Iodine is an essential mineral that your body needs but cannot produce on its own. This means you must obtain it through your diet or supplements. Iodine plays a crucial role in the production of thyroid hormones, which are vital for regulating metabolism, enzyme activity, and protein synthesis. Understanding “What Foods Have Iodine In Them Naturally” is key to maintaining optimal thyroid health and overall well-being.
Recommended Amounts of Iodine
- RDA (Recommended Dietary Allowance): Adults (19+ years): 150 mcg daily. Pregnant women: 220 mcg daily. Lactating women: 290 mcg daily. [1, 2]
- UL (Tolerable Upper Intake Level): Adults (19+ years), including pregnant and lactating women: 1,100 mcg daily.
The Importance of Iodine for Health
Infant and Childhood Health
Iodine requirements increase significantly during pregnancy to support the production of thyroid hormones essential for both the mother and the developing fetus. Iodine is critical for the fetus’s physical growth and brain development. Breast milk contains iodine, the amount of which depends on the mother’s dietary iodine intake, and many infant formulas are fortified with iodine. The American Academy of Pediatrics suggests that pregnant and breastfeeding women consume supplemental iodine through iodized salt. [2] It’s important to consult with a healthcare provider before taking high-dose iodine supplements, as they can sometimes lead to thyroid issues.
Iodine deficiency in children can have serious consequences, including lower IQ and stunted growth. Supplementation has been shown to improve both physical and mental development in iodine-deficient children.
Hypothyroidism and Hyperthyroidism
These conditions arise when the thyroid gland produces too little (hypothyroidism) or too much (hyperthyroidism) thyroid hormone. Elevated levels of thyroid-stimulating hormone (TSH) in the blood can be an early indicator of hypothyroidism, potentially linked to inadequate iodine intake. Conversely, high doses of iodine in supplements can also trigger hypothyroidism, especially in individuals with a history of iodine deficiency. [1]
Goiter, characterized by a lump in the front of the neck due to an enlarged thyroid gland, can stem from hypothyroidism, hyperthyroidism, or excessive iodine intake (typically from prolonged consumption of very high doses exceeding 18,000 mcg daily). [1] Additionally, goitrogens present in certain cruciferous vegetables can hinder iodine absorption, potentially affecting thyroid function and causing goiter, particularly in individuals with iodine deficiency or hypothyroidism.
What Foods Have Iodine in Them Naturally?
The iodine content of food depends on the iodine levels in the soil and ocean where they are grown or sourced. Animal protein foods and sea vegetables are generally richer in iodine than other food groups. Fortified foods like bread, cereals, and milk can also contribute to your daily iodine intake. Here’s a breakdown of natural food sources of iodine:
- Seaweed: Seaweed is one of the best natural sources of iodine. Different types of seaweed contain varying amounts. Nori, kelp, kombu, and wakame are popular options.
Various types of seaweed, including nori, kelp, kombu, and wakame, highlighting their natural iodine content.
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Fish and Shellfish: Many types of seafood are good sources of iodine, including cod, tuna (canned), oysters, and shrimp. The iodine content will vary depending on where the fish was caught.
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Dairy Products: Milk, cheese, and yogurt contain iodine. The iodine content of dairy products can be influenced by the iodine supplementation of cattle feed and the use of iodine-containing sanitizers during milk processing.
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Eggs: Eggs contain iodine, with most of it found in the yolk.
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Beef Liver and Chicken: These meats contain smaller amounts of iodine.
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Iodized Salt: Although not naturally occurring, iodized salt is a readily available source of iodine. Check the label to ensure it is indeed iodized.
Signs of Iodine Deficiency and Toxicity
Deficiency
Iodine is critical for metabolism, the process of converting food into energy for cell function and growth. An iodine deficiency can disrupt normal growth and development, particularly in pregnant women and infants, leading to miscarriage, stillbirth, stunted growth, and cognitive impairments. In adults, iodine deficiency can cause hypothyroidism, disrupting metabolic functions like heart rate, body temperature, and weight regulation. [2] Goiter, a swelling in the neck, often accompanies hypothyroidism. Other symptoms include:
- Fatigue, lethargy
- Weakness
- Sensitivity to cold
- Constipation
- Dry skin and hair
- Weight gain
People at risk for iodine deficiency include those who don’t use iodized salt or supplements, pregnant women, vegans who avoid all animal products, and individuals living in areas with low iodine levels in the soil.
Toxicity
Most healthy individuals tolerate high iodine intakes without adverse effects. This is commonly seen in cultures with high seaweed consumption. [1, 3] However, individuals with autoimmune thyroid disease or a history of chronic iodine deficiency can be sensitive to extra iodine, potentially developing hypothyroidism and goiter. [2, 4] Excessive iodine can also cause hyperthyroidism, characterized by increased metabolism, weight loss, rapid heartbeat, tremors, irritability, fatigue, and excessive sweating. Even slight increases in dietary iodine above the RDA can trigger hyperthyroidism in sensitive individuals. [4]
Some studies suggest a link between high seaweed consumption and an increased risk of certain thyroid cancers, particularly in postmenopausal women, but the underlying mechanisms are not fully understood. [2, 3]
Excessive iodine intake can result from high-dose supplements or overconsumption of certain seaweeds and salts. Severe iodine poisoning is rare, but symptoms include fever, stomach pain, nausea, vomiting, a burning sensation in the mouth, throat, and stomach, and even coma. [2] Children, infants, the elderly, and those with pre-existing thyroid conditions are more susceptible to iodine toxicity and iodine-induced thyroid disorders. [3, 4]
Did You Know?
- In the U.S., the primary sources of dietary iodine are iodized salt and milk.
- Iodine supplements can interact with certain blood pressure medications and diuretics (e.g., lisinopril, spironolactone, amiloride), leading to hyperkalemia (a dangerous buildup of potassium in the blood).
- Iodine is used in contrast agents for X-rays or CT scans to enhance image clarity.
References
Last reviewed March 2023
