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Black Tea Extract (Camellia sinensis)

Camellia sinensis
Evidence Level
Moderate
7 Clinical Trials
5 Documented Benefits
3/5 Evidence Score

Black tea comes from the same plant as green tea (Camellia sinensis), but its leaves are rolled and left to oxidize, a step the tea trade calls fermentation even though no microbes are involved. During this enzymatic oxidation, catechins in the leaf are converted into theaflavins and the larger, less understood thearubigins, which give black tea its color (theaflavins on their own have a separate page). Black tea extracts concentrate these polyphenols and often keep the tea's natural caffeine unless labeled decaffeinated. Most of the encouraging human research used black tea as a drink, either leaf tea or dissolved tea powder, at about 2 to 5 cups a day: pooled trials show small drops in blood pressure and better blood-vessel dilation. Capsule extracts have a thinner record, including null results for cholesterol and long-term blood sugar. Black tea also strongly reduces iron absorption from a meal.

Studied Dose Beverage trials: about 2 to 5 cups of black tea a day (pooled blood-pressure trials averaged 4 to 5 cups). Capsule or tablet extract trials (roughly 75 to 1,000 mg/day) gave mixed or null results. Check each product's theaflavin and caffeine content.
Active Compound Black tea polyphenols: theaflavins and thearubigins (formed when tea catechins oxidize during processing), remaining catechins and flavonols, plus naturally occurring caffeine unless the extract is decaffeinated.

Benefits

Blood pressure with regular black tea drinking

Two meta-analyses of randomized trials found that drinking black tea regularly lowered blood pressure slightly: about 1 to 2 mmHg systolic and 0.6 to 1.3 mmHg diastolic versus control drinks. These are small shifts in a risk marker, not proof of fewer heart attacks or strokes, and most trials tested the drink rather than capsules. One meta-analysis was funded by a company that sold tea.

Supported by Trial 1, Trial 3

Endothelial function and blood vessel dilation

Flow-mediated dilation measures how well an artery widens. A meta-analysis of 9 placebo-controlled studies, mostly of black tea, found 2 to 3 cups a day raised it by 2.6 percentage points, and a crossover in 19 men showed a dose-response. Results were not uniform: a 6-month trial of 3 cups a day found no change. The meta-analysis authors worked for a company that sold tea.

Supported by Trial 2, Trial 3

Cholesterol and blood lipids

The lipid trials give mixed results. A Cochrane review of a few small trials and a meta-analysis of 10 trials found black tea lowered LDL cholesterol slightly, but a meta-analysis of 15 trials found no significant change in total or HDL cholesterol, and its LDL drop held in only one of two statistical models. Purified theaflavin capsules, with or without catechins, did not lower LDL in 102 adults over 11 weeks.

Supported by Trial 5, Trial 1

Blood sugar after a sugary drink

In a small study of 24 adults with normal or prediabetic blood sugar, a single black tea drink lowered the glucose rise after a sugar drink versus placebo, with no change in insulin. Longer studies were less encouraging: 3 cups a day for 6 months did not change fasting glucose, and a green and black tea extract did not improve HbA1c in people with type 2 diabetes.

Supported by Trial 4, Trial 6

Body weight and waist measures

In a 6-month trial of 111 regular tea drinkers, 3 cups a day of black tea powder led to slightly less weight gain (0.64 kg) and a smaller waist (1.9 cm) at 3 months compared with a caffeine-matched placebo drink, but neither difference was still significant at 6 months. This is a single trial, so black tea is not an established weight-management tool.

Supported by Trial 4

Mechanism of action

1

Oxidized tea polyphenols

When black tea leaves oxidize, the catechins that dominate green tea are joined into theaflavins and the larger thearubigins, which are the most abundant black tea polyphenols. Thearubigins are a highly mixed group and are much less studied, so it is unclear which compounds drive the effects seen in tea drinkers.

