Several studies have found that coffee and other caffeinated drinks can reduce iron absorption.

One study found that drinking a cup of coffee with a hamburger meal reduced iron absorption by 39%. Drinking tea, a known inhibitor of iron absorption, with the same meal reduced iron absorption by a whopping 64% ( 3 ).

Another study found that drinking a cup of instant coffee with a bread meal reduced iron absorption by 60–90% ( 4 ).

What’s more, the stronger the coffee or tea, the less iron absorbed ( 3 ).

However, caffeine alone does not seem to be the main substance interfering with iron absorption.

In fact, one study found that caffeine itself only binds to about 6% of the iron from a meal. Given that this is a relatively small amount, other factors must affect iron absorption (5).

Furthermore, regular coffee consumption may also have an effect on iron storage levels.

A large study found that among elderly people, each weekly cup of coffee was associated with a 1% lower level of ferritin, a protein that indicates iron storage levels ( 6 ).

However, it’s important to remember that the effects of coffee and caffeine on iron absorption seem to depend on when you drink your coffee. For example, drinking coffee one hour before a meal had no effect on iron absorption ( 7 ).

Summary: Drinking coffee and other caffeinated beverages with a meal is associated with a 39–90% reduction in iron absorption. However, caffeine itself only binds a small amount of iron.