Iodised salt

{{Short description|Table salt preparation with iodide salts added}} {{use British English|date=March 2026}}  thumb|An example of a commonly distributed packet of iodised salt

'''Iodised salt''' (also spelled '''iodized salt''') is table salt mixed with a minuscule amount of various iodine salts. The ingestion of iodine prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of intellectual and developmental disabilities.<ref name="mcneil"/><ref name="The Lancet-2008">{{Cite journal |url = http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(08)61009-0/fulltext |title = Iodine deficiency—way to go yet|date = 12 July 2008 |journal = The Lancet |access-date = 2014-12-10 |doi = 10.1016/S0140-6736(08)61009-0 |pmid = 18620930 |volume=372 |issue = 9633|page=88|last1 = The Lancet|s2cid = 5416860}}</ref> Deficiency 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 purposely adding small amounts of iodine to the sodium chloride salt.

Iodine is a micronutrient and dietary mineral 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. Where natural levels of iodine in the soil are low and vegetables do not take up the iodine, iodine added to salt provides the small but essential amount of iodine needed by humans.

An opened package of table salt with iodide may rapidly lose its iodine content in high temperature and high relative humidity conditions through the process of oxidation and iodine sublimation.<ref>Diosady, L. L., and M. G. Venkatesh Mannar. "Stability of iodine in iodized salt". 8th World Salt Symposium. Amsterdam: Elsevier. 2000.</ref> Poor manufacturing techniques and storage processes can also lead to insufficient amounts of iodine in table salt.<ref>{{Cite web |title=Table salt needs extra iodine – Bangladesh study |url=https://www.scidev.net/global/news/table-salt-needs-extra-iodine-bangladesh-study/ |access-date=2023-10-30 |website=SciDev.Net |language=en-US}}</ref>

==Chemistry, biochemistry, and nutritional aspects== thumb|A pile of iodised salt

Four inorganic compounds are used as iodine sources, depending on the producer: potassium iodate, potassium iodide, sodium iodate, and sodium iodide. Any of these compounds supplies the body with the iodine required for the biosynthesis of thyroxine (T<sub>4</sub>) and triiodothyronine (T<sub>3</sub>) 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.<ref>Phyllis A. Lyday "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. {{doi|10.1002/14356007.a14_381}}.</ref>

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: 3.75 mg/kg in 1922,<ref name=swiss/> 7.5 mg/kg in 1962, 15 mg/kg in 1980, 20 mg/kg in 1998, and 25 mg/kg since 2014.<ref>{{cite web |title=Sel de cuisine: hausse du taux d'enrichissement en iode |url=https://www.news.admin.ch/fr/nsb?id=51580 |publisher=Swiss Federal Administration |language=fr |access-date=8 January 2014}}</ref> These increases were found to improve iodine status in the general Swiss population.<ref>{{cite journal |title=Increasing the iodine concentration in the Swiss iodized salt programme markedly improved iodine status in pregnant women and children: a 5-y prospective national study |date=August 2005 |journal=American Journal of Nutrition |author1=Michael B Zimmermann |author2=Isabelle Aeberli |author3=Toni Torresani |author4=Hans Bürgi |volume=82 |issue=2 |pages=388–392 |pmid=16087983|doi=10.1093/ajcn.82.2.388 |doi-access=free }}</ref>

Salt that is iodised with iodide may slowly lose its iodine content by exposure to excess air over long periods.<ref>Katarzyna Waszkowiak & Krystyna Szymandera-Buszka. Effect of storage conditions on potassium iodide stability in iodised table salt and collagen preparations. International Journal of Food Science & Technology. Volume 43 Issue 5, Pages 895–899. (Published Online: 27 Nov 2007).</ref> Salts fortified with iodate are relatively stable to storage and heat; the main concern is reducing impurities in the salt itself, which can be removed relatively easily. Moisture accelerates the decomposition of iodate,<ref>{{cite journal |last1=Waszkowiak |first1=Katarzyna |last2=Szymandera-Buszka |first2=Krystyna |title=Effect of storage conditions on potassium iodide stability in iodised table salt and collagen preparations |journal=International Journal of Food Science & Technology |date=May 2008 |volume=43 |issue=5 |pages=895–899 |doi=10.1111/j.1365-2621.2007.01538.x}}</ref> but ceases to do so once reducing impurities are removed.<ref>{{cite journal |last1=Shi |first1=Huimin |title=Adding An Oxidant Increases the Stability of Iodine in Iodized Salt |journal=Food and Nutrition Bulletin |date=January 2004 |volume=25 |issue=2 |pages=137–141 |doi=10.1177/156482650402500205|pmid=15214259 }}</ref>

