Iron is part of hemoglobin, the oxygen-carrying component of the blood. Iron-deficient people tire easily because their bodies are starved for oxygen. Iron is also part of myoglobin, which helps muscle cells store oxygen.

The most absorbable form of iron, called "heme" iron, is found in fish, oysters, meat and poultry. Non-heme iron is found in dried fruit, molasses, leafy green vegetables, wine, and most iron supplements. Another source of iron can be found in acidic foods (such as tomato sauce) cooked in an iron pan.