Many enzyme (natural substances required for chemical reactions in the body) systems that are needed for the transfer of energy within our bodies must have a supply of magnesium. Magnesium also plays a part in the normal functioning of muscles and nerves. Magnesium occurs widely in foods, and cereals and vegetables are particularly good sources. An inadequate supply of magnesium in the diet is rare. However, deficiency can occur as a result of prolonged vomiting, diarrhoea und other gastrointestinal disorders. Chronic alcoholics frequently suffer from magnesium deficiency, which may be due to low intake and large losses in urine.