2

Effects on the blood-vessel lining

In patients with coronary artery disease, black tea improved artery widening that depends on the vessel lining (the endothelium) but not widening triggered by nitroglycerin, and a 200 mg dose of caffeine alone had no acute effect. This points to the tea flavonoids acting on the endothelium itself rather than to caffeine.

3

Binding iron in the gut

Black tea polyphenols reduce the absorption of non-heme iron (the form in plant foods, fortified foods and most supplements) eaten at the same meal, and the effect grows with the drink's polyphenol content. This is a drawback for people who need iron rather than a benefit.

Clinical trials

1
Black Tea and Blood Pressure: Meta-Analysis of 11 Placebo-Controlled Studies
PubMed

Systematic review and meta-analysis of placebo-controlled black tea intervention studies lasting at least 1 week, funded by Unilever, which employed four of the authors (Greyling et al. 2014, PLoS One).

11 studies, 12 intervention arms, 378 adults; about 4 to 5 cups of black tea a day, as leaf tea in 6 studies and dissolved tea extract powder in 5.

Systolic pressure fell by 1.8 mmHg (95% CI 0.7 to 2.8) and diastolic by 1.3 mmHg (95% CI 0.8 to 1.8) versus placebo. Powder studies showed larger systolic drops than leaf-tea studies, and effects were larger at higher starting blood pressure. These were beverage trials, not capsule supplements, and the effect is small.

2
Tea and Flow-Mediated Dilation: Meta-Analysis of 9 Studies
PubMed

Meta-analysis of placebo-controlled human intervention studies of tea on brachial artery flow-mediated dilation (FMD), written by Unilever employees (Ras et al. 2011, PLoS One).

9 studies (15 arms) in healthy people and patient groups; 7 studies tested black tea and 3 tested green tea; median 500 mL of tea a day (2 to 3 cups).

Tea raised FMD by 2.6 percentage points (95% CI 1.8 to 3.3) versus placebo, with significant heterogeneity between studies. FMD is a marker of blood-vessel function, not a clinical outcome. All studies tested brewed or dissolved tea drinks.

3
Black Tea Dose-Response for Flow-Mediated Dilation: Crossover in 19 Men
PubMed

Randomized, double-blind, controlled crossover of black tea providing 0, 100, 200, 400 and 800 mg tea flavonoids a day, each for 1 week (Grassi et al. 2009, J Hypertens).

19 healthy men.

FMD rose in step with dose, from 7.8% on control to 9.0, 9.1, 9.6 and 10.3% across the four doses, and even the lowest dose differed from control. Office blood pressure also fell (by 2.6 mmHg systolic and 2.2 mmHg diastolic), as did an arterial stiffness index, with no change in the other measures studied. A short beverage study in a small group of healthy men.

4
Six Months of Black Tea: Weight, Glucose, Lipids and Endothelial Function (RCT)
PubMed

Randomized, double-blind, 6-month parallel trial of 3 cups a day of powdered black tea solids versus a flavonoid-free, flavor- and caffeine-matched placebo drink (Bøhn et al. 2014, Food Funct).

111 regular tea-drinking men and women with BMI 20 to 35.

At 3 months the tea group gained less weight (-0.64 kg) and had a smaller waist (-1.88 cm) than placebo, but these differences were no longer significant at 6 months. There were no significant effects on fasting glucose, insulin, blood lipids or endothelial function. The authors note this same trial earlier reported a blood-pressure benefit not explained by caffeine.

5
Theaflavin Capsules and Cholesterol: Null Placebo-Controlled RCT
PubMed

Randomized, double-blind, placebo-controlled parallel trial of once-daily capsules of purified black tea theaflavins or theaflavins plus catechins for 11 weeks (Trautwein et al. 2010, Eur J Nutr).

102 adults with mildly to moderately raised cholesterol (67 men, 35 women).

Neither theaflavins alone (77.5 mg/day) nor theaflavins with catechins (75 mg theaflavins, 150 mg catechins, 195 mg other polyphenols) lowered total or LDL cholesterol versus placebo; cholesterol drifted down in the placebo group too. This tested a supplement extract, not brewed tea.

