Causes of iodine deficiency

If you don’t know much about the mineral iodine, you should, because it’s pretty important. “Iodine is necessary to make thyroid hormones that regulate growth, development, and metabolism,” says Elizabeth Ward, MS, RD, author of Expect the Best. Because the body doesn’t make iodine itself, the mineral is considered essential, per the American Thyroid Association.

Iodine needs vary depending on life stage. Adults require 150 micrograms per day, according to the National Institutes of Health. During pregnancy, that need jumps to 220 micrograms daily, and anyone who is breastfeeding requires 290 micrograms daily.

While iodized salt provides iodine, several other sources exist. These include ocean-caught or farmed fish and shellfish, milk, cheese, eggs, and vegetables grown in iodine-rich soil. “Experts suggest at least eight ounces of seafood weekly for adults, and eight to 12 ounces of seafood weekly for pregnant and breastfeeding women,” says Ward. Seaweed and sea vegetables also offer iodine, adds Isabel K. Smith, MS, RD, a dietitian in New York City. Get a dose of iodine-containing foods by whipping up miso-glazed salmon, protein French toast, or a vanilla bean smoothie.

With the introduction of iodized salt, iodine deficiency is much less common than it used to be. But it can still occur—about 30 percent of the world’s population is at risk, reports the American Thyroid Association. Watch out for these nine signs of iodine deficiency.

You feel tired or depressed

“Iodine, an essential micronutrient, is found in every tissue in the body,” says Nancy M. DiMarco, PhD, RDN, CSSD, Professor Emerita of nutrition and food sciences at Texas Woman’s University in Denton. “The only known function of iodine is its role in the production of the thyroid hormones, thyroxine and triiodothyronine.” In hypothyroidism, the thyroid is underactive—and the body can’t make enough of the thyroid hormones to keep the body running efficiently. Symptoms of hypothyroidism include fatigue, constipation, weight gain, and these other silent symptoms.

Your skin is dry or you feel sensitive to the cold

Additional signs of hypothyroidism include dry skin, sensitivity to cold, and muscle weakness. “Women have an eight times greater risk of developing hypothyroidism than men, making it predominantly a women’s health concern,” says DiMarco. “Although women may develop hypothyroidism at any age, incidence increases with age—especially after menopause.” Find out how to tell if you have a hidden thyroid problem.

Your work is suffering

“In adults, mild to moderate iodine deficiency can impair mental function and work productivity,” says Ward. She explains that these are symptoms of hypothyroidism. “We tend to think of iodine deficiency as a problem of developing countries,” she says. “But many Americans, especially pregnant and lactating women, may not be getting enough because they don’t eat foods that are rich in iodine.”

You have a large lump on your neck

A goiter is the enlargement of the thyroid and is a visible sign of low iodine intake. It would appear at the base of the front of the neck. “A goiter is usually the earliest sign of low iodine intake,” says Ward. “The salt that’s added to processed commercial foods does not contain iodine—and since many Americans rely on processed foods, they may not be getting adequate iodine.” Find out what standard thyroid testing won’t tell you.

You feel like you’re choking when you lie down

A large goiter may cause you to have a hard time breathing and swallowing. When you’re lying down, you may feel like you’re choking, per the American Thyroid Association.

Your urinary iodine concentration is low

Curious about your iodine levels? If you were to get your levels tested, your doctor would likely prescribe a urine test to determine your urinary iodine concentration. This is because iodine leaves the body via urine. The test results would indicate whether you have an iodine deficiency.

You had a miscarriage or stillbirth

“During pregnancy, the body needs thyroid hormones, which require adequate iodine to produce,” says Ward. “ make myelin—which surrounds and protects nerve cells, helping them to communicate properly. Moms who are severely iodine deficient are at risk for miscarriage and stillbirth.” See which foods thyroid experts avoid.

Your child has neurological impairments

“Iodine deficiency has multiple adverse effects on growth and development of the fetus,” says DiMarco. “Iodine deficiency in pregnancy impairs the neurological development of the fetus.” She explains that iodine deficiency in a pregnant mother can lead to irreversible brain damage, including mental retardation, for the baby. “Iodine deficiency is the leading cause of preventable mental retardation in the world,” she notes. In addition, inadequate iodine intake in children limits brain development and may affect intelligence, adds Ward.

