Salt is one of the best-known and most important substances ingested by the human body. Essential systems regarding the hydration of the body, the maintenance of the acid/base balance essential to human survival, and production of muscular energy cannot occur without the consumption of dietary salt and its regulated presence in every cell.
Salt, often described as table salt given its widespread use as a condiment, is the chemical compound created by the union of two elements, sodium, a metal, and chlorine. Their product, sodium chloride, is expressed as the chemical formula NaCl. While in popular speech salt is commonly used in an interchangeable fashion in description of sodium's characteristics, sodium represents only 40% of the composition of table salt by weight. Salt is a mineral, a substance that is mined underground in various parts of the world; salt is also easily extracted from seawater. The term salt is used to describe both the sodium chloride compound as well as the more generic class of metals that are capable of replacing an existing hydrogen atom in an acid. Potassium, calcium, and magnesium are classified as salts in this respect.
Salt is the most common flavoring added to food in the world. Salt has been used as a food preservative for thousands of years, and it is today employed, either in its common form or in a similar chemistry such as monosodium glutamate (MSG), in thousands of food preparation processes. Sodium nitrate, a preservative, and sodium bicarbonate, used in food preparation, are also common sources of sodium in compounds similar to salt. Salt that is sold commercially as a flavoring or condiment is usually distributed with iodine added; iodine is an essential element to human function that assists in the prevention of various thyroid gland conditions, including goiter, a pronounced enlargement of the gland which can restrict its operation, leading to an impairment of the regulation of the body's entire metabolic function.
Throughout the industrialized world, salt is consumed through food in amounts far in excess of the body's actual requirements for either sodium or chlorine. In the United States, the recommended daily allowance (RDA) of sodium for an adult is between 1,100 to 3,300 mg per day; the average American adult consumes between 4,000 and 5,000 mg of sodium. Many foods have salt or sodium in their composition, including all milk products, green vegetables such as celery, root vegetables such as beets, and others. Salt is commonly added to meats and all manner of prepackaged or processed food products. Paradoxically, no matter what amount of salt is ingested by the body through regular diet, additional salt is essential to athletic performance, and most sports drinks and other nutritional supplements will have salt or simple sodium added.
Sodium and chlorine play distinct roles in effective human function. Each element is absorbed into the body through the digestive processes of the small intestine, where the elements are broken into their single elemental forms. The key processes to which sodium is directed from the point of absorption into the body include water (fluid) balance within the body; acid/base balance in the body, known as the pH level; the specific relationship between sodium and the element potassium creates what is often referred to as a potassium/sodium "pump," a fluid pressure system essential to the generation of energy within each cell; and a related role in the effective transmission of impulses through out the central nervous and peripheral nervous systems.
The most common negative impact of excessive salt consumption is the generation of excessive levels of sodium within the body. Excess sodium is a negative impact on the rather delicate fluid balance levels within the body, the most direct effect of which is hypertension, or high blood pressure. Hypertension is a critical factor in reduced cardiovascular health, including significantly increased risk of stroke and other forms of system failure.
Conversely, an overly restricted dietary salt consumption can lead to the relatively common condition experienced by endurance athletes, hyponatremia, a disruption of the sodium balance that interferes with the body's ability to regulate fluid levels under the stresses imposed by endurance sport.
Chlorine is not given any where near the critical scrutiny of that afforded excess sodium consumption. Chlorine comprises only 0.15% of the body weight of an adult person, and it is stored by the body almost entirely within the intracellular fluids. Chlorine is also important to the body's ability to regulate the acid/base balance. Chlorine is important to the body's ability to absorb potassium, as well as being a part of the function performed by the blood in transporting waste carbon dioxide from the tissues to the lungs to be exhaled. Chlorine is essential to the digestive process, in that chlorine joins with hydrogen to form hydrogen chloride, the major component of stomach bile.
Unlike sodium, excess chlorine is not believed to present any significant problems to overall body function.