Tea naturally contains polyphenols which are plant compounds praised for their antioxidant properties.
These same compounds can latch onto non-heme iron, the type found in most plant-based foods. When that happens, the body absorbs less of the mineral.
Tannins, which are abundant in black tea and present to varying degrees in other varieties, seem to strengthen this effect.
Even fairly mild brews may reduce absorption, though the exact mechanism is still being studied.
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Research published in Nature suggests that, in controlled settings, tea has sharply limited the amount of iron the gut could take up.
Not all teas work the same way
Different teas contain different levels of polyphenols and tannins, which means their impact varies.
- Black tea generally contains the most tannins.
- Green tea contains less but has its own group of polyphenols, catechins, that can also interfere with iron.
- Oolong typically sits between the two.
- Even herbal blends may influence absorption because many herbs naturally contain polyphenols.
A study in Frontiers in Nutrition has linked frequent green-tea drinking with lower ferritin levels, an indicator of reduced iron stores.
Fermented black tea may also dampen the absorption of certain supplemental iron forms, a study published in The Journal of Nutrition showed.
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Timing matters more than avoidance
For most people with low iron, giving up tea isn’t necessary. What appears to matter most is separating tea from meals and iron supplements.
Research published in Heliyon shows that drinking tea with food can significantly reduce iron uptake.
While another research published in The American Journal of Clinical Nutrition showed that waiting about an hour before or after eating may help the body absorb more.
Pairing iron-rich foods with vitamin C sources, such as oranges, peppers, or strawberries, can also boost absorption.
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Moderate tea consumption is still considered safe for most adults, but caffeine guidelines apply, particularly for pregnant individuals and children.
Sources: VeryWell Health, Nature, Frontiers in Nutrition, Heliyon, and The American Journal of Clinical Nutrition.
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