Effects on blood pressure of drinking green and black tea

Bioactive molecules from terrestrial and seafood resources in hypertension treatment: focus on molecular mechanisms and targeted therapies

Hypertension (HTN), a complex cardiovascular disease (CVD), significantly impacts global health, prompting a growing interest in complementary and alternative therapeutic approaches. This review article seeks to provide an up-to-date and thorough summary of modern therapeutic techniques for treating HTN, with an emphasis on the molecular mechanisms of action found in substances found in plants, herbs, and seafood. Bioactive molecules have been a significant source of novel therapeutics and are crucial in developing and testing new HTN remedies. Recent advances in science have made it possible to understand the complex molecular mechanisms underlying blood pressure (BP)-regulating effects of these natural substances better. Polyphenols, flavonoids, alkaloids, and peptides are examples of bioactive compounds that have demonstrated promise in influencing several pathways involved in regulating vascular tone, reducing oxidative stress (OS), reducing inflammation, and improving endothelial function. The article explains the vasodilatory, diuretic, and renin-angiotensin-aldosterone system (RAAS) modifying properties of vital plants such as garlic and olive leaf. Phytochemicals from plants are the primary in traditional drug development as models for novel antihypertensive drugs, providing diverse strategies to combat HTN due to their biological actions. The review also discusses the functions of calcium channel blockers originating from natural sources, angiotensin-converting enzyme (ACE) inhibitors, and nitric oxide (NO) donors. Including seafood components in this study demonstrates the increased interest in using bioactive chemicals originating from marine sources to treat HTN. Omega-3 fatty acids, peptides, and minerals obtained from seafood sources have anti-inflammatory, vasodilatory, and antioxidant properties that improve vascular health and control BP. Overall, we discussed the multiple functions of bioactive molecules and seafood components in the treatment of HTN.

Comprehensive Understanding of the Relationship between Bioactive Compounds of Black Tea and its Angiotensin Converting Enzyme (ACE) Inhibition and Antioxidant Activity

Long term regular intake of black tea (BT) can lower blood pressure, which is probably due to its antioxidant activity and angiotensin converting enzymes (ACE) inhibitory activity. This study achieves a comprehensive understanding of the relationship between bioactive compounds of BT and its ACE inhibitory activity and antioxidant activity. Phenolic compounds are closely related to antioxidant activity and ACE inhibitory activity. Catechin (C) exhibits stronger inhibitory activity on ACE enzyme than that of other compounds. Molecular docking demonstrates that C could directly bind to ACE active site pockets and Zn(II). Other bioactive compounds are involved in antioxidant and ACE inhibitory activity in varying degrees but no obvious trend is established. Our study proposes a conjecture that some bioactive compounds of BT regulate antioxidant defenses through mechanisms that involve ACE. The mixed mode of in vitro inhibition of ACE and oxidant of BT bioactive compounds needs to be further investigated.

Plants Used as Antihypertensive

Hypertension is a critical health problem and worse other cardiovascular diseases. It is mainly of two types: Primary or essential hypertension and Secondary hypertension. Hypertension is the primary possibility feature for coronary heart disease, stroke and renal vascular disease. Herbal medicines have been used for millions of years for the management and treatment of hypertension with minimum side effects. Over aim to write this review is to collect information on the anti-hypertensive effects of natural herbs in animal studies and human involvement as well as to recapitulate the underlying mechanisms, from the bottom of cell culture and ex-vivo tissue data. According to WHO, natural herbs/shrubs are widely used in increasing order to treat almost all the ailments of the human body. Plants are the regular industrial units for the invention of chemical constituents, they used as immunity booster to enhance the natural capacity of the body to fight against different health problems as well as herbal medicines and food products also. Eighty percent population of the world (around 5.6 billion people) consume medicines from natural plants for major health concerns. This review provides a bird's eye analysis primarily on the traditional utilization, phytochemical constituents and pharmacological values of medicinal herbs used to normalize hypertension i.e. Hibiscus sabdariffa, Allium sativum, Andrographis paniculata, Apium graveolens, Bidenspilosa, Camellia sinensis, Coptis chinensis, Coriandrum sativum, Crataegus spp., Crocus sativus, Cymbopogon citrates, Nigella sativa, Panax ginseng,Salviaemiltiorrhizae, Zingiber officinale, Tribulus terrestris, Rauwolfiaserpentina, Terminalia arjuna etc.

The effect of black tea supplementation on blood pressure: a systematic review and dose-response meta-analysis of randomized controlled trials

The main goal of this work was to clarify the effects of black tea supplementation on blood pressure (BP) by performing a systematic review according to the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines, followed by a dose-response meta-analysis of randomized controlled trials (RCTs). Electronic search was carried out in PubMed, Embase and the Cochrane Library databases published up to March 2020. To be included, RCTs had to report the effect of black tea supplementation on systolic blood pressure (SBP) or diastolic blood pressure (DBP) in adults. A total of 13 trials, including 22 study arms were eligible for inclusion in the final quantitative analysis. It was observed that black tea supplementation significantly reduced SBP (WMD - 1.04 mmHg; 95% CI - 2.05 to -0.03; and P = 0.04) and DBP (WMD - 0.59 mmHg; 95% CI - 1.05 to -0.13; and P = 0.01) compared to the control. However, nonlinear analysis failed to indicate a significant influence of black tea flavonoid supplementation dose or duration on both SBP and DBP. Sensitivity analysis showed that no individual study had a significant impact on our results. In addition, we found no evidence for the presence of small-study effects among studies for both SBP and DBP. Thus, the favorable effect of black tea supplementation emerging from the current meta-analysis suggests the possible use of this tea as an active compound in order to promote cardiovascular health, mostly when used for longer duration (>7 days) and in men. Furthermore RCTs using different doses of black tea and various durations may contribute to confirming our conclusion.

