Almanac A1C

Tea: Nature’s Metabolic Health Elixir

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dr. Karunia Valeriani Japar

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Introduction

Tea is one of the most widely consumed beverages globally and has long been associated with health-promoting properties, particularly in relation to metabolic health. Current evidence highlights that tea, notably green, oolong, and white varieties, contains diverse bioactive compounds, including polyphenols such as catechins and epigallocatechin gallate (EGCG), which exert potent antioxidant, anti-inflammatory, and metabolic regulatory effects. These mechanisms underpin tea’s benefit for weight management, insulin sensitivity, lipid metabolism, and overall cardiometabolic risk reduction [1,2,3,4,5,6].

Recent clinical experimental studies reveal that regular tea consumption may support improvement in multiple markers of metabolic syndrome, such as body weight, body fat, waist circumference, and blood pressure, glycemic control, and cholesterol levels. These effects are attributed to tea’s ability to enhance thermogenesis, modulate gut microbiota, and regulate cellular pathways involved in inflammation and lipid handling. Epidemiological data consistently link tea intake with lowered prevalence of diabetes, cardiovascular disease, and related chronic disorders [1,3,6,7,8].

As interest grows in evidence-based interventions for metabolic disease prevention, scientific understanding of tea’s biological activities and clinical potential continues to expand. This article will examine the molecular mechanisms and human studies supporting tea’s role in metabolic health, providing a foundation for clinical recommendations and health technology applications in preventive medicine [6,7].

Chemical Composition and Antioxidant Properties

Tea (Camellia sinensis) contains a rich array of bioactive compounds, with polyphenols constituting the predominant chemical class responsible for its health promoting effects. The polyphenolic composition varies significantly across tea types depending on the degree of fermentation during processing [9,10].

Polyphenolic Composition

Green Tea Catechins

Green tea, which undergoes minimal fermentation, is characterized by a high content of catechins, flavanol monomers that comprise approximately 30% of the dry leaf weight. Catechins belong to the flavan-3-ol class of flavonoids and possess a benzopyran skeleton with a phenyl group substituted at the 2-position and a hydroxyl or ester function at the 3-position. The major catechins identified in green tea include [9]:

  • (-)-Epigallocatechin-3-gallate (EGCG): the most abundant catechin, accounting for 50-70% of total catechin content [11,12]
  • (-)-Epigallocatechin (EGC)
  • (-)-Epicatechin-3-gallate (EGC)
  • (-)-Epicatechin (EC)
  • (+)-Catechin (C )
  • (+)-Gallocatechin (GC) [10]

EGCG represents the principal bioactive compound, with concentrations ranging from 23.29 to 70.22 mg/g in commercial green tea products. The molecular formula of EGCG is C22H18O11 with a molecular weight of 458.40 Da. Its structure features multiple hydroxyl groups on both B-ring (gallocatechin moiety) and D-ring (galloyl residue), which are critical determinants of its antioxidant capacity [12,13,14,15,16].

Black Tea Polyphenols

Black tea undergoes complete fermentation, during which catechins are enzymatically oxidized to form more complex polyphenolic compounds. The major oxidation products include:

  • Teaflavins (TF): orange-red dimericcompounds comprising 3-6% of black tea extract solids, formed by co-oxidation of paired catechins [17,18].
  • Thearubigins (TR): red-brown polymeric compounds accounting for 20-60% of extract solids [18,19]
  • Theabrownins (TB): polymerized thearubigins linked with proteins [19].

The four principals theaflavins are theaflavin, theaflavin-3-monogallate, theaflavin-3’-monogallate, and theaflavin-3,3’-digallate. These compounds retain significant antioxidant properties comparable to catechins, with theaflavins demonstrating enhanced superoxide radical scavenging capacity, approximately 10 times faster than EGCG [18].

Antioxidant Mechanisms

Tea polyphenols exert antioxidant effects through multiple complementary mechanisms, functioning both as direct free radical scavengers and as the modulators of endogenous antioxidant systems [16,20].

Direct Free Radical Scavenging

The antioxidant activity of catechins drives from their structural characteristics, particularly the number and position of. Hydroxyl groups. The p-electron system on the benzene ring exhibits conjugation with the single electron on the oxygen atom of phenolic hydroxyl groups, thereby reducing the activity of the hydrogen-oxygen bond and increasing hydrogen availability for reaction with free radical. This process enables tea polyphenols to react with reactive oxygen species (ROS) to form relatively stable phenolic oxygen radicals, effectively terminating free radical chain reactions [16,20].

