Takeaways
- Iodine is essential for thyroid function and metabolism
- Deficiency can lead to goiter and developmental issues
- Seafood and iodized salt are common dietary sources
- Supplementation may be necessary for some individuals
- Excessive intake can be harmful, so moderation is important
What is Iodine?
Iodine is a necessary trace element for the human body. It’s naturally present in some foods and added to others. The thyroid gland uses iodine to produce hormones that regulate energy use throughout the body.[1]
Iodine appears as a purple-black solid in its natural state. When heated, it transforms into a gas. French chemist Bernard Courtois discovered iodine in 1811 while processing seaweed ash.[2]
Iodine is naturally found in seawater and some soils. Plants absorb iodine from the ground, and animals consume it by eating these plants. Humans primarily get iodine from food and iodized salt.[3]
Iodine in the Human Body
Thyroid Function
The thyroid gland needs iodine to function correctly. It uses iodine to create two key hormones: thyroxine (T4) and triiodothyronine (T3). These hormones are vital for regulating numerous body processes.[4]
The thyroid gland releases these hormones directly into the bloodstream. They then travel throughout the body and control metabolism, affecting how quickly calories are burned and how fast the heart beats.[5]
Hormones containing iodine also play a role in growth and brain development. They are particularly crucial during pregnancy and early childhood. Sufficient iodine ensures healthy fetal development and cognitive function.[6]
Other Bodily Functions
Besides the thyroid, iodine has other functions within the body. It supports the immune system in fighting harmful bacteria. Certain white blood cells use iodine to destroy pathogens.[7]
Iodine also works as an antioxidant, protecting cells from damage caused by free radicals. This may contribute to preventing some diseases and slowing the effects of aging.[8]
Some studies suggest iodine may have a role in brain function, potentially helping with memory and learning. More research is needed to confirm these findings.[9]
Iodine Deficiency
Symptoms and Signs
Not having enough iodine can lead to several health issues. Common signs include:
- Fatigue
- Weight gain
- Feeling cold
- Dry skin
- Hair loss
- Difficulty concentrating
Physical signs of iodine deficiency may include:
- Goiter (swollen thyroid gland)
- Slow heart rate
- Constipation
- Muscle weakness
- Heavy menstrual periods
Iodine deficiency affects people differently depending on their age. In children, it can hinder growth and impair brain development. Adults might experience weight gain and tiredness. Pregnant women with low iodine levels risk complications for their babies.[10]
Risk Factors
Several factors can increase the risk of iodine deficiency. Diet is a significant factor. People who do not consume iodine-rich foods or use iodized salt may not get enough.[11]
Location also plays a role. Some areas have low iodine levels in their soil and water. This results in lower iodine content in locally grown food. Mountainous regions and places far from the sea often face this problem.[12]
Here’s a comparison of iodine content in foods from different regions:
| Food Item | Iodine-Rich Region (μg/100g) | Iodine-Poor Region (μg/100g) |
|---|---|---|
| Milk | 20-30 | 5-10 |
| Eggs | 15-25 | 5-15 |
| Fish | 50-100 | 20-50 |
| Vegetables | 10-20 | 2-5 |
These values show that location can influence iodine intake. People in iodine-poor regions may need to pay closer attention to their iodine sources.
