Our obsession with salt is damaging our health

When I was at university, I had a biology lecturer who was obsessed with iodine and whose mission in life was to solve global dietary deficiencies. He encouraged us to always use iodized salt and told us that it raised the IQ of entire nations and was one of the greatest public health inventions of all time. I still hear his voice in my head every time I’m in the salt section of the supermarket.

In recent years, however, it has become more and more difficult for me to find even iodized salt on the shelves. Over time, it was supplanted by fancy-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 profoundly cold. This makes me wonder: are we about to undo all the benefits that come from this non-consumable 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 regulate fetal brain growth. Even mild to moderate defects in utero are estimated to reduce intelligence by 0.3 to 13 IQ points. Iodine is also important in childhood to support brain development and thyroid function. Case reports describe extremely picky eaters who are short for their age, struggle in school, and are constantly tired because they are iodine deficient. 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 attempt to take in more iodine.

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

In 1922, Switzerland was the first country to introduce iodized salt, which was made by adding a small amount of extra iodine to regular table salt. The goitre practically disappeared in a short time, the children were taller and received an “IQ injection”, as economist Dimitra Politi described it. This meant that more and more of them completed high school and went on to earn college degrees.

In 1924, Michigan also made iodized salt available, and other parts of the US and many other countries soon followed. Its introduction was considered one of the factors that drove the worldwide increase in IQ observed during the 20th century. Rarely has such a cheap invention had such extraordinary advantages. “For 5 cents per person per year, you can make an entire population smarter than before,” said endocrinologist Gerald Burrow. The New York Times in 2006.

However, now that goiter is long forgotten, iodized salt is suffering a popularity crisis. For one thing, it cannot compete with the beauty of pink Himalayan flakes. Some of the trendy non-iodized salts explicitly advertise their lack of iodine additives and suggest that they may somehow be bad for you. I know parents who deliberately avoid giving iodized salt to their children because they fear the chemical additives (even though iodine is a natural substance).

At the same time that people are using less iodized salt in the home kitchen, we are also eating more processed foods and takeaways, which are usually made with non-iodized salt to prevent adverse reactions during processing. More and more people are becoming vegan or switching from cow’s milk to plant-based milk, further reducing iodine intake.

Because of these trends, a study published in November found that the proportion of Americans who don’t get enough iodine has doubled since 2001. More worryingly, the study found that 46 percent of pregnant women now have insufficient income.

The story is similar in the UK. The average iodine level measured in women of reproductive age is “now well below the threshold of adequacy,” according to a study published in January. And in Australia, 62 percent of pregnant and lactating women have insufficient iodine levels. (Although it should be noted that some places, such as parts of Japan, have the opposite problem with excessive iodine consumption, which comes with its own thyroid problems).

This has led public health experts to urge people in the US, UK and Australia to resume iodized salt to avoid damage to cognitive function and thyroid health and the recurrence of goiter.

Indeed, it is a strange time. The supplement industry is booming, and people are loading up on zinc, selenium, and ginkgo biloba pills to support their brain health, even though there’s little evidence to support any benefits. In contrast, iodine supplements and salts are overlooked, even though many people have legitimate iodine deficiencies that carry real risks. I can’t wrap my head around it.

But fashion or not, I’ll keep rummaging through the supermarket shelves for iodized salt, still too scared of what my old teacher would think if I went for the pretty pink flakes.

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