Nuts & Seeds · Nuts

Brazil Nuts: Benefits, Selenium, How Many a Day & Side Effects

Why one Brazil nut carries more selenium than most people need in a day, what the trials show for your thyroid, antioxidant enzymes and cholesterol, and why one to two a day is the right amount.

By Dr. Josh Axe, DC, DNM, CNS·23-min read

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Evidence-based48 sources citedUpdated October 3, 2026

Published Oct 3, 2026Last updated Oct 3, 2026Editorial policyMedical review policyFact-checking policy

Brazil nuts (Bertholletia excelsa), the seeds of an Amazon rainforest tree and the richest known food source of selenium.

The Dr. Axe Score™

7.3/10

Overall Dr. Axe Score · Brazil Nuts

Brazil nuts score 7.3 for their exceptional selenium, for randomized trials showing they raise the body's selenium enzymes, and for their copper and magnesium.

Scientific Evidence

7.0/10

Two meta-analyses of the nut's own randomized trials, which ran 6 weeks to 6 months.

Antioxidant & Anti-Inflammatory

7.4/10

Raised glutathione peroxidase in pooled trials; lower CRP and TNF in a controlled trial.

Clinical Effectiveness

7.2/10

Two nuts matched a 100 mcg selenium supplement; one to two a day is the amount.

Nutrient Density

7.6/10

Selenium, copper, magnesium and phosphorus; almost no omega-3.

Why this score?

Why Brazil Nuts scores 7.3 / 10

Weighting: Evidence 30% · Antioxidant & Anti-Inflammatory 25% · Clinical Effectiveness 25% · Nutrient Density 20% (7.0×0.30 + 7.4×0.25 + 7.2×0.25 + 7.6×0.20 = 7.27, shown as 7.3).

A transparent, weighted index built for foods. See how it’s calculated →

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Brazil nuts at a glance

Brazil nuts are the large, rich seeds of an Amazon rainforest tree and the richest known food source of selenium: on USDA's long-standing average, one nut carries 175% of the daily value.1 2 3 I recommend one to two a day.4

Best-supported use: raising your selenium and the antioxidant enzyme glutathione peroxidase; in a randomized trial, two nuts a day matched a 100 mcg selenium supplement on blood selenium and beat it on the enzyme5
Thyroid: selenium runs the enzymes that make active thyroid hormone, and selenium supplements lowered TPO antibodies in randomized trials of people with Hashimoto's 6 7
Amount: one to two a day, because the selenium in a single nut depends on the soil its tree grew in
Go carefully: a tree nut allergy, moldy or spoiled nuts, and doubling up with a selenium supplement

For the full thyroid plan, get the free Hypothyroidism Protocol.

A single Brazil nut weighs about 5 grams, yet on USDA's long-standing average it carries 96 micrograms of selenium, more than the 55 micrograms an adult needs in a day.2 6 The tree pulls selenium out of the rainforest soil and stores it in its seeds, so a nut or two a day can cover what your body needs.6

Brazil nuts are No. 1 on the list of thyroid-healing foods in my Hypothyroidism Protocol, where two Brazil nuts are the food alternative to 200 micrograms of selenium a day.4 Selenium is the working part of the enzymes that activate thyroid hormone and of the glutathione peroxidases, enzymes that protect your cells from oxidative damage.6

Selenium 200 mcg daily (or 2 Brazil nuts) — it runs the conversion enzymes and lowers antibodies.Dr. Josh Axe, DC, DNM, CNS

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Did you know?

Brazil nut trees take up selenium so readily that they're classed as selenium accumulators, alongside garlic and cabbage-family plants.6
Brazil nuts are on the approved food list in The Biblio Diet, my book with Jordan Rubin.8
After a randomized trial, researchers in New Zealand concluded that two Brazil nuts a day could improve New Zealanders' selenium status without fortified foods or supplements.5

What are Brazil nuts?

Quick answer

Brazil nuts are the large, oil-rich seeds of Bertholletia excelsa, a tree of the Lecythidaceae family that grows in the Amazon region.1 9 Researchers call them the richest known food source of selenium, the mineral your body builds into its antioxidant and thyroid enzymes.1 6

Shelled, a Brazil nut is cream-colored with patches of thin brown skin and a rich, mild flavor, and each one weighs about 5 grams.2 Two-thirds of that weight is fat, mostly unsaturated, with a little protein and fiber.2 The selenium comes from the soil, which is why it varies so much from nut to nut, as the section on selenium per nut explains.6

Where Brazil nuts come from

Brazil nuts are part of the traditional diet in river communities of the Brazilian Amazon, such as those along the Lower Tapajós River, where people also eat chicken, game meat and fish.10 Today researchers study them as a natural way to improve selenium status in countries such as New Zealand,5 and for vegans and vegetarians, whose plant-based diets tend to supply less selenium.11 12

