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Control of electrolyte bal. Electrolyte requirements
Last reviewed: 08.07.2025
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Electrolyte concentrations in cell membranes must be tightly controlled to ensure cellular function throughout the body. Electrolyte imbalances, such as in cardiac muscle, can have deleterious effects, so the kidneys are well-adapted to maintaining electrolyte balance by conserving or releasing minerals such as sodium, chloride, potassium, calcium, and magnesium. Aside from the existence of an "appetite" for sodium chloride, there is no reason to assume that the intake of other minerals is regulated by similar reactions. Provided dietary energy intake is adequate, mineral intake usually exceeds requirements, resulting in a positive mineral balance.
Need for electrolytes
Electrolyte loss is accompanied by fluid loss in urine and sweat. Athletes and workers who sweat heavily on a daily basis may also lose large amounts of electrolytes, especially sodium and chloride. Potassium is also lost in sweat, although at much lower concentrations (usually < 10 mmol L-1) than sodium (20-100 mmol L-1). Since sodium concentrations vary among individuals, some are prone to severe sodium deficiency while others are not. The risks associated with heat and muscle cramps are related to sodium loss in sweat.
The amount of sodium chloride lost in sweat is quite significant. For example, a football player who trains 5 hours a day loses 8 liters of sweat (1.6 liters per hour). If his sweat contains an average of 50 mmol Na+ per liter, the total sodium loss is 9200 mg (23 g NaCI). This loss, which does not include the 100-200 mmol of sodium normally excreted in urine, indicates that many physically active individuals have large sodium chloride requirements to replace the sodium chloride lost in sweat.
Human sweat contains small amounts of dozens of substances, many of which are minerals. Even with heavy sweating, sweat losses of minerals such as magnesium, iron, and calcium are unlikely to cause mineral imbalances in most people. However, for some individuals, such losses may create additional nutritional needs, as in the case of calcium loss in sweat in physically active women. More research is needed to determine whether these individuals should increase their daily intake of these substances.
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