tannins
3 interactions related to tannins
black tea + iron
Black tea is rich in polyphenols (tannins) that bind iron in the digestive tract. When the two are taken together, less of the iron your body needs gets absorbed.
peppermint tea + iron
Peppermint tea is rich in plant polyphenols and tannins (including rosmarinic acid) that bind non-heme iron in the gut, forming insoluble complexes the body cannot absorb. Human studies show peppermint tea substantially reduces non-heme iron absorption from a meal, placing it among the stronger natural inhibitors. Heme iron from meat, poultry, and fish is not affected.
oolong tea + iron
Oolong tea is partially oxidised and contains the same families of iron-binding polyphenols found in green and black tea, including catechins and theaflavins. These polyphenols can bind non-heme iron in the gut and lower how much is absorbed when tea is taken with iron-rich meals or supplements. The effect is well documented for green and black tea; for oolong specifically it is a reasonable extrapolation of the same mechanism rather than a directly measured result.