Ingestion Of Tea Research Articles

Does green tea catechin enhance weight-loss effect of exercise training in overweight and obese individuals? a systematic review and meta-analysis of randomized trials.

Green tea (GT) is a common component of supplements known as fat burners. It has gained popularity as an ergogenic aid for weight reduction to assist with obesity management. This systematic review and meta-analysis aim to explore the effect of green tea ingestion coupled with exercise training (EX) on body composition and lipid profile in overweight and obese individuals. Two independent researchers systematically searched the electronic databases of PubMed, Web of Science, and Scopus. Studies with a randomized-controlled design to compare the effect of green tea in conjunction with exercise training (EX+GT) versus exercise training alone (EX+P) in overweight or obese participants were included. Of the 1,015 retrieved studies, 24 were identified to undergo full-text review, out of which 10 randomized trials met the inclusion criteria. EX+GT versus EX+P had a small and consistent effect on weight [Standardized mean difference (SMD) = -0.30, CI: -0.53 to -0.07], BMI [SMD = -0.33 CI: -0.64 to -0.02] and fat reduction [SMD = -0.29, CI: -0.57 to -0.01] and there was no evidence of heterogeneity across the trials. When compared to EX+P, EX+GT had no greater effect on lipid profile improvement [triglyceride: SMD = -0.92, CI: -1.30 to 0.49; LDL: SMD = -1.44, CI: -0.73 to 0.82; HDL: SMD = 0.56, CI -0.71 to 0.46; and total cholesterol SMD = -0.54, CI -0.85 to 0.13]. Current evidence suggests that green tea could have quite minimal additive benefit over exercise-induced weight loss. However, incorporation of green tea into exercise training does not seem to exert additional benefits on lipid profile and it warrants further investigations in the future.

A pilot study comparing the initial clinical response to different proton pump inhibitors within first week in treating erosive esophagitis

AbstractGastroesophageal reflux disease (GERD) characterized by heartburn and/or acid regurgitation symptoms is one of the most common gastrointestinal disorders. The rapid onset of proton pump inhibitors (PPIs) to improve annoying symptom is an essential need in treating GERD. There was no report about the short‐term clinical effects comparing lansoprazole 30 mg to rabeprazole 20 mg. This pilot study was designed to compare the initial one‐week clinical response of the two drugs in GERD with erosive esophagitis. Total 44 patients with GERD were enrolled in this study and randomized into two groups. The patients had the symptoms of acid regurgitation, heartburn, or feeling of acidity in the stomach and erosive esophagitis proven by endoscopy. They respectively received once‐daily dose of lansoprazole 30 mg (n = 23) and rabeprazole 20 mg (n = 21) for treatment of GERD. The primary end point was complete symptom resolution (CSR). The CSR rate was evaluated by questionnaire including acid regurgitation, heartburn sensation and epigastric pain at day 1, 3 and 7. Two patients in the arm of rabeprazole had poor compliance of drugs and were excluded from analysis. The final patient numbers were 23 in the arm of lansoprazole and 19 in rabeprazole. The baseline characteristics of two groups were similar in age, gender, body mass index (BMI), Helicobacter pylori infection, GERD severity, smoking, alcohol, coffee, spicy, sweet food and laboratory data. The ingestion of tea was the only one variable with significant difference between the two groups (65.2% and 31.58%, p = .03). At day 1, 3 and 7, the CSR rate of lansoprazole and rabeprazole were 21.74% and 26.32% (p = 1.000), 34.78% and 31.58% (p = .827), 47.83% and 47.37% (p = .976), respectively. The other clinical factors, including age, gender, BMI, Helicobacter pylori infection, smoking, alcohol, coffee, tea, spicy, sweet food and laboratory data, have also no significant influence on CSR rates at day 1, 3, 7. However, the patients with GERD C and D had significantly higher CSR rate than patients with GERD A and B at day 1 and 7 (CSR rate at day 1: 50.00% vs. 15.63, p = .040; day 3: 60.00% vs. 25.00%, p = .059; day 7: 90.00% vs. 34.38%, p = .003). In multivariate regression analysis, the patients with GERD C and D still had significantly higher CSR rate than patients with GERD A and B at day 7 (Odds ratio: 28.27, 95% CI: 2.10–380.03, p = .012). The CSR rates between lansoprazole group and rabeprazole group at day 1, 3, 7 were not significantly different, so the difference of PPIs did not play the role on the initial clinical response within 1 week for the erosive GERD patients. However, the patients with more severe erosive GERD on endoscopy had higher CSR rate at day 7.

