Whether you are anemic or are just low in iron, you should beware that what you see (i.e., the amount of iron printed on the label of your supplements) may not be what you get. The quantity of iron you take does not correlate with how much iron your body absorbs!  

   Many dietary factors inhibit iron absorption, including:

• Polyphenols in tea and coffee (from tannin derivatives of gallic acid)
• Oxalic acid in spinach, chard, berries, chocolate and tea, among others
• Phytates, or phytic acid, inositol hexaphosphate, or polyphosphate in maize, whole grains, legumes
• EDTA, a preservative
• Phosvitin, a protein found in egg yolks
• Nutrients such as calcium, calcium phosphate salts, zinc, manganese, and nickel

   So if you consume these nutrients around the same time you take your iron supplements, chances are your iron absorption is being decreased by a significant amount. Check out these stats: Polyphenols, such as those highly concentrated in tea and coffee, when consumed with a source of iron, have been shown to reduce iron absorption over 60%.[i] Coffee consumption, with a meal or right after, may reduce iron absorption by 40%.[ii]

   Phytates and oxalates use oxygen to bind many minerals, including not only iron, but also zinc, copper, and calcium. If you are taking any of these nutrients as supplements, you might want to make sure to limit your whole grain intake an hour before or two hours after you take your supplement(s). Also, iron appears to interact with zinc, calcium, phosphorus, and manganese, so if you take any of these supplements individually, try to take them at separate times, as far apart as possible. In multivitamins, the absorbed amount is usually less than indicated on the bottle due to the interactions of these minerals with each other and with some of the same receptors for absorption in the body. To optimize absorption of these divalent minerals, you may want to take them as separate supplements. Consult with your physician before taking or changing your vitamin and mineral regimen.  

   Here’s a helpful hint: To increase iron absorption from non-heme sources (sources other than meats, such as supplements), you can simultaneously consume Vitamin C (ascorbic acid) from foods or supplements or citric acid (found in citrus fruits). Ascorbic and citric acid act as reducing agents and help iron to remain soluble in the small intestine, thus enhancing nonheme iron absorption.

[i] Gropper SS, Smith JS, Groff JL. Advanced Nutrition and Human Metabolism. [4th Ed.] Thomson-Wadswoth, CA, USA. 2005:423-435.

[ii] Morck T, Lynch S, Cook J. Inhibition of food iron absorption by coffee. Am J Clin Nutr 1983;37:416-20.