How Selenium Supports Your Thyroid
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Selenium might not be as famous as calcium or iron, but this small nutrient plays a big role in keeping your thyroid healthy. Your thyroid is a butterfly-shaped gland in your neck that controls metabolism, growth, and energy levels. And without enough selenium, it may not work properly.
This article explains why selenium matters for thyroid health and how to make sure you're getting the right amount—no more, no less.
What Is Selenium?
Selenium is a trace mineral, which means you only need a small amount of it. Even so, it's essential for many body functions. Selenium helps create special proteins called selenoproteins, which protect your cells from damage and support your immune system.
For the thyroid, selenium is extra important. It helps convert the thyroid hormone T4 (thyroxine) into its active form T3 (triiodothyronine), which your body uses to regulate metabolism. It also helps protect the thyroid gland from oxidative stress—a kind of cell damage that happens when harmful molecules (called free radicals) build up.
Why Is Selenium Important for the Thyroid?
Your thyroid contains more selenium per gram than any other organ. That’s because it relies heavily on selenium-dependent enzymes for two key jobs:
- Making thyroid hormones work properly
- Protecting thyroid cells from damage
When your body doesn’t get enough selenium:
- It may struggle to convert T4 into active T3
- You could develop symptoms of low thyroid (fatigue, weight gain, cold sensitivity)
- Your immune system might attack your thyroid, leading to autoimmune diseases like Hashimoto’s thyroiditis or Graves’ disease
What Happens If You're Low on Selenium?
Research, including the 2025 study published in the journal Biological Trace Element Research, shows that selenium deficiency can cause several thyroid-related problems, such as:
- Hypothyroidism (underactive thyroid): Your body doesn’t produce enough active thyroid hormone.
- Hashimoto’s thyroiditis: An autoimmune disease where your immune system attacks the thyroid.
- Graves’ disease: An autoimmune disease that causes overactive thyroid and may lead to eye problems.
- Goiter: Swelling of the thyroid gland due to hormonal imbalance or lack of nutrients.
The study also explains that low selenium levels increase oxidative stress in the thyroid, causing inflammation and damage over time.
Can Selenium Supplements Help?
Yes, but with caution. Clinical studies have shown that selenium supplements can:
- Lower thyroid antibody levels in autoimmune diseases
- Improve quality of life in people with thyroid disorders
- Support better thyroid hormone balance in people with subclinical hypothyroidism
However, more selenium isn’t always better. The recommended daily amount is about 55 micrograms (µg) for adults. During pregnancy or breastfeeding, it goes up slightly. The upper safe limit is 400 µg/day. Taking more than that can cause side effects like stomach issues, hair loss, and nerve problems.
How to Get Enough Selenium Naturally
You can usually get enough selenium from food without needing a supplement. Good sources include:
- Brazil nuts (very high—just 1–2 per day is enough!)
- Fish and shellfish
- Eggs
- Chicken and turkey
- Whole grains
If you’re vegan or live in areas where the soil is low in selenium (like parts of Europe and Asia), you may be more at risk of deficiency.
What Should You Do?
1. Don’t self-prescribe supplements
Always talk to a doctor before starting selenium supplements, especially if you already have thyroid problems.
2. Ask for a selenium test
A blood test can check your selenium status and guide whether you need extra support.
3. Combine with other nutrients
Selenium works best when your body also has enough iodine, zinc, iron, and vitamin D—all of which support thyroid function.
Final Thoughts
Selenium might be a small nutrient, but it has a mighty impact on your thyroid. From helping your body make active thyroid hormones to protecting your gland from damage, selenium is a quiet but crucial helper. Making sure you have enough—without going overboard—can make a big difference in your energy, metabolism, and overall well-being.