Many of us find it harder and harder to lose excess weight as we get older. When in my 30s, the weight would drop off me very quickly if I reduced my calorie intake. By age 45, that no longer worked. When I was doing practitioner work, my clients found the same problem.
Popular health books and magazines suggest the problem may be due to an underactive thyroid gland—an all too common problem which frequently goes undiagnosed. These publications almost always tell you “iodine is good for the thyroid, and you need to supplement it because it is no longer added to table salt”. Likewise, herbal products sold in health food stores for the thyroid are usually based on iodine-rich seaweed.
These books, articles and products make me extremely worried. Here’s why.
Indeed, an iodine deficiency can cause hypothyroidism—an underactive thyroid. Hypothyroidism due to iodine deficiency used to be endemic in Switzerland, where it caused goitre and cretinism.
But the most common cause of hypothyroidism nowadays is an autoimmune condition known as Hashimoto’s disease. And guess what, if you take iodine supplements you can make it worse.
Some people do indeed need more dietary iodine, but research has shown that it needs to be balanced with an adequate selenium intake. In the UK and western Europe, most individuals get an extremely low intake of selenium, due to low levels in the soil. So if these individuals then begin taking herbal medicines with a high iodine content, they are at risk of damaging their thyroid gland even more.
It’s ok to supplement iodine, and you may indeed need it if your diet is low in fish and seafood. But if you live in a low-selenium country like the UK or New Zealand, you must also supplement selenium in order to protect your thyroid. Selenium is a vital nutrient for thyroid hormone activation.
References
Ihnatowicz P, Drywień M, Wątor P, Wojsiat J. The importance of nutritional factors and dietary management of Hashimoto's thyroiditis. Ann Agric Environ Med. 2020 Jun 19;27(2):184-193
https://pubmed.ncbi.nlm.nih.gov/32588591/
Mikulska AA, Karaźniewicz-Łada M, Filipowicz D, Ruchała M, Główka FK. Metabolic Characteristics of Hashimoto's Thyroiditis Patients and the Role of Microelements and Diet in the Disease Management-An Overview. Int J Mol Sci. 2022 Jun 13;23(12):6580.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9223845/