Your child has ADHD or other problems

An iodine deficiency during pregnancy may also lead to stunted growth and other problems for the child, notes Ward. “Iodine deficiency during pregnancy has been associated with ADHD in children,” she adds. “Experts suggest pregnant and breastfeeding women and women who may become pregnant take 150 micrograms of potassium iodine as a supplement daily. The body absorbs potassium iodine well, and it’s often the form found in regular multivitamins.” Learn the silent signs you aren’t getting enough vitamins.

At a Glance

Iodine is an essential element needed for the production of thyroid hormone. It is a component of thyroxine (T4 with four iodine molecules) and triiodothyronine (T3 with three iodine mol). Iodine is not produced by the body, so it must be part of the diet. It is found in various foods, including dairy products, seafood, meat, some breads, eggs, and iodized salt, and is found naturally in soil and seawater. Inadequate intake of iodine leads to inadequate thyroid hormone production, resulting in goiter (enlargement of the thyroid), hypothyroidism, and pregnancy-related problems.

Goiter is thse most obvious manifestation of iodine deficiency. The primary activity of the thyroid gland is to concentrate iodine absorbed in the gastrointestinal tract and circulating in blood to make thyroid hormone. Low iodine intake leads to reduced T4 and T3 production and, thus, hypothyroidism. There is then an increase in thyrotropin (TSH) secretion in an attempt to restore T4 and T3 levels to normal. TSH also stimulates thyroid growth, resulting in the goiter. In areas of iodine deficiency, children generally have diffuse goiters, whereas adults who have experienced long periods of iodine deficiency have nodular goiters.

Although it is uncommon in the United States for adults to have hypothyroidism due to low iodine intake, iodine deficiency is the most common cause of hypothyroidism worldwide. Iodine deficiency is on the rise in the United States. In the United States iodine deficiency occurred at a rate of 2.6% between 1971-1994 and a rate of 11.8% from 1988 to 1999. Iodine deficient patients have the usual clinical manifestation of hypothyroidism, including fatigue, weight gain, and depression, as well as a goiter.

Other symptoms of hypothyroidism include brittle fingernails; coarsening and thinning of hair; puffy eyes; pale, dry skin; weakness; and constipation. Symptoms expressing themselves later in the course of the disease are hoarseness; menstrual disorders; puffy hands, face, and feet; thickening of the skin; thinning of eyebrows; increased cholesterol levels; muscle and/or joint aches and stiffness; slowed speech; and decreased hearing.

Thyroid hormone is essential during pregnancy for the normal maturation of the fetal central nervous system; therefore, iodine deficiency is especially important in pregnant women. Severe iodine deficiency in pregnant women has been associated with miscarriages, stillbirth, preterm delivery, and congenital abnormalities.

Hypothyroidism during critical periods of fetal development can lead to mental retardation and problems with growth, hearing, and speech. Mental retardation in the most severe form is known as cretinism, which is a syndrome characterized by permanent brain damage, mental retardation, deaf mutism, spasticity, and short stature. Although cretinism is not common, all fetuses and infants in regions of iodine deficiency are at risk for some degree of mental retardation. Even mild iodine deficiency during pregnancy can lead to low intelligence in children.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Iodine deficiency is not diagnosed specifically in individuals, but rather across populations. To assess iodine nutrition across populations, measurements of urinary iodine, thyroid size, serum TSH, and thyroglobulin levels are used. The urinary iodine concentration indicates current iodine nutrition, whereas thyroid size and serum thyroglobulin concentration reflect iodine nutrition over a period of months or years.

Urinary iodine excretion (UI) is an excellent indicator of recent iodine intake, because more than 90% of ingested iodine eventually appears in the urine. Since iodine deficiency is diagnosed across populations, UI can be measured as random samples from a group and expressed as the median. The median UI in random samples correlates well with 24-hour urine collections, which may be impractical to obtain in large populations. A median UI less than 20 mcg/L is indicative of severe iodine deficiency. Moderate deficiency is indicated with a median UI of 20-49 mcg/L and mild deficiency with a median UI of 50-99 mcg/L.

Thyroid size is a sensitive marker for iodine deficiency, because goiter is the most obvious manifestation. Goiter can be measured through neck inspection and palpation or with ultrasonography. The World Health Organization (WHO) recommends the total goiter rate be used to define severity of iodine deficiency in populations using the following criteria

  • less than 5% iodine sufficiency

  • 5-19.9% mild deficiency

  • 20-29.9% moderate deficiency

  • more than 30% severe deficiency

Serum TSH can be used as a sensitive indicator of iodine nutrition in the newborn (not in children and adults). Iodine deficiency in the population is determined when there is an increase in transient newborn hypothyroidism as indicated when more than 3% of newborn TSH concentrations are greater than 5 mIU/L in blood spots collected 3-4 days after birth. TSH screening in newborns is used in many countries to detect congenital hypothyroidism due to iodine deficiency, which is the most common preventable cause of mental retardation in the world.