Brazil nuts nutrition facts

Quick answer

Two Brazil nuts (10 grams) have about 66 calories and, on USDA's long-standing average, 192 micrograms of selenium, 349% of the daily value, plus 19% of your daily copper and 9% of your magnesium. One nut is about 33 calories and 96 micrograms of selenium.2 3

Calculated from USDA FoodData Central, SR Legacy FDC ID 170569, at USDA's weights of 5 grams per nut and 28.35 grams per ounce; % Daily Value uses FDA reference values.2 3

Nutrient	2 nuts (10 g)	% DV (2 nuts)	1 ounce (about 6 nuts)	% DV (1 ounce)
Calories	66	n/a	187	n/a
Total fat	6.7 g	9%	19.0 g	24%
Saturated fat	1.6 g	8%	4.6 g	23%
Monounsaturated fat	2.4 g	n/a	6.8 g	n/a
Polyunsaturated fat	2.4 g	n/a	6.9 g	n/a
Protein	1.4 g	3%	4.1 g	8%
Carbohydrate	1.2 g	under 1%	3.3 g	1%
Fiber	0.8 g	3%	2.1 g	8%
Selenium	192 mcg	349%	544 mcg	990%
Copper	0.17 mg	19%	0.49 mg	55%
Magnesium	38 mg	9%	107 mg	25%
Phosphorus	73 mg	6%	206 mg	16%
Thiamin	0.06 mg	5%	0.17 mg	15%
Manganese	0.12 mg	5%	0.35 mg	15%
Vitamin E	0.6 mg	4%	1.6 mg	11%
Zinc	0.4 mg	4%	1.15 mg	10%
Potassium	66 mg	1%	187 mg	4%

Selenium is the headline, and two nuts also bring a fifth of your daily copper along with some magnesium, phosphorus and thiamin. Nearly all of their polyunsaturated fat is linoleic acid, with only a trace of plant omega-3,2 so pair them with walnuts or ground flaxseed when you want omega-3s.

How much selenium is in one Brazil nut?

Quick answer

It depends on where the tree grew. USDA's long-standing average works out to about 96 micrograms a nut, but the averages in the table below run from about 14 micrograms a nut in USDA's 2023 record to about 1,261 in nuts used for a São Paulo trial, and single nuts tested one at a time spread wider still.2 13 14 15

The tree takes up whatever selenium its soil holds. Brazil nuts grown in selenium-rich soil can carry more than 100 micrograms in one nut, while nuts from selenium-poor soil carry about a tenth of that.6 Even USDA has two records: its long-standing SR Legacy average of 1,920 micrograms per 100 grams comes from 15 samples that ranged from 136 to 2,740, and its 2023 Foundation record of eight samples lists 280, while the two records' other minerals line up closely.2 13 Here's what the published samples work out to per nut:

Selenium in one Brazil nut, from published samples (per 5-gram nut where calculated)

Source	What was measured	Selenium per nut
USDA Foundation record, 2023	8 samples, 280 mcg per 100 g	About 14 mcg13
New Zealand randomized trial	Two nuts supplied 53 mcg a day	About 26.5 mcg5
USDA SR Legacy record	15 samples, 1,920 mcg per 100 g	About 96 mcg2
Brazilian controlled trial	8 g supplied 347.2 mcg	About 217 mcg16
Brazilian dialysis studies	58.1 mcg per gram of nut	About 290 mcg1 17
São Paulo randomized trial	Reported per nut	About 1,261 mcg14
324 single nuts from two Brazilian regions	0.03 to 512 parts per million	About 0.15 to 2,560 mcg15

That spread is the reason I recommend one or two a day rather than a handful. In the New Zealand randomized trial, two nuts came to about 53 micrograms, while at the São Paulo trial's level, one nut held more than 20 times the daily value.5 14 Grinding evens things out: in measurements made for a 2025 randomized trial, Brazil nut butter made from a single batch measured 3.45 to 3.65 micrograms of selenium per gram, while eight individual nuts from five batches ranged from 0.25 to 5.06.12

What are Brazil nuts good for?

Quick answer

Brazil nuts are best for raising your selenium status and the activity of glutathione peroxidase, the selenium enzyme that defuses peroxides. Two meta-analyses of randomized trials found that eating them raised both.18 19 Other human trials link them to lower inflammation markers, lower oxidized LDL, better verbal fluency in older adults with mild cognitive impairment, and higher thyroid hormone in dialysis patients low in T3.

Where the research stands

Brazil nuts have two meta-analyses of their own randomized trials (8 and 7 trials), and both found higher blood selenium and glutathione peroxidase.18 19 A systematic review of 24 clinical trials, 15 of them not randomized, found antioxidant status improved in all the studies that measured it.20 The Brazil nut trials on this page enrolled 17 to 133 people and lasted 2 weeks to 6 months, and they measured blood markers rather than outcomes such as heart attacks, so the evidence is strongest for selenium status and the enzymes it powers.