Tea Consumption Patterns in Relation to Diet Quality among Children and Adults in the United States: Analyses of NHANES 2011-2016 Data

Flavonoid-rich tea offers an alternative to sugar-sweetened beverages. The present analyses, based on 2 24-hour dietary recalls for 17,506 persons aged ≥9 years old in the 2011–2016 National Health and Nutrition Examination Survey database (NHANES 2011–2016), explored tea consumption patterns in relation to demographics, diet quality, cardiovascular disease (CVD) biomarkers (lipids and blood pressure), and body weight. Beverage categories were unsweetened tea, other tea (herbal and presweetened tea), coffee, milk, 100% juice, water and other high-calorie (HC) and low-calorie (LC) beverages. Tea consumption (18.5% of the sample) was highest among older adults (51–70 years old), non-Hispanic Asians and Whites, and those with college education and higher incomes. The effects of age, gender, education, income, and race/ethnicity were all significant (p < 0.001 for all). Adult tea consumers had diets with more protein, fiber, potassium, iron, and magnesium, and less added sugars and alcohol. Their diets contained fewer HC beverages and coffee but had more total and citrus fruit, more total dark green and orange vegetables, and more seafood, eggs, soy and milk. Tea consumers had higher Healthy Eating Index (HEI-2015) and higher Nutrient-Rich Foods (NRF9.3) nutrient density scores. Few children drank tea and no differences in diet quality between consumers and non-consumers were observed. Adult tea consumers had slightly higher high-density lipoprotein (HDL) cholesterol and lower body mass index (BMI) values. Tea consumption was associated with higher socioeconomic status and better diets.

Effects and Mechanisms of Tea Regulating Blood Pressure: Evidences and Promises

Cardiovascular diseases have overtaken cancers as the number one cause of death. Hypertension is the most dangerous factor linked to deaths caused by cardiovascular diseases. Many researchers have reported that tea has anti-hypertensive effects in animals and humans. The aim of this review is to update the information on the anti-hypertensive effects of tea in human interventions and animal studies, and to summarize the underlying mechanisms, based on ex-vivo tissue and cell culture data. During recent years, an increasing number of human population studies have confirmed the beneficial effects of tea on hypertension. However, the optimal dose has not yet been established owing to differences in the extent of hypertension, and complicated social and genetic backgrounds of populations. Therefore, further large-scale investigations with longer terms of observation and tighter controls are needed to define optimal doses in subjects with varying degrees of hypertensive risk factors, and to determine differences in beneficial effects amongst diverse populations. Moreover, data from laboratory studies have shown that tea and its secondary metabolites have important roles in relaxing smooth muscle contraction, enhancing endothelial nitric oxide synthase activity, reducing vascular inflammation, inhibiting rennin activity, and anti-vascular oxidative stress. However, the exact molecular mechanisms of these activities remain to be elucidated.

Regular consumption of green tea improves pulse pressure and induces regression of left ventricular hypertrophy in hypertensive patients

This study characterized the effects of regular green tea (GT) and hot water (HW) ingestion on systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), and left ventricular hypertrophy (LVH) in two equal, sex- and age-matched groups; Grp1 and Grp2 (n = 100 each; age 53 ± 4 years) of hypertensive patients. Grp1 had regular GT treatment, followed by HW ingestion, whereas Grp2 had HW ingestion followed by GT treatment for periods of 4 months each. Electrocardiographic (ECG) and echocardiographic assessments of LVH were made before and at the end of both periods. SBP was lowered significantly by 6.6%; DBP by 5.1%, and PP by 9.1% by the end of month 4 of GT treatment in Grp1. Upon GT cessation and HW ingestion, SBP, DBP, and PP returned to pretreatment levels over 4 months. In Grp2, SBP, DBP, and PP were reduced insignificantly by 1.5%, 1.0%, and 2.3% by the end of the 4th month of HW ingestion. Conversely, over 4 months of GT treatment, SBP, DBP, and PP were significantly lowered by 5.4%, 4.1%, and 7.7% from the baseline values, respectively. ECG and echocardiographic evidence of LVH was shown in 20% of Grp1 and 24% of Grp2 patients before intervention. This was significantly lowered to 8% and 10% in Grp1 and Grp2 by GT treatment. However, this increased to 16% following HW ingestion in Grp1. HW ingestion did mot induce regression of LVH in Grp2. Thus, regular GT ingestion has cardiovascular protective effects.

Nutritional Supplements for the Treatment of Hypertension: A Practical Guide for Clinicians

Nutraceuticals are dietary components with pharmacologic properties that can be used to treat various disease states. There is growing interest among patients in the use of nutraceuticals for the management of hypertension; as such, it is important that clinicians are prepared to engage in meaningful discussions with their patients about these substances. Flavonoids, beetroot, garlic, and unsaturated fats have garnered significant attention for their blood pressure lowering properties. We review the clinical evidence and reported mechanisms of action for these substances in an attempt to offer a practical guide for clinicians to engage with patients who are highly motivated to seek out nutraceutical therapies to manage their hypertension.