Serum thyroglobulin concentration (Tg) is elevated more often than serum TSH in infants and children. It is a sensitive measure of thyroid activity but is a nonspecific test, as any type of thyroid stimulation or injury can raise Tg levels. Increased Tg levels greater than 40 mcg/L correlate well with iodine deficiency.

Taking too much iodine, whether through medications (such as amiodarone, radiology procedures, or dietary excess), can cause or worsen hyperthyroidism and counterintuitively hypothyroidism. Also, people who move from iodine deficient regions of the world to iodine sufficient areas may develop thyroid problems. These patients usually develop iodine induced hyperthyroidism.(Table 1).

Table I.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

Serum TSH levels in newborns can be affected by iodine antiseptics used during delivery. In newborn TSH screening, blood should be taken at least 48 hours after birth to avoid physiological newborn surge.

What Lab Results Are Absolutely Confirmatory?

There are no tests available to confirm if you have enough iodine in your body. Iodine deficiency in populations is best managed by ensuring food has sufficient levels of iodine. Because even mild iodine deficiency can have effects on the developing fetus, pregnant women should take a multivitamin containing at least 150 mcg of iodine daily.

Iodine status cannot ultimately be determined by thyroid hormone concentrations. Although serum T3 does increase or remain unchanged and serum T4 usually decreases in iodine deficient populations, these changes are generally within normal range in most children and adults. The overlap with iodine sufficient populations is large enough to make thyroid hormone levels not sufficiently sensitive for the diagnosis of the disorder.

Median UI results can be misinterpreted. Individual iodine intakes are highly variable from day to day. To estimate iodine intake in individuals, 24-hour urine collections are recommended.

Iodine deficiency: Clinical implications

A 65-year-old woman is found to have a goiter. She is clinically euthyroid. She is a strict vegan and only uses noniodized Himalayan salt for cooking. Her thyroid gland is diffusely enlarged with no nodules. The estimated weight of the thyroid gland is 50 g (normal 10–20 g) based on ultrasonography. Her thyroid-stimulating hormone (TSH) level is 2.95 mU/L (reference range 0.5–5 mU/L), and her free thyroxine level is 0.8 ng/dL (0.7–1.8 ng/dL). Testing for TSH receptor antibody is negative. Her 24-hour urine iodine is undetectable (urine iodine concentration < 10 μg/L with urine volume 3,175 mL). What may be the cause of her goiter?

Iodine is an essential element needed for the production of thyroid hormone, which controls metabolism and plays a major role in fetal neurodevelopment. Its ionized form is called iodide. Iodine deficiency results in impairment of thyroid hormone synthesis and may lead to several undesirable consequences. Physicians should be aware of the risks iodine deficiency poses, especially during pregnancy, and should be familiar with approaches to testing and current indications for iodine supplementation.

SOURCES OF IODINE AND SALT IODIZATION

The major environmental source of iodine is the ocean. Elemental iodine in the ocean volatilizes into the atmosphere and returns to the soil by rain. The effects of glaciation, flooding, and leaching into soil have resulted in the variable geographic distribution of iodine. Mountainous areas (eg, the Alps, Andes, Himalayas) and areas with frequent flooding typically have iodine-deficient soil due to slow iodine cycling.1 Seafood is a good source of iodine because marine plants and animals concentrate iodine from seawater. The iodine content of other foods varies widely, depending on the source and any additives.

In the United States, the major sources of dietary iodine are dairy products (due to livestock iodine supplements and use of iodophors for cleaning milk udders) and iodized salt.1,2 Seafood contains a higher amount of iodine by weight than dairy products but is consumed far less than dairy.3,4 Further, the iodine content of milk can range from 88 to 168 μg per 250 mL (about 1 cup), depending on the product manufacturer. Also, iodine content is often omitted from the food label. Even if it is reported, the package labeling may not accurately predict the iodine content.5

Less common sources of iodine are radiographic contrast, bread with iodate dough conditioners, red food coloring (erythrosine), and drugs such as amiodarone.1

Using iodized salt is an effective and stable way to ensure adequate iodine intake. In the United States, only table salt is iodized, and the salt typically used in processed food has only minimal iodine content.6 Nearly 70% of the salt we ingest is from processed food. Table salt provides only 15% of dietary salt intake, and only 70% of consumers choose iodized salt for home cooking.7

IODINE REQUIREMENTS

Daily requirements of iodine suggested by the World Health Organization (WHO) and by the US Institute of Medicine are in the range of 90 to 150 µg/day.8,9 The iodine requirement is higher in pregnancy (220–250 µg/day) because of increased maternal thyroid hormone production required to maintain euthyroidism and increased renal iodine clearance, and it is even higher in lactating women (250–290 µg/day).

