Food sources of iodine - by Doug Cook RD

11 Signs And Symptoms Of Iodine Deficiency

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Iodine is one of the 50+ nutrients you need every day to be healthy. It’s an essential mineral just as iron, magnesium and zinc are.


Your body uses iodine for a variety of functions. Without enough iodine, you can develop a full-blown deficiency disease or it may be more subtle.


The amount of iodine you need each day depends on your age, and how you meet your iodine requirement will depend on your overall food choices and/or supplement use.


What is iodine?

Iodine is an essential mineral commonly found in a variety of foods.


Unfortunately, up to a third of people worldwide are at risk of not getting enough iodine (1). Rates of iodine deficiency have reached epidemic levels, increasing fourfold over the past 40 years according to the World Health Organization.


Some estimates are that North Americans used to get about 800 mcg  of iodine per day. Much less than we do today. That makes for a potentially public health problem.


Those at the highest risk include (234):

  • People living in regions with iodine-poor soils. This includes South Asia, Southeast Asia, New Zealand and European countries.
  • People with marginal iodine status who eat foods with goitrogens
  • 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 (a.k.a. highly processed)
  • People who follow a vegetarian or vegan diet.


On the other hand, clinical iodine deficiencies are rare in North America. This is because there are sufficient levels of the mineral in the food supply (5). Having said that, many still don’t get an optimal amount of iodine and don’t reap all of its benefits.


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What does iodine do?

Your thyroid gland uses it to make thyroid hormones which have a variety of functions (67):

  • Neurotransmitter production
  • Control growth
  • Help to repair damaged cells
  • Supports a healthy metabolism
  • Bone and brain development during pregnancy and infancy


There is a strong connection between iodine and mental health too.


What are the signs and symptoms of iodine deficiency?

1. Swelling of the thyroid gland

As blood levels of iodine decrease, the thyroid gland, located in the neck, gets bigger. This is because it’s trying to grab what little iodine there is in the blood stream. In this sense, it’s casting a wider net (8). More thyroid tissue, the more it can mop up circulating iodine.


Swelling of the neck is the most common sign of iodine deficiency. It can be felt long before it’s seen with the naked eye. If the thyroid gland gets really enlarged, it will appear as a lump in the neck; a goiter.


2. Low levels of thyroid hormones

It goes without saying. Low intakes of iodine will result in lower levels of the very hormones that rely on iodine as a building block. The two thyroid hormones are T4 or thyroxine, and T3 or triiodothyronine. T3 has three atoms of iodine and T4 has, you guessed it, four atoms of iodine.


Lower levels of thyroid hormones will lead to an under-active thyroid gland and reduced thyroid function.


3. Weight gain or inability to lose weight

If everything else has been looked at when it comes to weight management and you are experiencing weight gain or difficulty losing weight, then your metabolism may need help. Inexplicable weight gain can be a sign of iodine deficiency or insufficiency.


The body needs adequate amounts of iodine to make optimal amounts of thyroid hormones, which drive your metabolic rate (9, 10). When your metabolic rate is low, you burn fewer calories at rest. This means there is a greater likelihood your food energy will be stored as fat (11, 12).


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4. Fatigue and weakness

Since iodine is needed for a healthy metabolism, then a deficiency resulting in a slower metabolism will leave you feeling tired. In fact, the vast majority of people with low thyroid hormone levels and/or hypothyroidism feel tired, run down, fatigue and general malaise (13).


Obviously if you’re metabolism is slow and you don’t have enough thyroid hormones to help you make energy from food, you’ll be dragging your feet. But, you’ll also feel tired if your mood is low, are feeling cold, and concentration is off – symptoms of iodine deficiency as well.


5. Dry, flaky skin

Another common symptom of iodine deficiency. Studies have found that those with low thyroid hormones levels may experience dry skin (14, 15). Women who are peri-menopausal or postmenopausal are routinely told their flaky, dry skin is just part of losing their cycle. Concerns about iodine status are often overlooked because it’s assumed that iodine deficiencies are a thing of the past.


Thyroid hormones also regulate sweat. Iodine deficiency can lead to less sweat which normally helps to hydrate the skin (16, 17). Sweat production is compromised with hypothyroidism, so assessing your iodine intake should be part of your skin care routine.


6. Brittle nails

Like the skin, the fingernails tell a lot about your health. Thyroid diseases such as hypothyroidism (low thyroid hormones as a consequence of iodine deficiency) may cause brittle nails or splitting of the nail bed from the nail plate (onycholysis).   (18)


7. Cold intolerance

This is another classic and common symptom of a suboptimal iodine intake. Those with low levels of thyroid hormones routinely complain of intolerance to cold temperatures (19).


