Iron is a trace element, meaning it is present in the body in extremely small amounts. However, it plays a critical role in human metabolism. Iron forms the oxygen transporting compounds in blood (hemoglobin) and in muscle (myoglobin). Iron absorption by the body is determined by the amount already stored relative to a constant level. In other words, the lower the stored levels of iron (called serum ferritin), the more room there is for iron absorption. Marginal iron intake creates a risk for low iron stores, which in turn can lead to iron deficiency anemia and poor oxygen carrying, diminished energy and poor athletic performance. When excess iron is absorbed (called hemochromatosis), the risk of liver or heart damage arises. Therefore iron intake is about keeping a balance.

Because iron deficiency is a buzz word in the athletic community, many athletes lean towards iron supplementation if they experience poor performance. However, iron deficiency is only one of the many causes of poor athletic performance or low energy levels in athletes. Iron supplementation is not recommended if iron levels stores are in fact normal because of vastly individual absorption rates. Before blaming iron as the low performance culprit, the metabolism of iron, the stages of low iron stores and iron deficiency anemia must be understood.

Stages of Depletion

Iron depletion occurs in stages. Initial iron depletion is difficult to detect because even though iron stores may deplete, hemoglobin itself is still in normal ranges. This is called iron deficiency without anemia. Even at this stage, athletic performance will suffer. Anemia is the final stage of iron depletion diagnosed when the hemoglobin concentration itself is low. A blood test is the only sure way to diagnose anemia. Clinical symptoms and performance capacity can vary between individuals at each stage of the iron depletion. Typically, a low iron level which result in the degradation of blood gas transport, negatively affects aerobic capacity, endurance, and overall exercise performance. Chronic fatigue, high exercise heart rate, low power, frequent injury, recurring illness, loss of interest in exercise, lethargy, sleepiness, apathy, poor concentration and irritability are symptomatic. Secondary symptoms also include poor appetite and diminished immunity. Since many of these symptoms are also common to over-training, a blood test should always be performed for proper diagnosis.

Athletes and Iron depletion

Athletes are generally at an increased risk for iron depletion because iron lost thorough sweat can amount to 0.3 – 0.4 mg per liter. Adolescents and vegetarian athletes are particularly at risk because meeting iron requirements by diet for them is a challenge - adolescents, because of their growth state and increased requirements, and vegetarians because iron from plant sources is not as bioavailable as iron from animal sources. Animal iron, or heme iron, provides most of the iron absorbed through diet. Females, through menstrual blood loss, are also more susceptible to lower iron stores than males. Other factors particular to athletes that increase iron depletion include increase in gastrointestinal blood loss after running, hematuria (presence of hemoglobin or myoglobin in the urine), which results from the red blood cell rupture caused by the foot striking the ground or by mechanical stress in the muscle.

Routine iron screening is essential for athletes, particularly those that are overly concerned with weight management for their sport. Iron levels are individualized and regular blood work will protect against actual iron deficiency and misinterpreting a single blood test as sports anemia (blood hemodilution). Sports anemia refers to a condition often found in endurance athletes when low hemoglobin levels are evident but normal levels of other iron status indicators are normal and often occurs when intensity of training rapidly increases after a rest period. It is not a true anemia. The hemoglobin concentration is low due to a blood volume increase, a common and positive phenomenon as training increases. To minimize the false reading of sports anemia, blood tests should preferably be done prior to the start of the sports season to establish individual baselines.

Once blood tests detect low iron stores, dedication and careful meal planning are necessary to ensure one’s diets includes foods rich in iron, especially the more absorbable heme iron from animal sources. Furthermore, foods that aid in iron absorption should be included with foods rich in iron and foods that block iron absorption should be excluded. Vitamin C improves iron absorption. Calcium, caffeine, tannins (acidic, astringent substance found in tea, wine and some vegetables), phytates and oxalates (chemical compounds found in grains, bran and leafy green vegetables) impair iron absorption.

Care must be taken to not eliminate iron sources when either modifying diet or traveling to places that require dietary modification. Athletes traveling abroad for periods of time may be more susceptible to iron deficiency if they make radical changes to their regular diet. For example; in certain areas of the world animal protein sources may be less available.

The decision to initiate iron supplementation should not be made unless a blood test dictates a need. Athletes with normal iron status, as indicated by either serum ferritin or hemoglobin should not take iron supplements. The presence of anemia (due to iron deficiency) does call for supplementation. The specific supplementation regime should be tailored to the individual athlete. Dietary Reference Intakes (DRI) suggests a requirement of 8 mg/day of iron for men, and 18 mg/day for females. Endurance athletes may need slightly more.

Supplements

Iron tablets are available in various forms, ferrous sulfate being the most common. Other forms used include Fumarate and Gluconate. Because of concerns surrounding daily supplementation (i.e. toxicity, non-compliance) the International Nutritional Anemia Consultatitive Group investigated the efficacy of different supplement protocols. Their conclusion is that daily treatment is more effective for restoring the deficiency. They suggest a 60 mg/day for adolescents and adults (plus 400 ug/day of folic acid for women of childbearing age). The iron in a multivitamin supplement is not as well absorbed as administering the iron alone, particularly if calcium is part of the preparation or if it is consumed with tea, coffee or a meal. Replenishment of iron stores is a slow process and could take upwards of two months. One suggested course of supplementation is 100 mg of iron per day in the ferrous form, 10-20% of which is absorbed by the intestine, for 20 consecutive days per month. Side effects of supplementing iron may include increased gastrointestinal distress and constipation.

Food sources

Rich sources of heme iron include beef, organ meats, clams, oysters and dark poultry meat. Rich sources of non heme iron (plant based) , not as well absorbed as animal sources, include legumes, dried fruits, baked potatoes, beets, spinach and broccoli. Whole grain items contain the most iron of any food in the grain product group. Fortified or iron enriched foods are even better. Cereal is often labeled as being enriched. Unfortunately, most non heme iron comes from foods that also contain fiber, phytates and oxalates which inhibit absorption. As previously mentioned, vitamin C is known to enhance the absorption of iron; therefore, it should be consumed along with sources of iron, particularly low absorbable non-heme iron. Another way to obtain iron in the diet is through the use of cast-iron skillets in cooking. Iron can actually leech into foods left to simmer in such cookware.

Summary

Iron plays a critical role in aerobic capacity and performance because of its role as an oxygen transporter to working muscles. Less than adequate iron results in less oxygen delivered to muscles, resulting in maximal oxygen consumption deterioration and less that optimal performance. Athletes have a higher rate of iron deficiency than non-athletes because of iron loss through sweat, urine, and in the gastrointestinal tract, and female athletes are particularly at risk for deficiency due to menstruation. Depleted iron stores result in iron deficiency which develops and progresses through stages: depleted iron stores (functional iron remains normal); early functional iron deficiency without anemia; and iron-deficiency anemia. Hemoglobin appears normal in early stages so the condition often goes undetected or is dismissed as inconsequential. Low iron stores, even without anemia, can be detrimental to athletic performance. Due to possible liver and heart damage risks with excess iron, supplementation is not warranted unless blood work is analyzed and the possibilities of a misdiagnosis such as sports anemia as well as over-training are ruled out.

References:

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