Selenium is a trace mineral that supports thyroid function, DNA production and protection of cells from damage. You need only a small amount, and too much can be harmful, so the right dose matters.
This guide covers daily needs, food sources, signs of excess, and who should be careful.
Daily selenium requirement
The NIH recommended dietary allowance (mcg per day):
- Children 1 to 3 years: 20 mcg
- Children 4 to 8 years: 30 mcg
- Children 9 to 13 years: 40 mcg
- Adults: 55 mcg
- Pregnant women: 60 mcg
- Breastfeeding women: 70 mcg
The tolerable upper limit for adults is 400 mcg per day (children 1 to 3: 90 mcg, 4 to 8: 150 mcg, 9 to 13: 280 mcg).
Best food sources of selenium
Most people get enough selenium from a normal diet.
- Seafood and fish
- Beef, pork and poultry
- Eggs and dairy products
- Grains, beans and lentils
- Nuts, especially Brazil nuts, which contain roughly 68 to 91 mcg per nut, so one or two a day is plenty
Forms of selenium in supplements
Supplements commonly contain selenomethionine, selenium yeast, or sodium selenite or selenate. Check the label so your total intake from food and supplements stays under the upper limit.
Signs of too much selenium
Long-term excess can cause:
- Garlic-like breath and a metallic taste
- Hair loss and brittle nails
- Skin rash, nausea and diarrhea
- Fatigue, irritability and nerve problems
Stop supplements and see a doctor if you notice these signs.
Who is at risk of low selenium and what about supplements
People on kidney dialysis, people with HIV, and those eating mostly food grown in selenium-poor soil may have lower intake. According to the NIH, selenium supplements have not been shown to reduce the risk of prostate cancer or heart disease, so they should not be taken for those reasons.
Selenium may interact with the chemotherapy drug cisplatin, so cancer patients should ask their oncologist first.
Frequently Asked Questions
How much selenium do I need every day?
Adults need 55 mcg per day. Pregnant women need 60 mcg and breastfeeding women 70 mcg.
What is the safe upper limit for selenium?
For adults, 400 mcg per day from all sources combined.
How many Brazil nuts can I eat?
One or two a day is usually enough, since a single nut can contain about 68 to 91 mcg of selenium.
Does selenium prevent cancer or heart disease?
According to the NIH, supplements have not been shown to lower the risk of prostate cancer or heart disease.
What are the signs of selenium toxicity?
Garlic breath, metallic taste, hair loss, brittle nails, rash, nausea, diarrhea, fatigue and nerve problems.
Related reading: Zinc daily needs and safe limits | Vitamin E daily needs and supplement safety | Vitamin C daily needs and food sources
Sources
Medical disclaimer: this article is for general information and does not replace advice from a qualified doctor. Do not start, stop or change any supplement or medicine without medical advice.