Black Tea (Camellia sinensis, fully oxidized)

Black Tea vs. Green Tea

Black tea and green tea come from the same plant; the difference is processing. Black tea leaves are rolled and fully oxidized, green tea leaves are heated soon after picking to stop oxidation. That one step changes the polyphenols, color, flavor and, to a lesser degree, caffeine.

Black tea figures are cited in this entry; green tea caffeine is from USDA FoodData Central as cited in the green tea entry, and catechin values for both come from the same compilation (van Duynhoven et al., 2013). Neither is clearly healthier: green tea has more catechin research, black tea more blood-pressure and population data. Matcha, a powdered green tea eaten as the whole leaf, usually carries more caffeine per serving than either, at about 38–88 mg.

Active Compounds

The oxidation process distinguishes black tea’s chemistry from that of green tea in fundamental ways. Rather than EGCG-dominant catechin chemistry, black tea is characterized by a complex mixture of catechin oxidation products.

Theaflavins are orange-red pigments formed by the co-oxidation and dimerization of specific pairs of green tea catechins. Four primary theaflavins have been characterized: theaflavin (TF1), theaflavin-3-gallate (TF2a), theaflavin-3’-gallate (TF2b), and theaflavin-3,3’-digallate (TF3). Together they make up roughly 2–6% of the solids extracted into a black tea brew (Linus Pauling Institute), with the amount depending on brewing time and tea grade. Theaflavins are the primary contributors to the bright orange-red color of a freshly poured cup. They carry galloyl groups structurally analogous to those in EGCG, and have demonstrated anti-inflammatory and antioxidant properties in cell culture and animal models, primarily through NF-κB pathway inhibition and direct radical scavenging.

Thearubigins are a heterogeneous class of high-molecular-weight polymeric polyphenols that form progressively during extended oxidation and make up more than 20% of the extracted solids (Linus Pauling Institute). Compiled analytical data put brewed black tea at about 81 mg of thearubigins per 100 mL, or roughly 160 mg in a 200 mL cup (van Duynhoven et al., 2013). Thearubigins are responsible for the dark mahogany color and much of the body and mouthfeel of a steeped cup of black tea. Their chemical structure is incompletely characterized due to their molecular complexity, but they represent the bulk of black tea polyphenol content and likely contribute to the majority of antioxidant capacity measured in vitro.

Residual catechins: Oxidation in black tea is extensive but not complete. Brewed black tea contains about 25 mg of catechins per 100 mL (roughly 50 mg in a 200 mL cup), including residual EGCG, EGC, EC, and ECG — substantially less than green tea brewed the same way (about 125 mg per 100 mL), but not negligible (van Duynhoven et al., 2013).

L-theanine is present in black tea, though at lower concentrations than in shade-grown green teas. In an analysis of 37 commercial teas, black tea leaf averaged 5.1 mg of L-theanine per gram versus 6.6 mg/g for green tea (Boros et al., 2016), but the brewed cup differs less: a 2025 analysis measured about 12 mg per 200 mL in both brewed black and green tea (Ayakdaş & Ağagündüz, 2025), and Unilever researchers have put a typical cup of black tea at about 20 mg (Nobre et al., 2008). A cup therefore holds roughly 10–20 mg, depending on how much leaf is used and how long it steeps. The L-theanine concentration depends on leaf grade and growing conditions; first-flush Darjeeling and shaded cultivars tend to be at the higher end.

Caffeine: USDA FoodData Central lists brewed black tea at about 20 mg per 100 mL (roughly 40 mg per 200 mL cup), and measurements of more than 20 teas prepared to package directions ranged from 42 to 79 mg per 8-ounce (240 mL) serving (Linus Pauling Institute). The range is wide because caffeine content depends on leaf grade (tips and younger leaves have more caffeine), brewing time, water temperature, and whether bags or loose leaf is used. Compared with a single 1-ounce espresso (~63 mg caffeine; USDA FoodData Central), a typical mug of black tea delivers a moderate but meaningful caffeine dose.

Fluoride is concentrated in mature Camellia sinensis leaves, and black tea made from older, cheaper leaf grades can contain significant fluoride. Brick tea, pressed from older leaves and stems, is the extreme case: in a survey across Tibet, where it is drunk in large volumes, the median fluoride intake from brick tea alone was about 25 mg per day, and clinical skeletal fluorosis was diagnosed in 46% of adults examined (Fan et al., Journal of Epidemiology, 2016). Ordinary bagged black tea carries far less, but volume still matters. Waugh et al. (Journal of Environmental and Public Health, 2017) measured 18 commercial products in New Zealand and estimated 0.8–14.7 mg of fluoride per day for people drinking 6–10 mugs, depending on the brand and whether the brewing water was fluoridated. The US tolerable upper intake level is 10 mg/day for adults and children aged 9 and over, 2.2 mg/day for ages 4–8, and 1.3 mg/day for ages 1–3 (Institute of Medicine, 1997). Outside brick-tea regions, skeletal fluorosis from tea is rare and is described mainly in case reports of people drinking one to two gallons of tea a day for years (Izuora et al., Journal of Clinical Endocrinology & Metabolism, 2011).

Tannins: Black tea tannins (primarily thearubigins, theaflavins, and residual catechins) bind to dietary iron, particularly non-heme iron, and can reduce its absorption when consumed alongside iron-containing meals.

Black tea’s theaflavins form when the catechins found in green tea oxidize during processing; our review of polyphenols and aging covers the research on those catechins.

Nutritional Profile

Per 200 mL brewed cup (1 tea bag or ~2 g loose leaf, steeped 3–5 minutes in boiling water). Calories, potassium, and the upper fluoride figure scale from USDA FoodData Central; flavonoids, caffeine, and the lower fluoride figure from Linus Pauling Institute; thearubigins and catechins from van Duynhoven et al., 2013; L-theanine from Ayakdaş & Ağagündüz (2025) and Nobre et al. (2008):

Evidence for Purported Benefits

Typical Use and Preparation

Photo: AntanO, CC BY-SA 4.0, via Wikimedia Commons

Black tea preparation varies substantially by tradition and purpose:

Western (British-style) brewing: Loose-leaf or bagged tea steeped in freshly boiled water (95–100°C) for 2–5 minutes. Longer steeping extracts more polyphenols and caffeine but also more tannins, increasing astringency. Milk is commonly added, but in a radio-iron study adding milk had little or no influence on tea’s inhibition of iron absorption (Hurrell et al., 1999); milk’s effect on polyphenol bioavailability is debated but modest at typical consumption levels.

Masala chai: Black tea (typically Assam CTC) combined with spices (cardamom, ginger, cinnamon, cloves, black pepper), simmered with milk and sweetener. The spice mixture contributes additional polyphenols and bioactive compounds; whether the milk-heavy preparation reduces polyphenol bioavailability is unsettled.

Iced tea: Cold-brewed black tea (cold water, 8–12 hours) extracts caffeine and flavor but may slightly reduce total polyphenol yield compared with hot brewing.

Darjeeling first-flush: Light-bodied, muscatel-flavored teas best brewed at 85–90°C for 3 minutes; boiling water can damage the more delicate catechin profile retained in lighter oxidized Darjeelings.

To preserve polyphenol content, avoid adding black tea to very cold water (slow extraction) or over-brewing in boiling water for more than 6 minutes (excessive bitterness without proportional polyphenol gain).

Frequently Asked Questions