A trip to your physician for a complete evaluation may reveal that you are suffering from iron-deficiency anemia, a condition characterized by a reduced oxygen-carrying capacity of the blood. Iron deficiency is a common nutritional deficiency, especially among active females of childbearing age. Iron is needed by your body to form hemoglobin and myoglobin, essential oxygen-carrying proteins in the blood and muscles, respectively. It is also needed to make enzymes that play a role in energy production. If your body is using more iron than what it is taking in, red blood cell formation and hemoglobin production are impaired.
Low iron levels reduce the oxygen carrying capacity of your blood. If there is not enough oxygen transported to your muscles, fatigue sets in, reducing your endurance capacity during exercise and leading to a general feeling of tiredness throughout the day. Low iron levels can also effect the functioning of your brain, which relies on an adequate supply of oxygen, causing such symptoms as irritability, poor concentration, decreased attention span, and impaired learning. Other symptoms of iron deficiency include a sensitivity to cold, weakness, and impaired immune function.
Who is at Risk?
What is the Recommended Daily Intake?
- Females, particularly active/athletic women of childbearing age, due to iron loss through menstruation.
- Pregnant women who need more iron due to the increased blood volume associated with pregnancy.
- Active individuals/athletes, especially those engaging in endurance exercises. The need for iron in these individuals is increased by approximately 70%. Iron is lost through sweat, therefore heavy sweating could contribute to lower iron levels. Runners can also experience what is called "heel strike" hemolysis in which the red blood cells are damaged as the feet make contact with the ground, thus effecting iron status.
- Children experiencing growth "spurts" which involve quick increases in blood volume and red blood cell formation.
- Vegetarians/vegans because iron consumed from plant-based sources is not as readily absorbed by the body as it is from animal sources.
- Those who consume a diet that is deficient in iron.
- Regular blood donors
Best Food Sources of Iron
- Women ages 19-50 years - 18 mg/day
- Women ages 51+ - 8 mg/day
- Pregnant women - 27 mg/day
- Men ages 19-50+ years - 8 mg/day
Other Food Sources of Iron
- Lean red meat
Factors Effecting Iron Absorption
- Iron-fortified cereals
- Dark-green leafy vegetables (e.g., spinach)
- Blackstrap molasses
- Dried fruit (e.g., raisins)
- Iron found in animal sources is better absorbed by the body because it is in the heme form (myoglobin and hemoglobin, like in our bodies) and, therefore, treated like a protein.
- Iron found in plant sources is in the nonheme form which has to be released by digestive enzymes from the plant structures. Various factors decrease its absorption.
- Consuming Vitamin C (approximately 25-75 mg of Vitamin C) can enhance your body's absorption of iron.
- Cooking foods in a cast iron skillet increases absorbable iron, especially when cooking acidic foods such as tomatoes.
- Caffeine, calcium, zinc, tannins (in tea), polyphenols, and phytates can interfere with the body's ability to absorb iron.
Reversing iron-deficiency anemia can take 3-6 months and may require taking iron supplements. However, you should consult your physician before taking iron supplements because iron toxicity can result.
Under normal circumstances, very little iron is lost from the body and so taking an excess can lead to an accumulation in your body's tissues and organs. Abnormally high levels of iron are associated with an increased risk for Parkinsons' disease, cancer, and heart disease. Excessively high levels of iron can also cause congestive heart failure and irreversible liver damage.
If you suspect that you may have iron-deficiency anemia schedule an appointment with your physician. There may be causes of the anemia, other than dietary intake, that need medical attention.
Vegetarian Sports Nutrition - food choices and eating plans for fitness and performance, 2007; Larson-Meyer, D.E.
The Coaches Guide to Sports Nutrition, 2007; Benardot, D. and Thompson, W.R.
Office of Dietary Supplements of the National Institutes of Health, "Dietary Supplement Fact Sheet - Iron."
ACSM's Health & Fitness Journal, Vol. 9/Issue 2, "Avoiding Exercise-Related Fatigue," pp. 30-32, Rush, S.