Contrary to popular assumptions, iodised salt cannot be used as a substitute for potassium iodide (KI) to protect a person's thyroid gland in the event of a nuclear emergency. There is not enough iodine in iodised salt to block the uptake of radioactive iodine by the thyroid.<ref>{{cite web | work = World Health Organisation | url = https://www.who.int/news-room/questions-and-answers/item/use-of-potassium-iodine-for-thyroid-protection-during-nuclear-or-radiological-emergencies#:~:text=During%20nuclear%20emergencies%2C%20iodized%20table,pose%20a%20significant%20health%20hazard. | title = Use of potassium iodine for thyroid protection during nuclear or radiological emergencies | date = 7 July 2023 }}</ref>

==Production== {{owidslider | start = 2020 | list = Template:OWID/Share of households consuming iodized salt#gallery | location = commons | caption = | title = | language = | file = link=|thumb|upright=1.6|right|Share of households consuming iodized salt | startingView = World }}

Edible salt 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 short ton (2,000 pounds) of salt.<ref name=mcneil/> Optional additives include: * Stabilisers such as dextrose (typically at about 0.04%) and sodium thiosulfate, which prevent potassium iodide from oxidizing and evaporating. These ingredients are not required for potassium iodate, which is commonly used globally for its increased stability, but is not approved by the US FDA.<ref name=salt-inst>{{cite web|title=Iodized Salt|url=http://www.saltinstitute.org/news-articles/iodized-salt/|work=The Salt Institute|access-date=7 October 2013|archive-url=https://web.archive.org/web/20131016171353/http://www.saltinstitute.org/news-articles/iodized-salt/|archive-date=16 October 2013}}</ref> * Anti-caking agents such as calcium silicate and sodium ferrocyanide, which prevent clumping.<ref name=salt-inst/>

==Public health initiatives== [[File:Stamp of Indonesia - 1996 - Colnect 253494 - UNICEF.jpeg|thumb|right|Promotion of iodised salt to children by UNICEF on a 1996 Indonesian postage stamp]]

Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual and developmental disabilities.<ref name="mcneil">{{cite news|url=https://www.nytimes.com/2006/12/16/health/16iodine.html?fta=y|title=In Raising the World's I.Q., the Secret's in the Salt|last=McNeil|first=Donald G. Jr|date=2006-12-16|work=New York Times|access-date=2008-12-04}}</ref><ref name="The Lancet-2008"/> 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.<ref name=mcneil/> 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.<ref name=mcneil/>

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.<ref name=mcneil/>

The United States Food and Drug Administration recommends<ref>{{Cite web |url=http://www.access.gpo.gov/nara/cfr/waisidx_05/21cfr101_05.html |title=2005 CFR Title 21, Volume 2 |access-date=2006-04-11 |archive-url=https://web.archive.org/web/20120217203548/http://www.access.gpo.gov/nara/cfr/waisidx_05/21cfr101_05.html |archive-date=2012-02-17 }}</ref> 150 micrograms (0.15 mg) of iodine per day for adults. While iodine is crucial, the FDA also recommends limiting overall sodium intake to less than 2,300 mg per day for adults, which is approximately 1 teaspoon of table salt.<ref>{{Cite journal |last=Program |first=Human Foods |date=2025-02-27 |title=Sodium in Your Diet |url=https://www.fda.gov/food/nutrition-education-resources-materials/sodium-your-diet |journal=FDA |language=en}}</ref>

