How the human body handles salt
Salt provides two elements that are essential for life and for good health - sodium and chloride ions. They are both elements that the body cannot manufacture itself so it must be supplied by food. Although salt is the most common dietary source for these essential elements, sodium also available from various foods that contain sodium naturally. Sodium is a mineral element that plays a critical role in body physiology. It controls the volume of fluid in the body and helps maintain the acid-base level. About 40% of the body's sodium is contained in bone, some is found within other organs and cells and the remaining 55% is in blood plasma and extracellular fluids. Sodium is important in proper nerve conduction, in aiding the passage of various nutrients into cells, and in the maintenance of blood pressure.
Chloride ions also helps maintain proper blood volume, blood pressure, and pH of body fluids. Chloride is the major extracellular anion and contributes to many body functions including the maintenance of blood pressure, acid-base balance, muscular activity, and the movement of water between fluid compartments. Chloride ions are secreted in the gastric juice as hydrochloric acid, which is the naturally-produced acid that is essential for the digestion of food.
One of salt's major functions is to regulate blood volume and pressure including the flexibility of the blood vessels. When the heart contracts, it forces blood through the arteries of the circulatory system; the pressure required to pump this blood is called "systolic," the "top" number of a blood pressure reading. Between heartbeats, the heart relaxes and the pressure maintained is called "diastolic," the "bottom" number. When the blood volume increases or the blood vessel walls don't expand enough, blood pressure increases. Normal blood pressure is less than 130/85 mm Hg according to the National Heart, Lung and Blood Institute. In any given population, blood pressures are considered to be a realatively good indicator of the incidence of cardiovascular events like heart attacks and strokes.
Blood pressure can be affected by many things. Above all else is the genetic predisposition to high blood pressure, just like there are certain groups that have a genetic predisposition to low blood pressure. Blood pressure can be effected by stress, age, exercise and diet. People who consume a Mediterranean-type diet, with lots of fruits, vegetables and low-fat dairy products are the least susceptible to high blood pressure. For certain individuals who are salt sensitive, excessive consumption of sodium can increase blood pressure. This tendency can be minimized by eating a balanced Mediterranean-type diet. In an average populations consuming and American-type diet, when salt intakes are reduced, about 30% will experience a drop in blood pressure between 1 and 4 mm Hg while about 20% will experience a similar increase in blood pressure. The remaining 50% of the population will show no effect at all of salt intake reduction. Nevertheless, the entire debate on salt and health has almost exclusively focused on the issue of blood pressure, with little regard to any other risk factors or biomarkers resulting from a variation in salt intake.
Sodium and chloride ions play an important role in the firing of the nervous system neurons. Changes in the concentrations of sodium and chloride ions cause an action potential to fire, allowing a neuron to send a signal to other cells which it's connected to. This results in sending the proper signals throughout her body to elicit all of our reactions physiological including mechanical movement of muscles. Changing the consumption of salt has a minimal impact on the nervous system. Only at extreme levels of sodium deficiency will responses in the nervous system be noticed.
Metabolism (digestive system)
Almost all the salt taken in with food or beverages is quickly absorbed from the small intestine and rapidly finds its way to the circulatory system and the extracellular space of tissues. During rapid growth, a considerable amount of sodium is taken up by the skeletal system and other tissues. After maturity, in a healthy person, all salt was taken in, regardless of quantity, is compensated for by the daily elimination of the same quantity through our normal excretory channels. In fact, our kidneys are capable of filtering an incredibly large quantity of sodium on a daily basis (the daily equivalent of 6 pounds of salt).
Role of hormones in sodium regulation
Steroid hormones, secreted by the adrenal cortex regulate the balance of water and electrolytes in the body. Working at the distal tubule and collecting ducts of the kidney, aldosterone increases the permeability of their inner membranes to sodium and potassium and is responsible for reabsorbing sodium (Na+) ions and water from the urine back into the blood, while secreting potassium (K+) ions into the urine. Aldosterone is responsible for the reabsorption of virtually all the sodium content in human blood under normal kidney filtration function. Aldosterone also acts on specific receptors in the brain to conserve water and salt by controlling renal tubular resorption.