Theaflavins are orange-red pigments, a small family of polyphenols (plant compounds) that form when black tea is made. Four are routinely measured: theaflavin, theaflavin-3-gallate, theaflavin-3′-gallate and theaflavin-3,3′-digallate. They arise when enzymes in the tea leaf oxidize green tea catechins.
That is why a cup of green tea holds only 0.12 mg in the USDA data. A 200 mL cup of the black tea measured in one trial held about 18 mg. Together with thearubigins, theaflavins account for almost all the color of a black tea liquor.
The tea plant seems to use them too. A 2026 study reported that jasmonate, a plant stress hormone, induces theaflavins in tea plants. At a low dose (1.25 µg/g) they worked as defenses against insect herbivores.
They are also a small part of the leaf. In 1958 E. A. H. Roberts put them at up to 2% of the dry weight of tea. A 2026 survey of 32 Assam black teas found about 0.5% to 1.6%.
Two things most people do not know. In 1958 Roberts suggested that theaflavins and caffeine make tea brisk. Yet a 2004 taste analysis of black tea infusions found that neither theaflavins, catechins nor thearubigins were the main source of astringency. Flavonol glycosides were.
And very little of what you swallow is absorbed. After 700 mg of theaflavins, about 30 cups of black tea by the authors’ estimate, blood plasma peaked at only 1.0 µg/L.
Health benefits of theaflavin
None of the studies below reaches strong evidence. Only a few trials tested theaflavins themselves, in doses from 45 mg in a drink to 500 mg in one capsule. The best-known result is a 2003 trial in which a theaflavin-enriched green tea extract lowered LDL (“bad”) cholesterol by 16.4%. But a later trial of purified theaflavins at 77.5 mg a day found no difference from placebo (a dummy pill).
Meta-analyses are studies that pool many trials. Those of black tea show a small drop in blood pressure, 1 to 2 mmHg, and mixed results for cholesterol. That is tea, not theaflavins. Here is what 18 studies found, strongest evidence first, including the trials that found nothing.
4 to 5 cups of black tea lowered systolic pressure 1.8 mmHg
This meta-analysis pooled 11 placebo-controlled studies (12 arms, 378 people) in which adults drank black tea for at least a week. This is tea, not theaflavins on their own. Systolic pressure (the top number) fell 1.8 mmHg and diastolic (the bottom number) 1.3 mmHg. The size of the effect depended on tea extract powder versus leaf tea, and on starting blood pressure; four authors work for Unilever.
Black tea lowered blood pressure slightly, with no clear dose pattern
This dose-response meta-analysis pooled 13 randomized trials (22 study arms) of black tea in adults. Systolic pressure fell 1.04 mmHg and diastolic 0.59 mmHg. In a nonlinear analysis, dose and duration had no clear influence, and the authors call for trials with other doses. Again this is black tea, not isolated theaflavins.
Across 15 trials, black tea did not clearly lower LDL cholesterol
This meta-analysis pooled randomized trials of black tea drinking. In healthy people, LDL fell 5.57 mg/dL in the simpler statistical model. In the more cautious model it fell 4.56 mg/dL, a drop that could be chance. Total cholesterol and HDL did not change, and people with coronary disease had no LDL change. Tea polyphenol dose made no difference, and the authors want better trials.
Theaflavin-enriched green tea extract lowered LDL cholesterol by 16.4%
240 adults with mild to moderate high cholesterol, on a low-fat diet at 6 hospitals in China, took part. They took 375 mg a day or placebo for 12 weeks, double-blind. Total cholesterol fell 11.3%, while HDL (2.3%) and triglycerides (2.6%) did not change clearly, and the placebo group did not change. No significant adverse events were seen. The extract was enriched with theaflavins, so the result cannot be credited to them alone. The abstract does not give the theaflavin share or the funder.
Show 14 more studies
Purified theaflavins did not lower cholesterol compared with placebo
102 people with mildly to moderately raised cholesterol took part in this 11-week double-blind trial. They took theaflavins alone (77.5 mg a day), theaflavins with catechins (75.0 mg plus 150.0 mg catechins and 195.0 mg other polyphenols) or placebo. Total and LDL cholesterol did not differ between groups, and both fell over time in the theaflavin and placebo groups. The lead author works for Unilever.
