It is easy for an athlete's iron stores to become depleted. And it is easy for their performance to suffer as a result.
By Michelle Rockwell & Dr. Pamela Hinton
Michelle Rockwell, MS, RD, is the former Coordinator of Sports Nutrition for the University of Florida Athletics Association and currently serves as a consultant for athletes and teams nationwide. Based in Durham, N.C., she can be reached at: firstname.lastname@example.org.
Pamela Hinton, PhD, is an Assistant Professor of Dietetics at the University of Missouri, specializing in sports nutrition, iron deficiency, and the female athlete triad. She can be reached at: HintonP@missouri.edu.
Lisa is a freshman college soccer player. Before arriving on campus, she spent the summer playing for her club team. She wanted to report to her new team as fit as possible, so she also got up early every morning to run stadiums and sprints, went to the gym several evenings each week to lift weights, and played pick-up games every chance she got. She worked hard on improving her diet by choosing healthier snacks and cutting down on her favorite foodschicken wings and fast food burgers. Her high school coach says Lisa is the hardest working athlete he has ever coached.
But two weeks into preseason college workouts, she begins dropping toward the back of the pack during team runs. She struggles to make her time goals in conditioning sessions. She has twice slept through her alarm clock and missed morning workouts. She doesn't focus well in film sessions. Her roommate says she's moody. Her new coaches think she can't cut it at the college level. Her parents wonder if she's just homesick.
Lisa is referred to a physician who suspects mononucleosis or another virus. She works with a sports psychologist. She completes extra cardio workouts. Eventually, the real culprit is discoverediron deficiency anemia. The athlete had drained her iron stores by training hard all summer, had lowered her intake of dietary iron (by limiting burgers and chicken wings, which are both high in iron), and had begun having heavier menstrual periods as her body matured (and thus, more blood loss). Lisa starts taking iron supplements and working with a sports dietitian on dietary iron strategies. Six weeks later, she is in the starting line-up and back to her old self.
Because iron deficiency is so common among athletes, particularly female athletes, it is critical that sports medicine staff members and coaches know the facts about iron and performance. Below is practical information on iron deficiency designed to help you detect and treat iron deficiency in your athletes.
HOW IT WORKS
Iron plays a critical role in carrying oxygen from athletes' lungs to their working muscles, allowing aerobic metabolism to take place. When an athlete is operating without adequate iron, less oxygen is delivered to muscles, maximal oxygen consumption (VO2max) drops, and performance suffers.
Athletes have a higher rate of iron deficiency than non-athletes because their bodies lose iron through sweat, urine, and in the gastrointestinal tract (for example, it's not uncommon for runners to have blood in their stool following races). They often turn over more iron due to utilizing more oxygen. Footstrike hemolysis, the breakdown of red blood cells due to the impact of an athlete's foot striking the ground, can also contribute to a slight decrease in hemoglobin for athletes in many sports. And because they also lose iron through menstruation, female athletes are particularly at risk for deficiency.
When an athlete is not getting enough iron to maintain his or her iron stores, iron deficiency will develop and progress through three stages: depleted iron stores (but functional iron is unchanged); early functional iron deficiency without anemia; and iron-deficiency anemia. In the first two stages, hemoglobin appears normal, so the condition often goes undetected or is dismissed as inconsequential in the absence of anemia. However, it's critical to understand that low iron stores, even without anemia, can be detrimental to athletic performance.
By the time an athlete's condition reaches early functional iron deficiency, he or she will begin experiencing reduced endurance capacity and loss of energy. Animal studies have shown that symptoms show up at this stage because iron-containing oxidative enzymes and cytochromes have already become less active.
The hallmark symptom of iron deficiency anemia is fatigue that worsens with exertion. Since fatigue is a common complaint of athletes and can have many different causes (such as other nutritional imbalances, illness, stress, or mental health concerns), the exertional component of iron deficiency fatigue is the key indicator. Look for fatigue that worsens with exercise. If an athlete complains of fatigue throughout the day, but feels fine during workouts, the cause is likely not exclusively iron deficiency.
Other symptoms of iron deficiency include:
- Breathlessness or feeling abnormally winded during workouts.
- Decreased performance, especially a sudden decrease.
- Lethargy, sleepiness, and apathy.
- Poor concentration.
- Moodiness or irritability.
- Increased injury susceptibility.
- Always feeling cold, and unable to tolerate cold tank or ice treatments.
WHO IS AT RISK?
