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Iodine: Are You Getting Enough?

Fish and seafood on Paleo

If your IQ is high enough to read these words, you have iodine to thank: this little-known mineral is essential for brain development in infancy, among several other crucial functions. But even though outright iodine deficiency is fairly rare in the developed world, it’s still a danger to be aware of – especially because the combination of a Paleo diet and the modern food environment can unintentionally create a dangerously low dietary iodine intake. So take a look at what iodine is, why you need it, and how to make sure you’re getting enough.

What can Iodine Do for You?

The first organ that comes to mind when you think of iodine is probably the thyroid, and rightly so. The thyroid needs iodine to synthesize the thyroid hormones T4 and T3, hormones that regulate almost every other metabolic and endocrine reaction in the body. Deficiency of iodine makes it harder for the thyroid to do its job, ultimately leading to hypothyroid symptoms and autoimmune thyroiditis. And since the thyroid is the master switch for all your hormones, keeping it happy is definitely a worthy goal.

Iodine also plays an important role in mental health: in developing countries where iodine intake is still inadequate, iodine deficiency is the biggest cause of preventable mental retardation. Fertility in general also requires adequate iodine stores, with the need becoming even more important for women who choose to breastfeed. Clearly, this is one nutrient that you don’t want to be missing out on.

Another Potential Role: Breast Cancer

Considering how closely iodine is linked to fertility, it’s certainly an interesting theory that it might have something to do with breast cancer. And in fact there is some very inconclusive data suggesting an association between iodine, breast cancer, and the thyroid:

This is very intriguing, but there’s nothing here to support the confident pronouncements that “avoiding breast cancer is easy” or that breast cancer is nothing but an iodine deficiency. Correlation is not causation. Plenty of other things have happened in the United States in the past 40 years that could explain the rise in breast cancer. Japanese women are different from American women in all kinds of ways; iodine is just one of them.

The short version: iodine may help prevent against breast cancer and other breast diseases, but at this point, there’s just not enough evidence to tell.

Iodine and the American Diet

On average, iodine intake in the United States is more than adequate. According to our most recent set of data (from 2000), levels of iodine in the United States are nothing to worry about. A person with enough iodine in their diet will have urine levels of 10 mg/DL or greater, and the US average in 2000 was 16.1mg/DL. The one exceptional group is pregnant women, who are frequently mildly deficient even in the United States, because of their higher iodine needs.

But after all the good, here comes the bad news: a Paleo diet may put you at risk for iodine deficiency. salt

Why? Because of where most people in the United States get their iodine from. Since the 1920s, most table salt in the United States and other developed countries has been fortified with iodine, a rare example of a public-health initiative that actually worked. It addressed a real problem (at one point, up to 70% of children in some areas of the United States had goiter!), it offered a realistic solution (inexpensive supplementation of something we all eat anyway), and it worked beautifully: goiter, cretinism, and iodine-deficiency mental retardation are almost unheard-of in the First World today.

So far, so good. But when a lot of people go Paleo, they switch from iodized salt to sea salt, believing that it’s healthier or more “natural.” Sea salt contains very little iodine, and is not usually iodized. That takes a substantial chunk of iodine out of your daily intake, potentially bringing you down to dangerous levels.

Iodine from salt is especially important on Paleo because the other significant sources of iodine in the American diet are dairy (a gray area food that many people eliminate) and bread.

According to this FDA survey, the iodine that Americans get from sources other than salt comes from:

Milk doesn’t naturally contain iodine any more than salt does, but iodine is used as a disinfectant on the cows’ udders and the milk cans, and some makes its way into the finished product. And grains don’t typically contain a lot of iodine either, but it’s used as a preservative in many processed bread mixes.

This might seem a little strange: the top three iodine sources in the modern diet are all completely artificial. None of them contain iodine naturally.

So how did anyone get enough iodine before fortification? Surely that would be the most “Paleo” way to get it in.

The most obvious source is fish and other seafood: just about anything from the sea is high in iodine. But we also used to get a lot of iodine from vegetable foods growing in iodine-rich soils. Today, years of intensive monoculture have depleted our soil to the point where vegetables are no longer a reliable source of iodine as they once were.

Getting enough iodine is a problem that cavemen didn’t have, but modern Paleo dieters do. With so many people switching to sea salt, with the other two iodine sources in the American diet – milk, and bread – off the Paleo table, and with vegetables no longer delivering enough to meet our needs, iodine deficiency starts to look a lot closer to home. But fortunately, this is an easy problem to solve. You can get adequate iodine by:

You might notice that these recommendations are a little light on numbers: that’s because the iodine content of foods is notoriously tricky to pin down. In seaweed, for example, it all depends on whether you measure it wet or dry, or somewhere in between. In animal foods, everything depends on the diet of the animal, so two eggs could have very different iodine concentrations depending on the diet of the hens that laid them. But if you eat enough iodine-rich foods, especially seaweed, you’ll get enough to meet your needs.

Iodine: Necessary but Not Sufficient

Another way to make sure you get all the health benefits associated with iodine intake is to get enough of the other nutrients that help it do its job. As weird as it sounds, iodine alone isn’t the only cause of iodine deficiency problems. This study, for example, described a puzzling finding: among a group of schoolchildren in India, iodine status was perfectly adequate, but 15% had goiter anyway. This suggests that iodine by itself is not enough to handle the symptoms of iodine deficiency; other micronutrients are important as well.

The biggest names in this game are two other minerals, iron and selenium. In the India study, iron levels were notably lower in the goiter group than the healthy group. In other studies, selenium deficiency has been implicated as the villain: selenium is also important in the formation of thyroid hormones, and selenium deficiency is widespread in many areas where goiter is still prevalent.

These findings simply confirm what we already know: health is complicated and untangling one individual nutrient from the tangle is probably impossible. They also highlight the solution: whole foods whenever possible, with supplements only as a last resort. Most whole foods that contain iodine also contain iron and selenium, and they sure taste a whole lot better than a handful of supplement pills.


Iodine deficiency is a problem that Paleo dieters need to be especially aware of, because it’s more likely to be an issue than it is in the general population. Trying to be healthier by replacing regular salt with sea salt can actually compound the problem, since it takes out the last of the three big iodine sources that keep the US average so high.

The fix: either use iodized salt in your cooking (again, there’s nothing wrong with salt and no reason to avoid it), or eat fish and seafood regularly. It’s true that our ancestors didn’t have to do any of this, but we don’t live in that world anymore, and it’s up to us to live in the world we have, not the world we’d like.