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Research · Food and drink

Black tea

Two pooled analyses of trials found black tea lowered blood pressure by 1 to 2 mmHg, with mixed results for LDL cholesterol. Cohorts link it to about 10% lower death but not to less coronary artery disease. Drunk with a meal, it cut iron absorption by 79% to 94%, and very high intakes caused skeletal fluorosis in case reports.

Add to Bio HackChecked 2026-11-13
Status
A food, not a regulated health product. Black, green and oolong teas all come from the same plant, Camellia sinensis [1].
Also called
black tea, tea, English breakfast tea, Earl Grey, Assam tea, Darjeeling tea, Ceylon tea, orange pekoe, chai, iced tea, tea with milk, Camellia sinensis
Studied for
heart health, blood pressure, cholesterol, longer life, stroke prevention

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help2

Reported risks3

What it was studied for, and what was found

Shown to help2

Moderate

Death from any cause

Linked to 10% lower death at the highest black tea intake than the lowest in pooled cohorts, and about 12% lower at 2 or more daily cups in UK adults.

Compared with the lowest intake category [2]; people drinking no tea [3]

The numbers and sources
Effect
At the highest against the lowest black tea intake, the relative risk was 0.90 (95% CI 0.83 to 0.98) for death from any cause, 0.79 (95% CI 0.65 to 0.97) for cancer death and 0.88 (95% CI 0.77 to 1.01) for cardiovascular death [2]. In UK adults, against no tea, the hazard ratio for death was 0.95 (95% CI 0.91 to 1.00) at 1 cup or fewer a day, 0.87 (95% CI 0.84 to 0.91) at 2 to 3 cups and 0.88 at 4 to 5 and at 6 to 7 cups, with similar results at higher intakes. Results held whether or not people also drank coffee and across genetic differences in caffeine metabolism [3].
Population
18 prospective cohorts with 55,528 deaths, pooled by tea type [2]. 498,043 UK adults aged 40 to 69 followed a median 11.2 years, in a population where black tea is the main type drunk [3].
Sources
[2], [3]
Caveats
Observational. Tea drinkers differ from non-drinkers in other habits (confounding), and illness can change what people drink (reverse causation). The UK study did not measure cup size or strength [3].
Strong

Blood pressure

Shown to lower blood pressure slightly, by 1 to 2 mmHg systolic and under 1.5 mmHg diastolic, in two pooled analyses of controlled trials.

Compared with placebo [6]; control groups the abstract does not describe [7]

The numbers and sources
Effect
Regular black tea lowered systolic pressure by 1.8 mmHg (95% CI -2.8 to -0.7) and diastolic by 1.3 mmHg (95% CI -1.8 to -0.8), and the effect differed by tea preparation, extract powder or leaf tea [6]. A later review found falls of 1.04 mmHg systolic (95% CI -2.05 to -0.03) and 0.59 mmHg diastolic (95% CI -1.05 to -0.13), with no clear effect of dose or duration [7].
Population
378 adults in 11 placebo-controlled studies of at least 1 week, at 4 to 5 cups a day [6]. 13 randomized trials with 22 study arms [7].
Sources
[6], [7]
Caveats
Small effects in small trials. Four of the seven authors of the first review were employed by Unilever R&D [6].

Mixed results2

Moderate

Heart disease and stroke

Mixed results: pooled cohorts found no link between black tea and coronary artery disease, while 3 or more daily cups of green or black tea went with 21% less stroke.

