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A trace mineral and an essential component of the thyroid hormones, triiodothyronine (T3) and thyroxine (T4). These hormones regulate the metabolic activities of most cells and play a vital role in the process of early growth and development of most organs, especially the brain. Inadequate intake of iodine-rich foods leads to insufficient production of these hormones, which adversely affect the muscle, heart, liver, kidney and the developing brain.(1) Nationwide insufficient iodine was once considered such a serious problem that the mineral was added to table salt, and iodine deficiency remains the leading cause of preventable mental retardation in the world today, even in developed nations. Unfortunately, most table salt is not a healthy naturally occurring rock, crystal or sea salt and should never be considered as a source of healthy iodine.

According to an Indian Journal of Endocrinology and Metabolism article, 15 to 20 milligrams of this element are found in your body, with 70% to 80% in your thyroid gland,4 and also high concentrations in the salivary glands.

There are multiple types of iodine. The American Thyroid Association (ATA) explains that when it’s in the form of iodide, iodine is made into two radioactive forms: iodine-123 or I-123 (harmless to thyroid cells), and iodine-131 or I-131 (harmful to thyroid cells). Both are used in people with thyroid diseases, and given orally in pill or liquid form.5 If you want to know where your iodine levels stand, you doctor may recommend that you undergo a urine or blood test.6

Don’t confuse active forms of the chemical element iodine7 with that found in table salt, even if the label says it contains iodine because iodized table salt is technically potassium iodide8 added to sodium chloride, the chemical name for table salt.9

The same principle applies if you encounter povidone iodine. This substance, commonly known by the brand name Betadine10 and used topically as an antiseptic,11 is composed of iodine and a synthetic polymer called polyvinylpyrrolidone or povidone.12

A brief history of iodine

Did you know that iodine was accidentally discovered? A French chemist named Bernard Courtois discovered iodine in 1811, while helping his father manufacture saltpeter, an ingredient used in gunpowder. After running out of wood ash, which was their source of potassium nitrate, Courtois burned seaweed instead, then washed the ash with water.

However, he added too much sulfuric acid to the washed ashes, and a cloud of violet gas appeared from the ashes. When it condensed, purple crystals appeared on a cold surface.

Suspecting it might be a new element, Courtois took the crystals to other scientists to examine. When they confirmed that, indeed, it was a new element, a French chemist named Joseph Louis Gay-Lussac named it “iode,” from the Greek word ioeidēs meaning “violet-colored.”13

Originally, iodization was adopted to reduce the incidence of goiter, an enlargement of the thyroid gland. But research since then has found that iodine also plays a crucial role in brain development, especially during gestation.

Iodine deficiency today is the leading cause of preventable mental retardation in the world. It’s estimated that nearly one-third of the world’s population has a diet with too little iodine in it, and the problem isn’t limited to developing countries—perhaps one-fifth of those cases are in Europe (pdf), where iodized salt is still not the norm.

Iodine in Salt: Why Is It Added?

Iodine was added to salt around 1924, at the request of government initiatives, due to the growing need for regulation of iodine deficiency disorders. In the 1920s era in the United States, the Great Lakes and Pacific Northwest region of the country experienced high incidences of goiter, a common thyroid-malfunction-based condition involving a large swelling on the neck. Soil levels were extremely low in iodine, and people weren’t eating enough iodine rich foods.

Researchers at the University of Michigan decided to copy a Swiss practice of adding iodine to cooking salt, in order to attempt to remedy the concern. Goiter occurrences dropped drastically as a result, and the practice soon became standard [1]. In fact, due to the successes seen in Michigan, iodine-enhanced salts were sold by the Morton Salt Company for the first time, on a national scale. Regulations committees saw that it would be easy to take a simple and cost-effective measure to prevent this health imbalance, and for about $0.05 per person per year, salt became iodized.

Salt was used as the carrier for iodine because it was an easy, spoil-free method of getting iodine into the food chain. Salt is a food that almost everyone eats throughout the day. Iodized salt was also added to animal feed, as it also offered thyroid support benefits for livestock as well.

Things have changed since the 1920s with the manufacturing of toxic chemicals and more cost-effective ways of harvesting salt. Most of the salt harvested then was natural salt from the sea or from natural salt deposits and contained the beneficial trace mineral iodine.

