Quick answer: Your thyroid needs specific nutrients to make and activate its hormones: iodine to build them, selenium and zinc to convert T4 into active T3, iron for the enzyme that makes thyroid hormone, and vitamin D for immune balance. Balance matters: too little or too much iodine or selenium can cause problems, especially in Hashimoto’s, so testing and guidance help.
Key takeaways
The thyroid relies on iodine to build its hormones and on selenium and zinc to convert T4 into active T3.
Iron is needed for the enzyme that makes thyroid hormone, and vitamin D supports immune balance.
Balance matters, because too little or too much iodine or selenium can cause problems, especially with Hashimoto’s.
For the bigger picture of thyroid root causes, see natural remedies for thyroid issues. This guide focuses on nutrients.
The nutrients your thyroid needs
Iodine is the raw material for thyroid hormone, and both too little and too much can cause problems. Selenium is needed to convert T4 to T3 and protect the gland (see who should consider selenium), and iron is needed for thyroid peroxidase, the enzyme that makes hormone (see who should consider iron).
Zinc, balanced with copper, supports hormone production and receptor function. For vitamin D, low levels are linked with autoimmune thyroid disease. Vitamin A and B vitamins support hormone transport and activity, and myo-inositol has been studied together with selenium in Hashimoto’s.
Herbs sometimes used
Ashwagandha may raise thyroid hormone levels, so it is not for hyperthyroidism. Guggul is a traditional thyroid herb that interacts with medications. Seaweeds such as kelp and bladderwrack contain variable, sometimes high iodine, so use them only with guidance. Omega-3s and curcumin support a healthy inflammatory response.
Amounts should be individualized.
Daily habits that support the thyroid
Consider a trial off gluten if you have Hashimoto’s, after celiac testing, and enjoy cruciferous vegetables, cooked if you eat a lot of them. Filter your drinking water, sleep before 11 pm when possible, and manage stress.
Is testing helpful?
A full thyroid panel (TSH, free T4, free T3, reverse T3 and antibodies) and iron studies help guide nutrient choices (see reverse T3). Functional labs are optional. They can be helpful in more complex cases.
The thyroid and healthy aging
Active thyroid hormone (T3) helps set how efficiently mitochondria make energy and supports cell renewal and repair. When the thyroid is underactive or under immune attack, energy production slows and inflammation rises, both processes linked with aging.
Safety
According to the NIH Office of Dietary Supplements, the upper limit for selenium is 400 mcg a day for adults. Iodine supplements can worsen some thyroid conditions, including Hashimoto’s and hyperthyroidism. Thyroid medication should be taken apart from iron, calcium and soy. Never change thyroid medication without your prescriber.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have thyroid symptoms despite “normal” labs, or if you have Hashimoto’s or a family history of thyroid disease. The same is true if you are unsure whether you need iodine or selenium, or if you take thyroid medication and want to add nutrients safely.
See a medical provider promptly for a rapidly enlarging neck lump, trouble swallowing or breathing, or a racing heartbeat with weight loss and tremor.
What the research shows
Selenium has the most thyroid research. A 2010 meta-analysis by Toulis and colleagues of blinded trials in people with Hashimoto’s thyroiditis on levothyroxine found that three months of selenium significantly lowered TPO antibodies and made people more likely to report better well-being. Thyroid function and medication needs were not clearly changed.
Ashwagandha has a small thyroid trial. In a 2018 study by Sharma and colleagues, 50 adults with mildly elevated TSH (4.5 to 10) took 600 mg of ashwagandha root extract or a placebo for eight weeks, and TSH, T3 and T4 levels improved significantly compared with placebo. It was a short, single-center pilot study, and ashwagandha can raise thyroid hormone levels, so people already on thyroid medicine should not add it without their prescriber.
Want a thyroid nutrient plan matched to your labs?
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Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Should we check my iodine, selenium, iron and vitamin D before I take any thyroid nutrients?
Which thyroid nutrients might I be low in, based on my diet and labs?
Should we check my iron, selenium or vitamin D as part of my thyroid picture?
Could too much iodine or selenium be a concern for me?
Frequently asked questions
Should I take iodine for my thyroid?
Only if you are low. Too much iodine can worsen Hashimoto’s and other thyroid conditions.
What foods support the thyroid?
Seafood, eggs, Brazil nuts in small amounts, legumes, and colorful vegetables provide key nutrients.
Does iron affect thyroid function?
Yes. Iron is needed to make thyroid hormone, and low iron is common in people with hypothyroidism.
Can I take supplements with thyroid medication?
Some, such as iron and calcium, block absorption. Take them at least four hours apart and ask your provider.
Sources
- Toulis KA, Anastasilakis AD, Tzellos TG, et al. Selenium supplementation in the treatment of Hashimoto's thyroiditis: a systematic review and a meta-analysis. Thyroid 2010. PMID: 20883174. https://pubmed.ncbi.nlm.nih.gov/20883174/
- Sharma AK, Basu I, Singh S. Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial. J Altern Complement Med 2018. PMID: 28829155. https://pubmed.ncbi.nlm.nih.gov/28829155/
- Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol 2014. PMID: 24342882. https://pmc.ncbi.nlm.nih.gov/articles/PMC3976240/
- Ventura M, Melo M, Carrilho F. Selenium and Thyroid Disease: From Pathophysiology to Treatment. Int J Endocrinol 2017. PMID: 28255299. https://pmc.ncbi.nlm.nih.gov/articles/PMC5307254/
- Zimmermann MB, Köhrle J. The impact of iron and selenium deficiencies on iodine and thyroid metabolism: biochemistry and relevance to public health. Thyroid 2002. PMID: 12487769. https://pubmed.ncbi.nlm.nih.gov/12487769/
- Wang J, et al. Meta-analysis of the association between vitamin D and autoimmune thyroid disease. Nutrients 2015. PMID: 25854833. https://pmc.ncbi.nlm.nih.gov/articles/PMC4425156/
- NIH Office of Dietary Supplements: Selenium (Consumer Fact Sheet)
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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