CZ:Featured article/Current
Potassium in nutrition and human health
To maintain life and health, the diet of humans must contain the chemical element,potassium, in its ionic form (K+), usually consumed as potassium salts of organic acids in food (e.g., potassium citrate), found most abundantly in non-grain plant foods (vegetables and fruits). In 2004-2006, and again in 2010, the Institute of Medicine of the National Academies of Science [1] and its Food and Nutrition Board [2] [3] recommended that adult humans consume 4700 milligrams (mg) of potassium per day, or more, which, calculated from the atomic mass of potassium (39.1 mg per mmol), corresponds to 120 millimoles (mmol) potassium per day: 4700 mg/39.1 mg/mmol=120 mmol. That recommended intake of potassium substantially exceeds estimates from recent surveys of average intakes by the general population, raising the possibility that a persisting state of suboptimal body potassium content, and rate of throughput of potassium, prevails in the general population. [4] [5] [6]
Subsequent sections will discuss potassium intake recommendations for children and special groups, as well as more recent perspectives on the 'optimal' requirements for dietary potassium in humans.
General considerations
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 compose. Among other metabolic functions, potassium plays a role in the synthesis of proteins and in the biochemical transformations required for carbohydrate metabolism.
Potassium plays an esential role in maintaining the electrical potential difference across the cell's plasma membrane, the intra- to extra-cellular electrical potential difference, typically referred to as the 'membrane potential'. That physicochemical regulatory function importantly enables normal transmission of information along nerves (nerve impulse transmission), normal contraction of muscle fibers, and normal functioning of the heart. The concentration of potassium inside cells (the intracellular fluid) exceeds that outside cells (the extracellular fluid) by an order of magnitude (~30 times), whereas the extracellular concentration of sodium exceeds that of its intracellular concentration by an order of magnitude (~10 times), the reverse of the situation with potassium. Those concentration differences between potassium ions and sodium ions generates the membrane potential, the inside potential negative with respect to the outside potential. A protein-based ion-pumping mechanism located within the lipid bilayer of the....
By influencing the electrical potential difference across the cell membrane, the ratio of the concentrations of potassium in intracellular fluid (ICF) to that in the cells' surrounding extracellular fluid (ECF) has important effects on the rate of transmission of electrical activity (pulses) along nerve fibers and skeletal muscle cells, which, among other things, affects the degree of contraction of the smooth muscles of arteries and arterioles (vascular tone).[7] Inasmuch as extracellular potassium varies in the 3-6 mmol/L range, while intracellular potassium concentrations average about 145 mmol/L, small changes in extracellular potassium concentration have a greater effect on the ICF-to-ECF potassium concentration ratio than similar small changes in intracellular potassium concentration. Subsequent sections discuss the implication of changes in the ICF-to-ECF potassium concentration ratio in human physiology.
| notes |
|---|
|