The major deficiency disease for iron is hypochromic microcytic anemia, often called iron deficiency anemia. In this form of anemia, the red blood cells are smaller than normal and pale in color due to low amounts of hemoglobin. Because of the low hemoglobin content of the blood, the tissues of the body become oxygen-starved, leading to symptoms such as listlessness, fatigue, irritability, difficulty swallowing, paleness, heart palpitations during exertion, and general lack of well-being.

However, because the symptoms of anemia appear only after all the body's stores of iron have been depleted, the usual tests for anemia are an unsatisfactory means of detecting iron depletion. Moreover, numerous studies have shown that even in the absence of anemia, iron deficiency may ave detrimental effect on learning ability, endurance, and general well-being. For example, when chronically fatigued women were studied, the researchers concluded that some of these women might have been suffering from iron deficiency, even though their hemoglobin was in the accepted range. Apparently, their normal range for hemoglobin was higher than average. In other studies, women who were clearly iron deficient and women who had low to normal hemoglobin levels were found to have a low tolerance for cold, which improved when they received iron supplements. Runners who are iron deficient but nonanemic have been found to have less endurance. Hen college students were studied, it was found that low iron may play a part in faulty attention spans. Another study indicated that iron supplementation of iron-deficient children improves their ability to learn Finally, both infants with anemia and infants with signs of iron deficiency but no anemia have shown significant improvement in mental development scores when supplemented with iron.

Because iron plays a role in immune system function, other deficiency symptoms include increased susceptibility to infection, reduced white blood cell counts, and impaired antibody production. Other widely diverse signs of possible iron deficiency was present in much a much higher percentage of sufferers. Animal experiments suggest that iron deficiency may contribute to high levels of fat in the blood and liver. In addition, new data indicate that a craving for salt may be a sign of iron deficiency.

Of all the nutrient allowances, the allowance for iron is the most difficult to obtain from dietary sources. This is why iron deficiency is the most common single nutrient deficiency in the world. Vast numbers of individuals become deficient in iron at some time in their lives, and large segments of the population are chronically deficient.

While iron deficiency is far from uncommon in men, children, and the elderly, the highest risk category is menstruating women. Healthy men have an iron reserve of 1,000 milligrams, and lose an average of 1 milligram of iron per day. In menstruating women, the iron reserve is not more than 200 to 400 milligrams. These women lose an average of 1.5 milligrams per day, and sometimes as much as 2.4 milligrams per day. In a study of female college students, only six of the seventy-four women studied-about 12 percent-were getting the RDA for iron. Other surveys have shown that 10-30 percent of women have iron iron deficits. In 2001, a national survey found that in 5,300 children six to sixteen years of age, iron deficiency was most common in girls (nearly 9 percent), and iron deficient children were more than twice as likely to have below average math scores than children with normal iron levels. The RDI for iron is 18 milligrams for all men and women. Yet women and girls have lower caloric requirements and consequently cannot meet their needs even when they follow a diet of carefully selected foods.

Pregnant women are at particularly high risk for low iron, with deficiencies as high as 60 percent. I usually recommend supplements for these women because their needs cannot be met by the average diet. Often, they had a marginal iron intake before becoming pregnant. Therefore, their iron stores are below optimum, putting them and their babies at risk.

Some researchers have expressed concern that vegetarian women may be at an even higher risk for low iron intake than nonvegetarians. Based on an actual analysis of their diet, the average intake is 11-14 milligrams per day for lacto-ovo vegetarian women. Although this is below the RDI, nonvegetarian women appear to have similarly low intakes.

Even when iron intake is sufficient, various factors can affect iron absorption. Low stomach acid, removal of part of the stomach,and malebsorption syndromes have all been shown to reduce iron absorption. In addition, calcium phosphate salts, tannic acid in tea, and antacids tend to interfere with absorption. Phytates, a substance found in whole grains, may interfere with iron absorption, too. However, the evidence for this is inconclusive. anemia

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