Iron (Fe)
Iron is one of most important trace elements because of its role in the hemoglobin of the red blood cells that deliver oxygen to all cells and tissues in the body. Around two thirds of the body's total iron supply is found in the red blood cells and in muscle tissue. Around a third of our iron is stored in the liver, spleen, and bone marrow where the red blood cells are produced. A very small amount is used in vital enzymes in the brain, among other places. The organism has a limited ability to excrete iron through the intestinal system, the bile, the urine, and the skin. Moreover, iron is excreted through menstrual blood and breastmilk. An adult contains around 3-6 grams of iron. One litre of blood contains around 500 mg of iron. It is iron that gives blood its red colour, and the oxygenated blood in our arteries is lighter than the deoxygenated blood in our veins.