The mineral iodine, found predominantly in the ocean and in variable amounts in the soils of the world, is essential for thyroid function. To ensure everyone was getting enough, table salt was fortified with the mineral starting in the 1920s. Given that sodium is considered one of the leading dietary killers in the world, however, iodized salt should not be considered as a viable source (though if you do add salt to foods, use iodized salt instead of “sea salt” or other non-iodized varieties).

The Most Healthful Iodine Source

The most concentrated, healthful source is seaweed, which has the iodine of seafood without the fat-soluble pollutants that build up in the aquatic food chain. Sea vegetables are the underwater dark-green leafies, and I encourage you to experiment with ways to include them in your diet. The recommended daily intake of iodine is 150 mcg, which is what is in about two sheets of nori, the seaweed used to make sushi, or a half-teaspoon of the seaweeds arame or dulse. I caution against hijiki (also spelled hiziki), because it has been found to be contaminated with arsenic, as well as kelp, which may have too much iodine. (Just a half-teaspoon of kelp could exceed the daily upper limit.) Too much iodine can cause excessive thyroid gland activity.

Passing Over Pork Products

How else may we protect our thyroid health? One way is by minimizing exposure to pork products. Nearly 100,000 Americans are sickened each year by Yersinia bacteria. In every outbreak for which a source has been found, the culprit was contaminated pork. In most cases, Yersinia food poisoning leads to little more than acute gastroenteritis, but the symptoms can become severe and mirror appendicitis, resulting in unnecessary emergency surgeries. Long-term consequences of Yersinia infection include chronic inflammation of the eyes, kidneys, heart, and joints. Studies have found that within a year of contracting Yersinia food poisoning, victims appear 47 times more likely to come down with autoimmune arthritis, and the bacteria may also play a role in triggering an autoimmune thyroid condition known as Graves’ disease. How contaminated are U.S. pork products? Consumer Reports magazine tested nearly 200 samples from cities across the country and found that more than two-thirds of the pork was contaminated with Yersinia.

What About Soy Products?

Tofu, soy milk, miso, tempeh, edamame, and other soy products—including the soybeans themselves—are high in the same nutrients we associate with other legumes, such as fiber, iron, magnesium, potassium, protein, and zinc. Do they have any negative effects on thyroid function?

Soy Foods and Our Thyroid

Soy has so-called goitrogenic compounds (as do flaxseeds and vegetables in the broccoli family), and they can interfere with thyroid function in people with marginal iodine intake. The answer is not to avoid these super healthy foods, but to make sure you get enough iodine.

Soy and Thyroid Medication

Soy foods may inhibit the oral absorption of Synthroid, thyroid hormone replacement drugs, but so do all foods. That’s why we tell patients to take it on an empty stomach.

For substantiation of any statements of fact from the peer-reviewed medical literature, please see the associated videos below.

Image Credit: ChesiireCat / Thinkstock. This image has been modified.

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