Iron is a case in point. Iron deficiency is often listed as the most common nutrient deficiency in the world. Iron deficiency anemia affects work capacity, by reducing the blood hemoglobin that is necessary for the transport and utilization of oxygen. Iron deficiency in pregnant women is associated with a greater likelihood of low birth weight infants. In infants and young children, iron deficiency adversely affects mental development and behavior.
Iron deficiency is much less common in males or older adults.
But before you reach for an iron supplement, consider the other side of this double-edged sword. In populations of European origin, approximately 1 in 300 people have hemochromatosis, a genetic abnormality of excessive iron stores that results in liver damage and higher rates of several cancers. Ten percent of these populations are carriers of the gene for hemochromatosis. Scientist are testing hypotheses that high iron stores may increase everyone's risk of chronic diseases, such as cancer and heart disease. We recently tested the effects of iron supplements on the body's control of iron absorption.