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Salt intake, salt restriction, and primary (essential) hypertension

Lawrence J Appel, MD, MPH
Section Editors
George L Bakris, MD
Norman M Kaplan, MD
Deputy Editor
John P Forman, MD, MSc


Sodium, commonly consumed as sodium chloride (table salt), is a major component of our food supply. Although sodium can be consumed in nonchloride forms (sodium bicarbonate [ie, baking soda] and monosodium glutamate [MSG]), salt provides approximately 90 percent of dietary sodium [1]. In the United States, the quantity of sodium is typically reported as milligrams or millimoles of sodium, whereas in other parts of the world, in the scientific literature, and in recommendations, the quantity of sodium is reported as grams of salt (sodium chloride) rather than as sodium alone (to convert between units: grams of salt x 393 = milligrams of sodium; millimoles of sodium x 23 = milligrams of sodium).

Sodium is the principal cation of the extracellular fluid and functions as the osmotic determinant in regulating extracellular fluid volume and, therefore, plasma volume. Approximately 95 percent of the total sodium content of the body is found in extracellular fluid. Sodium is also an important determinant of the membrane potential of cells and the active transport of molecules across cell membranes. The concentration of sodium within the cell is typically less than 10 percent of that outside cell membranes, and an active, energy-dependent process is required to maintain this concentration gradient.

The relationship between sodium intake and blood pressure (BP), as well as the effects of sodium reduction in patients with uncomplicated primary hypertension (formerly called "essential" hypertension), are discussed in this topic review.

The importance of a reduced sodium intake, as well as fluid removal with diuretics, for volume management BP control in patients with chronic kidney disease is discussed elsewhere. (See "Overview of hypertension in acute and chronic kidney disease", section on 'Benefits of sodium restriction' and "Antihypertensive therapy and progression of nondiabetic chronic kidney disease in adults", section on 'Importance of salt intake'.)

The relationship of other factors to the development of hypertension, the evaluation of the hypertensive patient, and the management of hypertension in general and in specific subpopulations are discussed elsewhere. (See appropriate topic reviews.)

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Literature review current through: Sep 2017. | This topic last updated: Oct 11, 2017.
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