Brazil nut benefits, graded by evidence strength (Updated October 2026)
Benefit	Evidence	What was studied	What the research shows	Good to know
Selenium status	Strong	Whole nuts, nut flour or granules; 7 randomized trials in each pooled analysis	Blood selenium rose in both pooled analyses19 18	Selenoprotein P rose too in a 2025 randomized trial12
Antioxidant enzyme (glutathione peroxidase)	Strong	Whole nuts or nut products; 2 meta-analyses of randomized trials	Enzyme activity rose18 19	Every dialysis patient reached the normal range in a single-group study1
Thyroid support	Moderate	Selenium supplements in Hashimoto's; 1 nut a day in dialysis patients	TPO antibodies lower; T3 higher in dialysis patients low in it7 17	Results held or grew stronger with selenomethionine, the form in Brazil nuts7
Lower inflammation	Emerging	8 g of nuts a day on a weight-loss diet	CRP, TNF, IL-1β and IL-8 lower than with no nuts16	The effects tracked selenium status
Cholesterol and oxidized LDL	Mixed	Whole nuts, nut flour or granules	Cholesterol, triglycerides and oxidized LDL lower than placebo in one trial; oxidized LDL lower in another21 22	Small-vessel blood flow improved too in the teen trial21
Brain health in older adults	Emerging	1 nut a day, mild cognitive impairment, 6 months	Verbal fluency and constructional praxis improved more than control23	Blood selenium rose in the nut group23
Blood sugar and DNA protection	Emerging	1 nut a day, type 2 diabetes, 6 months	Fasting glucose, LDL and DNA damage fell24	Glutathione and catalase rose too24

How do Brazil nuts work in your body?

Brazil nuts work through their selenium, which your body builds into enzymes that defuse peroxides and make active thyroid hormone. Here's the path from the nut to those enzymes:

1Selenium arrives as selenomethionine

In Brazil nuts, most of the selenium is bound into the amino acid selenomethionine.9

2Digestion releases most of it

In a lab model of digestion, about 85% of the nut's selenium was released in a form your gut can absorb.9

3Stored or put to work

Your body can tuck selenomethionine into its proteins in place of methionine, a reserve that may be released as proteins turn over, or use its selenium to build at least 25 selenoproteins.6

4Glutathione peroxidases defuse peroxides

These selenium enzymes turn hydrogen peroxide and damaged fats called lipid hydroperoxides into harmless water and alcohols.6

5Deiodinases make active thyroid hormone

Selenium-dependent deiodinases remove one iodine atom from T4 to make T3, the active form; most of the T3 in your blood and cells is made this way.6

Heal Your Cells, my book with Dr. Will Cole, describes selenium as part of antioxidant enzymes like glutathione peroxidase, which protect your mitochondria and lysosomes from oxidative damage.25 On my show, I've explained that selenium works together with riboflavin (vitamin B2), magnesium and vitamin C to help your body make more glutathione, your master antioxidant.26

That's why Brazil nuts, for their selenium, were on the list of foods we had my mom eat constantly while she battled cancer, alongside broccoli sprouts, cruciferous vegetables, garlic and onions, eggs and salmon.26 Those foods were part of the nutrition and lifestyle support that went along with her medical care.

Brazil nut benefits, ranked by evidence

Ordered from the most human research to the least, Brazil nuts are best for raising selenium status, boosting the selenium antioxidant enzyme, supporting the thyroid, calming inflammation, improving oxidized LDL and cholesterol markers, supporting brain health in older adults, and protecting DNA in type 2 diabetes. Each card names the design and size of the studies behind it.

Raises selenium status

Strong evidenceHuman study2 meta-analyses · 7 randomized trials each; randomized trials · 59 and 86 adults

Pooled across seven randomized trials and 315 people, eating Brazil nuts raised plasma selenium by 87.63 micrograms per liter, and a separate meta-analysis, pooling seven of its eight randomized trials, found a large rise as well.19 18 In a 12-week randomized trial of 59 New Zealand adults, two Brazil nuts a day raised plasma selenium 64.2%, about the same as a 100 mcg selenomethionine supplement (61.0%; the difference wasn't significant), compared with 7.6% on placebo, even though the nuts turned out to supply only about 53 micrograms a day.5 In a 2025 randomized trial of 86 vegans and omnivores, Brazil nut butter supplying 55 micrograms a day raised serum selenium and selenoprotein P, the protein that carries selenium through the body, as well as a supplement with the same amount over two weeks, while the placebo groups didn't change.12

Study takeaway: two Brazil nuts a day raised blood selenium as much as a 100 mcg supplement.

