Salt has a great effect on the body's physiology and is an absolutely essential mineral to maintain life. It is so essential that the body has special mechanisms at the most basic cellular level to insure it is kept in balance with other chemicals. The kidneys make sure that the salt supply throughout the body is maintained at a constant level.
Explaining Salt
Chemically there are many kinds of salts. Using the term "salt" in diet and nutrition usually refers to common table salt or sodium chloride. When salt enters the body or is placed in water it dissolves into its component elements of sodium and chloride. These become electrolytes, which means they each have an electrical charge. Their charge enables them to carry electrical currents in and around cells. Without this physical property of electrolytes, no cell in the body would be able to function.
Function of the Kidneys
The kidneys are organs with a number of functions, one of which is to filter waste from the blood. This function is related to their role in maintaining a balance between electrolytes in the blood. Sodium, potassium and chloride, for example are electrolytes the kidneys regulate with particularly tight control. This is because a steady balance of these electrolytes is required for all physiological functions including water balance and electrical communication between cells.
Physiology of Salt
The balance of electrolytes is tightly controlled because the relative proportion of each electrolyte represents the basis for almost every cell process. Disturbance in that balance can have serious consequences. Hypernatremia, or increased sodium in the blood, results when the kidneys do not excrete sodium effectively. Conversely, hyponatremia occurs when the kidneys excrete too much sodium, leaving less in the blood. Various conditions can produce these effects. For example, hyponatremia can occur if you drink too much water too quickly, essentially diluting the sodium in the blood. Hypernatremia, on the other hand, can occur if you have diarrhea or vomit excessively, essentially removing water from the blood and concentrating the sodium.
Regulation
During hyponatremia, the kidneys try to retain sodium. If they cannot, the results can be fatigue, headache, weakness and nausea. Many times, you can reverse hyponatremia by simply eating salt to bring serum sodium levels back to normal. During hypernatremia the opposite effect occurs and the kidneys try to get rid of excess serum sodium. Hypernatremia's symptoms are like those of hyponatremia. Treating hypernatremia can be as simple as drinking water in order to dilute the sodium in the blood. Generally speaking, most people get enough sodium and other electrolytes from a normal diet.
