In This Article
By Astrid N Espino, PhD
Only thirty of the ninety-four naturally occurring elements on Earth are essential for life, and iodine is one of them.
Despite the small quantities required in our bodies (approximately 0.02 mg per kg), the contribution to our health is enormous.
Primarily, iodine is involved in the production of hormones in the thyroid—the butterfly-shaped organ in front of the throat. These hormones are needed in all stages of life to regulate growth, development, metabolism, and brain function, among many other vital processes.
The role of iodine is not limited to hormone production in the thyroid. Depending on its chemical form and amount, iodine may help improve health in several ways, including supporting the innate immune system, increasing the antioxidant potential of the body, and even counteracting cellular damage following exposure to nuclear radiation.1
Iodine Deficiency Disorders
Iodine is abundant in ocean sediment, sedimentary rocks, seawater, and even sea breeze. Thus, people living by the sea benefit most from iodine exposure, especially if they consume seafood. On the other hand, people living in inland areas, mountains, and other regions with low iodine content in the water, soils, and foods, are at risk of iodine deficiency disorders.
The most severe consequences of iodine deficiency occur in pregnancy and early childhood, where iodine deficiency contributes to pregnancy loss, natal mortality, congenital anomalies, and impaired brain function.
In adults, iodine deficiency risks include thyroid disorders (mainly hypothyroidism and goiter), metabolic diseases (eg, high blood pressure, diabetes, abdominal obesity, metabolic syndrome), cognitive deterioration and learning difficulties, and sensitivity to nuclear radiation.
Areas most affected by iodine deficiency include the Midwestern United States and South America, Europe, Asia, Africa, Southern Australia, and the Highlands of New Guinea.2 Since 1994, iodine has been added to table salt with remarkable results to help with iodine deficiency worldwide. However, it must be noted that iodine content in table salt can gradually decrease due to improper storage and heat (cooking). In this sense, the best way to prevent health problems is through supplementation.
Dosage
The recommended iodine intake in pregnant and breastfeeding women is 200-500 µg/day; 150 µg/day for adolescents and adults; 120 µg/day for school children (six to twelve years); and 90 µg/day for infants (zero to fifty-nine months).3 Breast milk already has high iodine content and protects the newborn so breastfed infants do not require any supplementation.
The amount of iodine in urine is an excellent way to determine iodine status. The most commonly used test measures the Urinary Iodine Concentration (UIC) from the early morning discharge. A more precise method examines the Urinary Iodine Excretion (UIE) in urine collected throughout the whole day (24 h). As always, consult a knowledgeable healthcare professional to accurately interpret lab test results and determine the optimal daily intake.
Iodine for an Extended Lifespan
Iodine status is so vital that it is considered a primary marker of nutrition and health. The relationship between iodine consumption and health is best demonstrated in Japan—a country with high life expectancy and high daily iodine intake (1,000–3000 µg). Also, Japan has low rates of infant deaths, cardiac diseases, and thyroid, breast, and prostate cancers.
Remarkably, the traditional Japanese diet may account for the health more than genetics. For instance, Japanese who move to the US have a higher risk for breast and prostate cancer (twenty-eight percent and twenty-three percent, respectively) just due to dietary changes.
The traditional Japanese diet is rich in seaweed, such as nori (Porphyra), wakame (Undaria), and kombu (Laminaria). These types of algae are the better accumulators of iodine in nature. Still, all seafood—fish, octopus, shrimp, crabs, shellfish, oysters—represent an excellent source of iodine since this nutrient abounds in the ocean.
Land-based iodine-rich foods include all dairy products, tubers (eg, turnips and saffron), beef kidney, green beans, eggs, yeast, and some condiments (eg, chili powder and mint). Of note, foods such as soy, cassava, and cruciferous vegetables (eg, cauliflower, kale, and cabbage) contain goitrogens—substances that interfere with the uptake of iodine in the thyroid—and can exacerbate iodine deficiency if not properly prepared.
Counteracting Infections and Diseases
Many disinfectants in the market contain molecular iodine (I2) as the active ingredient because of its potent bactericidal effect. Iodine-based products effectively kill parasites, fungi, bacteria, and viruses without losing efficacy over time. Recently, during the pandemic, iodine-based mouthwashes and antiseptics proved to reduce transmissions of COVID-19 in medical settings.
Beyond the topical application of iodine, circulating free iodine (I- and I2) in the body improves immune defenses. For instance, saliva, breast milk, and tears contain compounds (eg, lactoperoxidase enzymes) that stop microbial growth, but in combination with iodine, bacteria, and viruses are completely eradicated. Similarly, white blood cells produce some of those enzymes, and iodine helps them communicate and respond better to infections.
