Iodine is required for the making of thyroid hormone, an important regulator of metabolism, growth and reproduction in your body. Iodine supplements are used to manage thyroid diseases such as hypothyroidism and radioactivity-induced thyroid cancer. Iodine is also helpful in relieving the pain from fibrocystic breast disease, a benign condition with painful and lumpy breast. However, when it comes to iodine, more is not better. Just like iodine deficiency, chronic iodine excess can lead to thyroid diseases. Too much iodine at one time can be deadly.
Acute Iodine Poisoning
Although rare, a dose greater than 1.1 mg of iodine, which is the upper tolerable level set by the Institute of Medicine for adults, can cause acute poisoning, producing symptoms ranging from diarrhea, nausea, and vomiting, to burning of the upper gastrointestinal tract, weak pulse and coma. The National Institutes of Health states that giving milk, cornstarch or flour mixed with water every 15 minutes may help if the person is still able to swallow. But in all cases of iodine poisoning, you should seek help immediately from poison control or health care professionals.
Health Risks of Long-term Excessive Iodine Intake
Long-term excess iodine intake can inhibit the production of thyroid hormone and causes hypothyroidism, or low thyroid function, and goiter, mimicking iodine deficiency. On the other hand, excess iodine may also lead to hyperthyroidism or high thyroid function. This often results from the iodine supplements used to correct thyroid deficiency. Inflammation of the thyroid gland and thyroid cancers are also major concerns with too much iodine intake. The recommended intake of iodine for adults is 150 micrograms a day. You should not take more than 1.1 mg of iodine a day without medical supervision.
Susceptible Population
Not everyone is equally susceptible to the toxicity of excess iodine. For certain populations, especially those with autoimmune thyroid disease, thyroid tumor, and iodine deficiency diseases such as goiter and hypothyroidism, even doses that are considered safe for the general population can produce adverse effect. These diseases cause the thyroid to actively trap iodine from the circulation and thus amplify the effects of iodine overdose.
Interaction with Medications
Iodine supplements can interact with a number of medications. For example, iodine may potentiate the effect of anti-thyroid drugs used to decrease the thyroid gland, according to the National Institutes of Health. As a result, the thyroid may decrease too much. Because iodine supplementation is often provided in the form of potassium iodide, it may interfere with potassium-sparing drugs such an ACE inhibitors and angiotensin-receptor blockers, two classes of hypertensive drugs, and potassium-sparing diuretics. Using potassium iodide together with these medications may cause the body to accumulate too much potassium, a condition that can lead to heart failure.
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