Does drinking coffee or tea with a meal reduce the amount of iron your body absorbs from the meal? That question is the subject of this post and a matter of concern for two groups of people: those with too much iron, like hemochromatosis sufferers, and those with not enough iron, like people with anemia.
BTW, that headline is not a typo, it is a clever pun, or so I thought. Apologies if you already spotted the connections but it is based on a great line from the 1980s Melanie Griffith movie “Working Girl” in which Cynthia the secretary, played by the incomparable Joan Cusack, delivers the following line to Mr. Trainer, the handsome executive played by Harrison Ford: “Can I get ya anything, Mr. Trainer? Coffee? Tea? Me?”
So I replaced Me with Fe, which is the symbol for iron in the periodic table of the elements. That is most of the pun (perhaps not such a funny one since I felt I had to explain it). The other part is that the great Cusack acting dynasty, including Joan and her brother John, is Irish American, a group at considerably higher risk of hereditary hemochromatosis than the general population.
Anyway, moving on, there is sadly no easy answer to this tea-or-coffee-blocks-iron question. I certainly don’t think people who are trying to reduce their iron intake, like hemochromatosis sufferers, should not rely on tea of coffee to do the trick. It is true that several studies were done that showed drinking tea or coffee with a meal reduced iron absorption, but since then some studies have introduced a number of qualifications. The most relevant seems to be this one, which suggests that the blocking effect wears off with regular tea drinking: Proline-Rich Proteins Moderate the Inhibitory Effect of Tea on Iron Absorption in Rats.”
(Note: This would make a great Science Fair project. Get 10 people who regularly have tea or coffee with their dinner and compare their iron absorption with 10 who don’t, after having all of them eat the same meal.)
Another qualification to the “tea reduces iron absorption” theory is that the extent of the effect depends on the type of iron. Before my wife found out that she had hemochromatosis I used to think iron was iron, but biologically things are more complicated.
Apparently there is heme iron, which comes from animal flesh, and non-heme iron from plants (I realize that this is a gross over-simplification but I’m not trying to win the Science Prize here).
The non-heme form of iron is generally harder for the body to absorb. People with anemia probably know this already. As I understand it, eating a 12 ounce steak is going to get more iron into your system than consuming an equal weight of iron rich plant products.
The point is, researchers found that the blocking effect of tannin in tea and coffee affects only non-heme iron (as noted in this New York Times article). So, if you eat a medium-rare steak and a baked potato for dinner, a cup of tea or coffee may not do much to reduce the amount of iron your body gets from that meal, particularly if you are a regular tea drinker. (BTW, drinking orange juice with a breakfast steak will boost iron absorption, as will a cigarette with dinner.)
Of course, I’m not a scientist or doctor, but if you read your Google results carefully you can see that the original “tea-blocks-iron” stories go back further than the more recent caveats that suggest things are not that simple (like the 2005 paper on Proline-Rich Proteins cited earlier). The bottom line is that iron absorption depends on many factors and much more research needs to be done. In the meantime, there is one source of dietary information for hemochromatosis sufferers that I can recommend: The Hemochromatosis Cookbook by Cheryl Garrison. This is way more than just a cookbook and should be handed out to every newly diagnosed hemochromatosis sufferer.