Boosts the selenium antioxidant enzyme

Strong evidenceHuman study2 meta-analyses · 5 and 3 randomized trials; randomized trials · 59 and 91 adults; single-group study · 81 people

Glutathione peroxidase, the enzyme family in the diagram above, is one of your body's main defenses against peroxides. In the New Zealand trial, whole-blood glutathione peroxidase rose 13.2% on two nuts a day, more than on the 100 mcg supplement (5.3%) or placebo (1.9%).5 Pooled across five randomized trials, the enzyme's activity rose, and a second meta-analysis, pooling three trials, put the rise at 8.05 units per gram of hemoglobin.18 19 In a randomized trial of 91 adults in which each person tried both, Brazil nut granules roughly doubled plasma selenium, from 87.0 to 180.6 micrograms per liter, and raised plasma glutathione peroxidase from 112.66 to 128.32 units.22 In 81 people on dialysis, all low in selenium, one nut a day for 3 months raised the enzyme from 46.6 to 55.9 units per gram of hemoglobin in a study with no comparison group, and afterward every patient's activity was in the normal range.1

Study takeaway: two nuts a day raised the body's selenium enzyme more than a 100 mcg selenium supplement.

Thyroid support

Moderate evidenceHuman studyMeta-analysis of selenium supplements · 35 randomized trials; pilot with no comparison group · 40 people

Selenium is the working part of the enzymes that make active thyroid hormone, and in randomized trials of people with Hashimoto's, selenium supplements lowered TPO antibodies.6 7 One Brazil nut a day also raised T3 in a study of 40 dialysis patients, which had no comparison group. The thyroid section below has the numbers.17

Study takeaway: selenium supplements lowered TPO antibodies in randomized trials of people with Hashimoto's.

Calms inflammation

Emerging evidenceHuman studyControlled trial, not randomized · 56 women, 46 finished; study with no comparison group · 40 people

In an 8-week trial of 56 women with overweight or obesity on a reduced-calorie diet (46 finished; the groups weren't randomized), those who ate 8 grams of Brazil nuts a day, about one and a half nuts supplying 347.2 micrograms of selenium, ended with lower C-reactive protein, TNF, IL-1β and IL-8 and lower intestinal permeability than women on the same diet without nuts, and both groups lost similar weight.16 The bigger a woman's rise in blood selenium, the bigger her drop in IL-8.16 In 40 people on dialysis, one nut a day for 3 months lowered TNF-α, IL-6 and markers of oxidative damage to DNA and fats, in a study with no comparison group.27

Study takeaway: about 8 grams of Brazil nuts a day lowered CRP and three inflammatory cytokines compared with the same diet without nuts.

Cholesterol and oxidized LDL

Mixed evidenceHuman studyRandomized trials · 17, 91 and 77 people; study with no comparison group · 40 people; meta-analysis · 3 trials

In a 16-week randomized trial of 17 teenage girls with obesity, 3 to 5 Brazil nuts a day, more than the amount on this page, lowered median total cholesterol from 152 to 136 mg/dL, LDL from 86.5 to 72.5 and triglycerides from 84.5 to 69.0, and total cholesterol, triglycerides and oxidized LDL ended lower than in the placebo group; the girls knew which group they were in.21 The nuts also sped red blood cells through the tiny capillaries at the base of the fingernails compared with placebo, a sign of better small-vessel function.21 In 91 adults with high blood pressure and high cholesterol, in a trial where each person tried both and neither the people nor the researchers knew who got what, 13 grams a day of partially defatted Brazil nut granules for 12 weeks lowered oxidized LDL from 66.31 to 60.68 U/L.22 In a second report from the same research program, 77 people already taking cholesterol-lowering drugs got partially defatted Brazil nut flour or a placebo flour for 90 days, and neither the people nor the researchers knew who got what; total cholesterol fell 20.5 mg/dL within the nut group, a change that didn't differ significantly from the placebo group.28 In 40 people on dialysis, one nut a day for 3 months raised HDL and lowered LDL, in a study with no comparison group.27 Pooled across three trials, the shifts in total, LDL and HDL cholesterol were too small to rule out chance,18 so the steadiest signal so far is lower oxidized LDL, seen in two of the trials.21 22

Study takeaway: Brazil nuts lowered oxidized LDL in two trials, and cholesterol and triglycerides compared with placebo in one.

Brain health in older adults

Emerging evidenceHuman studyRandomized pilot trial · 31 enrolled, 20 finished

In a 6-month pilot trial, 31 older adults with mild cognitive impairment were randomly assigned to one Brazil nut a day, estimated at 288.75 micrograms of selenium, or their usual diet; 20 finished. In the nut group, blood selenium rose, red-blood-cell glutathione peroxidase changed differently from the control group, and verbal fluency and constructional praxis, the ability to copy shapes and drawings, improved more than in the control group.23

Study takeaway: one Brazil nut a day improved verbal fluency in older adults with mild cognitive impairment.