A V-shaped bis-coumarin based fluorescence probe for F- detection in tea infusions and potable water and bioimaging applications in living systems

Fluorine (F) is a pivotal element in the formation of human dental and skeletal tissues, and the consumption of water and tea constitutes a significant source of fluoride intake. However, prolonged ingestion of water and tea with excessive fluoride content can lead to fluorosis, which poses a serious health hazard. In this manuscript, a novel turn-on fluorescent probe DCF synthesized by bis-coumarin and tert-butyldiphenylsilane (TBDPS) was introduced for detecting F- in potable water and tea infusions. By leveraging the unique chemical affinity between fluoride and silicon, F- triggers the silicon-oxygen bond cleavage in DCF, culminating in a conspicuous emission of yellow fluorescence. Validated through a succession of optical tests, this probe exhibits remarkable advantages in terms of superior selectivity, a low detection limit, a large Stokes shift, and robust interference resistance when detecting inorganic fluoride. Moreover, it can serve as portable test strips for on-site real-time identification and quantitative analysis of F-. Furthermore, the application of DCF for in-situ monitoring and imaging of F- in zebrafish and soybean root tissues proved its significant value for F- detection in both animal and plant systems. This probe potentially functions as an efficient instrument for delving into the toxic mechanisms of fluoride in physiological processes.

Distinguishable short-term effects of tea and water drinking on human saliva redox

Food consumption can alter the biochemistry and redox status of human saliva, and the serving temperature of food may also play a role. The study aimed to explore the immediate (3 min) and delayed (30 min) effects of hot tea (57 ± 0.5 °C) ingestion and cold tea (8 ± 0.5 °C) ingestion on the salivary flow rate and salivary redox-relevant attributes. The saliva was collected from 20 healthy adults before, 3-min after and 30-min after the tea ingestion. The hot or cold deionised water at the same temperatures were used as control. The salivary flow rate and redox markers in hot tea (HBT), cold tea (CBT), hot water (HW) and cold water (CW) group were analysed and compared. The results demonstrated that neither the black tea nor the water altered the salivary flow rate; the black tea immediately increased the salivary thiol (SH) and malondialdehyde (MDA) content while reduced salivary uric acid (UA) significantly. The tea ingestion showed a tendency to elevate the ferric reducing antioxidant power (FRAP) in saliva, although not significantly. The water ingestion decreased the MDA content immediately and increased the UA level significantly. Cold water was found to induce a greater delayed increase in total salivary total protein (TPC) than the hot water. In conclusion, the black tea ingestion affects the redox attributes of human saliva acutely and significantly, while the temperature of drink makes the secondary contribution.

Human Metabolism and Excretion of Kawakawa (Piper excelsum) Leaf Chemicals.

Piper excelsum (kawakawa) has a history of therapeutic use by Māori in Aotearoa New Zealand. It is currently widely consumed as a beverage and included as an ingredient in "functional" food product. Leaves contain compounds that are also found in a wide range of other spices, foods, and medicinal plants. This study investigates the human metabolism and excretion of kawakawa leaf chemicals. Six healthy male volunteers in one study (Bioavailability of Kawakawa Tea metabolites in human volunteers [BOKA-T]) and 30 volunteers (15 male and 15 female) in a second study (Impact of acute Kawakawa Tea ingestion on postprandial glucose metabolism in healthy human volunteers [TOAST]) consume a hot water infusion of dried kawakawa leaves (kawakawa tea [KT]). Untargeted Liquid Chromatography-Tandem Mass spectrometry (LC-MS/MS) analyses of urine samples from BOKA-T identified 26 urinary metabolites that are significantly associated with KT consumption, confirmed by the analysis of samples from the independent TOAST study. Seven of the 26 metabolites are also detected in plasma. Thirteen of the 26 urinary compounds are provisionally identified as metabolites of specific compounds in KT, eight metabolites are identified as being derived from specific compounds in KT but without resolution of chemical structure, and five are of unknown origin. Several kawakawa compounds that are also widely found in other plants are bioavailable and are modified by phase 1 and 2 metabolism.

