Sodium (chloride)

Sodium in our body exist as sodium and chloride ion dissolved in body fluid. There is no fluid that contains only sodium (a positive ion) without chloride (a negative ion).

Sodium (Na+) and chloride (Cl) are the principal ions in the fluid outside of cells (extracellular fluid), which includes blood plasma. They play critical roles in a number of life-sustaining processes.

Sodium concentrations are more than ten times lower inside than outside cells, and potassium concentration are 30 times higher inside the cell, than outside. Together, sodium and potassium concentration differences maintain the electrochemical gradient called membrane potential. Membrane potential is essential for normal function of the cell. The potential is regulated by the ion pump on the membrane, which is activated every time the gradient changes. The maintenance of the gradient is so important that the ion pump uses energy molecule called ATP to regulate it.

Most of our intake of sodium is from table salt, that is exactly sodium chloride. There are different salts available now on the market: like potassium or magnesium salts, often recommended for person with high blood pressure. But their taste is less salty than the original table salt. They are mixed with sodium chloride in order to make balance with this mineral intake.

Sodium deficiency (hyponatremia)

Sodium deficiency is very rarely caused by low sodium intake even in people with restricted intake of table salt.

Hyponatremia is a condition where sodium concentration is below 136 mmol/liter, and is caused by retention of fluids called dilutional hyponatremia, or by conditions that increase the loss of sodium like diarrhea and vomiting.

Symptoms of hyponatremia include: headache, nausea, vomiting, muscle cramps, fatigue, disorientation, and fainting.

Hyponatremia is a potential problem in individuals competing in very long endurance exercise events, like marathons, ultramarathons, and Ironman triathlons.

Adequate sodium intake

Food and Nutrition Board of the Institute of Medicine established an adequate intake level (AI) for sodium based on the amount needed to replace losses through sweat in moderately active people and to achieve a diet that provides sufficient amounts of other essential nutrients.

Table 1. Adequate Intake (AI) for Sodium, with Estimated Sodium Chloride (Salt) Equivalence
Life Stage Age Males and Females
Sodium (g/day)
Salt (g/day)
Infants 0-6 months 0.12 0.30
Infants 7-12 months 0.37 0.93
Children 1-3 years 1.0 2.5
Children 4-8 years 1.2 3.0
Children 9-13 years 1.5 3.8
Adolescents 14-18 years 1.5 3.8
Adults 19-50 years 1.5 3.8
Adults 51-70 years 1.3 3.3
Adults 71 years and older 1.2 3.0
Pregnancy 14-50 years 1.5 3.8
Breast-feeding 14-50 years 1.5 3.8

 

Excess sodium intake

Blood pressure

Since it is regulating the volume of blood and blood pressure, it is a fact that too much table salt increases the blood pressure. The National High Blood Pressure Education Program and the National Heart, Lung, and Blood Institute of the NIH recommend consuming no more than 6 grams/day of salt, and the Food and Nutrition Board of the Institute of Medicine recently recommended that adults consume no more than 5.8 grams/day of salt.

Kidney stones

Some studies have shown that abnormally elevated urinary calcium (hypercalciuria) increases the risk of developing calcium stones. It has been found that increased dietary sodium intake increases calcium excretion. This effect may be more pronounced in patients with a history of calcium-containing kidney stones.

Osteoporosis

Some studies suggest connection between increased sodium intake and risk of fractures in postmenopausal women. This finding is supported with the fact that increased sodium intake increases the excretion of calcium.

Gastric cancer

Studies conducted mainly in Asian countries indicate that high intake of salty food is associated with gastric cancer. Populations with high intakes of salted foods tend to have low intakes of fruit and vegetables, which are protective against gastric cancer.

 

 

 

 

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