A single 300 mg dose improved small blood vessel function
24 healthy adults, double-blind, took on separate days 500 mg of catechins, four doses of theaflavins (100 to 500 mg) or placebo. The reactive hyperemia index (RHI), a test of small blood vessels, was measured at 2, 4 and 6 hours. RHI rose by 0.28 at 300 mg, by 0.19 at 500 mg (a borderline result) and by 0.2 with catechins, and lower doses did nothing. These were single doses, not daily use, and the authors work for Unilever.
A theaflavin drink raised blood pressure for a few hours
In this pilot randomized trial, healthy volunteers had a drink with 45 mg of theaflavins. Blood pressure rose clearly 2 and 4 hours later. Flow-mediated dilation (FMD), a test of how well arteries widen, improved compared with placebo at 4 hours. In an earlier rat study, one dose raised blood pressure and heart rate briefly, while 2 weeks of 10 mg/kg a day lowered it. The abstract does not give the number of volunteers.
Theaflavins for 10 weeks lowered body fat percentage in a small trial
In this randomized double-blind pilot study, 30 healthy Japanese adults were split between placebo, theaflavins (50 or 100 mg a day) and catechins (400 mg). Body fat and subcutaneous fat fell, and skeletal muscle percentage rose, with theaflavins compared with placebo. Catechins did not differ from placebo. Groups were very small, and the authors work for Yaizu Suisankagaku Industry, a company.
Theaflavins did not change the main gum-disease bacteria
56 healthy adults without gum disease took theaflavins or placebo for 6 weeks, 28 per group, double-blind. The main endpoint, numbers of P. gingivalis and F. nucleatum in saliva, was unchanged. Prevotella intermedia fell more with theaflavins, a borderline result. Clinical evaluation did not change, no significant adverse effect was seen, and the abstract does not give the dose.
Three cups of black tea daily went with lower blood sugar, triglycerides
In this randomized trial in Mauritius, people from a normal population drank 3 x 200 mL of black tea a day without additives. They did so for 12 weeks, then had a 3-week break, and the tea measured 90 mg/L of theaflavins. Fasting glucose fell 18.4%, triglycerides 35.8% and the LDL/HDL ratio 16.6%. FRAP, an antioxidant measure, rose 418%, an unusually large change that calls for caution. The abstract does not give group sizes or say whether the control group had a placebo drink.
A catechin and theaflavin blend preserved leg strength after hard exercise
Men aged 18 to 35 took placebo, or 1,000 mg or 2,000 mg a day of a proprietary polyphenol blend. After 13 weeks they did a 40-minute downhill run. The high dose reduced the drop in peak leg torque at 48 and 96 hours, and eased soreness at 48 hours. The blend contains catechins and theaflavins, so the effect cannot be tied to theaflavins; the authors work for Kemin Foods.
Black tea lowered LDL by 0.43 mmol/L; heart events were unreported
This Cochrane review covered randomized trials lasting at least 3 months. Of 11 trials with 821 people, 4 tested black tea and 7 green tea. Black tea lowered LDL by 0.43 mmol/L and systolic blood pressure by 1.85 mmHg. No study reported cardiovascular events, and the authors say few trials fed each analysis, studies were at risk of bias and results need caution.
Highest black tea intake went with 11% lower coronary heart disease risk
This meta-analysis pooled 14 prospective cohort studies with 958,477 participants and 16,990 coronary heart disease cases. The top intake had 0.89 times the risk, and results varied moderately between studies (I2 = 50.6%). Risk was lower at 2 cups a day (0.95) and 4 cups a day (0.91). The link held in Europe but not in the USA, and as observational data on black tea, not theaflavins, it cannot show cause.
Two theaflavin gallates cut gut-cell bile acid uptake to about a third
This cell study examined 39 polyphenols in Caco-2 gut-lining cells. Theaflavin-3-gallate and theaflavin-3′-gallate cut uptake of the bile acid taurocholic acid to 37.4% and 33.8% of untreated cells. They appeared to bind the bile acid transporter ASBT through its cysteine residues. Blocking that transporter is one proposed way to lower cholesterol, but this was done in cells, not people.
In a test tube, theaflavins reduced cholesterol entering bile-acid micelles
This lab study used artificial micelles, tiny fat carriers, made from oleic acid, bile acids, lysophosphatidylcholine and cholesterol. Theaflavins, mainly theaflavin-3-gallate, cut the amount of labeled cholesterol that entered micelles, more at higher doses, and made large, onion-like vesicles instead. The authors work for Unilever. It points to less cholesterol absorption in the gut, which this study did not test in people.
