Black tea: a small drop in blood pressure and a large cut in iron absorption

Black tea lowers blood pressure, by very little. A meta-analysis of 13 randomized trials found it cut systolic pressure by 1.04 mmHg (95% CI 0.03 to 2.05) and diastolic by 0.59 mmHg compared with control, with no sign that more tea did more. The same quality of evidence finds no benefit for total cholesterol. A meta-analysis of 15 trials found no significant change, and an LDL drop of 5.57 mg/dL in healthy people lost significance under the more cautious random-effects model. The larger effect is on iron. In a stable-isotope study in young Indian women, 1 or 2 cups of black tea with a rice meal cut iron absorption by 49 and 66 percent in women with normal iron stores. In women with iron deficiency anemia the cuts were 59 and 67 percent, measured over single meals in two groups of 10.

Every statement here is tied to a source. The badge says what kind of evidence stands behind it: A is a meta-analysis or systematic review, E is the position of an expert body without its own analysis. How we verify →

The numbers, per 3.5 oz (100 g)

USDA entry	kcal	Fat	Carbs
Beverages, tea, black, brewed, prepared with distilled water	1	0 g	0.3 g
Beverages, tea, black, brewed, prepared with tap water	1	0 g	0.3 g
Beverages, tea, black, brewed, prepared with tap water, decaffeinated	1	0 g	0.3 g
Beverages, tea, black, ready to drink	0	0 g	0 g
Beverages, tea, black, ready to drink, decaffeinated	38	0 g	8.75 g
Beverages, tea, black, ready to drink, decaffeinated, diet	0	0 g	0.83 g
Beverages, tea, black, ready-to-drink, lemon, diet	1	0 g	0.22 g
Beverages, tea, black, ready-to-drink, lemon, sweetened	45	0.22 g	10.8 g
Beverages, tea, black, ready-to-drink, peach, diet	1	0 g	0.25 g

These are the USDA entries that are black tea, not foods made from it; they differ in cut, part, pack or preparation. Linked names have a page with the full profile and per-portion figures.

As people eat it, per 3.5 oz (100 g)

As eaten	kcal	Fat	Carbs
Tea, hot, leaf, black	1	0 g	0.3 g
Tea, hot, leaf, black, decaffeinated	1	0 g	0.3 g
Tea, iced, bottled, black	45	0.22 g	10.8 g
Tea, iced, bottled, black, decaffeinated	38	0 g	8.75 g
Tea, iced, bottled, black, decaffeinated, diet	0	0 g	0.83 g
Tea, iced, bottled, black, decaffeinated, unsweetened	1	0 g	0.3 g
Tea, iced, bottled, black, diet	1	0 g	0.22 g
Tea, iced, bottled, black, unsweetened	0	0 g	0 g
Tea, iced, brewed, black, decaffeinated, pre-sweetened with low calorie sweetener	2	0 g	0.68 g
Tea, iced, brewed, black, decaffeinated, pre-sweetened with sugar	32	0.02 g	7.94 g
Tea, iced, brewed, black, decaffeinated, unsweetened	1	0 g	0.3 g
Tea, iced, brewed, black, pre-sweetened with low calorie sweetener	2	0 g	0.68 g

All 22 (10 more)

As eaten	kcal	Protein	Fat	Carbs	Fiber
Tea, iced, brewed, black, pre-sweetened with sugar	32	0 g	0.02 g	7.94 g	0 g
Tea, iced, brewed, black, unsweetened	1	0 g	0 g	0.3 g	0 g
Tea, iced, instant, black, decaffeinated, pre-sweetened with low calorie sweetener	3	0.03 g	0 g	0.72 g	0 g
Tea, iced, instant, black, decaffeinated, pre-sweetened with sugar	32	0.06 g	0.02 g	7.89 g	0 g
Tea, iced, instant, black, decaffeinated, unsweetened	1	0.06 g	0 g	0.17 g	0 g
Tea, iced, instant, black, pre-sweetened with low calorie sweetener	2	0.02 g	0 g	0.44 g	0 g
Tea, iced, instant, black, pre-sweetened with sugar	30	0.01 g	0.05 g	7.31 g	0.1 g
Tea, iced, instant, black, pre-sweetened, dry	401	0.12 g	0.73 g	98.5 g	0.7 g
Tea, iced, instant, black, unsweetened	1	0.02 g	0 g	0.23 g	0 g
Tea, iced, instant, black, unsweetened, dry	315	20.2 g	0 g	58.7 g	8.5 g

USDA Food and Nutrient Database for Dietary Studies (FNDDS, release 2024-10-31): black tea as it is prepared and served, from the recipes behind the national dietary survey, rather than a single laboratory sample.