The Acute Effect of Chamomile Intake on Blood Coagulation Tests in Healthy Volunteers: A Randomized Trial.

Chamomile administration may have desirable effects in the perioperative setting. Current practice, however, discourages perioperative chamomile use due to a theoretical increase in bleeding. Therefore, we evaluated if chamomile acutely (within 4 h of ingestion) prolongs coagulation assays. Eight healthy volunteers were randomized to receive 2 interventions in a crossover design: (a) single dose of chamomile extract capsule (500 mg) and (b) single dose of chamomile tea (3 g in 150 mL water). Interventions were separated at least 3 days apart from each other. Blood was sampled pre-ingestion, 2 h post-ingestion, and 4 h post-ingestion for each intervention. The primary outcome was the maximal change in prothrombin time (PT) before vs after each intervention. Secondary outcomes included changes in international normalized ratio, activated partial thromboplastin time, thrombin time, reptilase time, and fibrinogen levels. All 8 subjects completed the study. The average pre-ingestion PT values for tea and capsules were 11.9 (1.1) s and 12.0 (0.9) s, respectively. Tea significantly increased the average maximum PT by 0.7 (0.2) s (P = 0.0078). Extract capsules increased the maximum PT by 0.3 (0.2) s (P = 0.06). Neither PT prolongation met the predefined 10% threshold for clinical significance. No significant changes in secondary outcomes were observed. Chamomile tea ingestion prolongs PT. However, the clinical significance of this is unclear at this time and warrants further investigation. ClinicalTrials.gov Registration Number: NCT05272475.

Acute effects of (-)-gallocatechin gallate-rich green tea extract on the cerebral hemodynamic response of the prefrontal cortex in healthy humans.

The benefits of long-term consumption of green tea on the brain are well known. However, among many ingredients of green tea, the acute effects of (-)-gallocatechin gallate-rich green tea extract (GCG-GTE), have received comparatively less attention. Herein, we investigated the acute effects of oral ingestion of green tea with GCG-GTE, which contains close replicas of the ingredients of hot green tea, on task-dependent hemodynamics in the prefrontal cortex of healthy adult human brains. In this randomized, double-blind, placebo-controlled, parallel group trial, 35 healthy adults completed computerized cognitive tasks that demand activation of the prefrontal cortex at baseline and 1 h after consumption of placebo and 900 mg of GCG-GTE extract supplement. During cognitive testing, hemodynamic responses (change in HbO2 concentration) in the prefrontal cortex were assessed using functional near-infrared spectroscopy (fNIRS). In fNIRS data, significant group x session interactions were found in the left (p = 0.035) and right (p = 0.036) dorsolateral prefrontal cortex (DLPFC). In behavioral data, despite the numerical increase in the GCG-GTE group and the numerical decrease in the Placebo group, no significant differences were observed in the cognitive performance measure between the groups. The result suggests a single dose of orally administered GCG-GTE can reduce DLPFC activation in healthy humans even with increased task demand. GCG-GTE is a promising functional material that can affect neural efficiency to lower mental workload during cognitively demanding tasks. However, further studies are needed to verify this.

Microplastics and phthalate esters release from teabags into tea drink: occurrence, human exposure, and health risks.