Table Salt or “Iodized Salt” is not a healthy naturally occurring rock, crystal or sea salt. It is a manufactured type of sodium called sodium chloride with added iodide.

Iodine in salt available at grocery stores, restaurants, and in practically all processed foods, have synthetic chemicals added to them. These chemicals may include manufactured forms of iodide, sodium solo-co-aluminate, fluoride sodium bicarbonate, potassium iodide, anti-caking agents and aluminium derivatives. Unfortunately, most table salt is unhealthy and should never be considered as a source of healthy iodine.

Salt found in nature is not usually white. It is often pink in color, such as Himalayan Crystal Salt which is harvested in pristine mountains and naturally dried in the sun.

Of course, we need this iodine because the thyroid gland requires it for making thyroxine (T4) and triiodothyronine (T4), two key hormones for metabolic function. Commonly consumed forms of iodine include potassium iodate, potassium iodide, sodium iodate, and sodium iodine. Each of these forms of iodine enables the thyroid gland to create T4 and T3 hormones.

Using iodine-fortified table salt may still put you at risk for micronutrient deficiencies. A study done at the University in Texas at Arlington, and published in the journal Environmental Science and Technology, found that salt alone cannot prevent iodine deficiency [2].

The research looked into iodine levels in over 80 types of commonly-sold iodized salt brands and found that 47 of them (over half!) did not meet the U.S. Food and Drug Administration’s recommendation for healthy iodine levels. Moreover, with time, iodine levels tend to decrease in salt products that are left in humid conditions. The study concluded that only about 20% of the so-called “iodized” salt sold in stores has enough of the micronutrient to be considered enough for daily level acquisition.

Why iodine deficiency is alarmingly rising

Here are iodine deficiency statistics that may surprise you:

  • The National Health Nutritional Examination Survey reported that iodine levels have decreased by 50 percent in the last 30 years.
  • More than 96 percent of over 5,000 patients tested were iodine-deficient in a clinical study conducted by thyroid expert Dr. David Brownstein. (2)
  • According to the WHO, iodine deficiency affects 72 percent of the world’s population.
  • In 2011, 70 percent of households globally had access to iodized salt (3)

The term iodine deficiency disorders has been coined to represent the different array of disorder that result from iodine deficiency in a population. (4) These disorders are all preventable if the appropriate dose of iodine is administered. Common disorders that result from iodine deficiency are hypothyroidism, increased cholesterol levels, endemic goiter, cretinism, decreased fertility rate, increased infant mortality, fibrocystic breast disease, atherosclerosis and breast cancer. (5)

Iodine deficiency is a rising problem worldwide, affecting 2.2 billion people, predominantly in countries where iodized salt is not available.14,15 According to the ATA, average urinary iodine levels (which may be utilized to measure dietary iodine intake16), have dropped by half since the 1970s.17 There are nutritional and environmental factors linked to an iodine deficiency, namely:18

  • Shifts in food preparation and consumption — More Americans are consuming prepackaged and ready-to-eat foods or eating in restaurants, instead of preparing home-cooked meals. This increases their exposure to high-salt foods that may not have sufficient amounts of iodine.
  • Thiocyanates in foods — Thiocyanates are metabolites19 found in vegetables from the Brassica family, as well as in cassava and soy. Frequent consumption of high-thiocyanate foods, according to the World’s Healthiest Foods, may disrupt your thyroid gland’s ability to process iodine. This may cause you to think you’re dealing with an iodine deficiency, even if the problem isn’t present at all.
  • Iodine-deficient soils — In North America overuse of alkaline fertilizer and intensive cropping contributes to iodine depletion in the soils, which then prevents food crops from getting iodine naturally from the soil.20 In the Midwest in the U.S., soils are lacking in iodine anyway, due to their distance from ocean waters.21