The gallocatechin moiety and galloyl residue in EGCG are particularly important for antioxidant activity, with compounds containing these structural features demonstrating superior AMPK activation and free radical scavenging capacity. Additionally, EGCG possesses metal chelating properties that reduce oxidation through chelation of transition metal ions [13,16,20,21].

Modulation of Endogenous Antioxidant System

Beyond direct scavenging, tea polyphenols enhance cellular antioxidant defenses by regulating the activity and expression of antioxidant enzymes. Key mechanisms include:

  1. Inhibition of Pro-oxidant Enzymes: Tea polyphenols suppress xanthine oxidase, NADPH oxidase, lipoxygenase, and cyclooxygenase activities, thereby reducing ROS generation [20, 22].
  2. Activation of Antioxidant Enzymes: Tea polyphenols upregulate superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), calatase (CAT), glutathione S-transferase (GST), and glutathione reductase (GR), strengthening cellular antioxidant capacity [16,20].
  3. Nrf2-ARE Pathway Activation: EGCG and other catechins activate the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway through phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) and mitogen-activated protein kinase (MAPK) pathways. Nrf2 activation induces expression of phase II detoxifying enzymes including heme oxygenase-1 (HO-1), NAD(P)H quinone oxidoreductase (NQO1), and GST, which collectively reduce oxidative stress and protect against cellular damage [16,20,23].

Mechanisms of Tea for Metabolic Health

Enhancement of Insulin Sensitivity and Glucose Metabolism

Tea polyphenols improve insulin sensitivity and glucose homeostasis through multiple molecular pathways. Animal studies demonstrate that green tea extract significantly decreases fasting plasma glucose, insulin, triglycerides, and free fatty acids, while enhancing insulin stimulated glucose uptake in adipocytes. These effects involve both insulin potentiating properties and reduction of oxidative stress associated with insulin resistance [24,25,26].

In human trials, green tea supplementation has shown variable effects on glycemic parameters. While some studies report improvements in fasting glucose and insulin sensitivity markers, others indicate more complex relationship. A large study in Chinese adults with high diabetes risk found that tea consumption was associated with higher glucose levels during oral glucose tolerance testing, potentially reflecting altered pancreatic b-cell function and insulin secretion pattens rather than direct adverse effects, these divergent findings underscore the importance of population characteristics, baseline metabolic status and medication use in determining individual responses to tea intervention [25,27,28,29].

The mechanisms underlying glucose-lowering effects include enhanced cellular glucose uptake, improved insulin receptor sensitivity, and modulation of hepatic glucose production pathways [25,30].

AMPK Pathway Activation

A central mechanism by which tea polyphenols regulate metabolic health involves activation of AMP-activated protein kinase (AMPK), a master regulator of cellular energy homeostasis. Catechins, particularly EGCG, induce phosphorylation of both LKB1 (liver kinase B1), a tumor suppressor protein a major AMPK upstream kinase, and AMPa itself leading to increased AMPK activity in liver, muscle, and adipose tissues [21,31,32,33].

The structural specificity for AMPK activation requires either a gallocatechin moiety or a galloyl residue, with reactive oxygen species serving as mediators of EGCG-induced LKB1/AMPK pathway activation. Once activated, aMPK phosphorylates downstream targets including acetyl-CoA carboxylase (ACC), leading to its inhibition and consequent reduction in fatty acid synthesis [21,34].

AMPK activation by tea polyphenols produces several metabolic benefits:

  1. Enhanced Glucose metabolism: AMPK stimulates glucose transporter expression in muscle tissue, facilitating glucose uptake and utilization, thereby improving blood glucose control [34].
  2. Increased Fatty Acid Oxidation: AMPK activation promotes b-oxidation of fatty acids in both mitochondria and peroxisomes while suppressing lipogenesis. Studies in chicken liver demonstrate that green tea polyphenols enhance phosphorylation of AMPKa and ACACA, alter expression of lipid-metabolizing enzymes, reduce hepatic lipid content, and decrease abdominal fat mass [34,35].
  3. Inhibition of Gluconeogenesis: in hepatocytes, AMPK suppresses gluconeogenesis and fatty acid synthesis, helping maintain hepatic energy balance [31].
  4. Mitochondrial Biogenesis: AMPK regulates mitochondrial biogenesis and function, thereby enhancing cellular energy production capacity [36].

