Potassium 

Potassium is the primary intracellular cation (K⁺) found within the body’s intracellular fluid.¹ Potassium, sodium, and chloride are the main electrolytes that control water balance and action/electric potentials to conduct muscle/nerve impulses.

Absorption and Excretion:  Potassium, similar to sodium and chloride, absorption rate ranges between 90-95%. Potassium is absorbed along the intestines and is thought to be mostly absorbed in the colon.¹ Potassium is absorbed using a potassium-hydrogen antiport ATPase pump or diffused into extracellular fluid using potassium pumps; potassium is also necessary within the extracellular fluid.¹ Any excess potassium is regulated and excreted by the kidneys through urine.¹ Potassium is also regulated within the blood by sodium-potassium ATPases.¹

Storage and Circulation: The majority of potassium is found within intracellular fluid (97-98%).¹ There is only 4 mEq/L of sodium in extracellular fluid compared to 140 mEq/L in intracellular fluid.¹

Functions: Potassium has many functions within the body which include controlling fluid balance and electric/action potentials.¹ Fluid balance is controlled through the difference between the concentration gradient and charge of ions to maintain isotonicity - this is referred to as an electrochemical gradient.¹ Action/electrical potentials occur when gated channels open to allow sodium to enter the intracellular fluid and potassium to enter the extracellular fluid.¹ This allows for a muscle contraction or nerve impulse to occur, and the sodium and potassium reestablish their concentration within the extracellular and intracellular fluid once done.¹

Dietary Reference Intake (DRI) - The Adequate Intake (AI) for adult men and women (19 years and older) per day is 3400 milligrams and 2600 milligrams.² 

Deficiency/Toxicity - The body regulates potassium reabsorption through the renal system. Excess potassium in the blood is termed hyperkalemia, and too little potassium in the blood is termed hypokalemia.¹ Both conditions can be fatal by causing heart arrhythmias, CNS abnormalities, and more if not corrected. 

Dietary Sources of Potassium

Potassium is found naturally within a variety of foods in the diet. While bananas are notorious for their potassium content, other fresh, unprocessed foods contain potassium.  Some evidence suggests that the consumption of potassium decreases calcium excretion and lowers blood pressure compared to sodium which increases calcium excretion and blood pressure.¹ Potassium can be found in the following foods: 

Fruits/Vegetables - apricots, prunes, potatoes, tomatoes, avocado, bananas, celery, carrots, broccoli 

Dairy - milk, yogurt, cheese 

Meat/Seafood/Animal Product - chicken, trout/fish, pork, beef 

Grains/Legumes - kidney beans, soybeans, cereals, breads, wheat flakes, bran flakes

Source(s):

1. Denise M Medeiros and Robert E.C. Wildman, Advanced Human Nutrition, 4th ed. (Burlington, MA: Jones & Bartlett, 2019).

2. https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/