Daily Selenium Intake: How Much Selenium Do You Need?

By The DRI Calculator Team  |  Published: August 14, 2026  |  Updated: August 14, 2026  |  9 min read

Your daily selenium intake only needs to be 55 micrograms for adults, one of the smallest targets of any nutrient, and here is the striking part: a single Brazil nut can contain that entire amount, sometimes more. Selenium is a trace mineral your body needs in tiny quantities for thyroid function, antioxidant defence, and immunity, but it has an unusually narrow window between enough and too much. Get it from a varied diet and you almost certainly meet the target without trying. Lean too hard on concentrated sources like Brazil nuts or supplements and you can quietly approach the safe limit. This guide gives the real numbers by age, answers the Brazil nut question properly, names the best foods, and explains how to stay in the safe zone.

What Your Daily Selenium Intake Should Be

The recommendation comes from the Recommended Dietary Allowance set by the National Academies. For adults it is 55 micrograms of selenium a day, rising to 60 micrograms in pregnancy and 70 micrograms while breastfeeding. Our guide to what DRI is explains how the RDA and the upper limit work together, which matters more for selenium than for most nutrients.

Selenium is a trace mineral, meaning the body needs only a very small amount, but that small amount does important work. It is built into a group of proteins called selenoproteins that act as antioxidants, support thyroid hormone metabolism, and help the immune system. Because the requirement is so tiny and many everyday foods contain selenium, most people in regions with selenium-rich soil meet the target easily.

Daily Selenium Intake by Age & Sex (Full Chart)

Selenium needs rise gradually through childhood and settle at 55 micrograms from the teen years, the same for both sexes, with small increases for pregnancy and breastfeeding.

How much selenium do you need per day?

Adults need 55 micrograms of selenium a day, the same figure for men and women. Pregnancy raises the target to 60 micrograms and breastfeeding to 70 micrograms. Children need less, from 20 micrograms at ages 1 to 3, up to 40 micrograms by ages 9 to 13.

The Brazil Nut Question: How Many Is Safe?

No food is more associated with selenium than the Brazil nut, and for good reason, but it is also where people most often go wrong. Brazil nuts draw selenium up from deep rainforest soil and concentrate it to an extraordinary degree, far beyond any other common food.

Best Food Sources of Selenium

Beyond Brazil nuts, selenium is spread across seafood, meat, eggs, and grains, and these everyday sources are the reliable, low-risk way to meet the target without worrying about portion size.

A single serving of tuna covers well over a day's selenium, and a mix of poultry, eggs, and whole grains gets most people to the target comfortably. This is why, unlike some nutrients, selenium deficiency is rare wherever soil selenium is adequate.

What Selenium Actually Does

Selenium's roles come mainly through the selenoproteins it forms. It acts as an antioxidant, helping protect cells from oxidative damage through enzymes like glutathione peroxidase. It is essential for the thyroid, in fact the thyroid gland holds more selenium per gram than any other tissue, and the mineral is needed to convert thyroid hormone into its active form. It also supports the immune system and plays a part in reproduction. These are genuine and important functions, but they are fully covered by the small 55 microgram target; more selenium does not enhance them, and beyond the safe limit it becomes harmful rather than helpful.

The Narrow Safe Window

Selenium is unusual in how close the useful amount sits to the harmful amount. The target is 55 micrograms and the tolerable upper intake level is 400 micrograms, and while that looks like a comfortable gap, concentrated sources close it faster than people expect. A couple of Brazil nuts plus a selenium-containing supplement can cover a surprising share of that range in a single day.

The Supplement-Stacking Trap

The most common way people accidentally approach the upper limit is by adding sources together without noticing. A daily multivitamin often contains 20 to 55 micrograms of selenium. A dedicated selenium supplement typically provides 100 to 200 micrograms. Add a couple of Brazil nuts on top, and the total can climb toward the ceiling quickly.

The point is not that any of these is unsafe on its own, but that selenium adds up across everything you take. If you use a multivitamin or a selenium supplement, it is worth doing the arithmetic before also eating Brazil nuts daily, and questioning whether a standalone selenium supplement is needed at all, since most people already meet the target from food. When in doubt, food alone is the safer route.

Signs of Low Selenium

Outright selenium deficiency is rare in North America and Europe, where soil selenium is generally adequate, and is more common in regions with selenium-poor soil, such as parts of China and Russia. When it does occur, low selenium is linked to impaired immune function and thyroid problems, and in severe, long-standing cases in deficient regions it has been associated with a form of heart muscle disease and a joint disorder. People most at risk include those with conditions that impair nutrient absorption, people on long-term dialysis, and those living where soil selenium is very low. Because the signs are non-specific and overlap with other conditions, a suspected deficiency should be assessed by a doctor rather than self-treated with supplements, given selenium's narrow safe window.

Who Needs to Watch Their Selenium

Most people meet their needs from a varied diet and never need to think about selenium. A few situations call for more attention. People with thyroid conditions sometimes ask about selenium, and while it plays a real role in thyroid function, supplementing should be guided by a doctor rather than assumed helpful. Those taking multivitamins or selenium supplements should account for the combined total, as above. Pregnant and breastfeeding women have slightly higher targets, covered in our guide to the DRI for pregnancy. The standard adult figures, which are the same for both sexes, sit within the wider picture in our guides to the DRI for men and the DRI for women.

How to Hit Your Daily Selenium Intake

For almost everyone, a varied diet handles selenium effortlessly. Seafood, poultry, eggs, and whole grains are all reliable sources, and a single serving of fish or a mix of these across the day easily covers the 55 microgram target. Brazil nuts are an excellent source too, but they are best treated as a small, deliberate portion, one or two a day, rather than something to snack on by the handful. Because the safe window is narrow, the guiding principle is to reach the target from everyday foods and be cautious about stacking supplements on top. For most people, no supplement is needed at all.

The most useful starting point is your own number, since it depends on your age and life stage. Your full nutrient targets, selenium included, take only a moment to calculate.

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