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Are You Getting Enough Iodine? The Effects of Iodine Deficiency


We need lots of different minerals and vitamins to keep our bodies working well. Eating a varied, balanced diet is usually enough for us to get most of the ingredients we need. However, one ingredient you don’t often find in your diet is iodine. And that can mean your body isn’t functioning properly.

What does iodine do?

woman's neck thyroid gland

Iodine is an important ingredient our bodies use to make thyroid hormones. These hormones control our metabolism and are also important for bone and brain development in babies. Iodine is naturally found in seafood. Today, dairy products are also a good source of iodine because iodine is used as a disinfectant.

Iodine deficiency used to be a major problem across the U.S., especially for inland states. Before the 1920s, an area spanning the Great Lakes, Appalachians, and Northwestern regions of the U.S. was known as the “goiter belt.”

A goiter is an enlarged thyroid gland, and is one of the most common symptoms of iodine deficiency. Some goiters are small and don’t cause any problems, but they can be large enough to be highly visible and cause problems breathing and swallowing. In the goiter belt, between one quarter and three quarters of children had “clinically apparent” goiters.

A doctor in Michigan noticed during the World War I draft that almost a third of new enlistees had goiters so bad they disqualified the men from service. Studies carried out in the area as a result of this observation found that up to two-thirds of the population suffered from serious goiters.

While goiters are the most visible symptom of iodine deficiency, they aren’t the only one. Because your thyroid hormones control your metabolism, low iodine levels can cause an underactive thyroid (hypothyroidism), which leads to metabolic disorders. Unexplained weight gain, feeling tired and weak, suffering from dry skin and hair loss, and feeling cold are all common symptoms.

More concerningly, low iodine levels can slow your heart rate, making you feel dizzy or sick. Iodine is also important for brain function, so learning and memory problems are common. Within ten years of increasing iodine intake across the nation, the average IQ in the States rose 3.5 points.

How to get enough iodine

table salt shaker

Scientists stumbled onto a simple and effective way of increasing everybody’s iodine intake — by adding it to table salt. Today many salts are still marketed as “iodized,” meaning they contain iodine. We don’t need very much iodine to support healthy thyroid function, so using iodized salt as normal was all that was needed to get the right amount.

As well as increasing the national IQ, iodized salt cured the goiter belt. Today, about 120 countries have mandated iodized salt. In the U.S., adding iodine to salt is only voluntary, so it’s important to check if the salt you buy is iodized.



0-6 months

110 micrograms

7-12 months

130 micrograms

1-8 years

90 micrograms

9-13 years

120 micrograms

14-18 years

150 micrograms


150 micrograms

During pregnancy

220 micrograms

During breastfeeding

290 micrograms

Source: National Institutes of Health Office of Dietary Supplements

A microgram is a millionth of a gram, a tiny amount. In the U.S., iodized salt contains 45 micrograms of iodine per gram. That means the average adult needs about half to three-quarters of a teaspoon of salt per day. That’s below the recommended daily limit of sodium, so getting enough iodine through salt won’t cause other health problems for people who aren’t on a limited sodium diet.

Iodine deficiency is on the rise

pink himalayan salt

With a common source of iodine easily available, why are levels of iodine deficiency going up again? It’s mostly to do with our lifestyles.

After the introduction of iodized salt in the 1920s, American levels of iodine deficiency dropped dramatically. By the 1940s, America was classed as iodine sufficient, meaning the population as a whole was getting enough iodine. The use of iodized salt has remained steady at 70-76% of U.S. households since the 1950s, and over 90% of U.S. households have ready access to iodized salt.

However many households aren’t properly informed about the importance of iodine in salt, and the national salt intake has been making headlines in recent years. The FDA recently issued guidelines for reducing the sodium content of processed and restaurant foods by 12% over the next 2.5 years in a bid to reduce how much salt Americans are consuming. The daily recommended amount is 2300mg of salt, but the average American consumes 3400mg, almost 50% more.

That might seem like good news for our thyroids, but the majority of this salt isn’t iodized. Most processed foods use non-iodized salt, meaning there’s lots of sodium in the American diet, but very little iodine. To check if your favorite food is iodized, look at the ingredients label. Iodized salt has to be listed separately, so it’s easy to spot if iodine is included.

Iodine deficiency isn’t isolated to people who rely on processed or fast food, either. Home cooks are also skipping out on iodine, because regular table salt has fallen out of fashion. If you use speciality salts instead, you might be surprised to learn they aren’t iodized. This includes kosher salt, sea salt, pink himalayan salt, fleur de sel, and many other salt varieties.

Non-salt sources of iodine

nori sushi

If you can’t imagine cooking with table salt, giving up processed foods, or increasing your sodium intake, there are other sources of iodine available. Dairy products can be a good source of iodine.

A study in the late 1970s found that raw milk from farms in New York State contained very high levels of iodine — a third had 200-500 micrograms of iodine per liter (about 34 fluid ounces), and 10% had more than 500 micrograms per liter. That’s several times more than the recommended daily intake of iodine, which for an adult is about 150mcg. In retail milk, the iodine content averaged just under 400mcg per liter, and 472mcg per 100g (3.5oz) of cheese.

Too much iodine can be as bad for us as too little. Excess iodine can cause an overactive thyroid (hyperthyroidism), and that can lead to increased heart rate, anxiety, shaking, palpitations, rapid weight loss, and excessive hunger and sweating. In serious cases, people can experience what’s known as a thyroid storm, which can be life-threatening.

However the upper levels of daily iodine intake are very high, about 1100mcg for an adult, so consuming too much is not usually a problem for most people.

The amount of iodine in dairy varies by product. However in general, you can get your full daily amount of iodine from the following:

  • 16 ounces of nonfat cow’s milk
  • 10 ounces of Greek yogurt
  • 6 hen’s eggs

Seafood is another important source of iodine, and the reason people living in coastal regions are rarely iodine-deficient. Some of the top sources of iodine include:

  • Seaweed (6.5g of dried nori provides 100% of daily iodine)
  • Cod (3oz of baked cod contains all the iodine you need)
  • Oysters (5oz of cooked oysters meet your daily iodine intake)

Vegetarians and vegans may struggle to find enough iodine to meet their dietary requirements without using iodized salt. One alternative product is kelp granules, sold in many grocery stores as a salt substitute. Because kelp is a seaweed, these products are usually very high in iodine. However they can also contain heavy metals like mercury, so it’s important to only consume them in moderation.

Another source of iodine available to most people is enriched foods, especially bread. Fortified bread can contain up to 185mcg of iodine per slice, which is more than the recommended daily requirement.

Finally, you can also take supplements if you’re worried about your iodine intake. Many daily multivitamins now contain iodine.

In conclusion

Iodine is an important nutrient that plays a crucial role in many of our body’s functions. However in some regions it can be hard to get enough iodine naturally, especially for vegetarians and vegans. While seafood and dairy products are good sources of iodine, iodized salt has also helped people get enough iodine over the past 100 years. As our diets and lifestyles change, our consumption of iodized table salt has decreased, and iodine deficiency is one again on the rise.

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