What Does Selenium Do in the Human Body?

Selenium: heard of it? If you’re part of dieting, wellness, or “bio-hacking” circles, this nutrient has probably popped up from time to time.

What’s crazy about selenium: its role in health (and what it does in the human body) is only now starting to be understood. Some are scrambling to make sure they get enough. Still, the what, how, and why of selenium feels relatively new and unknown to some.

What is Selenium?

Selenium is a trace mineral. Our body needs some, but not a lot, to function.

Because there isn’t a lot in most foods we eat (and the body’s requirements are low), selenium has been greatly underestimated over the decades. However, research shows it’s important in more ways than we ever knew.

We need selenium for healthy thyroid function.* It’s also vital to reproductive, heart, immune, and cognitive health.* Selenium appears to play essential roles in balancing inflammation, repelling free radicals, preventing cancer, and supporting hormone production too (especially thyroid hormone).* Along with another mineral, iodine, the thyroid couldn’t function without selenium.*

Symptoms of selenium deficiency can be hard to detect. Thyroid problems, iodine deficiency, infertility, immune issues, and frequent illness are common signs.

So, How Much Selenium Do You Need?

You need around 40-50 mcg of selenium per day, experts say. Fortunately, most people get enough selenium naturally—if they eat a healthy, varied diet.

Since getting selenium from food depends on its presence in soils (and thus in crops we eat or that meat animals eat), people in selenium-poor areas may not get enough. People who eat less meat may be at risk, too, since it’s most plentiful in animal foods.

Best Whole Food Sources of Selenium

Can you lean on whole food sources for selenium? Or do you have to take a supplement? We’ll go through these best whole food sources and find out.

#1: Seafood

The National Institutes of Health show that seafood, especially fish, is the best selenium source. You need 1-2 servings per day of foods like tuna, halibut, shrimp, or sardines to get your needs.

What if you’re vegan or vegetarian? Or, don’t have access to whole and sustainably sourced seafood? What about allergies? Don’t worry, there’s other sources.

#2: Organ Meats

Those with seafood/shellfish allergens can try organ meats. Research suggests they’re the next plentiful source, including liver, kidneys, even brain.

According to SELF Nutrition Data, 2-3 servings cooked beef liver per day covers all your daily selenium. Not all people like organ meats, though. Most don’t buy and eat them often, and vegetarians and vegans can’t eat them, either.

#3: Brazil Nuts

Brazil nuts contain more selenium than seafood or organ meats, and plant eaters can enjoy them.

The rub: selenium in Brazil nuts is unpredictable. A single Brazil nut can have MORE than your daily needs (68-91 mcg). This may cause  selenium toxicity symptoms over time— carefully eating 1-3 per day is safest.

#4: Beef

Don’t have a beef with beef? Give beef a try. It contains about half your daily selenium, so you’ll need to eat a couple servings.

Vegetarians and vegans do have a beef with beef, though. And some people with dietary restrictions can’t eat beef— they’ll need other sources.

#5. Turkey

Turkey is “up there” on the list of selenium rich whole food sources. Like beef, you’ll need 2-3 servings a day (but at least you’ve got a leaner option).

Again, this source is barred to vegans and vegetarians. Though it’s “healthier” meat, sourcing it ethically and sustainably (which ensures more nutrients like selenium) may prove challenging and expensive.

#6: Chicken

Poultry in general seems to be high in selenium. To get your daily value from chicken specifically though, you’d need 3-4 servings per day.

Chicken is also leaner, healthier, and more widely available. Organic and ethically raised chicken— which is more nutrient dense— is also easier to come by. Still, it’s not a good option for plant eaters.

#7: Eggs

Which comes first: the chicken or the egg? In terms of selenium, chickens come first, but eggs aren’t too far behind.

You’d have to eat about 5 eggs per day to keep up on your selenium requirements, though. Vegetarians, not vegans, can give this a try— though that’s about 2-3 omelets per day.

#8: Vegetables

It’s not all about animal products (or Brazil nuts). Vegetables, too, can provide some of your daily selenium. Still, you’d have to eat a lot of them, and only certain produce are notable sources.

Some good examples: spinach, green peas, beans, and potatoes. Vegans and vegetarians can take advantage of this. But, with vegetables alone, you’d come nowhere close to hitting the mark for your daily needs.

#9: Fortified Foods

There are always fortified foods to consider. Cereals, dairy, milk, and milk alternatives often come fortified with trace minerals like selenium. These can be helpful to both meat and plant eaters alike.

People who seek selenium through whole foods may run into a few obstacles, however. They’ll have to eat lots of specific foods to keep up. Or, they may be limited to relying on difficult-to-source foods. Eaters with sustainability/ethical standards may have the hardest time of all.

Yes, you can always try standard selenium supplements.

OR…. try our powder supplements from Root’d. (Link Here)

Our supplements are made just like certified organic whole foods are grown (or raised). They’re good for the environment, contain no additives or animal products, and are tested for purity and quality.

They’re just like a whole food, but as easy to take as a supplement (and they taste great).

Best of all: our supplements contain a little under your daily recommended selenium. That way, you can get other selenium from foods as much (or as little) as you want, without worrying about toxicity.


Professor Margaret P. Rayman (2012). Selenium and human health. The Lancet 379(9822) 1256-1268. Retrieved from

Fiona M. Fordyce (2012). Selenium Deficiency and Toxicity in the Environment. Essentials of Medical Geology pp. 375-416. Retrieved from

Office of Dietary Supplements (Updated 2019). Selenium: Fact Sheet for Health Professionals. National Institutes of Health – U.S. Department of Health and Human Services. Retrieved from

SELF Nutrition Data.

Jennifer K. MacFarquhar, Dr. Danielle L. Broussard, et. al. (2011). Acute Selenium Toxicity Associated With a Dietary Supplement. Archives of Internal Medicine 170(3) 256-261. Retrieved from

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