How much is actually in it

Laboratory data from 19 processing experiments suggest that the withering step changes black tea catechins, theanine and pigments, with conventional indoor withering tending to deplete catechins. — Nineteen studies (n = 19 studies) Evidence D source
Direction varies by method; extreme heterogeneity
The UK composition table lists brewed black tea as 99.5 g water per 3.5 oz (100 g) with trace energy, 27 mg potassium and 0.15 mg manganese. — CoFID 2021, food code 17-165, tea, black, infusion, average Evidence E source
Energy trace (2 kJ), protein 0.1 g, potassium 27 mg, manganese 0.15 mg, magnesium 2 mg, folate 3 mcg per 3.5 oz (100 g)

What a real portion looks like

In the US dietary survey a cup of hot black tea is coded at 240 g, and an unspecified amount at 360 g. — USDA FNDDS portion weights, Tea, hot, leaf, black (code 92302000) Evidence E source
1 cup 240 g; quantity not specified 360 g; small 360 g, medium 480 g, large 600 g

What your body absorbs

In a stable-isotope trial in young Indian women, 1 or 2 cups of black tea with a rice meal cut iron absorption by 49% and 66% in iron-replete women and by 59% and 67% in women with anemia. — 2 groups of 10 subjects with iron deficiency anemia (IDA) and 10 subjects who were iron replete (n = 20) Evidence B source
Iron-replete -49% (1 cup), -66% (2 cups); IDA -59%, -67%
In a randomized crossover study in healthy volunteers, taking a 0.4 mg folic acid tablet with black tea instead of water cut peak serum folate by 38.6% and total exposure by 17.9%. — healthy volunteers Evidence B source
Cmax -38.6%, AUC -17.9% versus water
In a double-blind crossover RCT, a drink with 55 mg black tea polyphenols three times a day for 10 days raised fecal fat excretion from 5.51 to 6.87 g per 3 days. — participants Evidence B source
Total fecal lipid 5.51 to 6.87 g/3 d vs control

What cooking and storage change

A review of 88 studies found fluoride release rises with brewing time, with black tea bags reaching 6.01 mg/L after 30 minutes and black tea averaging 2.73 mg/L. — 88 global studies (n = 88 studies) Evidence C source
Brewing time r = 0.82; black tea 2.73 mg/L; children 4-8 y EDI 0.078 mg/kg/day

What it does to your health

By a meta-analysis of 13 RCTs, black tea lowered systolic blood pressure by 1.04 mmHg and diastolic by 0.59 mmHg versus control. — adults (n = 13 trials) Evidence A source
SBP -1.04 mmHg (95% CI -2.05 to -0.03), DBP -0.59 mmHg (95% CI -1.05 to -0.13)
Observational data from 14 cohorts with 958,477 people link the highest black tea intake to an 11% lower coronary heart disease risk. — 16,990 CHD cases among 958,477 participants (n = 958477) Evidence C source
RR 0.89 (95% CI 0.79 to 0.99), I2 50.6%; 2 cups/day RR 0.95, 4 cups 0.91
In a double-blind crossover RCT in 24 adults, a black tea drink with 110 or 220 mg polymerized polyphenols lowered the 60-minute glucose response to sucrose versus placebo. — Twenty-four subjects, male and female aged 20-60 years, normal and pre-diabetic (n = 24) Evidence B source
Glucose AUC 0-60 min in normal subjects 3,232 and 3,295 vs 3,652 mg.min/dL (p=0.016); no insulin difference

Safety, limits and interactions

A meta-analysis of 21 surveys found mycotoxins in 89.2% of black tea samples, the most contaminated tea type, with lower rates in high-income countries. — 21 included studies (n = 21 studies) Evidence C source
Black tea contamination 89.2% (95% CI 73.9% to 98.3%)
According to the FDA, 400 mg of caffeine a day is an amount not generally associated with negative effects for most adults. — most adults Evidence E source
400 mg/day