This is because one of iodine’s role is to drive your metabolic rate. Digesting food for energy creates heat. If you have low thyroid hormone levels, your metabolism will slow down. Simply put, a slower metabolism creates less heat and less heat will make you feel colder (20, 21).


8. Problems with concentration & memory

Iodine is needed for learning and memory consolidation. It is needed for concentration as well. Clinical and functional deficiencies can affect your ability to concentrate, learn and remember (a.k.a. brain fog) (22, 23, 24).


Iodine and its role in thyroid hormone production influences memory via its impact on your hippocampus size and mass. Those with lower levels of thyroid hormones TSH, T4 and the active form, T3 have smaller hippocampuses (25). Assessing your iodine intake or the iodine levels in your urine is a wise consideration for those middle aged and older.


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9. Hair loss

This can be an easily overlooked symptom of iodine deficiency, especially with older adults. We assume hair loss is just a part of aging, and it can be but it can also be from a lack of iodine. Thyroid hormones do so much including controlling the growth of hair follicles.


Low iodine and low thyroid levels result in decreased hair follicle regeneration. Healthy hair, and hair growth, needs a healthy hair bed – in this case, the follicles (26, 27, 28). Nourishing your scalp goes beyond biotin, vitamin A, zinc and B vitamins – give iodine some love too.


10. Cognitive issues

The brain is a major target organ for thyroid hormones, and adult-onset hypothyroidism can have significant effects on neuro (brain)-psychiatric function. Cognitive dysfunction is commonly seen in clinical hypothyroidism (29).


Cognitive symptoms include decreases in general intelligence, attention/concentration, memory, perceptual function, language, psychomotor function, and executive function. Memory is the most consistently affected attribute (30, 31, 32, 33).


Those with cognitive decline and impairment would benefit from assessing thyroid function including thyroid hormones T4 and T3. T4 alone doesn’t indicate thyroid hormone ‘health’. You can have adequate levels of T4 but not T3 since T4 has to be converted into its active form. Considering iodine status should be part of an overall assessment of thyroid function.


11. Mood disorders

Low thyroid levels are associated with both depression and anxiety. Low levels of T4 and the active thyroid hormone T3, negatively impacts levels of serotonin, dopamine, and GABA. All of these neurotransmitters influence cognition, behaviour and mood (34, 35, 36).


An under-active thyroid can lead to depression and anxiety. An over-active thyroid can lead to and aggravate anxiety with racing heart, nervousness and trembling. Most would never consider mood disorders as a symptom of iodine deficiency but it should.


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How is iodine deficiency prevented?

The best defense is a good offense. Reflect on the risk factors for iodine deficiency above and address any that might apply to yourself.


The best way to prevent an iodine deficiency is to ensure you’re consuming enough of this precious mineral daily. The important thing there is to include a variety of foods rich in iodine and/or include a good quality multivitamin with minerals or multi-mineral supplement. You may want to consider an iodine supplement on its own.


A good target is to buy a brand that provides 100 mcg per dose. As well, if you’re a vegan or vegetarian, seriously consider a supplement, or include seaweed several times a week as land-based plant foods are poor sources of iodine.

Food sources of iodine

An unintended consequence of the anti-sodium movement is that many have given up on using iodized table salt. The reality is, the amount of sodium most people get from table salt is minimal compared to processed foods. A “pinch’ is the problem.


Also, iodine is volatile, it evapourates easily so if you’ve had salt sitting around for a year, or two or more. Much of the iodine has been lost.


The amount of iodine in foods 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 (35).


Best foods sources of iodine include:

  • Fish, shrimp, seafood
  • Eggs
  • Lima beans
  • Nuts
  • Meats
  • Dairy products
  • Seaweed (nori, wakame, kombu kelp)
  • Iodized table salt (which is readily available in North America. Processed foods, however, such as canned soups, almost never contain iodized salt)


When it comes to minerals, calcium, iron, magnesium, potassium and zinc get all the attention. Like with vitamins C and D, because true cases of scurvy and rickets are rare (I do seem them in practice), we assume everyone is getting optimal amounts of those nutrients.


Iodine is suffering the same fate. Because we don’t see people walking around the streets with full-on goiters, we assume everyone is getting enough iodine. It’s true, enough to prevent goiter but perhaps not to reap iodine’s fullest benefits. Time to give iodine the attention it needs


Doug Cook RDN is a Toronto based integrative and functional nutritionist and dietitian with a focus on digestive, gut, mental health.  Follow me on FacebookInstagram and Twitter.