Tea, the most common infusion worldwide, is usually sold in teabags due to the ease of usage. The increase in the use of plastic materials in the food packaging industry has led to an increase in released contaminants, such as microplastics (MPs) and phthalates (PAEs), in various food products including teabags. In this research, the abundance and features of MPs as well as PAEs concentration were investigated in 45 teabag samples of different Persian and German brands. The abundance of MPs in the Persian and German teabag samples was averagely 412.32 and 147.28 items/single teabag, respectively. Also, average PAEs levels in the Persian and German teabag samples were 2.87 and 2.37 mg/g, respectively. The predominant size category of MPs was related to 100-250 μm. Fibers and transparent were the dominant shape and color of detected MPs in teabags, respectively. Polyethylene (PE) and nylon were the most common MP polymer types. The most prominent PAEs congeners in teabag samples were diethylhexyl phthalate (DEHP) and diisobutyl phthalate (DiBP). Furthermore, MP exposure hazard through tea ingestion was analyzed for children and adults. DEHP showed the cancer risk (CR) for children and adults. The findings of this research indicated that high MPs and PAEs levels are released from teabags into tea drinks. Considering a daily drinking of a volume of 150 and 250 mL tea by children and adults, 486 and 810 MPs may enter their bodies, respectively. Thus, tea prepared with teabag-packed herbs may pose a significant health risk for consumers.

A cluster of acute thebaine poisonings from non-food grade poppy seeds in the Australian food supply

Introduction Poppy seed tea is used for its opioid effects and contains multiple opium alkaloids, including morphine, codeine, papaverine, and thebaine. Animal studies indicate thebaine has strychnine-like properties, but there is limited literature describing human thebaine poisoning. We describe a cluster of acute thebaine poisoning in people ingesting tea made using poppy seeds with high thebaine content that entered the Australian food supply chain. Methods This is an observational study of patients poisoned after drinking poppy seed tea. Cases were identified by three prospective toxicovigilance systems: the Emerging Drug Network of Australia collaboration, the New South Wales Prescription, Recreational and Illicit Substance Evaluation program, and the Emerging Drugs Network of Australia Victoria study. We report characteristics of clinical toxicity in cases with reported ingestion of poppy seed tea and analytical confirmation of thebaine exposure. Results Forty cases presenting with multi-system toxicity following poppy seed tea ingestion were identified across seven Australian states/territories from November 2022 to January 2023. Blood testing in 23 cases confirmed high thebaine concentrations. All 23 were male (median age 35, range 16–71 years). All patients experienced muscle spasms. Rigidity was described in nine, convulsions in six, while rhabdomyolysis, acute kidney injury, and metabolic acidosis occurred in five patients. There were two cardiac arrests. The thebaine median admission blood concentration was 1.6 mg/L, with a range of 0.1–5.6 mg/L, and was the dominant opium alkaloid in all samples. Convulsions, acute kidney injury, metabolic acidosis, and cardiac arrest were associated with increasing median thebaine concentrations. Four patients were managed in the Intensive Care Unit, with two receiving continuous kidney replacement therapy (one also received intermittent haemodialysis) for kidney injury. There was one death. Conclusions Thebaine toxicity, like strychnine poisoning, resulted in neuromuscular excitation characterized by muscle spasm, rigidity, and convulsions. Severe toxicity, including acute kidney injury, metabolic acidosis, and cardiac arrest, appears dose-dependent.

Postprandial Metabolic Responses to High-fat Feeding in Healthy Adults Following Ingestion of Oolong Tea–Derived Polymerized Polyphenols: A Randomized, Double-blinded, Placebo-controlled Crossover Study

BackgroundPolymerized polyphenols (PP) found in oolong tea can inhibit pancreatic lipase activity in vitro, and pilot work indicates that this may reduce postprandial lipemia. Since tea contains caffeine and catechins, the interactions between these ingredients and PP warrant investigation. ObjectivesTo assess whether PP ingested alone or with caffeine and catechins lowers postprandial lipemia. MethodsFifty healthy adults [mean (SD) age: 26 (7) y; BMI (in kg/m2): 24.0 (2.7); female: n = 16] completed 4 oral lipid tolerance tests in a placebo-controlled randomized, crossover design. Participants ingested 40 g of fat with either 1) placebo, 2) 100 mg PP, 3) 150 mg PP, or 4) 100 mg PP plus 50 mg caffeine and 63 mg catechins (PP + CC). Blood was sampled for 3 h postprandially to assess concentrations of serum and plasma triacylglycerol and plasma markers of lipid (NEFA; glycerol; LDL and HDL cholesterol; and ApoA-I, A-II, B, C-II, C-III, and E) and glucose metabolism (glucose, insulin, and C-peptide). ResultsSerum and plasma triacylglycerol concentrations and lipid metabolism variables generally increased following any test drink ingestion (main effect of time, p < 0.001). Nevertheless, for the lipid metabolism responses, there were no statistically significant condition–time interactions and no statistically significant differences in incremental or total area under the curve between conditions, apart from HDL cholesterol (p = 0.021). Ingesting 100 mg PP + CC lowered peak plasma glucose, insulin, and C-peptide concentrations compared with all other conditions 30 min postingestion (p < 0.001), with persistent alterations in glucose concentrations observed for 90 min compared with placebo and 100 mg PP conditions. ConclusionsPP ingested at doses ≤150 mg does not clearly alter early-phase postprandial triacylglycerol concentrations in healthy adults, irrespective of the presence or absence of caffeine and catechins. Nevertheless, caffeine and catechins added to PP lowered postprandial glucose and insulin concentrations.This trial was registered in ClinicalTrials.gov as NCT03324191 (https://clinicaltrials.gov/ct2/show/NCT03324191).