What people believe that the data does not support

By a meta-analysis of 15 RCTs, black tea did not lower total cholesterol, and the LDL drop of 5.57 mg/dL in healthy people lost significance under a random-effects model. — healthy subjects or patients with coronary artery diseases (n = 15 trials) Evidence A source
TC no significant change; LDL-C -5.57 mg/dL (95% CI -9.49 to -1.66) fixed, -4.56 (95% CI -10.30 to 1.17) random
In an RCT in 21 healthy men, 4 or 6 mugs of black tea a day (168 or 252 mg caffeine) hydrated as well as the same amount of water. — Healthy resting males (n 21) (n = 21) Evidence B source
No significant differences in blood or urine hydration markers
The EU refused to authorize the claim that black tea helps you focus attention. — EU Register on nutrition and health claims Evidence E source
Non-authorized
The EU refused to authorize the claim that black tea improves endothelium-dependent vasodilation for healthy blood flow. — EU Register on nutrition and health claims Evidence E source
Non-authorized

Who this works differently for

Observational data from 39 cohort publications link each extra daily cup of tea to a 4% lower cardiovascular death risk, with stronger links in older adults. — generally healthy adults (n = 39 cohort publications) Evidence C source
Per cup: CVD mortality -4%, all-cause -1.5%; elderly CVD mortality RR 0.89 (95% CI 0.83 to 0.96)
In a pilot RCT in nursing women, 10 fl oz (300 mL) decaffeinated black tea daily for 6 days left no detectable tea catechins in breast milk. — Healthy nursing women (n = 18) Evidence B source
Catechins not detected in milk; antioxidant capacity unchanged
In a survey of 1112 Polish pregnant and breastfeeding women, black tea was a main caffeine source, and 26% of pregnant women exceeded the 200 mg daily EFSA limit. — 1112 women, of whom 401 were pregnant and 711 were breastfeeding (n = 1112) Evidence C source
Median caffeine 114.5 mg/d pregnant, 193.7 mg/d breastfeeding; 73.8% of pregnant within 0-200 mg/d

What is still unknown

Observational data show no link between the highest black tea intake and prostate cancer risk. — Thirteen studies (n = 13 studies) Evidence C source
OR 0.99 (95% CI 0.82 to 1.20)

The bottom line

Observational studies look more encouraging and prove less. Across 14 cohorts with 958,477 people, the highest black tea intake was linked to an 11 percent lower risk of coronary heart disease (relative risk 0.89, 95% CI 0.79 to 0.99), and the link appeared in European studies and not in American ones. Cohorts that pooled black and green tea link each extra daily cup to a 4 percent lower risk of cardiovascular death, evidence their authors rate low to moderate. For prostate cancer, 13 studies found no association (odds ratio 0.99). The EU refused to authorize claims that black tea helps you focus or improves blood flow through the vessel lining, which means the evidence was judged insufficient when assessed. The worry that tea dehydrates you is a myth. In 21 healthy men at rest for 12 hours, 4 or 6 mugs of black tea with milk, holding 168 or 252 mg of caffeine, hydrated as well as the same amount of water. Several cautions come from the cards. Tea drunk with a meal cuts iron absorption, which matters most for anyone with iron deficiency anemia. In a crossover study in healthy volunteers, a single 0.4 mg folic acid tablet taken with black tea instead of water reached a 38.6 percent lower peak in blood folate, in a study that used a tea extract. The FDA cites 400 mg of caffeine a day as generally free of negative effects for most adults, a figure that does not cover pregnancy. In a survey of 1,112 Polish pregnant and breastfeeding women, black tea was a main caffeine source and 26 percent of the pregnant women went over EFSA's 200 mg a day, by self-reported 3-day recall. In 18 nursing women drinking 10 fl oz (300 mL) of decaffeinated black tea daily for 6 days, tea catechins did not appear in breast milk. Fluoride rises the longer tea brews, and black tea bags reached 6.01 mg/L after 30 minutes in a review of 88 analytical studies. That review names black tea as a fluoride risk for children aged 4 to 8, at an estimated intake of 0.078 mg per kg a day. A meta-analysis of 21 surveys detected mycotoxins in 89.2 percent of black tea samples, a detection rate that says nothing about amounts above safety limits.

Compared with other foods

Black tea vs green tea — calories · which is healthier

All food comparisons

Questions about black tea, answered from the trials

Does tea lower blood pressure?