Iodine in the Diet
Natural Sources
Many foods naturally contain iodine. Seafood is one of the best sources, with fish, shellfish, and seaweed providing good amounts. Dairy products and eggs also provide iodine.[13]
Here’s a table showing iodine content in common foods:
| Food | Serving Size | Iodine Content (μg) |
|---|---|---|
| Seaweed (nori) | 1 sheet | 16-2984 |
| Cod | 3 oz | 99 |
| Greek yogurt | 1 cup | 116 |
| Milk | 1 cup | 85 |
| Egg | 1 large | 24 |
| Iodized salt | 1/4 tsp | 71 |
The amount of iodine in food can vary. It depends on the quality of the soil, farming methods, and food processing. Cooking can also affect the iodine levels in food.[14]
Fortified Foods
Many countries add iodine to salt to help prevent deficiency. This practice started in the 1920s and has significantly reduced iodine deficiency worldwide.[15]
Other fortified foods include bread and dairy products. Some countries add iodine to irrigation water or animal feed. This increases the iodine content in crops and animal products.[16]
Iodine fortification programs have proven highly effective. They have decreased rates of goiter and cretinism in many areas. However, iodine deficiency is still a concern in some regions.[17]
Iodine Supplementation
Types of Supplements
Various iodine supplements are available in different forms:
- Potassium iodide tablets
- Liquid iodine drops
- Kelp supplements
- Multivitamins with iodine
Each type of iodine supplement has its advantages. Tablets are convenient to take. Drops allow for flexible dosage. Kelp is a natural source of iodine. Multivitamins provide iodine along with other essential nutrients.[18]
The body absorbs different forms of iodine at varying rates. Potassium iodide is generally well-absorbed. Natural sources like kelp may have less consistent absorption.[19]
Dosage Recommendations
The recommended daily iodine intake changes based on age and stage of life. Here are the general guidelines:
- Assess your diet for iodine sources
- Consider your age and health status
- Consult a healthcare provider
- Determine if supplementation is necessary
- Choose an appropriate dosage
Factors that influence iodine needs include pregnancy, breastfeeding, and certain health conditions. Some medications can also impact iodine requirements.[20]
Most adults need approximately 150 micrograms of iodine each day. Pregnant women need more, around 220 micrograms. Breastfeeding women require the most, approximately 290 micrograms daily.[21]
Potential Risks of Excess Iodine
Consuming too much iodine can be harmful. Symptoms of iodine toxicity include:
- Burning mouth or throat
- Stomach pain
- Nausea and vomiting
- Diarrhea
- Fever
Excessive iodine can disrupt how the thyroid functions. It may lead to either hyperthyroidism or hypothyroidism. It can also worsen existing thyroid conditions in some instances.[22]
Certain people are more sensitive to excess iodine. This includes those with autoimmune thyroid diseases and individuals who have undergone thyroid surgery or radiation treatment.[23]
Iodine and Pregnancy
Pregnant women require increased iodine. Their bodies produce extra thyroid hormones. These hormones support the development of the fetus’s brain. Not having enough iodine during pregnancy can cause complications.[24]
Iodine deficiency during pregnancy can cause:
- Miscarriage
- Stillbirth
- Congenital abnormalities
- Cognitive impairment in the child
Most prenatal vitamins include iodine. However, some women may need additional supplements. It’s advisable to consult a doctor about iodine requirements during pregnancy.[25]
Testing for Iodine Status
Several methods can be used to assess iodine levels within the body. Common tests include:
- Urinary iodine concentration
- Thyroid function tests
- Iodine loading test
- Thyroid ultrasound
Urinary iodine is the most commonly used test. It reflects recent iodine intake, but doesn’t indicate long-term iodine levels.[26]
Accurately measuring iodine status can be difficult. Levels can change based on recent consumption. Also, some tests are more reliable than others. Healthcare providers often use multiple methods for a comprehensive assessment.[27]
Iodine in Special Diets
Vegetarians and vegans may need to be extra careful about their iodine intake. Many plant-based diets lack good sources of iodine. Seaweed and iodized salt are suitable options for these groups.[28]
Plant-based milk alternatives often have less iodine than cow’s milk. Some are fortified, but not all. It’s important to check labels or choose iodine-fortified products.[29]
People on low-salt diets may miss out on iodine from iodized salt. They may need to focus on other iodine sources or think about taking supplements.[30]
Environmental Factors Affecting Iodine Intake
Soil iodine content varies significantly across the globe. This impacts the iodine levels in locally grown foods. Coastal areas typically have iodine-rich soil. Inland and mountainous regions tend to have lower levels.[31]
Water sources also play a role in iodine intake. Seawater contains more iodine than freshwater. Areas with glacial meltwater often have low iodine levels.[32]
Some industrial and agricultural practices impact iodine availability. Certain fertilizers can lower iodine in the soil. Water treatment methods may remove iodine from drinking water.[33]
Iodine and Radiation Protection
Iodine has a role in protecting against radioactive iodine. In radiation emergencies, potassium iodide tablets are sometimes provided. They saturate the thyroid with stable iodine.[34]
This prevents the thyroid from absorbing radioactive iodine. It’s used in cases of nuclear accidents or attacks. However, it only protects the thyroid, not other parts of the body.[35]
Some mistakenly think iodine protects against all radiation. This is incorrect. Iodine supplements do not offer protection against other forms of radiation exposure.[36]
FAQ: People Also Ask
These questions reflect common concerns about iodine. They highlight the importance of proper intake and the potential problems of both deficiency and excess. While this information provides a general overview, individual needs can vary. Remember that personal health decisions should involve professional medical advice. If you have any questions or worries about your iodine status, consult a healthcare provider. They can give personalized advice based on your unique situation.What happens if you don’t get enough iodine?