Theaflavin reduced artery plaque in mice on a high-fat diet
Mice lacking ApoE ate a high-fat diet with or without 5 or 10 mg of theaflavin by stomach tube for 12 weeks. Blood fats and MDA, a marker of fat damage, fell, and the enzymes SOD, CAT and GSH-Px rose. In human vein-lining cells, theaflavin turned up Nrf2/HO-1 signaling and microRNA-24. These are mouse and cell results.
A theaflavin reduced fat droplets in liver cells in a dish
This cell study looked at one theaflavin, theaflavin-3,3′-digallate (TF3). It cut lipid droplet buildup in liver cells, bound plasma kallikrein and stimulated AMPK, an energy-sensing enzyme. The authors propose plasma kallikrein as a target for fatty liver disease. The abstract reports no animal or human data.
A theaflavin-rich tea fraction made human fat cells store more fat
This study used primary human fat cells from under the skin, in a dish. A fraction from green tea co-fermented with garland chrysanthemum was high in theaflavin. It made the cells mature, with more lipid droplets, fat-cell gene activity and adiponectin release, without hurting cell viability. The authors read this as a possible skin-structure benefit, though effects may depend on cell type, since reviews describe anti-obesity results in animals.
Foods high in theaflavin
Theaflavins are a black tea compound. They form when the leaf is oxidized, so black tea is the food source that matters. The USDA ranking below lists only green tea, at 0.05 mg per 100 g or 0.12 mg in a cup. It does not list black tea, so the table after it uses published measurements.
In 32 black teas from Assam, the dry leaf held 4.88 to 15.54 mg of theaflavins per gram. The brew gets only part of that. In four tea bag products, at most 35% to 55% of the theaflavins in the leaf reached the brew.
One Mauritian black tea measured 90 mg/L, which is about 18 mg in a 200 mL cup. The authors of another study equated 700 mg with about 30 cups, or about 23 mg a cup.
In a European survey of 36,037 adults, theaflavin intake was highest in the UK general population. Men there took in about 29 mg a day and women 25 mg, against close to zero in Greece and Spain. Black tea extracts sold as supplement ingredients are far more concentrated than tea, as the last row shows.
Per serving. No daily amount is set, so bars compare each food with the top food.
Per 100 g. No daily amount is set, so bars compare each food with the top food.
Per 100 kcal: the same calories of each food, for a fair comparison. Bars compare each food with the top food.
Food labels have no Daily Value or Reference Intake for theaflavin, so the % compares each food with the top food.
| Food | Amount per 100 g (unless noted) | Source |
|---|---|---|
| Black tea leaf, dry (32 teas from Assam) | 488 to 1,554 mg per 100 g (published as 4.88 to 15.54 mg/g, average 8.61 mg/g) | 1 |
| Brewed black tea (one Mauritian tea) | 9 mg per 100 mL (published as 90 mg/L) | 2 |
| Brewed black tea, authors’ equivalence | About 23 mg per cup (700 mg was said to equal about 30 cups) | 3 |
| Black tea extract sold as a supplement ingredient (two products) | 14.04 g and 92.2 g per 100 g (published as 14.04% and 92.2% w/w) | 4 |
Sources
- Sarmah PP, Deka H, Parasar P, et al. Biochemical quality profile of black tea from Upper Assam and North Bank region of Assam, India. Foods. 2026. Leaf measured by HPLC after methanol extraction.
- Bahorun T, Luximon-Ramma A, Neergheen-Bhujun VS, et al. The effect of black tea on risk factors of cardiovascular disease in a normal population. Prev Med. 2012.
- Mulder TP, van Platerink CJ, Wijnand Schuyl PJ, van Amelsvoort JM. Analysis of theaflavins in biological fluids using liquid chromatography-electrospray mass spectrometry. J Chromatogr B Biomed Sci Appl. 2001.
- Noritake SM, Liu J, Kanetake S, et al. Phytochemical-rich foods inhibit the growth of pathogenic trichomonads. BMC Complement Altern Med. 2017. Two commercial black tea extracts analyzed by HPLC.
- Lakenbrink C, Lapczynski S, Maiwald B, Engelhardt UH. Flavonoids and other polyphenols in consumer brews of tea and other caffeinated beverages. J Agric Food Chem. 2000.
