01 Before - Sodium chloride: what is it and how does it work in the body?

Sodium chloride (NaCl), better known as ‘table salt’ has many functions in the human body. NaCl is not only present in table salt, but can also be found naturally in foods in small amounts. NaCl becomes functional in the body when it dissolves into the ions sodium (Na+) and chloride (Cl-) (Hopkin et al., 2009). Na+ and Cl- are concentrated in different densities in intracellular and extracellular spaces in the body (Sitges-Serra. 2004), with highest concentrations found in the extracellular space. Active transport of sodium constantly takes place to keep intracellular concentrations constant. While Na+ is actively transported out of cells, K+ is being transported into cells, as intracellular K+ concentrations need to remain high (Hopkin et al., 2009). This Na+/K+ pump costs a lot of energy but is essential for the acid base balance and neural communication (Sitges-Serra. 2004). Furthermore, sodium plays a crucial role in osmoregulation. In order to maintain sufficient water volumes, sodium levels need to be high enough. The kidneys constantly adjust sodium concentrations through urinal excretion, to stabilize body water volume. Consuming sodium results in higher water retention, thus losing less via urine (Mallié et al., 2002; Rehrer, 2001). Athletes could benefit from this effect by taking in sodium before exercise, as the water retained can be used for exercise induced functions, such as thermoregulation (Coles & Luetkemeier, 2005). When sodium content drops below a certain level, the body will start having problems with its water management, leading to a cascade of effects (thermoregulation, energy management) that hamper proper functioning (Sharp. 2005). Low sodium consumption has been studied by Nishimuta et al. (2018). Minerals such as sodium (Na), calcium (Ca) and magnesium (Mg) are stored in the bone (Nishimuta. (1990); Ishizak. (1974)). When Na+, Ca2+ or Mg2+ reach inadequate levels in the body, the mineral needed is leached from the bone into blood vessels. However, this process is not mineral specific. According to Nishimuta et al. (2018), mineral absorption from the bone led to an increase in all minerals and not an increase in Na+ only (Na+ was the only undersupplied mineral). This unbalance in minerals, eventually after bone resorption, led to the wasteful excretion of excess Ca2+ and Mg2+ via sweat and urine. As Ca2+ and Mg2+ are needed for proper body functioning, this reduction could negatively affect performance (Clarkson. 1991).

The AIS classified NaCl as a category A ergogenic aid, as it fits in the category ‘electrolytes’ (Australian Institute of Sport, 2019).