The best foods for your thyroid

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 produces hormones that are important for various bodily functions. The main hormones produced by the thyroid are triiodothyronine (T3) and thyroxine (T4).

T4 is largely an inactive hormone. After it is released from the thyroid, certain organs in the body convert it into T3, allowing it to act on cells and bodily 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 effects on the body. Free hormone levels are most often measured in blood tests to assess thyroid function, as they provide an accurate picture of 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?

Source: NIDDK, 2021; Penn Medicine, 2023

Both underactive and overactive thyroid function can cause unpleasant symptoms and negatively affect your health over time. If you suspect a thyroid problem, a blood test is the most reliable way to check thyroid hormone levels. This can be done through your general practitioner or with a home test, such as the Homed-IQ Thyroid Home Test. This laboratory test measures levels of FT3, FT4, and thyroid-stimulating hormone using a blood sample collected at home.

Foods that Support Healthy Thyroid Function

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 day is 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.