The Top 4 Nutrients to Support Thyroid Function

by Lacy Kuester MS, MPP, RDN Nutrition
Aerial view of foods.

Suboptimal thyroid levels have long been associated with cognitive dysfunction, including Alzheimer’s disease. For this reason, multiple thyroid related labs are often involved in a work up for Alzheimer’s disease and mild cognitive impairment. Optimizing these levels is an important part of restoring cognitive health.

What is the Thyroid Gland?

Your thyroid is a hormone-secreting gland located in the front of your neck. It plays a role in growth, metabolism, and brain function (1, 2). Your thyroid is part of a feedback loop with your brain and bloodstream, all of which work together to keep your hormone levels balanced. If your brain registers high levels of thyroid hormones in your blood, it tells your thyroid to secrete less. If your brain detects low circulating levels of thyroid hormone, it signals your thyroid to start increasing its hormone production (2). The balance of your thyroid hormones is important for your mood, energy levels, and cognitive health.

Understanding Your Thyroid Labs

There are several different thyroid-related tests, all of which tell you something different about your thyroid function.

  • TSH-- this is the hormone secreted by the brain that tells your thyroid to produce its hormones. If your TSH is high, it means your brain is sending a strong signal to your thyroid to ramp up its hormone production because it senses too little in your blood. If your TSH is low, it means your brain thinks you have too much circulating thyroid hormone, so it doesn’t want to stimulate your thyroid to make more (2).
  • Free T3 and Free T4 --these labs measure the circulating levels of the hormones secreted by your thyroid that are available for use by your body. Your body makes much more T4 than T3, but it uses more T3 than T4. The cells that need T3 to perform their functions can convert T4 to T3 (2). If your brain is secreting high levels of TSH but your T3 and T4 remain low, it could signal that your thyroid is sluggish and not responding to stimulation. Alternatively, if your brain has stopped sending TSH to your thyroid but your hormones remain elevated, your thyroid is likely hyperactive, refusing to shut down even though your brain is telling it to do so.
  • Reverse T3-- When your body converts T4 to T3, not all of it becomes free T3. Some of it becomes reverse T3. This molecule cannot be used by your body and actually blocks free T3 from binding with cells. If you have high reverse T3 compared to free T3, then your body will have a difficult time using your active thyroid hormone. You can think of free T3 and reverse T3 as your body’s accelerator and brake. High reverse T3 means you are pressing the break when you need to accelerate. High reverse T3 has been linked with neurodegenerative disorders, inflammation, depression, anxiety, and fatigue (3).

The Role of Nutrition in Thyroid Function

At the Amos Institute, we work with many clients who have suboptimal thyroid hormone levels. While thyroid issues are complex and require very targeted and individualized intervention, much improvement can be made with nutritional modifications. Certain nutrients are needed by your body to form and convert your thyroid hormones. Consuming a variety of vegetables, nuts, and organic protein sources can help you ensure that you get the right nutrients to support your cognitive and thyroid health (4). Here are some of the most important micronutrients for optimizing thyroid health.

Iron: needed for the first stages of thyroid hormone creation

Iron Rich Foods:

  • Protein-rich animal products like grass-fed meat, wild-caught fish, and pasture-raised poultry and eggs
  • Organic, iron-fortified tofu
  • Spinach
  • Broccoli
  • Pecans, walnuts, pistachios, roasted almonds, roasted cashews, or sunflower seeds
  • Lentils
  • Beans

Iodine: the building block of every molecule of thyroid hormone

Iodine Rich Foods:

  • Pasture-raised eggs
  • Produce grown in iodine-rich soil, which the US has in abundance
  • Seaweed
  • Wild caught shrimp sourced from the Northwest Atlantic Ocean off of Nova Scotia

Selenium: required to convert T4 to T3

Selenium Rich Foods:

  • Brazil nuts (a one-ounce serving of 6-8 nuts contains 10 times the selenium you need each day. Limit your intake to 1-2 nuts every other day to avoid selenium toxicity)
  • Wild-caught sardines and salmon
  • Grass-fed meats
  • Pasture-raised poultry and eggs
  • Mushrooms
  • Spinach
  • Cashews
  • Lentils

Zinc: required to convert T4 to T3

Zinc Rich Foods:

  • Grass-fed meat
  • Pasture-raised eggs
  • Lentils
  • Pumpkin, flax, and hemp seeds
  • Cashews


  1. InformedHealth. (2010). How does the thyroid gland work? [Updated 2018 Apr 19]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG). Available from:
  2. Shahid M.A. & Sharma, S. (2019). Physiology, thyroid Hormone. [Updated 2019 Mar 23]. Treasure Island, FL: StatPearls Publishing. Available from: books/NBK500006/
  3. Smith, P. (2016). The importance of reverse T3.Townsend Letter, 396. https://
  4. O’Kane, S., Mulhern, M., Pourshahidi, L., Strain, J., & Yeates, A. (2018). Micronutrients, iodine status and concentrations of thyroid hormones: a systematic review.Nutrition Reviews, 76(6), 418–431.