6
Black Tea Drink and Post-Meal Blood Sugar: Crossover in 24 Adults
PubMed

Randomized, double-blind, placebo-controlled crossover of a single black tea drink taken with a sucrose load (Butacnum et al. 2017, Asia Pac J Clin Nutr).

24 adults aged 20 to 60 with normal or prediabetic blood sugar.

Drinks with 110 or 220 mg of black tea polymerized polyphenols lowered the blood glucose area under the curve over the first 60 minutes versus placebo; insulin responses did not differ. A one-off test of a beverage, not evidence of long-term blood sugar control.

7
Green and Black Tea Extract and HbA1c: Null 3-Month RCT
PubMed

Double-blind, placebo-controlled, randomized trial of a combined green and black tea extract at 0, 375 or 750 mg/day for 3 months (Mackenzie et al. 2007, Metabolism).

49 adults (study completers) with type 2 diabetes not using insulin, average age 65; 80% used glucose-lowering medication.

HbA1c, the primary outcome, rose slightly in all arms (+0.4 placebo, +0.3 at 375 mg, +0.5 at 750 mg) with no difference between groups. The authors found no glucose-lowering effect of the extract.

Side effects and drug interactions

Common Potential side effects

Caffeine: black tea typically supplies about 71 mg of caffeine per 12 fl oz, and extracts range from caffeinated to decaffeinated. Caffeine can cause jitteriness, a fast heartbeat, stomach upset or poor sleep. FDA cites 400 mg a day from all sources as an amount not generally linked to negative effects for most adults.
Iron absorption: in one absorption study, black tea drunk with a bread meal cut non-heme iron absorption by 79 to 94%. People with low iron stores, vegetarians and vegans, and anyone taking iron should take black tea or its extract between meals, about an hour or more after eating.
Concentrated extracts have far less safety data than brewed tea; take them with food and follow the label dose.
Pregnancy and breastfeeding: count the caffeine and talk with a health care provider; extracts have not been studied in pregnancy.

Important Drug interactions

Iron supplements: black tea polyphenols reduce non-heme iron absorption; take iron and black tea or its extract at different times.
Stimulant medications and other caffeine sources: caffeine in non-decaffeinated extracts adds to the effects of stimulants, pre-workouts and energy drinks.
Medicines that slow caffeine clearance (for example some antibiotics and antidepressants) can raise caffeine levels; ask a pharmacist if you take a caffeinated extract alongside them.
Blood pressure, cholesterol and diabetes medicines: the small effects seen in tea trials are no substitute for prescribed treatment; tell your clinician if you start a concentrated extract.

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Frequently asked questions about Black Tea Extract (Camellia sinensis)

Is a black tea extract the same as drinking black tea?

Not quite. Most of the encouraging research on blood pressure and blood-vessel function used black tea as a drink, either brewed leaf tea or tea powder dissolved in water, at about 2 to 5 cups a day. Capsule extracts vary widely in their theaflavin, thearubigin and caffeine content, and the extract trials run so far on cholesterol and long-term blood sugar mostly found no effect.

How much caffeine is in black tea and black tea extract?

FDA lists a typical 12 fl oz serving of black tea at about 71 mg of caffeine, roughly double green tea and well below brewed coffee. Extracts differ: some keep the natural caffeine and some are decaffeinated, and decaffeinated tea products still contain a little. Check the label and count caffeine from all sources.

Does black tea affect iron absorption?

Yes. In absorption studies, black tea drunk with a bread meal cut non-heme iron absorption by 79 to 94%, and adding milk made little difference. Waiting an hour after a meal before drinking tea roughly halved the effect in one study. If you have low iron or take an iron supplement, keep black tea and its extracts away from iron-rich meals and iron pills.

How is black tea extract different from theaflavins or green tea extract?

Green tea extract is rich in catechins such as EGCG because the leaves are not oxidized. Black tea extract contains the products of oxidation, mainly thearubigins plus a smaller share of theaflavins. A theaflavin supplement is a more purified fraction of black tea; see the theaflavins and green tea pages for those ingredients.

