Potassium

Potassium (K), a macromineral, is also an important electrolyte, acting as the major cation of intracellular fluid (small amounts are also present in extracellular fluid). Cellular uptake of potassium, coupled to simultaneous expulsion of sodium (a process driven by cell membrane bound ATPase pumps), serves to create electrochemical gradients essential for the uptake of nutrients and numerous other processes, such as nerve innervation and muscle contraction. An average adult male is estimated to contain 1.6 - 2.0 g of potassium / kg of body weight, with total body potassium proportionate to lean tissue mass. Potassium is present in a wide variety of foods including bananas, plums, raisins, tomato juice, pulses, nuts, seeds, milk, fish, beef, chicken, liver and bread.

 

Functions

In addition to being an integral component in the maintenance of cellular membrane potentials, potassium is also a cofactor for the enzyme pyruvate kinase, which is involved in the metabolism of carbohydrate, and is essential for lean tissue development and correct renal function. Roles for potassium in the regulation of insulin secretion and blood pressure are also becoming increasingly apparent.

Reference Intake (RI)

 

    AGE

   CHILDREN

    MALES

FEMALES

MALES

FEMALES

PREGNANCY

YEARS

1-3

4-6

7-10

11-14

15-17

11-14

15-17

18-64

65+

18-64

65+

 

Potassium (mg / d)

800

1100

2000

3100

3500

3100

3500

3500

3500

3500

3500

(No increment)

 

    MONTHS

0-3

4-6

7-9

10-12

LACTATION

Potassium (mg / d)

800

850

700

700

 (No increment)

 

Food Sources

PRODUCTS

White Beans

Dark Leafy Greens

(spinach)

Baked Potatoes  (with skin)

Dried Apricots

(mg / 100 g)

 561

 558

 535

 1162

PRODUCTS

Butternut Squash (baked)

Yoghurt (plain, low-fat)

Salmon

Avocado

(mg / 100 g)

 437

 255

 628

 485

 

Deficiency / Toxicity

Dietary deficiency of potassium is unlikely due to it's extensive distribution in staple foodstuffs. However, some studies have indicated low potassium status in Western populations due to poor intake of fruit and vegetables. Epidemiological evidence also points to a link between low potassium intake and risk for the development of a number of chronic diseases including hypertension and osteoporosis.   

Abnormally low plasma potassium levels, referred to as hypokalaemia, may result from prolonged vomiting, use of certain diuretic agents, some forms of kidney disease, or metabolic abnormalities. Symptoms of hypokalaemia, arising from disruptions to cellular membrane potentials and cellular metabolism, include feelings of fatigue, nausea, muscle weakness and cramping, adominal pain, and constipation. Severe hypokalaemia may result in muscle paralysis or disruption to normal heart rhythm (cardiac arrhythmia), which may be fatal if untreated. 

As potassium levels within the body are regulated predominantly by the kidneys, accumulation of excess levels during normal renal function is almost impossible.

Factors influencing the uptake of potassium

Alcoholism, magnesium depletion, overuse or abuse of laxatives, use of diuretics (thiazides or furosemide for example) or corticosteroids, are factors that may hinder the uptake of potassium.

Magnesium may assist the uptake of potassium.