Blood sugar and DNA protection in type 2 diabetes

Emerging evidenceHuman studySingle-group study · 133 enrolled, 74 finished

In 133 people with type 2 diabetes and overweight who ate one Brazil nut a day for 6 months (74 finished; there was no comparison group), selenium, glutathione and the antioxidant enzymes glutathione peroxidase and catalase rose, markers of oxidative damage to fats and proteins fell, and LDL and HDL cholesterol and the liver enzyme GGT dropped. DNA damage fell, and so did fasting glucose.24

Study takeaway: one Brazil nut a day for six months was followed by less DNA damage and lower fasting glucose in type 2 diabetes.

Are Brazil nuts good for your thyroid?

Quick answer

Yes. Brazil nuts are one of the best foods for your thyroid because of their selenium. Selenium runs the enzymes that turn T4 into active T3, selenium supplements lowered TPO antibodies in randomized trials of people with Hashimoto's, and in a study of 40 dialysis patients with no comparison group, one Brazil nut a day raised T3 in people who were low in it.6 7 17

Your thyroid releases mostly T4, a storage form of thyroid hormone, and selenium-dependent enzymes turn it into active T3, the step shown in the diagram above.6 That chemistry is why selenium is a centerpiece of thyroid nutrition, especially in autoimmune thyroid disease.

If you have high TPO antibodies, so Hashimoto's thyroiditis, selenium is probably the single most important nutrient.Dr. Josh Axe, DC, DNM, CNS

The largest body of antibody research is on selenium itself. A 2024 meta-analysis of 35 randomized trials of selenium supplements in Hashimoto's found that selenium lowered TPO antibodies across 29 groups of 2,358 people, a large effect by the usual research yardstick. It also lowered TSH in people not yet taking thyroid hormone (7 groups, 869 people) and lowered malondialdehyde, a marker of oxidative damage. Free and total T4 and T3 didn't change, side effects were no more common than in the control groups, and the results held or grew stronger with selenomethionine, the form in Brazil nuts. The authors rated the overall certainty of the evidence as moderate, and low for the antibody result.7

One of the earliest trials shows what that looks like. Seventy women with autoimmune thyroiditis, all already taking thyroid hormone, were randomly assigned to 200 micrograms of selenium (as sodium selenite) or a placebo for 3 months, without knowing which they got. TPO antibodies fell to 63.6% of their starting level on selenium, a 36.4% drop, compared with 88% on placebo, a 12% drop that wasn't significant. Antibodies returned to normal in 9 women on selenium and 2 on placebo, and in women who started with antibodies above 1,200 IU/mL, they fell 40% on selenium and rose 10% on placebo. TSH and free thyroid hormones didn't change in either group.29

The Brazil nut studies so far have measured thyroid hormones rather than antibodies. In 40 people on dialysis, all low in selenium and in T3, one nut a day for 3 months raised T3 from 27.3 to 50.2 ng/dL and free T4 from 0.87 to 0.98 ng/dL, though T3 didn't reach the normal range; the study had no comparison group.17 In the randomized 90-day trial of 77 people on Brazil nut flour or placebo flour, free T3 fell in the placebo group and held steady in the nut group.28 Pooled across the randomized trials that measured them (two for T3 and T4, three for TSH), Brazil nuts left T3, T4 and TSH where they were,19 which fits what researchers see with selenium in general: the benefit shows up where status is low.30

My Hashimoto's Protocol puts one to two Brazil nuts among the foods that calm the autoimmune attack.31 If you take thyroid medication, keep taking it exactly as prescribed. Levothyroxine is meant to be taken on an empty stomach, and its label lists walnuts and dietary fiber among foods that can bind it and reduce its absorption, so eat your Brazil nuts with a later meal.32 To know where you stand, ask your doctor for TSH, free T4, free T3 and TPO antibodies.

Five markers that show your thyroid and selenium picture

These markers show how your thyroid is working, whether autoimmunity is part of the picture, and where your selenium stands. No single result diagnoses a thyroid condition on its own.

TSH: The pituitary's signal to your thyroid. It rises when the thyroid is underactive.
Free T4: The main hormone your thyroid releases, the raw material for T3.
Free T3: The active thyroid hormone, made mostly by selenium-dependent enzymes.
TPO antibodies: The antibodies that mark autoimmune (Hashimoto's) thyroiditis.
Selenium: Your current selenium status, useful before you add a supplement.

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The key compounds in Brazil nuts

Selenium does most of the work, and it comes packaged with a small set of plant compounds and fat-soluble antioxidants.

Selenomethionine

The main selenium form

The form your body can store in its proteins or use to build selenoproteins.9 6

Phenolic compounds

Flavan-3-ols and phenolic acids

Catechin, epicatechin, quercetin, and ellagic, gallic and ferulic acids, measured in lab composition analysis.33

Vitamin E and plant sterols

Tocopherols, squalene, beta-sitosterol

Alpha- and gamma-tocopherol, squalene, and 64 mg of beta-sitosterol per 100 grams.33 2

Not sure how Brazil nuts fit your day?