Sources of inaccuracy in the measurement of adult patients' resting blood pressure in clinical settings: a systematic review

BACKGROUND

To interpret blood pressure (BP) data appropriately, healthcare providers need to be knowledgeable of the factors that can potentially impact the accuracy of BP measurement and contribute to variability between measurements.

METHODS

A systematic review of studies quantifying BP measurement inaccuracy. Medline and CINAHL databases were searched for empirical articles and systematic reviews published up to June 2015. Empirical articles were included if they reported a study that was relevant to the measurement of adult patients' resting BP at the upper arm in a clinical setting (e.g. ward or office); identified a specific source of inaccuracy; and quantified its effect. Reference lists and reviews were searched for additional articles.

RESULTS

A total of 328 empirical studies were included. They investigated 29 potential sources of inaccuracy, categorized as relating to the patient, device, procedure or observer. Significant directional effects were found for 27; however, for some, the effects were inconsistent in direction. Compared with true resting BP, significant effects of individual sources ranged from -23.6 to +33 mmHg SBP and -14 to +23 mmHg DBP.

CONCLUSION

A single BP value outside the expected range should be interpreted with caution and not taken as a definitive indicator of clinical deterioration. Where a measurement is abnormally high or low, further measurements should be taken and averaged. Wherever possible, BP values should be recorded graphically within ranges. This may reduce the impact of sources of inaccuracy and reduce the scope for misinterpretations based on small, likely erroneous or misleading, changes.

Effect of black tea consumption on radial blood pulse spectrum and cognitive health

Black tea consumption has been proven to improve endothelial function and to lower the risk of stroke and cognitive impairment. Several effects of black tea on cardiovascular system had been surveyed. However, the black tea effect on pressure pulse spectrum remains unknown. The study was aimed to investigate the influence of black tea on radial blood pressure and Pulse Spectrum. Fourteen healthy subjects received water and single doses of black tea (0.05g/Kg) in separate weeks. The radial blood pressure and pulse wave were measured and the pressure pulses were evaluated using harmonic analysis. This report confirmed that black tea consumption (dose=0.05g/Kg) significantly increased third, fifth, (P<0.1), sixth, seventh, and eighth harmonics (p<0.05) of radial pressure wave comparing to water control. We proposed that black tea may increase cerebral blood flow (CBF), which was deduced from the results and from the conclusions of previous studies. The results also showed that the harmonic components of pressure pulse could be the vascular kinetic index that assessed the hemodynamic status in each time frame before and after consumption of black tea.

Anti-hypertensive Herbs and their Mechanisms of Action: Part I

The use of herbal therapies for treatment and management of cardiovascular diseases (CVDs) is increasing. Plants contain a bounty of phytochemicals that have proven to be protective by reducing the risk of various ailments and diseases. Indeed, accumulating literature provides the scientific evidence and hence reason d'etre for the application of herbal therapy in relation to CVDs. Slowly, but absolutely, herbal remedies are being entrenched into evidence-based medical practice. This is partly due to the supporting clinical trials and epidemiological studies. The rationale for this expanding interest and use of plant based treatments being that a significant proportion of hypertensive patients do not respond to Modern therapeutic medication. Other elements to this equation are the cost of medication, side-effects, accessibility, and availability of drugs. Therefore, we believe it is pertinent to review the literature on the beneficial effects of herbs and their isolated compounds as medication for treatment of hypertension, a prevalent risk factor for CVDs. Our search utilized the PubMed and ScienceDirect databases, and the criterion for inclusion was based on the following keywords and phrases: hypertension, high blood pressure, herbal medicine, complementary and alternative medicine (CAM), nitric oxide, vascular smooth muscle cell (VSMC) proliferation, hydrogen sulfide, nuclear factor kappa-B, oxidative stress, and epigenetics/epigenomics. Each of the aforementioned keywords was co-joined with herb in question, and where possible with its constituent molecule(s). In this first of a two-part review, we provide a brief introduction of hypertension, followed by a discussion of the molecular and cellular mechanisms. We then present and discuss the plants that are most commonly used in the treatment and management of hypertension.

Correlation between tea consumption and prevalence of hypertension among Singaporean Chinese residents aged ⩾40 years

By a cross-sectional epidemiology study, we attempted to correlate the consumption of tea and/or health supplements, living habits and socio-demographic factors to the prevalence of hypertension among Singaporean Chinese residents. Singaporean Chinese residents aged ⩾40 years were randomly selected and interviewed face-to-face by clinical research assistants. Hypertension was defined as measured systolic blood pressure at least 140 mm Hg and/or diastolic blood pressure at least 90  mmHg or self-reported history/treatment for hypertension. The prevalence of hypertension among the whole investigated population (N=1184, 58.27% females) was 49.73% and the prevalence increased to 66.47% in the sub-population aged ⩾60 years. High risk of hypertension was associated with age ⩾60 years (odds ratio (OR): 4.15-4.19, P<0.01), obesity (body mass index >25 kg m(-2), OR: 2.10-2.11, P<0.01), family history of hypertension (OR: 2.69-2.76, P<0.01), diabetes history (OR: 2.29-2.33, P<0.01), hyperlipidemia history (OR: 1.79-1.80, P<0.01), male (OR: 1.56-1.59, P<0.01) and coffee intake (OR: 1.44-1.46, P<0.05). In contrast, drinking green tea at least 150 ml per week was associated with lower hypertension risk (OR: 0.63, 95% confidence interval (CI): 0.43-0.91, P<0.05). Drinking combination of green tea and British tea was associated with higher reduction in the risk of hypertension (OR: 0.58, 95% CI: 0.39-0.85, P<0.05). This cross-sectional study suggests that consumption of tea, especially green tea and British tea, was associated with lowering the risk of hypertension. On the other hand, consumption of coffee could be a risk factor of hypertension. These findings may provide useful information for health promotion to reduce risk of hypertension and warrant further study to confirm and elucidate such association.