Thermogenesis and Fat Oxidation

Green tea extract rich in catechin polyphenols significantly increases 24 hour energy expenditure and fat oxidation beyond effects attributable to caffeine alone. In controlled human studies, green tea extract (containing 50 mg caffeine and 90 mg EGCG per dose) increased 24-hour energy expenditure by 4% and decreased respiratory quotient from 0.88 to 0.85, indicating enhanced fat oxidation. Urinary norepinephrine excretion was elevated by 40%, suggesting sympathetic nervous system activation as a primary mechanism [37,38].

Meta-analysis of multiple trials confirms dose-dependent effects, with catechin-caffeine mixtures increasing daily energy expenditure by approximately 0.53 kJ per mg administered and fat oxidation by 0.02 g per mg. importantly, caffeine only supplementation did not significantly increase fat oxidation, indicating that catechin polyphenols are essential for the fat oxidizing effects [37,38].

The thermogenic and fat oxidative properties of tea polyphenols operate through sympathetic activation, potentially involving inhibition of catechol-O-methyltransferase (COMT), which prolongs the action of norepinephrine. These mechanisms contribute to body composition improvements and metabolic rate maintenance during weight loss interventions [37,38,39,40].

Lipid Metabolism Regulation

Tea consumption exerts favorable effects on lipid profiles through multiple mechanisms, meta-analysis of 31 randomized controlled trials involving 3,321 subjects demonstrates that green tea supplementation significantly lowers total cholesterol (TC) by 4.66mg/dL and low-density lipoprotein (LDL) cholesterol by 4.55 mg/dL compared to control groups, these effects occur in both normal weight and overweight/obese individuals [42].

The mechanisms underlying lipid lowering effects include:

  1. Inhibition of Lipid Synthesis: Tea catechins suppress expression of lipogenic enzymes including fatty acid synthase (FAS) and ACC, reducing hepatic and adipose tissue lipogenesis [35,40,43].
  2. Enhanced Fatty Acid bOxidation: Tea polyphenols upregulate expression of genes encoding acyl-CoA oxidase (ACO), acyl-CoA synthetase long-chain (ACSL), and fatty acid binding protein (FABP), facilitating mitochondrial and peroxisomal fatty acid oxidation, different tea polyphenols activate distinct pathways: teaflavins and epitheaflagallin activate mitochondrial fatty acid oxidation, while EGCG preferentially activates peroxisomal b-oxidation [31,35,44].
  3. Interference with Intestinal Lipid Absorption: EGCG reduces micellar solubility of lipids and interferes with intestinal micelle absorption, thereby limiting dietary fat uptake.
  4. Modulation of Cholesterol Metabolism: Tea polyphenols may influence hepatic cholesterol synthesis, bile acid production, and cholesterol excretion pathways [43,45].

Black tea consumption specifically demonstrates protective effects on systolic blood pressure, while green tea reduces LDL cholesterol levels, particularly in individuals with body mass index (BMI) ≥28. These differential effects may reflect varying polyphenolic compositions between tea types [29,35].

Anti-Inflammatory Effects

Chronic low-grade inflammation is hall mark of metabolic syndrome and related disorders. Tea polyphenols, particularly EGCG, exhibit potent anti-inflammatory properties by suppressing inflammatory cytokine expression and modulating inflammatory signaling pathways [46,47,48].

Meta-analysis of 12 randomized controlled trials reveals that green tea supplementation significantly reduces circulating tumor necrosis factor-alpha (TNF-a) levels in patients with metabolic syndrome and related disorders, although effects on C-reactive protein (CRP) and interleukin-6 (IL-6) did not reach statistical significance. TNF-a plays a central role in insulin resistance, atherogenesis, and non-alcoholic fatty liver disease pathogenesis [48].

The anti-inflammatory mechanisms include:

  1. Nf-kB Pathway Inhibition: Tea polyphenols act as antioxidants to scavenge reactive oxygen species, leading to attenuation of nuclear factor-kB (NF-kB) activity and subsequent reduction in inflammatory cytokine expression [47].
  2. Suppression of Inflammatory Enzymes: Green tea and EGCG suppress gene and protein expression of cyclooxygenases, matrix metalloproteinases, and other inflammation related enzymes [47].
  3. Modulation of Inflammatory Signaling: Tea polyphenols influence MAPK and PI3K/AKT signaling pathways, which regulate inflammatory responses [46].

