Iodised salt (
also spelled iodized salt) is
table salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
mixed with a minute amount of various salts of the element
iodine
Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...
. The ingestion of iodine prevents
iodine deficiency
Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated cong ...
. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of
intellectual and developmental disabilities.
Deficiency also causes
thyroid
The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...
gland problems, including
endemic goitre
Endemic goiter is a type of goitre that is associated with dietary iodine deficiency.
Cause
Some inland areas where soil and water lacks in iodine compounds and consumption of marine foods is low are known for higher incidence of goitre. In such ...
. In many countries, iodine deficiency is a major public health problem that can be cheaply addressed by purposely adding small amounts of iodine to the
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
salt.
Iodine is a
micronutrient
Micronutrients are nutrient, essential dietary elements required by organisms in varying quantities throughout life to orchestrate a range of physiological functions to maintain health. Micronutrient requirements differ between organisms; for exam ...
and
dietary mineral
In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon ...
that is naturally present in the food supply in some regions, especially near sea coasts but is generally quite rare in the Earth's crust since iodine is a so-called heavy element, and
abundance of chemical elements
The abundance of the chemical elements is a measure of the occurrence of the chemical elements relative to all other elements in a given environment. Abundance is measured in one of three ways: by the mass-fraction (the same as weight fraction); ...
generally declines with greater atomic mass. Where natural levels of iodine in the
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
are low and the iodine is not taken up by vegetables, iodine added to salt provides the small but essential amount of iodine needed by humans.
An opened package of table salt with
iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...
may rapidly lose its iodine content in high temperature and high relative humidity conditions through the process of oxidation and iodine
sublimation.
Chemistry, biochemistry and nutritional aspects
![Iodised salt](https://upload.wikimedia.org/wikipedia/commons/8/82/Iodised_salt.JPG)
Four
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
s are used as iodide sources, depending on the producer:
potassium iodate
Potassium iodate ( K I O3) is an ionic chemical compound consisting of K+ ions and IO3− ions in a 1:1 ratio.
Preparation and properties
Potassium iodate is an oxidizing agent and as such it can cause fires if in contact with combustible materi ...
,
potassium iodide
Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are us ...
,
sodium iodate
Sodium iodate ( Na I O3) is the sodium salt of iodic acid. Sodium iodate is an oxidizing agent. It has few uses.
Preparation
It can be prepared by the reacting a sodium-containing base such as sodium hydroxide with iodic acid, for example:
: ...
, and
sodium iodide
Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions (I ...
. Any of these compounds supplies the body with its iodine required for the biosynthesis of
thyroxine
File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones T3 and T4
rect 376 268 820 433 Thyroid-stimulating hormone
rect 411 200 849 266 Thyrotropin-releasing hormone
rect 297 168 502 200 Hypothalamus
rect 66 216 386 25 ...
(T
4) and
triiodothyronine
Triiodothyronine, 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.
Production of T3 and its prohormone thyroxine ( ...
(T
3) hormones by the thyroid gland. Animals also benefit from iodine supplements, and the
hydrogen iodide
Hydrogen iodide () is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under sta ...
derivative of
ethylenediamine
Ethylenediamine (abbreviated as en when a ligand) is the organic compound with the formula C2H4(NH2)2. This colorless liquid with an ammonia-like odor is a basic amine. It is a widely used building block in chemical synthesis, with approximately ...
is the main supplement to livestock feed.
Salt is an effective vehicle for distributing iodine to the public because it does not spoil and is consumed in more predictable amounts than most other commodities. For example, the concentration of iodine in salt has gradually increased in
Switzerland
). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
: 3.75 mg/kg in 1952, 7.5 mg/kg in 1962, 15 mg/kg in 1980, 20 mg/kg in 1998, and 25 mg/kg in 2014. These increases were found to improve iodine status in the general Swiss population.
Salt that is iodized may slowly lose its iodine content by exposure to excess air over long periods.
Production
Edible
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
can be iodised by spraying it with a potassium iodate or potassium iodide solution. 57 grams of potassium iodate, costing about US$1.15 (in 2006), is required to iodise a ton (2,000 pounds) of salt.
