Salt

Salt is mostly sodium chloride (NaCl). This salt shaker also contains grains of rice, which some use to prevent caking.

Brine being boiled down to pure salt in Zigong, PRC

Salt is a dietary mineral composed primarily of sodium chloride that is essential for animal life, but toxic to most land plants. Salt flavor is one of the basic tastes, and salt is the most popular food seasoning. Salt is also an important preservative.

Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodized salt. It is a crystalline solid, white, pale pink or light gray in color, normally obtained from sea water or rock deposits. Edible rock salts may be slightly grayish in color because of this mineral content.

Chloride and sodium ions, the two major components of salt, are necessary for the survival of all known living creatures, including humans. Salt is involved in regulating the water content (fluid balance) of the body. Salt cravings may be caused by trace mineral deficiencies as well as by a deficiency of sodium chloride itself. Conversely, overconsumption of salt increases the risk of health problems, including high blood pressure.

History

Main article: History of salt

Human beings have used canning and artificial refrigeration for the preservation of food for approximately the last two hundred years, however, in the millennia before then, salt provided the best-known food preservative, especially for meat.^[1] The harvest of salt from the surface of the salt lake Yuncheng in Shanxi, China dates back to at least 6000 BC, making it one of the oldest verifiable saltworks.^[2]:18–19

Salt was included among funereal offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds and salt fish.^[2]:38 From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon Cedar, glass, and the dye Tyrian purple; the Phoenicians traded Egyptian salt fish and salt from North Africa throughout their Mediterranean trade empire.^[2]:44

Along the Sahara, the Tuareg maintain routes especially for the transport of salt by Azalai (salt caravans). In 1960, the caravans still transported some 15,000 tons of salt, but this trade has now declined to roughly a third of this figure.^[3]

Salzburg, Hallstatt, and Hallein lie on the river Salzach in central Austria, within a radius of no more than 17 kilometres. Salzach literally means "salt water" and Salzburg "salt city", both taking their names from the Germanic root for salt, salz. Hallstatt literally means "salt town" and Hallein "saltwork", taking their names from hal(l)-, a root for salt found in Celtic, Greek, and Egyptian. The root hal(l)- also gave us Gaul, the Roman exonym for the Celts, Halle and Schwäbisch Hall in Germany, Halych in Ukraine, and Galicia in Spain: this list of places named for Celtic saltworks is far from complete.^[4][5][6]

Hallstatt gave its name to the Celtic archaeological culture that began mining for salt in the area in around 800 BC Around 400 BC, the Hallstatt Celts, who had heretofore mined for salt, began open pan salt making. During the first millennium BC, Celtic communities grew rich trading salt and salted meat to Ancient Greece and Ancient Rome in exchange for wine and other luxuries.^[1]

At times, troops in the Roman army were paid in salt and this is the origin of the words salary and, by way of French, soldier.^[2]:63 The word salad literally means "salted," and comes from the ancient Roman practice of salting leaf vegetables.^[2]:64

In the history of Indian Independence, Mahatma Gandhi took a long parade called "Dandi March" or "Salt SathyaGraha" against taxes levied by the then British rulers, for the export of salt, as this would affect the poor "salt-makers". The significance of this announced "March" is that Gandhi never told about his "way" and "destination" till the last moment, and it was a very great success in bringing millions of people together as one.

In religion

According to Strong's Concordance, there are forty-one verses which reference salt in the English translation of the King James Bible, the earliest being the story of Lot's wife, who was turned into a pillar of salt when she disobediently looked back at the wicked cities of Sodom (Genesis 19:26). When King Abimelech destroyed the city of Shechem he is said to have "sowed salt on it;" a phrase expressing the completeness of its ruin. (Judges 9:45.) In the Sermon on the Mount, Jesus referred to his followers as the "salt of the earth". The apostle Paul also encouraged Christians to "let your conversation be always full of grace, seasoned with salt" (Colossians 4:6).

Salt is mandatory in the rite of the Tridentine Mass.^[7] Salt is used in the third item (which includes an Exorcism) of the Celtic Consecration (cf. Gallican rite) that is employed in the consecration of a church. Salt may be added to the water "where it is customary" in the Roman Catholic rite of Holy water.

Salt is considered to be a very auspicious substance in Hindu mythology, and is used in particular religious ceremonies like housewarmings and weddings.

In many Pagan religions esp. Wicca salt is symbolic of the element Earth. It is also used as a purifier of sacred space.

In the native Japanese religion Shinto, salt is used for ritual purification of locations and people, such as in Sumo Wrestling.

In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water.

