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What Does Selenium Do to Your Body? A Dietitian Explains the Evidence

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RDAs for Selenium
Age (years) Male Female
18 to 51+ 55 mcg 55 mcg
14 to 17 55 mcg 55 mcg
9 to 13 40 mcg 40 mcg
4 to 8 30 mcg 30 mcg
1 to 3 20 mcg 20 mcg

Selenium needs are higher during pregnancy and lactation (breastfeeding).

Pregnant people need 60 mcg of selenium per day, and breastfeeding people need 70 mcg per day.

What Foods Naturally Have Selenium?

Selenium is found in many foods, including plant foods and animal foods. Some foods are also fortified with selenium.

The amount of selenium in plant foods depends on the mineral’s presence in the soil where the plants grow.

Similarly, selenium levels in animal foods depend on the amount of selenium in the food (typically plants) the animal ate.

Good sources of selenium are outlined below:

  • Brazil nuts, 1 ounce, 544 mcg selenium: Just six to eight Brazil nuts contain 989% of the daily value for selenium. Therefore, consuming Brazil nuts in moderation is vital to prevent selenium toxicity.
  • Tuna, 3 ounces, 92 mcg selenium: One serving of tuna also contains more than 100% of the percent daily value for selenium. The FDA recommends no more than two to three servings of tuna per week since it contains mercury.
  • Sardines, 3 ounces, 45 mcg selenium: Sardines are a low-mercury fish and an excellent source of protein and calcium.
  • Shrimp, 3 ounces, 42 mcg selenium: Shrimp is another excellent source of selenium. However, it is a type of shellfish, a common allergen.
  • Lean meats, 3 ounces, 37 mcg selenium: Lean meats, like turkey, chicken, pork, and specific cuts of beef, provide more than half the percent daily value of selenium.
  • Pasta, 1 cup, 33 mcg selenium: Whole-grain pasta is typically higher in selenium and other nutrients than enriched pasta. Guidelines recommend that at least half of your daily grain intake comes from whole grains.
  • Eggs, one large egg, 15 mcg selenium: While eggs are a good source of selenium, they’re also an excellent source of cholineanother essential nutrient.
  • Baked beans, 1 cup, 13 mcg selenium: Beans, including baked beans, are a great source of fiber and can also be vegetarian and/or vegan.
  • Oatmeal, 1 cup, 13 mcg selenium: Oatmeal is a source of fiber and whole grains. It’s also vegan and vegetarian.
  • Brown rice, 1 cup, 12 mcg selenium: One cup of cooked brown rice provides 24% of the daily value of selenium. It’s also a source of fiber and B vitamins and is naturally gluten-free.

Many other foods contain selenium. Eating a wide variety of foods as frequently as possible is the best way to get all the selenium you need.

What Are the Risks of Selenium Supplements?

Although selenium supplements are mostly thought to be safe, they have some risks.

Some people may be allergic to selenium. You should seek immediate medical attention if you have a severe allergic reaction (itching, hives, shortness of breath) to selenium.

Selenium may be harmful if you take too much. Adults should not exceed 400 mcg of selenium daily.

Risks of taking selenium supplements include:

  • Side effects: Consuming too much selenium may increase the chance of side effects. Common side effects include nausea, diarrhea, a metallic taste in the mouth, skin rash, brittle nails, and hair loss.
  • Interactions: Selenium may interact with certain medications. Cisplatina chemotherapy drug, may lower selenium levels in your body. Before taking selenium, check with a healthcare provider if you take any medications.
  • Skin cancer: Some evidence that excessive selenium use may increase the risk of non-melanoma skin cancer. However, the study results are mixed, so more research is needed.
  • Type 2 diabetes: A high intake of selenium may increase the risk of type 2 diabetes, at least according to some studies. Too much selenium may cause hyperglycemia. More research is needed, however.
  • Toxicity: Very high doses or chronically high intake of selenium may result in toxicity. Signs of selenium toxicity include difficulty breathing, tremors, kidney failure, and heart failure.

To lower your risk of side effects, toxicity, or other adverse events, only use selenium supplements as directed, and never take more than you should.

Talk with your healthcare provider about how to safely use selenium.

What Are the Signs You Need Selenium?

Although rare in the United States, some people may become deficient in selenium. Before supplementing, a healthcare provider should evaluate you for signs of selenium deficiency. This may include ordering lab tests to determine selenium levels in your hair, nails, or blood.

Selenium deficiency occurs when your body doesn’t have enough of the mineral. Your risk of selenium deficiency may be higher if you are living with human immunodeficiency virus (HIV), are undergoing kidney dialysis, or live in an area with low selenium levels in the soil.

Selenium deficiency may lead to the development of certain illnesses. Keshan disease is a heart condition thought to be caused by selenium deficiency. Likewise, Kashin-Beck disease, a type of osteoarthritis, most often occurs in areas with low selenium.

Selenium deficiency may also worsen an iodine deficiency. If both deficiencies occur together, goiter or hypothyroidism may occur.

There is some evidence that low selenium levels may affect reproduction. In females, selenium deficiency may cause complications like miscarriage or low birth weight of the baby. In males, selenium deficiency has been linked to poor sperm quality, which may cause infertility.

Selenium Supplements

Most people can get all the selenium they need from a well-balanced diet. However, some people may need to use selenium supplements for various reasons.

Selenium supplements can be purchased online or in certain retail stores or specialty nutrition shops. A variety of selenium supplement forms are available, including capsules, tablets, and liquid extracts.

Many brands offer vegan and gluten-free selenium supplements. The product label will typically contain information about these specifics.

You can find supplements that contain selenium only or selenium plus other nutrients. For example, many multivitamins contain selenium.

If you use supplements, ensure your selenium intake from food and supplements doesn’t exceed the upper limit of 400 mcg per day. Consuming too much selenium may lead to side effects or toxicity.

Choose a supplement that a third-party agency such as NSF International, ConsumerLab.comor U.S. Pharmacopeia (USP) has approved whenever possible. These agencies review dietary supplements for harmful contaminants and quality but do not guarantee effectiveness.

Supplement use should be individualized and vetted by a healthcare professional, such as an RD or RDN, a pharmacist, or a healthcare provider. No supplement is intended to treat, cure, or prevent disease.

Summary

Selenium is an essential trace mineral that your body needs for specific processes. It plays a vital role in thyroid, heart, and cognitive (brain) health.

Selenium is found in soil and water and is in many plant and animal foods, including Brazil nuts, seafood, beans, and eggs.

Selenium deficiency is rare but may lead to the development of conditions like Keshan and Kashin-Beck disease. It’s also possible to consume too much selenium.

If you’re interested in using selenium supplements, talk with a healthcare provider to ensure you use them safely and correctly.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Brittany Lubeck, MS, RDN

Lubeck is a registered dietitian and freelance nutrition writer with a master’s degree in clinical nutrition.

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