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  • Writer's pictureDr. Stefanacci

Your Thyroid from a Functional Perspective - Part 3: Nutrients

Over the past few weeks we’ve been taking a close look at the thyroid gland from a functional perspective. Part 1 explored how the thyroid gland works, the different types of thyroid imbalances, and the symptoms they may produce. In Part 2 we explored those symptoms further by discussing some of the root causes of these thyroid imbalances.

For Part 3, we are going to take a closer look at one of those root causes - nutrient deficiencies and explain how certain nutrients can effect the thyroid’s function.

How thyroid conversion works

Although we discussed the thyroid conversion process in detail in Part I of our series, let’s have a quick refresher.

Your thyroid gland produces hormone T4, but your body needs to convert T4 into T3 for it to become active. The active form of this hormone is what your body uses to maintain a healthy balance. When your body doesn’t convert enough T4 to T3 naturally, or when your body doesn’t have enough of the key nutrients that assist in this conversion, you start to feel the symptoms of an imbalanced thyroid.

How nutrient deficiencies affect thyroid conversion

It’s common for those individuals who are experiencing hypothyroidism or struggling with a thyroid imbalance to also find that they are lacking in certain vitamins and minerals that play a role in the thyroid’s conversion process.

In some cases, an autoimmune disorder can be the cause of a thyroid condition, like Hashimoto’s. This is where the immune system mistakenly sends out antibodies to attack the thyroid, resulting in an increase of thyroid peroxidase antibodies, or TPO antibodies, in the thyroid gland.

While nutrients deficiencies aren’t the only thing that can affect your thyroid health, they can play a large role in achieving a balanced thyroid. If you and your doctor find that your nutrient levels might be affecting your wellness, here are some of the vitamins to focus on and some ways in which you can introduce them into your wellness journey.


This micronutrient and antioxidant is necessary for thyroid function as well as maintenance of healthy antibody levels. In fact, the thyroid gland has the highest concentration of selenium per gram of tissue compared to all other tissues in the human body. Selenium is needed for the deiodinase enzymes, which are necessary to properly convert T4 to T3. Selenium has also been shown to decrease TPO antibody levels in individuals suffering from autoimmune thyroiditis.

Supplementation with organic forms of selenium such as selenomethionine or selenocysteine have proven to be the best way for the body to absorb selenium. In addition to supplements, eating a handful of Brazil nuts a day contains the necessary daily dose of 200mcg of selenium.


Similarly to selenium, zinc is important for the conversion of thyroid hormone. Conversely, thyroid hormones are important for the absorption of zinc. Studies have shown that in some instances thyroid medications and supplements work markedly better with the addition of zinc supplementation.

The best source of zinc outside of a supplement is found in shellfish, specifically oysters. 6 medium oysters contain 32 mg of zinc, or 291% of the DV. Red meat is another great way for your body to absorb zinc, however, if you don’t eat animal products, you can find zinc in legumes, like chickpeas, lentils, and beans, although your body has a harder time absorbing zinc through non-animal products.


Iodine plays an important role in the synthesis of thyroid hormones and has been shown to help improve TSH levels. However, it is slightly controversial because, while you need iodine to make T4, too much iodine can lead to hypothyroidism.

It is recommended that adults get 150 micrograms of iodine a day, according to the National Institute for Health. The body does not produce iodine on its own so be sure to get supplemental iodine from foods like kale, seaweed, shrimp, and cod. You’ll want to keep a close eye on your iodine levels with your doctor to make sure you’re not taking too much.

Vitamin A

This fat-soluble vitamin has been shown to inhibit secretion in the thyroid gland and normalize TSH levels. A 2012 trial found that women who were given vitamin A supplementation over a period of 4 months had a significant reduction in TSH concentration and an increase in T3.

Retinol is the true form of vitamin A and is most easily absorbed by the body. Retinoids can be found in animal products like beef liver, eggs, and salmon. Another form of vitamin A is carotenoids, which need to be converted to retinol by your body. This form of vitamin A can be found in plant products like carrots, sweet potatoes, and even fruits like mangoes and apricots.


Iron deficiency effects about 20% of the world’s population. Iron is an important component in the normal functioning of thyroid peroxidase, which is necessary to produce T4 and convert it to T3.

A healthy gut is important for proper assimilation of nutrients, including iron. If the gut is healthy, foods such as grass-fed beef, liver, and spinach can be used to improve iron levels. Using cast iron cookware can also increase how much iron you’re getting.


Copper, the third most abundant mineral in the human body, also plays a role in thyroid metabolism. Healthy levels of copper have been shown to increase levels of T4 while preventing over absorption. When blood copper levels are low, thyroid hormone levels decrease.

The most bioavailable copper comes from animal products, such as grass-fed liver and oysters. Sesame seeds are also a good plant source of copper.

So what now?

We’ve covered a lot of ground with our series on the Thyroid from a Functional Perspective. From understanding the thyroid’s role in your body, understanding the variety of root causes that can change your thyroid’s function, to taking a look at some of the nutrients that impact thyroid health.

More than anything, we want you to feel empowered about your thyroid health, to understand why you’re experiencing symptoms and what you can do to reach your optimal health. When looking at your thyroid, most conventional doctors will just look at your thyroid-stimulating hormone (TSH), while overlooking nutrient levels which, as we’ve discussed above, play an important role in how your thyroid maintains a balance.

If you have thyroid condition or want to learn more about your thyroid health, you can choose to approach your thyroid health from a functional perspective. By looking at more than just your symptoms, testing more than just your TSH levels, and taking the time to understand your overall wellness, functional medicine offers a sustainable option for reaching your optimal thyroid health.

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