Hashimoto's thyroiditis (HT), a condition that results in an underactive thyroid, is the most common autoimmune condition globally. It is characterized by thyroid antibodies, particularly anti-thyroperoxidase (TPO) that attack thyroid tissue. On lab tests, hypothyroidism (underactive thyroid) is diagnosed by the presence of elevated TSH (thyroid-stimulating hormone) levels and reduced thyroid hormones (T4 and T3).
While genetics play a dominant role in Hashimoto’s development (70-80%), environmental factors account for 20-30% of the risk. Included in environmental factors are nutritional needs, making diet a foundational way to manage this condition. Certain dietary choices can reduce inflammation, alleviate immune overactivation, provide necessary vitamins and minerals, and improve gut health. Emerging research highlights a complex connection between gut health and Hashimoto’s, suggesting that improving gut function may reduce thyroid inflammation.
This guide delves into the best dietary approaches for Hashimoto's and hypothyroidism and explores common myths around thyroid health.
The Mediterranean Diet: A Foundation for Thyroid Health
Also known as an anti-inflammatory diet, the Mediterranean diet provides an excellent framework for supporting Hashimoto's. The Mediterranean diet has benefits for autoimmune conditions generally given its positive effects on inflammation, immune function, and the gut microbiota and its antioxidant qualities. It is a plant-forward diet that emphasizes:
High consumption of vegetables, fruits, whole grains, legumes, nuts, seeds and healthy fats (like olive oil and salmon).
Low intake of saturated fats, refined carbohydrates, and processed foods.
This balanced approach reduces systemic inflammation, which is crucial for managing autoimmune conditions like Hashimoto’s.
Gluten-Free Diet: Is It Necessary?
Individuals with Hashimoto’s are more likely to have gluten-related conditions, such as Celiac disease (CD) and non-Celiac gluten sensitivity. Celiac disease, specifically, is the most common autoimmune condition to co-occur with Hashimoto's.
Both conditions share genetic susceptibilities and alterations in gut microbiota. Consuming gluten with these gluten-related conditions can lead to intestinal permeability (leaky gut), triggering systemic inflammation and immune activation against the thyroid.
Key points:
A strict gluten-free diet is essential for individuals with Celiac disease.
For non-Celiac gluten sensitivity or immune responses to gluten, a gluten-free diet is still helpful as it may reduce inflammation, improve gut health, and enhance thyroid function.
Benefits of gluten-free (GF) diet:
Improves absorption of thyroid-supporting nutrients like vitamin D and selenium.
Strengthens gut lining, reducing intestinal permeability and inflammation in the body.
Studies show reduced TSH levels, increased T4 levels, and lower antibody levels in individuals with Hashimoto’s who follow a gluten-free diet, even with diagnosed Celiac disease.
Nutrient considerations:
Opt for gluten-free alternatives that are still whole-foods, as opposed to relying on gluten-free breads, pastas and other processed foods.
Replace gluten-containing foods with those naturally gluten-free, like whole grains, legumes and starchy vegetables.
Lactose-Free Diet: Benefits Beyond Intolerance
Those with lactose intolerance should completely eliminate dairy products given the subsequent dysbiosis that can occur as a result. Up to 70% of individuals are lactose intolerant! Even individuals without lactose intolerance may benefit from dairy elimination, as dairy can be inflammatory.
Key findings:
Eight weeks of lactose elimination improved TSH levels in individuals with Hashimoto’s.
Fermented dairy products (e.g., yogurt, kefir) are better tolerated and support gut health due to their reduced lactose content and probiotic benefits.
Soy-Free Diet: Evaluating the Evidence
High soy intake, often seen in vegetarian diets, may increase the risk of subclinical hypothyroidism progressing to overt hypothyroidism. However, there is limited evidence to suggest complete soy avoidance is necessary for thyroid health. Soy has also been shown to benefit blood pressure, blood sugar, and post-menopausal symptoms.
Key insights:
Be mindful of excess soy intake with subclinical hypothyroidism (abnormal TSH, normal T4 and T3).
Soy does not reduce the efficacy of levothyroxine in post-menopausal women.
Moderate soy intake is unlikely to harm thyroid function and may offer benefits, such as reduced inflammatory markers.
Cruciferous Vegetables: Friend or Foe?
Cruciferous vegetables (e.g., broccoli, kale, cauliflower) have long been avoided in Hashimoto's patients due to concerns about their glucosinolate content, which is thought to interfere with thyroid function. However, research shows that moderate consumption is safe, particularly in the context of adequate iodine intake. Given the other benefits of cruciferous vegetables to liver function, hormone metabolism and reducing future cancer risk, cruciferous vegetables should not be limited in individuals with Hashimoto's.
Highlights:
Cruciferous vegetables should not be limited, and instead eaten regularly.
Cooking cruciferous vegetables reduces glucosinolate activity, making them safer for thyroid health while retaining their nutritional benefits.
