Optimal diet for hypothyroidism: Foods to include and avoid

Hypothyroidism, or an underactive thyroid, is a common thyroid disorder where the thyroid gland does not produce enough thyroxine (T4), a hormone essential for regulating various body functions. 

This can result from a malfunction in the pituitary gland, which may fail to signal the thyroid effectively by releasing adequate Thyroid Stimulating Hormone (TSH), or the thyroid may not produce enough T4 and T3 (active hormone). Regular thyroid testing is typically necessary to monitor these levels.

Common symptoms include fatigue, low mood, dry skin, hair thinning, sensitivity to cold, constipation, low libido, menstrual irregularities, weight gain, and difficulty with concentration.

How hypothyroidism impacts metabolism

The thyroid is key due to its impact on metabolism and energy regulation. When thyroid function is low, it hinders the body’s ability to regulate blood sugar, cholesterol, and weight.
 
Additionally, the thyroid influences body temperature, heart rate, brain development, reproductive health, and bone maintenance. Thus, low thyroid function can disrupt multiple metabolic and physiological processes, including:

• carbohydrate, protein, and fat metabolism
• vitamin absorption
• mitochondrial and muscle function
• blood flow and oxygen use
• hormone regulation

A personalised approach to hypothyroidism

Since the thyroid is sensitive to changes in overall health, a personalised approach to hypothyroidism and nutrition is essential. An in-depth, individualised approach is needed and in this multifaceted condition the following factors should be thoroughly examined:

• stress and adrenal function
• gut health and immunity
• infection history (viral or bacterial)
• gluten sensitivity
• environmental toxins
• nutrient deficiencies

Chronic conditions and hypothyroidism

Hypothyroidism is often connected to other health issues, either as a cause or effect, including:

• obesity
• diabetes
• cardiovascular disease and high cholesterol
• autoimmune disorders (notably Hashimoto’s disease)

Comprehensive testing often includes evaluating thyroid function, gut health, immune response, toxicity, and stress.

Key nutrients for thyroid health

Iodine

Essential for producing T4 and converting it to T3, iodine is crucial in the diet but should be balanced carefully to avoid potential harm. Best sources include seaweed, eggs, saltwater fish, and shellfish.

Zinc

Important for T4-to-T3 conversion and TSH production. Good sources are shellfish, red meats, legumes, pumpkin seeds, and nuts.

Selenium

Vital for T4-to-T3 conversion and reducing thyroid inflammation, selenium is concentrated in foods like Brazil nuts, shrimp, halibut, sardines, grass-fed beef, salmon, and turkey.

To meet the recommended daily intake of selenium (about 55 micrograms for most adults), here are a few examples of selenium-rich foods and their typical portions:

• Brazil nuts: The highest natural source of selenium. 1-2 Brazil nuts (5–6 grams): Provides around 68–95 micrograms of selenium, meeting or exceeding the daily requirement in just one or two nuts.
• Yellowfin tuna: A rich seafood source. 3 ounces (85 grams) of cooked yellowfin tuna contains about 92 micrograms of selenium, which is roughly 167% of the daily value.
• Sardines (canned in oil): Another good seafood option. 3 ounces (85 grams): Contains about 45 micrograms of selenium, providing approximately 82% of the daily value.
• Turkey (light meat, cooked): Common in many diets. 3 ounces (85 grams) offers about 31 micrograms of selenium, which is 56% of the daily value.
• Eggs: Widely accessible and versatile. 1 large egg provides approximately 15–20 micrograms of selenium, about 27–36% of the daily value.
• Sunflower seeds: An easy plant-based source.1 ounce (28 grams) contains around 19 micrograms of selenium, which is 34% of the daily value.

Potentially harmful nutrients

Goitrogens

Found in some plant foods, goitrogens can interfere with thyroid function by limiting iodine absorption. Cooking these foods can reduce their goitrogen content.

Soy

Soy isoflavones may inhibit thyroid hormone synthesis and elevate TSH, so it is generally best to avoid soy products if you have a thyroid imbalance.

Gluten

Individuals with thyroid issues often have a sensitivity to gluten. A gluten-free diet can help reduce inflammation and prevent immune reactions that might impact the thyroid.

Processed foods

High-sugar and processed foods can worsen inflammation and hormonal imbalances, disrupting thyroid health.

Recommended diet for hypothyroidism

An ideal diet for hypothyroidism includes ample fruits and vegetables, lean proteins, healthy fats, and moderate complex carbohydrates. A gluten-free Mediterranean or Paleo-style diet may work well, but a personalised approach considering individual health factors is always best.

Weight management tips for hypothyroidism

If it has been recommended that you lose weight but hypothyroidism is making weight loss difficult, here are some tips to keep in mind:

• Rest: Poor sleep is linked to weight gain, especially around the abdomen.
• Mindful eating: Paying attention to hunger and eating slowly can improve your relationship with food and support weight management.
• Yoga or meditation: These practices help reduce stress, a factor that can impact thyroid function and weight.
• Exercise: Moderate to high-intensity exercise may boost thyroid hormones, but lower-impact routines are advisable for those with fatigue or pain.

Working with an experienced practitioner such as a registered dietitian can help develop a tailored plan to address thyroid health and related symptoms comprehensively.

References

Chaker, L., Bianco, A. C., Jonklaas, J., & Peeters, R. P. (2017). Hypothyroidism. The Lancet, 390(10101), 1550–1562. 

Leung, A. M., & Pearce, E. N. (2013). The role of iodine in thyroid function in health and disease. Obstetrical & Gynecological Survey, 68(10), 687–697. 

Zimmermann, M. B., & Boelaert, K. (2015). Iodine deficiency and thyroid disorders. The Lancet Diabetes & Endocrinology, 3(4), 286–295. 

Duntas, L. H., & Benvenga, S. (2015). Selenium: An element for life. Endocrine, 48(3), 756–775. 

Messina, M., & Redmond, G. (2006). Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: A review of the relevant literature. Thyroid, 16(3), 249–258.