Selenium is an essential nutrient. But what exactly is it?

The global supplement market reached more than $485 billion in 2024, and some six in 10 adults are taking at least one dietary supplement a month, according to the U.S. Centers for Disease Control and Prevention.

Vitamin D, magnesium, fish oil, vitamin C and zinc continue to be among the most popular supplements today, but the mineral selenium is also climbing in popularity.

Here's what selenium is, what benefits it provides and the dangers of taking too much.

What is selenium?

Selenium is a nutrient that is naturally present in many foods, added to others and is also available as a dietary supplement in pill, powder and liquid form, explains Perri Halperin, a nutritional scientist, registered dietitian and founder of All the Nutrition. It's considered an essential trace mineral because the body only needs a small amount of it for optimal health but doesn't produce it.

The foods that naturally contain selenium include seafood such as shrimp, cod and tuna; red meat like pork chops, ham and beef steak; and eggs and dairy products such as cottage cheese, yogurt and milk. Oatmeal, mushrooms, pasta noodles, beans, spinach, bananas and whole-wheat bread also contain the mineral.

While most of us get enough selenium as part of a healthy diet, "people with specific health conditions such as Crohn’s disease, severe gastrointestinal disorders or those living in regions with selenium-deficient soils may be at higher risk of selenium deficiency and could benefit from supplementation under medical supervision," says Amy Goodson, a nutritionist and registered dietitian at The Sports Nutrition Playbook.

Is selenium good for you? What does selenium do for the body?

Selenium plays important roles in hormone function, a healthy metabolism, DNA synthesis and protection from oxidative damage and infection, notes the U.S. National Institutes of Health (NIH) Office of Dietary Supplements.

Because of this, selenium contained in food or supplements can be helpful in boosting your immune system, regulating your hormones and protecting your cells from damage, says Goodson. "It can also reduce the risk of certain chronic diseases, including heart disease and some cancers," she explains, "and can contribute to slowing the aging process and improving skin health."

Vanessa Rissetto, a New Jersey-based registered dietitian at Culina Health, says the mineral can also help with reproductive health because the mineral's impact on hormones improves a woman's menstrual cycle and because it helps men develop healthy and motile sperm.

Selenium has also been associated with reducing your risk of Alzheimer's disease, improving cognitive function and decreasing symptoms related to asthma.

Can you take selenium every day?

Despite so many benefits, it's important to keep your selenium intake within the recommended levels of consumption. That's 55 micrograms daily for people 14 years and older, per the NIH; "but you'll need slightly more if pregnant or breastfeeding," says Halperin.

While you should shoot to keep your selenium intake within these recommendations, the daily upper limit before reaching toxicity levels is much higher. Taking into consideration all food and drink sources that contain selenium, plus any supplements, adults should not take more than 400 micrograms daily.

Exceeding that amount can lead to toxicity and related side effects such as "hair loss, joint pain, brittle nails and hair, skin rash, nausea, diarrhea, fatigue, breathing problems and even kidney failure," says Rissetto.

You're unlikely to reach toxic levels from food consumption alone though, with the exception of eating too many Brazil nuts. A single ounce containing six to eight Brazil nuts packs a whopping 544 micrograms of selenium. Because of this, "it's not recommended to eat more than three to five Brazil nuts a day," says Goodson.

Other examples of foods that will get you to your daily recommended intake of selenium include cooked shrimp (42 micrograms in three ounces), spaghetti noodles (33 micrograms in one cup), turkey meat (26 micrograms in three ounces) and hard-boiled eggs (15 micrograms in one large egg).

This article originally appeared on USA TODAY: What is selenium?