Iodine is an important trace mineral that plays a crucial role in supporting human health. Ensuring adequate iodine levels is important for maintaining healthy bodily functions, particularly for thyroid health. This article will discuss what iodine is, how it affects the body, how to test for it, and how to support proper levels.
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What is Iodine?
Iodine was first discovered in the 1800s by French chemist Bernard Courtois. Courtois was making gunpowder when sparks of a violet substance, what we now know as iodine, emitted. The name "iodine" comes from the Greek word ioeidēs, which means purple.
Iodine is a trace mineral essential for human health; however, we do not innately make it. Iodine is found in soil. Soils contain iodine levels that will penetrate into crops, thus supplying us with iodine. However, there are many areas of iodine soil depletion. Because of this, iodization programs have been implemented in many countries to help maintain adequate iodine levels. Iodization programs involve enriching the food supply with iodine, primarily through iodized salt.
What is Iodine's Role in The Body?
Iodine is important for supporting proper thyroid functioning. The pituitary gland releases thyroid-stimulating hormone (TSH). TSH helps maintain levels of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), which are important for overall health. TSH release causes iodine to be taken up by the thyroid for use in the creation and release of T4 and T3.
Iodine deficiency typically occurs when a person receives less than 20 micrograms (mcg) of iodine daily. Lack of iodine can cause the thyroid gland to become enlarged, referred to as a "goiter." The enlargement is the thyroid's way of trying to catch and keep more iodine from the circulation to make thyroid hormones. Additionally, in a state of iodine deficiency, T4 and T3 are not readily made, and TSH will remain elevated, which may contribute to symptoms associated with low thyroid hormone levels. These symptoms can include fatigue, weight gain, cold intolerance, hair loss, constipation, brain fog, low libido, and mood changes.
People who do not use iodized salt, pregnant women, people who do not consume meat, dairy, seafood, and eggs regularly, and people who live in areas with iodine-deficient soil may be at risk for low iodine levels. Additionally, people with lower iodine levels but who consume high amounts of goitrogen-containing foods are also at risk. Goitrogens are substances that may interfere with the uptake of iodine by the thyroid gland. Common goitrogen-containing foods include cassava, soy, and cruciferous vegetables, including broccoli, kale, and cabbage.
Excess iodine can occur due to over-supplementation, consumption of certain medications, and excess amounts of iodized salt in the diet. High amounts of iodine can lead to increased thyroid hormone production. Symptoms associated with high thyroid hormone levels include rapid heart rate, weight loss, heat intolerance, anxiety, and hair loss. Extremely high amounts can lead to iodine toxicity and result in discomfort in the mouth and throat, excess saliva production, a metallic taste in the mouth, fever, nausea, vomiting, skin changes, and may eventually lead to more serious health concerns.
However, high amounts of iodine can also lead to goiter and low thyroid hormone levels.
Excessive iodine may also cause an autoimmune reaction to occur against the thyroid gland, and high iodine levels may also be associated with thyroid health concerns. Lastly, excess iodine can lead to the Wolff-Chaikoff effect, where the thyroid reduces its uptake of iodine, potentially affecting thyroid hormone levels.
Because of its effects on thyroid physiology, iodine is especially important for pregnant women and infants, as a lack of iodine can impact brain development in these populations. Iodine deficiency in pregnant women can affect fetal growth and development. Additionally, iodine deficiency can be associated with developmental concerns, including cognitive and physical changes.
Additionally, mild iodine insufficiency in pregnant women may be associated with attention and behavioral concerns in children, and iodine deficiency in children can be linked to learning and developmental challenges.
How to Test Iodine Levels
Testing for iodine deficiency will differ from testing for iodine excess. Iodine deficiency is best checked by doing a 24-hour urine sample. This is because iodine levels will fluctuate throughout the day; thus, one sample may be misleading. An AM and PM dried urine sample may also be used to check iodine levels and may be easier for the patient as opposed to the 24-hour collection. It is important to monitor or be aware of large intakes of iodine while testing occurs, as 90% of the iodine in the diet will end up in the urine.
A blood test is preferred in cases of suspected high iodine levels, as it is quicker than a 24-hour urine or dried urine test, and the results of excessive iodine can be an emergency.
Additional labs, including a full thyroid panel and ultrasound, may also be indicated to fully assess iodine levels by having a complete picture of thyroid functioning. Autoimmunity may result in the case of high iodine, and thus thyroid antibodies should also be checked.
How to Make Sure You are Getting Enough Iodine in Your Diet
The Recommended Daily Allowance (RDA) is the daily intake needed to meet nutritional requirements. The RDA for iodine is dependent upon age:
Additionally, pregnant and lactating women require higher intakes of iodine. The RDA for pregnant women is 220 mcg, and the RDA for lactating women is 290 mcg.
Due to a lack of evidence, there is no RDA for children under one year old. However, levels of Adequate Intake (AI), a measurement indicating an amount of vitamin or mineral assumed to give sufficient nutrient status, have been established for those under one year old. The AI from birth to six months is 110 mcg, and the AI from seven to 12 months is 130 mcg.
Iodine can be found naturally in certain foods and can also be found in processed foods due to the introduction of iodine fortification in the food system.
Foods Naturally High in Iodine
Processed Foods High in Iodine
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Summary
Iodine is important for supporting human health due to its role in thyroid physiology. Both low and high iodine levels can impact thyroid health, which in turn can affect overall well-being. Iodine is particularly important for pregnant women and children, as adequate iodine levels support healthy development. Testing iodine levels can be helpful for those concerned about their iodine status and can provide insights into thyroid health.
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