Human studies confirm no negative impact on thyroid health with regular consumption.
Iron-Rich Foods: Essential for Thyroid Function
Iron deficiency—the most common global nutrient deficiency—is linked to hypothyroidism and worsened thyroid lab markers. Groups at higher risk include individuals with heavy menstrual periods and pregnant women due to blood loss and higher demands for iron. Vegetarians and those with poor digestion may also be at higher risk due to increased intake and decreased absorption.
Sources of dietary iron:
Animal proteins: Beef, pork, chicken.
Plant-based: Nuts, beans, leafy vegetables, and fortified grains.
If dietary intake is insufficient, iron supplementation may help but should be monitored due to potential side effects like GI upset and constipation.
Fluoride: A Hidden Threat to Thyroid Health
High fluoride exposure is associated with reduced thyroid function. Levels exceeding 2-2.5 mg/L in drinking water may elevate TSH levels, contributing to hypothyroidism. Fluoride levels in water vary in different locations.
Resources:
This CDC website breaks down which areas have fluoridated water, though does not disclose how much.
To determine exact amount, ion-selective electrodes are available that take these measurements.
Low-Carb Diets: Emerging Evidence
Limited research suggests low-carbohydrate diets may improve thyroid antibody levels. However, more studies are needed to confirm these findings.
Important Nutrients and Supplementation for a Hashimoto’s Diet
Optimal thyroid health relies on adequate levels of specific nutrients. Supplementation should address deficiencies without exceeding the body’s needs, as excessive intake offers no added benefits.
Key nutrients:
Vitamin D
Source: Minimal food sources make supplementation often necessary. Small amounts are found in liver, fatty fish, eggs, and milk is often has small amounts of added vitamin D.
Testing: Necessary to ensure proper dosing. Being a fat-soluble vitamins means it builds up in the body, increasing the risk of toxicity if dosed too high.
Function: Adequate levels of vitamin D help reduce thyroid antibodies in Hashimoto's patients.
Selenium:
Sources: Found in Brazil nuts, seafood, and animal proteins.
Testing: Recommended to avoid over-supplementation, as both too little and too much selenium can cause thyroid issues.
Function: Supports thyroid hormone production and reduces thyroid antibodies.
Iodine:
Sources: Sourced from seaweed, seafood, and eggs. Table salt is fortified with iodine, while sea salt has some, though much less, present naturally.
Testing: Recommended if considering supplementation. Deficiency is rare in the U.S., but excess iodine may harm thyroid function.
Function: Iodine is needed to produce thyroid hormone. Too little and too much iodine can result in a goiter (excessive growth of thyroid).
Zinc:
Sources: Highest amount are found in oysters. Also in fish, and whole grains.
Testing: Recommended if considering supplementation.
Function: Involved in the production and metabolism of thyroid hormones. Particularly crucial for non-autoimmune hypothyroidism.
Conclusion
Diet plays an integral role in managing Hashimoto’s thyroiditis by reducing inflammation, supporting gut health, and optimizing nutrient levels. A Mediterranean diet offers a solid foundation, but adding gluten-free or lactose-free options, moderating soy intake, and focusing on key nutrients can further improve thyroid health. Always consult with a healthcare provider for tailored dietary and supplementation advice.
Disclaimer
The information provided in this blog and throughout the website is intended for educational purposes only and should not be considered, or used as a substitute for, medical advice. The content is not meant to diagnose, treat, or cure any medical condition. This blog does not constitute the practice of any medical, nursing or other professional health care advice, diagnosis or treatment. Always consult with a qualified healthcare provider before making any changes to your health regimen or starting new treatments, and never disregard professional medical advice or delay seeking care because of something that you have read on this blog, website or in any linked materials. Your individual needs and circumstances should be evaluated by a medical professional to ensure safe and appropriate care. If you are experiencing a medical emergency, please call 911 or call for emergency medical help on the nearest telephone immediately.
References
Chaudhary, Sandeep, Deep Dutta, Manoj Kumar, Sudipta Saha, Samim Ali Mondal, Ashok Kumar, and Satinath Mukhopadhyay. “Vitamin D Supplementation Reduces Thyroid Peroxidase Antibody Levels in Patients with Autoimmune Thyroid Disease: An Open-Labeled Randomized Controlled Trial.” Indian Journal of Endocrinology and Metabolism 20, no. 3 (2016): 391–98. https://doi.org/10.4103/2230-8210.179997.
Galanty, Agnieszka, Marta Grudzińska, Wojciech Paździora, Piotr Służały, and Paweł Paśko. “Do Brassica Vegetables Affect Thyroid Function?—A Comprehensive Systematic Review.” International Journal of Molecular Sciences 25, no. 7 (April 3, 2024): 3988. https://doi.org/10.3390/ijms25073988.
