Potassium

What Is Potassium?

Potassium is a major mineral and the primary intracellular electrolyte in the human body. Roughly 98 percent of the body's potassium is found inside cells, where it maintains a concentration of approximately 150 mmol/L — about 30 times higher than the extracellular concentration. This steep gradient is maintained by the sodium-potassium ATPase pump and is fundamental to cellular function.

Key Functions

• Blood pressure regulation: Adequate potassium intake blunts the blood-pressure-raising effect of sodium by promoting urinary sodium excretion and relaxing blood vessel walls.
• Nerve and muscle function: The potassium gradient across cell membranes sets the resting membrane potential, making action potentials in nerves and muscles possible.
• Cardiac rhythm: Potassium is critical for normal heart rhythm. Both hypokalemia (low) and hyperkalemia (high) can cause life-threatening arrhythmias.
• Bone health: Higher potassium intake is associated with reduced urinary calcium excretion and may support bone mineral density.
• Glucose metabolism: Potassium is required for insulin secretion; chronic deficiency impairs glucose tolerance.

Dietary Reference Values and Food Sources

The Adequate Intake (AI) for potassium is 2,600 mg/day for adult women and 3,400 mg/day for adult men. Most adults in Western countries fall short, averaging around 2,300 mg/day. Rich food sources include:

• Dried apricots, prunes, and raisins
• Cooked beans and lentils (700-900 mg per cup)
• Baked potato with skin (approximately 950 mg)
• Avocado (approximately 700 mg per fruit)
• Banana (approximately 420 mg)
• Leafy greens, tomatoes, and orange juice

Deficiency and Excess

Hypokalemia (serum potassium below 3.5 mmol/L) causes muscle weakness, cramps, constipation, and cardiac arrhythmias. It is most often caused by diuretic use, vomiting, or diarrhea rather than low dietary intake alone. Hyperkalemia is rare in people with healthy kidneys but is a serious concern in those with chronic kidney disease, who may need to restrict potassium-rich foods.