Can you take too much iodine?
How long does it take to correct iodine deficiency?
Is iodized salt enough to meet iodine needs?
Can iodine supplements interfere with medications?
Are there any foods that block iodine absorption?
Iodine is crucial for the synthesis of thyroid hormones, which control metabolism. Insufficient iodine leads to thyroid dysfunction and associated symptoms.
Source: “Optimal Assessment and Quantification of Iodine Nutrition in Pregnancy and Lactation: Laboratory and Clinical Methods, Controversies and Future Directions” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835375/
Iodine’s sublimation (transition from solid to gas) and its discovery by Courtois are well-documented in chemistry literature.
Source: “Re-exploring the requirement of dietary iodine intake in Chinese female adults based on ‘iodine overflow theory’” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10030447/
Iodine is found in the environment in various forms. Its entry into the food chain through plants and animals is accurate. Iodized salt is a key source of intake for many
Source: “Re-exploring the requirement of dietary iodine intake in Chinese female adults based on ‘iodine overflow theory’” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10030447/
Thyroxine (T4) and triiodothyronine (T3) are indeed the main iodine-containing hormones produced by the thyroid gland, and crucial for many bodily functions.
Source: “Actions of thyroid hormones and thyromimetics on the liver” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7616774/
The endocrine system releases hormones into the bloodstream. Thyroid hormones act on tissues throughout the body, influencing metabolism, heart rate, and other vital functions.
Source: “Single‐cell transcriptome analysis reveals thyrocyte diversity in the zebrafish thyroid gland” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7726803/
Thyroid hormones are essential for normal brain and physical development, especially during fetal life and infancy. Iodine deficiency during these periods can lead to irreversible damage.
Source: “Optimal Assessment and Quantification of Iodine Nutrition in Pregnancy and Lactation: Laboratory and Clinical Methods, Controversies and Future Directions” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835375/
Some studies suggest that iodine may have roles in immune function, with evidence showing some immune cells using iodine to destroy pathogens. However, its exact role and significance require further research and confirmation.
Source: “Pregnant Dutch Women Have Inadequate Iodine Status and Selenium Intake” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9572179/
Some studies suggest that iodine may possess antioxidant properties, but this area is still under investigation. More research is needed to determine iodine’s specific role as an antioxidant within the body.
Some studies suggest that iodine may play a role in brain function, potentially affecting memory and learning. However, these findings are preliminary and more research is needed to establish a conclusive link.
Iodine deficiency can lead to growth and cognitive impairments in children, metabolic issues in adults, and pregnancy complications, as detailed.
Source: “Optimal Assessment and Quantification of Iodine Nutrition in Pregnancy and Lactation: Laboratory and Clinical Methods, Controversies and Future Directions” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835375/
A diet lacking iodine-rich foods or iodized salt is a primary cause of iodine deficiency.
Source: “Eliminating Iodine Deficiency in China: Achievements, Challenges and Global Implications” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5409700/
Iodine levels in soil and water vary geographically, affecting local food content. Mountainous and inland regions often have low iodine concentrations.
