2.4.2 Magnesium (Mg)
Magnesium is also present in bone in the body and in the soft tissues, although in much lower quantities than calcium. It is important in the activity of more than 300 enzyme systems, in particular those using ATP. It is involved in the synthesis of proteins and in many other reactions in the body. In plants, magnesium is part of the chlorophyll molecule, so it is present in green vegetables and is found widely elsewhere in the diet, so intake is normally adequate. In some areas, there are low levels of magnesium in the drinking water, due to the lack of magnesium compounds in the underlying rocks. In such areas, surveys show that coronary heart disease is more common, though no clear causative link between magnesium and coronary heart disease has yet been found.