===Argentina=== Since 8 May 1967 salt for human or animal use must be iodised, according to the Law 17,259.<ref>{{cite web|url=https://servicios.infoleg.gob.ar/infolegInternet/verNorma.do;jsessionid=D3B5BA571D052F13A9EDCDDE5382CA43?id=197392|title=InfoLeg - Información Legislativa|website=servicios.infoleg.gob.ar}}</ref> ===Australia=== Australian children were identified as being iodine deficient in a survey conducted between 2003 and 2004.<ref>{{Cite journal |last1=Li |first1=Mu |last2=Eastman |first2=Creswell J. |author-link2=Creswell Eastman |last3=Waite |first3=Kay V. |last4=Ma |first4=Gary |last5=Byth |first5=Karen |last6=Zacharin |first6=Margaret R. |author-link6=Margaret Zacharin |last7=Topliss |first7=Duncan J. |last8=Harding |first8=Philip E. |last9=Walsh |first9=John P. |date=2006-01-01 |title=Are Australian children iodine deficient? Results of the Australian National Iodine Nutrition Study |url=https://www.mja.com.au/journal/2006/184/4/are-australian-children-iodine-deficient-results-australian-national-iodine |journal=Medical Journal of Australia |volume=184 |issue=4 |pages=165–169 |doi=10.5694/j.1326-5377.2006.tb00177.x |issn=0025-729X |pmid=16489900 |s2cid=5862807 |url-access=subscription}}</ref> As a result of this study the Australian Government mandated that all bread except "organic" bread must use iodised salt.<ref>{{Cite web|url=https://www.abc.net.au/health/thepulse/stories/2008/11/06/2399550.htm|title=Your daily bread, now with iodine - Health & Wellbeing|last=Corporation|first=Australian Broadcasting|website=www.abc.net.au|access-date=2016-12-31}}</ref> There remains concern that this initiative is not sufficient for pregnant and lactating women.<ref>{{Cite journal|last1=Gallego|first1=Gisselle|last2=Goodall|first2=Stephen|last3=Eastman|first3=Creswell J.|date=2010-01-01|title=Iodine deficiency in Australia: is iodine supplementation for pregnant and lactating women warranted?|url=https://www.mja.com.au/journal/2010/192/8/iodine-deficiency-australia-iodine-supplementation-pregnant-and-lactating-women#4|journal=Medical Journal of Australia|volume=192|issue=8|pages=461–463|doi=10.5694/j.1326-5377.2010.tb03586.x|pmid=20402611|s2cid=38147490|issn=0025-729X|url-access=subscription}}</ref>

===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.<ref>{{Cite web|url=http://colegiomarista.org.br/joaopauloii/pesquisa-avalia-impacto-do-sal-iodado-no-brasil|title=Pesquisa avalia Impacto do Sal Iodado no Brasil|website=colegiomarista.org.br|lang=pt-BR}}</ref> 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 daily, more than twice the recommended value of 5 g daily. To avoid excess consumption of iodine, the iodizing of Brazilian table salt was reduced to 15–45 mg/kg in July 2013. Specialists criticised 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.<ref>{{Cite web|url=https://g1.globo.com/bemestar/noticia/2013/04/sal-com-menos-iodo-deve-ser-produzido-no-brasil-em-ate-90-dias.html|title=Sal com menos iodo deve ser produzido no Brasil em até 90 dias|first1=Do|last1=G1|first2=em São|last2=Paulo|date=April 25, 2013|website=Bem Estar|lang=pt-BR}}</ref>

===Canada=== For table and household use, salt sold to consumers in Canada must be iodised with 0.01% potassium iodide. Sea salt and salt sold for other purposes, such as pickling, may be sold uniodised.<ref>{{cite web|url=http://www.inspection.gc.ca/food/labelling/food-labelling-for-industry/salt/eng/1391790253201/1391795959629?chap=0|title=Labelling Requirements for Salt|date=7 February 2014|access-date=20 October 2017|archive-date=30 August 2018|archive-url=https://web.archive.org/web/20180830115339/http://www.inspection.gc.ca/food/labelling/food-labelling-for-industry/salt/eng/1391790253201/1391795959629?chap=0}}</ref>

