Encyclopedia
- For sour salt, see calcium citrate or citric acid.
Edible salt, also called
table salt or just
salt, is a
mineral, one of a very few rocks commonly eaten by
humans. There are different forms of edible salt: unrefined salt, refined salt, table salt or iodised salt. It is a crystalline solid, white, pale pink or light grey in colour, obtained from
sea water or from rock deposits.
Sea salt comes in fine or larger crystals. In nature, it includes not only
sodium chloride, but also other vital trace minerals. Edible rock salts may be slightly greyish in colour due to this mineral content.
Salt is necessary for the survival of all living creatures, including humans. Salt is involved in regulating the water content of the body. Salt flavour is one of the basic tastes. Salt cravings may be caused by trace mineral deficiencies as well as by a deficiency of sodium chloride itself.
Salt is required for life, but overconsumption can increase the risk of health problems, including high blood pressure, in those individuals who are genetically predisposed to hypertension. In food preparation, salt is used as a preservative and as a seasoning.
History of edible salt
Salt's preservative ability was a foundation of
civilization. It eliminated dependency on the seasonal availability of food, allowed travel over long distances, and was a vital food additive. However, because salt was difficult to obtain, it became a highly valued trade item throughout history. Until the
1900s, salt was one of the prime movers of national economies and wars. Salt was often
taxed; research has discovered this practice to have existed as early as the 20th century BC in China.
In the empire of
Mali, merchants in 12th century
Timbuktu—the gateway to the
Sahara Desert and the seat of scholars—valued salt enough to buy it for its weight in
gold; this trade led to the legends of the incredibly wealthy city of Timbuktu, and fueled inflation in
Europe, which was exporting the salt.
Forms of edible salt
Unrefined salt
Different natural salts have different mineralities, giving each one a unique flavor.
Fleur de sel, natural sea salt harvested by hand, has a unique flavor varying from region to region.
Some assert that unrefined sea salt is more healthy than refined salts. There are concerns, however, that raw sea or rock salts may not contain sufficient iodine salts to prevent iodine deficiency diseases like goitre.
Refined salt
Refined salt, that is most widely used presently, is mainly sodium chloride. Only about 7% of refined salt is used as a food additive. The majority is sold for industrial use, from manufacturing pulp and paper to setting dyes in textiles and fabric, to producing soaps and detergents, and has great commercial value.
The manufacture and use of salt is one of the oldest chemical industries. Salt is also obtained by evaporation of
sea water, usually in shallow basins warmed by
sunlight; salt so obtained was formerly called bay salt, and is now often called sea salt or solar salt. Today, most refined salt is prepared from rock salt: mineral deposits high in edible salt. These rock salt deposits were formed by the evaporation of ancient salt lakes. These deposits may be
mined conventionally or through the injection of water. Injected water dissolves the salt, and the brine solution can be pumped to the surface where the salt is collected.
After the raw salt is obtained, it is refined to purify it and improve its storage and handling characteristics. Purification usually involves recrystallization. In recrystallization, a brine solution is treated with chemicals that precipitate most impurities . Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are
kiln-dried.
Anticaking agents are generally added at this point. These agents are hygroscopic chemicals which absorb
humidity, keeping the salt crystals from sticking together. Some anticaking agents used are tricalcium phosphate,
calcium or
magnesium carbonates,
fatty acid salts ,
magnesium oxide, silicon dioxide, sodium alumino-silicate, and alumino-calcium silicate. Concerns have been raised regarding the possible toxic effects of
aluminium in the latter two compounds, however both the European Union and the United States
Food and Drug Administration permit their use in regulated quantities. The refined salt is then ready for packing and distribution.
Table salt
Table salt is refined salt, nearly pure sodium chloride. It usually contains substances that make it free flowing such as sodium silicoaluminate , as well as a minute amount of invert sugar to prevent the salt from turning a yellow colour when exposed to sunlight, and to prevent a significant loss of iodine via vaporization. It is common practice to put a few grains of uncooked
rice in salt shakers to absorb extra moisture when anticaking agents are not enough. Table salt is also often iodised—a small amount of
potassium iodide is added as an important dietary supplement. Table salt is mainly employed in cooking and as a table condiment. Iodised table salt has significantly reduced disorders of iodine deficiency in countries where it is used. Iodine is important to prevent the insufficient production of thyroid hormones , which can cause goitre, cretinism in children, and myxedema in adults.
Table salt is now used all over the world.
