With the meal is when absorption is cut; between meals the worry largely goes.
Full mechanism, in text
Tea can block iron absorption
1 · Tannins bind plant iron in the lumen
In the gut, tea polyphenols bind non-heme iron from food into insoluble complexes, so that iron cannot be absorbed.Tea polyphenols carry galloyl groups that bind iron ions. In the gut they form insoluble complexes with non-heme iron from plants, eggs, and fortified foods, so the iron cannot be absorbed. This is not a myth. It has a clear mechanism.
2 · Heme iron uses another path and is barely affected
Tea affects iron from plants, eggs and fortified foods, while heme iron from red meat travels a different absorption pathway and is barely affected.This hits iron from plants, eggs, and fortified foods. Heme iron from red meat travels a different pathway and is barely affected. Iron-deficient, anemic, pregnant, or vegetarian people should care most. Everyday tea is basically nothing to worry about when stores are normal and the diet has meat.
3 · With the meal is when the cut lands on absorption
In the trial, black tea drunk with a meal cut plant-iron absorption from that meal by 79–94%, and the more polyphenols the drink held, the stronger the inhibition.Hurrell 1999 gave polyphenol drinks with a meal: black tea cut that meal's plant-iron absorption by 79–94%, and inhibition rose with the drink's polyphenol content. The drinks included black tea, several herb teas and cocoa, but not green tea. The point is not that tea is off limits. It is: do not drink strong tea with the meal where you are trying to absorb iron.
4 · Drink between meals and the worry largely goes
Separate tea from meals and iron supplements, and pair the meal with vitamin C, which boosts non-heme iron absorption and partly offsets the tannins.Tea is not off limits — just do not drink it with the iron meal.