Sodium (Na) - Nutrition Minerals

Sodium (Na)

Sodium is an electrolyte whose primary function is the control of fluid balance in the body. It controls the extracellular fluid and is essential for osmosis. Sodium is also necessary to maintain the acid-base balance in the body. In addition, it partici-pates in the transmission of nerve impulses essential for normal muscle function.

Sources.The primary dietary source of sodium is table salt (sodium chlo-ride), which is 40% sodium. (One teaspoon of table salt contains 2,000 mg sodium.) It is also naturally available in animal foods. Salt is typically added to commercially prepared foods because it enhances flavor and helps to preserve some foods by controlling growth of microorganisms. Fruits and vegetables contain little or no sodium. Drinking water contains sodium but in varying amounts. “Softened” water has a much higher sodium content than “hard,” or unsoftened, water.

Requirements.The DRI for sodium has been established at 1,500 mg,or 3,800 mg of salt. The UL for salt is 5,800 mg, with the majority of men and women exceeding that limit.

Deficiency or Excess.Either deficiency or excess of sodium can causeupsets in the body’s fluid balance. Although rare, a deficiency of sodium can occur after severe vomiting, diarrhea, or heavy perspiration. In such cases, dehydration can result. A sodium deficiency also can upset the acid-base bal-ance in the body. Cells function best in a neutral or slightly alkaline medium. If too much acid is lost (which can happen during severe vomiting), tetany due to alkalosis may develop. If the alkaline reserve is deficient as a result of starvation or faulty metabolism, as in the case of diabetes, acidosis (too much acid) may develop.

An excess of sodium is a more common problem and may cause edema. This edema adds pressure to artery walls that can cause hypertension. Thus, an excess of sodium is frequently associated with cardiovascular conditions such as hypertension and congestive heart failure. Certain groups have greater (or lesser) reduction in blood pressure in response to reduced sodium intake. Those with the greatest reductions in blood pressure have been termed saltsensitive, whereas those with little or no reduction in blood pressure have beentermed salt resistant. Working with your cardiologist is the best way to deter-mine which you are, sensitive or resistant. Depending on the diagnosis, the diet order may be either a 3- to 4-gram (also called no-added salt, or NAS) or a 1- to 2-gram sodium-restricted diet. A physician rarely prescribes a diet of 1 gram of sodium because compliance is difficult.