The anti-inflammatory effects of tea contribute to its protective roles against cardiovascular disease, diabetes, and obesity-related metabolic complications [47,48,49].

Gut microbiota Modulation

Emerging evidence indicates that tea polyphenols exert significant effects on metabolic health through modulation of the gut microbiome. Most ingested polyphenols (80-90%) are not absorbed in the small intestine and instead reach the colon, where they undergo extensive microbial biotransformation [50,51].

Bidirectional Tea-Microbiota Interactions

  1. Microbial Metabolism of Tea Polyphenols: Gut bacteria transform catechins through C-ring cleavage, dihydroxylation, and A-ring cleavage to produce hydroxyphenyl-c-valerolactones and smaller phenolic acids including 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, and hydrophenylpropionic acid. These microbial metabolites exhibit biological activities and contribute to the systemic health effects of tea consumption [50,51].
  2. Modulation of Microbiota Composition: Tea polyphenols alter gut microbial community structure by promoting growth of beneficial species while inhibiting pathogenic bacteria. In. metabolic syndrome patients, tea consumption influences the abundance of major phyla including Firmicutes, Bacteroidota, and Proteobacteria. These compositional changes correlate with improvement in metabolic parameters [50,52,53].
  3. Metabolic Pathway Alterations: Tea polyphenol treatment modifies microbial metabolic pathways, including decreased carbohydrate energy scavenging reduced bile acid synthesis and fatty acid absorption, increased hexose and vitamin production and altered amino acid metabolism. These metabolic shifts in the gut microbiome have systemic complications for host energy balance and metabolic health [50,53].

The interplay between tea polyphenols and gut microbiota represents a critical mechanism underlying tea’s metabolic benefits, with individual variations in gut microbial composition potentially explaining inter-individual differences in response to tea consumption [51,54].

Clinical Evidence in Metabolic Syndrome

Recent systematic reviews and meta-analysis of randomized controlled trials provide robust evidence for tea’s beneficial effects on metabolic syndrome components. Analysis of 24 RCTs demonstrates that tea consumption significantly improves body weight, body mass index (BMI), and waist circumference in individual with metabolic syndrome and obesity. Different tea types exhibit specific protective mechanisms: black tea reduces systolic blood pressure, while green tea decrease LDL cholesterol and diabetes incidence, particularly in individuals with BMI ³28 [29,55].

A comprehensive meta-analysis confirms protective effects on diastolic blood pressure across all tea types and beneficial effects on BMI values. However, effects on lipid metabolism, glucose metabolism, and blood pressure indices show variability across studies, reflecting differences in tea type, dosage, intervention duration population characteristics, and concomitant medication use [29,55,56].

These clinical findings supports the integration of tea consumption as an adjunctive dietary strategy for metabolic syndrome prevention and management, although optimal dosing regimens and long-term efficacy require further investigation through carefully designed trials [29,48,55,56].

Safety Profile and Contraindications

General Safety and Adverse Effects

Tea consumption in traditional beverage forms is generally recognized as safe for most individuals, with consumption of 2-4 cups per day well tolerated across diverse populations. However, excessive tea intake, particularly exceeding 3-4 cups (710-950 mL) per day, may lead to adverse effects primarily related to caffeine and tannin content. The most commonly reported adverse effects associated with moderate to high tea consumption include gastrointestinal disturbances such as nausea, abdominal discomfort, dyspepsia, constipation, and diarrhea, particularly when tea is consumed on an empty stomach due to astringent nature of tannins that can irritate digestive tissue. Central nervous system effects attributable to caffeine include anxiety, nervousness, restlessness, insomnia, sleep disturbances and headaches, with sensitivity varying considerably among individuals. The caffeine content varies across tea types, with matcha containing the highest levels (60-80mg per 240mL cup), followed by oolong tea (38-58), black tea and chai (47-53mg), white tea (25-50mg), and green tea (29-49mg). Chronic caffeine consumption can lead to tolerance and physical dependence, with withdrawal symptoms including headaches and fatigue occurring upon discontinuation. Additionally, tea tannins can reduce iron absorption from plant-based (non-heme) iron sources by 60-90% when consumed with meals, potentially exacerbating iron deficiency in susceptible individuals. This effect is mediated by tannin binding to non-heme iron in the digestive tract, forming insoluble complexes that cannot be absorbed, although this interaction does not significantly affect heme iron from animal sources, which is absorbed at higher efficiency. Cardiovascular symptoms include increased heart rate, palpitation, and elevated blood pressure may occur with excessive caffeine intake, particularly in caffeine sensitive individual [57,58].

