Interactions of sodium with other micronutrients (vital substances).
Calcium
Because of the interdependence between sodium and calcium with respect to their reabsorption in the kidney and the sodium effect on parathyroid hormone (PTH) secretion, increased sodium intake is associated with increased renal loss of calcium. Sodium (Na) and calcium (Ca) are excreted via the kidney in approximately the ratio of 2.3 g Na (equivalent to 6 g table salt): 24-40 mg Ca.Sodium is considered a mineral that can lead to bone loss (osteoporosis), as much of the calcium retention variation is explained by losses via the urine. In women, each gram of extra sodium can increase the amount of bone loss by 1% per year as excreted calcium is mobilized from bone. Although studies in animals have shown increased bone loss with high sodium intake, no controlled clinical trials have yet been conducted in humans to demonstrate the relationship between sodium intake and bone loss. However, in postmenopausal women, increased urinary sodium excretion – characteristic of increased sodium intake – has been associated with decreased bone mineral density. From the relationships described previously, it can be inferred that substitution (replacement) with the alkaline minerals potassium and calcium would be useful: potassium contributes to the maintenance of normal blood pressure, among other things, and calcium is needed for the maintenance of normal bones.
Potassium
Sodium is found predominantly outside the body cells in the body fluid, including the blood volume. Sodium is about 10 times more concentrated in the extracellular space than in the intracellular space. In contrast, potassium is mainly found in the intracellular space of the human body. There it is more than 30 times more concentrated than in the extracellular fluid.The different concentrations between potassium and sodium on the respective sides of the cell membrane lead to an electrochemical gradient known as membrane potential. This is essential for cell excitability, nerve signal transmission, muscle contraction and nerve function, among other things. To maintain this membrane potential, the sodium-potassium ratio of the diet or a balance between sodium and potassium is extremely important.Excessive sodium intake can result in a deficiency of potassium. According to epidemiological studies, there is a close correlation between potassium and sodium intake and blood pressure or increased risk of apoplexy (stroke). Potassium has the greatest importance in the non-pharmacological regulation of blood pressure. Increased intake of potassium increases natriuresis (excretion of sodium through urine). In addition, potassium has a dilating (widening) effect on the vascular wall. In a meta-analysis with both hypertensive (elevated blood pressure) and normotensive (normal blood pressure) subjects, the effect of potassium supplements (60 to 200 mmol/day, i.e. an amount of 2,346-7,820 mg) on blood pressure was studied. The result was a clear reduction in blood pressure (systolic average of 3.11 mmHg and diastolic average of 1.97 mmHg).However, in normotensive subjects – persons with normal blood pressure – the effect was less than in hypertensive patients. In the studies in which the subjects had a high sodium intake at the same time, the treatment success was greater.A metaregression analysis of a total of 67 clinically controlled studies 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 examined the effect of potassium and sodium intake on blood pressure produced unconvincing or contradictory results. A larger clinical intervention study of hypertensive men treated with antihypertensive medications who consumed 3,754 mg of potassium daily and very small amounts of sodium showed no association between potassium and sodium intake and elevated blood pressure. Furthermore, the level of potassium intake influences salt sensitivity (synonyms: salt sensitivity; saline sensitivity; saline sensitivity).A low potassium intake is accompanied by a high sensitivity to common salt. Conversely, this is suppressed in a dose-dependent manner when dietary potassium intake is increased. Finally, a diet rich in potassium, especially in individuals with marginal potassium intake, can reduce salt sensitivity and thus prevent or delay the onset of hypertension (high blood pressure). Potassium supplement recommendations:
- German Society for Nutrition (DGE) – adolescents and adults: 4,000 mg/d.
- World Health Organization (WHO) – adults: 3,500 mg/d, provided that a maximum of 2,000 mg sodium* is ingested.
- European Food and Safety Authority (EFSA) – adolescents aged 15 to 17 years and adults, including women in pregnancy 3,500 mg/d.
- Food and Nutrition Board (FNB) of the United States and Canada – adults: 4,700 mg/d.
* The conversion factor of sodium (in g) to table salt (in g) is 2.54, i.e., 1 g sodium is contained in 2.54 g table salt (NaCl).