Compared with the lowest intake category [4][2]; people drinking under 1 cup a day [5]; people drinking no tea [3]

The numbers and sources
Effect
For black tea, coronary artery disease was not linked to intake (RR 0.92, 95% CI 0.82 to 1.04, highest against lowest, and 0.98, 95% CI 0.94 to 1.02, per daily cup) [4]. Black tea was not significantly linked to cardiovascular death in a second review [2]. In UK adults, tea was linked to lower death from cardiovascular disease, ischemic heart disease and stroke [3]. People drinking 3 or more cups of green or black tea a day had 21% lower stroke risk (0.79, 95% CI 0.73 to 0.85) than those drinking under 1 cup [5].
Population
13 studies of black tea [4]. 18 prospective cohorts [2]. 498,043 UK adults [3]. 194,965 people with 4,378 strokes in 9 studies [5].
Sources
[4], [2], [3], [5]
Caveats
Observational. The stroke review combined green and black tea [5].
Moderate

Cholesterol

Mixed results: one pooled analysis found black tea lowered LDL cholesterol by 4.6 mg/dL, while another found no significant change. Total and HDL cholesterol did not change.

Compared with control groups in randomized trials the abstracts do not describe [8][9]

The numbers and sources
Effect
Black tea lowered LDL cholesterol by 4.64 mg/dL (95% CI -8.99 to -0.30), more in people at higher cardiovascular risk, with no change in total cholesterol (-2.04 mg/dL) or HDL (-1.15 mg/dL) [8]. A second review found LDL fell 5.57 mg/dL in healthy people in a fixed-effects analysis (95% CI -9.49 to -1.66) and 4.56 mg/dL, not significant, in a random-effects analysis (95% CI -10.30 to 1.17), with no change in total or HDL cholesterol [9].
Population
411 participants in 10 trials [8]. 15 randomized trials in healthy people and people with coronary artery disease [9].
Sources
[8], [9]
Caveats
Small trials. The second review concluded black tea might not lower cholesterol [9].

Amounts studied

Cohorts grouped people from no tea to 10 or more cups a day [3], or compared 3 or more cups a day with under 1 [5]. Blood pressure trials gave 4 to 5 cups a day for at least a week [6]. The iron studies gave tea with a single test meal, with beverages carrying 100 to 400 mg of polyphenols a serving reducing absorption most [10], or 1 hour after the meal [11]. The fluorosis cases drank 1 to 2 gallons of tea a day for decades [12][1].

Risks

Reported risks2

ModerateHow often is not known

Lower iron absorption from a meal

Shown in isotope studies to cut iron absorption from a meal by 79% to 94% when black tea was drunk with it. A 1-hour gap halved this in one trial.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Against water, black tea drunk with a bread meal cut non-heme iron absorption by 79% to 94%, and adding milk made little or no difference [10]. Tea inhibited iron absorption from iron salts, bread, a rice meal and uncooked hemoglobin, with or without vitamin C, and not from cooked hemoglobin [13]. Iron absorption from a porridge meal was 5.7% with water, 3.6% with tea at the meal and 5.7% with tea 1 hour later, so the inhibition fell from 37.2% to 18.1% [11].
Population
Adult volunteers [10][13]. 12 healthy UK women with normal iron, mean age 24.8 [11].
Sources
[10], [13], [11]
Caveats
Single-meal studies measure absorption, not iron stores over time. The effect is on non-heme iron, and tea did not inhibit absorption from cooked hemoglobin [13].
LimitedStudied in womenHow often is not known

Skeletal fluorosis at very high intakes

Case reports: two women drinking 1 to 2 gallons of tea a day for decades developed skeletal fluorosis, with bone pain and very dense bones.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
A 49-year-old woman who drank 2 gallons of extra-strength instant tea a day since age 12 had serum fluoride of 120 μg/L (reference 20 to 80) and a spine bone density Z-score of +10.3. Her tea drink supplied about 44 mg of fluoride a day, 35 mg of it from the tea powder [12]. A 48-year-old woman who drank 1 to 2 gallons of brewed orange pekoe tea a day for over 30 years had severe bone and joint pain, kyphosis and a spine Z-score of +9.9, and her pain resolved over months after she stopped drinking tea and continued vitamin D [1].
Population
Two US women [12][1].
Sources
[12], [1]
Caveats
Two cases at intakes far above usual drinking. The authors state that tea from Camellia sinensis, including black tea, can contain substantial fluoride [12][1].

