A growing iodine deficiency could bring back America's goitre.
"A century ago much of northern America was known as the goitre belt," said The Economist.
A lack of natural iodine in the soil and water led to the "characteristic neck swellings" – enlarged thyroid glands. In the 1920s between 70% and 100% of schoolchildren in Michigan, Minnesota and Wisconsin reportedly had goitres.
But after iodine supplements were shown to help prevent them, it was added to table salt (a ubiquitous food product that could quickly reach large parts of the population). The iodised salt was rolled out across the US in 1924, and by the 1940s goitres had all but "vanished". Now, thanks to complacency, changing diets and a "lack of public health education", iodine deficiency is making a comeback.
Iodine helps the thyroid produce hormones that regulate the metabolism, crucial for nutrition and development. A deficiency of it in pregnant women often leads to "children with a severely diminished IQ" and other cognitive impairments, said The Washington Post. It is the leading global cause of "preventable intellectual disability".
Iodine deficiency has "re-emerged" among pregnant Americans over the past 15 years, said Healio. A 2021 study found that about a quarter of them had below the recommended level of iodine.
Only about half the table salt sold in the US is iodised, while processed foods, which make up an increasing majority of salt in people's diets, are generally free of the mineral. Dairy, meat and white fish are key sources of iodine, but decreasing demand, alongside the growing popularity of dairy milk substitutes like oat milk, "may cause a further decline". Less than a third of dairy alternatives are iodised.
But this problem extends far beyond America. A "ground-breaking" study published in The Lancet last month revealed a "shocking truth", said the Daily Express. More than 5 billion people – 68% of the world's population – weren't getting enough iodine, making it a "silent health epidemic". | 