Forms of salt

Unrefined salt

Main articles: Sea salt, Halite, and Fleur de sel

A commercial pack of sea 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 advocates for sea salt assert that unrefined sea salt is healthier than refined salts.^[8] However, completely raw sea salt is bitter because of magnesium and calcium compounds, and thus is rarely eaten. The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough iodine salts to prevent iodine deficiency diseases.^[9]

Unrefined sea salts are also commonly used as ingredients in bathing additives and cosmetic products. One example are bath salts, which uses sea salt as its main ingredient and combined with other ingredients used for its healing and therapeutic effects.

Refined salt

Salt mounds in Bolivia.

Refined salt, which is most widely used presently, is mainly sodium chloride. Food grade salt accounts for only a small part of salt production in industrialised countries (3% in Europe^[10]) although worldwide, food uses account for 17.5% of salt production^[11]. The majority is sold for industrial use. Salt has great commercial value because it is a necessary ingredient in the manufacturing of many things. A few common examples include: the production of pulp and paper, setting dyes in textiles and fabrics, and the making of soaps and detergents.

The manufacture and use of salt is one of the oldest chemical industries.^[12] Salt is also obtained by evaporation of sea water, usually in shallow basins warmed by sunlight;^[13] 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 salt. These rock salt deposits were formed by the evaporation of ancient salt lakes,^[14] and 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 (largely magnesium and calcium salts).^[15] Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are kiln-dried.

Salt Crystals at Devil's Golf Course in Death Valley National Park.

Single-serving salt packets.

Since the 1950s it has been common to add a trace of sodium ferrocyanide to the brine; this acts as an anticaking agent by promoting irregular crystals.^[16] Other anticaking agents (and potassium iodide, for iodised salt) are generally added after crystallization. These agents are hygroscopic chemicals which absorb humidity, keeping the salt crystals from sticking together. Some anti-caking agents used are tricalcium phosphate, calcium or magnesium carbonates, fatty acid salts (acid salts), magnesium oxide, silicon dioxide, calcium silicate, sodium aluminosilicate, and calcium aluminosilicate. 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 (FDA) permit their use.^[17] The refined salt is then ready for packing and distribution.

Table salt

Table salt is refined salt, 99% sodium chloride.^[18][19] It usually contains substances that make it free-flowing (anti-caking agents) such as sodium silicoaluminate or magnesium carbonate. It is common practice to put a few grains of uncooked rice^[20] or half a dry cracker (such as Saltine) in salt shakers to absorb extra moisture and help break of clumps when anti-caking agents are not enough. Table salt has a particle density of 2.165 g/cm³, and a bulk density (dry, ASTM D 632 gradation) of about 1.154 g/cm³.^[21]

Salty condiments

In many East Asian cultures, salt is not traditionally used as a condiment.^[22] However, condiments such as soy sauce, fish sauce and oyster sauce tend to have a high salt content and fill much the same role as a salt-providing table condiment that table salt serves in western cultures.

Additives

See also: Iodised salt

Iodized salt (BrE: iodised salt) is table salt mixed with a minute amount of potassium iodide, sodium iodide, or iodate. Iodized salt is used to help reduce the incidence of iodine deficiency in humans. Iodine deficiency commonly leads to thyroid gland problems, specifically endemic goiter, a disease characterized by a swelling of the thyroid gland, usually resulting in a bulbous protrusion on the neck. While only tiny quantities of iodine are required in the diet to prevent goiter, the United States Food and Drug Administration recommends (21 CFR 101.9 (c)(8)(iv)) 150 micrograms of iodine per day for both men and women. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used.^[23] Iodine is important to prevent the insufficient production of thyroid hormones (hypothyroidism), which can cause goitre, cretinism in children, and myxedema in adults.

Table salt is mainly employed in cooking and as a table condiment. The amount of iodine and the specific iodine compound added to salt varies from country to country. In the United States, iodized salt contains 46-77 ppm, while in the UK the iodine content of iodized salt is recommended to be 10-22 ppm.^[24] Today, iodized salt is more common in the United States, Australia and New Zealand than in the United Kingdom.

In some European countries where drinking water fluoridation is not practiced, fluorinated table salt is available. In France, 35% of sold table salt contains either sodium fluoride or potassium fluoride.^[25] Another additive, especially important for pregnant women, is Folic acid (Vitamin B9), which gives the table salt a yellow color.

In Canada, at least one brand (Windsor salt) contains invert sugar. The reason for this is unclear.