[ ]Dextrose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
is added as a stabilizer to prevent potassium iodide from oxidizing and evaporating. Anti-caking agents such as calcium silicate
Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and is sometimes formulated as 2CaO·SiO2. It is also referred to by the shortened trade name Cal-Sil or Calsil. It occurs naturally as the mineral larnite.
...
are commonly added to table salt to prevent clumping.
In public health initiatives
Worldwide, iodine deficiency
Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated cong ...
affects two billion people and is the leading preventable cause of intellectual and developmental disabilities. 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 US$0.05 per person per year.[ At the ]World Summit for Children
The United Nations World Summit for Children was held in the United Nations Headquarters in New York City on 29–30 September 1990. The summit had the then-largest-ever gathering of heads of state and government to commit to a set of goals to impr ...
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 iodize edible salt supplies. Opposition to iodization comes from small salt producers who are concerned about the added expense, private makers of iodine pills, concerns about promoting salt intake, and unfounded rumors that iodization causes ]AIDS
Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual m ...
or other illnesses.[
The ]United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
recommends 150 microgram
In the metric system, a microgram or microgramme is a unit of mass equal to one millionth () of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and United Kingdom whe ...
s (0.15 mg) of iodine per day for adults.
Argentina
Since 8 May 1967 salt for human or animal use must be iodised, according to the Law 17,259.
Syria
In the end of eighties of last century, a Syrian endocrinologist Samir Ouaess conducted a research on hypothyroidism and noticed that 90 percent of Syrians suffer from hypothyroidism, 50 percent suffer from health problems as a result of Thyroid deficiency, and 10 percent of students suffer from a decline in their academic level due to that problem. Dr. Ouaess linked these results with the fact that natural drinking water sources in Syria do not contain enough minerals. He presented the result of that study to the Syrian Ministry of Health. After that, adding iodine to salt became almost mandatory till 2021, when the Syrian government canceled the iodization of salt and as a result of economic problems related to economic sanctions.
Australia
Australian children were identified as being iodine deficient in a survey conducted between 2003 and 2004. As a result of this study the Australian Government mandated that all bread with the exception of "organic" bread must use iodised salt. There remains concern that this initiative is not sufficient for pregnant and lactating women.
Brazil
Iodine Deficiency Disorders were detected as a major public health issue by Brazilian authorities in the 1950s when about 20% of the population had a goitre
A goitre, or goiter, is a swelling in the neck resulting from an enlarged thyroid gland. A goitre can be associated with a thyroid that is not functioning properly.
Worldwide, over 90% of goitre cases are caused by iodine deficiency. The term is ...
. The National Agency for Sanitary Vigilance (ANVISA) is responsible for setting the mandatory iodine content of table salt. The Brazilian diet averages 12 g of table salt per day, more than twice the recommended value of 5 g a day. To avoid excess consumption of iodine, the iodizing of Brazilian table salt was reduced to 15–45 mg/kg in July 2013. Specialists criticized the move, saying that it would be better for the government to promote reduced salt intake, which would solve the iodine problem as well as reduce the incidence of high blood pressure.
Canada
Salt sold to consumers in Canada for table and household use must be iodized with 0.01% potassium iodide. Sea salt and salt sold for other purposes, such as pickling, may be sold uniodized.
China
Much of the Chinese population lives inland, far from sources of dietary iodine. In 1996, the Chinese Ministry of Public Health estimated that iodine deficiency was responsible for 10 million cases of intellectual developmental disorders in China. Chinese governments have held a legal monopoly on salt production since 119 BCE and began iodizing salt in the 1960s, but market reforms in the 1980s led to widespread smuggling of non-iodized salt from private producers. In the inland province of Ningxia
Ningxia (,; , ; alternately romanized as Ninghsia), officially the Ningxia Hui Autonomous Region (NHAR), is an autonomous region in the northwest of the People's Republic of China. Formerly a province, Ningxia was incorporated into Gansu in ...