- Knaze V, Zamora-Ros R, Luján-Barroso L, et al. Intake estimation of total and individual flavan-3-ols, proanthocyanidins and theaflavins, their food sources and determinants in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Br J Nutr. 2012.
- USDA Database for the Flavonoid Content of Selected Foods, Release 3.3. Bhagwat S, Haytowitz DB. US Department of Agriculture, Agricultural Research Service. 2018.
How theaflavin works
Most of what we know about how theaflavins act comes from test tubes, cells and animals. Four ideas come up again and again. They are made from green tea catechins by oxidation, and they get in the way of cholesterol and bile acid uptake in the gut. They also switch on the cell’s own defenses, and very little of them reaches the blood.
Here is each one, and what has been seen in people.
They are green tea catechins that oxidized
In the fresh leaf, the starting material is catechins such as EGCG, EGC and epicatechin. During black tea making, plant enzymes called polyphenol oxidase and peroxidase oxidize them, and catechins join in pairs to form theaflavins. In a study that followed the process, catechins fell and theaflavins rose. Theaflavin-3-gallate tracked the loss of the cis-catechins most closely.
The order of events in making black tea. The theaflavin range is from leaf of 32 Assam black teas, and the thearubigin share is Roberts’s 1958 figure.
Theaflavins are not the end of the line. Roberts showed that they undergo further oxidation during fermentation, and that this produces thearubigins, the larger and still poorly understood part of black tea color.
They get in the way of cholesterol and bile acid uptake
In test-tube mixtures that copy the contents of the gut, theaflavins reduced the amount of cholesterol that entered micelles. These are the tiny fat carriers that move cholesterol toward the gut wall. Theaflavin-3-gallate did most of the work, forming large insoluble vesicles instead. In gut-lining cells, two theaflavin gallates cut uptake of a bile acid to about a third of normal.
A 2024 review adds other ideas from animal and cell work. They include less fat absorption through pancreatic lipase, activation of AMPK and changes in gut microbes. The micelle study was done by Unilever authors.
Drawn to scale. In this cell study the two theaflavin gallates are the polyphenols its abstract reports out of 39 tested.
They switch on the cell’s own defenses
In mice on a high-fat diet, theaflavin lowered blood fats, raised the antioxidant enzymes SOD, CAT and GSH-Px, and reduced plaque in the aorta. In human vein-lining cells it turned up Nrf2/HO-1 signaling, a control switch for the cell’s protective enzymes. In liver cells, one theaflavin, the digallate, lowered fat droplets by way of AMPK.
One fat-cell experiment points the other way: a theaflavin-rich tea fraction made human fat cells mature and store more fat. All of these are cell and mouse results.
Very little reaches the blood
This is the catch. In a 2001 study, two volunteers took 700 mg of theaflavins, which the authors equated with about 30 cups of black tea. The highest level in blood plasma was 1.0 µg/L, two hours later. A later feeding study found that theaflavin and its gallate forms were not absorbed in detectable amounts.
Gut bacteria removed the gallate groups, and in a fecal test 67% of the theaflavin core was still there after 24 hours. A 2025 review links the low absorption to poor stability at different pH values and to efflux transporters, which pump compounds back out of cells. It says the metabolites in people are not fully understood.
Not drawn to scale. The blood level comes from two volunteers, and the colon result from a lab test with fecal bacteria.
Tea polyphenols do reach some tissues. 20 men drank 1.42 L a day of black or green tea, or a caffeine-matched soda, for 5 days before prostate surgery. Tea polyphenols were higher in prostate samples of the tea drinkers, although none were detectable in serum. The paper’s title reports theaflavins in that tissue.
What has been seen in people
These ideas are much easier to show in a dish than in a person. For cholesterol, a 2003 trial of a theaflavin-enriched green tea extract found LDL 16.4% lower. But purified theaflavins at 77.5 mg a day did not differ from placebo, and meta-analyses of black tea show at most a small LDL change.
A single 300 mg dose improved small blood vessel function, while a 45 mg drink raised blood pressure for a few hours. All of these are among the study cards above. So little is absorbed that it is not known where any effect comes from. It could be theaflavins themselves, their breakdown products or action inside the gut.
Sources
- Sarmah PP, Deka H, Parasar P, et al. Biochemical quality profile of black tea from Upper Assam and North Bank region of Assam, India. Foods. 2026.
- Lee LS, Kim YC, Park JD, Kim YB, Kim SH. Changes in major polyphenolic compounds of tea (Camellia sinensis) leaves during the production of black tea. Food Sci Biotechnol. 2016.
