Iodine, a trace mineral of great importance, plays a central role in essential physiological processes, establishing a harmonious balance within our bodies. Its significance stems from its vital role in the production of thyroid hormones—thyroxine (T3) and triiodothyronine (T4) — with each numeral reflecting the specific number of atoms attached to these hormones.
The impact of iodine extends far beyond its role in thyroid function alone. In fact, iodine is crucial for brain and nervous system development, especially during the critical stages of fetal growth and infancy. As a result, pregnant and breastfeeding women are strongly encouraged to increase their iodine intake in order to ensure their babies' normal brain development.
Iodine can be obtained from a variety of natural food sources. Seafood, such as fish and seaweed, is particularly rich in iodine. Dairy products, eggs, and grains like bread and cereal can also contribute to iodine intake. Furthermore, iodized salt, which has iodine added to it, is a common source of iodine in many households.
In cases where dietary intake may be insufficient, dietary supplements can help meet iodine requirements. These supplements provide a convenient way to ensure adequate iodine intake, especially for individuals with specific dietary restrictions or limited access to iodine-rich foods.
Surprisingly, an estimated two billion people worldwide experience insufficient iodine intake, often characterized by subclinical iodine deficiency that may not exhibit apparent symptoms, making it a silent threat to global health. The prevalence of iodine deficiency is particularly pronounced in regions such as South Asia and sub-Saharan Africa, where soils are inherently poor in iodine.
In this article, we cover the basics of iodine, including recommended daily allowances, highest dietary sources, health benefits, and potential deficiency symptoms.
Quick Facts About Iodine
How much Iodine do we need Daily?
1000 mcg = 1 mg
What are the Health Benefits of Iodine?
Beyond its crucial role in thyroid function, iodine serves several other essential functions in the body, including potential health benefits such as:
# Thyroid Hormone Production
Iodine plays a pivotal role in the synthesis of thyroid hormones, thyroxine (T4), and triiodothyronine (T3). These hormones are crucial for maintaining a healthy metabolism, regulating body temperature, and supporting the proper functioning of various organs and tissues.
When iodine levels are inadequate, the thyroid gland cannot produce sufficient thyroid hormones, leading to hypothyroidism, which can cause symptoms such as fatigue, weight gain, and dry skin.
Ensuring adequate iodine intake is essential for maintaining a healthy thyroid function and overall metabolic balance.
# Brain Development and Cognitive Function
During infancy and childhood, iodine is particularly critical for proper brain development and cognitive function. Adequate iodine levels support the growth of neurons and promote optimal cognitive abilities.
Children born to mothers with iodine deficiency during pregnancy may be at a higher risk of experiencing intellectual deficits and lower IQ scores.
Ensuring sufficient iodine intake during pregnancy and early childhood is vital for promoting optimal brain development and cognitive abilities.
# Reduces the Risk of Fibrocystic Breast Condition
Iodine is associated with fibrocystic breasts, a benign health condition characterized by lumpy and painful breasts that primarily affects women of childbearing age and during menopause.
While the exact cause of breast cysts is not fully understood, there is evidence suggesting that reproductive hormones, particularly high levels of estrogen, may play a role.
Several studies have shown promising results regarding the potential role of iodine supplementation in preventing and treating fibrocystic breasts, especially in individuals with low iodine levels.(4)
Iodine’s mechanism of action is believed to involve reducing the estrogen dominance, which may contribute to potential relief from fibrocystic breast symptoms.
It’s important to note that while research in this area is promising, more studies are needed to fully understand the extent of iodine’s impact on fibrocystic breast conditions.
# Essential For a Healthy Pregnancy
Iodine plays a crucial role during pregnancy, as iodine deficiency at this stage can lead to irreversible health effects for both the mother and the developing baby.
Pregnant women experience an increase in estrogen levels, which can contribute to a higher likelihood of thyroid dysfunction during this period. However, maintaining adequate iodine levels during pregnancy is believed to help counteract estrogen buildup and reduce the risk of estrogen dominance.
NHANES data indicates that pregnant women who avoid consuming dairy products and restrict their salt intake are more susceptible to iodine deficiency and subsequent thyroid disorders compared to women who include dairy products in their diet and do not limit salt intake. Both table salt and dairy products are rich sources of iodine, making them essential components for ensuring sufficient iodine intake during pregnancy.
# Supports Fetal and Infant Development
Iodine plays a critical role in fetal and infant development, and its deficiency in pregnant women can have major health consequences on the growing baby.
