Say iodine and most people think of goiter; one type of thyroid disease characterized by the big bulge that people with severe iodine deficiency develop in their necks.
The bulge is nothing more than an enlarged thyroid gland. Normally, as blood flows through the thyroid, it absorbs all the iodine it needs.
But if a diet is chronically low or deficient in iodine, the thyroid grows in size attempting to grab whatever little iodine it can find in the bloodstream.
A larger thyroid = more thyroid tissue trying to sponge up more of this precious mineral.
What is iodine?
Iodine is a mineral just like iron, magnesium and calcium are. It’s found in some foods but not all. The amount of iodine in fruits, vegetables, grains, nuts and seeds depends on the iodine content of the soil those foods were grown in.
For this reason, the iodine content of similar foods can vary. Other factors that can influence the iodine content include fertilizer use and irrigation (1).
How does iodine work?
The body needs iodine to make the thyroid hormones thyroxine (T4) and triiodothyronine (T3). Iodine is a crucial component of these hormones. What do thyroid hormones do? They control your metabolism (helping the body turn food into energy), maintains an ideal body temperature and other important bodily functions.
Thyroid hormones are needed for bone and brain development during pregnancy and infancy too. T4 and T3 also support neurotransmitter production and function and moods but more on that in a bit.
Thyroid function is mainly regulated by thyroid-stimulating hormone or TSH. Its job is to control thyroid hormone secretion and keep it in the Goldie Locks zone; not too little, not too much.
What are symptoms of low iodine?
The symptoms of low iodine are well documented. Given the introduction of iodized salt, many of the classic signs are overlooked and not considered because it’s assumed that iodine insufficiencies are a thing of the past. The classic symptoms include:
- Swelling of the neck
- Fatigue and weakness
- Elevated LDL cholesterol
- Dry, flaky skin
- Hair loss
- Intolerance of cold temperatures
- Brain fog
- Slowed heart rate
- Weight gain not otherwise explained
Severe iodine deficiency is still a major nutritional deficiency concern in some parts of the world. Because the iodine content of soil varies geographically, the iodine content of food is inconsistent & unreliable for the most part. In fact, iodine deficiency is the most common cause of preventable neuro-developmental delays in the world (2).
Goiter used to be a real concern in Canada too before iodine was added to table salt which virtually eliminated goiter, the most extreme form of iodine deficiency. Iodine deficiency disorders and poor iodine intake-related problems result from inadequate thyroid hormone levels in the body. Not enough iodine, not enough thyroid hormone.
FUN FACT: TSH secretion increases when iodine intake is below about 100 mcg/day. TSH continues to rise as iodine intake decreases/remains poor (3)
TSH increases thyroidal iodine uptake from the blood and increases the production of thyroid hormone. However, very low iodine intakes can reduce thyroid hormone production even in the presence of elevated TSH levels. Elevated TSH suggests the thyroid is being told to STEP UP production of its hormones. Unfortunately, thyroid hormone production might be lagging if iodine ain’t around to help.
Iodine deficiency test
There isn’t a blood test to assess iodine status. A review of your usual diet, supplement use, and use of iodized table can help health professionals get a ballpark sense of your intake. This kind of assessment is qualitative and it can help you understand if you’re a risk of inadequate iodine intake.
Urinary iodine test
More than 90% of ingested iodine is excreted in your urine within 24-48 hours. Therefore your daily iodine intakes can be measured based on how much you’re peeing out. This is more accurate than a diet recall but it can support a diet recall which is used to screen those at risk.
WHO iodine deficiency is defined as:
- < 150 mcg/day for pregnant women
- < 100 mcg/day for everyone else including children, adolescents, adults, and breast-feeding women
Iodine patch test
In the natural health world, the iodine skin patch test is promoted as a way to assess an iodine deficiency. It goes like this. Buy an iodine tincture (2% iodine), rub some on your skin (which will turn brown). The iodine patch will fade. It always does.