Ask Dr. Axe AI. Answers are grounded in this library, with sources shown.

How many Brazil nuts should you eat a day?

Quick answer

One to two a day. That's the amount I recommend, and at USDA's long-standing average two nuts supply about 192 micrograms of selenium, close to the 200 micrograms a day in my thyroid protocol.4 2

One to two a day is the rule, including during pregnancy and breastfeeding. Every source of selenium counts toward the daily upper limit for your age, including multivitamins and prenatals, and at USDA's long-standing average one nut carries about 96 micrograms:2 34 35

Daily upper limits for selenium from all sources (micrograms a day)

Group	U.S. limit (Institute of Medicine)	European limit (EFSA, 2023)
Adults, including pregnancy and breastfeeding	400	255
Teens	400 (ages 14 to 18)	230 (ages 15 to 17)
Older children	280 (ages 9 to 13)	180 (ages 11 to 14)
Children	150 (ages 4 to 8)	130 (ages 7 to 10); 95 (ages 4 to 6)
Toddlers, ages 1 to 3	90	70

Europe's food safety authority explains why the amount matters: a serving of five or six Brazil nuts could supply anywhere from about 100 to 2,000 micrograms of selenium, and regular Brazil nut eaters are one of the few groups it expects can pass the limit.35 A traditional Amazon diet has a reassuring record: when researchers examined 448 people in 12 communities along the Tapajós River, whose diet includes Brazil nuts, blood selenium ran from normal to very high, and no skin, nail, hair or breath signs of selenium toxicity were tied to it.10

In a trial of 1,202 people from low-selenium areas of the eastern U.S., where neither the people nor the researchers knew who got what, 200 micrograms of selenium a day from a supplement for an average of 7.7 years was followed by more type 2 diabetes than placebo, 12.6 versus 8.4 new cases a year for every 1,000 people, a secondary finding of the trial, with the highest risk in people who started with the most selenium in their blood.36 Food selenium can overshoot too: in a randomized trial of 55 São Paulo women with obesity who weren't low in selenium, one very high-selenium nut a day, about 1,261 micrograms, raised the activity of inflammatory genes over two months while their blood inflammatory proteins stayed the same; the comparison group ate no nuts.14 Selenium helps most where status is low, and people who already have plenty may be harmed by piling on more.30

That's why I keep selenium from supplements at or under 200 micrograms a day; more isn't better.31 In my Hypothyroidism Protocol, the two nuts and the 200-microgram supplement are alternatives, so choose one or the other, not both.4 On days you skip the nuts, wild-caught salmon, sardines and pasture-raised eggs are other selenium foods in that protocol.4

How should you eat, buy and store Brazil nuts?

Chop one over oatmeal or plain yogurt at breakfast.

Stuff a Medjool date with one for a two-bite snack.

Grate one over a salad dressed with olive oil.

Blend one into a berry smoothie.

Add one or two to a small mix of walnuts and pumpkin seeds.

Pair two with an apple for an afternoon snack.

Buy shelled nuts that are whole, plump and evenly colored, from a store that sells through its stock, and skip any that look shriveled, discolored or moldy; the safety section explains why. Store them in an airtight container in the refrigerator or freezer, because their unsaturated fat turns rancid with heat, light and air,2 and toss any that smell sharp or bitter. Prepare them the way The Biblio Diet recommends for nuts and seeds: soaking them in water and drying them in a low-temperature oven or a food dehydrator makes them easier to digest.8

Brazil nuts vs. other nuts

Ounce for ounce, no common nut comes close to Brazil nuts for selenium, and they also lead this group on magnesium. Walnuts bring the plant omega-3s and almonds the vitamin E, so a small mix of the three covers a lot of ground.

Brazil nuts and four common nuts, per 1 ounce (28 g) (USDA FoodData Central)
	Brazil nuts (about 6)	Almonds	Walnuts	Cashews	Macadamia nuts
Calories	187	164	185	157	204
Selenium	544 mcg	1.2 mcg	1.4 mcg	5.6 mcg	1.0 mcg
Magnesium	107 mg	77 mg	45 mg	83 mg	37 mg
Copper	0.49 mg	0.29 mg	0.45 mg	0.62 mg	0.21 mg
Vitamin E	1.6 mg	7.3 mg	0.2 mg	0.3 mg	0.2 mg
Plant omega-3 (ALA)	Under 0.01 g	Under 0.01 g	2.6 g	0.02 g	0.06 g

An ounce of Brazil nuts is about six nuts, so your one or two supply up to about a third of that column, which is still far more selenium than a full ounce of any other nut here.2 37 38 39 40 See the guides to the healthiest nuts, cashews and macadamia nuts for more.

What are the side effects of Brazil nuts?

