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The thyroid gland is a butterfly-shaped organ located in the neck. Although small in size, it produces hormones that act as chemical messengers to regulate many different processes in the body. A poorly functioning thyroid can negatively impact your health and lead to a variety of symptoms throughout your body. In this blog, we discuss the best foods to eat to support thyroid health and which foods are better to avoid.
Table of Contents
- What is the function of the thyroid gland?
- What are the functions of thyroid hormones?
- What is hypothyroidism and hyperthyroidism?
- Foods that may support healthy thyroid function
- Foods to avoid with hypothyroidism
- Foods to avoid with hyperthyroidism
- Summary
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.
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.
Source: Cleveland Clinic, 2022
What are the functions of thyroid hormones?
Thyroid hormones influence many vital functions in the body, including:
- Regulate metabolism and energy use
- Control body temperature, heart rate, and digestion
- Support growth in children and fertility in women
- Imbalances (too high or too low) can affect nearly every body system
Source: Cleveland Clinic, 2022.
What is hypothyroidism and hyperthyroidism?
| Condition | Description | Common Symptoms |
|---|---|---|
| Hypothyroidism (Underactive Thyroid) | The thyroid does not produce enough hormones, slowing down metabolism and body functions. | – Weight gain – Muscle cramps – Irregular menstruation – Dry and pale skin – Sensitivity to cold – Hair loss – Chronic constipation – Decreased libido |
| Hyperthyroidism (Overactive Thyroid) | The thyroid produces too much hormone, speeding up metabolism and body functions. | – Weight loss – Sensitivity to heat – Rapid heartbeat – Anxiety or irritability – Fatigue – Sweating – Trembling hands – Enlarged thyroid (goiter) – Increased bowel movements |
Source: NIDDK, 2021; 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 that can help support a healthy thyroid
Diet alone won’t treat thyroid disease, but these nutrients are vital for thyroid health:
- Selenium: Needed for hormone production and metabolism. Brazil nuts are the richest source, but just 1-2 per dayis enough; too many can be harmful. Other sources: fish, eggs, sunflower seeds.
- Iodine: Essential for making thyroid hormones T3 and T4. Found in seaweed, seafood, dairy, and iodized salt. Deficiency can lead to hypothyroidism, but avoid supplements unless prescribed, as excess iodine can worsen thyroid conditions.
- Zinc: Supports hormone production and absorption. Found in meat, seafood (shrimp, mussels), nuts, seeds, and whole grains.
- Iron: Important for thyroid hormone metabolism. Low iron or anemia can worsen thyroid problems. Good sources include red meat, fish, eggs, and nuts. Note: Don’t take iron supplements at the same time as thyroid medication, as they reduce absorption.
Sources: Ventura et al., 2017; Harvard Health, 2023; Cleveland Clinic, 2022; Betsy et al., 2013; Ashraf et al., 2017; Wopereis et al., 2018
Foods to avoid with hypothyroidism
There’s no special diet that can cure an underactive thyroid, but some foods may interfere with thyroid function or with medication:
- Soy: Found in soybeans, tofu, soy milk, and tempeh. Soy can reduce how well your thyroid medication is absorbed. Wait at least 4 hours after taking medication before eating soy.
- Cruciferous vegetables: Broccoli, cauliflower, cabbage, and Brussels sprouts contain compounds (goitrogens) that may affect thyroid hormone production if eaten in large amounts. They’re fine in moderation—especially when cooked.
- Processed foods & added sugars: These don’t directly harm the thyroid but can worsen weight gain and fatigue. A balanced diet helps manage symptoms and overall wellbeing.
Source: Nippoldt, 2021; Felker et al., 2016
Foods to avoid with hyperthyroidism
An overactive thyroid speeds up body functions, and certain foods can make symptoms worse:
- Iodine-rich foods: Too much iodine can aggravate hyperthyroidism and interfere with treatment. Limit foods such as seaweed, iodized salt, seafood, and some dairy; but only under your doctor’s advice.
- Caffeine: Coffee, tea, energy drinks, and chocolate can trigger or worsen rapid heartbeat, anxiety, and restlessness. Reducing caffeine may ease symptoms.
Source: Farebrother et al., 2019; Johnson, 2022
Summary
The thyroid gland produces the hormones T3 and T4, which regulate metabolism, energy, temperature, heart rate, digestion, growth, and fertility. Imbalances can cause hypothyroidism (too little hormone, slowing body functions) or hyperthyroidism (too much hormone, speeding them up), each with distinct symptoms that affect overall health. Blood tests measuring FT3, FT4, and TSH provide the most accurate assessment. While diet cannot cure thyroid disorders, nutrients like selenium, iodine, zinc, and iron support healthy thyroid function, while certain foods—such as excess soy, raw cruciferous vegetables, iodine-rich foods, and caffeine—may worsen symptoms depending on the condition.
References
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
