is essential to human life. Iron is an integral part of hemoglobin, the oxygen-carrying protein found in red blood cells. Marked iron deficiency causes a reduction in red cell size and hemoglobin content known as iron-deficiency anemia; this in turn causes fatigue, depression, reduced immunity, impaired mental function and many other symptoms. Iron-deficiency anemia due to malnutrition is a very common problem in developing countries, especially among children. In the US, however, deficiency occurs most commonly among menstruating women, due to cyclical blood loss.
Based on this fact, the famous “iron-poor blood” advertisements of the 1950s and 1960s popularized the notion that a majority of women could benefit from iron supplements. However, this idea does not have widespread acceptance, to say the least. According to conventional medical wisdom, iron deficiency does not cause symptoms until it reaches the point of causing anemia. In addition, during the 1980s and 1990s, a theory developed claiming that excess iron can increase risk of heart disease and strokes. The value of iron supplements for women without iron-deficiency anemia is therefore quite controversial.
The situation has begun to change in recent years. The excess iron-increased heart attack theory has begun to lose ground, and at the same time, a growing body of evidence suggests that marginal iron deficiency does indeed cause problems.
The body stores iron in the form of ferritin. Accumulating evidence indicates that non-anemic women with low ferritin levels may in fact feel somewhat tired, and that iron supplementation might increase their energy and physical performance. Thus, the “iron-poor blood” advertisements have been partially vindicated. Furthermore, a study published in March 2007 suggests that iron supplements may improve mental function in non-anemic women with low ferritin.
This study, reported in the
American Journal of Clinical Nutrition
, evaluated 149 women with varying levels of stored iron–ranging from adequate iron through mild deficiency to true iron-deficiency anemia. All participants were given either iron supplements or placebo over a period of 16 weeks.
At the beginning of the study, tests of mental function showed a direct relationship between iron status and brain function. On average, participants with anemia performed least well on these tests, while participants with mild iron deficiency performed in the middle and those with adequate iron did the best. By the end of the study, performance improved markedly among those who showed an increase in iron stores. In other words, those who were deficient in iron (whether anemic or not) benefited from iron supplements more than they benefited from placebo. However, those who were not deficient did not show improvement.
The bottom line: Don’t take iron supplements unless lab tests show that you are genuinely deficient. However, check measures of iron storage (such as ferritin), because even mild iron deficiency, too mild to cause anemia, may impair your physical and mental function.
Murray-Kolb LE, Beard JL. Iron treatment normalizes cognitive functioning in young women.
Am J Clin Nutr