Health effects

Sodium is one of the primary electrolytes in the body. All four cationic electrolytes (sodium, potassium, magnesium, and calcium) 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.^[26] Drinking too much water, with insufficient salt intake, puts a person at risk of water intoxication (hyponatremia). Salt is even sometimes used as a health aid, such as in treatment of dysautonomia.^[27]

The risk for disease due to insufficient or excessive salt intake varies because of biochemical individuality. Some have asserted that while the risks of consuming too much salt are real, the risks have been exaggerated for most people, or that the studies done on the consumption of salt can be interpreted in many different ways.^{[28] [29]}

Excess salt consumption has been linked to:

• exercise-induced asthma.^[30]
• heartburn^[31].
• osteoporosis: One report shows that a high salt diet does reduce bone density in women.^[32]. Yet "While high salt intakes have been associated with detrimental effects on bone health, there are insufficient data to draw firm conclusions." (^[33], p3)
• Gastric cancer (Stomach cancer) is associated with high levels of sodium, "but the evidence does not generally relate to foods typically consumed in the UK." (^[33], p18) However, in Japan, salt consumption is higher.^[34]
• hypertension (high blood pressure): "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." (^[33] p3). A large scale study from 2007 has shown that people with high-normal blood pressure who significantly reduced the amount of salt in their diet decreased their chances of developing cardiovascular disease by 25% over the following 10 to 15 years. Their risk of dying from cardiovascular disease decreased by 20%.^[35]
• left ventricular hypertrophy (cardiac enlargement): "Evidence suggests that high salt intake causes left ventricular hypertrophy, a strong risk factor for cardiovascular disease, independently of blood pressure effects." (^[33] p3) "…there is accumulating evidence that high salt intake predicts left ventricular hypertrophy." (^[36], p12) Excessive salt (sodium) intake, combined with an inadequate intake of water, can cause hypernatremia. It can exacerbate renal disease.^[26]
• edema (BE: oedema): A decrease in salt intake has been suggested to treat edema (fluid retention).^[37][26]
• duodenal ulcers and gastric ulcers^[38]
• Death. Ingestion of large amounts of salt in a short time (about 1 g per kg of body weight) can be fatal. Salt solutions have been used in ancient China as a method of suicide (especially by the nobility, since salt was quite valuable). Deaths have also resulted from attempted use of salt solutions as emetics, forced salt intake, and accidental confusion of salt with sugar in child food.^[39]

Sea salt (an unrefined form of salt made by evaporating sea water) is often sold for use as a condiment. Because it contains trace amounts of other minerals which are removed in the refining process, it may have health advantages over normal table salt.^[40] Certain sea salts are also used in the production of bath salts and cosmetic products.

Rock and sea salt is usually referred and sold as Natrum Muriaticum in homeopathy, and purported by followers to be a deep acting and powerful curative when taken over long periods of time.

Some isolated cultures, such as the Yanomami in South America, have been found to consume little salt, possibly an adaptation originated in the predominantly vegetarian diet of human primate ancestors.^[41]

Recommended intake

Sea salt and peppercorns.

A salt mill for sea salt.

In the United Kingdom the Scientific Advisory Committee on Nutrition (SACN) recommended in 2003 that, for a typical adult, the Reference Nutrient Intake is 4 g salt per day (1.6 g or 70 mmol sodium). However, average adult intake is two and a half times the Reference Nutrient Intake for sodium. SACN states, "The target salt intakes set for adults and children do not represent ideal or optimum consumption levels, but achievable population goals."^[33] The Food Safety Authority of Ireland endorses the UK targets.^[36]

Health Canada recommends an Adequate Intake (AI) and an Upper Limit (UL) in terms of sodium,^[42] as does the Auckland District Health Board in New Zealand.^[43].

The NHMRC in Australia was not able to define a recommended dietary intake (RDI). It defines an Adaquate Intake (AI) for adults of 460-920mg/day and an Upper Level of intake (UL) of 2300mg/day.^[44]

In the United States, the Food and Drug Administration itself does not make a recommendation,^[45] but refers readers to Dietary Guidelines for Americans 2005. These suggest that US citizens should consume less than 2,300 mg of sodium (= 2.3 g sodium = 5.8 g salt) per day.^[46]

Labeling

UK: The Food Standards Agency defines the level of salt in foods as follows: "High is more than 1.5g salt per 100g (or 0.6g sodium). Low is 0.3g salt or less per 100g (or 0.1g sodium). If the amount of salt per 100g is in between these figures, then that is a medium level of salt." In the UK, foods produced by some supermarkets and manufacturers have ‘traffic light’ colors on the front of the pack: Red (High), Amber (Medium), or Green (Low).^[47]

USA: The FDA Food Labeling Guide stipulates whether a food can be labelled as "free", "low", or "reduced/less" in respect of sodium. When other health claims are made about a food (e.g. low in fat, calories, etc.), a disclosure statement is required if the food exceeds 480mg of sodium per 'serving.'^[48]

Campaigns

In 2004, Britain's 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 (SMA).^[49] The Advertising Standards Authority did not uphold the SMA complaint in its adjudication.^[50]. In March 2007, the FSA launched the third phase of their campaign with the slogan "Salt. Is your food full of it?" fronted by comedienne Jenny Eclair.^[51]

The Menzies Research Institute in Tasmania, Australia, maintains a website ^[52] dedicated to educating people about the potential problems of a salt-laden diet.