Tea, but not coffee consumption, is associated with components of arterial pressure. The Observation of Cardiovascular Risk Factors study in Luxembourg

There is uncertainty regarding the impact of tea and coffee consumption on arterial blood pressure. The present study aimed to examine the association between blood pressure (BP) components, namely, systolic BP (SBP), diastolic BP, mean arterial pressure, and pulse pressure (PP), and tea or coffee consumption, taking into account simultaneous consumption. The study population was derived from a national cross-sectional stratified sample of 1352 individuals aged 18 to 69 years, recruited between November 2007 and January 2009 to participate in the Observation of Cardiovascular Risk Factors in Luxembourg study. We hypothesized that greater tea consumption would be independently associated with lower BP. Tea and coffee consumptions in deciliters per day were obtained from a semiquantitative food frequency questionnaire. Participants were classified into 3 groups: nonconsumers, ≤3-dL/d consumers, and >3-dL/d consumers of each beverage separately. After exclusion of subjects taking antihypertensive medications, several general linear models were performed to investigate the independent relationship between tea/coffee consumption and BP components. Tea consumers (36.3%) were more likely to be younger women, nonsmokers, with better cardiometabolic profiles, and less frequent chronic pathologies, whereas the reverse was true for coffee consumers (88%). Greater tea consumption was associated with lower SBP and PP values, after adjustment for age, sex, education, lifestyle, and dietary confounding factors, including coffee drinking. No association between BP components and coffee consumption was observed. Daily consumption of 1 dL of tea was associated with a significant reduction of SBP by 0.6 mm Hg and PP by 0.5 mm Hg. Given the widespread consumption of tea and coffee throughout the world, together with the major cardiovascular disease risk, our findings have important implications for human health.

Protective effect of kombucha on rats fed a hypercholesterolemic diet is mediated by its antioxidant activity

CONTEXT

Kombucha (KT) is claimed to have various beneficial effects on human health, but there is very little scientific evidence available in the literature.

OBJECTIVE

The present study investigates the effects of Camellia sinensis (GT) Linn. (Theaceae) and KT, two natural drinks, on cholesterol and antioxidant status using a hypercholesterolemia rat model.

MATERIALS AND METHODS

The present study compared the free-radical scavenging abilities and polyphenol levels of GT and KT. Wistar rats fed cholesterol-rich diets were given KT or GT (5 mL/kg body weight per day, po) for 16 weeks, then fasted overnight and sacrificed. The plasma lipid levels, thiobarbituric acid reactive substances (TBARS) and aspartate aminotransferase (AST), alanine aminotransferase (ALT), and γ-glutamyl transpeptidase (GGT) serum levels, antioxidant activities of superoxide dismutase (SOD) and catalase (CAT), and creatinine and urea rats were examined.

RESULTS

KT had a phenolic compound of 955 ± 0.75 mg GAE/g) followed, by GT (788.92 ± 0.02 mg GAE/g). The free radical scavenging activity of KT was higher than GT. Compared with GT, KT induced lowered serum levels of TC, TG, VLDL-C, and LDL-C by 26, 27, 28, and 36%, respectively, and increased the serum level of high-density lipoprotein cholesterol (HDL-C). KT induced a 55% decrease of TBARS level in liver and 44% in kidney, compared with those of rats fed a cholesterol-rich diet alone. Moreover, CAT and SOD activities were reduced by 29 and 33%, respectively, in liver and 31 and 35%, respectively, in kidney, after oral administration of KT, compared with those of HCD-fed rats.

CONCLUSION

The findings revealed that KT administration induced attractive curative effects on hypercholesterolemic, particularly in terms of liver-kidney functions in rats. Its effect on humans needs to be studied further.

Differing chemical compositions of three teas may explain their different effects on acute blood pressure in spontaneously hypertensive rats

BACKGROUND

Heavy tea consumption is suggested to be unsuitable for hypertensive people. However, the bioactive substances in different varieties of tea leaves are very different. This study compares the effects of three Chinese teas - C. sinensis, C. ptilophylla and C. assamica var. kucha - on blood pressure (BP) and heart rate in spontaneously hypertensive rats (SHRs).

RESULTS

Intragastric administration of C. sinensis extract led to an acute increase in systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate in SHRs. However, C. ptilophylla and C. assamica var. kucha exerted no obvious influences on SBP, DBP or heart rate. Similar to the extract of C. sinensis, intragastric administration of caffeine also led to an acute increase in BP and heart rate in SHRs. In contrast, theobromine and theacrine - purine alkaloids predominantly contained in C. ptilophylla and C. assamica var. kucha, respectively - had no pressor effects. The effect of caffeine on BP was related to the regulation of plasma epinephrine and norepinephrine levels in SHRs.