Quick answer

At one to two a day, Brazil nuts are a safe, nourishing food for most people. The cautions are eating many nuts every day, which can push selenium past its daily upper limit; a tree nut allergy; and moldy or spoiled nuts.35 They also carry natural radium; for an adult, two nuts a day add less than a tenth of the average yearly dose from natural background.41

Too much selenium

Selenium toxicity, called selenosis, comes from high intake over time. Its signs include brittle, thickened nails with white spots and streaks, brittle hair and hair loss, garlic-smelling breath, tooth discoloration, skin lesions and nervous-system symptoms.35 If you notice them, stop the Brazil nuts and any selenium supplement and ask your doctor to check your selenium level. The daily limits by age are in the how-many section above.

Radium

Brazil nut trees also draw natural radium and barium from the soil.9 Germany's Federal Office for Radiation Protection estimates that two nuts a day add about 160 microsieverts of radiation a year for an adult, against an average of about 2,100 microsieverts a year from natural background.41 A 2025 review put one or two nuts a day at about 88 to 220 microsieverts a year, and in a lab model of digestion only about 2% of the nuts' radium was released in absorbable form.11 9 Staying at one or two a day keeps that exposure small.

Aflatoxin and mold

Brazil nuts can carry aflatoxin, a toxin made by certain molds. In 95 samples from Brazilian supermarkets and street markets, 37.9% had detectable aflatoxin and three exceeded the international Codex limit of 10 micrograms per kilogram for ready-to-eat nuts.42 Most of the toxin sits in spoiled nuts: in in-shell lots from Amazon processing plants, rotten nuts made up 4.2% of the weight but 76.6% of the aflatoxin.43

Tree nut allergy

Brazil nut allergy is one of the tree nut allergies, and it can be severe. In a lab study of blood samples from 11 people who'd had anaphylaxis after eating Brazil nuts, all had antibodies to a Brazil nut protein called 2S albumin, while none of 10 people with antibodies to the nut but no symptoms did.44 Allergy specialists diagnose tree nut allergy from your history together with skin or blood tests, and avoidance plus an emergency plan is the core of care.45 If you have a tree nut allergy, skip Brazil nuts unless your allergist has confirmed you tolerate them, and get emergency care for lip or throat swelling, wheezing or faintness after eating them. See food allergy symptoms for the warning signs.

Kidney disease

Two nuts carry about 73 milligrams of phosphorus and 66 of potassium, small amounts.2 If you have kidney disease and follow a phosphorus or potassium limit, count them with the rest of your day within your care team's plan; see the renal diet guide. The dialysis studies on this page gave one nut a day for 3 months.1

The bottom line

Should you eat Brazil nuts?

Yes. Brazil nuts are the richest known food source of selenium, and randomized trials show that eating them raises your selenium as well as a selenium supplement does; in one, two nuts a day raised glutathione peroxidase, the selenium enzyme that defuses peroxides, more than the supplement. Selenium also runs the enzymes that make active thyroid hormone, which is why Brazil nuts top my list of thyroid-healing foods. People in the Amazon have made them part of a traditional diet, and the selenium research now explains why they're so valuable.

Eat one to two a day, raw or soaked and dried, with breakfast or a snack, and choose them in place of a selenium supplement rather than on top of one. Skip them with a tree nut allergy, and toss any nut that's shriveled, discolored or smells off. My philosophy has always been to use food as medicine first, and a nut or two with breakfast is an easy place to start.46

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Brazil nuts: frequently asked questions

Are Brazil nuts good for you?

Yes. Brazil nuts are the richest known food source of selenium, and randomized trials show that eating them raises your selenium and the antioxidant enzyme glutathione peroxidase, with copper, magnesium and phosphorus as a bonus.5 18 2

How many Brazil nuts should I eat a day?

One to two. That's the amount I recommend, because the selenium in a single nut varies so widely, and in my thyroid protocol two nuts are the food alternative to a 200-microgram selenium supplement, so don't eat them on top of one.4

How much selenium is in one Brazil nut?

About 96 micrograms on USDA's long-standing average, 175% of the daily value, but the averages cited here run from about 14 to about 1,261 micrograms a nut, depending largely on the selenium in the soil where the tree grew.2 13 14 6

Are Brazil nuts good for your thyroid?

Yes. Their selenium runs the enzymes that turn T4 into active T3, selenium supplements lowered TPO antibodies in randomized trials of people with Hashimoto's, and one Brazil nut a day raised T3 in a study of 40 dialysis patients with no comparison group.6 7 17 They're No. 1 on my list of thyroid-healing foods.4

Can you eat too many Brazil nuts?

Yes. Eating many nuts every day can push your selenium past its daily upper limit and, over time, cause selenosis, with brittle nails, hair loss and garlic-smelling breath.35 One to two a day is the amount I recommend, and the limits by age are in the how-many section above.

Are Brazil nuts radioactive?

Slightly. They carry natural radium from the soil, and Germany's Federal Office for Radiation Protection estimates that two nuts a day add about 160 microsieverts of radiation a year for an adult, against an average of about 2,100 from natural background.41

Do Brazil nuts lower cholesterol?