Consensus Action on Salt and Health (CASH)^[53] established in 1996, actively campaigns to raise awareness of the harmful health effects of salt. The 2008 focus includes raising awareness of high levels of salt hidden in sweet foods and marketed towards children.^[54]

Salt substitutes

Main article: Salt substitute

Salt intake can be reduced by simply reducing the quantity of salty foods in a diet, without recourse to salt substitutes. Salt substitutes have a taste similar to table salt and contain mostly potassium chloride, which will increase potassium intake. Excess potassium intake can cause hyperkalemia. Various diseases and medications may decrease the body's excretion of potassium, thereby increasing the risk of hyperkalemia. Those who have kidney failure, heart failure or diabetes should seek medical advice before using a salt substitute. One manufacturer, LoSalt, has issued an advisory statement^[55] that those taking the following prescription drugs should not use a salt substitute: Amiloride, Triamterene, Dytac, Spironolactone (Brand name Aldactone), Eplerenone and Inspra.

Production trends

Salt output in 2005

Salt is produced by evaporation of seawater or brine from other sources, such as brine wells and salt lakes, and by mining rock salt, called halite. In 2002, total world production was estimated at 210 million tonnes, the top five producers being the United States (40.3 million tonnes), China (32.9), Germany (17.7), India (14.5), and Canada (12.3).^[56] Note that these figures are not just for table salt but for sodium chloride in general.

See also

A ship loading salt from a terminal.

• Alberger process
• Black salt
• Curing (food preservation)
• Fleur de sel
• Halite
• History of salt
• International Salt Co. v. United States
• Kosher salt
• Old Salt Route
• Pink salt
• Salt equivalent
• Salt shaker
• Sodium chloride
• Sea salt
• Smoked salt

Notes

References

• Kurlansky, Mark (2002), Salt: A World History, New York: Walker & Co., ISBN 0802713734, OCLC 48573453 .
• Barber, Elizabeth Wayland (1999), The Mummies of Ürümchi, New York: W.W. Norton & Co., ISBN 0393320197, OCLC 48426519 .

Further reading

• Kurlansky, Mark, and S. D. Schindler. The Story of Salt. New York, NY: G.P. Putnam's Sons, 2006. ISBN 0399239987 -- a children's book about salt.
• Laszlo, Pierre. Salt: Grain of Life. Arts and traditions of the table. New York: Columbia University Press, 2001.
• 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.

External links

• Salt production methods and practices
• Salt Institute
• Cook's Thesaurus: Salt (Summary and descriptions of edible salts)
• Richard Cowen, Salt in History (Draft book chapter)

Salt and health

Government bodies

Many other government bodies are listed in the References section above.

• Ireland: Food Safety Authority of Ireland Salt and Health
• UK: Food Standards Agency Salt campaign
• UK: Scientific Advisory Committee on Nutrition (SACN) Salt and Health (PDF) and Salt Subgroup minutes
• UK: Why 6g? A summary of the scientific evidence for the salt intake target

Medical authorities

• The Cochrane Collaboration "Effect of longer-term modest salt reduction on blood pressure"
• Menzies Research Institute Salt Matters Web Site

Charities and campaigns

• British Nutrition Foundation article "Salt in the Diet"
• Consensus Action on Salt and Health (UK charity)
• Action on Salt and Health
• CSPI page Salt: The Forgotten Killer
• Irish Heart Foundation booklet Time to cut down on salt (PDF format)

Journalism

• BBC article "Salt: friend or foe?"
• BBC medical notes "Salt"
• Guardian article The sceptic
• Ockham's Razor Salt matters - talk by Dr Trevor Beard, Menzies Research Institute (ABC Radio National 4th February 2007)

Salt industry

• EuSalt Position papers
• LoSalt (salt substitute manufacturer)
• Salt Manufacturers' Association Salt and health
• Salt Institute Sodium and health

• ^  Bloch, David: Economics of NaCl: Salt made the world go round.