- Roberts EAH. The estimation of the theaflavins and thearubigins in made teas. Tea Quarterly. 1958;29(2):99-100. Reprinted from Two and a Bud, 1958.
- Dong S, Wu S, Hao F, et al. Research advancements on theaflavins: isolation, purification, synthesis, gut microbiota interactions, and applications potentials. Food Res Int. 2025.
- Vermeer MA, Mulder TP, Molhuizen HO. Theaflavins from black tea, especially theaflavin-3-gallate, reduce the incorporation of cholesterol into mixed micelles. J Agric Food Chem. 2008. The authors work for Unilever.
- Takashima Y, Ishikawa K, Miyawaki R, et al. Modulatory effect of theaflavins on apical sodium-dependent bile acid transporter (ASBT) activity. J Agric Food Chem. 2021.
- Zeng J, Deng Z, Zou Y, et al. Theaflavin alleviates oxidative injury and atherosclerosis progress via activating microRNA-24-mediated Nrf2/HO-1 signal. Phytother Res. 2021.
- Zhang W, An R, Li Q, et al. Theaflavin TF3 relieves hepatocyte lipid deposition through activating an AMPK signaling pathway by targeting plasma kallikrein. J Agric Food Chem. 2020.
- Park PJ, Rha CS, Kim ST. Theaflavin-enriched fraction stimulates adipogenesis in human subcutaneous fat cells. Int J Mol Sci. 2019.
- Fang Y, Wang J, Cao Y, et al. The antiobesity effects and potential mechanisms of theaflavins. J Med Food. 2024.
- Mulder TP, van Platerink CJ, Wijnand Schuyl PJ, van Amelsvoort JM. Analysis of theaflavins in biological fluids using liquid chromatography-electrospray mass spectrometry. J Chromatogr B Biomed Sci Appl. 2001. The lead author works for Unilever.
- Pereira-Caro G, Moreno-Rojas JM, Brindani N, et al. Bioavailability of black tea theaflavins: absorption, metabolism, and colonic catabolism. J Agric Food Chem. 2017.
- Li M, Li W, Dong Y, et al. Advances in metabolism pathways of theaflavins: digestion, absorption, distribution and degradation. Crit Rev Food Sci Nutr. 2025.
- Henning SM, Aronson W, Niu Y, et al. Tea polyphenols and theaflavins are present in prostate tissue of humans and mice after green and black tea consumption. J Nutr. 2006.
- Zhang J, Wang WW, Zhang X, et al. Anti-herbivore activity of jasmonate-induced theaflavins: integrated multi-omics reveals flavonoid-mediated defense strategies in tea plants. J Agric Food Chem. 2026.
- Scharbert S, Holzmann N, Hofmann T. Identification of the astringent taste compounds in black tea infusions by combining instrumental analysis and human bioresponse. J Agric Food Chem. 2004.
Is theaflavin safe? Supplements, dose and interactions
Theaflavins at the amounts in black tea are not a known safety concern. Black tea is a common drink, and UK adults take in about 25 to 29 mg of theaflavins a day. We found no acceptable daily intake, upper level, FDA GRAS notice or EFSA novel food assessment for theaflavins themselves.
EFSA (the EU’s food safety agency) did review a black tea defined by catechins plus theaflavins of at least 30 mg per 200 mL. That was a health claim opinion, and it found no established link to normal blood vessel widening. EFSA’s separate opinion on green tea catechins found that 800 mg or more of EGCG a day from supplements raised liver enzymes. It is about catechins, but the 2003 cholesterol trial used a green tea extract.
- Trial doses and side effects. Trials used 45 mg in a drink, 50 to 100 mg a day for 10 weeks, and 77.5 mg a day for 11 weeks. Others used single capsules of 100 to 500 mg, or 375 mg a day of an enriched green tea extract for 12 weeks. The 2003 trial reported no significant adverse events, and a 6-week trial in 56 adults found no significant adverse effect. Most ran 6 to 12 weeks, so long-term use is untested.
- Blood pressure. In a small trial, a drink with 45 mg of theaflavins raised blood pressure clearly 2 and 4 hours later. In rats, one dose raised blood pressure and heart rate briefly. People with high blood pressure or on blood pressure drugs should ask a clinician before taking a supplement. Drinking black tea for a week or more lowered blood pressure slightly in meta-analyses.
