Iodised salt
Encyclopedia
Iodised salt is table salt mixed with a minute amount of various iodine-containing salts. The ingestion of iodide prevents iodine deficiency
. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of mental retardation
. It also causes thyroid
gland problems, including endemic goitre
. In many countries, iodine deficiency is a major public health problem that can be cheaply addressed by iodisation of salt.
Iodine is a micronutrient
that is naturally present in the food supply in many regions. However, where natural levels of iodine in the soil
are low and the iodine is not taken up by vegetables, iodine added to salt provides the small but essential amount needed by humans.
Iodide-treated table salt slowly loses its iodine content through the process of oxidation and iodine evaporation.
, potassium iodide
, sodium iodate
, and sodium iodide
. Any of these compounds supplies the body with its iodine required for the biosynthesis of thyroxine
(T4) and triiodothyronine
(T3) hormones by the thyroid gland. Animals also benefit from iodine supplements, and the hydrogen iodide
derivative of ethylenediamine is the main supplement to livestock feed.
Edible salt
can be iodised by spraying it with a potassium iodate
solution. 60 ml of potassium iodate, costing about USD$1.15 (in 2006), are required to iodise a ton of salt. Salt is an effective vehicle for distributing iodine to the public because it does not spoil and is consumed by everyone in the population in fairly predictable amounts. For example, the concentration of iodine in salt has gradually increased in Switzerland: 3.75 mg/kg in 1975, 7.5 mg/kg in 1962, 15 mg/kg in 1980, and 20 mg/kg in 1998. These increases were found to improve iodine status in the general Swiss population.
Salt that is iodised with iodide may slowly lose its iodine content by exposure to excess air over long periods. The halogen iodide, over time and exposure to excess oxygen and carbon dioxide, slowly oxidises to metal carbonate and elemental iodine, which then evaporates.
affects two billion people and is the leading preventable cause of mental retardation
. According to public health experts, iodisation of salt may be the world's simplest and most cost-effective measure available to improve health, only costing USD$0.05 per person per year. At the World Summit for Children
in
1990, a goal was set to eliminate iodine deficiency by 2000. At that time, 25% of households consumed iodised salt, a proportion that increased to 66% by 2006.
Salt producers are often, although not always, supportive of government initiatives to iodise edible salt supplies. Opposition to iodisation comes from small salt producers who are concerned about the added expense, private makers of iodine pills, concerns about promoting salt intake, and unfounded rumours that iodisation causes AIDS
or other illnesses. Iodisation programmes are more likely to be successful in areas where most edible salt is produced by a small number of large companies, as opposed to hundreds of smaller companies.
The United States
Food and Drug Administration
recommends 150 microgram
s of iodine per day for both men and women.
, a country in Central Asia in which local food supplies seldom contain sufficient iodine, has drastically reduced iodine deficiency through salt iodisation programmes. Campaigns by the government and non-profit organisations to educate the public about the benefits of iodised salt began in the mid 1990s, with iodisation of edible salt becoming legally mandatory in 2002.
was especially prevalent in the region around the Great Lakes
and the Pacific Northwest
.
David Murray Cowie
, a professor of paediatrics
at the University of Michigan
, led the U.S. to adopt the Swiss practice of adding sodium iodide
or potassium iodide
to table and cooking salt. On May 1, 1924, iodised salt was sold commercially in Michigan
. By the fall of 1924, Morton Salt Company began distributing iodised salt nationally.
is made for producing the brine to be used in pickling vegetables and other food-stuffs. This salt has no iodine added because the iodide can be oxidised by the foods and darken them—a harmless but aesthetically undesirable effect. Also, typical anticaking agent
s are not soluble in water, and form an unwanted precipitate, which is also undesirable in pickling jars.
Adding iron to iodised salt is complicated by a number of chemical, technical, and organoleptic issues. Since a viable DFS premix became available for scale-up in 2001, a body of scientific literature has been emerging to support the DFS initiative including studies conducted in Ghana, India, Côte d'Ivoire, Kenya and Morocco.
to enhance dental health.
Iodine deficiency
Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inlandareas where no marine foods are eaten—iodine deficiency gives rise to...
. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
. It also causes thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...
gland problems, including endemic goitre
Goitre
A goitre or goiter , is a swelling in the thyroid gland, which can lead to a swelling of the neck or larynx...
. In many countries, iodine deficiency is a major public health problem that can be cheaply addressed by iodisation of salt.