Relation of Tea Ingestion to Salivary Redox and Flow Rate in Healthy Subjects

The biochemistry of human saliva can be altered by food intake. The benefits of tea drinking were extensively studied but the influence of tea ingestion on human saliva has not been revealed. The work aimed to investigate the immediate and delayed effect of vine tea, oolong tea and black tea intake on certain salivary biochemistry and flow rate. The saliva samples of healthy subjects were collected before, after and 30 min after tea ingestion. The chemical compositions and antioxidant capacity of tea samples were analyzed to correlate with salivary parameters. Principal component analysis indicated that the effects of vine tea consumption were dominated by increasing salivary flow rate (SFR), production rate of total protein (TPC), thiol (SH), malondialdehyde, catalase activity and antioxidant capacity (FRAP) in saliva. The antioxidant profile of studied tea samples (FRAP, polyphenols, flavonoids) was positively correlated with salivary SFR, TPC, SH and FRAP but negatively correlated with salivary uric acid concentration in saliva.

Superior mesenteric artery syndrome identified following bubble tea ingestion and duodenal impaction: a case report.

Superior mesenteric artery syndrome identified following bubble tea ingestion and duodenal impaction: a case report.

Is there tea complemented with the appealing flavor of microplastics? A pioneering study on plastic pollution in commercially available tea bags in Bangladesh.

Microplastic pollution is a global concern, mainly due to its adverse effects on organisms and ecosystems. However, our knowledge of its impact on humans, in particular, is still very limited. Thus, while we have not gathered definitive information on their consequences, studies that aim to identify the MP's sources constitute subsidies to better understand the various exposure pathways to these pollutants. Thus, we investigated the possible presence of MP-like particles in teabag samples (of different brands) obtained in Dhaka, Bangladesh. Surprisingly, all analyzed samples (five brands) were contaminated with MPs. Fragments and fibers were identified in a higher percentage, and a wide variety of colors was identified, with a predominance of brown, blue, and red colors. Scanning electron microscope images of teabags exhibited net-like structures of fiber particles with a smooth surface. Furthermore, we observed irregularly shaped MPs and rougher surfaces and fragments in the process of detachment from the main fiber, oxidation flakes, and fracture-like. The average size of these pollutants was between 200.6 and 220.7 μm, and the polymer types identified via Fourier-transform infrared spectroscopy (FT-IR) were polytetrafluoroethylene, high-density polyethylene, polycarbonate, nylon, polyvinyl chloride, polytetrafluoroethylene, ethylene-vinyl acetate, cellulose acetate, and acrylonitrile butadiene styrene, the last three being the most frequent in the analyzed samples. Finally, we noticed that MPs from tea bags in Dhaka could cause an average emission of 10.9 million grams of MPs/year. Although the teabags analyzed in our study are not "complemented with the appealing flavor of MPs", it is very likely that tea ingestion in Dhaka is accompanied by the concomitant ingestion of plastic particles making teabags an important route of human exposure to these micropollutants.

Acute Effects of Kawakawa (Piper excelsum) Intake on Postprandial Glycemic and Insulinaemic Response in a Healthy Population.

