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The miracle of iodine

How 10 cents and some table salt can raise IQs in the developing world.

China salt 2011 04 20Enlarge
Bags of salt lie on the ground prior to being transported, primarily for domestic use in China, in Bayinwusu Township of Hangjin Banner, Inner Mongolia Autonomous Region, northern China. (Stringer/AFP/Getty Images)

BANGKOK, Thailand — In America, it’s the Appalachian hilltops. In China, it’s Jixian village, once deemed too backward for army recruitment or even marriage to outsiders.

In Australia, it’s the remote island of Tasmania, the butt of a million hillbilly jokes. What do all three areas have in common? They were, historically, abundant with cretins.


“People used to make jokes, cruel jokes, about people from the hills,” said endocrinologist Cres Eastman, an Australian and vice-chairman of the International Council for the Control of Iodine Deficiency Disorders, or ICCIDD.

“But a lot of the so-called stupidity, which they thought was genetic, was clearly not so,” he said. “It was environmental.”

“A person has the right to enough iodine so their brain can develop and they can be educated.”
~Cres Eastman, vice-chairman of the International Council for the Control of Iodine Deficiency Disorders

A cretin, medically speaking, is a person born mentally handicapped and often physically deformed from an undernourished thyroid gland.

A cretin is born deprived of iodine, an element commonly absorbed through milk, seafood and crops grown in iodine-rich soil. By lacing table salt with small amounts of iodine, cretinism has been virtually eradicated in the industrialized world.

In recent decades, a push by the United Nations and the World Health Organization has brought most of the developing world along too. Roughly 70 percent of the world now eats iodized salt, the biggest preventer of cretinism, compared to just 20 percent in 1990.

But while cretins have become rarer, too little iodine in a fetus or young child’s system still causes a more subtle problem: diminished IQs.

Late last year, Thailand’s health minister, Jurin Laksanawisit, went public with a troubling study indicating Thai kids’ IQs averaged a lowly 91 points. A widely accepted average among developed countries is 104 and the World Health Organization’s suggested range is 90 to 110.

The problem, Jurin said, was low consumption of iodine.

Figures included in the ICCIDD report suggest the IQs of Thai children actually dropped between 1997 and 2002. In Thailand’s mostly urban central region, for example, the average child’s IQ dropped from 92 to just under 89 points during that span.

The culprit, Eastman said, is iodine deficiency in a less blatant guise.

In decades past, iodine-deprived regions were marked by mentally disabled people with deformities. Goiters ballooned from their necks, brought on by swollen, malnourished thyroid glands.

Touring art galleries in Tasmania, Eastman said, will reveal paintings of “all the grand ladies of the 1800s who had their portraits done ... and it’s amazing that most have goiters.”

But simply adding iodine to edible salt — often at a cost of roughly 10 cents per person per year, according to the U.N. — can virtually eliminates cretinism and lift IQs. The World Bank has called iodine supplements the most cost-effective health intervention on the planet.

A joint effort to iodize the world’s salt, led by the World Bank and the United Nations Children’s Fund, has largely ended iodine deficiency in many countries. According to their research, a lack of iodine can cost a developing child’s IQ between 10 and 15 points.

Still, 38 million babies in the developing world — more than the population of Canada — are born each year with “lifelong brain damage” because of a lack of iodine, according to the U.N.

Some appear perfectly healthy. “The loss of IQ is much more subtle than having a big goiter on your neck,” Eastman said.

The setback in Thailand and other parts of Asia is weak government regulation, said France Begin, Asia-Pacific regional nutrition adviser with the U.N. Children’s Fund.

Though Thailand’s most popular brands of table salt are iodized, a number of regional producers don’t iodize. “There’s also fish sauce, which a lot of people rely on in their diet for this salty taste,” Begin said. “Countries like Cambodia, Vietnam and China, they don’t consume as much white table salt.”

The fish sauce phenomenon helps explain why even well-off Thais are iodine deficient. Only 68 percent of the wealthiest segments of society are “adequately iodized,” said the ICCIDD report, compared to just 23 percent of the poorest.

But iodizing fish sauce, Begin said, is just as easy as iodizing salt. “It’s a no brainer,” she said.