History
In 1807 the English chemist Humphry Davy passed an electric current through molten caustic potash and isolated metallic potassium for the first time. The name comes from "potash," plant ash leached in pots, while the symbol K comes from the Latin kalium, from the Arabic for alkali. The 20th century revealed potassium's role in cell membrane potential, and the international INTERSALT study of the 1980s linked the urinary sodium-to-potassium ratio with blood pressure.
What it does
The sodium-potassium pump keeps potassium inside cells and sodium outside, creating the electrical gradient behind nerve signals, muscle contraction and a steady heartbeat. Eating enough potassium increases sodium excretion, lowers blood pressure and reduces stroke risk. Bananas, potatoes, sweet potatoes, spinach, beans, tomatoes, avocados and yogurt are rich sources, yet most people fall short of the recommended intake.
Deficiency and excess
Severe vomiting or diarrhea and diuretics can cause hypokalemia, with weakness, cramps and arrhythmias. Failing kidneys cannot clear potassium, causing hyperkalemia, which can trigger sudden cardiac arrest. People with chronic kidney disease or on some blood pressure drugs such as ACE inhibitors should discuss salt substitutes (potassium chloride) and supplements with a doctor. Low magnesium makes low potassium hard to correct.
This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.
FAQ
- How much potassium is in a banana?
- A medium banana has about 400 mg.
- Should I take potassium supplements?
- Healthy people can usually get enough from food; supplements should follow a doctor's advice after checking kidney function and medicines.
Sources reviewed: 2026-10-26
References
- Institute of Medicine. (2019). Dietary Reference Intakes for Sodium and Potassium. National Academies Press.
- Aburto, N. J., et al. (2013). Effect of increased potassium intake on cardiovascular risk factors and disease. BMJ, 346, f1378.
- Davy, H. (1808). On some new phenomena of chemical changes produced by electricity. Philosophical Transactions of the Royal Society, 98, 1–44.