Quick answer: Selenium is on my short list if you have thyroid concerns (especially Hashimoto’s patterns), eat few Brazil nuts or seafood, have brittle hair and nails, or have a family history of thyroid autoimmunity. Selenium is built into enzymes that protect the thyroid while it makes hormone. A little goes a long way: as few as one or two Brazil nuts can meet a day’s need for some people, and too much is harmful.
Key takeaways
Selenium protects the thyroid gland from the oxidative stress created when it makes thyroid hormone.
It may be worth considering for people with thyroid concerns, especially autoimmune patterns, and for those who eat few Brazil nuts or seafood.
More is not better with selenium, since the range between helpful and excessive intake is narrow.
Who should consider selenium?
Selenium may be worth considering for people with thyroid concerns, especially Hashimoto’s or positive thyroid antibodies, and for anyone with a family history of thyroid autoimmunity. It may also fit people who rarely eat seafood, eggs or Brazil nuts, and those living in regions with low-selenium soil.
People with brittle hair and nails may consider it too, as may men with fertility concerns.
Why selenium matters for the thyroid
Making thyroid hormone creates oxidative stress inside the gland. Selenium is built into glutathione peroxidase and other enzymes that neutralize that stress, and it is needed to convert T4 into active T3. Thyroid support is rarely just iodine. Selenium, iron, zinc and tyrosine all matter. I never treat the thyroid as an island: conversion of T4 to T3, antibody activity, and oxidative load around the gland all have nutrient requirements. Learn more in anti-TPO antibodies explained and thyroid health support.
Selenium beyond the thyroid
Selenium also supports a healthy inflammatory balance, immune function and sperm quality. Its antioxidant enzymes help protect cells and DNA from oxidative damage, one of the slow, everyday stresses that contributes to aging.
How much selenium is safe?
According to the NIH Office of Dietary Supplements, the recommended intake for adults is 55 mcg a day, and the upper limit is 400 mcg a day from all sources. Brazil nuts vary a lot in selenium content, so eating several every day can push you over the limit. Signs of too much include a garlic odor on the breath, a metallic taste, hair and nail loss or brittleness, and skin rashes. Discuss selenium with your provider, especially if you already take a multivitamin or thyroid formula that contains it.
If you work with me, the selenium and thyroid products I use are in my Fullscript dispensary. Related: natural remedies for thyroid issues.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have Hashimoto’s, positive thyroid antibodies or a family history of them, or if you have thyroid symptoms despite a “normal” TSH. The same is true if you want to know whether your multivitamin plus diet gives you too little or too much selenium, or if you are planning a pregnancy and have thyroid concerns.
See a medical provider promptly for a rapidly enlarging neck lump, trouble swallowing or breathing, or a fast or irregular heartbeat.
Thyroid concerns? Let us look at the whole picture, not just TSH.
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Would selenium make sense for my thyroid, given how much I already get from food?
Could selenium interact with any of my current medications or other supplements?
Would any labs or health history details help us decide whether selenium makes sense for me?
How would we tell whether selenium is a good fit for me, and when should we check in again?
Practitioner-grade options in my Fullscript catalog: if you and your clinician decide a supplement makes sense, my supplement guide by health goal links to the practitioner-grade products I trust.
Frequently asked questions
How many Brazil nuts should I eat for selenium?
Selenium content varies widely between nuts. For some people one or two a day is plenty. Eating many daily can exceed the upper limit.
Does selenium help Hashimoto’s?
Some studies show selenium may lower thyroid antibodies in some people, but results are mixed. It should be used as part of a plan with your provider.
What are signs of too much selenium?
Garlic-smelling breath, a metallic taste, brittle or falling-out hair and nails, skin rash, fatigue and irritability.
Can I get selenium from food?
Yes. Brazil nuts, seafood, eggs, poultry and whole grains are good sources, though the amount in plants depends on the soil.
Sources
- 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/
- Rayman MP. Selenium and human health. Lancet 2012. PMID: 22381456. https://pubmed.ncbi.nlm.nih.gov/22381456/
- Toulis KA, 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/
- Wichman J, et al. Selenium Supplementation Significantly Reduces Thyroid Autoantibody Levels in Patients with Chronic Autoimmune Thyroiditis. Thyroid 2016. PMID: 27702392. https://pubmed.ncbi.nlm.nih.gov/27702392/
- NIH Office of Dietary Supplements: Selenium (Consumer Fact Sheet)
- NIDDK: Hashimoto’s Disease
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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