How Adding Iodine To Salt Resulted In A Decade’s Worth Of IQ Gains For The United States


Iodized salt is so ubiquitous that we barely notice it. Few people know why it even exists. Iodine deficiency remains the world’s leading cause of preventable mental retardation. According to a new study, its introduction in America in 1924 had an effect so profound that it raised the country’s IQ.

new NBER working paper from James Feyrer, Dimitra Politi, and David N. Weil finds that the population in iodine-deficient areas saw IQs rise by a full standard deviation, which is 15 points, after iodized salt was introduced.

Since one quarter of the population lived in those areas, that corresponds to a 3.5 point increase nationwide. We’ve seen IQs go up by about 3 points every decade, something called the Flynn effect, so iodization of salt may be responsible for a full decade’s worth of increasing IQ in the U.S.

If a mother is iodine deficient while she’s pregnant, the cognitive development of the fetus is impeded, and the effects are irreversible. To this day, the World Health Organization estimates that nearly 50 million people suffer some kind of mental impairment related to iodine deficiency.

Before iodized salt, people were deficient based almost entirely on geography, whether the water and soil in their area had enough of the micronutrient. Diseases resulting from the deficiency, most commonly goiter, or swelling of the thyroid, were extremely common.

The differences by geography were vast, making the effects easy to isolate. Seawater, for example, is rich in iodine, but glaciers depleted iodine rich soil in places like Michigan:

Figure 6


The mental impacts were unknown, the program was started to fight goiter, so these effects were an extremely fortunate unintended side effect.

To figure out the effects, the researchers used the data from the Army General Classication Test (AGCT) given to people who enlisted during World War 2. That covers a wide group of men born precisely at the time iodized salt was introduced (1920-1927), which allowed comparison of low and high iodine areas.

The Air Force received enlistees who scored significantly higher on the AGCT, and the number of men who scored well and went to the Air Force from low iodine areas dramatically increased after iodized salt was introduced. The estimates of intelligence increases are based on that data.

Here’s the author’s chart that shows the boost in Air Force enlistment rates:NBER

Figure 18

Despite these positive effects, there were some negative side effects as well. People who suffer long-term iodine deficiency can actually end up with from hyperthyroidism when it’s introduced to their diet, so deaths spiked for a few years. However, the aggregate effect has been extremely positive.


Iodized SaltWorthed Of IQ Gains For USAIodization Effect On IQ


The IQ mineral

The IQ mineral

Unless you were a regular at the sushi bar or ate fish twice a week it used to be hard to get enough iodine in your diet – but there are signs that putting iodised salt in our bread has made this easier. Nearly four years ago concerns about iodine deficiency led to bread being fortified with iodised salt. Measures of iodine concentrations in the urine of school children in Tasmania show that iodine intake is higher now than before fortification began.

But we’re not out of the woods yet – there are also signs that pregnant women may not get enough iodine to ensure the optimal brain development of their unborn babies, says Associate Professor Karen Charlton of Wollongong University’s School of Health Sciences. Research by Charlton and her team suggests that many pregnant women may be low in this mineral which is essential for an unborn baby’s developing brain.



While adults need 150 mcg of iodine daily, the need for this mineral jumps by 50 per cent during pregnancy and breastfeeding – and that’s more than a few slices of bread with iodised salt can deliver. But although the National Health and Medical Research Council recommends iodine supplements for women who are pregnant or planning to be, Charlton says the message isn’t loud enough.

“In surveys we’ve done in the Illawarra region, about 40 per cent of women attending public antenatal clinics said they don’t take iodine supplements. Women aren’t aware how important iodine is in pregnancy and my feeling is that many women aren’t given advice to take a supplement,” says Charlton. “But new research has linked a low iodine intake in pregnancy with a reduced IQ in children.”