IODINE STATUS IN POPULATIONS

Since the establishment of universal salt iodization programs under the influence of the WHO and the International Council for Control of Iodine Deficiency Disorders (ICCIDD) in 1990, global iodine status has continued to improve. Yet only 70% of households worldwide currently have access to adequately iodized salt, because many countries lack a national program for iodine supplementation. The population of the United States was historically iodine-deficient, but since the introduction of salt iodization in the 1920s, the iodine status in the United States has been considered adequate.1

The WHO defines iodine status for a population by the median spot urinary iodine concentration. Because a urinary iodine concentration of 100 μg/L represents an iodine intake of about 150 μg/day, the WHO uses a median urinary iodine concentration of 100 to 199 μg/L to define adequate iodine intake for a nonpregnant population.9

The National Health and Nutrition Examination Survey (NHANES) found that the median urinary iodine concentration decreased by more than 50% from the 1970s to the 1990s, indicating declining iodine status in the US population.2 Of particular concern, the percentage of women of childbearing age with moderate iodine deficiency increased from 4% to 15% over this period.2 Still, the NHANES survey in 2009–2010 indicated that the overall US population is still iodine-sufficient (median urinary iodine concentration 144 μg/L).10 The decline in the US iodine status may be due to reduction of iodine content in dairy products, increased use of noniodized salt by the food industry, and recommendations to avoid salt for blood pressure control.

Although US iodine status has been considered generally adequate, iodine intake varies greatly across the population. Vegans tend to have iodine-deficient diets, while kelp consumers may have excessive iodine intake.11 Individuals with lactose intolerance are at risk of iodine deficiency, given that dairy products are a major source of iodine in the United States. Physicians should be aware of these risk factors for iodine deficiency.

PREGNANCY AND LACTATION

It is crucial to maintain euthyroidism during pregnancy. In early gestation, maternal thyroid hormone production increases 50% due to an increase in thyroid-binding globulin and stimulation by human chorionic gonadotropin. The glomerular filtration rate increases by 30% to 50% during pregnancy, thus increasing renal iodine clearance. Fetal thyroid hormone production increases during the second half of pregnancy, further contributing to increased maternal iodine requirements because iodine readily crosses the placenta.12

Women with sufficient iodine intake before and during pregnancy generally have adequate intrathyroidal iodine storage and can adapt to the increased demand for thyroid hormone throughout gestation. But in the setting of even mild iodine deficiency, total body iodine stores decline gradually from the first to third trimester of pregnancy.13

The fetal thyroid gland does not begin to concentrate iodine until 10 to 12 weeks of gestation and is not controlled by TSH until the full development of the pituitary-portal vascular system at 20 weeks of gestation.12 Therefore, the fetus relies on maternal thyroid hormone during this critical stage of neurodevelopment. Thyroid hormone is essential for oligodendrocyte differentiation and myelin distribution14 as well as fetal neuronal proliferation and migration in the first and second trimesters. Iodine deficiency leading to maternal hypothyroidism can result in irreversible fetal brain damage.

Because of the greater requirement during pregnancy, the WHO recommends using a median urinary iodine concentration of 150 to 249 μg/L to define a population that has no iodine deficiency.9 The NHANES data from 2007 to 2010 showed that pregnant US women were mildly iodine-deficient (median urinary iodine concentration 135 μg/L),10 and the National Children’s Study of 501 pregnant US women during the third trimester in 2009 to 2010 showed they had adequate iodine intake (median urinary iodine concentration 167 μg/L). Interestingly, pregnant non-Hispanic blacks were the only ethnic group with a median urinary iodine concentration less than 150 μg/L, suggesting that race or ethnicity is a predictor of iodine status in pregnant women.10

11 Signs And Symptoms Of Iodine Deficiency

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 (2, 3, 4):

  • 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.

What does iodine do?

Your thyroid gland uses it to make thyroid hormones which have a variety of functions (6, 7):

  • 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).

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.

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.

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 Facebook, Instagram and Twitter.

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