Sodium

  • Sodium is present in all body fluids and is involved in maintaining the acid-base balance of body fluids.
  • Sodium is present mostly in the extracellular compartment. Together with potassium sodium helps regulate the movement of fluids in and out of tissues. These two ions are also involved in the propagation of the electrical signal along the axon by moving in and out of the nerve cell.
  • Sodium concentration in the body is mainly controlled by the kidneys, adrenal glands and the pituitary gland. The concentration of sodium in urine is controlled by aldosterone.
  • A high sodium (salt) intake has been positively linked to hypertension.
  • Interactions: A high potassium intake was shown to increase the urinary excretion of sodium. High potassium intakes were found to inhibit the reabsorption of sodium in the urinary tract. This is beneficial in individuals with high blood pressure. An excess of sodium in the body can lead to increased urinary excretion of calcium, which may affect bone health and promote the formation of kidney stones.
  • Best food sources: Most of the dietary sodium consumed by the North American population (some 90%) comes from salt (NaCl). The rest is represented by food additives such as monosodium glutamate, sodium nitrite, benzoate and citrate. The primary food source of sodium (as salt) are canned and processed foods where salt is added for flavor, prevention of spoilage and growth of hazardous bacteria such as C. botulinum. For more information on the role of salt and sodium-containing ingredients as food additives see the review in ref.1. It has been estimated that only about 12 percent of the total salt consumed comes from natural sources such as meat, milk, poultry, vegetables and drinking water, the rest comes from processed foods and condiments such as soy sauce, onion salt, ketchup, mustard, etc. According to the Institute of Medicine (US) the daily amount of sodium needed by healthy people 19-50 years old is 1500 mg, which corresponds to approx. 3500 mg salt (2).


References
1. Review: Sodium in Food and Health. International Food Information Council's website
2. Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Standing Committee
    on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board. 2004. National Academy Press.