There are also certain groups who may be at risk for an iodine deficiency:22

  • Vegans and vegetarians23 — Authors of an Annals of Nutrition and Metabolism article highlighted that plant-based foods have fewer iodine contents than animal-based products.24
  • Pregnant women — Iodine facilitates thyroid production essential for the baby, although the mineral is oftentimes released through the mother’s urine.25 Some studies showed that pregnant women in countries like Brazil,26 China,27 Ethiopia28 and Ghana29 aren’t getting sufficient amounts of iodine.
  • People living in regions with iodine-deficient soils and who eat mostly locally grown foods — Soils in these areas tend to have low iodine levels, producing crops that have few amounts of this mineral. The Himalayas, the Alps and the Andes regions and some river valleys in south and southeast Asia tend to have the most iodine-deficient soils.30  In the early 20th century, certain areas of the U.S. were once known as “goiter belts” because regional soils were so lacking in iodine that up to 70% of children had goiter, a symptom of iodine deficiency. An iodine supplement program in the affected regions — the Appalachians, Great Lakes and Northwestern areas — and the introduction of iodized salt in 1924 addressed the issue.31
  • People consuming fewer amounts of iodine — Increasing iodine levels should be done via your diet since the body doesn’t produce it. If you don’t consume enough iodine-rich foods, this could lead to an iodine deficiency.32
  • People who eat foods containing goitrogens — These are naturally occurring substances33 that could negatively impact your body’s usage of iodine. Eating raw vegetables in the Brassica family (cauliflower, broccoli, kale, cabbage, soy, Brussels sprouts) can impact thyroid function because they contain goitrogens, molecules that impair peroxidase. Steaming these cruciferous vegetables until fully cooked before consumption breaks the goitrogens down. People with iodine deficiency are at risk when consuming these foods. (15)
  • People with selenium deficiency Iodine deficiency, coupled with selenium deficiency, is likely to lead into thyroid imbalance. One of the more serious manifestations of thyroid imbalance is a goiter. In many individuals who are diagnosed with iodine deficiency, studies have shown some may have selenium deficiency as well. The thyroid gland needs both selenium and iodine to produce adequate levels of thyroid hormones, but when there’s a deficiency in one or both, your body has low thyroid hormone levels. That’s why adequate iodine levels are needed for adequate thyroid function. Iodine is known for playing a vital role in thyroid health while benefit-rich selenium is critical in recycling iodine. When selenium levels are low, the thyroid will work harder to produce thyroid hormones, and the body will have a difficult time changing these hormones into forms utilized by cells. It’s important to treat both deficits in order to re-establish normal thyroid health. (10)
  • Smokers – Tobacco smoke contains a compound called thiocyanate. The inhibitory effects of thiocyanate on the uptake of iodide is through competitive inhibition of the iodide transport mechanism and may be responsible for the reduction of levels. Other substances in tobacco smoke that can impair thyroid function are hydroxypyridine metabolites, nicotine and benzapyrenes. Tobacco smoke not only has an effect on thyroid function, but can also block thyroid hormone action. (13)
  • People drinking Fluoridated and Chlorinated water – Most tap water contains fluoride and chlorine, which inhibit the absorption of iodine. In a study where researchers used the Wechsler Intelligence Test to determine the IQs of a total of 329 eight- to 14-year-old children living in nine high-fluoride, low-iodine villages and in seven villages that had only low levels of iodine. As discovered, the IQs of children from the high-fluoride, low-iodine villages were lower than those from the villages with low iodine alone. (14)

An iodine deficiency can also be problematic since it can lead to your body’s inability to make sufficient amounts of the thyroid hormone. This can lead to negative effects like:34

  • Inhibited growth, brain development35,36 and sexual progression in babies born to an iodine-deficient mother
  • Very low IQ levels in infants and children
  • Reduced ability to work and think clearly among adults
  • Increased risk for brain damage37

Some iodine deficiency symptoms to watch out for include:

  • Swelling of the thyroid glands in the neck,38 producing a visible lump called a goiter39
  • Weakness or tiredness
  • Weight gain
  • Hair loss
  • Dry skin
  • Increased tendency to feel cold
  • Slower heart rate
  • Cognitive issues like low IQ levels and trouble learning40
  • Hypothyroidism or low thyroid levels41

An iodine deficiency can also trigger a rare but life-threatening hypothyroidism complication called myxedema. Warning signs include unconsciousness, goiter, reduced energy levels, seizures, confusion and coma.42 Myxedema requires immediate medical treatment, so if you notice someone exhibiting these symptoms, seek medical attention right away.43

Iodine rich-foods to try

To help manage your iodine levels, there are various foods high in this nutrient you can add to your diet, namely:

