What are the Possible Risks Of Excessive Iodine Consumption

While iodine is essential, it is possible to consume too much. This condition is known as iodine excess. It is very difficult to reach toxic levels from iodised salt and food alone; excessive intake almost always results from taking high-dose iodine supplements or consuming large quantities of iodine-rich foods like seaweed (especially kelp) regularly.

Most people are quite tolerant of high iodine intakes, but chronic overconsumption can lead to thyroid problems similar to those caused by deficiency:

• Goiter and Hypothyroidism: Paradoxically, very large doses of iodine can actually inhibit the synthesis and release of thyroid hormones, a phenomenon known as the Wolff-Chaikoff effect. This can lead to an underactive thyroid (hypothyroidism) and the formation of a goiter.
• Hyperthyroidism: In some individuals, particularly those who were previously deficient, a sudden, large intake of iodine can trigger the thyroid to become overactive, producing too much hormone. This is called iodine-induced hyperthyroidism.
• Thyroiditis: Excessive iodine can cause inflammation of the thyroid gland.
• Other Symptoms: Acute iodine poisoning (from massive, single doses) is rare but can cause symptoms like a burning sensation in the mouth and throat, fever, nausea, vomiting, and diarrhea.

To prevent these issues, health authorities have set a Tolerable Upper Intake Level (UL) for iodine. For adults 19 years and older, the UL is 1,100 micrograms (µg) per day. This is the maximum daily intake unlikely to cause adverse health effects in the general population.