The thinking is that if it fades quickly, your body has absorbed it quickly (within 4 to 12 hours) because you’re deficient. Your body sucked it up like a dry sponge does water. If it fades slowly (still medium brown 24 hrs later), you’re not deficient because your body isn’t as ‘thirsty’ for iodine.
Problem is, this has never been validated and there aren’t any clinical trials to support this. As a compound, iodine is very volatile and evaporates easily. Not just from the skin, but from iodized salt which is why iodized table salt can be unreliable.
Iodine health benefits
Iodine is crucial for healthy thyroid function. In the thyroid gland, iodine combines with the amino acid tyrosine to form the thyroid hormones T4 (thyroxine) and T3 (triiodothyronine); a mouthful for sure. T3 is the active form and basically does it all.
T3 is the one that regulates physical growth and development in both fetuses and infants, promotes intellectual/brain development. T3 regulates metabolic rate, body temperature, protein metabolism, heart rate, and lung function. It’s also responsible for healthy testosterone levels, as well as estrogen production, immune function, neurotransmitter production and more (4).
Almost all of your body’s functions, in nearly every tissue rely on thyroid hormones. Their actions and influence are so wide-ranging that you cannot live without them.
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Iodine is a nutrient of concern during pregnancy & beyond because of its role in infant and child growth and brain development. Even a modest deficiency, long before goiter shows up, can result in a loss of 10-15 IQ points (5). This is why prenatal supplements have extra iodine and should not be overlooked.
How does iodine affect the brain?
Because iodine is crucial for a healthy and happy thyroid, and therefore T4 and T3 production and function, this precious mineral has a big role in good mental health. Iodine helps ensure that there’s enough T4 and T3 in the brain to help it activate key neurotransmitters such as dopamine, norepinepherine, serotonin, GABA, and acetylcholine.
Without out enough T4 and T3, people may experience insomnia, fatigue, depression, and difficulty concentrating and focusing.
DID YOU KNOW? A healthy thyroid gland will use about 80 mcg of iodine daily to make thyroid hormones
Iodine’s role in mood regulation
As hormones, T4 and T3 regulate gene expression. Think of genes as a light switch and hormones as your hand; you use your hand to turn on or turn off the switch. Similarly, hormones turn on or turn off genes.
Not consuming enough iodine can result in not having enough T4 and T3 to turn on the genes that regulate the very neurotransmitters that regulate your mood.
Thyroid hormones and neurotransmitters
Studies have shown that low levels of T3 results in low levels of serotonin which can lead to decreased mood/happiness, depression, changes in social behaviour, and increased anxiety (6)
T3 also regulates the action of dopamine (which is converted into norepinepherine/epinephrine) which affects memory, feelings of pleasure & reward, focus & attention, and improved behaviour and cognition (7)
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GABA is the ‘zen’ neurotransmitter. Think of it as your brain’s natural benzo. T3 is needed for optimal GABA production and therefore helps you respond to stress better. Low T3 via low iodine intake can result in impaired GABA production and increased anxiety (8).
Not as well known as other neurotransmitters, acetylcholine is needed for learning and forming new memories. Low iodine intake and low T4 and T3 can result in low acetylcholine levels in the brain affecting cognition, memory, recall, and mood.
While similar to epinephrine, norepinepherine acts like a neurotransmitter rather than its hormone sibling. Low iodine intake and low T4 and T3 levels can lead to low levels of norepinepherine leading to depression, anxiety and low energy.
Is iodine good for anxiety?
This question gets asked a lot. As mentioned above, iodine is crucial for two key neurotransmitters that are related to anxiety; serotonin and GABA. Given that some of the common symptoms of low iodine-related hypothyroidism such as depression, fatigue, and trouble concentrating track and are associated with anxiety, ensuring you’re getting enough iodine is worth looking into. Many people are being treated with benzodiazepines or anti-depressants when they really should be treated for hypothyroidism.