  • Sea vegetables like kelp, nori, kombu and wakame44  Iodine is highly abundant in the Earth’s oceans, especially among these sea vegetables.45 According to this 2014 study, out of the different seaweed varieties, kombu had the highest iodine content, followed by wakame and then nori.46
  • Organically grown cranberries or fresh cranberry juice — One ounce of cranberries (about one-third cup) contains 100 micrograms of iodine.47 Ideally, consume fresh and organic cranberries in moderation because they do contain 4.27 grams of fructose per cup.48 If you want cranberry juice, make your own drink at home, without added sugars, or by adding Stevia to it. One caveat: If you’re struggling with kidney stones, avoid consuming cranberry products because they contain oxalates that may trigger development of more stones.49 Mayo Clinic also advises that you avoid drinking cranberry juice if you’re taking warfarin (an anticoagulant medicine), because it may enhance this drug’s effects and increase your bleeding risk.50
  • Yogurt made from organic and grass fed milk51  Apart from being a good source of iodine,52 organic, grass fed yogurt is a good source of probiotics.
  • Dairy products, especially raw milk and grain products, are the major contributors of iodine to the American diet.

Based upon micrograms per serving and daily value (DV) of iodine, the top food sources of iodine include:

  1. Seaweed — Whole or 1 sheet: 16 to 2,984 micrograms (11 percent to 1,989 percent)
  2. Baked Cod — 3 ounces: 99 micrograms (66 percent)
  3. Cranberries — 1 ounce: 90 micrograms (60 percent)
  4. Plain Low-Fat Yogurt — 1 cup: 75 micrograms (50 percent)
  5. Baked Potato — 1 medium: 60 micrograms (40 percent)
  6. Raw Milk — 1 cup: 56 micrograms (37 percent)
  7. Shrimp — 3 ounces: 35 micrograms (23 percent)
  8. Navy Beans — ½ cup: 32 micrograms (21 percent)
  9. Egg — 1 large egg: 24 micrograms (16 percent)
  10. Dried Prunes — 5 prunes: 13 micrograms (9 percent)

To increase intake of iodine, try adding foods that are naturally high in iodine into your diet through the following recipes:

Iodine’s uses and health benefits

Your body needs iodine to facilitate production of thyroid hormones that aid in maintaining optimal metabolism and other important functions. This mineral, according to the National Institute of Health’s Office of Dietary Supplements, is particularly important if you’re pregnant or breastfeeding,53 since it can help babies grow and develop properly.54

