Chlorine (chloride)
An electrolyte mineral, the main anion in body fluids, essential for fluid balance, stomach acidity and nerve transmission, supplied mostly by salt.
Chlorine (in the form of the chloride ion) is a major electrolyte, a partner of sodium. It makes up table salt (sodium chloride, NaCl) and is found in extracellular fluids. Roles: fluid and acid-base balance, nerve transmission, and above all the production of stomach hydrochloric acid.
A fresh angle (the forgotten component of stomach acidity): chloride is essential for making the stomach’s hydrochloric acid (HCl), the same acid that digests protein, helps absorb certain minerals (iron, calcium, B12) and kills ingested pathogens.
A little-known link: hypochlorhydria (too little stomach acid, common with age or prolonged use of antacids/PPIs) can impair digestion and absorption. Chloride is a building block of this protective acid, often forgotten in discussions of digestion.
Rarely deficient, but… dietary chloride is rarely lacking (salt is everywhere). However, major losses (prolonged vomiting, severe diarrhoea, extreme sweating, certain diuretics) can cause a deficit and an acid-base imbalance (metabolic alkalosis).
The link with sodium (and its nuances): since chloride comes mainly from salt, its intake follows that of sodium. The “too much salt” debate concerns chloride as much as sodium. Some research even distinguishes the specific effects of chloride on blood pressure.
Not to be confused with the chlorine in tap water or swimming pools: the disinfectant “chlorine” (dichlorine Cl₂, hypochlorite) is a different chemical from the nutritional chloride ion. Dietary chloride is essential and harmless; disinfectant chlorine is a chemical with a different use.
Sources: table salt, salty foods, seaweed, tomatoes, olives, rye, lettuce, celery.