Iron is considered a trace mineral[1] because our body needs only small amounts of it when compared to other nutrients. However, it is an essential nutrient, and inadequate intakes can lead to body malfunction. Even though it is needed in tiny doses (around 18 mg for women and 8 mg for men), many people still can’t manage to get enough of it through diet. That’s because iron absorption is relatively low – around 10% to 15% of the total iron content of the food.
There are two forms of iron: heme iron and nonheme iron. Heme iron is found in animal flesh, mainly in red blood cells and muscle cells. This form of iron is well absorbed by the body, which makes animal foods our best iron source. Iron can also be found in plant foods such as potatoes, spinach, peas and legumes. It can also be added to grain products during the enrichment process. However, this type of iron (nonheme iron) is not efficiently absorbed by the body. Fortunately, there are a few measures that can be taken to improve iron absorption. Consuming both heme iron and nonheme iron foods, consuming more foods rich in vitamin C, and keeping the fiber intake within the current recommendations are a few examples.
Iron plays several important roles in the human body. It forms important compounds in red blood cells and in muscle cells. It is also used as part of some enzymes and proteins. The brain and the immune system require this mineral to function properly. However, most iron in the body is found in hemoglobin, a compound in red blood cells that is responsible for oxygen transportation. Severe iron deficiency reduces the amount of hemoglobin in the blood, decreasing its oxygen carrying capacity, a condition known as anemia. Women in their childbearing years are at increased risk for developing iron-deficiency anemia because of the regular blood losses during the menstrual period. At increased risk are also total vegetarians (vegans) because of the lack of consumption of heme iron foods.
Iron-deficiency anemia presents the following symptoms: pale skin, fatigue, loss of appetite, apathy, and poor temperature regulation. It is also associated with poor immune function, short attention span, irritability, and poor learning ability. Unfortunately, once the condition is established, the only way to recover is through iron supplementation. However, a physician must be consulted in order to determine the possible cause (such as inadequate intake or an unknown blood loss) and to prescribe the proper dosage. Iron supplementation should not be taken without medical advice, because high doses of iron can quickly build up in the body and lead to toxic symptoms.
The 2010 Dietary Guidelines for Americans recommends the consumption of heme iron rich foods as well as other nutrients that enhance iron absorption in order to prevent iron deficiency.
References
Benardot, D. Advanced Sports Nutrition. Champaign, IL: Human Kinetics. 2006.
Berning, J. and Steen, S. Nutrition for Sport & Exercise. Sudbury, MA: Jones and Bartlett Publishers. 2006.
United States. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2010. Washington, DC: U.S. Government Printing Office. 2010.
Wardlaw, G. and Smith, A. Contemporary Nutrition. New York: McGraw-Hill. 2009.
[1] Trace minerals are inorganic substances needed by the body in very small doses (100 milligrams or less). Examples are iron, zinc, selenium, and iodide, among others.