Iron oligoelement is a trace element that enters the hemoglobin composition of red blood cells but also participates in enzymatic reactions necessary for cellular respiration. The body contains about 3 to 4 g of iron, mainly in the blood and muscles. The iron requirements vary according to gender and age. Iron deficiency results in a state of fatigue due to poor oxygenation of the blood. Pregnant women and high-level athletes are the people most likely to be deficient. Present in red meats and some cereals, iron can also be provided by dietary supplements.