===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.<ref>{{cite news|last1=Tyler|first1=Patrick E.|title=China Confronts Retardation Of Millions Deficient in Iodine|work=The New York Times |url=https://www.nytimes.com/1996/06/04/world/china-confronts-retardation-of-millions-deficient-in-iodine.html|access-date=28 October 2015|agency=The New York Times|date=4 June 1996}}</ref> Chinese governments have held a legal monopoly on salt production since 119 BCE and began iodizing salt in the 1960s, but the reform and opening up in the 1980s led to widespread smuggling of non-iodised salt from private producers. In the inland province of Ningxia, only 20% of the salt consumed was sold by the China National Salt Industry Corporation. The Chinese government responded by cracking down on smuggled salt, establishing a salt police with 25,000 officers to enforce the salt monopoly. Consumption of iodised salt reached 90% of the Chinese population by 2000.<ref>{{cite news|last1=Fackler|first1=Martin|title=Special police protect an ancient monopoly -- and China's public health|agency=Associated Press|date=October 13, 2002}}</ref>

===India=== India and all of its states ban the sale of non-iodised salt for human consumption. However, implementation and enforcement of this policy are imperfect; a 2009 survey found that 9% of households used non-iodised salt and that another 20% used insufficiently iodised salt.<ref>{{Cite journal|last1=Rah|first1=Jee H.|last2=Anas|first2=Ansari M.|last3=Chakrabarty|first3=Arijit|last4=Sankar|first4=Rajan|last5=Pandav|first5=Chandrakant S.|last6=Aguayo|first6=Victor M.|date=2013-06-18|title=Towards universal salt iodisation in India: achievements, challenges and future actions|journal=Maternal & Child Nutrition|volume=11|issue=4|pages=483–496|doi=10.1111/mcn.12044|issn=1740-8695|pmc=6860305|pmid=23795562}}</ref>

Iodised salt was introduced to India in the late 1950s. Public awareness was increased by special programmes and initiatives, both governmental and non-governmental. Currently, 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 other iodine-rich foods are in the diet.{{cn|date=May 2022}}

===Iran=== A national programme with iodised salt started in 1992. A national survey of 1990 revealed the prevalence of iodine deficiency to be 20{{px2}}–{{px2}}80% in different parts of Iran indicating a major public health problem. Central provinces, far from the sea, had the highest prevalence of iodine deficiency. The national salt enrichment programme was very successful. The prevalence of goiter in Iran dropped dramatically. The national survey in 1996 reported that 40% of boys and 50% of girls have goiter. The 3rd national survey in 2001 showed that the total goiter rate is 9.8%. In 2007, the 4th national survey was conducted 17 years after iodised salt consumption by Iranian households. In this study, the total goiter rate was 5.7%.{{cn|date=September 2023}}

Concerns of iodine deficiency have raised over recent years due to the consumption of non-iodised salts especially sea salt which is strongly suggested by traditional medicine workers in Iran, many of whom lack a pertinent academic background.{{Citation needed|date=September 2023}}

===Kazakhstan=== Kazakhstan, a country in Central Eurasia 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.<ref name=mcneil/>

===Malaysia=== Salt being sold in the country must be iodised which is forced under the Food Regulation 1985 from 30 September 2020.<ref>{{Cite news |date=2020-09-25 |title=Health DG: Iodine must be added to salt being sold from Sept 30 |work=The Star (Malaysia) |url=https://www.thestar.com.my/news/nation/2020/09/25/health-dg-iodine-must-be-added-to-salt-being-sold-from-sept-30 |url-status=live |access-date=2023-07-10 |archive-url=https://web.archive.org/web/20230713165227/https://www.thestar.com.my/news/nation/2020/09/25/health-dg-iodine-must-be-added-to-salt-being-sold-from-sept-30 |archive-date=2023-07-13}}</ref>