Anemia is often perceived as a problem that only female endurance athletes need to worry about, but recent research has shown that iron deficiency can occur in athletes in any sport at any level, male or female. One recent study found that 25 to 35 percent of adolescent and adult females competing in a variety of sports were iron deficient. The same study found that 11 percent of males competing in a variety of sports were iron deficient, and males competing in certain sports appear to be more at risk: Fifteen percent of male basketball players and 36 percent of elite male gymnasts in the study were iron deficient.
At the University of Florida, we saw a significant number of cases of iron deficiency anemia in football and soccer players and in gymnastics athletes. Don't assume that any athlete is immune to iron problemswe have observed iron depletion in baseball, softball, and golf, all sports with a minimal endurance component. While any athlete can develop problems with iron, certain athletes do fall into high-risk categories:
- Female athletes, primarily because they lose iron through menstruation. Heavy or irregular periods may contribute to iron deficiency. Additionally, because female athletes typically consume fewer calories overall than male athletes do, they are less likely to consume adequate iron.
- Dieters or athletes restricting caloric intake. When overall food intake decreases, getting adequate iron is unlikely unless the athlete is specifically focusing on eating high-iron foods.
- Vegetarian athletes. Plant sources of dietary iron are not as dense or well absorbed as meat sources
- Athletes initiating a new or significantly more intense training program. Rapid depletion of iron stores can occur with the onset of harder training, particularly if levels were borderline before the athlete intensified his or her program.
- Athletes who frequently donate blood. Blood donation results in a loss of 200-250 mg of iron per 0.5 L of blood.
THE IRON-ADEQUATE DIET
The FDA recommends that women 18 to 50 years of age get 18 mg of iron per day. The RDA for men is eight mg per day. However, because of their high iron turnover, we recommend that all endurance or intensely trained athletes, both male and female, aim for 18 mg a day. The best way to help athletes protect their crucial iron stores is by helping them choose a diet that supplies adequate iron from a variety of sources.
More and more non-meat iron-fortified products have become available recently, ranging from cereals to sports bars to breads (e.g., Wonder Ironkids bread). These products may be a beneficial strategy for boosting iron intake, but they shouldn't be the sole source. Athletes who eat meat should focus on getting iron from animal sources, since the iron in animal products (which contains hemoglobin) is absorbed better than iron from plant sources (called non-heme iron), which contains no hemoglobin. Consuming three to four small servings of beef per week is effective in increasing iron stores for many athletes.
Vegetarian athletes can also meet their iron needs through diet, but it takes significant effort and planning. Some nutritionists feel that vegetarian athletes should aim for an iron intake as high as 24 mg per day since their iron sources are not as bioavailable (readily absorbed). It may be helpful to explain to vegetarian athletes why they need to pay particular attention to their iron intake by using the following example: A one-cup serving of raw spinach contains six mg of iron, but only 0.1 to 0.6 mg of that is absorbed in the small intestine. In contrast, a three-ounce serving of steak contains less irononly four mgbut 50 percent of that is absorbed in the intestine, for an actual iron intake of two mg.
It's also important to note that there are many athletes who do not necessarily label themselves "vegetarian" but who do follow a diet extremely low in meat products, such as athletes following a very high carbohydrate diet, on a limited budget, or with limited cooking skills (think dorm room macaroni and cheese). These athletes also need to be particularly careful to get adequate dietary iron.
In addition to consuming more iron, both vegetarian and meat-eating athletes can take steps to enhance the iron their bodies absorb from non-heme sources. One of the best ways to accomplish this is by combining non-heme iron sources with foods high in vitamin C. Easy examples include:
- Iron-fortified cereal with a grapefruit.
- Spinach salad with strawberries.
- Chili with lentil beans and tomatoes.
- Iron-fortified bread with real fruit preserves.
- Noodles with marinara sauce.
- Nuts with dried apricots.
- Bagel and orange juice.
Preparing non-heme iron foods in cast iron cookware can significantly increase iron content. For example, using a griddle made of cast iron will add extra iron to foods like pancakes, French toast, scrambled eggs, and stir fry.
It's also important to help athletes avoid nutritional practices that decrease the absorption of iron. For example, drinking tea or coffee with iron-rich foods may impair absorption. Similarly, the phytates present in some grains and vegetables can reduce iron absorption. It is also recommended that iron supplements be taken at a separate time from calcium supplements and even calcium-containing foods because calcium can inhibit iron absorption. Athletes may be advised to not select calcium-fortified orange juice if their intent is to use the juice to enhance iron absorption.