Iodine also acts by reducing cellular stress. More specifically, cells produce unstable molecules known as reactive oxygen species (ROS). While necessary in small amounts, excess ROS damages crucial components (DNA, lipids, and proteins), causing oxidative stress. Long-term, oxidative stress contributes to aging and disease, including thyroid disorders, metabolic diseases, and cancer.
Research shows iodine combats oxidative stress in several ways. Studies in cells, animals, and humans have demonstrated that free iodide (I-) and molecular iodine (I2) directly reduce oxidative stress by destroying ROS. These forms of iodine also activate novel protective mechanisms of the cell to minimize damage.
Preventing and Fighting Cancer with Iodine
Poor iodine status in the body is closely related to numerous diseases, including various types of cancer. One of the key factors in understanding iodine’s mechanism of action could be the ability of organs and cells to absorb and store free iodine (I- or I2). The best example is the thyroid, representing the organ with the highest oxidative stress and the storage of iodine in the body.
If there is insufficient iodine to control ROS, oxidative stress can damage the thyroid, contributing to the development of diseases, such as cancer. Amazingly, the effect of iodine is not only preventive but extends even after the cancer has developed. Research has shown that treatments with iodine may prompt the death of thyroid cancer cells but not normal ones.4
Generally, organs that tend to absorb and store more iodine are also affected by iodine’s anticarcinogenic effect. For example, tumors in the breasts, prostate, colon, pancreas, liver, ovary, or skin absorb more iodine than healthy organs. Interestingly, studies in cells and animals have demonstrated that high amounts of iodine kill breast and prostate cancer cells and reduce tumors in those organs. And more recently, high doses of iodine showed promising results as a complementary therapy for breast and prostate cancers.
Radioactive Iodine: Friend or Foe?
Iodine-127 is the only stable form of iodine in nature. Other variants (isotopes) are synthetically produced in nuclear reactors and emit radiation energy. In medicine, radioactive isotopes are used for a variety of purposes. Because iodine is easily seen by x-ray, radioactive iodine is used as a diagnostic tool (contrast medium) to help visualize organs and tissues. Also, by taking advantage of the high absorption in the thyroid, radioactive iodine helps treat hyperthyroidism and thyroid cancer by destroying the abnormal cells. Similarly, radioactive iodine is incorporated into some drugs to target radiation to specific organs and tissues for diagnosis or therapy.
On the other hand, radioactive iodine can be released during nuclear explosions into the environment, increasing the risk of thyroid cancer and autoimmune thyroiditis. Because the body does not differentiate between stable iodine and radioactive isotopes, they are equally absorbed in the thyroid. As such, following a nuclear disaster, a single high dose of stable iodine (up to 100 mg) can help block the thyroid from absorbing any iodine (radioactive or iodine-127) for one to two weeks. It is important to emphasize that high doses are for emergency use only to avoid potential permanent thyroid damage.
Conclusion
Maintaining a balanced iodine status is an important preventive strategy against several conditions, including hypothyroidism, reproductive risks, metabolic problems, and some types of cancer.
Additionally, iodine sufficiency helps support optimal brain functioning, strengthens the immune system, and even lessens the sensitivity to nuclear radiation. Thus, testing iodine levels and incorporating more iodine-rich foods in the diet can help prevent deficiency of this essential trace mineral.
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Astrid N Espino is a clinical researcher at Sanoviv Medical Institute (www.sanoviv.com). She is an enthusiastic scientist with a PhD in Biotechnology and professional experience in multiple biological disciplines. Also, she has a special interest in science dissemination and promoting health & wellness.
Iodine: A Micronutrient with Macro Potential is based on the recently published article “Implications and Practical Applications of the Chemical Speciation of Iodine in the Biological Context” by Astrid N Espino and colleagues in the scholarly journal Future Pharmacology.
References
- Espino-Vázquez AN, et al. “Implications and Practical Applications of the Chemical Speciation of Iodine in the Biological Context.” Future Pharmacology. 2022. https://doi.org/10.3390/futurepharmacol2040026
- Rohner, F, et al. “Biomarkers of Nutrition for Development—Iodine Review.” J. Nutr. 2014, 144, 1322S–1342S. https://doi.org/10.3945/jn.113.181974.
- WHO, UNICEF, ICCIDD. Review of Findings from 7-Country Study in Africa on Levels of Salt Iodization in Relation to Iodine De?ciency Disorders, Including Iodine-Induced Hyperthyroidism; Geneva, Switzerland, 1996.
- Aceves, C, et al. “Molecular Iodine Has Extrathyroidal Effects as an Antioxidant, Differentiator, and Immunomodulator.” Int. J. Mol. Sci. 2021, 22, 1228. https://doi.org/10.3390/ijms22031228.