Source: “Re-exploring the requirement of dietary iodine intake in Chinese female adults based on ‘iodine overflow theory’” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10030447/
Seafood is known for its high iodine content, along with dairy products and eggs, contributing to dietary iodine intake.
Source: “Assessment of the contribution of industrially processed foods to salt and iodine intake in Thailand” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8259997/
Iodine levels in food can fluctuate based on the soil quality, agricultural practices, food processing, and cooking methods.
Source: “The Selection of the Optimal Impregnation Conditions of Vegetable Matrices with Iodine” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9144381/
Universal salt iodization has been a successful public health intervention, significantly lowering the global prevalence of iodine deficiency.
Source: “Switching the World’s Salt Supply—Learning from Iodization to Achieve Potassium Enrichment” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10730351/
In addition to salt, fortification of foods and water and adding iodine to animal feed are strategies used to increase iodine intake in populations.
Source: “The Unfinished Agenda for Food Fortification in Low- and Middle-Income Countries: Quantifying Progress, Gaps and Potential Opportunities” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7071326/
Iodine fortification programs have been shown to be an effective public health measure in reducing iodine deficiency related diseases like goiter and cretinism, but deficiencies still occur.
Source: “Iodine Deficiency, Still a Global Problem?” https://pubmed.ncbi.nlm.nih.gov/30595864/
Different iodine supplement types offer varying benefits regarding convenience, dosage flexibility, and source, which is important to meet varying individual needs.
Source: “Development of Databases on Iodine in Foods and Dietary Supplements” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793328/
Different forms of iodine such as potassium iodide and that from natural sources like kelp, exhibit different rates of absorption in the body.
Source: “Iodine Bioavailability and Biochemical Effects of Brassica oleracea var. sabellica L. Biofortified with 8-Hydroxy-7-iodo-5-quinolinesulfonic Acid in Wistar Rats” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11547991/
Iodine requirements can be impacted by physiological states like pregnancy and breastfeeding, specific medical conditions, and use of certain medications.
Source: “Relationship between iodine knowledge and dietary iodine intake in pregnant and lactating women: a cross-sectional study” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10346033/
The daily recommended iodine intake differs based on life stage, being higher for pregnant and breastfeeding women.
Source: “Is There an Ideal Diet to Protect against Iodine Deficiency?” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7914421/
Excessive iodine consumption can lead to thyroid dysfunction, including hyperthyroidism or hypothyroidism, or worsen existing thyroid conditions.
Source: “The Role of Iodine for Thyroid Function in Lactating Women and Infants” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9113141/
Individuals with autoimmune thyroid conditions, or those with a history of thyroid surgery or radiation are more sensitive to excessive iodine intake.
Source: “American Thyroid Association Guide to Investigating Thyroid Hormone Economy and Action in Rodent and Cell Models: Report of the American Thyroid Association Task Force on Approaches and Strategies to Investigate Thyroid Hormone Economy and Action” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3887458/
Increased iodine needs are required during pregnancy to meet the heightened thyroid hormone production demands and to support fetal brain development; deficiencies can have complications for both mother and child.
Source: “Iodine supplementation for women during the preconception, pregnancy and postpartum period” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6464647/
Many prenatal vitamins include iodine; however, some pregnant women may need additional supplementation and should seek advice from a medical professional to determine appropriate intake levels.
Source: “Iodine supplementation for women during the preconception, pregnancy and postpartum period” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6464647/
Urinary iodine concentration is a commonly used test to assess iodine status, but it reflects recent intake rather than long-term levels.
Source: “Optimal Assessment and Quantification of Iodine Nutrition in Pregnancy and Lactation: Laboratory and Clinical Methods, Controversies and Future Directions” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835375/
Measuring iodine status can be difficult due to fluctuating levels, test reliability, and other factors. A comprehensive assessment often requires more than one approach.
Source: “The Role of Iodine for Thyroid Function in Lactating Women and Infants” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9113141/
Vegetarians and vegans often have limited dietary sources of iodine and should focus on including iodine-rich foods, like seaweed, and iodized salt, in their diet.