As an added dietary insurance policy, many sports nutritionists recommend a multivitamin that contains iron. Look for a multivitamin from a reputable company that contains approximately 50 percent of the iron Daily Value (9 mg) for men and 100 percent of the iron Daily Value (18 mg) for women. Examples of these include Theragran-M or Centrum for males and One-a-Day Women for females.
However, caution your athletes not to become too dependent on supplements for achieving their iron needs. Remind them that even though their supplement contains a high percentage of iron and is an excellent back-up, not all of the iron is well-absorbed, so they still need to focus on dietary sources. (For a listing of the iron content of common foods, see "Adding Up Iron".)
If you are working with an athlete who has symptoms consistent with iron deficiency, they should be referred for blood work and further evaluation. Many insurance companies will pay at least a portion of lab expenses for iron analysis when symptoms are present.
Blood tests for iron depletion most commonly measure serum ferritin. Ferritin is a measure of hepatic (liver) iron stores. Depleted ferritin can be associated with decreased performance. The cut-off for what is considered "low" varies. Some consider values less than 15 ug/L inadequate. Many sports medicine professionals aim for a higher range with athletes because iron stores are so critical to health and performance and can be depleted fairly rapidly through rigorous training. At the University of Florida, we considered less than 40 ug/L low for females and less than 70 ug/L low for endurance sport males.
It is worth mentioning that ferritin is an acute-phase protein that can be elevated in response to inflammation, hard exercise in an untrained person, or illness. Thus, if a ferritin test comes back high in the presence of these circumstances, it should be re-evaluated after one week.
Athletes whose iron deficiency has progressed to iron deficiency anemia may also have blood tests that show hemoglobin and hematocrit below the normal range. Hemoglobin is the protein in red blood cells that carries oxygen from the lungs throughout the body. Iron is a critical structural component of hemoglobin and when iron is inadequate, hemoglobin can become diminished. Hematocrit reflects the actual percentage of red blood cells in the blood. When hematocrit is low, aerobic function is likely diminished.
Normal ranges vary by lab, but a hemoglobin level of 12.0-14.8 g/dl for females and 13.7-16.5 g/dl for males and a hematocrit level of 37-43 percent for females and 40-48 percent for males can be used as good reference points. However, there appears to be an individualized component to hemoglobin concentration. In other words, an athlete may have hemoglobin in the standard normal range, but still be low relative to his or her own normal level. This is known as relative anemia, and it can significantly impact exercise tolerance and should be treated. Thus, it's valuable to compare hemoglobin and hematocrit over time as a drop in these (even if still in the normal range) may have negative effects.
Also be aware that a condition called sports anemia can cloud the iron deficiency anemia diagnosis in athletes. Endurance training increases the volume of plasma an athlete has. When plasma volume increases, it dilutes red blood cells and can make hemoglobin and hematocrit appear falsely low. Blood work should be done prior to the start of the season or a few weeks into training to minimize alterations caused by sports anemia.
Anemia is not always caused by iron deficiency. This is why exclusively testing hemoglobin and hematocrit is not enough to clarify the origin of anemia. If true iron deficiency exists, MCV (a measure of the size of the blood cell) will likely be low because iron deficiency causes a reduction in cell size and because ferritin levels are also low. Some physicians use a full iron panel to diagnose iron deficiency anemia, including tests such as total iron, iron binding capacity, and percent saturation.
While blood analysis is certainly a very valuable tool in uncovering the presence and measuring the severity of iron deficiency, it is not always possible. If you are in a situation where testing is not an option, there are many non-invasive tools effective in assessing iron habits and iron deficiency risk. Consider giving athletes a questionnaire that asks about typical diet, current supplementation, menstrual history, training status, and history of iron deficiency.
If you feel that an athletes' symptoms and habits point to iron deficiency, but no bloodwork is available to back up your suspicions, you can still take action. The conservative, but appropriate, step would be to supplement with an iron-containing multivitamin and ensure that dietary iron is greater than 20 mg per day.
When an athlete does have blood work showing that he or she is suffering from iron depletion or iron deficiency anemia, supplemental iron is usually needed. However, because of the risk of iron overload, supplemental iron should only be given under a physician's care and with warranting blood work. Excess iron can alter the metabolism of other important nutrients. Additionally, some individuals (primarily males) have a particular susceptibility to iron overload (called hemochromatosis). These people absorb iron at an extreme rate and the excess iron can pool in organs and tissues. And unlike most other minerals, iron cannot be actively excreted from the body, so the potential for toxicity is high.
