Black Tea

Food · Drink · Food, Typed Supps

About a third the caffeine of coffee, with tannins that blunt iron absorption.

Stage by stage

Intake (Brewed infusion): Steeping extracts caffeine and polyphenols together; longer brews raise both.
Gut interaction (Small intestine): Galloylated tannins chelate non-heme iron, forming insoluble complexes that are not absorbed.
Central action (Adenosine receptors): Caffeine blocks adenosine receptors, at roughly a third the dose of an equivalent coffee.
Fluoride (Skeletal uptake): Fluoride concentrated in the leaf is absorbed and incorporated into bone and enamel.

Timing

Keep an hour clear of iron-rich meals or iron supplements. Afternoon cups carry the same sleep caution as coffee, at a lower dose.

Time to effect

30–60 min: Alertness rises with plasma caffeine.
Same meal: The iron-absorption effect applies only to the meal it is drunk with.

Allergens

None of the fourteen major allergens. Derived from what this food is, not from a product label.

Eating patterns

Fits: Vegan, Vegetarian, Pescatarian, Halal, Kosher, Gluten-free. Depends on the product: Keto, Low-FODMAP.

Satiety

Not scored: the satiety index is measured on 240 kcal servings, and nobody eats a 240 kcal serving of this. The question does not apply rather than the answer being unknown.

Cost band

Pricey — roughly £30 per kg, as a band midpoint rather than a price.

Key nutrients

Nutrition per 100g

Calories: 0
Protein: 0.1g

Food vs. supplement

Brewed tea and concentrated green tea extract are not equivalent: EFSA identified a hepatotoxicity signal for catechin doses at and above 800 mg EGCG/day, a level drinking tea does not reach.

Kitchen tip

Adding lemon (vitamin C) to tea partly offsets its inhibition of non-heme iron; adding milk does not.

Common myth

“Tea blocks iron, so you should not drink it if you are low.” In reality: It inhibits non-heme iron in the same meal, not iron generally, and not systemically. Moving tea an hour away from iron-rich food or a supplement removes essentially all of the effect — and vitamin C in the meal offsets much of the rest.