Benefits of Iodine

  1. Controls Metabolic Rate. Iodine influences greatly the functioning of the thyroid glands by helping with the production of hormones directly responsible for controlling the body’s base metabolic rate. Metabolic rate ensures the efficiency of the body’s organ systems and biochemical processes, including sleep cycle, absorption of food and transformation of food into energy we can use. Hormones, like thyroxin and triiodothyronine, influence blood pressure, heart rate, body temperature and weight. The basal metabolic rate is maintained by the body with the help of these hormones, which also plays a role in protein synthesis. (20)
  2. Maintains Optimal Energy Levels. Iodine plays a vital role in maintaining optimal energy levels of the body by the utilization of calories, without allowing them to be deposited as excess fat.
  3. Helps Prevent Certain Kinds of Cancer. Iodine plays a role in boosting immunity and inducing apoptosis, the self-destruction of dangerous, cancerous cells. While iodine assists in destroying mutated cells, it doesn’t destroy healthy cells in the process. Evidence shows the ability of iodine-rich seaweed to inhibit growth of breast tumor development. (21) This is supported by the low rate of breast cancer in parts of world, especially in Japan, where women consume a diet rich in iodine. If you notice breast changes in your breast tissue, it could be a sign of iodine deficiency. Bromine plays a role here as well, as research shows bromine is a suspected carcinogen that “may exacerbate iodine insufficiency since bromine competes for iodine uptake by the thyroid gland and other tissues (i.e. breast).” (22)
  4. Removes Toxic Chemicals. Iodine can remove heavy metal toxins like lead, mercury and other biological toxins. Accumulating evidence suggests there are many extrathyroidal benefits of iodine, including antioxidant functions, maintaining the integrity of the mammary gland as well as antibacterial properties, particularly against H. pylori, which is a bacterial infection in the stomach and associated with gastric cancer. (23)
  5. Boosts Immunity. Iodine doesn’t just affect the thyroid; it does many other things, including playing an important role as an immune booster. Iodine is a scavenger of free hydroxyl radicals and stimulates and increases the activity of antioxidants throughout the body to provide a strong defensive measure against various diseases, including cancer and cardiovascular disease. Recent studies have shown that iodine directly protects the brain cells of rats from the harmful effects of free radicals by bonding onto fatty acids in the cell membrane, leaving less room for free radicals to have a negative impact on the organism. (24)
  6. Forms Healthy and Shiny Skin. Dry, irritated and rough skin that becomes flaky and inflamed is a common sign of iodine deficiency. Iodine helps with the formation of shiny and healthy skin, hair and teeth and is an important trace element, as a lack of iodine results in hair loss. A clinical study performed in Mexico wanted to determine the trace elements of healthy hair in malnourished children. Iodine levels were 10-fold higher than what has been reported by other authors. (25)
  7. Prevents Enlarged Thyroid Gland. Iodine deficiency is widely recognized as the primary cause of goiter. In fact, according to a meta-analysis out of China, lower urinary iodine concentration values “were associated with an increased risk of goiter, and … iodine deficiency may lead to an increased risk of goiter.” (26) Add sea salt, seafood, raw milk and eggs to your diet to avoid iodine deficiency, as this often also works as a preventative step of an enlarged thyroid gland.
  8. Helps Prevent Impaired Development and Growth in Children. Studies have shown that iodine deficiency during infancy and pregnancy can interrupt healthy brain development and growth. Infants are more susceptible to mortality and high risk for neurodegenerative problems if iodine-deficient, such as a mental form of disability known as cretinism, motor function problems, learning disabilities and low growth rate. In fact, according to research published by professors at the University of Sydney in Australia and the Swiss Federal Institute of Technology in Sweden, “Brain damage and irreversible mental retardation are the most important disorders induced by iodine deficiency.” (27) It’s difficult to get an accurate reading of iodine levels, even though doctors commonly test women for iodine deficiency during pregnancy. It’s encouraged by health care professionals for women to increase their supplementation with iodine and intake of iodine-rich foods to prevent these deficiencies.

Breast milk is a good iodine source for babies.55 However, the amount of iodine in breast milk relies on the mother’s intake of this mineral. According to WebMD, iodine may also:56

  • Help inhibit iodine deficiency and complications linked to it
  • Relieve cutaneous sporotrichosis, a skin disease caused by the Sporothrix fungus57
  • Address fibrocystic breast disease
  • Alleviate diabetic ulcers
  • Deliver expectorant capabilities
  • Lower someone’s risk for eye disease, diabetes, heart disease and stroke
  • Eliminate fungi, bacteria and amoebas
  • Purify water
Topical iodine applications may also aid in eliminating germs and reducing your risk for chemotherapy-caused mucositis, or soreness inside the mouth.58

Studies on iodine

One study found that iodine may help reduce the risk of cardiovascular diseases like hypercholesterolemia. The study, published in The Journal of Nutrition in September 2015, noted that iodine supplementation may reduce hypercholesterolemia risk in overweight women with a moderate to severe iodine deficiency.59

As mentioned above, iodine is also crucial to a child’s well-being, as iodine deficiency may lead to impaired neurodevelopment in children. According to a July 2017 study in The Journal of Nutrition, women whose maternal iodine intake levels fell below the Estimated Average Requirement during their pregnancy may bear children who’ll develop issues like language delays, behavior problems and decreased fine motor skills once they turn 3 years old.60

Furthermore, being deficient in this mineral may increase the risk for thyroid cancer. Results from a study published in Thyroid Research in June 2015 suggested that an iodine deficiency is a possible risk factor for thyroid cancer, follicular thyroid cancer (FTC) and anaplastic thyroid cancer (ATC).61

Iodine side effects to watch out for

If you’re interested in taking iodine supplements, it’s imperative to talk to your doctor to determine the ideal dosage for your condition. This may help lessen your risk for adverse effects like iodine overdose and acute iodine poisoning.62

Consuming high amounts of iodine can lead to hypothyroidism,63 which may block thyroid hormone production. Other side effects of taking a very large dose of iodine include:64

