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Why iodine is added to salt, and what’s missing

Prior to 1920, the northern US had a region known as the “goiter belt” due to iodine deficiency that ran along the Great Lakes, Appalachians and Northwest. Up to 70% of children in this region at that time had a visible goiter. Because of this, in 1924 the US started to implement a non-mandatory salt iodine fortification program which still continues to this day.

Some, but not all countries in the world eventually adopted a similar program. It wasn’t until the year 2000 that the country of Denmark instituted their own iodine fortification program to help lower the risk of thyroid irregularities in pregnant women.

About fifteen years later, the Danish government conducted a study to assess whether the fortification program was succeeding, by testing pregnant Danish women for thyroid function and thyroid antibodies (associated with autoimmune conditions such as Hashimoto’s Disease). They found thyroid dysfunction levels continued to be high, with rates at about 10 – 15% of the women tested. (They also looked for and did not find an association between thyroid function and preterm delivery.)

Overall, there appeared to be an increase in thyroid abnormalities after instituting the Danish iodine fortification program. But how is this possible, when we know iodine is essential for producing thyroid hormone?

One contributing factor could be supplementing only with iodine without supplying missing co-factors, especially selenium. Selenium helps to stabilize thyroid function by supporting an enzyme (iodothyronine deiodinase) which is critical for the conversion of inactive thyroid hormone T4 to active T3. In fact, one study showed that selenium deficiency inhibited T3 production almost as much as anti-thyroid medicine! In fact, selenium is so important to the tiny thyroid gland that it stashes away the largest amounts as compared to all other organs in the body.

Selenium also helps produce glutathione peroxidase, an enzyme that reduces inflammation and antibody production. High thyroid antibody levels occur in an autoimmune disease called Hashimoto’s, in which antibodies attack the thyroid gland and cause hypothyroidism. It’s a common phenomenon for Hashimoto’s cases to increase in countries with iodine fortification programs due to missing selenium. Almost all Hashimoto’s patients have been found to be deficient in selenium, as shown in several studies. Supplementing with selenium has been shown to help reduce thyroid antibodies significantly.

Dr. Wilson has been talking about the importance of adding selenium to iodine supplementation for many years, as an essential way to maintain thyroid stability. You can increase selenium intake from foods, such as Brazil nuts, crimini or shitaki mushrooms, cod, shrimp, tuna, halibut, salmon, scallops, chicken, eggs, lamb and turkey and you can add selenium supplements to ensure adequate intake.

Another factor that could be contributing to the recent rise of thyroid problems even in people receiving iodine supplementation is the recent rise of thyroid problems such as Hashimoto’s in the population in general, possibly due to the increase in environmental toxins.

Reference:

Eur J Endocrinol. 2015 Dec;173(6):709-18.
Endocrinology. 1996 Jun;137(6):2580-5.

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