What is Black Tea Extract?

Black tea comes from the same plant as green tea (Camellia sinensis), but its leaves are rolled and left to oxidize, a step the tea trade calls fermentation even though no microbes are involved.

What is Black Tea Extract used for?

Black Tea Extract is researched primarily for Cardiovascular and Metabolic Health. Two meta-analyses of randomized trials found that drinking black tea regularly lowered blood pressure slightly: about 1 to 2 mmHg systolic and 0.6 to 1.3 mmHg diastolic versus control drinks.

What is the recommended dosage of Black Tea Extract?

The clinically studied dose is Beverage trials: about 2 to 5 cups of black tea a day (pooled blood-pressure trials averaged 4 to 5 cups). Capsule or tablet extract trials (roughly 75 to 1,000 mg/day) gave mixed or null results. Check each product's theaflavin and caffeine content. Always follow the product label and check with a healthcare provider for personal advice.

Is Black Tea Extract safe, and does it have side effects?

For most healthy adults, Black Tea Extract is well tolerated at studied doses. Reported effects can include: Caffeine: black tea typically supplies about 71 mg of caffeine per 12 fl oz, and extracts range from caffeinated to decaffeinated. Caffeine can cause jitteriness, a fast heartbeat, stomach upset or poor sleep. It may also interact with some medications. Black Tea Extract is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Black Tea Extract interact with any medications?

Possible interactions include: Iron supplements: black tea polyphenols reduce non-heme iron absorption; take iron and black tea or its extract at different times. Stimulant medications and other caffeine sources: caffeine in non-decaffeinated extracts adds to the effects of stimulants, pre-workouts and energy… If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Black Tea Extract?