One UK study published in the medical journal The Lancet in May, reported that children of women with  a mild to moderate iodine deficiency in pregnancy had lower scores for verbal IQ, reading accuracy and reading comprehension, compared to children born to women with adequate iodine intakes. A study from Tasmania’s Menzies Research Institute has also attributed better scores on the NAPLAN school test in nine-year-olds to differences in iodine intakes of their mothers in pregnancy.

“There are many factors affecting a child’s intellectual development, including childhood experiences and the parents’ education level – but these studies controlled for other factors and still found an impressive association with iodine intake in pregnancy,” Charlton says.


Most adults should be able to get enough iodine with three slices of bread (unless it’s organic bread which isn’t required to have iodised salt) and two to three serves of dairy food daily, a couple of serves of fish or seafood weekly and sushi now and again, Charlton says. But this may not be enough for pregnant women – especially those who don’t eat much bread or are wary of eating fish in pregnancy.

How did we get to be low on iodine to begin with? There are a few reasons – low iodine levels in soil, less use of iodine-based cleaning products in the dairy industry which once boosted the iodine content of our dairy food, the fact that we now eat so much processed food which uses non-iodised salt and that we tend to use non-iodised salt at home.

If you’re pregnant or breastfeeding Karen Charlton suggests a multivitamin containing 150mcg of iodine – although women with a thyroid problem should talk to their doctor because too much iodine can exacerbate some thyroid conditions.

Can a healthier iodine intake in childhood make up for a shortfall in the womb?

“No – most brain development occurs during pregnancy,” explains Professor Cres Eastman, Asia Pacific regional co-ordinator for the International Council for Control of Iodine Deficiency Disorders. “But an adequate iodine intake is still important in childhood and children who don’t drink milk or eat bread – foods that are often the main  source of iodine in childhood – need a daily supplement of 100mcg of iodine.”

”Sebagian tanda orang yang berpegang pada amal, ialah berkurang harapannya kepada Allah ketika terjadi kesalahan-kesalahan.”-Mukadimmah Alhikam

Imam Ibnu ‘Atha’illah memulai kalam Hikmah nya yang pertama dengan mengajak kita untuk merenung kepada hakikat amal. Amal dapat dikatagorikan menjadi dua jenis, yaitu perbuatan dzahir dan perbuatan batin atau suasana hati berhubung dengan perbuatan zahir tersebut. Beberapa  orang dapat saja melakukan berbuatan dzahir, tapi suasana hati antara mereka berbeda-beda. Kesan amalan zahir kepada hati berbeda-beda antara seorang dengan orang  lain. Jika amal dzahir itu mempengaruhi suasana hati, maka hati itu dikatakan bersandar pada amalan dzahir. Begitu pula, jika hati dipengaruhi oleh amalan hati, maka hati tersebut juga dapat dikatakan bersandar pada amal, meskipun hanya amalan batin.

Hati yang bebas dari bersandar pada amal dzahir maupun  amal batin adalah hati yang menghadap kepada Allah Swt dan menggantungkannya kepada Allah Swt tanpa membawa-bawa sedikitpun amalannya, baik amal dzahir maupun amal batin, serta menyerahkan sepenuhnya kepada Allah Swt tanpa ada secuil takwil atau tuntutan. Hati yang demikian  tidak menjadikan amal (baik zahir maupun batin) sebanyak apapun sebagai alat tawar menawar dengan Allah  untuk mendapatkan sesuatu. Amalnya tidak dijadikan “perantara” antara diri nya dengan Allah. Orang yang seperti ini tidak membatasi kekuasaan dan kemurahan Tuhan untuk tunduk kepada perbuatan manusia. Allah yang  Maha Berdiri Dengan Sendiri berbuat sesuatu menurut kehendak-Nya tanpa dipengaruhi oleh siapapun atau sesuatu apapun.

