Biochemical functions of potassium
Because potassium is the most significant cation in the intracellular space, it is involved in the activity of every cell:
- Maintenance of potential difference across membranes – with this function, potassium is particularly important for cell membrane bioelectricity and cell excitability, respectively, that is, normal neuromuscular excitability, stimulus formation, and cardiac conduction – for these transport processes, ion channels enable the rapid movement of ions through the hydrophobic barrier of the cell membrane; we are talking about the K+-/ or Na+ channel, which transmit nerve signals
- Regulation of cell growth
- Transepithelial transport processes in kidney and intestine, including for glucose, amino acids.
- Influence on protective endothelial vascular functions.
- Maintenance of normal blood pressure
- Regulation of acid-base balance by influencing renal net acid excretion.
- Influencing the release of hormones, for example, insulin from beta cells.
- Carbohydrate utilization and protein synthesis.
- Synthesis and degradation of high-energy phosphate compounds in intermediary metabolism.
Because potassium is osmotically active, the mineral also plays a role in hydration. In this reaction based on electrostatic attraction, water molecules attach their negative end to positively charged ions and water dipoles attach their positive end to negatively charged ions. Hydration is in turn essential for other chemical processes. Potassium, in addition to maintaining osmotic pressure in the cell, is responsible for cell volume and regulation of water balance.Furthermore, some enzymes are potassium dependent and are activated by the essential mineral. These include some enzymes of glycolysis (the uptake of glucose in liver and muscle cells for glycogen synthesis is coupled to potassium uptake), oxidative phosphorylation, and protein metabolism. Because of the essential function of potassium to maintain the potential difference across membranes, disturbances in potassium homeostasis can affect neuromuscular excitability and conduction and lead to cardiac arrhythmias, among other consequences.
Potassium and blood pressure
According to epidemiological studies, there is a close correlation between potassium intake and blood pressure or increased risk of apoplexy (stroke). Potassium has the greatest importance in the nonpharmacological regulation of blood pressure.Thus, an older meta-analysis of 19 clinical trials was able to confirm this relationship-but the mechanism of action remained unclear. The first clinical-controlled study by Siani and coworkers (1991), in which hypertensives – persons with high blood pressure – had switched to a potassium-rich diet, showed a significant reduction in antihypertensive medication after one year.In another meta-analysis with both hypertensive and normotensive persons, the influence of potassium supplements (60 to 200 mmol/day, i.e. an amount of 2,346-7,820 mg) on blood pressure was investigated. The result was a clear reduction in blood pressure (systolic average of 3.11 mmHg and diastolic average of 1.97 mmHg). However, in the normotensive subjects – individuals with normal blood pressure – the effect was less than in the hypertensive patients. In the studies in which subjects had concomitant high sodium intake, treatment success was greater. A new randomized controlled intervention trial showed that low-dose supplementation of 24 mmol potassium/day (i.e., 938 mg potassium – this amount is approximately equivalent to the content in 5 servings of fresh fruits and vegetables) for 6 weeks also resulted in a decrease in mean arterial blood pressure of 7.01 mmHg, systolic blood pressure of 7.60 mmHg, and diastolic blood pressure of 6.46 mmHg. A meta-regression analysis of a total of 67 clinically controlled trials concluded that sodium reduction and increased potassium intake can make a significant contribution to the prevention of hypertension (high blood pressure).However, other studies that investigated the effect of potassium and sodium intake on blood pressure produced unconvincing or contradictory results.These studies found that increased potassium intake did not have preventive effects against hypertension (high blood pressure), nor was it effective in reducing elevated blood pressure.A larger clinical intervention study of hypertensive men treated with antihypertensive medications who consumed 3754 mg of potassium daily and very small amounts of sodium showed no relationship between potassium and sodium intake and elevated blood pressure. This did not reduce the level of antihypertensive medication dose.Although the protective effect of potassium against elevated blood pressure was absent in some studies, a daily potassium intake of 60 mmol (2,340 mg) is recommended to reduce the risk of fatal apoplexy (stroke).The level of potassium intake also affects salt sensitivity (synonyms: salt sensitivity; saline sensitivity; common salt sensitivity). Low potassium intake is associated with high sensitivity to table salt. Conversely, this is suppressed in a dose-dependent manner when dietary potassium intake is increased. Finally, a high-potassium diet, especially in individuals with marginal potassium intake, can reduce salt sensitivity and thus prevent or delay the onset of hypertension.