Chronic and severe iodine deficiency during pregnancy can lead to a condition known as cretinism, characterized by intellectual disability, deaf-mutism, motor spasticity, growth retardation, delayed sexual maturation, and various physical and neurological abnormalities in the child.
Even less severe iodine deficiency can result in lower-than-average intelligence in infants and children, as measured by IQ.(5)
The good news is that we can prevent these adverse outcomes simply by ensuring an adequate intake of iodine, as well as other essential trace minerals like copper, zinc, and selenium, during and after pregnancy.
In this regard, several national and international health organizations recommend women to consider a daily supplement containing 150 mcg of potassium iodide. This supplementation is essential both when planning for pregnancy and throughout the entire pregnancy and breastfeeding period. However, women with a history of thyroid disease should prioritize consulting a doctor before starting any supplement regimen.
# Promotes Skin Health and Wound Healing
Iodine is not only known for its antiseptic properties but also plays an important role in various aspects of skin health. It helps regulate skin moisturization by supporting the sweat gland proper function, contributing to balanced hydration levels and preventing dryness.
Additionally, iodine aids in the synthesis of collagen, a structural protein that promotes skin elasticity, reduces the appearance of fine lines, and improves wound healing, thus helping to minimize scars and accelerate tissue repair.
Moreover, iodine’s involvement in skin cell regeneration can contribute to a smoother skin complexion and may help with certain skin conditions.
However, it’s essential to use iodine-based treatments with caution and under professional guidance, as excessive iodine application can cause skin irritations.
# Supports the Immune System Function
Iodine plays a crucial role in supporting the immune system function. It serves as an essential component in facilitating communication between innate and adaptive immune cells, promoting a coordinated and effective immune response.
Additionally, iodine contributes to the development and maturation of B cells, which are responsible for producing antibodies. These antibodies are essential in recognizing and neutralizing harmful pathogens, helping the body fight infections.
Furthermore, iodine enhances phagocytosis, a critical process where immune cells engulf and destroy invading microorganisms. By promoting phagocytic activity, iodine assists in efficiently clearing pathogens from the body and promoting a robust defense against infections.
Iodine also influences the release of cytokines, which are essential inflammatory mediators that regulate immune responses. These signaling molecules help direct immune cells to the site of infection, enabling a targeted and precise immune reaction against invading pathogens.
By supporting these various aspects of immune function, iodine contributes to the overall resilience and effectiveness of the immune system in protecting the body from infections and maintaining optimal health.
# Assists in Detoxification Processes
Iodine plays a central role in supporting the body’s detoxification processes. In particular, it aids in the excretion of certain heavy metals, such as lead and mercury, both of which can have detrimental effects when accumulated in excess within the body.
Iodine has also been demonstrated to aid in the elimination of bromide, a substance commonly used in dough to increase elasticity and is also found in certain medications.
Excessive accumulation of bromide can lead to adverse effects, affecting neurological and endocrine functions. Bromide toxicity has been associated with headaches, fatigue, and cognitive impairment.
Furthermore, research has indicated that high levels of fluoride intake can affect the thyroid gland’s ability to absorb and utilize iodine, leading to iodine deficiency.
# Provides Antioxidant Properties
Emerging research suggests that iodine may possess antioxidant properties, helping to neutralize harmful free radicals in the body. These free radicals are unstable molecules that can cause oxidative stress and damage cells, potentially leading to various health issues. As an antioxidant, iodine may contribute to reducing oxidative stress and promoting cellular health.
Iodine Deficiency Symptoms
Iodine deficiency remains a significant public health concern in 25 countries, impacting a staggering population of approximately 683 million people worldwide.
The adverse effects of iodine deficiency on human growth and development are significant, making it the leading cause of preventable intellectual disability across the globe. Adequate iodine intake is crucial during critical periods of growth, such as pregnancy and early childhood, to ensure proper cognitive development and overall well-being.
When iodine deficiency occurs, the pituitary gland responds by producing more thyroid-stimulating hormone (TSH), which can be an indication of possible hypothyroidism or an underactive thyroid. These thyroid disorders can lead to various health problems, including neck swelling (Goiter), weight gain, weakness and fatigue, hair loss, and in severe cases, even intellectual disability.
# Neck Swelling (Goiter)
The thyroid’s effort to capture more iodine from the bloodstream leads to the enlargement of the gland, causing visible swelling in the neck.
# Weight Gain
As the thyroid gland plays a pivotal role in regulating metabolism, insufficient iodine intake can disrupt this balance. With lowered thyroid hormone levels, the body tends to burn fewer calories at rest, resulting in the accumulation of excess calories as stored fat and subsequent weight gain.
