The survey, whose unpublished results were presented last week to endocrinologists in Ramat Gan, found that 62 percent of school-age children and 85 percent of pregnant women have iodine levels below the World Health Organization minimum.

According to the researchers behind the survey, the numbers are among the highest in the world and signal a major national health problem likely related to Israel’s world-leading use of water desalination.

“We could be talking about a significant detriment across the population,” Dr. Aron Troen, a nutritional neuroscientist at the Hebrew University of Jerusalem who helped lead the survey, told JTA. “For anyone below the minimum level, you may loose 7 to 10 to 12 IQ points, which translates into a huge decrease in GDP due to reduced productivity.

“We are concerned that increased reliance on desalinated water in the Israeli food chain is contributing to iodine insufficiency in the population.”

Even mild iodine deficiency can limit intellectual development, and mild to moderate deficiency has been linked to decreased cognitive performance. In the womb or early childhood, iodine deficiency has been shown to impair brain development and in severe cases cause physical malformation, dwarfism and intellectual disability. Previous studies have found the children of iodine-deficient mothers perform much more poorly in school.

Researchers from Hebrew University, Maccabi Healthcare Service, Barzilai University Medical Center in Ashkelon and ETH Zurich in Switzerland collaborated on the survey, which analyzed urine samples from 1,0123 school-age children and 1,074 pregnant women. They found similar results among Israeli Arabs, secular Jews and Orthodox Jews.

From left, researchers Dov Gefel, Yaniv Ovadia, Aron Troen and Jonathan Arbelle (Courtesy of Hebrew University)

Based on their findings, the researchers called on the Israeli government to mandate the addition of iodine to salt or other foods, as do some 160 other countries, including the United States. They said the change would be easy, inexpensive and have potentially large public health benefits. In the meantime, Israelis can change their diets, including by seeking out iodized salt, which is hard to find in Israel.

“Individuals can improve their iodine status through increased consumption of iodine-rich foods such as milk, dairy and saltwater fish. They can also replace regular table salt with iodized salt,” said Yaniv Ovadia, the doctoral student and registered dietitian who performed the survey.

Israel was one of only a few countries to have never before gathered nationally representative data on its residents’ iodine levels. But Troen said “the trajectory” of his research suggests the problem has worsened in recent years and may be related to Israel’s pioneering use of water desalination, which removes iodine as well as other minerals. About half of the water Israelis consume is desalinated – a higher percentage than in any other country.

In a study last year, Troen and fellow researchers found a “surprisingly high” prevalence of insufficient iodine intake among the residents of the southern Israeli city of Ashkelon, where residents get much of their water from the local desalination plant. They also found a strong association with thyroid dysfunction among adults and evidence that the problem increased in the 2000s, as Israel was ramping up its water desalination program.

According to data from the Israel Center of Disease Control, self-reported use of thyroid medication among Israeli adults increased 63 percent between the Israeli National Health Interview Surveys of 2003-04 and 2007-10.

Troen said other potential explanations are Israelis’ increased consumption of processed foods and surprisingly low consumption of dairy products. He has started new research on the causes of iodine deficiency in Israel.