The thyroid gland is a butterfly-shaped organ located in the neck. Although it is small in size, the thyroid produces hormones that act as chemical messengers to regulate many different processes in the body. A poorly functioning thyroid gland can have a negative impact on your health and cause a range of symptoms throughout your entire body. In this blog, we will discuss the best foods to eat in order to support thyroid health, as well as what foods to avoid.
What is the function of the thyroid gland?
The thyroid gland produces hormones that are important for several different body functions. The main hormones produced by the thyroid are triiodothyronine (T3) and thyroxine (T4). T4 is a largely inactive hormone. After it is released from the thyroid, certain organs in the body convert it to T3 so it can act on cells and body processes (Cleveland Clinic, 2022).
FT3 (free triiodothyronine) and FT4 (free thyroxine) refer to the unbound, or free, forms of T3 and T4. They are considered the biologically active forms of the hormones that can enter cells and exert an effect on the body. Free hormone levels are most often measured in blood tests to assess thyroid function because it accurately represents the hormones available for use by the body’s tissues.
What are the functions of thyroid hormones?
Thyroid hormones play a crucial role in regulating the body’s metabolism and influencing how fast or slow various processes occur in our bodies. This means they help control the rate at which cells convert nutrients into energy, affecting body temperature, heart rate, and digestion. Additionally, thyroid hormones are essential for normal growth and development, particularly in children, as well as fertility in women. If the thyroid does not function correctly, levels of thyroid hormones can be too high or too low, leading to various health problems affecting almost every body system (Cleveland Clinic, 2022).
What is hypothyroidism?
Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormones to meet the body’s needs. This is also called an underactive thyroid. Thyroid hormones play a crucial role in regulating metabolism, so when there is a deficiency, it can slow down various bodily functions. Possible symptoms that occur with hypothyroidism are:
- Weight gain
- Muscle cramps
- Irregular periods
- Dry and pale skin
- Sensitivity to cold
- Hair loss
- Chronic constipation
- Lowered sex drive
Source: NIDDK, 2021
What is hyperthyroidism?
Hyperthyroidism occurs when the thyroid produces an excessive amount of thyroid hormones. This is also known as an overactive thyroid. Just as hypothyroidism slows down many body functions, hyperthyroidism can speed them up. Common symptoms of hyperthyroidism include:
- Weight loss
- Sensitivity to heat
- Rapid heartbeat
- Anxiety or irritability
- Trembling hands
- Enlarged thyroid gland (goiter)
- Increased bowel movements
Source: Penn Medicine, 2023
Both an under- and overactive thyroid can cause unpleasant symptoms and negatively impact your health over time. If you suspect you may have thyroid problems, a blood test is the most reliable way to check the levels of thyroid hormones. This can be done at your GP or using a home test, such as Homed-IQ’s Thyroid Home Test. This laboratory test checks the level of FT3, FT4 and thyroid-stimulating hormone using a blood sample collected from home.
Foods to avoid with hypothyroidism
Experts say there is no specific diet that can fix an underactive thyroid, but certain foods can affect thyroid function and certain medications used to treat hypothyroidism.
- Soy: Soy products contain compounds that can interfere with thyroid hormone production and may affect the absorption of hypothyroidism medication. While soy intake alone is not known to cause hypothyroidism, it is advised to wait four hours after taking thyroid medication to consume any foods that contain soy (Nippoldt, 2021). Foods containing soy include soybeans, tofu, soy milk, and tempeh.
- Cruciferous vegetables: Vegetables like broccoli, cauliflower, cabbage, and brussels sprouts contain goitrogens, or substances that impact the production of thyroid hormones. Consuming large amounts of cruciferous vegetables could impact thyroid hormone production (Felker et al., 2016). People with hypothyroidism can consume these vegetables in moderation. It is advised to cook these vegetables before consuming them to reduce the effects.
- Processed foods and added sugars: While processed foods have no documented impact on thyroid function, eating a healthy and balanced diet can help manage symptoms, weight, and overall well-being.
Foods to avoid with hyperthyroidism
- Iodine-rich foods: While sufficient iodine is necessary for the thyroid to function, excessive intake can worsen hyperthyroidism symptoms and interfere with certain treatments (Farebrother et al., 2019). If you have hyperthyroidism, speak to your doctor about whether you should avoid foods containing iodine such as seaweed, iodized salt, seafood, and certain dairy products.
- Caffeine: High caffeine intake can exacerbate symptoms of hyperthyroidism, such as rapid heartbeat and anxiety (Johnson, 2022). Reducing consumption of coffee, tea, energy drinks, and chocolate may help manage the symptoms of hyperthyroidism.
Foods that can help support a healthy thyroid
While most thyroid conditions are not caused by nutrition alone, certain foods can help support your thyroid’s function. Foods and nutrients that can have a positive effect on the thyroid include:
- Selenium: Selenium is an essential mineral that plays a vital role in thyroid function. The thyroid gland requires selenium to produce and metabolise thyroid hormones (Ventura et al., 2017). Brazil nuts, one of the highest dietary sources of selenium, can be beneficial for individuals with thyroid conditions, as they can help ensure sufficient selenium intake. However, it is important to consume brazil nuts in moderation due to their high selenium content, as excessive selenium intake can have negative effects on thyroid health.