CONCLUSION

The different effects of C. sinensis, C. ptilophylla and C. assamica var. kucha on BP might be explained, at least partially, by the differences in the varieties and contents of purine alkaloids.

Small molecule-sensing strategy and techniques for understanding the functionality of green tea

Various low-molecular-weight phytochemicals in green tea (Camellia sinensis L.), especially (-)-epigallocatechin-3-O-gallate (EGCG), are known to be involved in health promotion and disease risk reduction. However, the underlying mechanism has remained elusive because of the absence of an analytical technique that can easily detect the precise behavior of such a small molecule. Recently, we have identified a cell-surface EGCG-sensing receptor and the related signaling molecules that control the physiological functions of EGCG. We also developed a novel in situ label-free imaging technique for visualizing spatially resolved biotransformations based on simultaneous mapping of EGCG and its phase II metabolites. Furthermore, we established a chemometric method capable of evaluating the functionality of multicomponent green tea extracts by focusing on their compositional balances. This review highlights our proposed small molecule-sensing techniques for detecting the complex behavior of green tea components and linking such information to an enhanced understanding of green tea functionality.

(−)-Epicatechin prevents alterations in the metabolism of superoxide anion and nitric oxide in the hearts ofl-NAME-treated rats

The aim of this work was to evaluate the effects of (−)-epicatechin administration in the heart of a rat model with reduced NO production that follows a short-term treatment withl-NAME.

Tea consumption is inversely related to 5-year blood pressure change among adults in Jiangsu, China: a cross-sectional study

BACKGROUND

Data relating to the association between tea consumption and blood pressure change are inconsistent. The aim of this analysis was to investigate the association between tea consumption and the change in blood pressure (BP) in Chinese adults over a 5-year period.

METHODS

Data from 1109 Chinese men (N= 472) and women (N= 637) who participated in the Jiangsu Nutrition Study (JIN) were analysed. BP was measured in 2002 and 2007. Tea (green, black and total tea) consumption was quantitatively assessed at the follow-up survey in 2007.

RESULTS

Total tea and green tea consumption were inversely associated with 5-year diastolic BP (DBP) but not systolic BP (SBP) change. In the multivariable analysis, compared with no consumption of tea, those with daily total tea/green tea consumption of at least10 g had 2.41 mmHg and 3.68 mmHg smaller increase of DBP respectively. There was a significant interaction between smoking and total tea/green tea consumption and DBP change. The inverse association between total tea/green tea consumption and DBP change was significant only in non-smokers. Green tea consumption was inversely associated with SBP change only in non-smokers and those without central obesity.

CONCLUSION

The consumption of green tea is inversely associated with 5-year BP change among Chinese adults, an effect abrogated by smoking.

Effects of tea intake on blood pressure: a meta-analysis of randomised controlled trials

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.

The effect of green tea on blood pressure and lipid profile: a systematic review and meta-analysis of randomized clinical trials

INTRODUCTION

Many different dietary supplements are currently marketed for the management of hypertension, but the evidence for effectiveness is mixed. The aim of this systematic review was to evaluate the evidence for or against the effectiveness of green tea (Camellia sinensis) on blood pressure and lipid parameters.

METHODS AND RESULTS

Electronic searches were conducted in Medline, Embase, Amed, Cinahl and the Cochrane Library to identify relevant human randomized clinical trials (RCTs). Hand searches of bibliographies were also conducted. The reporting quality of included studies was assessed using a checklist adapted from the CONSORT Statement. Two reviewers independently determined eligibility, assessed the reporting quality of the included studies, and extracted the data. As many as 474 citations were identified and 20 RCTs comprising 1536 participants were included. There were variations in the designs of the RCTs. A meta-analysis revealed a significant reduction in systolic blood pressure favouring green tea (MD: -1.94 mmHg; 95% CI: -2.95 to -0.93; I(2) = 8%; p = 0.0002). Similar results were also observed for total cholesterol (MD: -0.13 mmol/l; 95% CI: -0.2 to -0.07; I(2) = 8%; p < 0.0001) and LDL cholesterol (MD: -0.19 mmol/l; 95% CI: -0.3 to -0.09; I(2) = 70%; p = 0.0004). Adverse events included rash, elevated blood pressure, and abdominal discomfort.

CONCLUSION

Green tea intake results in significant reductions in systolic blood pressure, total cholesterol, and LDL cholesterol. The effect size on systolic blood pressure is small, but the effects on total and LDL cholesterol appear moderate. Longer-term independent clinical trials evaluating the effects of green tea are warranted.

The effect of black tea on blood pressure: a systematic review with meta-analysis of randomized controlled trials

Objective

Epidemiological evidence has linked consumption of black tea, produced from Camellia sinensis, with a reduced risk of cardiovascular diseases. However, intervention studies on the effects of tea consumption on blood pressure (BP) have reported inconsistent results. Our objective was to conduct a systematic literature review with meta-analysis of controlled human intervention studies examining the effect of tea consumption on BP.

Methods

We systematically searched Medline, Biosis, Chemical Abstracts and EMBASE databases through July 2013. For inclusion, studies had to meet the following pre-defined criteria: 1) placebo controlled design in human adults, 2) minimum of 1 week black tea consumption as the sole intervention, 3) reported effects on systolic BP (SBP) or diastolic BP (DBP) or both. A random effects model was used to calculate the pooled overall effect of black tea on BP.