Mixed results1

LimitedHow often is not known

Iron stores in regular tea drinkers

Mixed results: a review found tea drinking was not linked to iron status where most people had adequate iron, with a negative link only where iron status was marginal.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In groups with frequent iron deficiency, tea drinking went with lower ferritin or hemoglobin, but the link disappeared after adjusting for other diet factors, except in one study where 40% of women were iron deficient. In groups with little iron deficiency, such as men and older adults, tea was not linked to lower ferritin or hemoglobin [14].
Population
16 observational studies of infants and children, premenopausal women, men and older adults [14].
Sources
[14]
Caveats
A narrative review of observational studies, searched up to 2001 [14].

Claims tested and not found

  1. That black tea lowers coronary artery disease. A meta-analysis of 13 studies found no link between black tea and coronary artery disease [4].
  2. That adding milk to tea removes its effect on iron absorption. Milk made little or no difference to tea's inhibition of iron absorption [10].
  3. That tea drinking lowers iron stores in people with adequate iron. In groups with little iron deficiency, tea was not linked to lower ferritin or hemoglobin [14].

Related

Green teaCaffeineCoffee

Sources

  1. Izuora K, Twombly JG, Whitford GM, et al. Skeletal fluorosis from brewed tea. The Journal of Clinical Endocrinology and Metabolism. 2011. https://doi.org/10.1210/jc.2010-2891
  2. Tang J, Zheng JS, Fang L, et al. Tea consumption and mortality of all cancers, CVD and all causes: a meta-analysis of eighteen prospective cohort studies. British Journal of Nutrition. 2015. https://doi.org/10.1017/s0007114515002329
  3. Inoue-Choi M, Ramirez Y, Cornelis MC, et al. Tea Consumption and All-Cause and Cause-Specific Mortality in the UK Biobank: A Prospective Cohort Study. Annals of Internal Medicine. 2022. https://doi.org/10.7326/m22-0041
  4. Wang ZM, Zhou B, Wang YS, et al. Black and green tea consumption and the risk of coronary artery disease: a meta-analysis. The American Journal of Clinical Nutrition. 2011. https://doi.org/10.3945/ajcn.110.005363
  5. Arab L, Liu W, Elashoff D. Green and black tea consumption and risk of stroke: a meta-analysis. Stroke. 2009. https://doi.org/10.1161/strokeaha.108.538470
  6. Greyling A, Ras RT, Zock PL, et al. The effect of black tea on blood pressure: a systematic review with meta-analysis of randomized controlled trials. PLOS ONE. 2014. https://doi.org/10.1371/journal.pone.0103247
  7. 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 and Function. 2021. https://doi.org/10.1039/d0fo02122a
  8. Zhao Y, Asimi S, Wu K, et al. Black tea consumption and serum cholesterol concentration: Systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition. 2015. https://doi.org/10.1016/j.clnu.2014.06.003
  9. Wang D, Chen C, Wang Y, et al. Effect of black tea consumption on blood cholesterol: a meta-analysis of 15 randomized controlled trials. PLOS ONE. 2014. https://doi.org/10.1371/journal.pone.0107711
  10. Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. British Journal of Nutrition. 1999. https://doi.org/10.1017/s0007114599000537
  11. Ahmad Fuzi SF, Koller D, Bruggraber S, et al. 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. The American Journal of Clinical Nutrition. 2017. https://doi.org/10.3945/ajcn.117.161364
  12. Whyte MP, Totty WG, Lim VT, Whitford GM. Skeletal fluorosis from instant tea. Journal of Bone and Mineral Research. 2008. https://doi.org/10.1359/jbmr.080101
  13. Disler PB, Lynch SR, Charlton RW, et al. The effect of tea on iron absorption. Gut. 1975. https://doi.org/10.1136/gut.16.3.193
  14. Temme EH, Van Hoydonck PG. Tea consumption and iron status. European Journal of Clinical Nutrition. 2002. https://doi.org/10.1038/sj.ejcn.1601309

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