===Nepal=== The Salt Trading Corporation has been distributing Iodised Salt in Nepal since 1963.<ref>{{Cite web|title=Salt Trading Corporation|url=https://www.stcnepal.com/|access-date=2021-06-12|website=www.stcnepal.com}}</ref> 98% of the Population uses Iodised Salt. Utilising non-Iodised salt for human consumption is prohibited.{{Citation needed|reason=Cannot find an easy-to-reach source for this info|date=August 2021}} Salt costs about US$0.27 a kilo.<ref>{{Cite web|title=Iodine Global Network (IGN) - Price differential hampers iodized salt use in Nepal|url=https://www.ign.org/price-differential-hampers-iodized-salt-use-in-nepal.htm|access-date=2021-06-12|website=www.ign.org|archive-date=2021-09-27|archive-url=https://web.archive.org/web/20210927134521/https://www.ign.org/price-differential-hampers-iodized-salt-use-in-nepal.htm}}</ref>

===Philippines=== On December 20, 1995, Philippine President Fidel V. Ramos signed Republic Act 8172: An Act for Salt {{notatypo|Iodiz|ation}} Nationwide (ASIN).<ref>{{Cite web|url=https://www.officialgazette.gov.ph/1995/12/20/republic-act-no-8172/|title=Republic Act No. 8172|publisher=Official Gazette of the Republic of the Philippines}}</ref> However, local production of non-iodised salt continues. ===Romania=== According to the 568/2002 law signed by the Romanian parliament and republished in 2009, since 2002 iodised salt has been 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 iodisation process has to ensure a minimum of 30mg iodine/kg of salt.<ref>Sustainable Prevention of Iodine Deficiency and Achievement of Optimal Iodine Nutrition – Romania http://www.ign.org/cm_data/Poster_Romania.pdf {{Webarchive|url=https://web.archive.org/web/20220425070603/https://www.ign.org/cm_data/Poster_Romania.pdf |date=2022-04-25 }}</ref><ref>DECISION no. 568 of 5 June 2002 (republished) https://legislatie.just.ro/Public/DetaliiDocument/36611</ref>

===South Africa=== The South African government instructed that all salt for sale would be iodised after December 12, 1995.<ref>[http://www.cerebos.co.za/IodationHints.aspx Health Hints], Cerebos {{webarchive |url=https://web.archive.org/web/20080325033408/http://www.cerebos.co.za/IodationHints.aspx |date=March 25, 2008 }}</ref><ref>[http://cat.inist.fr/?aModele=afficheN&cpsidt=1732067 Impact after 1 year of compulsory iodisation on the iodine content of table salt at retailer level in South Africa] {{Webarchive|url=https://web.archive.org/web/20110324085704/http://cat.inist.fr/?aModele=afficheN&cpsidt=1732067 |date=2011-03-24 }}, 1999, vol. 50, no. 1, pp. 7–12 (12 ref.), ''International journal of food sciences and nutrition'' ISSN 0963-7486</ref>

===Switzerland=== Switzerland was the first country to introduce iodised salt, in the world's first food fortification programme.

In the early 20th century, goitre was endemic in most Swiss cantons. Iodine was recognised to have an effect on goitre, but it was not until Heinrich Hunziker, a GP in Adliswil, argued that the necessary dose of iodine was minute (with larger amounts causing overdose issues), and another doctor, Otto Bayard, conducted successful experiments based on this idea, that the theory of goitre as iodine deficiency came to be accepted. Learning of Hunziker's theory, Bayard conducted experiments with iodised salt containing only tiny amounts of iodine in villages badly affected by goitre. The success of these led, starting in 1922, to the adoption of iodised salt throughout the Swiss cantons.<ref>{{cite magazine |last=Goodman |first=Jonah |date=30 November 2023 |title=A National Evil |url=https://www.lrb.co.uk/the-paper/v45/n23/jonah-goodman/a-national-evil |magazine=London Review of Books |location=London, United Kingdom |publisher= |access-date=6 December 2023}}</ref>

Today, iodised salt continues to be used in Switzerland, where historically endemic iodine deficiency has been eradicated.<ref name=swiss>{{cite magazine |author= |title=100 years of salt iodination in Switzerland |url=https://swissfederalism.ch/en/100-years-salt-iodination-switzerland/ |magazine=Swiss Federalism |location= |publisher= |date= |access-date=6 December 2023}}</ref>