# Weakness and Fatigue
A shortage of thyroid hormones can impair energy production, manifesting as persistent fatigue and weakness. Individuals may find themselves struggling with a lack of vitality and stamina.(3)
# Hair Loss
Iodine deficiency can inhibit hair follicles from regenerating. A study of 700 adults found that 30% of those with insufficient thyroid levels experienced hair loss. Yet, Another study indicated that insufficient iodine intake only accelerates the process in people with a family history of hair loss.
# Intellectual Disability
Iodine deficiency can have severe consequences on brain development, leading to intellectual disability.
Inadequate iodine intake during pregnancy and infancy can result in irreversible cognitive impairments, affecting learning abilities and overall intellectual functioning.
Intellectual disability may manifest as difficulties in problem-solving, memory retention, and language development.
Ensuring sufficient iodine intake, especially during critical periods of growth and development, is crucial in preventing such long-term cognitive deficits. Early detection and intervention are essential to mitigate the impact of iodine deficiency on intellectual development and optimize overall brain health.
# Dry and Flaky Skin
Dry, flaky skin is a common symptom of iodine deficiency. Iodine plays a crucial role in the sweating process, which helps keep the body moisturized and hydrated. Additionally, it aids in the regeneration of skin cells. Therefore, a shortage of iodine might impede these mechanisms, leading to dry skin and other skin issues.
# Cold Feet and Hands
Cold feet and hands, known as ‘cold extremities,’ can be a symptom of iodine deficiency. Iodine is essential for maintaining proper circulation and blood flow throughout the body.
When iodine levels are insufficient, it may lead to reduced blood flow to the extremities, causing the hands and feet to feel unusually cold compared to the rest of the body.
Addressing iodine deficiency is vital to support adequate blood circulation and maintain warmth in the extremities, promoting overall circulatory health.
The good news is that most cases of hypothyroidism can be treated by increasing your iodine intake
Who is most at risk for Iodine Deficiency?
After the successful implementation of salt iodization programs in many countries with low natural iodine content in the soil, the prevalence of iodine deficiency has significantly decreased. However, despite these efforts, certain groups of people remain at risk for iodine deficiency, including:
# People who do not use iodized salt
Iodized salt plays an essential role as the main source of iodine for many populations. However, those who do not use iodized salt in their diets face an increased risk of inadequate iodine intake.
With iodized salt being a readily available and affordable option, its exclusion from the diet may lead to iodine deficiency. Ensuring the use of iodized salt in daily cooking and meal preparation can go a long way toward meeting iodine needs and promoting overall thyroid health and well-being.
# Individuals living in areas with deficient soil iodine content
Living in iodine-deficient regions, such as mountainous areas (e.g., the Himalayas, Alps, and Andes regions) and flood-prone river valleys (particularly in South and Southeast Asia), poses a significant risk of iodine deficiency.
To address this concern, residents in these regions should prioritize the consumption of iodized salt and actively seek out foods produced outside of iodine-deficient areas.
# Pregnant and nursing mothers
Pregnant and breastfeeding women require increased iodine intake to support their own health and the optimal development of their babies.
During pregnancy, iodine requirements rise from 150 to 220 mcg per day, and during lactation, the intake further increases to 290 mcg.
Adequate iodine is crucial for proper fetal brain development and to meet the needs of the growing infant. Iodine deficiency during these critical periods can have long-lasting consequences on cognitive and neurological health.
Ensuring pregnant and nursing mothers consume foods rich in iodine, such as iodized salt, seafood, and dairy products, is essential for maintaining adequate iodine levels and promoting the overall well-being of both mother and child.
# Vegetarians
Vegetarians may face challenges in obtaining sufficient iodine from their plant-based diets. These diets are generally lower in iodine, as iodine-rich foods like seafood and dairy products are not commonly included.
To ensure adequate iodine intake, vegetarians can incorporate iodine-rich plant-based foods such as seaweed, certain types of fruits, and vegetables into their meals.
Additionally, iodine supplements provide a convenient and reliable source of iodine to bridge the gap in iodine requirements and support overall health.
It’s essential to consult with a healthcare professional before adding iodine supplements to your diet to determine the appropriate dosage and ensure it aligns with individual health needs.
# People with restricted diets
Individuals following restrictive diets, such as strict low-salt diets or specific weight loss programs, may unintentionally reduce their iodine intake.
Iodized salt is a significant source of dietary iodine for many people, and those who avoid salt or use non-iodized salt may be at risk of inadequate iodine intake.
