Keywords: electrolyte, water balance
- Acid-alkaline balance
- Assimilation of amino acids and glucose into body cells
- Energy production
- Normal water balance and blood volume
- Muscle contraction
- Nerve impulse transmission
The human sodium requirement is probably about 500 mg per day (representing about 1.3 grams of salt) although most individuals consume far more than this. Apart from salt and highly-salted foods such as smoked fish, ham, bacon and other preserved or processed meats, salted butter, salted nuts and packet snacks, other common sources of sodium include monosodium glutamate and other sodium-based food additives, baking powder, and sodium bicarbonate antacid medications. Salt itself is 40 per cent sodium and 60 per cent chloride.
Whereas potassium is mainly found inside the cells, sodium is found outside the cells, in the extracellular fluid. Large amounts are also found in bone, bile and pancreatic juice. There is no control of sodium absorption as with other minerals—the excessive dietary intakes which are so common in the developed world are readily absorbed.
This is rare in the Western world, although heavy exercise in a hot climate, causing prolonged sweating, may lead to sodium depletion. An insufficiency of the adrenal cortex gland, or prolonged vomiting or diarrhoea, kidney disease (as in renal failure), or long-term very low-sodium diets may produce a sodium deficiency, leading to weakness, lassitude, anorexia and vomiting, mental confusion, cramps and aching muscles.
Addison’s disease involves a loss of adrenal function and aldosterone production, thus causing sodium deficiency by impairing the kidney’s ability to reabsorb sodium.
Cushing’s disease on the other hand involves the production of excessive amounts of hormones by the adrenal cortex, which results in sodium retention.
Sodium and water balance
As the blood sodium levels rise the thirst receptors in the hypothalamus stimulate the thirst sensation, and the extra water is retained to keep the sodium diluted. At the same time the kidney will begin reabsorbing less sodium, thus allowing more sodium to be excreted in the urine. Aldosterone, a hormone secreted by the adrenal cortex, controls the rate of excretion of sodium in the urine, and vasopressin (also known as anti-diuretic hormone or ADH) produced by the pituitary, controls the rate of fluid excretion by the kidneys. Normal kidneys have no difficulty in excreting excess sodium as long as there is sufficient water to allow this.
Low-sodium diets are frequently prescribed to control the excessive retention of body water, especially in individuals with high blood pressure resulting from this excess fluid.
Information compiled by Linda Lazarides
Naturopathic Nutritionist, Author, Educator