===Syria=== In the late 1980s, a Syrian endocrinologist named Samir Ouaess conducted 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 cancelled the iodisation of salt as a result of economic problems related to economic sanctions.{{Citation needed|date=March 2024}}

===United Kingdom===

Iodised salt is not readily available in the UK, where table salt forms a low proportion of salt consumed and there exists a conflict of interest with the salt-reduction campaign, which aims to reduce salt consumption further still.<ref>{{cite journal |doi=10.1017/S1368980012005496 |title=Availability of iodised table salt in the UK – is it likely to influence population iodine intake? |date=2014 |last1=Bath |first1=Sarah C. |last2=Button |first2=Suzanne |last3=Rayman |first3=Margaret P. |journal=Public Health Nutrition |volume=17 |issue=2 |pages=450–454 |pmid=23324480 |pmc=10282266 }}</ref>

UK milk had historically provided an alternative avenue for iodine intake, for which it is indirectly fortified through cattle feed. Iodisation of cattle feed was originally started in the 1930s to improve cow health. Iodophor disinfectants used in milking parlours also serve as a source of iodine for cows. Subsequent dairy promotion programmes increased the population's milk consumption, creating an "accidental public health triumph" by increasing the population's iodine consumption and nearly eliminating goitre.<ref name=uk-gone-sour>{{cite journal |last1=Woodside |first1=Jayne V. |last2=Mullan |first2=Karen R. |title=Iodine status in UK–An accidental public health triumph gone sour |journal=Clinical Endocrinology |date=April 2021 |volume=94 |issue=4 |pages=692–699 |doi=10.1111/cen.14368|pmid=33249610 }}</ref> However, several factors threaten this triumph: 2005 limits on iodine content of animal feed, organic milk (which contains lower amounts of iodine<ref>{{cite journal |doi=10.1017/S0007114511003059 |title=Iodine concentration of organic and conventional milk: Implications for iodine intake |date=2012 |last1=Bath |first1=Sarah C. |last2=Button |first2=Suzanne |last3=Rayman |first3=Margaret P. |journal=British Journal of Nutrition |volume=107 |issue=7 |pages=935–940 |pmid=21781365 |s2cid=14544257 |doi-access=free }}</ref> because of restrictions on mineral additions<ref name=uk-gone-sour/>), and an overall reduction in milk intake. Several studies between 1995 and 2020 have found iodine deficiency in British teenagers and pregnant women.<ref name=uk-gone-sour/>

===United States=== Iodised salt is not mandatory in the United States, but it is widely available.

In the early 20th century, goitres were especially prevalent in the region around the Great Lakes and the Pacific Northwest.<ref>{{cite journal | year = 1987 | title = When It Rains It Pours: Endemic Goiter, Iodized Salt, and David Murray Cowie MD | journal = American Journal of Public Health | volume = 77 | issue = 2| pages = 219–229 | doi = 10.2105/AJPH.77.2.219 | pmc = 1646845 | pmid = 3541654 | author = Markel Howard }}</ref>{{rp|220}} David Murray Cowie, a professor of paediatrics at the University of Michigan, led the United States 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.<ref name="pmid17796701">{{cite journal | author = McClure RD | title = Goiter Prophylaxis with Iodized Salt | url = https://archive.org/details/sim_science_1935-10-18_82_2129/page/370 | journal = Science | volume = 82 | issue = 2129 | pages = 370–371 |date=October 1935 | pmid = 17796701 | doi = 10.1126/science.82.2129.370 | bibcode = 1935Sci....82..370M }}</ref> By the fall of 1924, Morton Salt Company began distributing iodised salt nationally.

