Fatigue during training is inevitable, but fatigue caused by iron deficiency anemia can be avoided and prevented. Iron, a trace mineral, is a major component of hemoglobin in red blood cells and is responsible for transporting oxygen to the lungs and various muscles during endurance exercise. When we are iron-deficient we may experience early-onset fatigue during a run, muscle burning, shortness of breath, nausea, frequent infections, pale appearance, light-headedness, or feelings of having heavy legs. Over 50% of female endurance athletes suffer from iron-deficiency anemia. However, male endurance athletes are not immune to anemia. Alan Culpepper, a top US marathoner, battled anemia in the summer of 2006. He struggled to train and compete until he was able to start supplementing with iron to improve his iron stores.
The iron needs of endurance athletes are greater than for non-athletes due to the iron losses that occur with each footstrike, and the loss in sweat. These needs are even greater for female runners because of menses. In addition, dietary intake of iron can be a limiting factor as well. Seventy-five percent of women aged 18 to 44 don’t eat enough iron-rich foods to meet their daily needs, so iron depletion is inevitable. And it doesn’t help that we absorb about 15% of the iron we ingest. The recommended daily allowance (RDA) for iron for women (11-50 years of age) is 15mg day and 10mg per day for men. During pregnancy iron needs increase to 30mg per day. Even though we know that endurance runners need more iron, there aren’t special iron recommendations for endurance athletes.
It is also very possible to have normal hemoglobin levels and have low iron stores (serum ferritin). Hemoglobin is the protein molecule attached to the red blood cell and is responsible for transporting oxygen to the various muscles and the lungs whereas serum ferritin is the storage form of iron in the body. Normal hemoglobin levels are between 11.5 -15.5g/dl and less than 11.5g/dl is considered anemia. Normal serum ferritin levels can range from 20ug/dl to 150ug/dl, yet some studies suggest that serum ferritin levels less than 30ug/dl to be iron depletion and 12ug/dl suggests exhaustion of iron stores. Athletes may feel tired and weak with low iron stores even though they are not anemic. The cut off levels for serum ferritin are very individual and may differ in athletes, so interpretation of low SF levels needs to be cautious. Anecdotal evidence suggests that serum ferritin levels around 50ug/dl or greater are preferred.
It has become standard practice in recent years to monitor an athlete's iron status by testing serum ferritin levels. However, there is no standardized ferritin level at which supplementation is recommended, nor is there a consensus as to the appropriate maintenance of ferritin. For example, an athlete experiencing symptoms of fatigue and has a serum ferritin level of 25ug/dl may be a candidate for iron supplementation and/or education regarding the importance of a balanced diet to maximize performance. Supplementation for the iron-depleted nonanemic athlete does not appear to be justified to solely improve performance. In fact, several studies show that supplementation with iron does not improve performance of iron-depleted nonanemic athletes. However, it is well-known that performance is diminished with anemia and is improved when the anemia is reversed.
The most prudent first step is to evaluate the athlete’s diet. It is possible that making a few dietary changes can improve iron stores. A diet rich in meats, beans and cereals combined with vitamin c rich foods can improve iron stores. Vitamin c increases the bioavailability of iron in the body. It is well established that the iron in animal sources, otherwise known as heme iron is better absorbed than iron from plant sources or non-heme iron. So meats are excellent sources of iron. A 3 oz portion of beef (visualize deck of cards) contains about 3 mg of iron. A cup of cereal can contain as much as 8 mg of iron, however, is not as well absorbed by the body. So eating iron-rich foods with vitamin c rich foods such as tomatoes, citrus fruits, strawberries, and broccoli can increase the amount of iron that is absorbed into the bloodstream. Cooking in a cast-iron skillet leaches iron into food.
Also note that the absorption of iron is inhibited by tannins found in tea and coffee, food additives such as phosphates found in soft drinks and certain preservatives. It is also decreased with excessive intake of certain minerals such as zinc and calcium
When a concerted effort has been made to increase dietary intake of iron and fatigue and low levels of serum ferritin and /or hemoglobin still persist, iron supplementation may be necessary until normal levels are achieved. Ferrous sulfate is the preferred form of iron since it has a high absorption rate. A typical dose of 50 to 100mg of elemental iron, 2 or 3 times a day taken with 500mg of vitamin c or with some orange juice will help absorption. Since high levels of iron can cause constipation or diarrhea, a liquid iron supplement may be preferable. Usually iron levels are restored within 60 days of therapeutic doses of supplemental iron.
Examples of food sources of iron:
· Lean cuts of beef, pork, lamb
· Liver
· Skinless turkey, and chicken
· Fish
· Iron-enriched cereals, breads, and pastas
· Green leafy vegetables
· Beans and dried peas
· Eggs (the yolk)
These foods eaten with vitamin c rich foods will aid in absorption. Listed below are examples with food rich in vitamin c:
- Citrus fruits (oranges, grapefruits)
- Strawberries
- Broccoli
- Juices fortified with vitamin c
- Bell peppers
- Tomatoes
It is important to continually monitor iron status as well as biochemical markers and nutritional status to ensure that iron deficiency anemia is prevented to assure optimal health and athletic performance.
