Potassium in nutrition and human health

To maintain health, the diet of humans must contain potassium, in its ionic form (K⁺), in millimolar amounts. In 2005, the U.S. Department of Health and Human Services and U.S. Department of Agriculture recommended that adult humans consume 4700 milligrams (mg) of potassium per day, which amounts to 120 millimoles (mmol) potassium per day, inasmuch as the atomic mass of potassium equals 39.1 mg per mmol (4700 mg/39.1 mg/mmol =120 mmol).

Humans must regularly consume potassium as the body does not store it and the kidney continues to excrete it in the urine even when potassium intake ceases.

Potassium ranks as the most abundant cation (positive ion) inside animal cells (intracellular), and as such contributes critically in numerous important ways to the optimal functioning of cells and therefore to optimal functioning of the organ systems and individuals they construct. It plays a role in the synthesis of proteins and in the biochemical transformations required for carbohydrate metabolism.

The ratio of the concentrations of potassium in intracellular fluid (ICF) and in its surrounding interstitial extracellular fluid (ECF) has important effects of the rate of transmission of electrical activity (pulses) along the nerve fiber and skeletal muscle cells, and affects the degree of contraction of arteries and arterioles (vascular tone). As extracellular potassium varies in the 3-6 mmol/L range, while intracellular potassium concentrations averages about 145 mmol/L, small changes in extracellular potassium concentration have a greater effect on the ratio than small changes in intracellular potassium concentrations. This article discusses the implication changes in the ICF-to-ECF potassium concentration ratio in sections below.

In healthy persons, the amount of potassium consumed equal the amount excretion, largely by the kidney and gastrointestinal tract.

Disturbances relating to body potassium deficiency may result from:

• inadequate consumption of potassium-rich foods;
• inappropriate excretion in urine;
• inappropriate excretion of potassium in feces.

Disturbances relating to body potassium excess may result from:

• kidney diseases that impair the kidney’s ability to excrete potassium in urine;
• deficiency of hormones that act to promote kidney and gastrointestinal excretion of potassium.

Subsequent sections will elaborate on the above introductory concepts.