Iodine Food: Essential Sources, Benefits, and Deficiency Awareness

Iodine is a vital trace mineral that our bodies can’t produce on their own, making it crucial to obtain it through the food we eat or supplements. Naturally present in various foods and added to iodized salt and some supplements, iodine plays a pivotal role in producing thyroid hormones, thyroxine and triiodothyronine. These hormones are critical for protein creation, enzyme activity, and the regulation of a normal metabolism. Insufficient iodine intake can impair thyroid hormone production, potentially leading to hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), both associated with diverse adverse health effects.

Recommended Daily Intake of Iodine Food

Understanding the recommended daily amounts of iodine is key to maintaining optimal health.

Recommended Dietary Allowance (RDA): For adults aged 19 years and older, the RDA for iodine is 150 micrograms (mcg) daily. This requirement increases for women who are pregnant or breastfeeding, with recommended intakes of 220 mcg and 290 mcg per day, respectively [1, 2].

Tolerable Upper Intake Level (UL): While iodine is essential, excessive intake can also be harmful. The Tolerable Upper Intake Level (UL) for iodine is set at 1,100 mcg daily for adults aged 19 years and older, including pregnant and lactating women. This UL represents the maximum daily dose considered unlikely to cause adverse health effects in the general population.

foods containing iodine, including a variety of fish, shellfish, iodized salt, milk, seaweed, nuts, seeds, potatoes, beans, eggs and a variety of dairy products including milk, cheese and yogurt.

Various iodine rich foods, including seafood, dairy, eggs, and iodized salt, are displayed to illustrate diverse dietary sources of iodine.

The Health Benefits of Iodine Food

Iodine’s impact on health is broad, particularly concerning thyroid function and developmental stages of life.

Iodine Food for Infant and Childhood Health

The demand for thyroid hormones rises during pregnancy, necessitating increased iodine consumption. Adequate iodine intake is essential for both fetal and infant physical growth and brain development. Breast milk contains iodine, and many infant formulas are fortified with it, though the amount in breast milk is dependent on the mother’s iodine intake. Importantly, not all prenatal multivitamins contain iodine. The American Academy of Pediatrics advocates for supplemental iodine for pregnant and breastfeeding women, often through iodized salt [2]. It’s important to note that high-dose iodine supplements should be approached cautiously as they can sometimes induce thyroid issues in some women.

Iodine deficiency, especially if moderate to severe in children, can lead to impaired cognitive function, resulting in a lower IQ, and stunted physical growth. Supplementation with iodine in deficient children has shown to improve both physical and mental development.

Iodine Food and Thyroid Disorders: Hypothyroidism and Hyperthyroidism

Iodine is intrinsically linked to the function of the thyroid gland. Hypothyroidism arises when the body doesn’t produce enough thyroid hormone, while hyperthyroidism occurs when there’s an overproduction. An elevated level of thyroid-stimulating hormone (TSH) in blood tests can be an early indicator of hypothyroidism, often linked to insufficient iodine intake. Ironically, it can also occur in individuals with a history of iodine deficiency who suddenly consume high doses of iodine, such as from supplements [1]. Goiter, characterized by a visible swelling in the front of the neck, can be a consequence of both hypo- and hyperthyroidism, as well as excessive iodine intake. Notably, goitrogens, found in cruciferous vegetables, can interfere with iodine absorption, potentially disrupting thyroid function and contributing to goiter, especially in those with pre-existing iodine deficiency or hypothyroidism.

Top Iodine Food Sources

Iodine content in food is influenced by the iodine levels in soil and ocean environments. Foods richest in iodine are primarily animal protein sources and sea vegetables, with lesser amounts found in fortified foods like bread, cereals, and milk. To ensure adequate iodine intake, consider incorporating these iodine-rich foods into your diet:

Seaweed: Varieties like nori, kelp, kombu, and wakame are excellent natural sources of Iodine Food.
Fish and Shellfish: Aquatic foods such as cod, canned tuna, oysters, and shrimp are good sources of dietary iodine.
Iodized Salt: Table salt labeled “iodized” is a readily available and effective way to increase iodine intake.
Dairy Products: Milk, cheese, and yogurt contribute to iodine intake.
Eggs: A versatile and accessible source of iodine food.
Beef Liver and Chicken: Meats like beef liver and chicken also contain iodine.
Fortified Infant Formula: Formulated to meet the nutritional needs of infants, including iodine.

A variety of seaweeds, such as nori, kelp, and wakame, are presented as key iodine food sources from the ocean.

Recognizing Iodine Deficiency and Toxicity

Maintaining a balanced iodine intake is crucial, as both deficiency and excess can lead to health issues.

Iodine Deficiency Symptoms

Iodine is essential for metabolism regulation, the process of converting food into energy. Iodine deficiency can disrupt normal growth and development, posing significant risks, especially during pregnancy and infancy, including miscarriage, stillbirth, stunted growth, and cognitive impairments. In adults, a daily iodine intake below 10-20 mcg can result in hypothyroidism, disrupting metabolic functions like heart rate, body temperature, and weight regulation [2]. Goiter is a common sign of hypothyroidism. Other symptoms of iodine deficiency include:

Persistent Fatigue and Lethargy
Muscle Weakness
Increased Sensitivity to Cold Temperatures
Constipation Issues
Dry Skin and Hair
Unexplained Weight Gain

Individuals at higher risk of iodine deficiency include those who avoid iodized salt or iodine-containing supplements, pregnant women, vegans who exclude all animal products, and people living in regions with iodine-poor soil.

Iodine Toxicity Symptoms

While high iodine intakes are generally well-tolerated by healthy individuals, excessive consumption can lead to toxicity, particularly in those with pre-existing thyroid conditions. Populations with high seaweed consumption, like in Japan and Korea, generally tolerate high iodine intake [3]. However, individuals with autoimmune thyroid disease or a history of iodine deficiency can be more susceptible to adverse effects from extra iodine, potentially triggering hypothyroidism and goiter [2, 4]. Iodine excess can also induce hyperthyroidism, characterized by:

Unintended Weight Loss due to Increased Metabolism
Rapid or Irregular Heartbeat
Hand Tremors
Irritability and Anxiety
Fatigue
Excessive Sweating

In sensitive individuals, even a slight dietary iodine increase above the RDA can induce hyperthyroidism [4]. Some studies suggest a link between high seaweed intake and increased risk of certain thyroid cancers, particularly in postmenopausal women, though the mechanisms are still under investigation [2, 3]. Severe iodine poisoning is rare but can manifest with symptoms like fever, abdominal pain, nausea, vomiting, and a burning sensation in the mouth, throat, and stomach, potentially leading to coma [2]. Vulnerable groups, including children, infants, the elderly, and those with thyroid disease, are more susceptible to iodine toxicity and iodine-induced thyroid disorders [3, 4].

Interesting Facts About Iodine Food

In the U.S., the primary sources of dietary iodine are iodized salt and milk.
Iodine supplements can interact negatively with certain blood pressure medications and diuretics, such as lisinopril, spironolactone, and amiloride, potentially causing hyperkalemia, a dangerous buildup of potassium in the blood.
Iodine is a key component in contrast agents used in medical imaging like X-rays and CT scans, enhancing image clarity.