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Supplements & Vitamins

Selenium: 6 Foods Ranked by Amount, and Why 1 Brazil Nut Covers Your Whole Day

Adults need 55 micrograms of selenium a day. A single Brazil nut carries 68 to 91, so one nut clears the whole target. Six of them clear the safe upper limit, which is the part nobody mentions.

Ageless Coach Editorial Team · August 30, 2026

In 30 Seconds
The target is 55 mcg a day. The Recommended Dietary Allowance is 55 micrograms for all adults 19 and over, the same figure for men and women, and it does not rise after 50. NIH Office of Dietary Supplements
The ceiling is 400 mcg a day. The Tolerable Upper Intake Level for selenium is 400 micrograms for adults, counting food and supplements together. NIH Office of Dietary Supplements
One ounce of Brazil nuts is 544 mcg. One ounce, about six to eight nuts, carries 544 micrograms of selenium, which is 989 percent of the Daily Value and above the adult ceiling. NIH Office of Dietary Supplements

One Brazil nut covers your entire daily selenium requirement, and six of them push you past the safe upper limit.

Selenium is a trace mineral. Your thyroid needs it to make hormones. But the gap between the dose you need and the dose that harms you is very narrow.

Here are the six foods that carry the most, ranked by the amount in a real serving. Then the ceiling, and why the biggest supplement trial ever run says to skip the pill.

1
The Six

Six Foods Ranked by How Much They Actually Carry

These are the top six from the food table published by the NIH Office of Dietary Supplements, in the serving sizes people actually eat.

The daily target to hold against them is 55 micrograms.

  1. Brazil nuts, 1 ounce, about 6 to 8 nuts. 544 mcg. Nearly ten times the daily target in one small handful, and above the 400 microgram adult ceiling on its own. This is a food to count, not to snack on.
  2. Yellowfin tuna, cooked, 3 ounces. 92 mcg. One ordinary serving carries well over a full day's requirement. Tuna alone can settle this nutrient for most people.
  3. Sardines, canned in oil with bone, 3 ounces. 45 mcg. Most of a day's target in one small tin, plus the calcium from the bones. Cheap and shelf stable.
  4. Shrimp, cooked, 3 ounces. 42 mcg. Roughly three quarters of the daily target. Seafood keeps appearing at the top of this list for a reason.
  5. Pork chop, bone in, broiled, 3 ounces. 37 mcg. Two thirds of the target from an everyday dinner. You do not need seafood to get there.
  6. Beef steak, bottom round, roasted, 3 ounces. 37 mcg. The same amount as the pork chop. Protein foods in general are where selenium lives.
544 mcg
One ounce of Brazil nuts, about 6 to 8 nuts, contains 544 micrograms of selenium, which is 989 percent of the Daily Value.
Source: NIH Office of Dietary Supplements

Look at the gap between the first line and the second. Nothing else on the list is close to the Brazil nut.

That is not a reason to eat more of them. It is the reason to count them.

2
The Ceiling

The 400 Microgram Line, and How Fast You Reach It

The adult Tolerable Upper Intake Level is 400 micrograms a day. That figure counts everything, food and pills together.

Now do the arithmetic on the nut. Each one holds 68 to 91 micrograms. Six nuts is 408 to 546. Six crosses the line even at the low end.

An open tin of sardines in oil on a bright yellow background
Sardines carry 45 micrograms in a 3 ounce serving, most of a day in one small tin.

The Office of Dietary Supplements says directly that Brazil nuts can cause you to go over the upper limit if you eat too many.

Too much selenium over time causes selenosis. The signs show up in hair and nails first. Hair loss. Brittle nails. A garlic odour on the breath. A metallic taste in the mouth.

Brazil nuts contain very high amounts of selenium (68 to 91 mcg per nut) and can cause you to go over the upper limit if you eat too many.

NIH Office of Dietary Supplements

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3
The Pill

The Biggest Trial Ever Run Said Skip the Supplement

Selenium supplements were sold for years on a prostate cancer prevention story. That story was tested properly, and it did not hold.

SELECT was the largest prostate cancer prevention trial ever run, with 35,533 men.