Iodine is a micronutrient
Micronutrient
Micronutrients are nutrients required by humans and other living things throughout life in small quantities to orchestrate a whole range of physiological functions, but which the organism itself cannot produce. For people, they include dietary trace minerals in amounts generally less than 100...
that is naturally present in the food supply in many regions. However, where natural levels of iodine in the soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
are low and the iodine is not taken up by vegetables, iodine added to salt provides the small but essential amount needed by humans.
Iodide-treated table salt slowly loses its iodine content through the process of oxidation and iodine evaporation.
Chemistry, biochemistry and nutritional aspects
Four inorganic compounds are used as iodide sources, depending on the producer: potassium iodatePotassium iodate
Potassium iodate is a chemical compound. It is ionic, made up of K+ ions and IO3- ions in a 1:1 ratio.-Chemical properties:Potassium iodate is an oxidizing agent and as such it can cause fires if in contact with combustible materials or reducing agents...
, potassium iodide
Potassium iodide
Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...
, sodium iodate
Sodium iodate
Sodium iodate is the sodium salt of iodic acid. Sodium iodate is an oxidizing agent and as such it can cause fires upon contact with combustible materials or reducing agents.-Preparation:...
, and sodium iodide
Sodium iodide
Sodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.-Uses:Sodium iodide is commonly used to treat and prevent iodine deficiency....
. Any of these compounds supplies the body with its iodine required for the biosynthesis of thyroxine
Thyroxine
Thyroxine, or 3,5,3',5'-tetraiodothyronine , a form of thyroid hormones, is the major hormone secreted by the follicular cells of the thyroid gland.-Synthesis and regulation:...
(T4) and triiodothyronine
Triiodothyronine
Triiodothyronine, C15H12I3NO4, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate....
(T3) hormones by the thyroid gland. Animals also benefit from iodine supplements, and the hydrogen iodide
Hydrogen iodide
Hydrogen iodide is a diatomic molecule. Aqueous solutions of HI are known as iohydroic acid or hydroiodic acid, a strong acid. Gas and aqueous solution are interconvertible...
derivative of ethylenediamine is the main supplement to livestock feed.
Edible salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
can be iodised by spraying it with a potassium iodate
Potassium iodate
Potassium iodate is a chemical compound. It is ionic, made up of K+ ions and IO3- ions in a 1:1 ratio.-Chemical properties:Potassium iodate is an oxidizing agent and as such it can cause fires if in contact with combustible materials or reducing agents...
solution. 60 ml of potassium iodate, costing about USD$1.15 (in 2006), are required to iodise a ton of salt. Salt is an effective vehicle for distributing iodine to the public because it does not spoil and is consumed by everyone in the population in fairly predictable amounts. For example, the concentration of iodine in salt has gradually increased in Switzerland: 3.75 mg/kg in 1975, 7.5 mg/kg in 1962, 15 mg/kg in 1980, and 20 mg/kg in 1998. These increases were found to improve iodine status in the general Swiss population.
Salt that is iodised with iodide may slowly lose its iodine content by exposure to excess air over long periods. The halogen iodide, over time and exposure to excess oxygen and carbon dioxide, slowly oxidises to metal carbonate and elemental iodine, which then evaporates.
In public health initiatives
Worldwide, iodine deficiencyIodine deficiency
Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inlandareas where no marine foods are eaten—iodine deficiency gives rise to...
affects two billion people and is the leading preventable cause of mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
. According to public health experts, iodisation of salt may be the world's simplest and most cost-effective measure available to improve health, only costing USD$0.05 per person per year. At the World Summit for Children
World Summit for Children
The United Nations World Summit for Children was held in New York on 29-30 September 1990, bringing together the then-largest-ever gathering of heads of state and government to commit to a set of goals to improve the well-being of children worldwide by the year 2000. The summit was the brain-child...
in
1990, a goal was set to eliminate iodine deficiency by 2000. At that time, 25% of households consumed iodised salt, a proportion that increased to 66% by 2006.
Salt producers are often, although not always, supportive of government initiatives to iodise edible salt supplies. Opposition to iodisation comes from small salt producers who are concerned about the added expense, private makers of iodine pills, concerns about promoting salt intake, and unfounded rumours that iodisation causes AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...
or other illnesses. Iodisation programmes are more likely to be successful in areas where most edible salt is produced by a small number of large companies, as opposed to hundreds of smaller companies.
The United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
recommends 150 microgram
Microgram
In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...
s of iodine per day for both men and women.
Kazakhstan
KazakhstanKazakhstan
Kazakhstan , officially the Republic of Kazakhstan, is a transcontinental country in Central Asia and Eastern Europe. Ranked as the ninth largest country in the world, it is also the world's largest landlocked country; its territory of is greater than Western Europe...
