The fantasy of both conventional and alternative healthcare practitioners is finding a single nutrient to treat hypothyroidism. For doctors, this is thyroid hormone. For alternative practitioners, it is iodine.
In the previous article I showed why, when used alone, thyroid hormone replacement often fails. In this post I’ll explain why iodine may not only be ineffective, but also cause harm.
Iodine deficiency is the most common cause of hypothyroidism worldwide. Once researchers realized this, health authorities around the world began adding iodine to table salt.
This strategy was effective in correcting iodine deficiency. But it had an unanticipated – and undesired – effect. In countries where iodine has been added to table salt, the rates of autoimmune thyroid disease have risen. The following is just a sample of studies around the world demonstrating this effect:
- Sri Lanka
Why does this happen? Because increased iodine intake, especially in supplement form, increases the autoimmune attack on the thyroid.
Iodine increases the activity of an enzyme called thyroid peroxidase (TPO). In Hashimoto’s disease, TPO is the target of the immune system’s attack. Therefore, excess iodine will worsen the autoimmune response.
The extreme of this expression is called the Jod-Basedow Phenomenon. It occurs in people who are iodine deficient with elevated thyroid antibodies. When they are given supplemental iodine they develop hyperthyroid symptoms.
Only a minority of Hashimoto’s patients will develop overt hyperthyroid symptoms as a result of taking iodine. Most will have no symptoms, but tests will indicate elevated levels of TPO antibodies, suggesting an autoimmune flare-up.
On the other hand, restricting intake of iodine can reverse hypothyroidism. In one study, 78% of patients with Hashimoto’s regained normal thyroid function with iodine restriction alone.
All of this might seem confusing to people with hypothyroidism who’ve been told their condition is caused by iodine deficiency. In the U.S., however, the most common cause of hypothyroidism is not iodine deficiency, but Hashimoto’s.
The conclusion I draw from this evidence is patients with autoimmune thyroid disease (Hashimoto’s and Graves’) should not be taking iodine supplements. Since 9 in 10 people with hypothyroidism have Hashimoto’s, it’s safe to say this advice applies to the vast majority of hypothyroid patients.
I am less certain about whether iodine in food must be restricted. Foods rich in iodine, like seafood, are also rich in other essential nutrients – such as selenium and vitamin D. One dietary recommendation I can make with certainty is to use non-iodized sea salt instead of iodized salt.
The use of iodine in the treatment of thyroid disease is a controversial subject. I’m sure some readers will post comments directing me to the work of Dr. Abraham and Dr. Brownstein, both of whom have successfully treated hypothyroid patients with iodine.
I’ve read Dr. Brownstein’s book and some of Dr. Abraham’s writings, and I respect their clinical experience. But when weighed against what we know about thyroid biochemistry and physiology, and the evidence presented above linking excess iodine to autoimmune thyroid disease, I believe the argument for not using iodine with Hashimoto’s is stronger than the argument for using it.
Dr. Datis Kharrazian, author of Why Do I Still Have Thyroid Symptoms When My Lab Test Are Normal?, has written extensively about the dangers of giving iodine to patients with Hashimoto’s disease. See this recent post on his blog for a summary of research supporting his view. (If you have a thyroid condition, do yourself a favor and buy his book. It’s the best on this topic by far.)
Finally, it’s worth pointing out that for the 10% of people who have hypothyroidism caused by iodine deficiency, supplemental iodine is both necessary and effective. How do you know you’re in this group? You get your thyroid antibodies (TPO & TG) tested. If the results are positive, you have Hashimoto’s. If the results are negative, however, you need to be tested at least once more to rule out Hashimoto’s. Antibody levels fluctuate and it’s possible to get a “false negative” result if you only have a single test.
Also keep in mind that a minority of patients with Hashimoto’s confirmed by biopsy (the gold standard) never test positive for thyroid antibodies. This is probably because their immune systems are so depressed they can no longer produce antibodies. If you have a combination of hyper- and hypothyroid symptoms, I would still suspect Hashimoto’s even if your thyroid antibody tests are normal.