Written by Lisa Dreher, MS, RDN, LDN
Supporting the Thyroid: Food as Medicine

Supporting the Thyroid: Food as Medicine

The thyroid is one of the most written and talked about glands in the body. It is a butterfly shaped gland that sits in your throat and regulates many of the body’s most important functions. In Functional Medicine, we pay close attention to the thyroid because of its far-reaching impact on health. The thyroid regulates the body’s metabolism by influencing how quickly you produce energy from nutrients and oxygen. For example, if you have an underactive thyroid, you won’t be able to optimally regulate your blood sugar, cholesterol, or weight. The thyroid acts somewhat like a thermometer by regulating body temperature as well as other important functions such as heart rate, brain development, the reproductive system, and bone maintenance. When the thyroid gland is not working, a person can feel downright miserable. According to the American Thyroid Association, more than 12% of the US population will develop a thyroid condition in their lifetime and an estimated 20 million Americans have some form of thyroid disease. Yet, it’s estimated that 50 to 60 percent of people with thyroid disease go undiagnosed.

As Dr. Hyman explains in his blog, “About 7 percent of your thyroid hormone is T3, the ‘active’ version, which sends messages to your DNA to turn up your metabolism to increase the fat burning in your mitochondria. T3 is critical to making every system in your body work at the right speed.T3 lowers your cholesterol, improves your memory, keeps you thin, promotes regrowth in cases of hair loss, relieves muscle aches and constipation, and even cures infertility in some patients. T4 (about 93 percent) is the inactive form of your thyroid hormone that, if everything works as designed, your body will convert into T3. If you produce too little T3, or the T4 you produce is not properly converted into this active thyroid hormone, your whole system goes haywire.”

Here is a list of common signs and symptoms for over and underactive thyroid conditions:

Signs of hyperthyroidism (overactive thyroid):

  • unexpected and/or sudden weight loss
  • insomnia
  • rapid heartbeat/palpitations
  • increased sensitivity to heat
  • excess sweating
  • irritability and nervousness
  • large/bulging eyes
  • muscle weakness
  • multiple bowel movements daily
  • tremor/shaking in hands and feet
  • fine, brittle hair
  • muscle pain

Signs of hypothyroidism (underactive thyroid):

  • being very sensitive to cold/ having cold hands and feet
  • low body temperature
  • sluggishness in the morning
  • constipation
  • poor concentration and memory
  • low-grade depression
  • dry skin
  • hoarse voice
  • weakness or cramps
  • low sex drive
  • fluid retention
  • high cholesterol


There are many possible reasons for thyroid dysfunction, and it is probably no surprise that nutrient deficiencies can play a key role. The following are 5 common nutrient deficiencies seen in thyroid dysfunction and a list of the best sources to help you get enough in your diet:

  1. Selenium is needed for the proper conversion of T4 to T3. Selenium also acts as an antioxidant in the body and may help reduce inflammation that can specifically impact the thyroid. While severe deficiency is rare, suboptimal levels may impact thyroid function. However, too much selenium supplementation can lead to gastrointestinal distress, hair/nail changes, fatigue, and even nerve damage. This is why I suggest food first.
    Best sources: Brazil nuts (they are very concentrated in selenium, so most people only need 1-3 nuts most days to meet their needs), shrimp, halibut, sardines, grass-fed beef, salmon and turkey.
  1. Iodine is needed to stimulate the production of T4 and supports the conversion to T3, so getting enough in the diet is important. While iodine deficiency is the most common cause of hypothyroidism, too much iodine supplementation can also cause harm. This is why iodine is a controversial nutrient when it comes to thyroid health. Not unlike other nutrients, a balance is needed to support optimal health. Iodine supplementation will impact the thyroid most significantly in the presence of selenium deficiency. You should have your levels checked and monitored by an experienced practitioner.
    Best sources: seaweed (an easy way to get this is by sprinkling some Dulse on your food. Sea Seasonings is a good brand), eggs, saltwater fish, and shellfish.
  1. Vitamin A is needed for many functions throughout the body including hormone synthesis and production of T3. Vitamin A has been shown in research to reduce elevated TSH levels and increase T3 levels in obese and nonobese premenopausal women. Similar to the previous two nutrients, vitamin A in excess amounts can lead to problems, so it is best to get your vitamin A from whole food sources rather than supplementation, unless you are being monitored. Try to incorporate the following into your diet regularly.
    Best sources: liver (this is a very concentrated source and you do not need much), carrots, sweet potato, kale, spinach, mustard/collard/turnip greens, and winter squash.
  1. Vitamin D is another key nutrient to monitor with hypothyroidism, as research shows an association between low levels and the severity of thyroid symptoms. Additionally, low vitamin D has been associated with several autoimmune conditions, specifically with autoimmune thyroid disease. Most of my patients are low or deficient in vitamin D and getting your levels checked is very important, not just for thyroid health but overall health and immune support. It is difficult to get vitamin D from the diet alone and supplementation may be needed. However, there are some good sources.
    Best sources: salmon, sardines, mackerel, eggs, and mushrooms. It is best to go out and get direct sunshine to promote the synthesis of vitamin D from cholesterol.
  1. Magnesium works alongside iodine to stimulate the production of T4 and supports the conversion to T3. Magnesium is also needed to support over 300 enzymes throughout the body and many people are suboptimal or deficient in this very important mineral. Other signs of low magnesium include constipation (often seen with hypothyroidism), muscle cramping, high blood pressure, asthma, and irregular heartbeat.
    Best sources: pumpkin seeds, almonds, spinach, swiss chard, sesame seeds, quinoa, cashews, dark chocolate and avocado.

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