What is selenium?

Selenium is an essential trace element (micronutrient) that is crucial for the immune system and thyroid function.
The element selenium was discovered in 1817 and named after the Greek moon goddess Selene.
Selenium is stored primarily in the muscles and the thyroid gland.
Selenium exists in two forms: (both have dietary benefits)
- Inorganic (selenate and selenite)
- Organic (selenomethionine and selenocysteine)
The body incorporates selenium into special types of proteins called selenoproteins, which are critical to normal thyroid and immune function, DNA production, and reproductive health.

10 best selenium supplements for 2022
Capsules
- Thorne Research Selenomethionine
- The purest selenium supplement on the market.
- Each capsule contains about 100 mcg of selenium or 182 percent of the total daily value (DV).
- Pure Encapsulations Selenium
- Delivers the standard 200 mcg dose in a cellulose capsule and has a touch of vitamin C for better shelf life.
- Devoid of additional additives, making it a smart choice.
- Life Extension Super Selenium Complex
- Pairs two forms of selenium with vitamin E for added antioxidant power.
- Designed specifically to take advantage of selenium’s benefit for long-term well-being and youthfulness.
- The inclusion of two different types of selenium might marginally improve the bioavailability of this supplement.
- NOW Foods Selenium
- Klaire Labs Seleno Met
- Contains L-selenomethionine‚ which has superior absorption compared with other forms of selenium.
- Each capsule contains 200 mcg of selenium or 364 percent of the DV.
- Bluebonnet Selenium
- A certified vegan and soy-and gluten-free product that contains selenomethionine for optimal absorption.
- Each capsule contains 200 mcg of selenium or 364 percent of the DV.
- Vital Nutrients Multi-Nutrients
- Is iron-or iodine-free and a great choice for a multivitamin that covers the daily needs for most nutrients.
- Three capsules contain 100 mcg of selenium or 182 percent of the DV.
- Nordic Naturals Multi-Minerals
- Contains several minerals in highly absorbable forms, including magnesium, zinc, copper, and other minerals.
- Three capsules contain 41.25 mcg of selenium or 75 percent of the DV.
Liquid
- Go Nutrients Selenium
- Is for people who cannot or do not like to take pill-based supplements.
- Liquid selenium supplement contains 200 mcg of selenium in each six-droplet serving.
Softgels
- Carlson Labs ACES + Zinc
- Provides 100 mcg of selenium (182 percent of the DV) along with zinc, vitamins A, C, and E, and 50 mg of calcium per two softgels.
- Is a decent option for people who need extra nutrient support.

QUESTION
According to the USDA, there is no difference between a “portion” and a “serving.” See AnswerWhat are the sources of selenium?
Despite its wide availability in foods, deficiency may still occur due to environmental, health, and dietary factors.
Nuts, especially Brazil nuts, are the best source of selenium, containing about 544 mcg per ounce.
Other animals and plant-based selenium-rich foods include:
- Fish
- Shellfish
- Ham
- Beef
- Eggs
- Poultry
- Turkey
- Brewer’s yeast
- Wheat germ
- Shiitake and button mushrooms
- Oats
- Wholewheat bread
- Bran
- Brown rice
- Red Swiss chard
Selenium can be found in most multivitamin-mineral supplements.
What are the normal daily requirements of selenium?
According to the U.S. recommendations, an average adult (older than 19 years) needs about 50 to 60 mcg of selenium per day. The specific needs are:
Group | Amount |
---|---|
Teenagers (14 to 18 years) | 55 mcg |
Pregnant women | 60 mcg |
Breastfeeding women | 70 mcg |
Adults should not consume more than 400 mcg of selenium per day, with children usually needing less than 300 mcg.
What causes selenium deficiency and what can it lead to?
The following people are deficient in selenium:
- Those who do not consume a balanced diet
- Smokers and alcoholics
- Those living in an area where the soil has naturally low concentrations of this mineral
- Those undergoing kidney dialysis
- Those with human immunodeficiency virus infection
- Those suffering from intestinal diseases (ulcerative colitis and Crohn’s disease)
- Those taking drugs, such as corticosteroids, birth control pills, and clozapine
Though selenium deficiency is rare, it can cause male infertility and Keshan disease, which is characterized by heart failure and pulmonary edema.
Some pieces of evidence suggest that those who consume lower than average amounts of selenium are at increased risk of developing certain cancer, especially colon and rectum, lung, bladder, skin, stomach, esophagus, and prostate cancer.
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7 potential health benefits of selenium
- Helps protect cells and DNA from oxidative damage
- Oxidative damage and the inflammation that goes along with it are implicated in every chronic disease, ranging from heart disease and cancer to cognitive impairment in the elderly.
- Selenium acts at the level of the cell membrane, protecting external free radicals from causing damage to the cell membrane.
- May protect sperm cells against oxidative damage
- Researchers report that higher selenium levels in the blood were linked to less oxidative damage and better quality and density of the sperm.
- Low selenium levels are associated with cognitive decline in the elderly
- Several studies connect selenium deficiency to poor cognitive performance. It plays a role in brain function and oxidative damage protection.
- Might prevent degenerative diseases of the brain
- Evidence from both animal and human studies suggests that selenium helps protect the brain and reduce the effects of Alzheimer’s disease.
- Researchers report that this reduction was linked to the antioxidant activity of selenium, providing a biological link between its antioxidant and neuroprotective effects.
- Moreover, selenium works in synergy with the fatty acids, preventing their breakdown and enhancing their beneficial effects on cognition.
- Plays a role in the proper functioning of the thyroid gland
- Initial research reported that together with iodine, selenium played an important role in properly regulating the production of thyroid hormones.
- Selenium is used by the thyroid gland to prevent oxidation from hydrogen peroxide, which could disrupt the synthesis of critical proteins for hormone production.
- Selenium supplementation is useful for people with thyroid disorders, such as Hashimoto’s and Grave’s disease.
- Good for fertility and reproductive health
- Balanced selenium levels are important for reproductive health in men and women.
- In men, selenium helps produce sperm and testosterone, whereas, in women, adequate selenium levels are especially important during early pregnancy.
- Promotes heart health
- Selenium may protect against heart disease by boosting the antioxidant, glutathione, reducing oxidative stress, and preventing platelet clumping.
What are the recommended dosages and potential risks of selenium supplements?
The Office of Dietary Supplements has set tolerable upper limits of selenium at 400 mcg per day for adult males and females.
According to the Office of Dietary Supplements at the United States National Institutes of Health, consuming excessive selenium than the recommended daily amount can eventually lead to serious side effects, including:
- Nausea
- Irritability
- Teeth discoloration
- Brittle nails
- Diarrhea
- Garlic breath
- Skin rashes
- Fatigue
- A metallic taste in the mouth
In severe cases, kidney failure, heart attacks, heart failure, and even tremors may occur.
Some epidemiological studies have reported an increased risk of type II diabetes in people with higher selenium levels than average. Selenium can dominate the function of iodine in the thyroid gland, leading to thyroid problems.

SLIDESHOW
Foods That Aren't as Healthy as You Think See SlideshowHealth Solutions From Our Sponsors
Ranking the best selenium supplements of 2021. https://bodynutrition.org/selenium/
Selenium. https://www.ncbi.nlm.nih.gov/books/NBK557551/
Selenium. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
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