Related foods

Tea and iron: in one small study, an hour's gap kept the iron

Guides that discuss this food

Polyphenols: what tea, fruit and supplements actually do

Sources

btea-daily-r1-14 · meta-analysis (lab)
Nineteen studies met the inclusion criteria, mostly published within the last 5 years and concentrated in China. Across studies, withering altered catechins, amino acids (including theanine), tea pigments, alkaloids, and organic acids, with substantial between-study variability indicating strong context dependence. Conventional natural indoor withering tended toward net catechin depletion
Compr Rev Food Sci Food Saf, 2026 · checked 2026-09-29
btea-daily-r1-16 · reference dataset
CoFID 17-165 Tea, black, infusion, average: Energy 2 kJ · Protein 0.1 g · Water 99.5 g · Potassium 27 mg · Manganese 0.15 mg · Magnesium 2 mg · Folate 3 µg
CoFID 2021, Public Health England (OGL v3.0), code 17-165 · checked 2026-09-29
btea-daily-r1-17 · reference dataset
FNDDS 92302000 Tea, hot, leaf, black (fdc 2710488): 1 fl oz 30 g · 1 cup 240 g · Quantity not specified 360 g · 1 small 360 g · 1 medium 480 g · 1 large 600 g
USDA FNDDS 2021-2023 (FoodData Central) · checked 2026-09-29
btea-daily-r1-07 · RCT (absorption)
Two stable-isotope iron absorption studies were made in 2 groups of 10 subjects with iron deficiency anemia (IDA) and 10 subjects who were iron replete (control subjects). In study 1, the reference rice meal was fed alone or with 1 or 2 cups of black tea. ... The consumption of 1 or 2 cups of tea decreased iron absorption in the control subjects by 49% (P < 0.05) or 66% (P < 0.01), respectively, and in the IDA group by 59% or 67% (P < 0.001 for both), respectively.
Am J Clin Nutr, 2008 · checked 2026-09-29
btea-daily-r1-08 · RCT (pharmacokinetic)
At the 0.4 mg folic acid dose, green and black tea reduced the mean C(max) of serum folate by 39.2% and 38.6%, and the mean AUC(0 --> infinity) by 26.6% and 17.9%, respectively.
Biopharm Drug Dispos, 2008 · checked 2026-09-29
btea-daily-r1-09 · RCT
In this randomized, placebo-controlled, double-blind, crossover study, in the first test period participants were asked to drink either a beverage containing 55 mg BTP or a control beverage without BTP 3 times a day for 10 d. ... Total lipid excretion increased from 5.51±1.73 to 6.87±1.91 g/3 d after BTP intake in comparison with intake of the control beverage.
Biol Pharm Bull, 2016 · checked 2026-09-29
btea-daily-r1-13 · scoping review
Brewing time strongly correlates with F- release (r = 0.82, p < 0.001), with black tea bags reaching 6.01 mg/L after 30 min. ... F- concentrations vary significantly by tea type: brick tea (4.78 mg/L) > black tea (2.73 mg/L) > green tea (1.37 mg/L) > white tea (0.49 mg/L) > herbal tea (0.17 mg/L). Brick tea consumption exceeds WHO guidelines across all age groups, while black tea poses risks for children (4-8 years: EDI 0.078 mg/kg/day) and adults in high-consumption regions.
Crit Rev Food Sci Nutr, 2025 · checked 2026-09-29
btea-daily-r1-01 · meta-analysis of RCTs
A total of 13 trials, including 22 study arms were eligible for inclusion in the final quantitative analysis. It was observed that black tea supplementation significantly reduced SBP (WMD - 1.04 mmHg; 95% CI - 2.05 to -0.03; and P = 0.04) and DBP (WMD - 0.59 mmHg; 95% CI - 1.05 to -0.13; and P = 0.01) compared to the control.
Food Funct, 2021 · checked 2026-09-29
btea-daily-r1-03 · meta-analysis of cohorts
A total of 14 studies, with 16,990 CHD cases among 958,477 participants, were included. The overall results showed a significant 11 % reduction in CHD risk with the highest black tea consumption [summary relative risk (RR): 0.89; 95 % confidence interval (CI): 0.79, 0.99]; there was a significant heterogeneity (P = 0.007, I2 = 50.6 %). In the subgroup analysis by region, the protective effect was observed in the European, but not in the USA.
Nutr Metab Cardiovasc Dis, 2026 · checked 2026-09-29
btea-daily-r1-06 · RCT
Twenty-four subjects, male and female aged 20-60 years, normal and pre-diabetic, randomly ingested a sucrose solution with a low dose (110 mg BTPP), a high dose (220 mg BTPP) of black tea drink or a placebo drink (0 mg BTPP). ... The drink containing low dose and high dose BTPP significantly decreased incremental blood glucose area under the curve (AUC) after sucrose intake compared with placebo in the normal (T0-60 min 3,232±356 vs 3,295±312 vs 3,652±454 mg.min/dL; p=0.016)
