Selenium for Health: Benefits, Sources, and What You Need to Know

When it comes to selenium, a trace mineral essential for thyroid function, immune response, and protecting cells from damage. Also known as Se, it doesn’t get much attention—but your body can’t run without it. Unlike vitamins you can overdose on, selenium works in tiny amounts. Too little? You might feel tired, get sick more often, or struggle with thyroid issues. Too much? It can turn toxic. The line between helpful and harmful is narrow, and most people don’t know where they stand.

Selenium is a key player in your thyroid, a gland that controls metabolism, energy, and body temperature. About 50% of the selenium in your body sits in your thyroid, helping convert inactive thyroid hormone (T4) into the active form (T3). If you have Hashimoto’s or another autoimmune thyroid condition, studies show selenium supplements can lower antibody levels and ease inflammation—especially when taken as selenomethionine. But it’s not a magic fix. It works best alongside proper medical care.

It also powers your antioxidant system, your body’s natural defense against oxidative stress. Selenium is part of glutathione peroxidase, an enzyme that neutralizes free radicals. Without enough, your cells age faster, inflammation rises, and your risk for chronic diseases goes up. That’s why it’s often paired with vitamin E in supplements—it’s a team effort.

Most people get enough selenium from food. Brazil nuts are the superstar—just one nut can give you your daily dose. Other sources include seafood like tuna and sardines, eggs, chicken, and whole grains. But if you live in a region with low-selenium soil (like parts of Europe or China), your food might not have enough. Vegans and people with digestive disorders like Crohn’s are also at higher risk for deficiency.

Don’t rush to take a supplement. The safe upper limit is 400 micrograms a day. One Brazil nut has 68–91 mcg. A multivitamin might add another 55 mcg. Stack them up, and you’re already near the edge. Symptoms of too much selenium include hair loss, brittle nails, garlic breath, and nerve pain. It’s not worth guessing.

What you’ll find in the articles below are real, practical guides on how selenium connects to everyday health issues: from thyroid support and immune strength to how it interacts with other supplements and medications. You’ll see how it plays a role in chronic conditions, what the science really says about supplements, and how to avoid common mistakes. No fluff. Just what works—and what doesn’t—based on actual patient experiences and clinical data.