, only 20% of salt consumed was sold by the China National Salt Industry Corporation. The Chinese government responded by cracking down on smuggled salt, establishing salt police with 25,000 officers to enforce the salt monopoly. Consumption of iodized salt reached 90% of the Chinese population by 2000.
India
India and all of its states ban the sale of non-iodized salt for human consumption. However, implementation and enforcement of this policy are imperfect; a 2009 survey found that 9% of households used non-iodized salt and that another 20% used insufficiently iodized salt.
Iodised salt was introduced to India in the late 1950s. Public awareness was increased by special programs and initiatives, both governmental and nongovernmental. As of now, iodine deficiency is only present in a few isolated regions which are still unreachable. In India, some people use Himalayan rock salt. Rock salt however is low in iodine and should be consumed only when there are other iodine-rich foods in diet.
Kazakhstan
Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...
, a country in Central Eurasia in which local food supplies seldom contain sufficient iodine, has drastically reduced iodine deficiency through salt iodization programs. Campaigns by the government and non-profit organizations to educate the public about the benefits of iodized salt began in the mid-1990s, with iodization of edible salt becoming legally mandatory in 2002.[
]
Nepal
The Salt Trading Corporation has been distributing Iodized Salt in Nepal since 1963. 98% of the Population uses Iodized Salt. Utilising non-Iodised salt for human consumption is prohibited. Salt costs about US$0.27 a Kilo.
Philippines
On December 20, 1995, Philippine President Fidel V. Ramos
Fidel Valdez Ramos (, ; March 18, 1928 – July 31, 2022), popularly known as FVR and Eddie Ramos, was a Filipino general and politician who served as the 12th president of the Philippines from 1992 to 1998. He was the only career military ...
signed Republic Act 8172: An Act for Salt Iodization Nationwide (ASIN).
Romania
According to the 568/2002 law signed by the Romanian parliament and republished in 2009, since 2002 iodized salt is distributed mandatory in the whole country. It is used mandatory on the market for household consumption, in bakeries, and for pregnant women. Iodised salt is optional though for animal consumption and the food industry, although widely used. The salt iodization process has to assure a minimum of 30mg iodine/kg of salt.
South Africa
The South African government instructed that all salt for sale was to be iodised after December 12, 1995.
United States
Iodized salt is not mandatory in the US but it is widely available.
In the U.S. in the early 20th century, goitres were especially prevalent in the region around the Great Lakes
The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...
and the Pacific Northwest
The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...
. David Murray Cowie
David Murray Cowie (November 19, 1872 – January 27, 1940) was a Canadian-American physician. He pioneered the salt iodization process in the U.S. He founded the pediatrics department at the University of Michigan and ran a private hospital in An ...
, a professor of paediatrics
Pediatrics ( also spelled ''paediatrics'' or ''pædiatrics'') is the branch of medicine that involves the medical care of infants, children, adolescents, and young adults. In the United Kingdom, paediatrics covers many of their youth until the ...
at the University of Michigan
, mottoeng = "Arts, Knowledge, Truth"
, former_names = Catholepistemiad, or University of Michigania (1817–1821)
, budget = $10.3 billion (2021)
, endowment = $17 billion (2021)As o ...
, led the U.S. to adopt the Swiss
Swiss may refer to:
* the adjectival form of Switzerland
* Swiss people
Places
* Swiss, Missouri
* Swiss, North Carolina
*Swiss, West Virginia
* Swiss, Wisconsin
Other uses
*Swiss-system tournament, in various games and sports
*Swiss Internation ...
practice of adding sodium iodide
Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions (I ...
or potassium iodide
Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are us ...
to table and cooking salt. On May 1, 1924, iodised salt was sold commercially in Michigan
Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...
. By the fall of 1924, Morton Salt Company
Morton Salt is an American food company producing salt for food, water conditioning, industrial, agricultural, and road/highway use. Based in Chicago, the business is North America's leading producer and marketer of salt. It is a subsidiary of ...
began distributing iodised salt nationally.
