Tannins — The Iron Blocker in Your Teacup
A cup of tea with an iron-rich meal can cut the iron you actually absorb by more than half.
science
Tannins are polyphenols — the same broad family of compounds responsible for the astringent, mouth-drying sensation in strong tea, red wine, and unripe fruit. They bind tightly to in the digestive tract, forming a complex the body cannot absorb. Unlike most anti-nutrients, tannins are largely heat-stable — boiling tea or coffee doesn't meaningfully reduce their iron-blocking effect.
This matters most for people already managing borderline status — particularly those eating plant-forward diets, where is already less bioavailable than the heme found in meat. A cup of black tea alongside a lentil dish can measurably blunt how much of that lentil actually gets absorbed.
The practical fix isn't avoidance — tannins are also legitimate antioxidants with their own benefits — it's timing. Separating tea and coffee from iron-rich meals by an hour in either direction allows absorption to proceed largely unimpeded, while still letting you enjoy your tea.
Tannins are heat-resistant — cooking does not neutralise their effect on absorption the way it does for lectins
Drink tea or coffee between meals rather than with them, especially if status is a concern
Vitamin C taken alongside an iron-rich meal can help counteract tannin binding, improving net absorption
This is a timing problem, not a reason to give up tea — tannins themselves have real antioxidant value