Results

Eleven studies (12 intervention arms, 378 subjects, dose of 4–5 cups of tea) met our inclusion criteria. The pooled mean effect of regular tea ingestion was −1.8 mmHg (95% CI: −2.8, −0.7; P = 0.0013) for SBP and −1.3 mmHg (95% CI: −1.8, −0.8; P<0.0001) for DBP. In covariate analyses, we found that the method of tea preparation (tea extract powders versus leaf tea), baseline SBP and DBP, and the quality score of the study affected the effect size of the tea intervention (all P<0.05). No evidence of publication bias could be detected.

Conclusions

Our meta-analysis indicates that regular consumption of black tea can reduce BP. Although the effect is small, such effects could be important for cardiovascular health at population level.

The role of nutrition and nutraceutical supplements in the treatment of hypertension

Vascular biology, endothelial and vascular smooth muscle and cardiac dysfunction play a primary role in the initiation and perpetuation of hypertension, cardiovascular disease and target organ damage. Nutrient-gene interactions and epigenetics are predominant factors in promoting beneficial or detrimental effects in cardiovascular health and hypertension. Macronutrients and micronutrients can prevent, control and treat hypertension through numerous mechanisms related to vascular biology. Oxidative stress, inflammation and autoimmune dysfunction initiate and propagate hypertension and cardiovascular disease. There is a role for the selected use of single and component nutraceutical supplements, vitamins, antioxidants and minerals in the treatment of hypertension based on scientifically controlled studies which complement optimal nutrition, coupled with other lifestyle modifications.

Acute effects of green tea extract intake on exogenous and endogenous metabolites in human plasma

The acute effects of green tea extract (GTE) on plasma metabolites in vivo are largely unknown. In this parallel, double-blind study, the transient changes in total and free concentrations of catechins were measured in plasma from healthy males following the consumption of a single GTE dose (559.2 mg total catechins, 120.4 mg caffeine). Furthermore, the acute effects on endogenous metabolites were assessed 2 h after GTE intake using four-phase metabolite profiling. The ratios of the catechin concentrations in plasma to those in the GTE followed the order ECG/CG > EC > GCG > EGCG > EGC > C > GC. The gallated catechins EGCG, CG/ECG, GC, and GCG were also present in their free form. Sixteen out of 163 mostly endogenous metabolites were affected by acute GTE ingestion, when compared to placebo. These included caffeine, salicylate, hippurate, taurine, 3,4-dihydroxyphenylethylene-glycol, serotonin, some cholesterylesters, fatty acids, triglycerides, and sphingosines. Our results on the exogenous metabolites largely confirm previous studies, while our findings on the endogenous metabolites are novel and may suggest specific biological targets.

Nutrition and nutraceutical supplements for the treatment of hypertension: part III

Vascular biology, endothelial and vascular smooth muscle, and cardiac dysfunction play a primary role in the initiation and perpetuation of hypertension, cardiovascular disease, and target organ damage. Nutrient-gene interactions and epigenetics are predominant factors in promoting beneficial or detrimental effects in cardiovascular health and hypertension. Macronutrients and micronutrients can prevent, control, and treat hypertension through numerous mechanisms related to vascular biology. Oxidative stress, inflammation, and autoimmune dysfunction initiate and propagate hypertension and cardiovascular disease. There is a role for the selected use of single and component nutraceutical supplements, vitamins, antioxidants, and minerals in the treatment of hypertension based on scientifically controlled studies that complement optimal nutrition, coupled with other lifestyle modifications.

Green and black tea for the primary prevention of cardiovascular disease

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.

Dietary (poly)phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases

Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-μM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.

Effect of beetroot juice on lowering blood pressure in free-living, disease-free adults: a randomized, placebo-controlled trial

Background

The consumption of beetroot juice on a low nitrate diet may lower blood pressure (BP) and therefore reduce the risk of cardiovascular events. However, it is unknown if its inclusion as part of a normal diet has a similar effect on BP. The aim of the study was to conduct a randomized controlled trial with free-living adults to investigate if consuming beetroot juice in addition to a normal diet produces a measureable reduction in BP.

Method

Fifteen women and fifteen men participated in a double-blind, randomized, placebo-controlled, crossover study. Volunteers were randomized to receive 500 g of beetroot and apple juice (BJ) or a placebo juice (PL). Volunteers had BP measured at baseline and at least hourly for 24-h following juice consumption using an ambulatory blood pressure monitor (ABPM). Volunteers remained at the clinic for 1-h before resuming normal non-strenuous daily activities. The identical procedure was repeated 2-wk later with the drink (BJ or PL) not consumed on the first visit.

Results

Overall, there was a trend (P=0.064) to lower systolic blood pressure (SBP) at 6-h after drinking BJ relative to PL. Analysis in men only (n=13) after adjustment for baseline differences demonstrated a significant (P<0.05) reduction in SBP of 4 – 5 mmHg at 6-h after drinking BJ.

Conclusions

Beetroot juice will lower BP in men when consumed as part of a normal diet in free-living healthy adults.

Trial registration

anzctr.org.au ACTRN12612000445875

The impact of the catechol-O-methyltransferase genotype on vascular function and blood pressure after acute green tea ingestion

SCOPE

Evidence for the benefits of green tea catechins on vascular function is inconsistent, with genotype potentially contributing to the heterogeneity in response. Here, the impact of the catechol-O-methyltransferase (COMT) genotype on vascular function and blood pressure (BP) after green tea extract ingestion are reported.

