Coffee, tea and iron

Morck and colleagues measured iron absorption in people without deficiency. A cup of coffee reduced iron absorption from a ground beef meal by 39%, compared with 64% for tea. In a test meal, absorption dropped from 5.88% to 1.64% with filter coffee and to 0.97% with instant coffee. Doubling the concentration of instant coffee lowered it to 0.53%. The most useful detail concerns timing: coffee consumed 1 hour before the meal had no effect, but coffee consumed 1 hour afterward interfered just as much as coffee consumed with the meal.

Hurrell and colleagues tested several polyphenol-rich drinks with a bread-based meal. All reduced iron absorption, with greater reductions at higher polyphenol levels: 50 to 70% for 20 to 50 mg of polyphenols per cup, and 60 to 90% for 100 to 400 mg. Black tea reduced absorption by 79 to 94%, peppermint by 84%, cocoa by 71% and chamomile by 47%. Adding milk made almost no difference.

As early as 1975, Disler and colleagues showed that tea inhibits iron absorption from iron solutions, bread and a rice meal, even in the presence of vitamin C. They attribute this to the formation of insoluble complexes between iron and tannins. In contrast, tea did not interfere with iron absorption from cooked hemoglobin, which is similar to the iron in meat. Caffeine-free herbal teas also strongly inhibit absorption: polyphenol content matters, not caffeine. A pure caffeine capsule was not tested in these trials, which is why the checker distinguishes between “Caffeine” and “Coffee or tea”.

If you take an iron supplement or your iron comes mainly from plants and your ferritin is low: drink coffee or tea at least 1 hour before your meal, not during it or in the hour afterward. Herbal teas count too. For your intake, see the table of iron-rich foods , our article on low ferritin and our comparison matcha or coffee.

These trials measure absorption from test meals, mostly in people without a deficiency. They do not measure the effect on iron stores over months, which depends on the rest of the diet. Timing was tested only for coffee, 1 hour before and 1 hour after. If you eat a varied diet and have normal ferritin levels, nothing in these data requires you to stop drinking coffee or tea.