People have held salt in high regard throughout the recorded history. The sodium mineral is found in all body fluids. The adult human body contains about 100 gram of sodium ions. It is present in salts and people find its taste immensely appealing. Sodium is the main cation outside the ceils and one of the electrolyte primarily responsible for maintaining fluid balance It is lost from the body through urine and sweat; the sodium which is passed out of urine is regulated by the kidney but that which is lost by sweating is not controlled.
It is present in table salt, soy sauce, moderate amounts in meat, milk, breads, vegetables, cornflakes, salted peanuts and in large amount in processed foods. It is normally added to food during cooking as sodium chloride.
Adult requirement of sodium is about 10-15 g.
- It is the principle cation of the extracellular fluid and the primary regulator of its volume. People who do hard work or strenuous exercises need more sodium.
- It helps maintain acid base balance.
- It is essential for nerve transmission and muscle contraction.
- It maintains electrolyte balance as well.
Foods usually provide more sodium than the body needs. It is readily absorbed by the intestinal tract and travels freely in the blood until it reaches the kidney, which filters all the sodium out of the body.
When blood sodium rises as when a person take too much salt in its food, it enter the body and captures water resulting cell dehydration which evoke thirst and the person drinks water until appropriate sodium to water ratio is restored.
If blood sodium drops as may occur in vomiting, diarrhea, or heavy sweating both sodium and water must be replenished. Under normal condition of sweating due to exercise, salt loses can easily be replaced later in the day with ordinary food. It can lead to low blood volume and low cardiac output therefore low BP.
During intense activities, such as ultra-endurance events, persons can loses much sodium and drink so much water that they develop hyponatremia which means very little sodium in the blood. Beverages with sodium and glucose and salty foods will help restore sodium balance.
Depletion of sodium may lead to muscular cramps, mental apathy and loss of appetite.
The immediate symptoms of acute sodium toxicity are edema and hypertension, but such toxicity poses no problem as long as water needs are met. Prolonged excessive sodium intake may contribute to hypertension in some people.
For years, a high sodium intake was considered the primary factor responsible for high blood pressure. Then research pointed to salt as the dietary culprit. Salt has greater effect on blood pressure than either sodium or chloride or in combination with other ions. Consequently health recommendation advises limiting daily salt intake to less than 6 grams.
A high sodium intake has also been associated with calcium excretion and bone losses. Dietary advice to prevent osteoporosis might suggest eating more calcium rich foods while eating fewer foods high in sodium.