METHODS AND RESULTS

Fifty subjects (n = 25 of the proposed low-activity [AA] and of the high-activity [GG] COMT rs4680 genotype), completed a randomized, double-blind, crossover study. Peripheral arterial tonometry, digital volume pulse (DVP), and BP were assessed at baseline and 90 min after 1.06 g of green tea extract or placebo. A 5.5 h and subsequent 18.5 h urine collection was performed to assess green tea catechin excretion. A genotype × treatment interaction was observed for DVP reflection index (p = 0.014), with green tea extract in the AA COMT group attenuating the increase observed with placebo. A tendency for a greater increase in diastolic BP was evident at 90 min after the green tea extract compared to placebo (p = 0.07). A genotypic effect was observed for urinary methylated epigallocatechin during the first 5.5 h, with the GG COMT group demonstrating a greater concentration (p = 0.049).

CONCLUSION

Differences in small vessel tone according to COMT genotype were evident after acute green tea extract.

Short-term effects of polyphenol-rich black tea on blood pressure in men and women

There is increasing evidence that black tea polyphenols contribute to vascular health. We have recently shown that regular ingestion of polyphenol-rich black tea over 6 months results in lower systolic and diastolic blood pressure. However, the time course of these effects remains unclear. Therefore, our objective was to determine if short-term effects of tea on blood pressure could contribute to longer-term benefits of regular tea consumption on blood pressure. Men and women (n = 111) were recruited to a randomised placebo-controlled double-blind parallel designed trial. During a 4-week run-in, all participants consumed 3 cups per day of black tea. Participants then consumed 3 cups over 1 day of either powdered black tea solids containing 429 mg of polyphenols (tea), or a control product matched in flavour and caffeine content but containing no tea solids. The 24 h ambulatory blood pressure and heart rate was measured at the end of the 4-week run-in (baseline) and again during the 24 h intervention period. The 24 h day-time and night-time blood pressures were not significantly different between tea and control (P > 0.05). Baseline-adjusted net effects on mean 24 h ambulatory blood pressure for systolic and diastolic blood pressure were -0.2 mm Hg (95% CI, -1.5 to 1.0), P = 0.72, and 0.0 mm Hg (95% CI, -1.0 to 0.9), P = 0.95, respectively. Heart rate was significantly lower for tea compared to control during the night-time and early-morning periods (-2.0 (95% CI, -3.2, -0.8) bpm, and -1.9 (95% CI, -3.7, -0.2) bpm, respectively; P < 0.05 for both), but not during the day-time. These results suggest that the longer-term benefits of black tea on blood pressure are unlikely to be due to short-term changes.

Metabolomics-driven nutraceutical evaluation of diverse green tea cultivars

Background

Green tea has various health promotion effects. Although there are numerous tea cultivars, little is known about the differences in their nutraceutical properties. Metabolic profiling techniques can provide information on the relationship between the metabolome and factors such as phenotype or quality. Here, we performed metabolomic analyses to explore the relationship between the metabolome and health-promoting attributes (bioactivity) of diverse Japanese green tea cultivars.

Methodology/Principal Findings

We investigated the ability of leaf extracts from 43 Japanese green tea cultivars to inhibit thrombin-induced phosphorylation of myosin regulatory light chain (MRLC) in human umbilical vein endothelial cells (HUVECs). This thrombin-induced phosphorylation is a potential hallmark of vascular endothelial dysfunction. Among the tested cultivars, Cha Chuukanbohon Nou-6 (Nou-6) and Sunrouge (SR) strongly inhibited MRLC phosphorylation. To evaluate the bioactivity of green tea cultivars using a metabolomics approach, the metabolite profiles of all tea extracts were determined by high-performance liquid chromatography-mass spectrometry (LC-MS). Multivariate statistical analyses, principal component analysis (PCA) and orthogonal partial least-squares-discriminant analysis (OPLS-DA), revealed differences among green tea cultivars with respect to their ability to inhibit MRLC phosphorylation. In the SR cultivar, polyphenols were associated with its unique metabolic profile and its bioactivity. In addition, using partial least-squares (PLS) regression analysis, we succeeded in constructing a reliable bioactivity-prediction model to predict the inhibitory effect of tea cultivars based on their metabolome. This model was based on certain identified metabolites that were associated with bioactivity. When added to an extract from the non-bioactive cultivar Yabukita, several metabolites enriched in SR were able to transform the extract into a bioactive extract.

Conclusions/Significance

Our findings suggest that metabolic profiling is a useful approach for nutraceutical evaluation of the health promotion effects of diverse tea cultivars. This may propose a novel strategy for functional food design.

Effects of some common food constituents on cardiovascular disease

Cardiovascular diseases are the major cause of morbidity and mortality worldwide, and there is considerable interest in the role of dietary constituents and supplements in the prevention and treatment of these disorders. We reviewed the major publications related to potential effects on cardiovascular risk factors and outcomes of some common dietary constituents: carotenoids, flavonoid-rich cocoa, tea, red wine and grapes, coffee, omega-3 fatty acids, and garlic. Increased intake of some of these has been associated with reduced all-cause mortality or reduced incidence of myocardial infraction, stroke, and hypertension. However, although the evidence from observational studies is supportive of beneficial effects for most of these foodstuffs taken as part of the diet, potential benefits from the use of supplements derived from these natural products remain largely inconclusive.