A 2017 study found that introducing iodised salt in 1924 raised the IQ of one-quarter of the population most deficient in iodine.<ref name="Journal of the European Economic Association-2017">{{Cite journal|last1=Feyrer|first1=James|last2=Politi|first2=Dimitra|last3=Weil|first3=David N.|date=2017|title=The Cognitive Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States|url=https://econpapers.repec.org/article/oupjeurec/v_3a15_3ay_3a2017_3ai_3a2_3ap_3a355-387..htm|journal=Journal of the European Economic Association|volume=15|issue=2|pages=355–387|doi=10.1093/jeea/jvw002|pmid=31853231|pmc=6919660}}</ref> These findings "can explain roughly one decade's worth of the upward trend in IQ in the United States (the Flynn effect)".<ref name="Journal of the European Economic Association-2017" /> The study also found "a large increase in thyroid-related deaths following the countrywide adoption of iodised salt, which affected mostly older individuals in localities with a high prevalence of iodine deficiency" between 1910–1960, a high short-term price for iodisation's long-running benefits.<ref name="Journal of the European Economic Association-2017" />{{efn|"Individuals in whom the chronic iodine deficiency has induced thyroid hyperplasia and goitre with autonomous thyroid follicular cells may respond to excessive intake with resultant hyperthyroidism."<ref name=uk-gone-sour/> A similar short term increase in deaths happened in the UK with the (unintentional) iodisation of milk, peaking in 1931–1940.<ref>{{cite journal |last1=Phillips |first1=D I |title=Iodine, milk, and the elimination of endemic goitre in Britain: the story of an accidental public health triumph. |journal=Journal of Epidemiology & Community Health |date=1 August 1997 |volume=51 |issue=4 |pages=391–393 |doi=10.1136/jech.51.4.391|pmid=9328545 |pmc=1060507 |bibcode=1997JECH...51..391P }}</ref>}} 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 iodised salt.<ref name=BI72213>{{cite news|title=How Adding Iodine To Salt Resulted In A Decade's Worth Of IQ Gains For The United States|url=https://www.businessinsider.com/iodization-effect-on-iq-2013-7|access-date=July 23, 2013|newspaper=Business Insider|date=July 22, 2013|author=Max Nisen}}</ref>

A 2018 paper found that the nationwide distribution of iodine-fortified salt increased incomes by 11%, labour 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 iodisation."<ref>{{Cite journal|last1=Adhvaryu|first1=Achyuta|last2=Bednar|first2=Steven|last3=Molina|first3=Teresa|last4=Nguyen|first4=Quynh|last5=Nyshadham|first5=Anant|date=2019-03-04|title=When It Rains It Pours: The Long-run Economic Impacts of Salt Iodization in the United States|journal=The Review of Economics and Statistics|volume=102|issue=2|pages=395–407|doi=10.1162/rest_a_00822|issn=0034-6535|hdl=10986/31273|s2cid=67876468|hdl-access=free}}</ref>

==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 is made for producing the brine to be used in pickling vegetables and other foodstuffs. Contrary to popular assumptions, however, iodised salt affects neither colour, taste, nor consistency of pickles.<ref>{{cite journal|journal=Eastern Mediterranean Health Journal|title=Possible effects of iodized salt on the taste, colour and consistency of traditional pickles|first1=Osama|last1=Badran|first2=Wisam|last2=Qaraqash|first3=Sana|last3=Gamah|url=https://www.emro.who.int/emhj-volume-2-1996/volume-2-issue-2/article5.html|access-date=2020-09-24}}</ref>

Processed food from the US almost universally does not use iodised salt,<ref>{{cite web |title=Office of Dietary Supplements - Iodine |url=https://ods.od.nih.gov/factsheets/Iodine-Consumer/ |website=ods.od.nih.gov |language=en}}</ref> raising concerns about possible deficiency.<ref>{{cite web |title=Iodine Is Important and You May Not Be Getting as Much as You Think |url=https://columbiasurgery.org/news/iodine-important-and-you-may-not-be-getting-much-you-think |website=Columbia Surgery }}</ref> On the other hand, processed food from Thailand contribute sufficient iodine to most of the population.<ref>{{cite journal |last1=Chotivichien |first1=Saipin |last2=Chongchaithet |first2=Nuntaya |last3=Aksornchu |first3=Pattamaporn |last4=Boonmongkol |first4=Nuntachit |last5=Duangmusik |first5=Pattama |last6=Knowles |first6=Jacky |last7=Sinawat |first7=Sangsom |title=Assessment of the contribution of industrially processed foods to salt and iodine intake in Thailand |journal=PLOS ONE |date=6 July 2021 |volume=16 |issue=7 |article-number=e0253590 |doi=10.1371/journal.pone.0253590 |pmid=34228736 |pmc=8259997 |bibcode=2021PLoSO..1653590C |doi-access=free }}</ref>

==Fortification of salt with other elements== thumb|Iodised salt with folic acid and fluorine. The folic acid gives a light yellow color to the salt.