Apa saja yang mengenai Allah Swt adalah mutlak, tidak ada batasannya. Karena itu, Orang yang arif tidak menjadikan amalnya sederajat untuk mengungkung ketuhanan Allah atau memaksa Ketuhanan Allah Swt berbuat sesuatu menurut perbuatan mahluk. Tidak pernah terjadi Allah Swt mengikuti perkataan dan perbuatan seseorang atau sesuatu.

Sebelum menjadi seorang yang ‘arif, hati manusia cenderung berhubung erat  sekali dengan amalanya, baik yang dzahir maupun yang batin. Seseorang yang kuat bersandar pada amal dzahir akan mencari faedah atau manfaat keduniawian, sedang orang yang bersandar pada amalan batin akan mencari faedah atau manfaat ukhrawi. Kedua manusia ini sangat percaya bahwa amalnya lah yang akan menentukan apa yang akan mereka peroleh baik didunia maupun diakhirat. Kepercayaan yang demikian kadang-kadang membuat manusia hilang atau kurang bergantung  kepada Allah. Kebergantungan mereka hanyalah kepada amalan semata-mata ataupun jika mereka bergantung kepada Allah s.w.t, kebergantungan itu bercampur dengan keraguan.

Setiap orang dapat  memeriksa apakah kebergantungannya  kepada Allah Swt kuat atau lemah? Kalam pertama Al hikam ini memberi petunjuk mengenai hal ini. Ketika  seseorang melakukan maksiat atau dosa, jika kesalahannya tesrsebut membuatnya berputus asa dari rahmat dan pertolongan Allah, itu tandanya orang tersebut sangat lemah sekali kebergantungannya kepada Allah Swt.

Firman Allah Swt : “Hai anak-anakku, pergilah kamu dan carilah berita tentang Yusuf dan saudaranya (Bunyamin), dan janganlah kamu berputus asa dari rahmat Allah. Sesungguhnya tiada berputus asa dari rahmat Allah, melainkan kaum yang kafir.”(Surah Yusuf (12) :Ayat 87 )

Ayat diatas menceritakan tentang seorang yang beriman kepada Allah Swt, yang menggantungkan segala-galanya kepada Allah Swt dalam kondisi apa dan bagaimanapun. Bergantung kepada Allah membuat hati tidak berputus asa, terutama dalam menghadapi berbagai persoalan hidup.

Dalam kehidupan, seringkali kita tidak mendapatkan apa yang kita inginkan, kita rencanakan dan kita usahakan. Kegagalan mendapatkan sesuatu yang diinginkan bukan berarti tidak menerima pemberian atau rahmat Allah s.w.t.  Selama seorang itu beriman dan bergantung kepada Allah, selama itulah Allah  melimpahkan rahmat-Nya.  Bagi orang yang beriman, apa pun yang ditetapkan yang Allah s.w.t  kepadanya  -termasuk dengan tidak memenuhi harapan dan keinginannya- pasti terdapat rahmat-Nya, walaupun dalam hal ini tidak sesuai dengan keinginan/ hajat orang tersebut.

Dengan keyakinan yang demikian, orang beriman akan  tabah menghadapi ujian hidup dan ia tidak sekali-kali berputus asa sebab ia yakin bahwa ketika ia menyandarkan semua perkara kepada Allah Swt tak ada satu hal pun yang menjadi sia-sia.

Orang yang demikian tidak lagi melihat kepada amalannya, walau begitu banyak amal yang telah dilakukannya namun, hatinya tetap melihat bahwa semua amalan tersebut adalah karena kurnia  Allah SWT kepadanya. Jika tidak karena taufik dan hidayah dari Allah s.w.t tentu tidak ada amal kebaikan yang dapat dilakukannya

Ali Imran 190-191

In the creation of the heavens and the earth and the alternation of the night and the day are signs for those of understanding (Ali Imran 190).

Who remember Allah while standing or sitting or [lying] on their sides and give thought to the creation of the heavens and the earth, [saying], “Our Lord, You did not create this aimlessly; exalted are You [above such a thing]; then protect us from the punishment of the Fire. ((Ali Imran 191).