Iron, one of the most abundant metals on Earth, is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Iron has the longest and best described history among all the micronutrients. It is a key element in the metabolism of almost all living organisms. In humans, iron is an essential component of hundreds of proteins and enzymes. Excellent food sources of iron include chard, spinach, turmeric and thyme. Iron is vital to the health of the human body, and is found in every human cell, primarily linked with protein to form the oxygen-carrying molecule hemoglobin. The human body contains approximately 4 grams of iron. Iron deficiency can cause anaemia resulting from low levels of haemoglobin in the blood. Iron deficiency is the most widespread mineral nutritional deficiency both in Britain and worldwide.