Some individuals are sensitive to high levels of iodine. These people are sensitive to both high levels of iodine in food and iodine used in x-ray procedures and iodine-based antiseptics. Iodine sensitive people only react to very high doses of iodine that far exceed the amount of iodine that people would receive from their normal diet, even with mandatory fortification.
The addition of iodine to bread (mandatory iodine fortification) is unlikely to cause harm even in the majority of iodine sensitive individuals. Iodine sensitive individuals may be advised to avoid foods high in iodine such as kelp, seaweed and seafood which may contain hundreds of micrograms or several milligrams of iodine. In contrast, mandatory iodine fortification increases iodine intake on average by approximately 54 micrograms per day (a microgram is a millionth of a gram). This is similar to the amount of iodine in a large glass of milk.
What if I have a thyroid condition?
The expected increase in iodine intake as a result of mandatory iodine fortification is unlikely to cause harm to people with a thyroid condition. If you have a thyroid condition you are likely to be under medical care and, in the unlikely event that a change in your thyroid function did occur; this would be identified and treated as part of your regular medical check-ups.
People with hyperthyroidism (an overproduction of thyroid hormone), including Graves' disease, may be more sensitive to increases in iodine intake. As a result, they may be advised to avoid medications, supplements and foods high in iodine, some cough medicine, iodine containing contrast media, kelp supplements, seafood and kelp/seaweed.
People with thyroid disorders should follow their doctor's advice on iodine intake.
What should I do if I think I'm sensitive to iodine?
If you think you might be sensitive to iodine talk to your doctor and ensure you have this checked through an appropriate clinical assessment. Remember, foods are a complex mixture of ingredients. While you may suspect iodine, it may be some other ingredient causing the problem, in which case you could be unnecessarily avoiding iodine-containing foods. A proper assessment should help to confirm this one way or the other.
If a suspected sensitivity to iodine is confirmed, the next step is to obtain appropriate dietary (through a dietitian or doctor) advice on how to avoid consuming large amounts of iodine-rich foods and substances.