Iron

Daily Value: 18 milligrams

Good Food Sources: Beef, Cream of Wheat cereal, baked potatoes, soybeans, pumpkin seeds, clams

There's no doubt that many of us can use more iron than we're getting. Roughly 20 percent of Americans are deficient in this mineral. The group most likely to be coming up short: women in their reproductive years.

"I would say that women need to be a little more thoughtful than men about iron, probably in the same way that women should be a little more cautious about calcium intake because of osteoporosis," says Adria Sherman, Ph.D., professor and chair of the Department of Nutritional Sciences at Rutgers University in New Brunswick, New Jersey.

Iron, which is absorbed in the intestines, comes in two forms: heme and nonheme. Found in meats, the heme form is well-absorbed. Men get about two-thirds of their iron needs met by heme iron; the amount varies for women. Nonheme iron is found in vegetables and isn't as well-absorbed.

Most of the iron you consume goes to form hemoglobin, the substance that helps your red blood cells transport oxygen from your lungs to the rest of your body. The rest is stored in the bone marrow, liver, spleen and other organs.

Because iron also plays a key role in helping to prepare your immune system's infection fighters for battle, a deficiency may lead to colds. Low iron levels can also cause fatigue, pallor and listlessness--hallmarks of anemia, says Dr. Sherman. In children, low iron levels can cause stunted growth and impaired learning. Other symptoms of iron deficiency include split nails, a sore tongue and cold hands and feet. An annoying condition called restless legs has also been linked to low iron.

Some experts even believe that vague gastrointestinal problems such as gas, belching, constipation and diarrhea may be rooted in iron deficiency. If you suspect that you may be deficient in iron, ask your family doctor or your gynecologist to test your blood at your yearly exam.

Using Iron Safely

Here's a fact about iron supplements that should encourage healthy respect: Researchers studying ten years of records at a large Winnipeg, Manitoba, hospital found that an average of five iron supplement poisonings occur each year.

Although accidental iron poisonings occur most often in children who ingest supplements containing iron that are formulated for adults, high levels of iron can also be toxic to adults. Therefore, most experts recommend that you don't take iron supplements unless your doctor confirms the need with a blood test.

A daily intake of 25 milligrams or more for an extended period of time may cause undesirable side effects. Symptoms of acute iron poisoning include pain, vomiting, diarrhea and shock. Still, doctors normally recommend iron supplementation for pregnant women and for infants.

Among the variety of iron supplements, experts say those made with ferrous salts are better absorbed. Among them, ferrous sulfate is considered best.

Slow-release and coated iron tablets may cause less diarrhea, nausea and abdominal pain, but since the site of maximum absorption is the beginning of the small intestine, delaying the time of release decreases the overall amount of iron absorbed by your body. Taking the tablets with a meal could go a long way in helping to reduce stomach upset, but then again, the food may interfere with the iron absorption. Therefore, since it is advantageous for absorption, experts recommend taking iron supplements between meals if you do not experience side effects or you can tolerate iron taken in this manner.