NutraSmarts rates the evidence for Black Tea Extract as Moderate (3 out of 5). It is backed by 7 clinical trials and 17 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(17 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Greyling A, Ras RT, Zock PL, Lorenz M, Hopman MT, Thijssen DH, Draijer R. The effect of black tea on blood pressure: a systematic review with meta-analysis of randomized controlled trials. PLoS One. 2014;9(7):e103247. doi: 10.1371/journal.pone.0103247.PubMedUsed to support: Meta-analysis of 11 placebo-controlled studies (378 adults, about 4 to 5 cups of black tea a day for at least 1 week): systolic pressure fell by 1.8 mmHg and diastolic by 1.3 mmHg versus placebo. Studies using dissolved tea extract powders found larger systolic drops than leaf-tea studies. Funded by Unilever, which employed four of the authors.
  2. Ma C, Zheng X, Yang Y, Bu P. The effect of black tea supplementation on blood pressure: a systematic review and dose-response meta-analysis of randomized controlled trials. Food Funct. 2021;12(1):41-56. doi: 10.1039/d0fo02122a.PubMedUsed to support: Dose-response meta-analysis of 13 randomized trials (22 study arms): black tea lowered systolic pressure by 1.04 mmHg and diastolic by 0.59 mmHg versus control. A nonlinear dose-response analysis found no significant influence of flavonoid dose or study duration.
  3. Hartley L, Flowers N, Holmes J, Clarke A, Stranges S, Hooper L, Rees K. Green and black tea for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2013;2013(6):CD009934. doi: 10.1002/14651858.CD009934.pub2.PubMedUsed to support: Cochrane review of 11 trials lasting at least 3 months (4 of black tea). Black tea lowered LDL cholesterol (mean difference -0.43 mmol/L) and systolic pressure (-1.85 mmHg); the diastolic confidence interval crossed zero. Only a few small trials at risk of bias contributed, no trial reported heart attacks or strokes, and the authors urged caution.
  4. Bøhn SK, Croft KD, Burrows S, Puddey IB, Mulder TP, Fuchs D, Woodman RJ, Hodgson JM. Effects of black tea on body composition and metabolic outcomes related to cardiovascular disease risk: a randomized controlled trial. Food Funct. 2014;5(7):1613-20. doi: 10.1039/c4fo00209a.PubMedUsed to support: Double-blind 6-month trial in 111 regular tea drinkers: 3 cups a day of powdered black tea solids versus a caffeine-matched placebo drink. At 3 months the tea group gained less weight (-0.64 kg) and had smaller waists (-1.88 cm), but these effects were no longer significant at 6 months; fasting glucose, insulin, blood lipids and endothelial function did not change.
  5. Ras RT, Zock PL, Draijer R. Tea consumption enhances endothelial-dependent vasodilation; a meta-analysis. PLoS One. 2011;6(3):e16974. doi: 10.1371/journal.pone.0016974.PubMedUsed to support: Meta-analysis of 9 placebo-controlled studies (15 arms; 7 studies tested black tea, 3 also or only green tea): tea raised brachial flow-mediated dilation by 2.6 percentage points at a median 500 mL a day (2 to 3 cups), with significant heterogeneity between studies. All authors were Unilever employees.
  6. Grassi D, Mulder TP, Draijer R, Desideri G, Molhuizen HO, Ferri C. Black tea consumption dose-dependently improves flow-mediated dilation in healthy males. J Hypertens. 2009;27(4):774-81. doi: 10.1097/HJH.0b013e328326066c.PubMedUsed to support: Randomized, double-blind crossover in 19 healthy men: black tea providing 0, 100, 200, 400 or 800 mg tea flavonoids a day, each for 1 week, raised flow-mediated dilation in a dose-dependent way (7.8% on control to 10.3% at 800 mg). Office systolic and diastolic blood pressure (by 2.6 and 2.2 mmHg) and an arterial stiffness index also fell, with no change in the other measures studied.
  7. Duffy SJ, Keaney JF Jr, Holbrook M, Gokce N, Swerdloff PL, Frei B, Vita JA. Short- and long-term black tea consumption reverses endothelial dysfunction in patients with coronary artery disease. Circulation. 2001;104(2):151-6. doi: 10.1161/01.cir.104.2.151.PubMedUsed to support: Randomized crossover in patients with coronary artery disease (66 randomized, 50 analyzed): 450 mL of black tea acutely, and 900 mL a day for 4 weeks, improved endothelium-dependent flow-mediated dilation while water did not, with no effect on nitroglycerin-induced dilation. A 200 mg dose of caffeine alone had no acute effect.
  8. Wang D, Chen C, Wang Y, Liu J, Lin R. Effect of black tea consumption on blood cholesterol: a meta-analysis of 15 randomized controlled trials. PLoS One. 2014;9(9):e107711. doi: 10.1371/journal.pone.0107711.PubMedUsed to support: Meta-analysis of 15 randomized trials: black tea did not significantly lower total cholesterol or change HDL. LDL in healthy participants fell by 5.57 mg/dL in a fixed-effects model but not significantly in a random-effects model, and there was no dose effect. The authors concluded black tea might not benefit blood cholesterol.
