Tannins grab iron only in the same mash; spaced, the waves miss.
Full mechanism, in text
Tea & coffee tannins · lower plant iron
1 · Polyphenols grab iron on the spot, in the lumen
Tea tannins lock iron into an insoluble clump the moment they meet it in the gut fluid, so DMT1 cannot take it in.Tea tannins carry sites that grab metals. Binding does not need the body to process anything: the moment the two meet in gut fluid, iron is locked into an insoluble clump and cannot squeeze into DMT1, which only takes free ferrous iron.
2 · The real variable: are they in the same batch of chyme
The stomach releases food into the duodenum in batches, and polyphenols and iron only meet if they land in the same batch of chyme.Food leaves the stomach in batches. The stretch that arrives in the duodenum is exactly where iron is taken up. If they never meet, nothing happens.
3 · With the meal they mix; spaced, the waves miss
Strong tea with the meal mixes polyphenols and iron into the same batch of chyme, while tea drunk a little later travels in its own batch and misses it.Tea with the meal mixes polyphenols and this meal's iron into the same mash at the door. Drink after waiting a little and that meal's chyme has already walked past the uptake stretch; polyphenols travel with their own batch. The two waves miss.
4 · Not a constitution — almost only the stretch they sit together
Polyphenols block only the iron in this meal and build no iron-suppressing constitution, so keep tea apart from the iron-rich meal instead of quitting it.Polyphenols do not build an iron-suppressing constitution. They block this meal's iron, not your ability to make blood. A cup right after the meal is almost the same as with it. You do not have to give up tea; just don't let it mix with that iron-rich meal.