Iron is a key element in the metabolism of almost all living organisms. In humans, iron is an essential component of hundreds of proteins and enzymes.

Most of the symptoms of iron deficiency are a result of the associated anemia, and may include fatigue, rapid heart rate, palpitations, and rapid breathing on exertion. Iron deficiency impairs athletic performance and physical work capacity in several ways. In iron deficiency anemia, the reduced hemoglobin content of red blood cells results in decreased oxygen delivery to active tissues

Increased iron utilization by the developing fetus and placenta, as well as blood volume expansion significantly, increase the iron requirement during pregnancy

Because iron from plant sources is less efficiently absorbed than that from animal sources, the U.S. Food and Nutrition Board has estimated that the bioavailability of iron from a vegetarian diet is only 10%, while it is 18% from a mixed diet. Therefore vegetarians need to increase their intake of iron.