What Is Selenium?
Selenium is a mineral found in the soil. It naturally appears in water and some foods. While people only need a very small amount, selenium plays a key role in your metabolism.
What Are the Benefits of Selenium?
Selenium supports many of your body's functions, including:
Thyroid health
Your thyroid is a small gland that makes hormones to regulate your body's metabolic processes. If you have an underactive thyroid, you may have fatigue, weight gain, depression, and muscle aches. Over time, thyroid risks can worsen chronic diseases.
While selenium helps maintain healthy thyroid function, too much of it can harm your thyroid. Ongoing research is examining the role of selenium in people with thyroid conditions such as Hashimoto's disease and thyroiditis to "ensure they're getting adequate levels of selenium in their diet," says Amy Woodman, a registered dietitian and founder of Farmington Valley Nutrition and Wellness in Simsbury, CT.
Cognitive support
Research shows selenium's antioxidant properties fight cell damage that may worsen brain and nervous system diseases such as Parkinson's, Alzheimer's, and multiple sclerosis. Studies are ongoing to find if selenium can help prevent or treat the loss of mental skills. But scientists believe getting enough in your diet can help maintain healthy brain function.
Antioxidant protection
Selenium has attracted attention because of its antioxidant properties. Antioxidants protect cells from damage caused by things such as aging, lifestyle choices, and environmental conditions such as pollution. Over time, this cell damage — called oxidative stress — is linked to cancer, heart disease, and the decline of mental skills.
Heart and brain health
Research shows that people with higher levels of selenium in their blood have a lower chance of heart failure and death compared to those with low levels of the mineral. One study found that a lack of selenium is common among people with heart failure, especially older women and those who smoke. Researchers link it to worse symptoms and health outcomes.
Selenium is also important in brain health because it helps create selenoproteins, which are essential for how your brain works. Not getting enough of this mineral can harm brain growth and health, raising your chances of brain diseases in the future.
Immune system support
Studies show that selenium helps control inflammation and supports a healthy immune system. It plays a role in how immune cells send signals, handle stress, and fight infections.
Reproductive health
Healthy sperm rely on selenium, which you can get through the food you eat. Researchers aren't sure whether selenium supplements have the same effect. Selenium also protects against oxidative stress (damage to cells from free radicals), which can lead to infertility.
Selenium has also been studied for the treatment of dozens of other conditions. They range from asthma to arthritis to prostate cancer. The results of these studies have been inconclusive.
How Much Selenium Should You Take?
The recommended dietary allowance (RDA) includes the total amount of selenium you should get from foods and from any supplements you take. Most people can get their RDA of selenium from food.
The safe upper limit for selenium is 400 micrograms a day in adults. Anything above that is considered an overdose.
Group | Recommended Dietary Allowance |
| Children 1-3 | 20 micrograms/day |
| Children 4-8 | 30 micrograms/day |
| Children 9-13 | 40 micrograms/day |
| Adults and children 14 and up | 55 micrograms/day |
| During pregnancy | 60 micrograms/day |
| While breastfeeding | 70 micrograms/day |
Which Foods Are High in Selenium?
The amount of selenium in a food largely depends on the soil conditions where that food was grown.
Good food sources of selenium include:
Brazil nuts. Brazil nuts are the most powerful source of selenium available. But it's important to moderate your portions. Just one nut contains 95 micrograms, almost twice your daily requirement. Doctors suggest taking no more than 400 micrograms of selenium a day to avoid potential health risks.
Seafood. Most seafood contains high levels of selenium. In a 3-ounce serving, yellowfin tuna and white fish such as halibut have about 92 micrograms of the mineral, while tinned sardines contain 45 micrograms for the same portion.
Lean meat. Meat is an excellent source of many essential nutrients, including selenium. A sautéed chicken breast can have up to 35 micrograms of selenium, with an extra 5 micrograms if you eat the skin. Lean varieties of beef can be a great choice as well. Serve up a 4-ounce portion of skirt steak to get 26 micrograms of selenium.
Pasta. Pasta is an easy way to include selenium in most diets. One cup of cooked pasta has 36 micrograms, while whole-grain varieties have as much as 50 micrograms.
Rice. Because most rice is gluten-free, it can be a good option for people with wheat allergies or celiac disease. One cup of cooked white rice contains 9 micrograms of selenium. But you can get about 15 micrograms from a cup of brown rice varieties.