Health effects
Sodium is one of the primary electrolytes in the body. All three electrolytes are available in unrefined salt, as are other vital minerals needed for optimal bodily function. Too much or too little salt in the diet can lead to muscle cramps, dizziness, or even an electrolyte disturbance, which can cause severe, even fatal, neurological problems. Drinking too much water, with insufficient salt intake, puts a person at risk of water intoxication. Salt is even sometimes used as a health aid, such as in treatment of dysautonomia.
People's risk for disease due to salt intake that is too low or too high varies, due to biochemical individuality. In fact, some have asserted that while the risks of consuming too much salt are real, the risks have been dramatically overhyped for most people, or that the studies done on the consumption of edible salt can be interpeted in many different ways.
Nevertheless, salt has been studied extensively by researchers and many of them believe that salt can be consumed in excess and can therefore lead to health problems.
For example, salt consumption has been linked to exercise-induced
asthma. On the other hand, another source counters, "…we still don't know whether salt contributes to asthma. If there is a link then it's very weak…". Excessive salt intake may also trigger heartburn. The role of salt in the causation or exacerbation of osteoporosis is similarly plausible. One report shows that a high salt diet does reduce bone density in girls.. Yet "While high salt intakes have been associated with detrimental effects on bone health, there are insufficient data to draw firm conclusions." Gastric cancer is associated with high levels of sodium, "but the evidence does not generally relate to foods typically consumed in the UK."
Studies have clearly shown a link between an overabundance of salt in the diet and hypertension . "Since 1994, the evidence of an association between dietary salt intakes and blood pressure has increased. The data have been consistent in various study populations and across the age range in adults." . "The CMO [Chief Medical Officer] of England, in his Annual Report , highlighted that people with high blood pressure are three times more likely to develop heart disease and stroke, and twice as likely to die from these diseases than those with normal levels.". Professor Dr. Diederick Grobbee claims that there is no evidence of a causal link between salt intake and mortality or cardiovascular events.. One study found that low urinary sodium is associated with greater risk of myocardial infarction among treated hypertensive men . Additionally, in a study of left ventricular hypertrophy , "Evidence suggests that high salt intake causes left ventricular hypertrophy, a strong risk factor for cardiovascular disease, independently of blood pressure effects." "…there is accumulating evidence that high salt intake predicts left ventricular hypertrophy." Excessive salt intake, combined with an inadequate intake of water, can cause hypernatremia. It can exacerbate
renal disease.
Australia: The recommended dietary intake is 0.92g–2.3g sodium per day
USA: The Food and Drug Administration itself does not make a recommendation but refers readers to
Dietary Guidelines for Americans 2005. These suggest that US citizens should consume less than 2,300 mg of sodium per day.
Labeling
The FDA
Food Labeling Guide stipulates whether a food can be labelled as "free", "low", or "reduced/less" in respect of sodium. A food that exceeds 480mg of sodium per 'serving' must have a disclosure statement.
Campaigns
In 2004, the
British Food Standards Agency started a public health campaign called "Salt - Watch it", which recommends no more than 6g of salt per day; it features a character called
Sid the Slug and was criticised by the Salt Manufacturers Association . The
Advertising Standards Authority did not uphold the SMA complaint in its adjudication..
Salt substitutes
Salt intake can be reduced quite easily by simply reducing salty foods in one's diet. Salt substitutes have a taste similar to table salt and contain mostly
potassium chloride, which will increase
potassium intake. Because excess potassium intake can cause potentially fatal hyperkalemia, it is advisable to check with one's physician and pharmacist before using salt substitutes. Various diseases and
medications may decrease the body's excretion of potassium, thereby increasing the risk of hyperkalemia. If you have kidney failure, heart failure or have diabetes, you should not use a low salt variety without medical advice. A manufacturer, LoSalt, has issued an advisory statement. that people taking the following prescription drugs should not use a salt substitute:
Amiloride,
Triamterene, Dytac,
Spironolactone,
Aldactone, Eplerenone, and Inspra.
See also
References
External links
Salt and health
Government bodiesMany other government bodies are listed in the References section above.
- Ireland: Food Safety Authority of Ireland
- UK: Food Standards Agency
- UK: Scientific Advisory Committee on Nutrition and
Medical authorities- The Cochrane Collaboration
Charities and campaigns- British Nutrition Foundation article
-
- CSPI page
- Irish Heart Foundation booklet
Journalism- BBC article
- BBC medical notes
- Guardian article
Salt industry- EuSalt
-
- Salt Manufacturers' Association
- Salt Institute
Chemical dataFurther reading
- Mark Kurlansky, Salt : A World History, Penguin Books
- Department of Health, Dietary Reference Values for Food Energy and Nutrients for the UK: Report of the Panel on DRVs of the Committee on the Medical Aspects of Food Policy , The Stationery Office
