Iodine is an essential mineral. Your thyroid gland uses it to make thyroid hormones, which help control growth, repair damaged cells and support a healthy metabolism. Unfortunately, up to a third of people worldwide are at risk of an iodine deficiency. Those at the highest risk include:
- Pregnant women.
- People who live in countries where there is very little iodine in the soil: South Asia, Southeast Asia, New Zealand and European countries.
- People who don’t use iodized salt.
- People who follow a vegetarian or vegan diet.
Iodine deficiencies had been rare in the United States, where there are sufficient levels of iodine in the food supply. However, changes in lifestyle have increased the prevalence across the United States in recent years. Symptoms can include swelling in the neck, pregnancy-related issues, weight gain and learning difficulties. Its symptoms are very similar to those of suboptimal thyroid function. Since iodine is used to make thyroid hormones, an iodine deficiency means your body cannot make enough of them, leading to hypothyroidism.
Signs that you may have an iodine deficiency:
Swelling in the Neck
Swelling in the neck is the most common symptom of an iodine deficiency. This is called a goiter and occurs when the thyroid gland grows too big. The thyroid gland is a small, butterfly-shaped gland in the front of your neck. The thyroid gland uses iodine to make thyroid hormones. However, when your body is low in iodine, it cannot make enough of them. To compensate, the thyroid gland works harder to try to make more. This causes the cells to grow and multiply, leading to a goiter. Most cases can be treated by increasing iodine intake. However, if a goiter has not been treated for many years, it might cause permanent thyroid damage.
Unexpected Weight Gain
Unexpected weight gain may occur if the body does not have enough iodine to make thyroid hormones. 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. Unfortunately, this means more calories from the foods you eat are stored as fat. Adding more iodine to your diet may help reverse the effects of a slow metabolism, as it can help your body make more thyroid hormones.
Fatigue and Weakness
Fatigue and weakness are also common symptoms of an iodine deficiency. 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. These symptoms occur because thyroid hormones help the body make energy. When thyroid hormone levels are low, the body cannot make as much energy as it usually does. This may cause your energy levels to plummet and leave you feeling weak.
Thyroid hormones help control the growth of hair follicles. When thyroid hormone levels are low, your hair follicles may stop regenerating. Over time, this may result in hair loss. For this reason, people with an iodine deficiency may also suffer from hair loss. Approximately 30% of those with low thyroid hormone levels experienced hair loss. If you experience hair loss because of an iodine deficiency, getting enough of this mineral may help correct your thyroid hormone levels and stop hair loss.
Dry, Flaky Skin
Dry, flaky skin may affect many people with an iodine deficiency. Studies show that up to 77% of people with low thyroid hormone levels may experience dry, flaky skin. Thyroid hormones, which contain iodine, help your skin cells regenerate. When thyroid hormone levels are low, this regeneration does not occur as often, possibly leading to dry, flaky skin. Additionally, thyroid hormones help the body regulate sweat. People with lower thyroid hormone levels, such as those with an iodine deficiency, tend to sweat less than people with normal thyroid hormone levels. Given that sweat helps keep your skin moist and hydrated, a lack of sweat may be another reason why dry, flaky skin is a common symptom of iodine deficiency.
Feeling Colder Than Usual
Feeling cold is a common symptom of an iodine deficiency. Over 80% of people with low thyroid hormone levels may feel more sensitive to cold temperatures than usual. Since iodine is used to make thyroid hormones, an iodine deficiency can cause your thyroid hormone levels to plummet. Because thyroid hormones help control the speed of your metabolism, low thyroid hormone levels may cause it to slow down. A slower metabolism generates less heat, which may cause you to feel colder than usual. Also, thyroid hormones help boost the activity of 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.
Changes in Heart Rate
Your heart rate is a measure of how many times your heart beats per minute. It may be affected by your iodine levels. Too little of this mineral could cause your heart to beat slower than usual, while too much of it could cause your heart to beat faster than usual. A severe iodine deficiency may cause an abnormally slow heart rate making you feel weak, fatigued, dizzy and possibly cause you to faint.
Trouble Learning and Remembering
An iodine deficiency may affect your ability to learn and remember. Thyroid hormones help your brain grow and develop. An iodine deficiency, which is required to make thyroid hormones, can reduce brain development. 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.
Problems During Pregnancy
Pregnant women are at a high risk of iodine deficiency – 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 under-active thyroid, such as a goiter, weakness, fatigue and feeling cold. Meanwhile, an iodine deficiency in infants may stunt physical growth and brain development. Furthermore, a severe iodine deficiency may increase the risk of stillbirth.
Heavy or Irregular Periods
Heavy and irregular menstrual bleeding may occur as a result of an iodine deficiency. Like most symptoms of iodine deficiency, this is also related to low levels of thyroid hormones. In one study, 68% of women with low thyroid hormone levels experienced irregular menstrual cycles, compared to only 12% of healthy women. 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.
Role of Iodine in Breast Health
Iodine deficiency is rapidly emerging as a major risk factor for breast cancer. Human breast tissue and breast milk contain higher concentrations of iodine than the thyroid gland itself, which contains just 30% of the body’s iodine stores. Breast tissue is rich in the same iodine-transporting proteins used by the thyroid gland to take up iodine from the blood. Iodine plays an important role in the health of women’s breast tissue. Iodine has been shown to exert a powerful antioxidant effect equivalent to vitamin C. Iodine-deficient breast tissue exhibits chemical markers of elevated lipid peroxidation, one of the earliest factors in cancer development. Iodine-deficient breast tissue also shows alterations in DNA and increases in estrogen receptor proteins. Coupled with iodine deficiency-induced increases in circulating estrogen levels, these changes can substantially increase the risk of breast cancer in women with low iodine levels.
