Q.What is the best form of iron?

A. There are two forms of dietary iron, “heme” iron and “non-heme” iron. Heme iron is iron bound to hemoglobin (the oxygen transporting protein in blood); non-heme iron is not bound to hemoglobin. Heme iron is the most efficiently absorbed form of iron. The absorption rate of non-heme iron supplements, such as ferrous sulfate and ferrous fumarate, is 2.9% on an empty stomach and 0.9% with food. This is much less than the absorption rate of heme iron, as found in liver, which is as high as 35%. In addition, heme iron is without the side effects associated with non-heme sources of iron, such as nausea, flatulence, and diarrhea.

Despite the superiority of heme iron, non-heme iron salts are the most popular iron supplements. One reason is that even though heme-iron is better absorbed, it is easy to take higher quantities of non-heme iron salts so that the net amount of iron absorbed is about equal. In other words, if you take 3 mg of heme iron and 50 mg of non-heme iron, the net absorption for each will be about the same. The best form of non-heme iron is ferrous succinate. Consult a healthcare professional before taking iron supplements.