Function

Potassium is the major cation of the intracellular fluid. Potassium plays a number of roles in the body.

  • In balance with extracellular sodium, helps maintain normal osmotic pressure and water balance.
  • Along with ionized sodium and hydrogen, helps control acid-base balance.
  • Plays a major role in skeletal and cardiac muscle activity.
  • In combination with ionized sodium and calcium, potassium helps regulate neuromuscular stimulation, transmission of impulses, and contraction of muscle fibers. This is particularly important to the proper action of heart muscle.
  • Potassium is also involved in carbohydrate metabolism and protein synthesis.

Absorption and Excretion

Dietary potassium is easily absorbed into the small intestine. Potassium is lost through urinary excretion. Through the renal aldosterone mechanism, potassium is lost in exchange for sodium. Approximately 160 mg of potassium is lost daily.

Clinical Conditions

Hyperkalemia

Hyperkalemia, or elevated serum potassium, is often a result of renal failure, whereby the normal clearance of potassium is prevented. Such failure can be caused by reduced aldosterone, a shift of potassium from the cells to the ECF, or increased intake, such as a too rapid intravenous infusion. Symptoms of hyperkalemia include weakening of the heart action, mental confusion, poor respiration, and numbness of extremities. Severe hyperkalemia results in paralysis of skeletal muscle.

Hypokalemia

Hypokalemia, or decreased serum potassium, may be caused by malnutrition or diarrhea and vomiting. Diarrhea causes direct loss of potassium from the stool. Vomiting actually causes potassium loss through the urine due to the metabolic acidosis and subsequent renal excretion of bicarbonate. The most common cause of Hypokalemia is renal loss, though some diuretic drugs also cause excess secretion of potassium. It is rarely caused by low intake of potassium. Hypokalemia can result in irregular heart muscle contractions.

Recommended Intake

The minimal requirement for potassium is set at 2000 mg for adults and children 10 years of age or older. The requirement for infants is in the range of 500 – 700 mg per day. Children require 350 – 600 mg per day.

Food Sources

Potassium is available in many foods. Good sources include legumes, whole grains, oranges, bananas, leafy vegetables, potatoes, and meat.

Previous section Next page Potassium page 2

Take a Study Break