Iodine is an essential mineral found in seafood. Your thyroid gland uses it to make thyroid hormones, which help control growth, repair damaged cells and support a healthy metabolism. But because so many lack it in their diet, up to a third of people worldwide are at risk of an iodine deficiency.

People who have the highest risk of iodine deficiency include: pregnant women, people who live in countries where there is very little iodine in the soil (South Asia, Southeast Asia, New Zealand and Europe), those who don’t use iodized salt in their food, and people who follow a vegetarian or vegan diet.

In the US, iodine deficiencies are rare because there are sufficient levels of the mineral in the food supply.

Iodine deficiency can cause very severe symptoms that can be very uncomfortable and very similar to those of hypothyroidism, or low thyroid hormones. Some of the symptoms include swelling in the neck, pregnancy-related issues, weight gain, and learning difficulties. Since iodine is used to make thyroid hormones, when deficient it means your body can’t make enough of the needed hormones, leading to hypothyroidism.

Most Common Iodine Deficiency Signs and Symptoms

  • Swelling in the neck – Swelling in the front of the neck is the most common symptom of an iodine deficiency. This is called a goiter. It occurs when the thyroid gland grows too big. When blood levels of TSH rise, the thyroid gland uses iodine to make thyroid hormones. When your body is low in iodine, the thyroid can’t make enough of the hormone. Because the gland is trying to compensate for the missing mineral it works harder. This causes the cells to grow and multiply, eventually leading to a goiter. Fortunately, most cases can be treated by increasing your iodine intake. But, if a goiter hasn’t been treated for a long time, it can cause permanent thyroid damage.
  • Fatigue and weakness – Both fatigue and weakness are common symptoms of an iodine deficiency. Numerous studies have found that nearly 80% of people with low thyroid hormone levels, which occur in cases of iodine deficiency, feel tired, sluggish and weak. When thyroid hormone levels are low, the body can’t make as much energy as it usually does. This may cause your energy levels to decline and leave you feeling weak.
  • Weight gain – Unexpected weight gain is another sign of an iodine deficiency. This is because thyroid hormones help control the speed of your metabolism, which is the process by which your body converts food into energy and heat. When your thyroid hormone levels are low, your body burns fewer calories at rest meaning more calories from the foods you eat are stored as fat.
  • Changes in heart rate – Your heart rate is a measure of how many times your heart beats per minute. When your body has too little of the iodine mineral it could cause your heart to beat slower than usual. Of course, the opposite occurs if you have too much of the said mineral which then could cause your heart to beat faster than usual.
  • Feeling cold – Another very common symptom of iodine deficiency is feeling colder than usual. Because of slow thyroid function, your metabolism slows down. A slower metabolism generates less heat, which may cause you to feel colder than usual. Also, thyroid hormones help boost the activity of your brown fat, a type of fat that specializes in generating heat. This means that low thyroid hormone levels, which may be caused by an iodine deficiency, could prevent brown fat from doing its job.
  • Hair loss – People with iodine deficiency suffer from hair loss. This is because thyroid hormones help control the growth of hair follicles. When your thyroid hormone levels are low, your hair follicles may stop regenerating, which in time, may result in hair loss. While numerous studies have shown that people with low thyroid hormone levels experienced hair loss, another set of studies has proven that this affects only those individuals with a family history of hair loss.
  • Dry skin – Dry, flaky skin affects many people with an iodine deficiency. Same as for your hair follicles, thyroid hormones, which contain iodine, help your skin cells regenerate. When thyroid hormone levels are low, this regeneration doesn’t occur as often, leading to dry, flaky skin.
  • Hard time learning and remembering things – An iodine deficiency may affect your ability to learn and remember. Studies have found that the hippocampus, the part of the brain that controls long-term memory, appears to be smaller in people with low thyroid hormone levels. Another study confirmed that those with higher thyroid hormone levels performed better on learning and memory tests, compared to those with lower thyroid hormone levels.
  • Heavy and irregular periods – Like most symptoms of iodine deficiency, this is also related to low levels of thyroid hormones. Women with low thyroid hormone levels experienced irregular menstrual cycles more often than those with healthy thyroid. Research also shows that women with low thyroid hormone levels experience more frequent menstrual cycles with heavy bleeding. This is because low thyroid hormone levels disrupt the signals of hormones that are involved in the menstrual cycle.
  • Problems doing pregnancy – Pregnant women are at a high risk of iodine deficiency. This is because they need to consume enough to meet their own daily needs, as well as the needs of their growing baby. The increased demand for iodine continues throughout lactation, as babies receive iodine through breast milk. Not consuming enough iodine throughout pregnancy and lactation may cause side effects for both the mother and baby. Mothers may experience symptoms of an underactive thyroid, such as a goiter, weakness, fatigue and feeling cold. Meanwhile, an iodine deficiency in infants may stunt physical growth and brain development.

Best Food Sources of Iodine

The recommended daily intake (RDI) is 150 mcg per day. This amount should meet the needs of 97/98% of all healthy adults. However, pregnant or breastfeeding women need more. Pregnant women need 220 mcg daily, while lactating women need 290 mcg daily.

Foods that are excellent sources of iodine:

  • Seaweed, one whole sheet dried – 11–1,989% of the RDI
  • Cod, 3 ounces (85 grams) – 66% of the RDI
  • Yogurt, plain, 1 cup – 50% of the RDI
  • Iodized salt, 1/4 teaspoon (1.5 grams) – 47% of the RDI
  • Shrimp, 3 ounces (85 grams) – 23% of the RDI
  • Egg, 1 large – 16% of the RDI
  • Tuna, canned, 3 ounces (85 grams) – 11% of the RDI
  • Dried prunes, 5 prunes – 9% of the RDI


Your body uses iodine to make thyroid hormones. That’s why an iodine deficiency can cause hypothyroidism, a condition in which the body can’t make enough thyroid hormones. Luckily, deficiency is easy to prevent through proper diet.

Please note if you suspect you have an iodine deficiency, it’s best to talk to your doctor.