per day, and a reduced risk of myocardial infarction. More human research is needed to draw conclusions about cancer and other markers of CHD. There was no consistent evidence pointing to a detrimental effect of tea drinking on hydration, bone health or iron status. The caffeine content of tea was modest compared with other sources and was unlikely to have an adverse effect on health within an intake range of 1 to 8 cups of tea per day.
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Despite the protective role of diets rich in fruit plant polyphenols against some cancers and chronic degenerative and inflammatory diseases, insufficient emphasis has been placed on oral health. Numerous studies have aimed to ascertain the role of polyphenols in the prevention and treatment of oral diseases; however, even when in vitro evidence appears convincing, the same is not true for in vivo studies, and thus there is a general paucity of solid evidence based on animal and clinical trials. To the best of our knowledge, only two reviews of polyphenols and oral health have been published; however, neither considered the potential role of whole plant extracts, which contain mixtures of many polyphenols that are often not completely identified. In the present study, our main aim was to review the current state of knowledge (search period: January 1965 to March 2011) on the effects of plant extracts/polyphenols on oral health. We found data on grapes, berries, tea, cocoa, coffee, myrtle, chamomile, honey/propolis, aloe extracts and the three main groups of polyphenols (stilbenes, flavonoids and proanthocyanidins). Their effects on caries, gingivitis, periodontal disease, candidiasis, oral aphtae, oral mucositis, oral lichen planus, leukoplakia and oral cancer were investigated. The data suggest that there is a lack of strong evidence, in particular regarding randomized clinical trials. However, a fascinating starting point has been provided by pre-clinical studies that have shown interesting activities of polyphenols against the most common oral diseases (caries, periodontitis and candidiasis), as well as in oral cancer prevention.
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Health information technology will transform health care delivery over the coming years. The central element of this will be the electronic health record, maintained by health professionals and linked to other health care providers, patients, and research and population health databases. Support of oncology functionality will necessitate special attention to how electronic health records are constructed, cancer-related data represented within, and clinical decision support tools designed to best support the objectives of quality care and cost-effectiveness. Standardization of functions and software will permit data exchange, leading to enhanced interoperability of systems. The present efforts at establishing oncology-related standards for electronic health records are reviewed.
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Theanine is a non-protein amino acid that occurs naturally in the tea plant (Camellia sinensis) and contributes to the favourable taste of tea. It is also associated with effects such as the enhancement of relaxation and the improvement of concentration and learning ability. It is also linked with health benefits including the prevention of certain cancers and cardiovascular disease, the promotion of weight loss and enhanced performance of the immune system. Thus, there has been a significant rise in the demand for theanine. While theanine has been chemically and biologically synthesised, techniques to isolate theanine from natural sources remain an important area of research. In this review article, the properties and health benefits of theanine are summarised and the synthesis and isolation of theanine are reviewed and discussed. Future perspectives for the isolation of theanine from natural sources are also outlined.