For as long as most of us can remember, doctors, parents and even the spinach-chugging Popeye have been reminding us to pump plenty of iron into our diets. After all, it's a vital component of red blood cells. Not getting enough can reduce stamina and interfere with learning, while severe shortages can cause anemia.

Despite all the reminders, iron remains the top nutritional deficiency for women in the U.S. It's not that most of us don't try to get our fill by eating iron-rich foods. The problem is that the body doesn't absorb much of the iron in them. In fact, says registered dietitian Linda Green of Advocate's Good Shepherd Hospital in Barrington, the body retains only about 5 percent of the iron in non-animal sources—foods like cereals, dried fruits, and, brace yourself, Popeye, even spinach.

Our bodies are much better at absorbing the iron from animal sources like meat, fish and poultry. Still, with only about 4 mg of iron in a 3-ounce portion of lean steak, it's tough for many of us to meet the 10 mg recommended daily requirement. And menstruating and pregnant women have an even more difficult time, since they require 15 mg and 30 mg, respectively, to meet their daily needs. Vegetarians and those who have cut back on red meat also may have a problem getting enough iron.

If you're a vegetarian or a premenopausal or pregnant woman, talk to your doctor about taking an iron supplement (prenatal vitamins are usually iron-fortified). Here are a few other ways to increase your iron level without taking supplements:

• Add an animal source of iron to a non-animal source in the same meal (for example, add chicken to beans). This doubles the absorption level of the non-animal source.

• Eat foods rich in vitamin C along with iron-fortified foods. This also doubles the absorption level of iron. (Add raisins to cereals, or have a glass of orange juice with cereal.)

• Use iron skillets for simmering sauces and stews, since tomato-based foods will pick up some iron from the skillet.

But you can overdo a good thing. Getting too much iron can be dangerous for the 1 million Americans with hemochromatosis, a disorder in which the body amasses large amounts of iron that can cause heart disease, liver cancer, diabetes and other problems.

A good rule of thumb is if you're healthy and eat a balanced diet, you probably don't need iron supplements-unless you're premenopausal, pregnant or a vegetarian. Talk to your doctor about your individual needs.