Humans can get iron from shots (injection) or IV (intravenous). They can also get iron from blood transfusions or by consuming (eating) iron that is in their food, or iron pills.
People consume two types of iron: non-heme and heme
iron comes primarily from plants and heme iron comes primarily from meat. Plants can contain tiny traces of heme iron but not enough to make a difference and as a rule, these plants are not types that we eat.
Meat contains both types of iron. About 55-60% of the iron in meat is non-heme the rest is heme iron.
Non-heme iron represents the majority of iron humans consume in their diets and is the type of iron in most supplements. Non-heme type of iron is found in greatest quantities in grains such as rice, wheat, and oats. Non-heme iron is also found in nuts, fruits, vegetables, most iron pills, fortified foods, or contaminant iron such as from water, soil or cooking utensils. Meat also contains non-heme iron.
Unlike heme iron, non-heme iron must be changed before it can be absorbed.
Meat, especially red meat is the best source of heme iron
. When we eat meat we consume the blood proteins, the hemoglobin and myoglobin contained in the flesh of the animal. Heme iron is easily absorbed by the body and the best source of iron for people who are iron deficient. Too much heme iron in the diet can increase the risk of disease for some people with abnormal iron metabolism such as hemochromatosis.
For persons with normal iron metabolism only 20 to 25 percent of the heme iron consumed is actually absorbed. For example, a four-ounce hamburger contains about 3 milligrams of iron; about 1.2 milligrams are heme and about 1.8 milligrams are non-heme. The amount of heme iron absorbed from that 4 oz hamburger would be approximately a third of a milligram. Persons with abnormal iron metabolism, such as hereditary hemochromatosis can absorb up to four times the iron as that of a person with normal metabolism. Therefore 80-100% of heme iron can be absorbed or approximately 1.2 milligrams from the same 4oz hamburger!
Many substances can reduce the amount of non-heme iron we absorb; these substances include tannins in coffee or tea, dairy, phytates (fiber), eggs and some types of chocolate. Calcium can impair the absorption of both non-heme and heme iron. Therefore if a person needs more iron, he or she should avoid these items to improve the amount of iron absorbed. But if a person has a problem of too much iron, he or she can use these items to help lower the amount of iron absorbed.
Read more about iron absorption in the diet section