Nutrition Science and Everyday Application - beta v 0.1

536 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
Figure 9.20. Dietary sources of iron. Examples of good sources pictured include fortified cereal,
clams, spinach, lentils and red meat. Source: NIH Office of Dietary Supplements
The bioavailability of iron is approximately 14% to 18% from mixed diets and 5% to
12% from vegetarian diets. 2 Bioavailability is influenced by the dietary factors previously
mentioned, as well as iron status. The body has no physiological mechanism to excrete iron;
therefore, iron balance is tightly regulated by absorption. 2 When iron stores are low, more
dietary iron will be absorbed.
The majority of the body’s iron needs are not met by dietary sources, but rather by
recycling iron within the body (endogenous
sources). Ninety percent of daily iron needs are
met by recycling iron released from the breakdown of aging cells, mostly red blood cells. 2
Iron Deficiency and Toxicity
Iron deficiency is one of the most common nutrient deficiencies, affecting more than a third
of the world’s population. 3 Iron-deficiency anemia is a condition that develops from having
insufficient iron levels in the body, resulting in fewer and smaller red blood cells that contain
less hemoglobin. As a result, blood carries less oxygen from the lungs to cells. Iron-deficiency
anemia has the following signs and symptoms, which are linked to the essential functions of
iron in energy metabolism and blood health:
• Fatigue
• Weakness
• Pale skin
• Shortness of breath