Huwiler, Valentina V., Stephanie Maissen-Abgottspon, Zeno Stanga, Stefan Mühlebach, Roman Trepp, Lia Bally, and Arjola Bano. “Selenium Supplementation in Patients with Hashimoto Thyroiditis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials.” Thyroid 34, no. 3 (March 1, 2024): 295–313. https://doi.org/10.1089/thy.2023.0556.
Iamandii, Inga, Lisa De Pasquale, Maria Edvige Giannone, Federica Veneri, Luigi Generali, Ugo Consolo, Linda S. Birnbaum, et al. “Does Fluoride Exposure Affect Thyroid Function? A Systematic Review and Dose-Response Meta-Analysis.” Environmental Research 242 (February 1, 2024): 117759. https://doi.org/10.1016/j.envres.2023.117759.
Luo, Jingyi, Xiaoxia Wang, Li Yuan, and Lixin Guo. “Iron Deficiency, a Risk Factor of Thyroid Disorders in Reproductive-Age and Pregnant Women: A Systematic Review and Meta-Analysis.” Frontiers in Endocrinology 12 (February 25, 2021): 629831. https://doi.org/10.3389/fendo.2021.629831.
Object, object. “The Effect of Soy Phytoestrogen Supplementation on Thyroid Status and Cardiovascular Risk Markers in Patients with Subclinical Hypothyroidism: A Randomized, Double-Blind, Crossover Study.” Accessed December 26, 2024. https://core.ac.uk/reader/151162672?utm_source=linkout.
“Office of Dietary Supplements - Iodine.” Accessed January 7, 2025. https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/.
“Office of Dietary Supplements - Iron.” Accessed January 7, 2025. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/.
“Office of Dietary Supplements - Selenium.” Accessed January 7, 2025. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/.
“Office of Dietary Supplements - Vitamin D.” Accessed January 7, 2025. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.
“Office of Dietary Supplements - Zinc.” Accessed January 7, 2025. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/.
Osowiecka, Karolina, and Joanna Myszkowska-Ryciak. “The Influence of Nutritional Intervention in the Treatment of Hashimoto’s Thyroiditis—A Systematic Review.” Nutrients 15, no. 4 (February 20, 2023): 1041. https://doi.org/10.3390/nu15041041.
Persiani, S., F. Sala, C. Manzotti, M. Colovic, M. Zangarini, Y. Donazzolo, B. Barbetta, et al. “Evaluation of Levothyroxine Bioavailability after Oral Administration of a Fixed Combination of Soy Isoflavones in Post-Menopausal Female Volunteers.” Drug Research 66, no. 3 (March 2016): 136–40. https://doi.org/10.1055/s-0035-1555784.
Piticchio, Tommaso, Francesco Frasca, Pasqualino Malandrino, Pierpaolo Trimboli, Nunzia Carrubba, Andrea Tumminia, Federica Vinciguerra, and Lucia Frittitta. “Effect of Gluten-Free Diet on Autoimmune Thyroiditis Progression in Patients with No Symptoms or Histology of Celiac Disease: A Meta-Analysis.” Frontiers in Endocrinology 14 (July 24, 2023): 1200372. https://doi.org/10.3389/fendo.2023.1200372.
Pobłocki, Jakub, Tamara Pańka, Małgorzata Szczuko, Arkadiusz Telesiński, and Anhelli Syrenicz. “Whether a Gluten-Free Diet Should Be Recommended in Chronic Autoimmune Thyroiditis or Not?—A 12-Month Follow-Up.” Journal of Clinical Medicine 10, no. 15 (July 22, 2021): 3240. https://doi.org/10.3390/jcm10153240.
Talebi, Sepide, Ehsan Ghaedi, Erfan Sadeghi, Hamed Mohammadi, Amir Hadi, Cain C. T. Clark, and Gholamreza Askari. “Trace Element Status and Hypothyroidism: A Systematic Review and Meta-Analysis.” Biological Trace Element Research 197, no. 1 (September 2020): 1–14. https://doi.org/10.1007/s12011-019-01963-5.
Verma, Anjali, Kusum Lata, Alok Khanna, Raj Singh, Ashuma Sachdeva, Prateek Jindal, and Swati Yadav. “Study of Effect of Gluten-Free Diet on Vitamin D Levels and Bone Mineral Density in Celiac Disease Patients.” Journal of Family Medicine and Primary Care 11, no. 2 (February 2022): 603–7. https://doi.org/10.4103/jfmpc.jfmpc_1190_21.
Zhang, Jingwen, Yuting Chen, Hongyan Li, and Hong Li. “Effects of Vitamin D on Thyroid Autoimmunity Markers in Hashimoto’s Thyroiditis: Systematic Review and Meta-Analysis.” The Journal of International Medical Research 49, no. 12 (December 6, 2021): 03000605211060675. https://doi.org/10.1177/03000605211060675.