Black Tea
Camellia sinensis
A Strong clinical evidenceIts caffeine and L-theanine increase attention and alertness. Observational studies link regular tea drinking to lower cardiovascular risk.
Image: Herbadex Botanik Stüdyosu · Özel Üretim
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At a glance
Black tea is made by fermenting (oxidising) Camellia sinensis leaves; Turks drink the most tea per person in the world. A glass contains 40–70 mg of caffeine, which is well shown to improve attention and alertness. In large observational studies, people drinking 2–3 cups a day had slightly lower cardiovascular risk; this is not proof of cause and effect.
Updated: October 15, 2026
ℹ Compiled from standard pharmacognosy references and clinical literature summaries where no formal EMA monograph exists.
What is it used for?
A Strong clinical evidence
Strong clinical evidence: Supported by strong human clinical trials and well-established medicinal use monographs.
How do we rate evidence levels? →Caffeine and L-theanine increase attention and alertness. [2]
B Limited clinical evidence
Limited clinical evidence: Supported by small-scale human clinical studies, though sample size and study quality are limited.
How do we rate evidence levels? →Observational studies link regular tea drinking to lower cardiovascular disease risk. [2]
How is it used?
Tea
Steep in a teapot for 5–10 minutes; avoid very strong and very hot tea.
Amount: 2–4 glasses daily
[2]Safety & interactions
- Very hot drinks (over 65 °C) increase the risk of oesophageal cancer; let tea cool a little.
- Tea tannins reduce iron absorption; people with iron deficiency should not drink it with meals.
- In pregnancy, keep caffeine under 200 mg a day (about 3–4 light glasses).
- People with sleeplessness or palpitations should avoid it in the evening.
Drug interactions
| Medicine / substance | Effect | Severity |
|---|---|---|
| Iron supplements | Reduces absorption; leave 1–2 hours apart. [1] | Moderate |
| Other caffeinated products, stimulant drugs | Caffeine effects may add up. [1] | Minor |
| Lithium, clozapine, theophylline | Caffeine may affect their levels. [1] | Minor |
Side effects
- Sleeplessness, palpitations (in excess)
- Heartburn
- Tooth staining
⚕ When to see a doctor
- If high fever, shortness of breath or purulent/bloody phlegm develops
- If symptoms do not improve within 1–2 weeks or worsen
- If severe abdominal pain, jaundice, rash or allergic reaction occurs
Did you know?
Turks drink about 3 kg of tea per person a year, the highest in the world. [2]
Frequently asked questions
How many glasses of tea a day?
For healthy adults the caffeine limit is about 400 mg, roughly 6–8 glasses of tea.
Does tea cause iron deficiency?
Drunk with meals it reduces iron absorption; between meals is better.
Light or strong tea?
Light tea has less caffeine and tannin; better for people with iron deficiency or a sensitive stomach.
Sources
- Herbs at a Glance: Evidence-Based Fact Sheets on Botanical ProductsNIH NCCIH · 2024
- EFSA Compendium of Botanicals Reported to Contain Naturally Occurring Substances of Possible ConcernEFSA · 2022
Cite This Page
Black Tea (Camellia sinensis). Herbadex — Doğal Şifa Rehberi (2026). https://herbadex.com/en/herb/black-tea/
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