Drug Interactions

Tea, particularly green tea, exhibits numerous pharmacokinetic and pharmacodynamic interactions with medications that can alter drug efficacy and safety. Caffeine in tea is metabolized primarily by cytochrome P450 (CYP1A2) and several medication inhibit this enzyme, decreasing caffeine clearance and increasing risk of caffeine-related side effects including jitteriness, headache, tachycardia, and anxiety. Medications that reduce caffeine metabolism include quinolone antibiotics (e.g., ciprofloxacin, norfloxacin), cimetidine, birth control pills, verapamil, mexiletine, terbinafine, and fluvoxamine. Conversely, caffeine can alter the pharmacokinetics and effects of several medications: it blocks adenosine and dipyridamole, potentially interfering with cardiac stress test, decreases theophylline clearance, increasing theophylline effects and side effects, reduce the efficacy of carbamazepine and ethosuximide in seizure control, and may interact with monoamine oxidase inhibitors (MAOIs) to cause dangerously elevated blood pressure. Tea polyphenols, particularly catechins, can interfere with intestinal absorption of several cardiovascular and other medications by inhibiting organic anion transporting polypeptides (OATPs), drug transporters expressed in the intestine. Green tea decreases absorption and bioavailability of nadolol (beta-blocker), celiprolol (beta-blocker), atorvastatin (statin), and rosuvastatin (statin), potentially reducing their therapeutic efficacy. Green tea may interact with warfarin due to vitamin K content, although the amount in tea is small and unlikely to cause clinically significant interactions with moderate consumption, however consumption of 8 or more cups daily should be avoided in patients taking warfarin. Catechins may interact with bortezomib (chemotherapy agent) and potentially decrease its anticancer effects, necessitating avoidance of green tea products during bortezomib treatment. Green tea might enhance the effects and toxicity of 5-fluorouracil chemotherapy when consumed in large amounts. The combination of caffeine from tea with stimulant medications (amphetamines, cocaine, ephedrine) or bronchodilators (beta-adrenergic agonists) can cause excessive sympathetic stimulation, leading to serious cardiovascular complications including tachycardia and hypertension. Tea polyphenols inhibit cytochrome P450 3A4 (CYP3A4), potentially altering metabolism of numerous medications metabolized by this enzyme. Green tea may interact with riluzole by decreasing its metabolism and increasing its effects and side effects. Additionally, caffeine can affect blood glucose levels in unpredictable ways, potentially requiring adjustment of diabetes medication dosage [59].

Contraindications and Special Populations

Several populations require special consideration or limitations regarding tea consumption due to increased vulnerability to adverse effects.

