September 21, 2018

Sodium in human body

Sodium ions are the major cations of extracellular fluid. The requirement for sodium is not well defined, but human dietaries generally contain more sodium than necessary. The main role of sodium is in controlling water distribution and fluid balance in the body. Water follows sodium, so high levels of sodium in a fluid compartment take water with it.

It is an essential nutrient necessary for maintenance of plasma volume, acid–base balance, transmission of nerve impulses and normal cell function. Tissue formation, as in growth, requires about 1.1 -1.2 mg/kg of tissue gained; the requirement for maintenance should be considerably less.

Intakes vary widely; about 10 gm NaCl/day appears to be usual for most Americans, whereas intakes of 30 – 40 gm/day are not uncommon in Oriental countries where soy sauces and sodium glutamate are flavored as flavoring agents. About 75% of dietary sodium comes from eating packaged and restaurant foods, whereas only a small portion (11%) comes from salt added to food when cooking or eating.

The human body contains about 1.8 gm Na/kg at free bodyweight, most of which is present in extracellular fluids. Normal plasma levels for sodium in adults range from 136 to 146 mEq/L, and this balance is normally maintained by an average dietary intake of 90 to 250 mEq per day.

Sodium excretion tends to reflect sodium intake, and on an average diet, urine sodium excretion will range between 80 and 180 mEq per day. Sodium is absorbed by the intestines and excreted by the kidneys. If sodium levels begin to rise, the body will make adjustments by stimulating a thirst mechanism so that the person will want to drink additional water.

Sodium levels are influenced by the antidiuretic hormone (ADH). Increased secretions of ADH causes more water to be reabsorbed in the kidneys and decreased ADH secretion allows more water to be excreted.
Sodium in human body

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