Health effects of green tea catechins in overweight and obese men: a randomised controlled cross-over trial

Regular consumption of green tea may be cardioprotective. In the present study we investigated the health effects of dietary supplementation with green tea catechins and the potential modifying effect of the catechol-O-methyltransferase (COMT) Val/Met genotype. Subjects (sedentary males, aged 40-69 years, with BMI ≥ 28 and ≤ 38 kg/m(2)) were randomly assigned to consume decaffeinated green tea extract (DGT; 530 mg containing about 400 mg total catechins/capsule, twice daily) and placebo in a complete cross-over design. Ambulatory blood pressure and biomarkers of metabolic function (cholesterol, TAG, glucose and insulin) were measured at weeks 0 and 6. Although a marked increase in the concentration of plasma epigallocatechin gallate (EGCG), urinary epigallocatechin (EGC) and urinary 4'-O-methyl EGC was found after DGT treatment, no effect on blood pressure or biomarkers of metabolic function was observed. However, a period × treatment interaction (P < 0·05) was detected for body-weight change. Despite a similar increase in estimated energy intake during intervention period 1, body weight decreased by 0·64 (sd 2·2) kg and increased by 0·53 (sd 1·9) kg in the DGT and placebo groups, respectively (P = 0·025), suggesting a protective effect of green tea catechins on weight gain. Additionally, the COMT Val/Met genotype influenced urinary accumulation of EGC and 4'-O-methyl EGC (P < 0·01). Mean concentrations were lower in individuals homozygous for the high-activity G-allele, possibly reflecting increased metabolic flux and a more rapid conversion to downstream metabolic species, compared with individuals carrying at least one copy of the low-activity A-allele. Additional studies are needed to confirm these findings and further explore the modifying effect of genotype.

Inhibition of angiotensin converting enzyme (ACE) activity by polyphenols from tea (Camellia sinensis) and links to processing method

The focus of this study was to investigate Angiotensin Converting Enzyme (ACE) inhibiting activity across 34 teas (Camellia sinensis) produced by 5 different processing methods including green (GT), oolong (OT), white (WT), black (BT) and dark (DT) teas. In vitro ACE inhibitory activity was affected by the tea processing method with IC(50) values for ACE inhibition: green < oolong < white < black < dark teas. Substrate-dependence of the reaction kinetics was studied for GT and BT polyphenolic size fractions either < or > 3 kDa and also Green Tea Polyphenolic Isolate (GTPI), and revealed that enzyme velocity curves fitted allosteric, not Michaelis-Menten, relationships. Inhibition was weakly dependent on substrate concentration for GT fraction >3 kDa and independent of substrate concentration for all other GT and BT size fractions and GTPI. Furthermore, evidence for direct inactivation of ACE by GTPI was demonstrated. Overall, the results suggest that tea polyphenolics exert a mixed mode of in vitro inhibition of ACE, mostly of a kinetically uncompetitive type. The results are discussed in the context of in vivo and epidemiological evidence for regulation of blood pressure by tea consumption.

Tea and cardiovascular disease

There is increasing evidence for a protective effect of tea consumption against cardiovascular disease. This review summarizes the available epidemiological data providing evidence for and against such an effect. We also review observational and intervention studies that investigated an effect of tea and tea extracts on cardiovascular risk factors, including blood pressure, serum lipids, diabetes mellitus, and obesity. Finally, we review potential mechanisms of benefit, including anti-inflammatory, anti-oxidant, and anti-proliferative effects, as well as favorable effects on endothelial function. Overall, the observational data suggest a benefit, but results are mixed and likely confounded by lifestyle and background dietary factors. The weight of evidence indicates favorable effects on risk factors and a number of plausible mechanisms have been elucidated in experimental and translational human studies. Despite the growing body evidence, it remains uncertain whether tea consumption should be recommended to the general population or to patients as a strategy to reduce cardiovascular risk.

Green tea polyphenol sensing

Green tea polyphenols have emerged over the past two decades as an important dietary factor for health promotion. There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate (EGCG) inhibit carcinogenesis. However, the mechanisms for the cancer-preventive activity of EGCG are not completely characterized and many features remain to be elucidated. Recently we have identified a cell-surface EGCG receptor and the relating molecules that confer EGCG responsiveness to many cancer cells at physiological concentrations. Here, we review some of the reported mechanisms for the cancer chemopreventive action of EGCG and provide an overview of several molecules that sense and manage the physiological functions of EGCG.

Diurnal blood pressure variation and related behavioral factors

Blood pressure (BP) varies according to many internal and external factors, and behavioral factors have an important role in diurnal BP variation. BP rises sharply on waking in the morning and falls during sleep at night, although it varies throughout the day and night. These changes in BP are closely related to mental and physical activities, and the sympathetic nervous system mainly contributes to the diurnal variation in BP. Other behavioral factors, such as food consumption and obesity, dietary intake of sodium, drinking and smoking habits, consumption of coffee and tea, and bathing, also affect the diurnal variation in BP. Alterations in diurnal BP variation due to behavioral factors are frequently seen in patients with hypertension and can be classified as morning hypertension, daytime hypertension and nighttime hypertension. Appropriate lifestyle modifications may normalize or improve both the level and rhythm of BP in these patients.