Sodium (symbol= Na+, latin for 'Natrium')-A soft, silver-white alkaline metallic element. Sodium is the primary cation (positiv ion, as compared with negative ions or anions, such as chlorine) of extracellular (outside or external to the cell) fluids.
uses of sodium
Sodium is essential in the diet, as will be discussed. Salts of sodium are widely used in medicine, the food industry, cosmetics, and for many other purposes.
Sodium acetate, the acetic acid (vinegar) combination with elemental sodium, is used as a source of sodium ions (positively or negatively charged atoms) in solutions for haemodialysis (hemodialysis, US spelling) and peritoneal dialysis. It is also used as a urinary alkalizer, diuretic and expectorant. Sodium alginate, is a carbohydrate of seaweed containing sodium, and is used as a thickening agent and suspending agent in foods and cosmetics. But of course, these products are combined with elemental sodium.
Sodium on its own is essential in the diet for many reasons. Sodium along with potassium and chloride function together in maintaining pH (acid-alkaline conditions) and in regulating osmolarity of intracellular (inside the cell) and extracellular (outside the cell) fluid. Sodium is involved in transmission of nerve impulses, and helps to maintain blood volume, and fluid voiume in other fluid compartments (see water).
DID YOU KNOW?
Sodium is exreted by the kidneys through the formation of urine. We also lose sodium through sweat. Relocating to a warmer climate causes an individual to lose more sodium through the sweat glands than he or she lost in the colder environment. If individuals relocating to warmer environments participate in intense physoical activity, large amounts of sodium (and water) are lost through the sweat glands, resulting in dehydration, and/or health risks. However, if we allow our body to acclimatise to the warmer environment over the period of a few weeks, we will not lose as much sodium and water through sweat. Why is this?
The average individual can lose anywhere from 500-700ml of sweat each hour, in warmer climates and through exercise. Sweating (losing water and salts) is beneficial because the water in sweat becomes warm and ecaporates from the skin removing excess body heat, and thus keeping body temperatures within safe limits. As a person remains in warmer climates, they begin to sweat more profusely, sweating up to 2 litres each hour! This means that an indiviudal can lose up to 30 grams (1 ounce) of salt per day ! OF course, this does not benefit the body, as we can see that we need salt (sodium and chloride) to live. Therefore, the body attempts to rectify salt loss by increasing the production of a hormone called aldosterone. ALdonsterone is a steroid hormone produced by adrenal glands, a pair of glands which are positioned above the kidneys. When salt concentration becomes low, the body can detect these changes in concentration. As a result, several chemical messengers are produced in different areas of the body. These chemical messengers have a direct and indirect effect on the adrenal gland. Upon stimulation, the adrenal gland is prompted to produce and secrete aldosterone. One of the functions of aldosterone is to decreasethe amount of salt (and thus water) lost in sweat. Thus, this feedback control mechanism is but one of the many wonderful biological control sweithces to help the human survive (see homeostasis. This information can benefit anyone travelling to a warmer climate, especially those who plan to participate in mountaineering, hiking, trekking, or any other strenuous activity, because by allowing the body to acclimatise for a period of several weeks, this allows the aldosterone effect to occur and decrease the amount of salt and water loss from the body. This is important not only for peak performance during sporting events, but more importnntly for maintainence of health. As we will learn, there is also a danger to potassium levels as well in regards to prolonged heat exposure.
RDA of sodium
An established RDA of sodium has not been reached yet. Of course, this is a touchy area anyway, considering the relation to sodium and hypertension (higher than the normal average blood pressure). Additionally, western diets supply more than adequate amounts of sodium, on occasion, supplying excessive amounts. For example, average American diets deliver approximately 12 grams of salt per day (8 grams in food and 4 grams added).
Toxicity of sodium
Excessive amounts of salt temporarily raise the blood pressure (the pressure of blood against the blood vessel walls). This, of course, is a concern, considering that increased blood pressure against the walls of blood vessels can damage them. Additionally, the wall can rupture, leading to haemorrhage, or stroke. Sodium raises blood pressure by attracting water into the blood, and therefore, increasing blood volume. If there is a higher blood volume in the compartment of blood vessels, this will lead to a higher pressure to accomodate the excess fluid portion of the blood.