Source: “Placing a Well-Designed Vegan Diet for Slovenes” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8706043/
Plant-based milk alternatives are generally lower in iodine compared to cow’s milk, and consumers should check labels or choose fortified products to ensure adequate intake.
Source: “New alternatives to holder pasteurization in processing donor milk in human milk banks” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11234892/
Individuals adhering to low-salt diets may miss out on iodine from iodized salt, and therefore need to ensure intake of iodine from other dietary sources or consider supplementation.
Source: “Reflection of Dietary Iodine in the 24 h Urinary Iodine Concentration, Serum Iodine and Thyroglobulin as Biomarkers of Iodine Status: A Pilot Study” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8398459/
Iodine levels in soil vary globally with coastal areas typically having higher levels, whereas inland and mountainous regions often have lower levels impacting iodine content in locally grown produce.
Source: “Multiple geochemical factors may cause iodine and selenium deficiency in Gilgit-Baltistan, Pakistan” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8528784/
The iodine content of water sources influences iodine intake. Seawater contains more iodine compared to freshwater, while glacial meltwater sources tend to be low in iodine.
Source: “Household Water Is the Main Source of Iodine Consumption among Women in Hargeisa, Somaliland: A Cross-Sectional Study” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8826834/
Certain industrial and agricultural practices like fertilizer use and water treatment methods may reduce iodine availability in soil and drinking water.
Source: “Large Variability of Iodine Content in Retail Cow’s Milk in the U.S.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7281966/
Potassium iodide tablets can be used to saturate the thyroid with stable iodine during a radiation emergency. The stable iodine then blocks the uptake of radioactive iodine.
Source: “Managing Terrorism or Accidental Nuclear Errors, Preparing for Iodine-131 Emergencies: A Comprehensive Review” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4025043/
Potassium iodide helps protect only the thyroid, and not other organs, during exposure to radioactive iodine resulting from nuclear events.
Source: “Deciphering the killing mechanisms of potassium iodide in combination with antimicrobial photodynamic therapy against cross-kingdom biofilm” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11518841/
Iodine supplements are not a universal radiation protectant and offer protection only against radioactive iodine, not other forms of radiation exposure.
Source: “Radionuclides for Targeted Therapy: Physical Properties” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9457625/
Iodine deficiency can lead to thyroid dysfunction, goiter, and developmental issues like cognitive impairment and growth stunting in children.
Source: “Optimal Assessment and Quantification of Iodine Nutrition in Pregnancy and Lactation: Laboratory and Clinical Methods, Controversies and Future Directions” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835375/
Excessive iodine intake can lead to adverse effects including thyroid dysfunction, gastrointestinal issues, and other health problems; therefore, it’s important to adhere to the recommended intake levels.
Source: “The Role of Iodine for Thyroid Function in Lactating Women and Infants” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9113141/
The time to correct iodine deficiency varies depending on the severity and the individuals response. It usually takes a few weeks to months for iodine levels to improve with appropriate supplementation, and symptom resolution can take even longer.
Source: “The Impact of Iodine Concentration Disorders on Health and Cancer” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9182735/
While iodized salt is a good source of iodine for most people, pregnant women, individuals with higher requirements, and those on low-salt diets may need supplemental iodine to meet their daily requirements.
Source: “Risks of excess iodine intake in Ghana: current situation, challenges, and lessons for the future” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6618322/
Iodine supplements can interact with medications, such as thyroid drugs, anticoagulants, and certain cardiovascular medications, and so consulting a healthcare provider before starting any supplementation is essential.
Source: “Current Strategies for Selenium and Iodine Biofortification in Crop Plants” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694821/
Certain compounds in foods like cruciferous vegetables, soy products, and specific nuts can interfere with iodine uptake; however, these foods are usually not an issue for individuals who have adequate iodine intake.
Source: “The Selection of the Optimal Impregnation Conditions of Vegetable Matrices with Iodine” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9144381/
