Sodium: Benefits, Dosage, and Safety

What sodium is

Sodium is an essential dietary mineral and the principal positively charged electrolyte in the fluid outside of cells. In the diet it comes almost entirely from sodium chloride (table salt), with very little occurring naturally in unprocessed foods. Roughly three-quarters of Americans' salt intake comes from salt added during commercial food processing and manufacturing rather than from the salt shaker. Because average intakes far exceed physiological needs, sodium is treated by public health authorities as a nutrient of concern for overconsumption rather than deficiency.

What it does

• Maintains the electrochemical gradient (membrane potential) across cell membranes via the sodium-potassium (Na+/K+) ATPase pump, a process estimated to use 20 to 40 percent of resting energy expenditure
• Controls extracellular fluid volume and, with the kidneys and hormones, helps regulate blood pressure
• Supports normal nerve impulse transmission and muscle contraction
• Drives active transport and absorption of nutrients such as glucose and amino acids across membranes
• Contributes, with chloride, to acid-base (pH) balance in the body

How much sodium per day

These are population reference values from the NIH and the Dietary Reference Intakes. They are targets for healthy people, not personal prescriptions. The last column is the Tolerable Upper Intake Level, the most you should get from all sources combined.

Deficiency and who is at risk

Sodium deficiency shows up as hyponatremia, a serum sodium concentration below 136 mmol/L. Inadequate sodium intake alone rarely causes it because the kidneys conserve sodium and adjust water excretion. When it does occur it usually results from excess sodium and fluid losses or from dilution by too much water. Symptoms range from headache, nausea, fatigue, confusion, and muscle cramps to, in acute severe cases, brain swelling, seizures, and death if not promptly treated. Mild chronic hyponatremia has been associated with attention deficits, gait instability, falls, and bone loss.

Who may need more

• Endurance athletes and heavy sweaters may need electrolyte replacement including sodium during prolonged exertion or in extreme heat
• People with certain salt-wasting conditions or on treatments that increase sodium loss, under medical supervision
• Most people in the US and similar populations do NOT need more sodium and instead consume too much; supplementation is rarely warranted

Food sources

Most dietary sodium comes from salt added during commercial food processing, not natural food content. Top contributors are breads and rolls, cured and processed meats (deli meats, hot dogs, sausage, bacon), cheese, canned soups, canned vegetables, pizza, savory snacks, sauces, condiments (soy sauce, ketchup), pickles, and restaurant and fast food. Fresh fruits, vegetables, legumes, and unprocessed grains are naturally low in sodium.

Forms and absorption

Dietary sodium is overwhelmingly consumed as sodium chloride (table salt, sea salt, kosher salt), which is about 40 percent sodium by weight; salt content equals sodium content multiplied by 2.5. Sodium is also present as sodium bicarbonate, sodium citrate, monosodium glutamate, and various sodium-based preservatives and leavening agents. Supplemental and rehydration products include salt tablets, oral rehydration solutions, and sports electrolyte formulas (often combining sodium chloride with potassium and glucose). Bioavailability of dietary sodium is essentially complete; the body absorbs nearly all ingested sodium.

Safety, excess and interactions

Too much

Ingesting large amounts of salt acutely can cause nausea, vomiting, diarrhea, and abdominal cramps. Hypernatremia (serum sodium above 145 mmol/L) is much less common than hyponatremia and is rarely caused by dietary intake; it usually reflects water loss (burns, infections, osmotic diarrhea) or too little water intake. The main long-term concern with excess sodium is that high habitual intake raises blood pressure and thereby contributes to hypertension, a leading preventable risk factor for cardiovascular disease. Average US intakes (about 3,300 to 4,400 mg/day in adults) sit well above the 2,300 mg/day CDRR.

Interactions to know

• Diuretics: loop and thiazide diuretics increase urinary sodium loss and can contribute to hyponatremia; potassium-sparing diuretics affect the sodium-potassium balance
• Lithium: low sodium intake or sodium loss (from diuretics, sweating, or vomiting) reduces lithium clearance and can raise lithium blood levels toward toxicity; abrupt increases in sodium can lower lithium levels and reduce its effect
• Corticosteroids and other mineralocorticoid-active drugs: promote sodium and fluid retention
• NSAIDs and antihypertensive drugs (including ACE inhibitors and ARBs): high sodium intake can blunt blood-pressure-lowering effects, and these agents can alter renal sodium and potassium handling
• Salt substitutes and potassium-based products used in place of sodium can raise potassium and interact with potassium-sparing diuretics, ACE inhibitors, and ARBs

How status is measured

Sodium status is assessed by serum (blood) sodium concentration, with a normal reference range of about 136 to 145 mmol/L; below 136 mmol/L is hyponatremia and above 145 mmol/L is hypernatremia. Dietary sodium intake is best estimated from 24-hour urinary sodium excretion, since most ingested sodium is excreted in urine. Blood pressure is monitored as a functional consequence of chronic intake.

Sodium is a required nutrient on the FDA Nutrition Facts label, with a Daily Value of 2,300 mg for adults and children 4 years and older. It is regulated as a food component; salt (sodium chloride) is Generally Recognized as Safe (GRAS). Electrolyte and salt-tablet products are marketed as foods or dietary supplements under DSHEA and are not pre-approved by the FDA for safety or efficacy. The FDA has issued voluntary sodium-reduction targets for the food industry.

What the evidence supports

We grade the strength of evidence behind each common reason people take sodium, mirroring how the NIH describes it.