The element of fitness success: iron deficiency may be sapping your energy and hurting your performance. Here's how to turn the tables

Muscle & Fitness/Hers, April, 2003 by Bob Lefavi

feeling a bit fatigued lately? Maybe it's that low-carb diet, or the fact that you've stepped up your exercise. Perhaps you're simply not getting enough sleep. These are the obvious reasons for feeling tired or run-down, but for many female athletes, they aren't the only ones.

Women who exercise regularly are especially prone to a potentially insidious disease that masks itself as plain old everyday fatigue--iron deficiency anemia. Unfortunately, it can be difficult to diagnose, and once it gets rolling, it can play havoc with your physical and mental health. Here's what you need to know.

IT'S ALL ABOUT BALANCE

Iron helps red blood cells carry oxygen to working muscles by binding to a substance in the blood called hemoglobin. (Interestingly, iron is what gives blood its reddish color.) Without adequate iron, you can't get enough oxygen to your muscles. That's a problem because oxygen helps produce the majority of your energy.

Remember learning in chemistry how aerobic (literally, "with oxygen") metabolism brings the most adenosine triphosphate, or ATP, for muscular action? Sorry to bring back bad school memories, but the point is that your body needs oxygen for long-term energy. Bottom line: Low iron equals low hemoglobin or anemia, which results in low energy levels and a feeling of fatigue. True anemia is most often brought about by iron deficiency than by any other factor.

Iron stores become depleted when your body loses more iron than it's taking in. This state of negative iron balance ultimately drains your body's stores and symptoms of iron deficiency anemia can set in, including fatigue, malaise (vague feeling of physical discomfort or uneasiness), sensitivity to cold, shortness of breath, dizziness and restless legs syndrome (sensations of pulling, tingling and crawling, accompanied by a need to move the legs).

ARE YOU AT RISK?

Many factors impact your risk of iron deficiency. Here are a few to consider:

1) Being female. A woman's monthly blood loss takes with it about 0.6 mg of iron per day. The growth processes that occur during pregnancy can also stress your blood iron level.

2) Exercise. Regular physical activity tends to deplete iron stores. Although the exact cause is unknown, a number of factors may contribute, including physical stress, hemoconcentration processes (shifting of blood plasma), muscular damage and even nitric oxide. (1,2) Since iron is used in aerobic metabolism, it might not surprise you that studies have shown endurance athletes to have the most problems maintaining adequate iron stores, and even taking a supplement may not help. (3)

3) Low iron intake. According to recent USDA surveys, more than 75% of American women ages 19-50 have iron intakes below 80% of the RDA of 18 mg per day. Studies on the diets of female athletes, who likely need to take in even more than the RDA to compensate for training-induced losses, indicate daily intakes of roughly 12 mg.

Why the iron intake problem? The main reason may be that women generally eat less red meat than men do. "Many female athletes come to me with similar complaints--feelings of weakness, low energy levels and difficulty recovering from their workouts," says Angela Gallo, DTR, CNC, sport nutrition consultant and owner of Total Nutrition Technology in Charlotte, North Carolina. "I can't emphasize enough how critical it is, especially for females, to take in a sufficient amount of iron in their diet."

HOW CAN YOU TELL?

I'm convinced that regardless of exercise status, all women should regularly check their hemoglobin count. It can give you and your doctor a way to detect iron depletion, or at least help establish a baseline for later tests. As a basic guideline, hemoglobin counts that fall below 12 g/dL may be problematic and indicate a need for medical or dietary intervention. Sometimes health-care providers will test for serum ferritin when looking at iron status, but hemoglobin is the better gauge for iron deficiency anemia.

The problem with testing athletes for iron status is that inflammation due to training can affect the results. A new, promising test called serum transferrin receptor is a good way to determine iron deficiency anemia because this test isn't affected by inflammation.

Even so, most recent research suggests that anemia may be more relative than definitive. While normal levels in females range from 12-16 g/dL, don't get too hung up on these numbers. At this level, some women will be iron-deficient and others won't. Further, you might be at 13 g/dL, a supposedly "normal" hemoglobin level, but nevertheless be functionally anemic, meaning you may need more iron than the average woman. That's why it's important to test regularly--any drop could be significant.

To make matters more confusing, athletes, especially endurance athletes, tend to have slightly low hemoglobin levels as judged by general population norms. In fact, endurance athletes commonly have hemoglobin concentrations of 1 g/dL or even 1.5 g/dL below normal. That's because one adaptation of regular exercise is a diluted bloodstream (your blood becomes more "watery"), increasing plasma volume, even though the total amount of red cells in the blood is normal. Your physician needs to be aware of this phenomenon, known as dilutional pseudoanemia or false anemia, and take your training into consideration.