  • Pregnancy and Lactation: Caffeinated teas (black, green, white, matcha, chai, oolong) are generally considered safe during pregnancy when consumed in moderation, with most health authorities recommending limitation of total daily caffeine intake to maximum of 200-300 mg per day during pregnancy. Caffeine easily crosses the placenta, and the fetal liver has limited capacity to metabolize it, excessive caffeine exposure during pregnancy is associated with increased risk of preterm birth, low birth weight, birth defects, miscarriage, and stillbirth. Certain women with genetic variants affecting caffeine metabolism may have substantially higher miscarriage risk (2.4-fold increased risk) even with moderate caffeine intake (100-300 mg/day), suggesting that particularly sensitive individuals should further limit consumption. During breastfeeding, caffeine is excreted into breast milk and may cause irritability, poor sleep, and fussiness in infants. Most herbal teas lack adequate safety data for pregnancy and lactation. However ginger tea (up to 1-gram dried ginger per day), peppermint tea, raspberry leaf tea (particularly in late pregnancy), and lemon balm tea are considered likely or possibly safe. Raspberry leaf and peppermint teas should be avoided in the first trimester due to potential uterine stimulation and menstrual flow effects. Chamomile tea has been associated with higher rates of preterm labor and miscarriage in some reports and should be consumed with caution or avoided in large quantities during pregnancy.
  • Iron Deficiency: Individuals with iron deficiency anemia or at high risk for iron deficiency (including menstruating women, pregnant women, growing children, and strict vegetarians. Vegans) should exercise caution with tea consumption due to tannin-mediated inhibition of non-heme iron absorption. To minimize iron absorption interference, tea should be consumed between meals rather than with iron-rich foods, with this timing modification reducing iron absorption inhibition from 60-70% to approximately 20%. Heavy tea consumers (3-6cups daily) in high-risk populations may require iron supplementation or dietary modification.
  • Anxiety Disorders and Insomnia: Individuals with anxiety disorders, panic disorder, or insomnia should limit or avoid caffeinated tea consumption, particularly in the afternoon or evening, as caffeine can exacerbate anxiety symptoms and significantly disrupt sleep architecture by blocking adenosine receptors and reducing sleep duration, sleep quality, and slow-wave sleep. Caffeine should be avoided for at least 8 hours before bedtime to minimize sleep disruption.
  • Cardiovascular Conditions: Patients with arrhythmias, uncontrolled hypertension, or hypersensitivity to stmulants should limit caffeine intake due to potential cardiovascular stimulation.
  • Gastroesophageal Reflux Disease (GERD): Caffeine can increase gastric acid production and exacerbate heartburn and acid reflux symptoms in susceptible individuals. Chronic
  • Kidney Disease: While moderate tea consumption (up to 4 cups daily) appears safe and potentially beneficial in early-stage CKD (stages 1-2), patients with advanced CKD should consult healthcare providers regarding appropriate tea intake, as excessive consumption may pose risks.
  • Hepatic Impairment: Individuals with pre-existing liver disease or compromised hepatic function should avoid high dose GTE supplements due to increased hepatotoxicity risk.
  • Medication Use: Patients taking medications with potential tea interactions, particularly warfarin, cardiovascular drugs, chemotherapy agents, psychotropic medications, and medications metabolized by CYP1A2 or CYP3A4 should consult healthcare providers before consuming tea regularly or in large quantities [60,61,62].

Recommendations for Safe Consumption

To optimize safety while obtaining health benefits from tea consumption, several practical recommendations should be followed. Moderate consumption of 2-4 cups per day of traditionally prepared tea is generally safe for healthy adults and associated with. Numerous health benefits. Individuals pursuing weight loss should not combine dietary restriction or fasting with high dose green tea extract supplements due to substantially increased hepatotoxicity risk, adequate nutrition should be maintained when using EGCG containing products. Green tea extract supplements should be used in moderation, avoiding long-term use and high doses (particularly exceeding 800mg ECGC per day (with preference given to traditional tea beverages over concentrated supplements. Individuals with HLA-B*35:01 or UGT1A4 genetic variants associated with increased hepatotoxicity risk should be exercise particular caution with GTE supplements. To minimize iron absorption interference, tea should be consumed between meals rather than with iron rich foods, particularly in individuals at risk for iron deficiency. Pregnant and breastfeeding women should limit total daily caffeine intake to less than 200-300 mg and avoid herbal teas with inadequate safety data. Individuals taking medications should consult healthcare provider or pharmacists before regular tea consumption, particularly those taking warfarin, cardiovascular drugs, chemotherapy agents, or medications with narrow therapeutic windows. Patients should discontinue green tea consumption at least 24 hours before cardiac stress test involving adenosine or dipyridamole. Any individual experiencing unexplained symptoms potentially elevated liver enzymes, severe anxiety, sleep disturbances, or cardiovascular symptoms, should reduce or discontinue tea intake and seek medical evaluation [58,59,63,64,65].

Conclusion

Tea, particularly its green, oolong, and white varieties, is rich in bioactive polyphenols like catechins and EGCG, which deliver potent antioxidant, anti-inflammatory and metabolic syndrome, such as body weight, waist circumference, blood pressure, glucose control, improve insulin sensitivity, modulated lipid metabolism and beneficial effects on gut microbiota. These molecular actions collectively contribute to tea’s ability to lower the risk of diabetes, cardiovascular disease, and related chronic disorders.

Clinically, tea can be safe adjunct to dietary and preventive strategies for metabolic health when consumed in moderation (2-4 cups daily). However, excessive intake, especially from supplements, can have adverse effects due to caffeine and tannins, and may interact with certain medication. For vulnerable populations, such as pregnant or breastfeeding women, individuals with iron deficiency or cardiovascular conditions, or those taking specific drugs, special considerations and timing modifications are recommended. Overall, the integration of tea into balanced lifestyle is supported by substantial scientific evidence, positioning it as a practical and effective approach to promoting metabolic health and reducing cardiometabolic risk.

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