Eggs. One large egg can meet about 28% of your daily selenium requirement. Most is found in the egg's yolk. If you're watching your cholesterol intake, the egg white also has about 9 micrograms of selenium.
Oatmeal. Whether you have a bowl for breakfast, use it to thicken smoothies, or substitute it for flour in baked goods, oatmeal is an excellent selenium source. A cup of instant oatmeal contains 10 micrograms of selenium, while raw oats have up to 23 micrograms.
Baked beans. Baked beans — and some other vegetarian products — contain about 12 micrograms of selenium per cup. Beans are a great source of fiber as well, but canned beans contain high amounts of sodium. Moderate your portions to avoid health risks that can come with a high-sodium diet.
Other sources of selenium include:
- Cottage cheese
- Fortified cereals
- Lentils
- Whole wheat bread
What Are the Risks of Taking Selenium?
Our bodies need selenium to work well, but there are risks to adding more to your diet, including:
Side effects. Taken at normal doses, selenium doesn't usually have side effects. An overdose of selenium may cause bad breath, hair loss, fever, tiredness, and nausea.
Interactions. Selenium may also interact with other medicines and supplements you take, such as some antacids, chemotherapy drugs, corticosteroids, niacin, cholesterol-lowering statin drugs, and birth control pills.
Skin cancer. Selenium supplements may be linked to a risk of skin cancer (squamous cell carcinoma), so people at high risk of skin cancer shouldn't take these supplements.
What Is Selenium Deficiency?
Among healthy people in the U.S., selenium deficiencies are rare. "Most people are probably getting adequate amounts," Woodman says. But if your doctor tells you that you have low levels of selenium, "taking a multivitamin would be a safe way to make sure there's no deficiency." A multivitamin contains anywhere from 100% to 150% of the daily value of selenium.
Some health conditions, such as HIV or Crohn's disease, put you at a higher risk for low selenium levels. People who are fed through an IV are also at risk for selenium deficiency.
Symptoms of selenium deficiency include:
- Headache
- Nausea
- Confusion
- Fatigue
- Seizure
- Coma
Having a selenium deficiency could lead to:
- Infertility in men and those assigned male at birth
- Keshan disease (a type of heart disease)
- Kashin-Beck disease (a type of arthritis)
When to Take a Selenium Supplement
Your doctor may suggest you take a selenium supplement if you have a deficiency.
These supplements usually come in the form of capsules or tablets. But whole foods are the best sources of selenium, as the mineral may be destroyed when it's processed. Unless your doctor tells you to take a supplement, get selenium from foods to avoid taking too much.
What Are the Risks of a Selenium Overdose?
A little bit of selenium is usually plenty to meet your daily requirements. Over the long term, routinely getting unsafe levels could lead to selenium toxicity, a condition linked to stomach and nervous system issues, tremors, dizziness, breathing issues, kidney failure, and heart problems. At high enough levels, selenium toxicity could even be fatal.
Who Should Avoid Selenium Supplements?
People with an autoimmune disease or an underactive thyroid (hypothyroidism), as well as those taking birth control pills, immunosuppressants, medicines that slow blood clotting, niacin, barbiturates, or warfarin, should talk to their doctor before taking a selenium supplement.
Takeaways
Selenium is a mineral found in the soil, water, and many foods. It plays an important role in metabolism, thyroid and brain health, immune support, and fertility. Foods such as Brazil nuts, seafood, lean meats, eggs, pasta, and oatmeal are good sources. A lack of selenium is rare, but it can happen in people with certain medical conditions and lead to serious issues, such as infertility, heart disease, or arthritis. Too much selenium, especially from supplements, can be harmful and cause symptoms such as nausea, hair loss, and even serious health problems such as kidney failure or heart problems.
Selenium FAQs
Is selenium good for skin?
Selenium may protect against skin cancer, treat psoriasis, and help fight premature skin aging due to its antioxidant properties.
Is it safe to take selenium every day?
Doctors suggest taking no more than 400 micrograms of selenium per day to avoid possible health issues.
What are the benefits of selenium for women?
Selenium is thought to offer many health benefits, including supporting metabolism, thyroid health, brain health, immune health, and reproductive health.