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Iodine Deficiency in the US

An article by Sarah Anne Wright appearing on page A3 of the Boston Globe on 7/22/2002.

US iodine consumption declining

Salt intake of some is low on key nutrient that blocks thyroid

Columbia, MO – Researchers have been monitoring how much iodine Americans consume because the amount has fallen in the last 25 years, although it generally remains within the level needed for good health.

The researchers say the decline in average consumption of iodine, which a survey released last year found had leveled off, appears to be the result of changes in eating habits and food production. The trace element is readily available in iodized salt, but Americans have been getting more of their salt from designer table salts and processed foods that do not contain iodine.

A risk exists that a small portion of the US population, arguably the most well-fed nation in the world, has not been getting sufficient iodine. Health officials monitor iodine consumption because lack of the micronutrient has serious health consequences.

A swollen neck, or goiter, brought on by enlargement of the thyroid gland has historically been the most visible sign of low iodine-intake. The thyroid gland is essential for maintaining regular body metabolism, growth, and development.

Other irreversible health problems can be caused by a lack of iodine, including dwarfism, mental and physical retardation, miscarriages, and a pronounced decrease in the intellectual ability of infants. Health researchers combating iodine disorder deficiencies (IDD) have been trying to raise public awareness of these other harmful effects.

“You show people posters of goiters, cretins and other conditions of IDD, and the one they always remember is the big neck,” said Jack Ling, a professor public health communications at Tulane University and chairman of the International Council for Control of Iodine Deficiency Disorders, a nonprofit group formed in 1985.

In the National Health and Nutrition Examination Survey of 1995, the Centers for Disease Control and Prevention found that iodine concentrations had declined in the past 20 years by half. The drop was unexpected and unexplained. The most recent survey, announced last August, found that the level stabilized at slightly above what it was in 1995. The results of a new survey are expected later this year.

The 1995 results showed 12 percent of Americans surveyed had low iodine concentrations, compared with just 3 percent in 1974. The World Health Organization considers a population iodine-deficient when at least 20 percent of the population is deficient.

The upper Midwest and Great Lakes regions were once known as the “Goiter Belt” because of the prevalence of enlarged thyroid glands that gave the afflicted visibly swollen necks. The goiter problem was widely noted during World War I when Army physicians recognized the condition in recruits.

Regional clusters of goiters were usually in mountainous areas, or inland regions where iodine and other highly soluble minerals in soils had diminished, possibly because of floods and glacier melts eons ago.

In 1924, US salt companies iodized table salt in an effort to eliminate iodine deficiencies. Because it is steadily consumed in small amounts, salt was considered the best carrier for iodine. Worldwide, people consume about 10 grams of salt a day, giving the average person an ample amount of iodine. Iodizing salt is inexpensive, costing just 4 cents a person per year. Two grams of salt contains about the daily recommended dose of iodine for an adult.

The country no longer has a goiter belt, but the South has a higher rate of thyroid disease and goiters, possible due to an older population and higher rates of smoking.

Thiocyanate, a chemical in cigarette smoke, blocks the thyroid’s ability to take up iodine, according to a Danish study published in the February issue of Archives of Internal Medicine. The researchers reported that almost half of clinically detectable goiters they studied in an iodine-deficient area were related to smoking.

Iodizing salt is now mandatory in 120 countries, including Canada and parts of Mexico. It is voluntary in the United States.

“In the US, they’ve left it to the people,” says Arie Hoogendoorn, director of scientific affairs for Morton Salt. “It was felt that the disease was under control.”

Hoogendoorn remembers attending a lot of meetings in the 1970s and 1980s where participants discussed the possibility that there might be too much iodine in American diets. During those decades, iodine was used in cattle feed, as a sanitizer for dairy cow udders, and as an agent in commercial baking.

These industrial processes have changed, leaving less iodine in the food supply.

It is estimated that about 70 percent of Americans consume iodized salt. Most salt sold in supermarkets is iodized. But some products, what Hoogendoorn refers to as “fancy salts” – salt substitutes, sea salt and kosher salt – are not iodized. Further, sales of round boxes of salt have been in steady decline since World War II.

Of all the food salt in the United States, about 70 percent is sold to food processors, including fast-food restaurants. “Virtually none of it is iodized,” said Dick Hanneman, president of the Salt Institute.

As Americans move away form home-cooked meals and consume more processed or fast food, a small percentage may be getting plenty of salt but not much iodine.

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