- Iron. In a trial of a bread meal, black tea cut absorption of non-heme iron by 79% to 94%. That was tea, not theaflavins alone, but people with low iron may want to ask about timing.
- Pregnancy, children and medicines. We found no theaflavin trials in pregnancy, breastfeeding or children, and no drug interaction studies, so ask your doctor. Black tea also contains caffeine: 15.51 to 39.24 mg per gram of leaf in 32 Assam teas.
How to get more theaflavin
- Best food. Black tea. One measured Mauritian tea held 9 mg per 100 mL, while the USDA lists green tea at 0.05 mg per 100 g.
- Brew it well. A study of tea bags found that at most 35% to 55% of the theaflavins in the leaf reached the brew. Another found that the amounts of tea and water, the infusion time and the stirring all changed what ended up in the cup.
- Food versus supplement. Absorption is very low from either. Doses of 45 to 500 mg are about 2.5 to 28 cups of the Mauritian tea at 18 mg a cup (our arithmetic). No trial shows that a higher dose is absorbed better.
Sources
- Bahorun T, Luximon-Ramma A, Neergheen-Bhujun VS, et al. The effect of black tea on risk factors of cardiovascular disease in a normal population. Prev Med. 2012.
- Knaze V, Zamora-Ros R, Luján-Barroso L, et al. Intake estimation of total and individual flavan-3-ols, proanthocyanidins and theaflavins, their food sources and determinants in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Br J Nutr. 2012.
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Black tea and maintenance of normal endothelium-dependent vasodilation: evaluation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006. EFSA J. 2018. Application from Unilever.
- EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). Scientific opinion on the safety of green tea catechins. EFSA J. 2018.
- Maron DJ, Lu GP, Cai NS, et al. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial. Arch Intern Med. 2003.
- Katanasaka Y, Yoshida N, Naitou H, et al. Effect of theaflavin on oral bacteria in Japanese subjects: a randomized, placebo-controlled, double-blind study. J Med Food. 2021.
- Saito A, Nakazato R, Suhara Y, et al. The impact of theaflavins on systemic- and microcirculation alterations: the murine and randomized feasibility trials. J Nutr Biochem. 2016.
- Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999.
- Sarmah PP, Deka H, Parasar P, et al. Biochemical quality profile of black tea from Upper Assam and North Bank region of Assam, India. Foods. 2026.
- Lakenbrink C, Lapczynski S, Maiwald B, Engelhardt UH. Flavonoids and other polyphenols in consumer brews of tea and other caffeinated beverages. J Agric Food Chem. 2000.
- Astill C, Birch MR, Dacombe C, Humphrey PG, Martin PT. Factors affecting the caffeine and polyphenol contents of black and green tea infusions. J Agric Food Chem. 2001.
- Mulder TP, van Platerink CJ, Wijnand Schuyl PJ, van Amelsvoort JM. Analysis of theaflavins in biological fluids using liquid chromatography-electrospray mass spectrometry. J Chromatogr B Biomed Sci Appl. 2001.
- Pereira-Caro G, Moreno-Rojas JM, Brindani N, et al. Bioavailability of black tea theaflavins: absorption, metabolism, and colonic catabolism. J Agric Food Chem. 2017.
- Li M, Li W, Dong Y, et al. Advances in metabolism pathways of theaflavins: digestion, absorption, distribution and degradation. Crit Rev Food Sci Nutr. 2025.
- USDA Database for the Flavonoid Content of Selected Foods, Release 3.3. Bhagwat S, Haytowitz DB. US Department of Agriculture, Agricultural Research Service. 2018.
History of theaflavin
In 1958 E. A. H. Roberts reported on the color in a black tea liquor that comes from oxidation products. Nearly all of it belongs to two classes of substances that chemists had not recognized before. He suggested calling them thearubigins and theaflavins.
The theaflavins, he wrote, give the golden-yellow element of the color and the thearubigins the rusty brown. He had two of them in pure form, theaflavin and theaflavin gallate. Together they made up as much as 2% of the dry weight of tea. He showed that they undergo further oxidation during fermentation, which produces thearubigins.
Roberts also described a spectrophotometer (light-measuring) method to estimate both groups in tea liquors. He tied the results to what tasters call strength, color and briskness. He suggested, provisionally, that briskness comes from theaflavins together with caffeine, and found that storing moist teas at high temperatures destroyed theaflavins.
A 2004 taste analysis later pointed to flavonol glycosides, not theaflavins, as the main source of astringency.
