How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Black tea
In trials, 4 to 5 cups of black tea per day slightly lower blood pressure (−1.8 mmHg) and LDL cholesterol, and improve arterial flexibility. In cohorts, drinking tea is associated with fewer deaths and strokes. Taken during meals, it inhibits iron absorption.
Benefits
- Blood pressure: in 11 trials (378 people, 4 to 5 cups per day), black tea lowered systolic blood pressure by 1.8 mmHg and diastolic pressure by 1.3 mmHg.
- Cholesterol: in adults with slightly elevated cholesterol, 5 cups per day in a low-fat diet lowered LDL by 7.5% compared to a placebo beverage, and by 11.1% compared to the same placebo with added caffeine.
- Arteries: in 50 coronary patients, 900 mL of black tea per day for 4 weeks, and even 450 mL two hours before measurement, improved brachial artery dilation; water had no effect.
- Dose and arteries: in healthy men, artery dilation increased from 7.8% to 10.3% depending on the dose of black tea; less than one cup a day was already enough to increase it.
- Platelets and inflammation: in 75 healthy men, 6 weeks of black tea versus placebo reduced platelet activation and CRP (0.76 versus 0.97 mg/L).
- Mortality: in the UK Biobank (498,043 adults, where black tea dominates), 2 to 3 cups per day were associated with 13% fewer deaths than zero cups, over 11 years.
- Stroke: 3 or more cups of tea per day, black or green, were associated with 21% fewer strokes in a cohort meta-analysis.
Precautions
Iron: tea limits the absorption of non-heme iron (found in plants); observational studies find less iron in the blood or more anemia in tea drinkers. No restriction is necessary if you are not iron deficient. If you eat little meat or fish and little vitamin C, iron absorption can be problematic: the authors therefore advise drinking tea between meals rather than with meals. Limitations: coronary heart disease: out of 13 studies, black tea was not associated with fewer coronary diseases (relative risk of 0.92, non-significant); only green tea was linked to it. In smokers, 6 cups of black or green tea per day did not change blood cholesterol or antioxidant vitamins. Cohorts are considered of low evidence, and the studies most at risk of bias found the strongest links; the UK Biobank did not measure cup size or tea strength. Trials are small (fewer than 400 people) and short, and effects on blood pressure remain in the range of 1 to 2 mmHg.
Recommended dosage
4 to 5 cups of black tea per day in trials on blood pressure and cholesterol; 2 to 3 cups or more in cohorts.
How to take it
- Quantity: 4 to 5 cups per day in trials; in the UK Biobank, the decrease in deaths appeared starting from 2 cups.
- Duration: 4 to 6 weeks in trials on arteries and platelets; for blood pressure, the effect was more pronounced beyond 3 months.
- If you are iron deficient: drink your tea at least one hour after the meal; this delay halved its effect on iron absorption (from 37.2% to 18.1% less iron).
- With the meal: the meat, fish, and vitamin C in the meal offset the inhibitory effect of tea on iron, even in large quantities.
- Black or green: on blood pressure, green tea performed slightly better than black tea in a meta-analysis of 5 trials.
Did you know?
Timing matters more than quantity for iron: drinking tea one hour after a meal rather than with it halved its effect on iron absorption, from 37.2% to 18.1% less iron.
What the studies say
This review and meta-analysis of 39 studies confirms that daily tea consumption, including black tea, is associated with a reduced risk of cardiovascular disease, stroke, and all-cause mortality. Each additional cup of tea per day is linked to an average 4% decrease in the risk of cardiovascular mortality and a 4% decrease in the risk of stroke. These benefits are more pronounced in the elderly.
Chung M, Zhao N, Wang D, Shams-White M, Karlsen M, Cassidy A, Ferruzzi M, Jacques PF, Johnson EJ, Wallace TC. — Advances in nutrition (Bethesda, Md.) (2020) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more