| Major minerals are sodium potassium, chloride, calcium, phosphate, and magnesium
|
| With the exception of chloride, deficiencies and excess of these cause clinical symptoms. Sodium is important in the maintenance of extracellular fluid volume (Chapter 22). It participates in electrophysiological phenomena and, together with potassium, is essential in maintaining transmembrane potential. Most of the chloride anion (70%) also resides in the ECF. Sodium (and water) overload is seen in cardiac failure and also in renal disease (Chapter 22) and low sodium intake is recommended in the prevention of hypertension.
|
| Potassium is the main intracellular cation. The maintenance of normal plasma potassium concentration is important because hyperkalemia and hypokalemia lead to arrythmias that may cause cardiac arrest. Also, dietary potassium intake needs to be limited in renal disease because of its impaired excretion and a tendency to hyperkalemia (Chapter 22). Potassium is contained in vegetables and fruit, particularly bananas, and in fruit juices.
|
| Calcium and phosphate balance is important for maintaining bone structure (Chapter 24). Calcium is present in milk and milk products, and in some vegetables. Phosphates are present in plant and animal cells.
|
| page 303 |  | | page 304 |
| Magnesium is important for skeletal development and for the maintenance of electrical potential in nerve and muscle membranes. It is also a co-factor for ATP-requiring enzymes, and it is important for the replication of DNA and for the RNA synthesis. Magnesium deficiency develops in starvation and malabsorption, may be due to the loss from the gastrointestinal tract in diarrhoea and vomiting, and sometimes occurs as
a result of diuretic treatment and surgical procedures on the gastrointestinal tract. It is also associated with acute pancreatitis and alcoholism. Hypomagnesemia is often accompanied by hypocalcaemia. Magnesium deficiency leads to muscle weakness and cardiac arrythmias.
|
|
