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Apparently, coffee consumption can inhibit iron intake and in some cases is even linked to iron deficiency anemia, as Wikipedia says. It is unclear to me, however, how this happens. On the page about health effects of caffeine, I can't find anything about iron deficiency anemia. Some health blogs claim that both caffeine and other substances inhibit iron intake, but I couldn't find reliable sources (e.g. other than forum discussions and fact sheets like this which were compiled by a company selling coffee substitute) yet.

What substances in coffee inhibit the iron intake to which amount, and is decaffeinated coffee more beneficial in that respect than regular coffee?

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Does coffee inhibit the absorption of iron? The answer appears to be yes (see links and references below). So does tea. Note that this does not have to do with caffeine, but rather polyphenols, phytates found in them. So, my answer would be that both regular coffee and decaf coffee inhibit iron, but I don't know whether one does so more than the other. Also, if you add milk to your coffee, that may also have some effect, because calcium inhibits iron absorption.

It also depends on whether it's heme iron (mostly from animals) or non-heme iron (from plant sources, iron fortified foods). This matters if you eat primarily a vegetarian diet, because the recommended intake for non-heme iron is 1.8 times, compared to those who eat meat . NIH's Iron Dietary Supplement Fact Sheet compiled a great literature review on iron intake. See also CDC.

References

Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999;81:289–95.

Layrisse M1, García-Casal MN, Solano L, Barón MA, Arguello F, Llovera D, Ramírez J, Leets I, Tropper E. Iron bioavailability in humans from breakfasts enriched with iron bis-glycine chelate, phytates and polyphenols. J Nutr. 2000 Sep;130(9):2195-9.

Zijp IM1, Korver O, Tijburg LB. Effect of tea and other dietary factors on iron absorption. Crit Rev Food Sci Nutr. 2000 Sep;40(5):371-98.

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  • A good answer, +1 :-) but I'd like to add that the situation is a bit more complicated with milk, because while calcium might impair the absorption of iron to a certain extent, proteins from milk precipitate some of the tannines (i.e. polyphenols) and might make them less available to precipitate iron. I don't think there is a specific study about this, but the case with adding milk is definitely not as straightforward as is may seem at first. – Lucky Sep 11 '15 at 12:48

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