Why is Iodine Important?

Reader Zoe writes:

I’ve been interested to read some of the comments on the subject of iodine and salt. I’ve always noticed that salt is “iodized” but have wondered why that’s important. Can you go into the subject a little? I’d be interested to read more.

Zoe, you never have to prod me too much to delve into a topic like this. Since we’ve been flirting with various subjects related to diet and health this past week, it only makes sense. Commercially made table salt is iodized by law in the US. It’s natural to wonder why.

Iodine is an element that’s essential to human health. It’s used by the thyroid gland to manufacture two very important hormones by the names of thyroxine and triiodothyronine. Together these hormones help regulate our metabolism. The thyroid gland in the neck is the organ responsible for trapping the miniscule amount of iodine that the human body needs. As long as iodine intake remains more or less constant, the thyroid hums along, quietly doing its job.

The trouble starts when the amount of iodine we take in decreases. In response the cells in the thyroid gland increase in size in an attempt to capture more of what they need. Critically low levels of iodine in the diet thus lead to a dramatic swelling of the thyroid gland. This neck swelling is the condition known as “goiter”. And while it’s mostly just unsightly, the condition also causes profound fatigue, coldness in the body and in extreme cases brain damage.

The main source of iodine on planet Earth is the sea. Thus, eating a steady diet of salt water fish is all it really takes to give your body the iodine it needs. Remarkably the body needs so little iodine to function it’s possible — provided you live right near the ocean — to breathe in enough iodine to sustain your metabolism.

Of course most people don’t live right near an ocean, and as a result are at risk for goiter. In the United States prior to the discovery of the link between iodine and goiter, there was a so-called “goiter belt” that extended from the Pacific Northwest all through the Great Lakes. In the early 20th century, up to 40 percent of the people who lived in that region suffered from goiter in some form. Thus is was a great relief when state and federal governments teamed up with salt companies in 1924 to deliver iodine to the American people via table salt. It was the world’s first “functional food.”

The fact that so many people these days — notably foodies — are opting for non-iodized specialty salts is a bit alarming. For people who are aware that fleur-de-sel and other high-end salts lack iodine, and can remember to take regular iodine supplements, it’s not an issue. However most of us alive today don’t remember iodine-related health issues like goiter and so don’t appreciate the boon that is iodization.

The bright note here is that commercial food packagers use standard iodized salt in their products. That being the case, if foodies can remember to eat a fair amount of cheese or the odd bag of Doritos, they’ll probably get all the iodine they need.