Foods that contain iodine
Iodine occurs naturally in soil but the iodine content, and the plants that grow in it, varies from region to region which is why there are pockets of iodine deficiencies.
Some foods, such as iodized salt, are fortified
To get the recommended amount of iodine, eat a variety of iodine-rich foods daily, including:
- Fish (such as cod and tuna), shrimp, and other seafood, which are generally rich in iodine.
- Seaweeds (nori, wakame, kombu kelp)
- Lima beans
- Dairy products (such as milk, yogurt, and cheese) are important sources of iodine in North American diets.
- Fruits and vegetables. The amount depends on the iodine in the soil where they grew and in any fertilizer that was used.
- Iodized salt, which is readily available in North America. Processed foods, however, such as canned soups, almost never contain iodized salt
Who’s at risk for iodine deficiency?
- People living in regions with iodine-deficient soils
- People with marginal iodine status who eat foods with goitrogens (9)
- Those who don’t use iodized salt (this includes sea salt, Himalayan salt)
- Pregnant women
- Breast-fed and weaning infants
- Breast-feeding women
- People on special diets
- Those with poor-quality diets
Are you getting enough iodine?
Studies of North Americans suggest that the vast majority of people are technically consuming enough iodine to prevent a clinical deficiency (using urinary iodine excretion). Many are missing the mark when it comes to the recommended amounts for various age and health categories. The recommended intake for healthy adults is 150 micrograms per day.
The results below are from the ongoing Canadian Community Health Survey which suggests that most Canadians meet the World Health Organization’s goal of 0.79 to 1.57 micromolar/L (of urine). US studies have similar findings.
But not everyone is hitting the mark. About 22% of Canadians have a mild iodine deficiency and another 7% have a moderate deficiency.
In other words, almost 1/3 of the population may be at risk of not getting the full brain & mental health benefits of iodine and that’s a concern.
In medicine, when it comes to matters of nutrition, it’s assumed that if a person doesn’t have a classic nutrient deficiency, in this case, goiter, then there’s nothing to worry about. This is a very old school approach to nutritional biochemistry rooted in the concept of preventing deficiency-related diseases.
The problem with this approach is that it doesn’t take into consideration that people have different absolute requirements for any given nutrient. People don’t absorb nutrients to the same degree, and the field of nutrigenomics has shown us that a person’s unique genes affect their ability to use nutrients to their fullest extent and more.
Simply striving to prevent a deficiency may not be the best goal when it comes to your health, you may want to go beyond just crossing the finish line and go for gold.
This is no less true when it comes to a nutrient like iodine, one which we assume everyone is getting/utilizing enough of especially when it comes to something a precious as your mental health.
Are iodine supplements safe?
Iodine supplementation may be needed if you don’t get enough iodine in your diet. There are different types of iodine supplements; some are very high in iodine and potentially problematic. Iodine is found in many multivitamins with minerals and multi-mineral formulas and as stand-alone iodine supplements.
Adults should avoid prolonged use of doses higher than 1100 mcg per day (the upper tolerable intake level, UL) without proper medical supervision. In children, doses should not exceed 200 mcg per day for children 1 to 3 years old, 300 mcg per day for children 4 to 8 years old. As well, 600 mcg per day for children 9 to 13 years old, and 900 mcg per day for adolescents. These are the upper tolerable intake levels (UL).
Some in the natural medicine world promote the use of very high doses of iodine which really should be avoided. The RDA is 150 mcg or 0.15 mg per day and proponents like Dr. David Brownstein and Dr. Mark Sircus to name a couple are suggesting 25 to 50 mg, or 25,000 – 50,000 mcg per day. This can increase the risk of hyperthyroidism. (10).
There are little to no meaningful well-designed, placebo-controlled studies showing that these kinds of doses are either safe or effective.