Asia Pac J Clin Nutr, 2017 · checked 2026-09-29
btea-daily-r1-12 · meta-analysis of contamination surveys
Regarding tea categories, black tea was the most contaminated type, with a rate of 89.2% (95% CI: 73.9%-98.3%), followed by green tea with a rate of 67.3% (95% CI: 37.0%-91.2%). The contamination prevalence was higher in studies conducted before 2018 than those of the 2018-2022 period, and lower in high-income countries compared to middle and low-income countries
Mycotoxin Res, 2026 · checked 2026-09-29
btea-daily-r1-20 · agency position
For most adults, the FDA has cited 400 milligrams a day — that's about two to three 12-fluid-ounce cups of coffee — as an amount not generally associated with negative effects.
U.S. FDA, Spilling the Beans: How Much Caffeine is Too Much?, 2024 · checked 2026-09-29
btea-daily-r1-02 · meta-analysis of RCTs
The consumption of black tea did not significantly lower TC concentrations either in healthy subjects or patients with coronary artery diseases based on both fixed-effects and random-effects analysis. ... The pooled net change of LDL-C in healthy participants was -5.57 mg/dL (95% CI, -9.49 to -1.66 mg/dL; P = 0.005) in fixed-effects analysis and -4.56 (95% CI, -10.30 to 1.17 mg/dL; P = 0.12) in random-effects analysis.
PLoS One, 2014 · checked 2026-09-29
btea-daily-r1-11 · RCT
Healthy resting males (n 21) were recruited from the general population. ... The test beverages, provided at regular intervals, were 4 × 240 ml black (i.e. regular) tea and 6 × 240 ml black tea, providing 168 or 252 mg of caffeine. ... revealed no significant differences between tea and water for any of the mean blood or urine measurements.
Br J Nutr, 2011 · checked 2026-09-29
btea-daily-r1-18 · regulatory decision
POL-HC-6325 Black tea from Camellia sinensis Black tea helps you to focus attention -/- Non-authorised
EU Register on nutrition and health claims, claim POL-HC-6325, snapshot 2026-09-21 · checked 2026-09-29
btea-daily-r1-19 · regulatory decision
POL-HC-8512 Black tea from Camellia sinensis Improves endothelium-dependent vasodilation, which contributes to healthy blood flow -/- Non-authorised
EU Register on nutrition and health claims, claim POL-HC-8512, snapshot 2026-09-21 · checked 2026-09-29
btea-daily-r1-04 · meta-analysis of cohorts
Linear meta-regression showed that each cup (236.6 mL) increase in daily tea consumption (estimated 280 mg and 338 mg total flavonoids/d for black and green tea, respectively) was associated with an average 4% lower risk of CVD mortality, a 2% lower risk of CVD events, a 4% lower risk of stroke, and a 1.5% lower risk of all-cause mortality. Subgroup meta-analysis results showed that the magnitude of association was larger in elderly individuals for both CVD mortality (n = 4; pooled adjusted RR: 0.89; 95% CI: 0.83, 0.96; P = 0.001)
Adv Nutr, 2020 · checked 2026-09-29
btea-daily-r1-10 · RCT (pilot)
Healthy nursing women were supplemented with either 250 mL of a soy drink (12 mg isoflavones; n = 18), 300 mL decaffeinated black tea (67 mg catechins; n = 18), or 300 mL water (n = 8, control) for 6 days. ... the major flavonoids constituents of black tea (catechin, epicatechin, and respective conjugates) could not be detected in milk samples.
Ann Nutr Metab, 2017 · checked 2026-09-29
btea-daily-r1-15 · cross-sectional
The maximum safe dose of caffeine in their diet is 200 mg per day, according to the European Food Safety Authority. ... The number of subjects who qualified for the study was 1112 women, of whom 401 were pregnant and 711 were breastfeeding. ... It was observed that the intake of 73.8% of pregnant women and 51.9% of breastfeeding women fit within the safe range (0-200 mg/d). The main sources of caffeine were ground coffee, black tea, and instant coffee.
Clin Nutr ESPEN, 2023 · checked 2026-09-29
btea-daily-r1-05 · meta-analysis of observational studies
For black tea, no statistically significant association was observed for the highest vs. non/lowest black tea consumption (OR = 0.99; 95% CI: 0.82-1.20).
Nutr Cancer, 2011 · checked 2026-09-29

Review. Reviewed on 2026-09-29 for evidence level, dose and population context, and claims a reader could misread. Bioma Learn has no human medical reviewer at this time, and we say so rather than invent one. Methodology. This is information, not medical advice.