Sodium

Overview

Sodium is one of the body’s three major electrolytes (the other two being potassium and chloride). They exist as fully dissociated ions and are the main particles responsible for osmotic pressure in body fluids. Sodium is the primary extracellular electrolyte in body fluids. These substances are called electrolytes because they carry an electronic charge in their dissociated (ionic) state. Their ionic strength enables them to influence the solubility of proteins and other substances throughout the body.

Most Americans consume enormous amounts of sodium, from 10 to 35 times more than the recommended daily intake. Dietary sodium is easily absorbed from the intestine, carried by the blood to the kidneys where it is either filtered out and returned to the blood or excreted.

Dosage Info

Dosage Range

A reasonable dietary intake is from 1 to 3 grams per day.

Most Common Dosage

Since sodium is readily available in the diet it is not generally used as a nutritional supplement.

Dosage Forms

Most commonly available as tablets or powder (granular), it is also available in numerous intravenous solutions and other injectable medications (Rx only).

Adult RDI

None established

Adult ODA

None established

RDA

Interactions and Depletions

Depletions

Active Forms

Sodium chloride.

Absorption

Sodium is readily absorbed from the gastrointestinal tract.

Toxicities & Precautions

General

Sodium is considered safe when used in moderation.

Side Effects

High sodium intake is associated with edema and elevated blood pressure. (1) , (2) , (3)

Functions in the Body

Cellular Permeability

Sodium helps control and operate the sodium/potassium pump. This helps make the cell walls permeable and facilitates transport of materials across cell membranes.

Blood Pressure

In regulating body fluids, sodium has a major role in the regulation of blood pressure.

Muscle and Nerve Action

Sodium ions play a critical role in the transmission of electrochemical impulses for nerve function and muscle contraction.

Acid/alkaline Balance

Sodium helps regulate the acid/alkaline balance in the blood and lymph fluids.

Clinical Applications

21-Hydroxylase Deficiency

Infants born with a genetic defect known as salt-losing 21-hydroxylase deficiency require life-long salt supplementation in order to maintain proper plasma sodium concentrations. (4)

Heat Exhaustion

Heat exhaustion can result in a loss of body fluids, which can cause life-threatening hyponatremia. Adequate fluid and electrolyte replacement, including sodium is essential to re-establish homeostasis. (5)

Post-Exercise Rehydration

If fluids used to rehydrate the body after intense or prolonged exercise do not contain appropriate levels of sodium, the replacement fluids will simply result in greater urinary output. (6)

Diuretic-Induced Hyponatremia

Individuals ingesting elevated doses of thiazide diuretics frequently suffer from hyponatremia and require electrolyte replacement with sodium chloride solution. (7)

Symptoms and Causes of Deficiency

Sodium deficiency is rare in humans. Conditions that could cause sodium deficiency include starvation, excessive vomiting, severe diarrhea, and excess perspiration, in conjunction with a lack of water. Symptoms of sodium deficiency include muscle weakness, poor concentration, memory loss, dehydration, and loss of appetite.

Dietary Sources

Table salt is the most concentrated source of sodium. Enormous amounts of sodium (and chloride) are used in cooking and food processing. Often times this “hidden salt” contributes more to an individual’s daily diet than does the salt shaker. Protein foods generally contain more sodium than vegetables and grains. Fruits contain almost no sodium.

References

  1. View Abstract: De Wardener HE. The hypothalamus and hypertension. Physiol Rev. Oct2001;81(4):1599-658.
  2. View Abstract: Fleet JC. DASH without the dash (of salt) can lower blood pressure. Nutr Rev. Sep2001;59(9):291-3.
  3. View Abstract: Hayashida T, Ohno Y, Otsuka K. Salt-loading elevates blood pressure and aggravates insulin resistance in Wistar fatty rats: a possible role for enhanced Na+ -H+ exchanger activity. J Hypertens. Sep2001;19(9):1643-50.
  4. View Abstract: Mullis PE, et al. Sodium Chloride Supplement at Diagnosis and During Infancy in Children with Salt-losing 21-hydroxylase Deficiency. Eur J Pediatr. Nov1990;150(1):22-25.
  5. View Abstract: Backer HD, et al. Exertional Heat Illness and Hyponatremia in Hikers. Am J Emerg Med. Oct1999;17(6):532-39.
  6. View Abstract: Shirreffs SM, et al. Post-exercise Rehydration in Man: Effects of Volume Consumed and Drink Sodium Content. Med Sci Sports Exerc. Oct1996;28(10):1260-71.
  7. View Abstract: Spital A. Diuretic-induced Hyponatremia. Am J Nephrol. 1999;19(4):447-52.