Potassium is an essential dietary mineral that is also known as an electrolyte. It is called an electrolyte because it can conduct electricity when dissolved in water. Potassium is essential for maintaining proper health and was first isolated by Sir Humphry Davy in 1807. It is a soft metal that can easily be cut by a knife. About 95% of the potassium in the body is stored within cells while the rest is present outside the body cells.
Potassium is the principal positively charged ion in the fluid inside of cells, while sodium is the principal ion in the fluid outside of cells. Along with sodium, potassium helps to regulate the water balance in and outside of the cell. Potassium is actively "pumped" in to the cell from the surrounding extra cellular fluid, whilst its opponent, sodium, is pumped out. This creates an electrical charge across the cell membrane which is critical for nerve impulse transmission, muscle contraction, and heart function.
Other functions of potassium in the body include a role in lowering blood pressure and maintaining the proper electrolyte and acid-base balance in the body. It also assists in protein synthesis from amino acids and in carbohydrate metabolism. Potassium converts glucose into glycogen to provide fuel to the muscle and is fundamental for normal nerve and muscle function.
 Food Sources
The richest sources of potassium are fruits and vegetables. It can be found in a variety of fruits such as bananas, apples, citrus fruit, kiwi, prunes, and apricots. Dried apricots contain more potassium than fresh apricots. Vegetables including broccoli, peas, lima beans, tomatoes, potatoes (especially their skins) and sweet potatoes are all good sources of potassium. All meats (red meat and chicken) and fish such as salmon, cod, flounder, and sardines are good sources of potassium. Milk and yogurt, as well as nuts, are also excellent sources of potassium.
 Recommended Dosage
In 2004, the Institute of Medicine at the National Academy of Sciences issued new Adequate Intake (AI) levels for potassium. The recommendations are as follows:
- 0-6 months: 400 milligrams/day
- 6-12 months: 700 milligrams/day
- 1-3 years: 3.5 g (grams)/day
- 4-8 years: 3.8 g/day
- 9-13 years: 4.5 g/day
- 14-18 years: 4.5 g/day
- 19-30 years: 4.7 g/day
- 31-50 years: 4.7 g/day
- 51+ years: 4.7 g/day
- Pregnant women: 4.7 g/day
- Lactating women: 5.1 g/day
What can high-potassium foods do for you?
Potassium occurs naturally in a wide variety of foods. As a result, dietary deficiency of potassium is uncommon. However, certain conditions can result in very low plasma levels of potassium, a condition called hypokalemia. Hypokalemia is most commonly a result of excessive loss of potassium which can be due to chronic diarrhoea or excessive vomiting, use of some diuretics or some forms of kidney disease.
A lack of potassium most commonly will cause fatigue or muscle cramps, bloating, constipation and abdominal pain, confusion and irritability. But severe potassium deficiency, or hypokalemia, quickly leads to electrolyte imbalance which affects all muscles, nerves and numerous body functions. This can cause serious problems such as irregular heart function, nervous system impairment, and even death.
Elevated blood levels of potassium can be toxic and are referred to as hyperkalemia. Usually this is due to an underlying medical condition such as kidney disease. Hyperkalemia occurs when the potassium intake is more than what can be eliminated by the kidneys. Symptoms of hyperkalemia may include tingling of the hands and feet, muscular weakness, and temporary paralysis. The most serious complication of hyperkalemia is the development of an abnormal heart rhythm (cardiac arrhythmia), which can lead to cardiac arrest.
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