One of the most recognized and important minerals, especially for athletes and physically active people, is iron. This mineral plays several key roles in bodily functions, and its absence in the diet can have dire consequences. It is found in food in structures classified as heme and non-heme iron. Heme iron is found exclusively in animal food. Whereas, non-heme iron is found in both animal and plant sources. Heme iron is absorbed more efficiently.
Functions in the Body
Depending upon size, gender, diet and menstrual status, the average adult has about 2 to 5g of iron in the body at any given time. Roughly 2/3 of total iron in the body is found in hemoglobin, the oxygen-carrying molecule in the blood. Myoglobin, which serves as an oxygen reserve in muscles, accounts for 10 percent of the iron in the body. It enhances the rate of oxygen transfer from the capillaries into the muscle cells. Iron is a crucial component of exercise because it is a component of hemoglobin and myoglobin, which are both involved in aerobic energy metabolism.
Sources and Intake
Iron can be found naturally in different meats, fruits, grains and vegetables. Good choices for meat provisions include lean cuts of beef, dark meat of skinless chicken or turkey, pork and lamb. In milligrams, liver provides the highest source of iron, with 7 1/2mg in a 3-oz. serving. Fruit sources include prune juice, prunes, raisins and plums. Spinach, lima beans, black-eyed peas and asparagus are natural vegetable sources of iron. Whole grains, like some cereals, are good sources if it indicates that they are "fortified" or "iron-enriched." Daily intake is recommended at 8mg for men and 18mg for women through menopause. Post-menopause requirements drop to 8mg.
Imbalance and Deficiency
The point where hemoglobin is unable to meet the body's demand for oxygen is known as anemia. This condition is precipitated by the depletion of iron. Anemia is generally associated with hemoglobin levels less than 7g per 100ml of blood. Normal levels in men are greater than or equal to 14mg per 100ml, while women are normal at greater than or equal to 12mg per 100ml of blood. A person with anemia is easily fatigued and intolerant of cold. These symptoms are accompanied by a pale complexion due to low presence of red-colored hemoglobin in blood vessels.
Supplementation
It is recommended for those diagnosed with iron-deficiency anemia to incorporate supplementation. The typical supplements, ferrous sulfate or ferrous gluconate, need to be taken for approximately 4 months to resolve the deficiency. Supplements should be taken in conjunction with vitamin C, or in the presence of meat, fish or poultry. These items appear to enhance the absorption of iron. Care should be taken to avoid iron overload, however. Toxic levels of iron can lead to distress in many organs, particularly the liver.
Special Population
Many active or athletic females practice vegetarianism in their efforts to lose weight. Besides the deprivation of iron-rich sources found in animal protein, they also predispose themselves to a condition known as amenorrhea--the loss of menstrual periods. These individuals increase their risks of stress fractures four and a half times of those who have normal menstrual periods. This condition can be reversed and normal cycles resumed with the incorporation of a well-balanced diet, including sources that provide sufficient amounts of iron.
References
- Nancy Clark's Sport Nutrition Guidebook, 3rd ed. Clark, Nancy. 2003
- Sports and Fitness Nutrition. Wildman, Robert and Miller, Bary. 2004
- Principles of Anatomy and Physiology. Tortora, Gerard and Derrickson, Bryan. 2009
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