Iodine is a vital trace mineral that the body cannot produce on its own. Therefore, it must be obtained through dietary sources or supplements. It plays a crucial role in the production of thyroid hormones, thyroxine and triiodothyronine, which are essential for protein synthesis, enzyme activity, and regulating metabolism. Insufficient iodine can lead to thyroid hormone dysfunction, potentially causing hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), both with various adverse health effects. Understanding What Food Contains Iodine is therefore important for maintaining optimal health.
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.
Recommended Daily Intake of Iodine
The Recommended Dietary Allowance (RDA) for iodine is 150 micrograms (mcg) per day for adult men and women (19+ years). Pregnant women need 220 mcg daily, and lactating women require 290 mcg daily to support the health of both mother and child. The Tolerable Upper Intake Level (UL) for iodine, which is the maximum daily dose unlikely to cause adverse effects, is 1,100 mcg for adults (19+ years) and pregnant/lactating women. It is important to adhere to these guidelines to ensure adequate iodine intake without risking toxicity.
The Importance of Iodine for Health
Infant and Childhood Development
Adequate iodine intake is particularly critical during pregnancy, as the production of thyroid hormones increases to support the developing fetus. Iodine is essential for the fetus’s physical growth and brain development. Breast milk contains iodine, and many infant formulas are fortified with it. The American Academy of Pediatrics recommends that prenatal and lactating women take supplemental iodine or use iodized salt to ensure sufficient intake. Moderate to severe iodine deficiency in children can result in lower IQ and stunted growth, and supplementation can improve both physical and mental development.
Hypothyroidism and Hyperthyroidism
Iodine plays a direct role in both hypothyroidism and hyperthyroidism, conditions where the body produces too little or too much thyroid hormone, respectively. Low iodine intake is a known risk factor for hypothyroidism, which may be indicated by elevated levels of thyroid-stimulating hormone (TSH) in the blood. Goiter, an enlargement of the thyroid gland, can also result from hypothyroidism, hyperthyroidism, or excessive iodine intake.
Key Food Sources of Iodine
Iodine content in food varies depending on the iodine levels in the soil and ocean where the food is grown or sourced. Generally, animal protein foods and sea vegetables are the richest sources of iodine. Here are some specific examples of what food contains iodine:
- Seaweed: Varieties like nori, kelp, kombu, and wakame are excellent sources of iodine.
Various edible seaweed types are rich in iodine.
- Fish and Shellfish: Cod, canned tuna, oysters, and shrimp are good sources of iodine.
- Iodized Salt: Table salt labeled “iodized” is a readily available source of iodine.
- Dairy Products: Milk, cheese, and yogurt contribute to iodine intake.
- Eggs: Another good source of iodine, especially the yolk.
- Beef Liver and Chicken: These meats contain moderate amounts of iodine.
- Fortified Infant Formula: Many infant formulas are fortified with iodine to meet the nutritional needs of infants.
Signs of Iodine Deficiency and Toxicity
Deficiency Symptoms
Iodine deficiency can disrupt normal growth and development, especially in pregnant women and infants, leading to potential complications such as miscarriage, stillbirth, stunted growth, and cognitive impairments. In adults, iodine deficiency can lead to hypothyroidism, disrupting metabolic functions like heart rate regulation, body temperature, and weight management. Common symptoms of hypothyroidism include:
- Fatigue and lethargy
- Weakness
- Sensitivity to cold
- Constipation
- Dry skin and hair
- Weight gain
- Goiter (swelling in the neck)
Individuals at risk for iodine deficiency include those who do not use iodized salt or iodine-containing supplements, pregnant women, vegans who avoid animal foods, and people living in areas with low iodine levels in the soil.
Toxicity Symptoms
While high iodine intakes are generally well-tolerated, some individuals, particularly those with autoimmune thyroid disease or a history of chronic iodine deficiency, may be sensitive to extra iodine. Excess iodine can induce hypothyroidism and goiter in susceptible individuals. Symptoms of hyperthyroidism, which can also result from excess iodine, include:
- Increased metabolism and weight loss
- Fast or irregular heartbeat
- Hand tremors
- Irritability
- Fatigue
- Sweatiness
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. Children, infants, the elderly, and those with existing thyroid disease are more vulnerable to iodine toxicity and iodine-induced thyroid conditions.
Important Considerations
- In the U.S., iodized salt and milk are primary sources of dietary iodine.
- Iodine supplements can interact with certain blood pressure medications and diuretics, potentially causing hyperkalemia (high potassium levels).
- Iodine is used in contrast agents for X-rays and CT scans to enhance image clarity.
By understanding what food contains iodine and maintaining a balanced diet, individuals can ensure adequate iodine intake for optimal thyroid function and overall health. Remember to consult with a healthcare professional or registered dietitian for personalized dietary advice.
