Iodized salt has become useless but many of us need to eat more iodine

When I was at university, I had a biology lecturer who was obsessed with iodine, and whose life’s work was to tackle global dietary deficiencies. He urged us to always use iodized salt and pointed out that it had increased the IQ of the entire nation and was one of the greatest public health inventions of all time. I still hear his voice in my head whenever I’m in the salt section of the supermarket.

However, in recent years, it has become difficult for me to even find iodized salt on the shelves. Over time, it has been filled with attractive looking Cornish sea salt crystals, Himalayan pink rock salt, smoked salt flakes and kosher salt. The few remaining containers of iodized salt come in drab packaging and look absolutely disgusting. This makes me wonder: Are we about to eliminate all the benefits we get from this simple food additive?

Iodine is an essential dietary mineral that the thyroid gland uses to make key hormones that regulate metabolism, growth, digestion, heart rate, and body temperature.

Getting enough iodine is especially important during pregnancy because thyroid hormones control fetal brain development. It has been estimated that even mild to moderate deficiencies in utero can result in a decrease in intelligence of 0.3 to 13 IQ points. Iodine is also important for supporting brain development and thyroid function during childhood. Case reports include people with very picky eaters, who are small for their age, struggle in school, and are tired all the time due to iodine deficiency. In children and adults, iodine deficiency can also lead to goiter – a swelling of the neck that occurs when the thyroid gland enlarges in an effort to take up more iodine.

Foods naturally rich in iodine include seaweed and seafood. Cow’s milk also contains iodine because it is often added to cattle feed, and iodine-based disinfectants are used to clean the udders and milking equipment of dairy cows. Fruits, vegetables and grains can absorb small amounts of iodine from the ground, but iodine levels in soil vary greatly. Switzerland and Michigan, once part of the “goiter belt” of North America, both have very low iodine in their soils. Historically, they had very high rates of goiter, with up to 70 percent of children in some Swiss towns affected.

In 1922, Switzerland was the first country to introduce iodized salt, made by adding a small amount of extra iodine to regular table salt. Within a short time, goitre almost disappeared, children grew taller and were given “an injection of IQ”, as the economist Dimitra Politi has described it. This means that more people finish high school and complete university degrees.

In 1924, Michigan also made iodized salt available, soon followed by other parts of the US and many other countries. Its introduction has been credited as a factor responsible for the increase in IQ worldwide during the 20th century. Seldom has such an inexpensive invention had such extraordinary benefits. The late endocrinologist Gerald Burrows explained, “For 5 cents per person per year, you can make the entire population smarter than ever before.” new York Times in 2006.

However, now that goiter has been long forgotten, iodized salt is suffering a popularity crisis. For one thing, it can’t compete with the beauty of the pink Himalayan pieces. Some trendy non-iodized salts specifically advertise the lack of iodine additives, hinting that they may be bad for you in some way. I know parents who deliberately avoid giving iodized salt to their children because they are concerned about chemical additives (even though iodine is a natural substance).

At the same time that people are using less iodized salt in home cooking, we are also eating more processed and takeaway foods, which are typically made with non-iodized salt to avoid unwanted reactions during processing. More people are becoming vegetarian or switching from cow’s milk to plant milk, further reducing iodine intake.

Because of these trends, a study published in November found that the proportion of Americans who are not getting enough iodine has doubled since 2001. Even more worryingly, the study found that 46 percent of pregnant women now get inadequate amounts of iodine.

The story is similar in Britain also. The average iodine level measured in reproductive-aged women is “now well below the threshold of sufficiency,” according to a study published in January. And in Australia, 62 percent of pregnant and breastfeeding women have inadequate iodine levels. (Although it should be noted that some places, such as parts of Japan, have the opposite problem of consuming too much iodine, which comes with thyroid problems).

This has led public health experts to urge people in the US, UK and Australia to switch back to iodized salt to avoid damage to cognitive and thyroid health and the re-emergence of goiter.

Truly, this is a strange time. The supplement industry is booming and people are taking zinc, selenium and ginkgo biloba pills to boost their brain health, even though there is little evidence to support any benefits. Conversely, iodine supplements and salt are being ignored despite many people having legitimate iodine deficiency, which poses real risks. I can’t wrap my head around it.

But fashionable or not, I would continue to wander around the supermarket shelves to find iodized salt, still very scared of what my old lecturer would think if I went for the pretty pink salt.