- Iodine: Iodine is an essential mineral required for the synthesis of thyroid hormones, as the thyroid gland absorbs iodine from the bloodstream to produce T4 and T3 (Harvard Health, 2023). Sufficient iodine is required for the thyroid to function normally, and a deficiency can contribute to hypothyroidism. Consuming foods such as seaweed, seafood (such as fish and shrimp), dairy products, and iodized salt can ensure your iodine intake is sufficient for thyroid health (Cleveland Clinic, 2022). If you are diagnosed with hyperthyroidism, speak to your doctor about whether avoiding iodine-rich foods is advisable.
- Zinc: Like selenium, zinc is needed for thyroid hormone production and thyroid function. Inadequate zinc intake can result in hypothyroidism, and hypothyroidism can cause impaired zinc absorption (Betsy et al., 2013). Zinc is found in meat, cheese, grain products, nuts, and seafood such as shrimp and mussels.
- Iron: Low iron levels or anemia due to iron deficiency can affect thyroid metabolism, potentially leading to hypothyroidism (Ashraf et al., 2017). Studies have also observed individuals with both hypothyroidism and hyperthyroidism had a higher odds of having anemia, although the mechanism of how thyroid dysfunction can lead to anemia is not yet understood (Wopereis et al., 2018). To ensure adequate iron levels, consume foods like red meat, fish, nuts, and eggs. If you would like to check your iron levels, try Homed-IQ’s Anemia Blood Test.
While there is no specific diet that can cause or cure a thyroid problem, eating a balanced diet that includes foods and nutrients necessary for thyroid function is the best way to support your health .Do you have symptoms of an over- or underactive thyroid? Speak to your doctor about checking your thyroid hormones or perform a home test with Homed-IQ.
Ashraf, A. T., De Sanctis, V., Yassin, M. A., Wagdy, M., & Soliman, N. (2017). Chronic anemia and thyroid function. PubMed, 88(1), 119–127. https://doi.org/10.23750/abm.v88i1.6048
Cleveland Clinic. (2022, July 6). Thyroid: What It Is, Function & Problems. https://my.clevelandclinic.org/health/body/23188-thyroid?_ga=2.216298646.1676197451.1683478243-1652938380.1679988763&_gac=1.26605007.1680769738.Cj0KCQjwuLShBhC_ARIsAFod4fLxCQZuvBv0NADal6kXRVhThe-zXsd-h48Sqo5YvQEv1ZzI81AllLkaAtHwEALw_wcB#:~:text=Your%20thyroid%20is%20an%20important,conditions%20are%20common%20and%20treatable.
Farebrother, J., Zimmermann, M. B., & Andersson, M. (2019). Excess iodine intake: sources, assessment, and effects on thyroid function. Annals of the New York Academy of Sciences. https://doi.org/10.1111/nyas.14041
Felker, P. M., Bunch, R. A., & Leung, A. Y. M. (2016). Concentrations of thiocyanate and goitrin in human plasma, their precursor concentrations in brassica vegetables, and associated potential risk for hypothyroidism. Nutrition Reviews, 74(4), 248–258. https://doi.org/10.1093/nutrit/nuv110
Harvard Health. (2023, March 7). Iodine. The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/iodine/#:~:text=Iodine%20is%20needed%20to%20make,well%20as%20regulating%20normal%20metabolism.
Hypothyroidism (Underactive Thyroid). (2022). National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism#symptoms
Nippoldt, T. B. (2021, October 5). Soy: Does it worsen hypothyroidism? Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/hypothyroidism/expert-answers/hyperthyroidism/faq-20058188
Penn Medicine. (2025). Hyperthyroidism (Overactive Thyroid). https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/hyperthyroidism-overactive-thyroid
Ventura, M., Coelho, A., & Carrilho, F. (2017). Selenium and Thyroid Disease: From Pathophysiology to Treatment. International Journal of Endocrinology, 2017, 1–9. https://doi.org/10.1155/2017/1297658
Wopereis, D. M., Du Puy, R. S., Van Heemst, D., Walsh, J., Bremner, A., Bakker, S. J. L., Bauer, D. C., Cappola, A. R., Ceresini, G., Degryse, J., Dullaart, R. P. F., Feller, M., Ferrucci, L., Floriani, C., Franco, O. H., Iacoviello, M., Iervasi, G., Imaizumi, M., Jukema, J. W., . . . Elzen, W. P. J. D. (2018). The Relation Between Thyroid Function and Anemia: A Pooled Analysis of Individual Participant Data. The Journal of Clinical Endocrinology and Metabolism, 103(10), 3658–3667. https://doi.org/10.1210/jc.2018-00481
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