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Selenium has been associated with positive health outcomes. Here’s what you need to know.

Selenium is a mineral that appears naturally in soil, water, and some foods. Ongoing research has suggested that it can have positive effects on your health as it boosts immunity and staves off cancer, cardiovascular disease, thyroid problems, cognitive decline, infertility, and asthma. If it’s new to you, or you’re just looking for more information, here are some things you should know.

Daily dietary allowances

Whether you get it through a supplement or by eating certain foods that we’ll identify below, here are the recommended daily dietary allowances for selenium:

  • Children aged 1-3 – 20 micrograms daily
  • Children aged 4-8 – 30 micrograms daily
  • Children aged 9-13 – 40 micrograms daily
  • Adults and children over 14 – 55 micrograms daily
  • Pregnant women – 60 micrograms daily
  • Breastfeeding women – 70 micrograms daily

An overdose from consuming selenium in food is unlikely but one is more possible when taking selenium in supplements.

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Natural food sources

You can consume selenium via supplement, but can also find it in the following foods:

  • nuts, such as Brazil nuts and walnuts
  • fresh and saltwater fish, such as tuna, cod, red snapper, and herring
  • beef and poultry (and eggs)
  • whole grains, including brown rice

Selenium and testosterone

Studies published in the British Journal of Urology, Biological Trace Element Research, and Journal of Veterinary Research indicate that taking selenium supplements may increase testosterone levels and enhance male fertility.

Specifically, one 26-week study involving 468 men with infertility who took 200 mcg of selenium together with N-acetyl-cysteine daily showed increased testosterone production, sperm count, and sperm quality. In addition, a second study involving 690 men with infertility who took 200 mcg of selenium together with 400 units of Vitamin E showed improved sperm motility and appearance in 53% of participants after just 100 days. Eleven percent of the men in that study got their partners pregnant.

Brazil nuts

Brazil nuts have also been linked with boosted testosterone levels as a result their high levels of naturally occurring selenium. Just one 28-gram serving of Brazil nuts provide 988% of the daily recommended dietary allowance of selenium.

Brazil nuts offer all kinds of positive health effects: boosts to antioxidants; support of thyroid function; they’re high in heart-healthy polyunsaturated fats; they have protective effects on the brain and mood-elevating properties; they may decrease blood sugar levels and improve insulin sensitivity; and reduced inflammation.


Researchers at Virginia Polytechnic Institute and State University, Virginia-Maryland College of Veterinary Medicine, University of South Dakota, and Texas A&M Univesity have experimented with supplementing the diets of farmed Nile tilapia with organic and non-organic selenium.

As it turns out, supplementing the fish’s diet with organic selenium helps maintain their health. It also produced fish with higher concentrations of the beneficial mineral to be consumed by people. It’s a potential win-win and a big deal, since aquaculture has shown the capacity to help respond to worldwide malnutrition.

Ongoing research has suggested that selenium can have positive effects on or help prevent immune health, cancer, cardiovascular disease, thyroid problems, cognitive decline, infertility, and asthma.

The downside

If you stay within those recommended daily dietary allowances, you should experience no negative side effects from selenium consumption. Going beyond recommended doses, however can be a problem. These are some signs of selenium toxicity:

  • garlic-y breach and a metallic taste in your mouth
  • brittle nails
  • tooth decay
  • nausea and gastrointestinal issues
  • neurological problems
  • fatigue and irritability
  • skin lesions and rashes
  • hair loss

Selenium can interact with other medicines and supplements, so you should always keep in mind what else you’re consuming to avoid any negative complications. Things that Selenium can interact with include antacids, chemotherapy drugs, corticosteroids, niacin, statins to lower cholesterol, and birth control pills.

There have been studies indicating a relationship between Selenium supplements and an increased risk of squamous cell carcinoma (skin cancer). If you’re already at high risk of developing skin cancer, avoid taking Selenium supplements.

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