Making black tea is often called fermentation, although the work is done by enzymes in the leaf, not by microbes. Four theaflavins are now measured routinely, but the chemistry of the thearubigins proved much harder. A 2010 paper said that, 50 years after the name was introduced, their chemical nature remained largely unresolved.
A 2003 trial in China tested a theaflavin-enriched green tea extract on cholesterol. In 2018 EFSA, at the request of Unilever, looked at black tea defined by catechins plus theaflavins of at least 30 mg per 200 mL. It judged that a cause and effect relationship with normal endothelium-dependent vasodilation (blood vessel widening) had not been established.
Sources
- Roberts EAH. The estimation of the theaflavins and thearubigins in made teas. Tea Quarterly. 1958;29(2):99-100. Reprinted from Two and a Bud, 1958.
- Scharbert S, Holzmann N, Hofmann T. Identification of the astringent taste compounds in black tea infusions by combining instrumental analysis and human bioresponse. J Agric Food Chem. 2004.
- Kuhnert N. Unraveling the structure of the black tea thearubigins. Arch Biochem Biophys. 2010.
- Dong S, Wu S, Hao F, et al. Research advancements on theaflavins: isolation, purification, synthesis, gut microbiota interactions, and applications potentials. Food Res Int. 2025.
- Sarmah PP, Deka H, Parasar P, et al. Biochemical quality profile of black tea from Upper Assam and North Bank region of Assam, India. Foods. 2026.
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Black tea and maintenance of normal endothelium-dependent vasodilation: evaluation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006. EFSA J. 2018.
- Maron DJ, Lu GP, Cai NS, et al. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial. Arch Intern Med. 2003.
- Theaflavin. Wikipedia.
Frequently asked questions about theaflavin
What do theaflavins do for the body?
The best-supported effects are small and come from black tea, not from theaflavins alone: meta-analyses found blood pressure about 1 to 2 mmHg lower. Trials of theaflavins themselves are few and mixed. One found LDL 16.4% lower with an enriched extract, and another found no effect at 77.5 mg a day. Small trials looked at blood vessel function and body fat, and no finding reaches strong evidence.
Which foods are high in theaflavins?
Black tea is the source. The dry leaf held 4.88 to 15.54 mg per gram in 32 Assam teas. One measured Mauritian tea had 90 mg/L, about 18 mg per 200 mL cup. The USDA data list green tea at only 0.05 mg per 100 g, and we found no measured values for other foods.
How much theaflavin should you take a day?
No dose is proven. Trials used 45 mg in a drink, 50 to 100 mg a day for 10 weeks and single doses of 100 to 500 mg. 77.5 mg a day for 11 weeks did not change cholesterol. A cup of the measured black tea held about 18 mg. We found no official upper level, so talk to a clinician before taking a supplement.
Do theaflavins lower cholesterol?
Possibly, but the evidence is mixed. A 2003 trial of 240 adults found LDL 16.4% lower with a theaflavin-enriched green tea extract, which also holds green tea compounds. A trial of 102 adults on purified theaflavins found no difference from placebo. A meta-analysis of 15 black tea trials found no clear LDL change. A Cochrane review of 4 black tea trials found 0.43 mmol/L lower.
Are theaflavins absorbed by the body?
Only in tiny amounts. After 700 mg of theaflavins, two volunteers had a peak of 1.0 µg/L in blood plasma. In a feeding study they were not absorbed in detectable amounts, and gut bacteria broke off their gallate groups. What the breakdown products do in people is not well understood.
Do theaflavin supplements have side effects?
Trials reported few. A 12-week trial of an enriched green tea extract reported no significant adverse events, and so did a 6-week trial in 56 adults. A small trial found that a 45 mg drink raised blood pressure for a few hours. Black tea can also cut iron absorption, and we found no studies in pregnancy or on drug interactions.
What is the difference between theaflavins and thearubigins?
Thearubigins come from further oxidation of theaflavins and make up much more of black tea. Roberts put them at more than 10% of the dry matter, against up to 2% for theaflavins. A 2010 paper said their structure is still largely unresolved. See the page on thearubigins for what is known.
Is there theaflavin in green tea?
Only a little. The USDA data list 0.05 mg per 100 g for green tea, or 0.12 mg in a cup. Theaflavins form when catechins oxidize during black tea making. The 2003 cholesterol trial used a green tea extract that had been enriched with theaflavins.