Ensuring the inclusion of iodine-rich foods, such as seafood, dairy products, and iodized salt in moderate amounts, is important for maintaining sufficient iodine levels in such diets.
# Infants and young children
Babies who are exclusively breastfed may be at risk of iodine deficiency if their mothers have a poor iodine intake.
While breast milk is the best source of nutrition for infants, its iodine content depends on the mother’s iodine status. If the mother’s iodine intake is inadequate, the breast milk may not provide enough iodine for the growing baby.
Introducing complementary foods that are rich in iodine, such as iodized salt, fortified cereals, and seafood, is essential for meeting the infant’s iodine needs as they transition to solid foods.
# The Elderly
As people age, their ability to absorb and retain nutrients, including iodine, may decline. Older adults may also have increased urinary iodine excretion, further impacting iodine status.
Inadequate iodine intake can affect thyroid function, metabolism, and overall health in older individuals.
Ensuring a balanced diet that includes iodine-rich foods like iodized salt, seafood, and dairy products is crucial to support the nutritional needs of older adults and reduce the risk of iodine deficiency.
# People with limited access to diverse foods
Geographic regions or socio-economic circumstances may limit access to a diverse range of iodine-rich foods. In areas where iodine-rich foods are scarce or expensive, people may rely on locally available foods that may not provide adequate iodine.
Promoting the availability and affordability of iodine-rich foods, as well as iodized salt, in these regions can help reduce the risk of iodine deficiency among these populations.
# Individuals with marginal iodine status who consume foods containing goitrogens
Individuals with marginal iodine status who consume foods containing goitrogens may be at an increased risk of exacerbating iodine deficiency.
Goitrogens are compounds found in certain foods, such as soybeans, cassava, and cruciferous vegetables (e.g., cabbage, broccoli, and cauliflower), that can interfere with iodine uptake in the thyroid gland.
This interference may potentially contribute to goiter development in individuals who already have low iodine levels or are at risk of iodine deficiency.
It’s important to note that goitrogens are generally not a concern for most people, including the majority of the US population with adequate iodine intakes and diverse diets.
# Individuals with certain medical conditions
Certain medical conditions can increase the risk of iodine deficiency by affecting iodine absorption, utilization, or excretion.
Gastrointestinal disorders such as celiac disease or inflammatory bowel disease may impair the body’s ability to absorb iodine from the diet, leading to reduced iodine levels.
Kidney disorders can also play a role, as they may result in increased iodine excretion through urine, further contributing to iodine depletion.
Additionally, individuals with specific metabolic disorders or hormone imbalances may experience alterations in thyroid function, potentially exacerbating iodine deficiency.
Where can we get Iodine from?
# From Daily Diet
Iodine intake has significantly improved in many countries due to salt iodization programs. Consequently, a substantial portion of our daily iodine intake comes from iodized table salt, providing approximately 45 mcg of iodine for every gram of salt consumed.
In addition to iodized salt, there are natural dietary sources of iodine from the soil and the ocean. Sea vegetables, including nori, dulse flakes, kombu, wakame, and dried arame, are among the richest sources of iodine. Notably, kelp stands out as the most iodine-rich seaweed, containing around 2000 mcg of iodine in a single tablespoon.
However, caution is advised against consuming excessive amounts of kelp, as it can lead to hyperthyroidism, posing risks similar to hypothyroidism.
Another iodine-rich seaweed, hijiki, should also be avoided due to its high levels of arsenic, a harmful heavy metal for human health.
Apart from seaweeds, dairy products like cow’s milk and eggs provide iodine. Plant-based milk substitutes, such as soy and almond drinks, contain smaller amounts of iodine.
While vegetables and fruits are generally not significant iodine sources, their iodine content can be influenced by soil iodine concentrations, fertilizer use, and irrigation practices.
For infants, both human breast milk and infant formulas contain iodine, ensuring proper iodine intake during early development.
It’s important to strike a balance in iodine consumption, considering both iodized salt and diverse iodine-rich foods, to support a healthy thyroid function and overall well-being.
# From Dietary Supplements
If obtaining sufficient iodine through your diet proves challenging, dietary supplements can be a valuable consideration.
Potassium iodide and sodium iodide are commonly used forms of iodine found in dietary supplements.
Additionally, kelp supplements, derived from iodine-rich seaweed, provide a concentrated iodine source. Typically, one tablet contains 150 mcg of iodine.
For added convenience, iodine is often included in multivitamins/minerals and prenatal supplements, especially as iodine requirements increase during pregnancy.