The Harmful Deficiency that Affects a Staggering Portion of the Population

Evidence Based

By Krystal Crawford, ND, MS

October 10, 2023

Did you know that iodine deficiency “is one of the most common nutrient deficiencies and is estimated to affect 35–45% of the world’s population,” according to research published in 2022, or that it’s “estimated to affect 2.2 billion people”? It’s true, but it doesn’t have to be this way.

Iodine is 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. This adversely affects the muscles, heart, liver, kidney and the developing brain.

The term iodine deficiency disorders has been coined to represent the different array of disorders that result from iodine deficiency in a population. These disorders are all preventable if the appropriate dose of iodine is administered.

Common disorders that result from iodine deficiency include:

• hypothyroidism
• increased cholesterol levels
• endemic goiter
• cretinism
• decreased fertility rate
• increased infant mortality
• fibrocystic breast disease
• atherosclerosis
• breast cancer

Iodine Deficiency Symptoms

Clinical signs and symptoms of iodine deficiency include: (6)

• Depression
• Swelling in the neck (goiter) or thyroid glands
• Changes in heart rate
• Difficulty losing weight or unexpected weight gain
• Dry skin
• Headaches
• Lethargy or fatigue
• Memory problems
• Menstrual problems
• Hyperlipidemia
• Recurrent infections
• Sensitivity to cold
• Cold hands and feet
• Brain fog
• Thinning hair or hair loss
• Constipation
• Shortness of breath
• Impaired kidney function
• Muscle weakness and joint stiffness
• Pregnancy issues

Risk Factors

When iodine intake becomes severely low, the thyroid compensates for the decreased levels by developing a swollen thyroid gland with nodules, known as a goiter, in order to absorb as much available iodine. The FDA currently has set recommended daily allowance (RDA) for iodine at 150 micrograms, which is efficient enough to eliminate goiters that are prevalent in iodine-deficient areas.

The following are potential risk factors that may lead to iodine deficiency.

1. Low Dietary Iodine

Soils from mountainous areas — such as the Alps, Andes and Himalayas — and areas with frequent flooding are likely to be deficient in iodine. Food grown in iodine-deficient soils rarely provide enough iodine to the livestock and population inhabiting there.

Unlike nutrients such as calcium, iron or other vitamins, iodine does not occur naturally in specific foods. Rather, it is present in the soil and ingested through foods grown on that soil.

In the early 1920s, Switzerland was the first country to fortify table salt with iodine to control cretinism and endemic goiter. In the 1970s and 1980s, controlled studies showed that iodine supplementation before and during pregnancy not only improved cognitive function in the rest of the population, but eliminated new cases of cretinism.

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Iodine is obtained primarily through diet but can be obtained from iodine supplementation. In food that is found primarily in sea life, iodine is absorbed into the body through the consumption of sea vegetables and seafood. Other food sources, such as nuts, seeds, beans, turnips, garlic and onions, are good sources, provided that the soil contains sufficient quantities of iodine.

2. 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 works harder to produce thyroid hormones, and the body has 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.

3. Pregnancy

Iodine is a crucial micronutrient for growth and development, particularly since it has a great effect on thyroid hormones.

Severe iodine deficiency is associated with stunted mental and physical growth, and even marginal iodine deficiency can impair brain functioning in infants.

4. Tobacco Smoke

Tobacco smoke contains a compound called thiocyanate. The inhibitory effects of thiocyanate on the uptake of iodide are 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.

5. Fluoridated and Chlorinated Water

Tap water contains fluoride and chlorine, which inhibit the absorption of iodine. In a study, 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. The IQs of children from the high-fluoride, low-iodine villages were lower than those from the villages with low iodine alone. 

6. Goitrogenic Foods

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.

How to Treat/Prevent

Best Sources of Iodine

Iodine Supplements and Iodine Salts

Salt iodization, also known as universal salt iodization, programs are put into place in more than 70 countries, including the U.S. and Canada, and 70 percent of households worldwide use iodized salt. The intention of U.S. manufacturers iodizing table salt in the 1920s was to prevent iodine deficiencies.

Potassium iodide and cuprous iodine have been approved by the FDA for salt iodization, while WHO recommends potassium iodate due to it having greater stability.

In the United States, iodized salt contains 45 micrograms iodine per gram of salt, which can be found in one-eighth to one-fourth teaspoon. Non-iodized salt is almost always used by food manufacturers, considering the majority of the salt intake comes from processed foods.

This is one of the reasons, however, that I recommend that you use benefit-rich sea salt instead and get your iodine through it, along with certain foods and supplementation rather than iodizing table salt. Sea salt (Himalayan or Celtic salt) contains more than 60 trace minerals and doesn’t pose a risk for overconsuming iodine like table salt can.

Furthermore, the benefits of universal salt iodization (USI) still require more research. Research published in the journal Nutrients examined a national cross-sectional study of iodine status among school-aged children in Tunisia, a country that adopted USD two decades ago. The researchers concluded:

Our adequacy assessment of the Tunisian USI program showed that, regarding the UIC impact indicator, the program achieved its objectives: ID national rates are now well below the target criteria of WHO certification (though with important geographic disparities). On the other hand, our study underlined that the coverage of households by adequately iodized salt, falls short of the target of certification. This inadequacy, due to a large variability of salt iodine content, also has adverse consequences, in that a non-negligible proportion of the population features an excess of iodine.

Most of the multivitamin/mineral supplements contain the forms of sodium iodide or potassium iodine. Dietary supplements of iodine-containing kelp or iodine are also available.

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

Final Thoughts

• Iodine is 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 muscles, heart, liver, kidney and the developing brain.
• Symptoms of iodine deficiency include depression, difficulty losing weight, dry skin, headaches, lethargy or fatigue, memory problems, menstrual problems, hyperlipidemia, recurrent infections, sensitivity to cold, cold hands and feet, brain fog, thinning hair, constipation, shortness of breath, impaired kidney function, muscle weakness, and joint stiffness.
• Risk factors for iodine deficiency include low dietary iodine, selenium deficiency, pregnancy, tobacco smoke, fluoridated and chlorinated water, and goitrogen foods.
• The RDA for iodine is 150 micrograms a day for adults and teens over 14 years old, and pregnant or breastfeeding mothers should consume 290 micrograms every day.