They may help. In a randomized trial of 17 teenage girls with obesity, 3 to 5 nuts a day for 16 weeks lowered total cholesterol, triglycerides and oxidized LDL compared with placebo, and oxidized LDL also fell in a trial of 91 adults in which each person tried both.21 22

Are Brazil nuts good for weight loss?

They fit well into a weight-loss plan. In a randomized trial of 40 women at cardiometabolic risk on a reduced-calorie diet, 15 grams of Brazil nuts (about three) plus 30 grams of cashews a day for 8 weeks lowered body-fat percentage by 1.3 points and improved lean-mass percentage compared with the same diet without nuts, and across 55 randomized trials of nuts in general, eating nuts didn't lead to weight gain.47 48

Are Brazil nuts good for men?

Yes, for their selenium, a mineral essential for healthy reproduction in men. Brazil nuts are the richest known food source of it, though no study has tested the nuts themselves on testosterone or sperm. In the testes, the selenium enzyme GPx4 protects developing sperm and is part of the structure around the sperm's mitochondria, which power its movement, and selenoprotein P delivers selenium there.30 6

Can you eat Brazil nuts while pregnant or breastfeeding?

Yes, one to two a day, the same as everyone else. Count any selenium in your prenatal toward the adult daily limit, which applies in pregnancy and breastfeeding too; it's in the table in the how-many section.34 35

Are Brazil nuts better than a selenium supplement?

They worked as well in head-to-head trials. In a 12-week randomized trial, two nuts a day raised blood selenium as much as a 100 mcg selenomethionine supplement and raised glutathione peroxidase more, and in a 2025 randomized trial of 86 adults, Brazil nut butter raised blood selenium as well as a supplement with the same selenium.5 12 A supplement gives you a fixed dose, so in my protocol you choose one or the other, not both.4

Should you eat Brazil nuts raw or soaked?

Either works. Soaking nuts in water and then drying them at low heat makes them easier to digest, the method The Biblio Diet recommends for nuts and seeds.8

Do Brazil nuts go bad?

Yes. Their unsaturated fat turns rancid with heat, light and air, so store them airtight in the refrigerator or freezer, and throw out any that are shriveled, discolored, moldy or bitter-smelling, since spoiled nuts carry most of the aflatoxin.2 43

Can you eat Brazil nuts with a tree nut allergy?

Not unless your allergist has confirmed you tolerate them. Brazil nut allergy can cause anaphylaxis, and avoidance plus an emergency plan is the standard of care for tree nut allergy.44 45

Can you eat Brazil nuts with kidney disease?

Usually, in small amounts. Two nuts carry about 73 milligrams of phosphorus and 66 of potassium, and studies in dialysis patients, which had no comparison group, have given one nut a day for 3 months, but count them within your care team's phosphorus and potassium limits.2 1

Freshness & update log

What changed in this update (October 3, 2026) — Rewritten around Dr. Axe's recommendation of one to two Brazil nuts a day, replacing the earlier "one to six nuts" guidance, with a new section on why the selenium in a single nut varies so widely and a single table of daily selenium limits by age. Added a Dr. Axe Score with its calculation; named, labeled human studies on selenium status, glutathione peroxidase, thyroid antibodies and thyroid hormones, inflammation, cholesterol and oxidized LDL, cognition and type 2 diabetes; two charts; a step diagram of how the nut's selenium reaches your enzymes; the levothyroxine timing note; and sections on radium, aflatoxin and Brazil nut allergy. Removed the anti-cancer, mood, bone and gut-health claims and the Brazil nut milk recipe, which used 2 cups of nuts a batch; replaced the plant-family allergy note with the documented Brazil nut allergen; corrected nutrient values against USDA FoodData Central; and moved the bottom line above the FAQ.

References

Dr. Josh Axe, DC, DNM, CNS

Doctor of Natural Medicine · Founder, DrAxe.com

Dr. Axe is a certified doctor of natural medicine, clinical nutritionist, and multiple New York Times bestselling author. He has spent 20+ years in clinical practice helping people heal at the root cause and founded one of the most-visited natural-health platforms in the world.

Read the full bio →

This article is for educational purposes. See our medical disclaimer.

On this page

What are they?
Nutrition facts
Selenium per nut
What are they good for?
How they work
Benefits, ranked
Thyroid
Key compounds
How many a day
Eat, buy & store
Vs. other nuts
Side effects & safety
The bottom line
Should you eat Brazil nuts?
FAQ

Quick facts

Daily amount1 to 2 nuts (Dr. Axe's recommendation)
One nut (5 g)About 33 calories and, on USDA's long-standing average, 175% of the daily value for selenium
Also rich inCopper, magnesium, phosphorus and thiamin
Best forSelenium status, antioxidant enzymes and thyroid support
Be careful withTree nut allergy; stacking nuts on a selenium supplement
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