Iodine is a trace mineral commonly found in seafood, dairy products, grains and eggs.
In many countries, it’s also combined with table salt to help prevent iodine deficiency.
Your thyroid gland uses iodine to produce thyroid hormones, which aid in tissue repair, regulate metabolism and promote proper growth and development
Thyroid hormones also play a direct role in the control of body temperature, blood pressure and heart rate
In addition to its essential role in thyroid health, iodine may play a central role in several other aspects of your health.
For example, test-tube and animal studies suggest that it may directly impact the function of your immune system
Meanwhile, other studies have found that iodine may help treat fibrocystic breast disease, a condition in which non-cancerous lumps form in the breast
Unfortunately, many people around the world are at an increased risk of iodine deficiency.
It's considered a public health problem in 118 countries, and more than 1.5 billion people are believed to be at risk
Deficiencies in micronutrients like iodine are increasingly prevalent in certain areas, especially in regions where iodized salt is uncommon or there are low levels of iodine in the soil.
In fact, it’s estimated that about a third of the population in the Middle East is at risk of iodine deficiency
This condition is also commonly found in areas such as Africa, Asia, Latin America and parts of Europe
In addition, certain groups of people are more likely to be deficient in iodine. For example, women who are pregnant or breastfeeding are at a higher risk of deficiency because they require more iodine.
Vegans and vegetarians are also at a greater risk. One study looked at the diets of 81 adults and found that 25% of vegetarians and 80% of vegans had iodine deficiency, compared to just 9% of those on mixed diets
A deficiency in iodine can cause a long list of symptoms that range from mildly uncomfortable to severe to even dangerous.
Among the most common symptoms is a type of swelling in the neck known as a goiter.
Your thyroid gland uses iodine to produce thyroid hormones. However, when your body doesn’t have enough of it, your thyroid gland is forced to go into overdrive to try to compensate and make more hormones.
This causes the cells in your thyroid to rapidly multiply and grow, resulting in a goiter
A decrease in thyroid hormones can also lead to other adverse effects, such as hair loss, fatigue, weight gain, dry skin and increased sensitivity to cold
Iodine deficiency may cause serious issues in children and pregnant women as well. Low levels of iodine can cause brain damage and severe problems with mental development in children
What’s more, it may also be associated with a higher risk of miscarriages and stillbirth
In 1917, physician David Marine began conducting experiments demonstrating that taking iodine supplements was effective at reducing the incidence of goiters.
Soon after in 1920, many countries around the globe began fortifying table salt with iodine in an effort to prevent iodine deficiency.
The introduction of iodized salt was incredibly effective at eliminating the deficiency in many parts of the world. Prior to the 1920s, up to 70% of children in certain areas of the United States had goiters.
In contrast, today 90% of the US population has access to iodized salt, and the population is considered overall iodine sufficient
Just a half teaspoon (3 grams) of iodized salt per day is enough to meet your daily iodine requirement
This makes using iodized salt one of the easiest ways to prevent iodine deficiency without having to make other major modifications to your diet.
Studies show that iodine intake above the daily recommended value is generally well tolerated.
In fact, the upper limit of iodine is 1,100 micrograms, which is the equivalent to 6 teaspoons (24 grams) of iodized salt when each teaspoon contains 4 grams of salt
However, excessive intake of salt, iodized or not, is not advised. The World Health Organization (WHO) recommends less than 5 grams of salt per day for adults
Therefore, you will exceed the safe level of salt intake long before you exceed your daily recommended dose of iodine.
A high intake of iodine may increase the risk of thyroid dysfunction in certain groups of people, including fetuses, newborn babies, the elderly and those with preexisting thyroid disease.
Excess iodine intake can be a result of dietary sources, iodine-containing vitamins and medications and taking iodine supplements
That said, multiple studies have reported that iodized salt is safe with minimal risk of adverse side effects for the general population, even at doses nearly seven times the daily recommended value