Background: Piper excelsum (kawakawa) is an endemic shrub of Aotearoa, New Zealand, of cultural and medicinal importance to Māori. Its fruits and leaves are often consumed. These tissues contain several compounds that have been shown to be biologically active and which may underpin its putative health-promoting effects. The current study investigates whether kawakawa tea can modulate postprandial glucose metabolism. Methods: We report a pilot three-arm randomized crossover study to assess the bioavailability of kawakawa tea (BOKA-T) in six male participants with each arm having an acute intervention of kawakawa tea (4 g/250 mL water; 1 g/250 mL water; water) and a follow-up two-arm randomized crossover study to assess the impact of acute kawakawa tea ingestion on postprandial glucose metabolism in healthy human volunteers (TOAST) (4 g/250 mL water; and water; n = 30 (15 male and 15 female)). Participants consumed 250 mL of kawakawa tea or water control within each study prior to consuming a high-glycemic breakfast. Pre- and postprandial plasma glucose and insulin concentrations were measured, and the Matsuda index was calculated to measure insulin sensitivity. Results: In the BOKA-T study, lower plasma glucose (p < 0.01) and insulin (p < 0.01) concentrations at 60 min were observed after consumption of a high-dose kawakawa tea in comparison to low-dose or water. In the TOAST study, only plasma insulin (p = 0.01) was lower at 60 min in the high-dose kawakawa group compared to the control group. Both studies showed a trend towards higher insulin sensitivity in the high-dose kawakawa group compared to water only. Conclusions: Consuming kawakawa tea may modulate postprandial glucose metabolism. Further investigations with a longer-term intervention study are warranted.

Effect of Black Tea Consumption on Urinary Risk Factors for Kidney Stone Formation.

Copious fluid intake is the most essential nutritional measure in the treatment of urolithiasis, and is suggested to be a protective factor in the primary prevention of urinary stone formation. Although the intake of black tea contributes to daily fluid intake, the high oxalate content could outweigh the beneficial effect of urine dilution. The present study investigated the effect of black tea consumption on urinary risk factors for kidney stone formation. Ten healthy men received a standardized diet for a period of ten days. Subjects consumed 1.5 L/day of fruit tea (0 mg/day oxalate) during the 5-day control phase, which was replaced by 1.5 L/day of black tea (86 mg/day oxalate) during the 5-day test phase. Fractional and 24-h urines were obtained. The intake of black tea did not significantly alter 24-h urinary oxalate excretion. Urinary citrate, an important inhibitor of calcium stone formation, increased significantly, while the relative supersaturation of calcium oxalate, uric acid, and struvite remained unchanged. No significantly increased risk for kidney stone formation could be derived from the ingestion of black tea in normal subjects. Further research is needed to evaluate the impact of black tea consumption in kidney stone patients with intestinal hyperabsorption of oxalate.

Rapid Inactivation In Vitro of SARS-CoV-2 in Saliva by Black Tea and Green Tea.

Saliva plays major roles in the human-to-human transmission of SARS-CoV-2. If the virus in saliva in SARS-CoV-2-infected individuals can be rapidly and efficiently inactivated by a beverage, the ingestion of the beverage may attenuate the spread of virus infection within a population. Recently, we reported that SARS-CoV-2 was significantly inactivated by treatment with black tea, green tea, roasted green tea and oolong tea, as well as their constituents, (-) epigallocatechin gallate (EGCG), theasinensin A (TSA), and galloylated theaflavins. However, it remains unclear to what extent tea inactivates the virus present in saliva, because saliva contains various proteins, nitrogenous products, electrolytes, and so on, which could influence the antivirus effect of tea. Here, we assessed whether tea inactivated the SARS-CoV-2 which was added in human saliva. A virus was added in healthy human saliva in vitro, and after treatment with black tea or green tea, the infectivity of the virus was evaluated by TCID50 assays. The virus titer fell below the detectable level or less than 1/100 after treatment with black tea or green tea for 10 s. The black tea-treated virus less remarkably replicated in cells compared with the untreated virus. These findings suggest the possibility that the ingestion of tea may inactivate SARS-CoV-2 in saliva in infected individuals, although clinical studies are required to determine the intensity and duration of the anti-viral effect of tea in saliva in humans.