, a country in Central Asia in which local food supplies seldom contain sufficient iodine, has drastically reduced iodine deficiency through salt iodisation programmes. Campaigns by the government and non-profit organisations to educate the public about the benefits of iodised salt began in the mid 1990s, with iodisation of edible salt becoming legally mandatory in 2002.
United States
In the U.S. in the early 20th century, goitreGoitre
A goitre or goiter , is a swelling in the thyroid gland, which can lead to a swelling of the neck or larynx...
was especially prevalent in the region around the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
and the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
.
David Murray Cowie
David Murray Cowie
David Murray Cowie pioneered the salt iodation process in the U.S. A professor of pediatrics at the University of Michigan, Cowie was concerned about the widespread problem of goiter in Michigan ....
, a professor of paediatrics
Pediatrics
Pediatrics or paediatrics is the branch of medicine that deals with the medical care of infants, children, and adolescents. A medical practitioner who specializes in this area is known as a pediatrician or paediatrician...
at the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
, led the U.S. to adopt the Swiss practice of adding sodium iodide
Sodium iodide
Sodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.-Uses:Sodium iodide is commonly used to treat and prevent iodine deficiency....
or potassium iodide
Potassium iodide
Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...
to table and cooking salt. On May 1, 1924, iodised salt was sold commercially in Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
. By the fall of 1924, Morton Salt Company began distributing iodised salt nationally.
South Africa
The South African government instructed that all salt for sale was to be iodised after 1 December 1995.No-additive salts for canning and pickling
In contrast to table salt, which often has iodide as well as anticaking ingredients, special canning and pickling saltPickling salt
Pickling salt is a salt that is used mainly for canning and manufacturing pickles. It is made without iodine or any anticaking products added. If pickles are made with table salt, they will have dark and cloudy juice, due to the iodide in the salt, although the flavour should be about the same...
is made for producing the brine to be used in pickling vegetables and other food-stuffs. This salt has no iodine added because the iodide can be oxidised by the foods and darken them—a harmless but aesthetically undesirable effect. Also, typical anticaking agent
Anticaking agent
An anticaking agent is an additive placed in powdered or granulated materials, such as table salt, to prevent the formation of lumps, easing packaging, transport, and consumption....
s are not soluble in water, and form an unwanted precipitate, which is also undesirable in pickling jars.
Double-fortified salt
Salt can also be double-fortified with iron and iodine (see below). The iron is microencapsulated with stearine to prevent it from reacting with the iodine in the salt. By providing iron in addition to iodine in the convenient delivery vehicle of salt, it could serve as a sustainable approach to combating both iodine and iron deficiency disorders in areas where both deficiencies are prevalent.Adding iron to iodised salt is complicated by a number of chemical, technical, and organoleptic issues. Since a viable DFS premix became available for scale-up in 2001, a body of scientific literature has been emerging to support the DFS initiative including studies conducted in Ghana, India, Côte d'Ivoire, Kenya and Morocco.
Fluoridated salt
In some countries, table salt is treated with potassium fluoridePotassium fluoride
Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali metal halide and occurs naturally as the rare mineral carobbiite...
to enhance dental health.
See also
- Basil HetzelBasil HetzelBasil Stuart Hetzel, AC is an Australian medical researcher who has made a major contribution to combating iodine deficiency, a major cause of goitre and cretinism world wide.-Academic career:...
- Enriched flourEnriched flourEnriched flour is flour with specific nutrients returned to it that have been lost while it was prepared. These restored nutrients include iron and B vitamins . Calcium may also be supplemented. The purpose of enriching flour is to replenish the nutrients in the flour to match the nutritional...
serves an analogous function to "enriched salt". - History of saltHistory of saltSalt's ability to preserve food was a foundation of civilization. It eliminated the dependence on the seasonal availability of food and it allowed travel over long distances. However, salt was difficult to obtain, and so it was a highly valued trade item...
- IodineIodineIodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
is a trace elementTrace elementIn analytical chemistry, a trace element is an element in a sample that has an average concentration of less than 100 parts per million measured in atomic count, or less than 100 micrograms per gram....
essential to diet - Pickling saltPickling saltPickling salt is a salt that is used mainly for canning and manufacturing pickles. It is made without iodine or any anticaking products added. If pickles are made with table salt, they will have dark and cloudy juice, due to the iodide in the salt, although the flavour should be about the same...
- Sea saltSea saltSea salt, salt obtained by the evaporation of seawater, is used in cooking and cosmetics. It is historically called bay salt or solar salt...
- Water fluoridationWater fluoridationWater fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride...
, a similar public health intervention