If you’re anything like me, you hear the word “iodine” and you think “thyroid” and that’s about it. I’d always heard the thyroid needs iodine and that it’s so important they started fortifying salt with it, but I didn’t know the details.
If you’re in the same boat, this post is for you. We’re going over everything you need to know about this important trace element and by the end, you’ll know more than you’ll ever need.
What does iodine do?
You guessed it, iodine is essential for normal thyroid function, and here’s why. In order to make thyroid hormones, the thyroid needs to use iodine from the blood. Triiodothyronine (T3) is a thyroid hormone used to regulate gene expression, growth, development, metabolism, and reproductive function. Thyroxine (T4) is another thyroid hormone whose main job is to be available to be converted into T3 when needed. When T4 levels in the blood decrease, the pituitary gland starts secreting thyroid-stimulating hormone (TSH), which stimulates the thyroid to start trapping iodine to be able to use it in making more T4. However, when there is not enough iodine, the body is not able to make enough T4. This lack of T4 causes the pituitary to release even more TSH. When TSH is chronically high, the thyroid gets enlarged and then you’ve got a thyroid problem.
Deficiency
Iodine deficiency is the most common cause of preventable brain damage in the world. According to the WHO, over 30% of the world does not consume enough iodine. Most of the earth’s iodine is found in the oceans, while mountainous regions and flooded river valleys are among the most severely iodine-deficient areas in the world. Beginning in the 1990s, many countries around the world have iodized their salt to address the concern of iodine deficiency.
One of the earliest signs of iodine deficiency is a goiter, or enlarged thyroid. In mild cases of deficiency, this growth is enough to solve the issue. However, more severe cases lead to hypothyroidism.
Fetal iodine deficiency occurs when there is a deficiency in the pregnant mother. This can cause congenital hypothyroidism, which leads to learning disability, physical retardation, and deafness in the most severe cases.
In newborns and infants, sufficient iodine intake is essential for normal brain development. A deficiency may lead to impaired intellectual development.
For children and adolescents, iodine deficiency often shows up as a goiter. School-aged children without sufficient iodine intake show lower IQs, poorer school performance, and more learning disabilities.
Adults experiencing iodine deficiency may notice the effects of hypothyroidism first. Symptoms such as slower response time, impaired mental function, fatigue, weight gain, cold intolerance, and constipation may be present.
Increased incidence of miscarriage, stillbirth, and birth defects are all associated with iodine deficiency in pregnancy. Additionally, infants who are breastfeeding need sufficient iodine from breast milk to support their developing brain. A daily prenatal vitamin containing 150 micrograms of iodine is recommended for pregnant and breastfeeding women, who have increased need of iodine.
Individuals at Risk of Iodine Deficiency
Vegetarian diets and diets that exclude iodized salt, fish, and seaweed contain very little iodine. If your diet looks like that, consider consuming more iodine. Additionally, smoking tobacco is associated with greater risk of goiter in iodine-deficient areas.
Nutrient Interactions
Selenium, vitamin A, and iron each support and play a role in the function of iodine and a deficiency of any may exacerbate the effects of iodine deficiency.
Goitrogens
Goitrogens are foods that contain substances that interfere with iodine utilization. Some of these foods include cassava, millet, cabbage, broccoli, cauliflower, brussel sprouts, and soybean isoflavones. However, consuming these foods should not be a problem unless they are consumed in large amounts or you already have an iodine deficiency.
Disease Prevention
Radioactive iodine may be released into the environment after a nuclear reactor accident. Those with insufficient iodine are more likely to absorb up this radioactive iodine, and thus more likely to develop radiation-induced thyroid cancer. Taking potassium iodide shortly before or after exposure to radioactive iodine has been shown to decrease the chance of developing this cancer.
Disease Treatment
There have been a few studies showing treatment with high doses of aqueous molecular iodine to be effective in fibrocystic breast conditions (noncancerous lumpiness and discomfort in the breasts).
Food Sources
Since iodine content of food largely depends on the iodine content of the soil it was grown in, and many soils are depleted, it’s hard to know exact quantities. In general, seafood is the best source of iodine since the ocean is full of it. Dairy products may be higher in iodine because iodine is often added to animal feed.
Supplementation
Iodine supplements are typically part of a combination product such as a multivitamin. Potassium iodide and potassium iodate are used when iodizing salt. It is rare to get too much iodine in a natural diet, and you would need to take many grams of iodine to reach acute poisoning levels. However, the upper limit for iodine intake has been set at 1100 micrograms. Prolonged intake of more than 18,000 micrograms a day can increase the incidence of goiter.
And there you have it. Iodine is a wonderful part of our world and all our thyroids are singing its praises.
Resources
Higdon, Jane and Victoria J. Drake, “An Evidence-based Approach to Vitamins and Minerals,” 2nd Edition, 2012