  • Goiter, or enlarged thyroid gland
  • Thyroid gland inflammation
  • Higher risk for thyroid cancer
  • Metallic taste
  • Soreness of teeth and gums
  • Worsening of conditions like hypothyroidism, goiter or thyroid tumor65
  • Burning sensations in your mouth, throat and stomach
  • Fever
  • Stomach pain
  • Nausea
  • Vomiting
  • Diarrhea
  • Weak pulse
  • Coma
Some people may not tolerate iodine or products containing it, like those diagnosed with an autoimmune thyroid disease. If you’re sensitive to iodine, the following complications could develop:66
  • Severe bleeding and bruising
  • Joint pain
  • Face and lip swelling
  • Contact dermatitis, a type of itchy rash that gradually develops
  • Urticaria or hives67

If you’re struggling with a rash called dermatitis herpetiformis, be aware that iodine could exacerbate this health issue.68 Medical News Today adds that an iodine intolerance may be fatal since it might trigger anaphylaxis, which could progress into a life-threatening anaphylactic shock. This is a sudden allergic reaction characterized by hives, low blood pressure, dizziness or lightheadedness, palpitations and breathing difficulties.69

According to the National Institutes of Health’s Office of Dietary Supplements, there can also be instances wherein iodine supplements may interact with medicines you’re taking:70

  • Anti-hyperthyroidism medicines like Methimazole (Tapazole) — Taking iodine supplements alongside antithyroid medications may deplete your body’s production of this important hormone.
  • ACE inhibitors like benazepril (Lotensin), lisinopril (Prinivil and Zestril) and fosinopril (Monopril) — ACE inhibitors are recommended for people with high blood pressure levels. If you take iodine supplements alongside ACE inhibitors, there’s a risk that the potassium in your blood may rise to an unsafe level.
  • Potassium-sparing diuretics like spironolactone (Aldactone) and amiloride (Midamore) — Using potassium iodide supplements together with potassium-sparing diuretics can significantly raise your blood’s potassium content.

Inform your doctor before using iodine supplements, especially if you have a medical condition, so they can advise whether your current medicine will interact with the supplement without causing any side effect.

Iodine is an effective mineral for your health

Iodine is crucial in maintaining ideal health and well-being, but most people take it for granted and don’t monitor their daily intake of this mineral. This leads to iodine deficiency, which now affects millions of people globally.

You can avoid iodine deficiency by eating iodine-rich foods or taking high-quality supplements and multivitamins containing this mineral. However, always exercise caution about raising your iodine intake, since this mineral has been linked to side effects, some of which are life-threatening and could exacerbate your condition.

Frequently asked questions (FAQs) about iodine

QWhat does iodine do?

A: Your body needs iodine because this mineral can help:71

  • Produce vital thyroid hormones
  • Promote babies’ development
  • Improve cognitive function during childhood
  • Lessen risk for radiation-induced thyroid cancer

Q: What is iodine used for?

A: Some of iodine’s uses include:72

  • Acting as an expectorant
  • Removing fungi, bacteria and amoebas from your body
  • Purifying water
  • Alleviating fibrocystic breast disease
  • Helping address cutaneous sporotrichosis, which is a skin disease caused by the Sporothrix fungus73

Q: Is iodine a metal?

A: According to LiveScience, iodine is a nonmetal, although it does exhibit some metallic qualities.74

Q: Where do you get iodine?

A: You can increase your body’s iodine stores by consuming foods high in iodine or taking high-quality supplements or multivitamins containing this mineral.75

Q: What foods have iodine?

A: Iodine-rich foods you can add to your diet include kelp, nori, wakame and other sea vegetables,76 organically grown cranberries or fresh cranberry juice77 and grass fed yogurt.78,79

Q: Does sea salt have iodine?

A: Yes, but in very low qualities.80 However, sea salt, which is usually minimally processed, has some amounts of calcium, magnesium and potassium.81

Q: Is iodine poisonous?

A: Iodine can be poisonous and can have dangerous side effects if you take too much of it.82,83,84 Before taking iodine supplements or significantly increasing your intake of iodine-rich foods, talk to a doctor to know about the amounts your body may need to prevent adverse effects.

Q: How much iodine do I need?

A: According to the National Institutes of Health’s Office of Dietary Supplements, the amount of iodine that you need typically depends on your age. The upper limits for an adult are 1,100 micrograms.85