Iodine also helps regulate levels of the stress hormone cortisol and contributes to normal immune function. Abnormal cortisol levels and deficient immune function are significant contributors to the risks of breast cancer; women with fibrocystic breast disease may also suffer from elevated cortisol levels. Taken together, these biological factors explain the well-known link between iodine deficiency and thyroid disease, thyroid cancer, and breast cancer, all of which predominate in postmenopausal women. The link between iodine consumption and breast cancer is most evident when you compare the Japanese and Western diets against cancer incidence. Japanese women consume a diet high in iodine-rich seaweed, which provides them with an iodine intake 25 times higher than the average American woman’s. Japanese women also have breast cancer rates roughly one-third of those found in American women, a difference that disappears in Japanese women who immigrate to the US, where they consume considerably less seaweed.
Studies of iodine therapy for breast cancer prevention are encouraging. Breast cancer cells avidly absorb iodine, which in turn suppresses tumor growth and causes cancer cell death. Added dietary iodine reduces the size of both benign and malignant breast tumors. Further benefits may be obtained by supplementing with selenium in addition to iodine; selenium is an essential cofactor in the enzymes used in thyroid and breast tissue to make optimal use of dietary iodine. In addition to its obvious role in preventing breast cancer, increased iodine intake may be important in mitigating another common, if less lethal, breast disorder—fibrocystic breast disease. Fibrocystic breast disease is extremely common – found in at least 9% of all women who undergo biopsies, though the actual rate is probably much higher. Fibrocystic breast changes can be reversed and women with fibrocystic breast disease can obtain substantial relief.
It is becoming increasingly clear that iodine deficiency interferes with optimum breast health, and intake of levels far higher than the recommended dietary allowance of 150-290 mcg is required to achieve benefits. Daily amounts of 3,000-6,000 mcg may help relieve the symptoms of fibrocystic breast disease.
The Role of Iodine in Cardiovascular Health
Iodine and iodine-rich foods enjoy a long history as natural therapies for hypertension and cardiovascular disease. Even when no overt symptoms are evident, hypothyroidism can contribute to heart disease and stroke, and it increases the risk of death from these conditions. Thyroid dysfunction creates unfavorable disturbances in lipid profiles, elevating low-density lipoprotein (LDL) and total cholesterol levels and raising the risk of atherosclerosis. Hypothyroidism also weakens the heart muscle, causing it to ‘squeeze’ less firmly with each contraction; it can cause cardiac arrhythmias as well. These effects may not be evident at rest, but become important during moderate exercise. Low thyroid function is also associated with higher waist-to-hip ratios, an obesity-related risk factor for cardiovascular disease. Restoring normal thyroid function helps reverse multiple cardiovascular risk factors, most notably adverse lipid profiles. Iodine therapy shows promise in safely and effectively modulating these health concerns.
Sources of Iodine
As with many diseases, it is better to prevent the problem rather than have to treat it. Over the last 80 years, worldwide efforts have been made to eliminate iodine deficiency. Elimination of iodine deficiency has been a major goal of the World Health Organization. Iodized salt has been the mainstay of treatment for iodine deficiency worldwide, including in the United States. Injections of iodized oil are occasionally used in regions of the world where widespread iodized salt use is not possible. Iodination of water supplies also has been effective in some places.
There are very few good sources of iodine in the diet. This is one reason why iodine deficiency is common worldwide. The recommended daily intake (RDI) is 150 mcg per day. This amount should meet the needs of 97–98% of all healthy adults. One teaspoon of iodized salt contains approximately 400 μg iodine. Most iodine-containing multivitamins have at least 150 μg iodine, but only about half of the types of multivitamins in the United States contain iodine. Pregnant or breastfeeding women need more iron. Pregnant women need 220 mcg daily, while lactating women need 290 mcg daily. Because the effects of iodine deficiency are most severe in pregnant women and their babies, the American Thyroid Association has recommended that all pregnant and breastfeeding women in the United States and Canada take a prenatal multivitamin containing 150 μg iodine per day.
The foods below 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
Seaweed is usually a great source of iodine, but this depends on where it came from. Seaweed from some countries, such as Japan, are rich in iodine. Smaller amounts of iodine are also found in a variety of foods like fish, shellfish, beef, chicken, lima and pinto beans, milk and other dairy products. The best way to get enough iodine is to add iodized salt to your meals. Half a teaspoon (3 grams) over the course of the day is enough to avoid a deficiency.
If you think you have an iodine deficiency, it’s best to consult your doctor. They will check for signs of swelling (a goiter) or take a urine sample to check your iodine levels.
Too Much Iodine
Taking too much iodine can also cause problems. This is especially true in individuals that already have thyroid problems, such as nodules, hyperthyroidism and autoimmune thyroid disease. Administration of large amounts of iodine through medications (i.e.: Amiodarone), radiology procedures (iodinated intravenous dye) and dietary excess (Dulce, kelp) can cause or worsen hyperthyroidism and hypothyroidism. In addition, individuals who move from an iodine-deficient region (for example, parts of Europe) to a region with adequate iodine intake (for example, the United States) may also develop thyroid problems since their thyroids have become very good at taking up and using small amounts of iodine. In particular, these patients may develop iodine-induced hyperthyroidism.
Talk to your heal care provider before starting an iodine regimen.