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Salt is a flavor enhancer, composed primarily of sodium chloride, and is one of the few minerals commonly eaten by humans. There are different forms of edible salt: unrefined salt (such as sea salt), refined salt (table salt), and iodized salt. It is a crystalline solid, white, pale pink or light grey in color, normally obtained from sea water or rock deposits. Natural sea salt includes vital trace minerals in addition to the sodium chloride. Edible rock salts may be slightly greyish in color due to this mineral content.
Sodium and chlorine, the two components of salt, are necessary for the survival of all living creatures, including humans, but they need not be consumed as salt, where they are found together in very concentrated form. Some isolated cultures, such as the Yanomami in South America, have been found to consume little salt.[1] Salt is involved in regulating the water content (fluid balance) of the body. Salt flavor 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.
Overconsumption of salt can increase the risk of health problems, including high blood pressure. In food preparation, salt is used as a preservative and as a seasoning.
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 (NaCl) 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. By the Middle Ages, caravans consisting of as many as forty thousand camels traversed four hundred miles of the Sahara bearing salt, sometimes trading it for slaves.
The first registers of salt use were produced around 4000 B.C. in Egypt, and later in Greece and Rome. Salt was very valuable and used to preserve and flavor foods. In Ancient Rome, salt was used as a currency. The Latin word salarium; meaning a payment made in salt, is the root of the word "salary." Unfortunately for those paid with salt, it was easily ruined by rain and other weather conditions. Payments to Roman workers and soldiers were made in salt.[2] Salt was also given to the parents of the groom in marriage until the 8th century.
From the Phoenicians dates the evidence of harvesting solid salt from the sea. They also exported it to other civilizations. As a result of the increased salt supply from the sea, the value of salt depreciated. The harvest method used was flooding plains of land with seawater, then leaving the plains to dry. After the water dried, the salt which was left was collected and sold.
In the Mali Empire, merchants in 12th century Timbuktu—the gateway to the Sahara Desert and the seat of scholars—valued salt (NaCl) 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 importing the salt.[3]
During his protests in India, Mohandas Gandhi performed the famous salt march to challenge the British-imposed monopoly on salt.
There are thirty-five references (verses) to salt in the Bible (King James Version), the most familiar probably being the story of Lot's wife, who was turned into a pillar of salt when she disobeyed the angels and looked back at the wicked city of Sodom (Genesis 19:26). In the Sermon on the Mount, Jesus also 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) so that when others enquire about their beliefs, the Christian's answer generates a 'thirst' to know more about Christ.
In the native Japanese religion Shinto, salt is used for ritual purification of locations and people, such as in Sumo Wrestling.
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.[4] However, completely raw sea salt is bitter due to magnesium and calcium compounds, and thus is rarely eaten. Other people think that raw sea and rock salts do not contain sufficient iodine salts to prevent iodine deficiency diseases like goitre.[5]
Refined salt, which 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.[6] Salt is also obtained by evaporation of sea water, usually in shallow basins warmed by sunlight;[7] 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 (largely magnesium and calcium salts). Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are kiln-dried.
Anticaking agents (and potassium iodide, for iodised salt) 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 (acid salts), magnesium oxide, silicon dioxide, calcium silicate, 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 (FDA) permit their use.[8] The refined salt is then ready for packing and distribution.
Table salt is refined salt, 95% sodium chloride.[9] It usually contains substances that make it free flowing (anticaking agents) such as sodium silicoaluminate as well as a minute amount of invert sugar to prevent the salt from turning a yellow color 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 iodized—a small amount of potassium iodide (in the US) or potassium iodate (in the EU) is added as an important dietary supplement. Table salt is mainly employed in cooking and as a table condiment. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used.[10] Iodine is important to prevent the insufficient production of thyroid hormones (hypothyroidism), which can cause goitre, cretinism in children, and myxedema in adults.
In some European countries where fluoridation of drinking water is not practiced, fluorinated table salt is available. In Germany, 60% of sold table salt contains sodium or potassium fluoride.[11] Another additive, especially important for pregnant women is Folic acid (B vitamin) giving the table salt a yellow color.
In many Asian cultures, table salt is not traditionally used as a condiment.[12]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.
Sodium is one of the primary electrolytes in the body. All three electrolytes (sodium, potassium, 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.[13] 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.[14]
People's risk for disease due to salt intake that is too low or too high varies, due to 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 edible salt can be interpreted in many different ways.[15] [16]
Salt consumption has been linked to:
A study by Nancy Cook et al shows that people 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%.[28][29]
According to a finding from a reputed group practicing 'Nature Cure', salt can be linked to most of the diseases in humans. According to its founder Dr. Raju [30] "The salt that we add to taste is roughly from 4000 mg to 25000 mg. Means we are consuming salt many times than required to satisfy the tongue. We do get the natural sodium more than enough through our natural food like fruits, vegetables, milk etc every day, causing no deficiency."
This section summarizes the salt intake recommended by the health agencies of various countries. Recommendations tend to be similar. Note that targets for the population as a whole tend to be pragmatic (what is achievable) while advice for an individual is ideal (what is best for health). For example, in the UK target for the population is "eat no more than 6 g a day" but for a person is 4 g.
Intakes can be expressed variously as salt or sodium and in various units.
United Kingdom: In 2003, the UK's Scientific Advisory Committee on Nutrition (SACN) recommended 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. "Although accurate data are not available for children, conservative estimates indicate that, on a body weight basis, the average salt intake of children is higher than that of adults." SACN aimed for an achievable target reduction in average intake of salt to 6 g per day (2.4 g or 100 mmol sodium) — this is roughly equivalent to a teaspoonful of salt. The SACN recommendations for children are:
Republic of Ireland: The Food Safety Authority of Ireland endorses the UK targets "emphasising that the RDA of 1.6 g sodium (4 g salt) per day should form the basis of advice targeted at individuals as distinct from the population health target of a mean salt intake of 6 g per day."([25], p16)
Canada: Health Canada recommends an Adequate Intake (AI) and an Upper Limit (UL) in terms of sodium.
Australia: The recommended dietary intake (RDI) is 0.92 g–2.3 g sodium per day (= 2.3 g–5.8 g salt)[33]
USA: The Food and Drug Administration itself does not make a recommendation[34] 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. [35]
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).[36]
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.'[37]
In 2004, the 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).[38] The Advertising Standards Authority did not uphold the SMA complaint in its adjudication.[39].
The Menzies Research Institute in Tasmania, Australia, maintains a website [40] dedicated to educating people about the potential problems of a salt-laden diet.
The "Salt Dish Campaign" took place on April 7th, 2006. It is celebrated annually.
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.[41] that people taking the following prescription drugs should not use a salt substitute: Amiloride, Triamterene, Dytac, Spironolactone, Aldactone, Eplerenone, and Inspra.
Many other government bodies are listed in the References section above.
Chemical data
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