Two amber supplement bottles standing on a pink surface beside a green plant leaf
Most multivitamins already contain selenium, so a separate pill stacks on top of one you did not count.
35,533
SELECT enrolled 35,533 men and found that selenium and vitamin E, taken alone or together, did not prevent prostate cancer.
Source: National Cancer Institute

The National Cancer Institute reports that the trial's monitoring committee reviewed the data in September 2008 and found selenium and vitamin E, alone or together, did not prevent prostate cancer. Participants were told to stop taking the study supplements the following month.

Cleveland Clinic adds the everyday version of the same point. In North America it is very rare to need selenium supplementation, because food grown here typically provides plenty of it through the soil.

✗
The Debunk

Three Selenium Beliefs Worth Dropping Today

Three corrections worth carrying to the supplement aisle.

Antioxidant means you cannot have too much. Selenium is the clearest counterexample there is. The target is 55 micrograms and the ceiling is 400, a gap that one ounce of Brazil nuts clears on its own. Chronically high intake causes selenosis, and the first signs are your hair falling out and your nails going brittle.

A handful of Brazil nuts is a healthy daily habit. One nut is a full day. Six is over the safe limit. Treat them the way you would treat a dose rather than a snack, and never combine daily Brazil nuts with a selenium supplement.

Most people are probably deficient. Not in North America. The Office of Dietary Supplements says most people in the United States get enough selenium from the foods they eat, and names specific at risk groups such as people on kidney dialysis and people living with HIV. Outside those groups, deficiency here is rare.

📋Your Coach's Recommendations
1
Hit 55 micrograms from food, not a bottle.
One serving of tuna, sardines or shrimp does it. So does a pork chop plus the rest of a normal day. The Office of Dietary Supplements says a varied diet of protein foods, grains, beans and nuts gets most people there without a supplement.
2
Count Brazil nuts as a dose and cap them at two.
At 68 to 91 micrograms each, one nut already clears the daily target and six clears the 400 microgram ceiling. If you eat them regularly, do not also take a selenium supplement.
3
Read the label on the multivitamin you already take.
Selenium is in most multivitamin and mineral products. Adding a separate selenium pill on top is how people stack toward the ceiling without ever deciding to. Check the Supplement Facts panel before you buy anything new.

To your health,

Ageless Coach

Age Strong. Live Long.

Trusted Sources Behind This Article
NIH Office of Dietary SupplementsCleveland ClinicNational Cancer Institute

This article is education, not medical advice. Hair loss, brittle nails or a garlic odour on the breath while taking a selenium supplement is worth a conversation with your doctor.

Frequently Asked Questions

How much selenium do I actually need each day?
55 micrograms if you are 19 or older, and that figure is the same for men and women and does not change after 50. The Office of Dietary Supplements sets 60 micrograms in pregnancy and 70 while breastfeeding. One serving of tuna or a small tin of sardines covers the adult target on its own.
Is it safe to eat Brazil nuts every day?
In small numbers, yes, but count them rather than pour them. Each nut carries 68 to 91 micrograms, so one already covers your day and six lands at 408 to 546, past the 400 microgram ceiling. The Office of Dietary Supplements specifically warns that Brazil nuts can take you over the upper limit if you eat too many.
Should I take a selenium supplement for my thyroid?
Your thyroid does need selenium to make hormones, but needing a nutrient is not the same as needing a pill. Cleveland Clinic says it is very rare to need selenium supplementation in North America because the soil here is rich in it. If you think you are in one of the at risk groups, ask for a test rather than guessing.
What happens if I take too much selenium?
Chronically high intake causes selenosis. The Office of Dietary Supplements says it is most commonly characterised by hair loss and nail brittleness or loss, and that other signs include a garlic odour in the breath, a metallic taste in the mouth, skin rash, nausea, diarrhoea, fatigue and irritability. Stopping the source is the first step.
Does selenium prevent prostate cancer?
No. SELECT tested exactly that question in 35,533 men, and the National Cancer Institute reports the trial found selenium and vitamin E, alone or together, did not prevent prostate cancer. Participants were told to stop the supplements in October 2008. It remains the largest trial of its kind.
Can I get enough selenium if I do not eat seafood?
Easily. Pork and beef both carry 37 micrograms in a 3 ounce serving, and turkey, eggs, cottage cheese, beans, lentils and grain products all contribute. The Office of Dietary Supplements lists selenium in most protein foods, so a varied diet reaches 55 micrograms without any fish at all.
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