Black tea decreases postprandial blood glucose levels in healthy humans and contains high-molecular-weight polyphenols that inhibit α-glucosidase and α-amylase in vitro: a randomized, double blind, placebo-controlled, crossover trial

Background: To prevent diabetes, it is important to control postprandial glycemic levels. Studies have suggested that consuming black tea decreases the risk of type 2 diabetes; however, only a few studies have examined the effects of black tea on postprandial glycemic control after consuming starch-rich foods. In addition, the mechanism underlying the suppression of postprandial glucose levels remains unclear.Objective: To investigate the effects of black tea on postprandial blood glucose levels in healthy humans and to identify the components of black tea that inhibit digestive enzymes.Methods: The inhibitory activity of black tea on digestive enzymes was measured, and the inhibitory components were fractionated. Healthy Japanese adults ingested 200 ml of black tea, and its effect on postprandial blood glucose and insulin levels were investigated. Results: Black tea dose-dependently inhibited α-glucosidase, sucrase, and α-amylase activity. The major components responsible for this inhibition were high–molecular-weight polyphenols. The galloyl moieties present in these compounds play an important role in their inhibitory activities. Two randomized, double-blind, placebo-controlled, crossover studies of healthy human subjects (total n = 46) were conducted to investigate the effect of black tea on blood glucose and insulin levels. Combined data from the two studies showed that black tea ingestion (200 mL) after cooked rice intake (200 g) significantly reduced the incremental area under the curve of glucose (P =.024) and insulin (P =.014) compared to placebo drink.Conclusions: The high–molecular-weight polyphenols in black tea inhibited α-glucosidase, sucrase, and α-amylase activity in a dose-dependent manner. Furthermore, black tea ingestion after eating cooked rice significantly reduced the incremental area under the curve of glucose and insulin. These effects of black tea could be attributed to the inhibition of digestive enzymes by high–molecular-weight polyphenols containing galloyl groups.Keywords: black tea, blood glucose, α-glucosidase, α-amylase, polyphenol

Effect of ingestion of black tea on salivary mutans streptococci- a randomised clinical trial

Effect of ingestion of black tea on salivary mutans streptococci- a randomised clinical trial

Subacute Ingestion of Caffeine and Oolong Tea Increases Fat Oxidation without Affecting Energy Expenditure and Sleep Architecture: A Randomized, Placebo-Controlled, Double-Blinded Cross-Over Trial.

Ingesting oolong tea or caffeine acutely increases energy expenditure, and oolong tea, but not caffeine, stimulates fat oxidation. The acute effects of caffeine, such as increased heart rate and interference with sleep, diminish over 1–4 days, known as caffeine tolerance. During each 14-day session of the present study, 12 non-obese males consumed oolong tea (100 mg caffeine, 21.4 mg gallic acid, 97 mg catechins and 125 mg polymerized polyphenol), caffeine (100 mg), or placebo at breakfast and lunch. On day 14 of each session, 24-h indirect calorimetry and polysomnographic sleep recording were performed. Caffeine and oolong tea increased fat oxidation by ~20% without affecting energy expenditure over 24-h. The decrease in the respiratory quotient by oolong tea was greater than that by caffeine during sleep. The effect of oolong tea on fat oxidation was salient in the post-absorptive state. These findings suggest a role of unidentified ingredients in oolong tea to stimulate fat oxidation, and this effect is partially suppressed in a postprandial state. Two weeks of caffeine or oolong tea ingestion increased fat oxidation without interfering with sleep. The effects of subacute ingestion of caffeine and oolong tea differed from the acute effects, which is a particularly important consideration regarding habitual tea consumption.

Acute effect of green tea and hibiscus ingestion on energy metabolism and substrate oxidation rates: A randomized clinical trial

Rationale: Green (Camellia sinensis;CS) and hibiscus (Hibiscus sabdariffa;HS) teas have bioactive compounds such as catechins and anthocyanins respectively1,2, which have been suggested in the treatment of obesity3. This study aims to evaluate the acute effect of CS and HS tea ingestion on energy expenditure (EE), respiratory quotient (RQ) and oxidized substrate (OS) rates in healthy individuals.