  9. Trautwein EA, Du Y, Meynen E, Yan X, Wen Y, Wang H, Molhuizen HO. Purified black tea theaflavins and theaflavins/catechin supplements did not affect serum lipids in healthy individuals with mildly to moderately elevated cholesterol concentrations. Eur J Nutr. 2010;49(1):27-35. doi: 10.1007/s00394-009-0045-7.PubMedUsed to support: Randomized, double-blind, placebo-controlled capsule trial in 102 adults with mildly to moderately raised cholesterol: purified black tea theaflavins (77.5 mg/day) or theaflavins plus catechins (75 mg theaflavins, 150 mg catechins, 195 mg other polyphenols) for 11 weeks did not lower total or LDL cholesterol versus placebo. The first author was from Unilever R&D.
  10. Fujita H, Yamagami T. Antihypercholesterolemic effect of Chinese black tea extract in human subjects with borderline hypercholesterolemia. Nutr Res. 2008;28(7):450-6. doi: 10.1016/j.nutres.2008.04.005.PubMedUsed to support: Double-blind randomized 3-month study in 47 adults with borderline high cholesterol: tablets of a water extract of Pu-erh tea (333 mg three times daily before meals) were followed by lower total and LDL cholesterol, triglycerides and weight compared with baseline. The abstract reports changes from baseline rather than a comparison with placebo, and the first author worked for a Japanese supplement company.
  11. Butacnum A, Chongsuwat R, Bumrungpert A. Black tea consumption improves postprandial glycemic control in normal and pre-diabetic subjects: a randomized, double-blind, placebo-controlled crossover study. Asia Pac J Clin Nutr. 2017;26(1):59-64. doi: 10.6133/apjcn.112015.08.PubMedUsed to support: Randomized, double-blind crossover in 24 adults with normal or prediabetic blood sugar: a black tea drink with 110 or 220 mg of black tea polymerized polyphenols, taken with a sucrose drink, lowered the blood glucose rise over the first hour versus a placebo drink; insulin did not differ. A single-dose test.
  12. Mackenzie T, Leary L, Brooks WB. The effect of an extract of green and black tea on glucose control in adults with type 2 diabetes mellitus: double-blind randomized study. Metabolism. 2007;56(10):1340-4. doi: 10.1016/j.metabol.2007.05.018.PubMedUsed to support: Double-blind randomized trial in 49 adults with type 2 diabetes (not on insulin): a combined green and black tea extract at 375 or 750 mg/day for 3 months did not change HbA1c compared with placebo.
  13. Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999;81(4):289-95..PubMedUsed to support: Radio-iron absorption study in adults: beverages drunk with a bread meal cut non-heme iron absorption in proportion to their polyphenol content. Black tea reduced absorption by 79 to 94% versus water, more than cocoa or most herb teas at equal polyphenol content, and adding milk made little difference.
  14. Ahmad Fuzi SF, Koller D, Bruggraber S, Pereira DI, Dainty JR, Mushtaq S. A 1-h time interval between a meal containing iron and consumption of tea attenuates the inhibitory effects on iron absorption: a controlled trial in a cohort of healthy UK women using a stable iron isotope. Am J Clin Nutr. 2017;106(6):1413-1421. doi: 10.3945/ajcn.117.161364.PubMedUsed to support: Stable-isotope study in 12 healthy UK women: tea drunk with an iron-containing porridge meal lowered iron absorption (3.6% versus 5.7% with water), while tea taken 1 hour after the meal roughly halved that inhibitory effect. The abstract does not name the type of tea.
  15. Zhu K, Ouyang J, Huang J, Liu Z. Research progress of black tea thearubigins: a review. Crit Rev Food Sci Nutr. 2021;61(9):1556-1566. doi: 10.1080/10408398.2020.1762161.PubMedUsed to support: Review describing thearubigins as the most abundant component of black tea, responsible for much of its color and mouthfeel, and noting they are less studied than smaller black tea polyphenols because they are a highly mixed group of compounds. The bioactivities it lists come mainly from laboratory research.
  16. US Food and Drug Administration. Spilling the Beans: How Much Caffeine is Too Much? FDA Consumer Updates. 2024;Content current as of 08/28/2024..SourceUsed to support: Not PubMed-indexed (FDA consumer page, read 2026-10-03). FDA cites 400 mg of caffeine a day as an amount not generally associated with negative effects for most adults, lists black tea at typically 71 mg of caffeine per 12 fl oz, and notes that decaffeinated teas still contain some caffeine.
  17. Zhao Y, Asimi S, Wu K, Zheng J, Li D. Black tea consumption and serum cholesterol concentration: Systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2015;34(4):612-9. doi: 10.1016/j.clnu.2014.06.003.PubMedUsed to support: Meta-analysis of 10 randomized trials (411 participants): black tea lowered LDL cholesterol by 4.64 mg/dL (95% CI -8.99 to -0.30), more so in people at higher cardiovascular risk, with no significant change in total or HDL cholesterol.