===Double-fortified salt (DFS)=== Salt can also be double-fortified with iron and iodine.<ref>Diosady LL and Mannar MGV. [http://chem-eng.utoronto.ca/~diosady/sltdbl.html Double fortification of salt with iron and iodine.] {{Webarchive|url=https://web.archive.org/web/20110813121825/http://chem-eng.utoronto.ca/~diosady/sltdbl.html |date=2011-08-13 }}, 2000, University of Toronto, Department of Chemical Engineering, The Pages of Professor L.L. Diosady</ref> The iron is microencapsulated with stearin to prevent it from reacting with the iodine in the salt. 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.<ref>{{cite journal |last1=Andersson |first1=Maria |last2=Thankachan |first2=Prashanth |last3=Muthayya |first3=Sumithra |last4=Goud |first4=Ramakrishna B |last5=Kurpad |first5=Anura V |last6=Hurrell |first6=Richard F |last7=Zimmermann |first7=Michael B |title=Dual fortification of salt with iodine and iron: a randomized, double-blind, controlled trial of micronized ferric pyrophosphate and encapsulated ferrous fumarate in southern India |journal=The American Journal of Clinical Nutrition |date=1 November 2008 |volume=88 |issue=5 |pages=1378–1387|pmid=18996875 |doi=10.3945/ajcn.2008.26149 |doi-access=free}}</ref>

Adding iron to iodised 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.<ref>[http://www.micronutrient.org/CMFiles/What%20we%20do/New%20Solutions%20-%20Double%20Fortified%20Salt/DFS-Tech-Breakthrough-to-alleviate-I&IDD-around-the-world.pdf Double Fortification of Salt: a Technical Breakthrough to Alleviate Iron and Iodine Deficiency Disorders Around the World. The Micronutrient Initiative.] {{webarchive|url=https://web.archive.org/web/20110725051037/http://www.micronutrient.org/CMFiles/What%20we%20do/New%20Solutions%20-%20Double%20Fortified%20Salt/DFS-Tech-Breakthrough-to-alleviate-I%26IDD-around-the-world.pdf |date=2011-07-25 }}, Micronutrient Initiative.</ref>

===Fluoridated salt=== In some countries, table salt is treated with potassium fluoride to enhance dental health.<ref name=Aigueperse>{{Ullmann|doi=10.1002/14356007.a11_307|title=Fluorine Compounds, Inorganic|year=2000|last1=Aigueperse|first1=Jean|last2=Mollard|first2=Paul|last3=Devilliers|first3=Didier|last4=Chemla|first4=Marius|last5=Faron|first5=Robert|last6=Romano|first6=René|last7=Cuer|first7=Jean Pierre|isbn=3527306730}}</ref>

===Diethylcarbamazine=== In India and China, diethylcarbamazine has been added to salt to combat lymphatic filariasis.<ref>[https://web.archive.org/web/20070712165432/http://www.who.int/bulletin/volumes/85/7/06-034108/en/index.html] WHO: Unfulfilled potential: using diethylcarbamazine-fortified salt to eliminate lymphatic filariasis</ref>

==See also== * Basil Hetzel * Enriched flour, an analogous function to "enriched salt" * History of salt * Lugol's iodine * Water fluoridation, a similar public health intervention * Food fortification

==Notes== {{notelist}}

==References== {{reflist|25em}}

==Further reading== {{refbegin}} * [https://web.archive.org/web/20120217203548/http://www.access.gpo.gov/nara/cfr/waisidx_05/21cfr101_05.html 21 CFR] 101.9 (c)(8)(iv) * [http://encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=364 Newton County – Encyclopedia of Arkansas] {{refend}}

{{portal bar|Food}} {{authority control}} Category:Edible salt Salt Category:History of salt Category:Endocrinology Category:Human nutrition