A 2017 study found that the introduction of iodized salt in 1924 raised the IQ for the one-quarter of the population most deficient in iodine. These findings "can explain roughly one decade's worth of the upward trend in IQ in the United States (the Flynn effect
The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standa ...
)". The study also found "a large increase in thyroid-related deaths following the countrywide adoption of iodized salt, which affected mostly older individuals in localities with high prevalence of iodine deficiency". A 2013 study found a gradual increase in average intelligence of 1 standard deviation, 15 points in iodine-deficient areas and 3.5 points nationally after the introduction of iodized salt.
A 2018 paper found that the nationwide distribution of iodine-fortified salt increased incomes by 11%, labor force participation by 0.68 percentage points and full-time work by 0.9 percentage points. According to the study, "These impacts were largely driven by changes in the economic outcomes of young women. In later adulthood, both men and women had higher family incomes due to iodization."
No-additive salts for canning and pickling
In contrast to table salt, which often contains iodide as well as anti-caking ingredients, special canning and pickling salt
Pickling salt is a salt that is used mainly for canning and manufacturing pickles. It is sodium chloride, as is table salt, but unlike most brands of table salt, it does not contain iodine or any anti caking products added. A widely circulated ...
is made for producing the brine to be used in pickling vegetables and other foodstuffs. Contrary to popular belief, however, iodized salt affects neither color, taste, nor consistency of pickles.
Fortification of salt with other elements
Double-fortified salt (DFS)
Salt can also be double-fortified with iron and iodine. The iron is microencapsulated with stearin 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 iodized salt is complicated by several 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 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 halide and occurs naturally as the rare m ...
to enhance dental health.
Diethylcarbamazine
In India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
and China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, diethylcarbamazine
Diethylcarbamazine is a medication used in the treatment of filariasis including lymphatic filariasis, tropical pulmonary eosinophilia, and loiasis. It may also be used for prevention of loiasis in those at high risk. While it has been used for o ...
has been added to salt to combat lymphatic filariasis
Lymphatic filariasis is a human disease caused by parasitic worms known as filarial worms. Usually acquired in childhood, it is a leading cause of permanent disability worldwide. While most cases have no symptoms, some people develop a syndrome ...
.
WHO: Unfulfilled potential: using diethylcarbamazine-fortified salt to eliminate lymphatic filariasis
See also
* Basil Hetzel
Basil Stuart Hetzel (13 June 1922 – 4 February 2017) was an Australian medical researcher who made a major contribution to combating iodine deficiency, a major cause of goitre and cretinism worldwide.
Early life and education
Hetzel was bor ...
* Enriched flour
Enriched flour is flour with specific nutrients returned to it that have been lost while being prepared. These restored nutrients include iron and B vitamins (folic acid, riboflavin, niacin, and thiamine). Calcium may also be supplemented. The ...
serves an analogous function to "enriched salt".
* History of salt
Salt, also referred to as table salt or by its chemical formula NaCl (sodium chloride), is an ionic compound made of sodium and chloride ions. All life depends on its chemical properties to survive. It has been used by humans for thousands of ...
* Lugol's iodine
Lugol's iodine, also known as aqueous iodine and strong iodine solution, is a solution of potassium iodide with iodine in water. It is a medication and disinfectant used for a number of purposes. Taken by mouth it is used to treat thyrotoxicosi ...
* Sea salt
Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt, solar salt, or simply salt. Like mined rock salt, production of sea sa ...
* Water fluoridation
Water fluoridation is the controlled adjustment of fluoride to a public water supply solely to reduce tooth decay. Fluoridated water contains fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding ...
, a similar public health intervention
* Food fortification
Food fortification or enrichment is the process of adding micronutrients (essential trace elements and vitamins) to food. It can be carried out by food manufacturers, or by governments as a public health policy which aims to reduce the number of p ...
Notes
References
*
21 CFR
101.9 (c)(8)(iv)
Newton County – Encyclopedia of Arkansas
External links
Iodine intake as a risk factor for thyroid cancer: a comprehensive review of animal and human studies
{{authority control
Edible salt
Salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
History of salt
Endocrinology