Many women are iron-deficient, but not always for the most obvious reasons. Who's at risk? And how can you make sure you're getting enough iron from your diet or supplements?
Iron-deficiency anemia affects 10%-15% of menstruating women and 7% of postmenopausal women in the United States. The most common form of anemia in women, it develops when iron stores become depleted. Perhaps surprisingly, an iron-poor diet is the least likely cause of iron-deficiency anemia in women in this country. Common causes include blood loss and poor absorption of iron from food.
The life of a red blood cell
Bone marrow, the spongy interior of bone, produces red blood cells (or erythrocytes). These cells make hemoglobin, a molecule made of protein and iron that carries oxygen to tissues throughout the body. Iron gives red blood cells their ability to pick up oxygen in the lungs.
Red blood cells circulate for three to four months in the bloodstream. The liver and spleen then remove them from circulation and extract the iron, storing it in the cells of the liver, spleen, and bone marrow. If iron requirements increase or an excessive blood loss occurs, the body can mobilize iron from its stores.
Anemia develops when we're deficient in healthy red blood cells or have too little hemoglobin. Several conditions can contribute to it. These include blood loss, poor diet, gastrointestinal conditions that inhibit the absorption of nutrients, genetic disorders, chronic illnesses, and damage to the bone marrow from radiation or chemotherapy. All affect the body's ability to maintain enough red blood cells to carry needed oxygen to tissues and organs.
Women of childbearing age lose iron during menstrual bleeding. During pregnancy, a woman's body draws heavily on her iron stores in order to increase her blood volume and supply hemoglobin to the fetus and placenta. Most of the time, these women can be treated with supplements and followed to be sure their iron levels return to normal. Because iron deficiency in premenopausal women is not always due to menstruation or pregnancy, every case should be thoroughly investigated.
Iron-deficiency anemia is less common in postmenopausal women. So when it does occur, it's a red flag, often indicating slow, chronic blood loss or poor absorption of nutrients, both of which are serious.
Is it anemia?
Most of the time, fatigue is the first sign of anemia. Other early symptoms include lightheadedness, paleness, and sensitivity to cold. Later, women may experience ringing in their ears; a sore tongue; spots before their eyes; and spooned, ridged, or brittle nails. Some women develop pica, a craving for nonfoods, such as ice.
To diagnose anemia, a clinician will order a complete blood count (CBC), which measures hematocrit (the percentage of red blood cells in a given volume of blood) and hemoglobin concentration. A woman is considered anemic if her hemoglobin is less than 12 grams per deciliter and her hematocrit is less than 37%. Additional tests may be ordered to study the size, shape, and color of the red blood cells; to determine whether the bone marrow is producing enough of them; and to measure blood levels of iron, vitamin B12, and folic acid.
Identifying the cause requires a medical history, a physical exam, and often a fecal occult blood test. Other possible tests include an upper endoscopy (using a narrow lighted tube down the esophagus to view and take samples of the upper gastrointestinal tract) or a colonoscopy (to examine the large intestine).
Pumping up iron
The goal of treatment isn't simply to improve blood counts, but also to replenish iron stores. This usually takes 6-12 months. While investigating the cause of the iron deficiency, most doctors will recommend a diet rich in iron and other nutrients. Iron supplements may help, but physicians turn to these only when a blood test confirms iron deficiency and after dietary measures have failed. Taking iron when you don't need it isn't a good idea. In people who are at risk due to genetic factors, excess iron intake can lead to an increased risk for heart disease, diabetes, and some cancers.
Optimize your iron intake
Premenopausal women should make an effort to consume enough iron-rich foods (see box, page 5).
Iron found in meat, fish, and poultry is in a chemical structure called heme that allows the iron to be easily absorbed. Iron from vegetable sources (nonheme iron) is not. But you can boost the absorption of iron from these foods by including in the same meal some meat or vitamin C-rich foods such as orange or grapefruit juice, broccoli, cabbage, and tomatoes.
Vitamin E, calcium, and medicines such as proton-pump inhibitors or H2-receptor agonists (taken for heartburn symptoms) can interfere with iron absorption. So can dairy products, tea, and coffee. So eat these foods either one hour before or two hours after you take your iron. Some iron-rich foods such as spinach, kale, beets, and Swiss chard also contain oxalic acid, which reduces iron absorption, so consumption of these foods should be limited.
Iron supplements are best absorbed when taken between meals, on an empty stomach. Because this may cause distressing side effects such as nausea, diarrhea, constipation, or cramping, your doctor may suggest taking half the recommended dose at mealtime. Stool softeners or laxatives can help with constipation. Some supplements come with vitamin C, which promotes iron absorption. Iron injections are an option if oral therapy is intolerable or blood loss persists.
Iron supplements can alter the effectiveness of certain medications. These include etidronate (taken for osteoporosis); penicillamine (commonly prescribed for arthritis); cimetidine (taken for ulcer symptoms); and certain antibiotics including oral tetracycline and quinolones. Some studies also suggest that iron supplements reduce the absorption of zinc. Staggering your doses may help, so ask your physician about how to do so.
Postmenopausal women don't need as much iron as younger women. In fact, healthy older women who take a multivitamin with iron should consider switching to one that doesn't have iron.
Losing iron through the digestive tract
Blood loss due to chronic bleeding of the digestive tract can lead to iron-deficiency anemia. Regular use of anti-inflammatory drugs such as aspirin or ibuprofen can cause such bleeding, as can ulcers, hemorrhoids, gastroesophageal reflux disease (GERD), inflammatory bowel disease, and cancer of the stomach or colon. Bleeding in other organ systems, such as the urinary tract, may also contribute.
Rapid bleeding from the large intestine and rectum is obvious as bright red blood in the stool or on toilet paper. Excessive bleeding from higher up in the gastrointestinal tract makes bowel movements look black and tarry. But slow bleeding from the upper intestine or stomach often has no obvious clues. (A fecal occult blood test can help find hidden blood loss.) Bleeding, both obvious and subtle, can occur with bladder and kidney cancer as well.
Certain medical conditions -- celiac disease or inflammatory bowel disease --interfere with the ability to absorb iron, as can surgical removal of part of the stomach.
Oral iron supplements
Legend for Chart:
A - Name
B - Common brand names
C - Comments
Ferrous Feosol, Feratab, Fer-Iron,
sulfate Fero-Gradumet, Ferospace,
Ferralyn, Mol-iron, Slow Fe
Usually the cheapest form. Well absorbed.
Can cause stomach cramping, nausea,
vomiting, dark stools, and constipation;
less often, diarrhea and heartburn.
Ferrous Fergon, Ferralet, Simron
Slightly more expensive than ferrous
sulfate. Slightly fewer side effects.
Ferrous Femiron, Feostat, Ferro-
fumarate Sequels, Fumasorb,
Fumerin, Hemocyte, Ircon,
Similar to ferrous gluconate.
Polysaccharide Ferrimin, Hytinic, Niferex,
iron Nu-Iron, Poly Iron
May cause less nausea and constipation
than other oral preparations. Taking
it with vitamin C increases absorption.
Some sources of iron
Heme iron Nonheme iron
lean red meats broccoli
kidney leafy greens
oysters dried beans
tuna dates and raisins
salmon dried prunes
turkey fortified cereals
chicken blackstrap molasses