A popular supplement in the natural health world. It is a solution of elemental iodine (5%) and potassium iodide (KI, 10%) together with distilled water. Each drop has 6.25 mg of iodine (6250 mcg) – 2.5 mg iodine and 3.75 potassium iodide. Patients are often prescribed take 2 drops per dose providing about 12.50 mg or 12, 500 mcg of iodine.
“Nascent iodine” was once used as simply another name for sodium iodide (an iodide atom bound to sodium). The term was then used by the American mysticist, Edgar Cayce, to describe a free form of iodine (i.e., a single atom of iodide unbound to any other atom) – apparently created by adding electromagnetic or another form of energy.
However, when this free form of iodide is exposed to a positively charged ion, such as sodium or potassium, as it would be in a liquid supplement, it will bind with these to form sodium iodide or potassium iodide. Therefore, if you are buying a supplement promoted as “nascent iodine”, it is most likely sodium iodide or potassium iodine
Common salt of iodine found in many supplements, either in a multivitamin and minerals or as a stand-alone iodine supplement. Doses typically range from 200 to 800 mcg per dose.
Multivitamins with minerals and multi-minerals
Typically contain different forms of iodine. Common salts include sodium or potassium iodide, potassium iodate, potassium iodide, or sodium iodide. Doses in most multis range from 50 to 220 mcg for prenatal formulas.
Also known as iodopovidone and goes by the brand name Betadine. It is an antiseptic used for skin disinfection before and after surgery. It can also be used to disinfect minor wounds.
It can be used to purify water (camping etc) in which case you would consume some iodine if you drank the water but it’s not recommended to use povidone iodine as an iodine supplement. As a disinfectant, it contains far more iodine than is needed for human health.
Health risks from excessive iodine
Interestingly, high intakes of iodine can cause the same symptoms as iodine deficiency including goiter, elevated TSH and hypothyroidism because excess iodine can inhibit thyroid hormone synthesis (11, 12).
In addition, very high intakes of iodine can lead to hyperthyroidism, as well as, thyroiditis and thyroid papillary cancer (11, 12).
Both chronic and acute cases of iodine toxicity is rare but usually caused by dosages in gram ranges versus the microgram range. Individual susceptibility varies which is why keeping capped at the DRI’s UL (Upper Level) of 1100 mcg per day is advisable.
Iodine is an essential nutrient; it must be obtained from your diet and/or supplements.
The fortification of salt resulted in North America was an important public health strategy as an effective intervention for the prevention of clinical iodine deficiency and goiter.
But not all countries fortify their food supply. As a result, iodine deficiencies are very common, especially in Europe and Third World countries, where both the food supply and the soil have low iodine levels.
Your body uses iodine to make thyroid hormones; thyroxine (T4) and triiodothyronine (T3). T3 is needed for energy production, regulating metabolic rate, body temperature, protein metabolism, heart rate, and lung function.
An iodine deficiency can cause hypothyroidism, a condition in which the body can’t make enough T3 and T4.
The good news is, deficiency is easy to prevent. By consuming a variety of iodine-rich foods every day, including iodized salt, you can ensure you get enough iodine for optimal health.
If you think you’re not getting enough iodine, it’s best to talk to your doctor. They’ll check for visible signs of an iodine deficiency, like a goiter, assess for symptoms and/or have you provide a urine sample to get a sense of your iodine status. It would be worthwhile to see a qualified nutrition professional as well to have your diet and supplement use assessed for iodine adequacy.
Sometimes, target iodine supplementation is needed to help reduce your risk for iodine deficiency, or as a treatment for certain medical conditions, such as underactive thyroid or goiter. An easy fix in addition to getting more food sources of iodine is to take a multi-vitamin with minerals or a multi-mineral supplement that contains iodine.
Talk to your doctor about your specific iodine needs.
Doug Cook RDN is a Toronto based integrative and functional nutritionist and dietitian with a focus on digestive, gut, and mental health. Follow me on Facebook, Instagram and Twitter.