Selenium: A Mineral Your Body Needs—And How to Get Enough

You've probably heard of calcium for bones and iron for energy. But there's a lesser-known mineral quietly working in nearly every cell of your body: selenium. Despite its importance, most people barely know what it does—or whether they're getting enough. Here's what doctors and nutritionists want you to understand about this often-overlooked nutrient.

What Is Selenium, and Why Does Your Body Need It?

Selenium is a trace mineral, meaning your body only needs small amounts, but those amounts matter enormously. It's a core component of selenoproteins—special proteins your body uses to manage inflammation, support immune function, and protect cells from damage.

Think of selenium as a cleanup crew. Your cells constantly produce free radicals during normal metabolism. These unstable molecules can damage healthy tissue if left unchecked. Selenoproteins, particularly one called glutathione peroxidase, help neutralize those free radicals before they cause harm. Without adequate selenium, your body struggles to run this protective system efficiently.

Beyond antioxidant defense, selenium plays roles in:

• Thyroid hormone metabolism — Your thyroid depends on selenium to convert thyroid hormones into forms your body can use
• DNA synthesis and repair — Cells need selenium to build and maintain genetic material
• Reproductive health — Both men and women require selenium for fertility
• Cognitive function — Some research suggests selenium supports brain health as we age

How Much Selenium Do You Actually Need?

The recommended daily allowance (RDA) is modest: 55 micrograms per day for adults. Most healthy people in developed countries meet this target without much effort, though some populations fall short.

That said, "meeting the minimum" isn't the same as "thriving." The range between deficiency and excess is fairly wide with selenium, which makes it relatively forgiving as nutrients go. You'd need to consistently consume far more than typical food sources provide to risk toxicity.

Where Selenium Comes From

Food is your primary source of selenium, and the mineral's concentration varies dramatically based on soil content.

Common selenium-rich foods include:

The tricky part: selenium content in plant foods depends entirely on whether the soil where they grew contains selenium. A tomato grown in selenium-rich soil contains far more than one grown in depleted soil. For this reason, geographic variation is real. People in regions with selenium-poor soil may need to be more intentional about their sources.

Animal products offer more consistency because animals are often fed supplemented feed, which stabilizes their selenium intake.

Who Might Not Get Enough Selenium?

Most people in developed countries consume adequate selenium. But certain groups face higher risk of deficiency:

People with digestive disorders — Conditions like Crohn's disease or celiac disease affect nutrient absorption. Those with significant gut issues should discuss selenium status with their doctor.

Individuals on restrictive diets — Vegans or vegetarians who avoid most plant sources from depleted soils, or those following very limited eating patterns, may fall short.

Residents in low-selenium regions — Certain geographic areas have genuinely depleted soil. This is more common globally than in the United States, but pockets exist everywhere.

People undergoing dialysis — Kidney disease and dialysis treatment affect mineral balance and nutrient retention.

Signs You Might Be Deficient

Severe selenium deficiency is rare in developed nations, but mild deficiency does occur. Warning signs can be subtle and overlap with other conditions:

• Fatigue and general weakness
• Muscle pain or weakness
• Mood changes or brain fog
• Hair loss or weak nails
• Recurring infections (suggesting immune strain)
• Thyroid problems

If you're experiencing these symptoms, the issue could stem from many causes. That's why testing matters. A simple blood test can measure selenium levels, though it's not routine screening. Bring it up with your doctor if you suspect a deficiency.

What About Supplements?

Selenium supplements exist, but most healthy people don't need them. If your diet includes seafood, poultry, eggs, or whole grains—especially from varied geographic sources—you're likely meeting your needs.

Supplementation makes sense if:

• Blood tests confirm low selenium levels
• You have a diagnosed digestive condition that impairs nutrient absorption
• Your doctor recommends it as part of thyroid management

Taking random supplements without evidence of deficiency isn't harmful in selenium's case (the safety window is wide), but it's also unnecessary for most people.

The Practical Takeaway

Selenium isn't glamorous, and you won't feel it working. But that's precisely why it matters—it does its job quietly in the background, supporting thyroid function, immune response, and cellular repair.

You don't need to obsess over selenium intake. A varied diet that includes protein sources like fish or poultry, a few eggs, and whole grains covers your bases for most people. Brazil nuts are an efficient option if you enjoy them, though they're not required.

If you fall into a higher-risk category—digestive disease, restricted diet, thyroid issues—make selenium part of the conversation with your healthcare provider. A quick blood test answers the question definitively, and from there, you can decide whether food sources alone are sufficient or whether supplementation makes sense.

That's how you approach nutrients sensibly: not with fear or obsession, but with informed awareness and action when evidence warrants it.