An athlete who is prescribed supplemental iron will need to choose between a variety of available forms. Most athletes with iron deficiency can tolerate ferrous sulfate, the most common form of iron supplements. One tablet per day (containing 35-60 mg of elemental iron) should be used with iron depletion and two tablets per day (one in the morning and one at night) with iron deficiency anemia.
Some athletes experience gastrointestinal upset with supplements. Nausea, cramping, constipation, dark stool, and diarrhea are typical complaints. To minimize these side effects, have the athlete start by taking one tablet per day and build up to two. He or she should take the iron with food (preferably food low in phytates and calcium but containing Vitamin C) and take it right before bed.
For athletes who cannot tolerate ferrous sulfate, time-released iron supplements or supplements containing small amounts of laxative or Vitamin C may be useful. Liquid iron supplements are a popular choice, especially among runners. They can be mixed in orange juice, which enforces Vitamin C consumption. Athletes should be advised to brush their teeth after taking liquid iron supplements since the iron can stain teeth.
Once an athlete begins treatment, hematocrit and hemoglobin will respond to the supplemental iron after about two weeks. It may take up to 12 months to fully replete iron stores. The athlete should be re-tested in three months. If improvements have not been made in lab values and symptoms by this point, a further medical and nutritional evaluation is warranted.
Another way of protecting your athletes against iron deficiency is to set up a standard testing protocol within your athletic department. Routine screening, especially of athletes at risk for iron deficiency, is tremendously beneficial since waiting until symptoms become significant enough to detect can be very costly in terms of performance. The longer the deficiency exists, the more severe the symptoms, and the longer the wait to return to optimal performance.
The cost of iron screening is not nearly as prohibitive as many think. A complete blood count (CBC), which includes hemoglobin and hematocrit, generally costs between $30 and $35. Ferritin evaluation costs $20 to $25 per test. Some labs offer discount prices for teams and groups of athletes. It's easy to argue that this nominal price is well worth it.
Many college programs already screen female endurance athletes, but we believe there is evidence to support broadening this to include all female athletes and male endurance athletes. At Florida, we expanded our screening to include all three groups, and the number of deficiencies we uncovered was significant. Many sports medicine staff members, coaches, and athletes felt that the attention we paid to our athletes' iron status was a very important factor in their success both on the field and in the classroom.
Sidebar: SAMPLE MEAL PLAN
An iron-rich diet that combines plant and animal sources is the best way for athletes to maintain iron stores. The following menu contains iron-rich foods that are easy to prepare, even in a dorm room.
Bagel with margarine and strawberry jelly (2 mg)
2 hard boiled eggs, prepared in microwave (2 mg)
Orange juice (Vitamin C)
Canned soup containing meat and/or beans (4 mg)
Grilled cheese sandwich on wheat bread (1 mg)
Fruit yogurt (Vitamin C) or pudding
Trail mix: nuts, dried fruit, chocolate if desired (2 mg)
Canned meat and/or bean chili (5 mg, Vitamin C)
French bread (1 mg)
Carrots and dip
Sliced roast beef or pre-cooked chicken tenderloins (3 mg)
Spinach salad with assorted veggies and vinaigrette dressing (5 mg)
Blueberry muffin (1 mg)
Grapefruit juice (Vitamin C)
Sidebar: VEGETARIAN MEAL PLAN
Vegetarian athletes need to pay particular attention to iron intake because iron from plant sources is more difficult for the body to absorb. The following is an example of a 2,500-calorie vegetarian meal plan containing 25 mg of iron.
1 cup iron-fortified cereal (5 mg)
1 cup skim milk or soy milk
12 oz orange juice (Vitamin C)
Spinach salad with 1/4 cup sunflower seeds and Italian dressing (7 mg)
Veggie burger with cheese (or soy cheese) on wheat bun (3 mg)
1 fruit yogurt (Vitamin C)
2 oatmeal raisin cookies (3 mg)
Tofu/broccoli stir-fry or 2 slices cheese pizza (6 mg)
1 cup rice (1 mg)
1 cup ice cream
Table: ADDING UP IRON
General dietary guidelines recommend that women 18 to 50 years of age get 18 mg of iron per day, while men get eight mg per day. However, we recommend that all endurance or intensely trained athletes, both male and female, get 18 mg a day. Vegetarian athletes and those who eat very little meat should aim for 24 mg per day.
|Food||Serving Size||Iron per Serving (mg)|
Beans or Lentils
Bean Soup or Chili w/Beans
Nuts or Seeds
Waffles or Pancakes
1 cup cooked
1 cup, raw
5 (varies by brand and type)