Brazil Nuts: Nutrients, What Research Shows and Safety

Brazil nuts are the seeds of the Brazil nut tree, Bertholletia excelsa (family Lecythidaceae), which grows wild in the Amazon rainforest. The part eaten is the kernel inside a hard shell, and the nuts are sold in the shell, shelled, blanched, or as butter, flour and oil. [6] People eat them mostly for selenium, an essential trace mineral. This page keeps the food apart from supplements and oils, and apart from hype.

Read this first

• Selenium is the main safety point. USDA lists about 543 micrograms (mcg) of selenium in a 1 ounce (28 g) serving of about 6 kernels. [1] That is more than the US and Canadian upper limit for adults (400 mcg a day) and more than the EU limit (255 mcg a day). [2] [3] The upper limit covers selenium from food and supplements together. It is an official safety ceiling, not a target.
• The selenium in one nut varies a lot. A study of Amazon trees found a single nut could supply from 11% to 288% of a 70 mcg daily requirement, depending on the region. [6] Because you cannot tell how much a given nut holds, this page cannot give a "safe number of nuts." Ask a clinician or pharmacist, especially if you take a selenium supplement.
• Allergy: Brazil nut is a tree nut. Tree nut allergies are often severe and can last a lifetime. For trouble breathing or swelling of the face, lips or throat, call 911 (or your local emergency number). [10] [11]
• Young children: whole and chopped nuts are on the CDC list of choking hazards for young children. [12]
• Evidence in one line: trials show Brazil nuts raise blood selenium. Evidence for any disease benefit is limited or missing.

What is in it (USDA values)

The values below are for dried, unblanched Brazil nuts (USDA FoodData Central item 170569, SR Legacy). [1] The serving column is the USDA household portion of 1 ounce, 28.35 g, about 6 kernels. [1]

% Daily Value uses the FDA 2016 Daily Values; values vary with variety, growing place, roasting and storage. The serving figures are the 100 g values multiplied by 0.2835. USDA lists one kernel as 5 g, which is about 96 mcg of selenium by the USDA average. [1] Real nuts differ widely from that average. [6] Brazil nuts are not a notable source of ALA omega-3: the USDA value is very small. [1]

Plant compounds: lab analyses of Brazil nut oil report phenolic compounds (including gallic acid derivatives) and plant sterols such as beta-sitosterol. This is laboratory chemistry, and we did not find a trial showing these compounds act in people when the whole nut is eaten. [16]

What research says

Studies of selenium supplements are a separate question. For the large SELECT trial and for the limits, see selenium toxicity, Brazil nuts and upper limits. We did not check funding in every study; abstracts often do not say.

Eaten as food vs taken as oil, extract or supplement. The trials above used whole nuts or nut butter. Brazil nut oil, flour and selenium tablets are different products. Selenium in the food form and in supplements both raise blood selenium, [8] and both count toward the same upper limit. [2]

How much is a normal serving

The USDA household portion is 1 ounce (28.35 g), about 6 kernels, which has about 187 kcal. [1] That is information from the USDA data, not a prescription. For Brazil nuts, the selenium in this portion is above the adult upper limits. [1] [2] [3] The sources we read do not give an official safe count of nuts, because the content varies by origin. [6] NHS says people who eat meat, fish or nuts should get enough selenium from food, and that 350 mcg or less a day from supplements is unlikely to cause harm. [4] Calories matter too: nuts are energy dense, and we did not read a Brazil-nut-specific weight study.

Safety, allergy and medicines

• Too much selenium (selenosis): the mildest signs are hair and nail loss; MedlinePlus also lists nausea, irritability, fatigue and mild nerve damage. [4] [5] EFSA based its adult limit of 255 mcg a day on hair loss seen at 330 mcg a day in the SELECT trial, and said regular Brazil nut eaters are among the adults who may exceed it. [2]
• Official limits: 400 mcg a day for people 14 and over (Health Canada 2025), including pregnancy and breastfeeding; lower for children: 90 mcg ages 1-3, 150 ages 4-8, 280 ages 9-13. [3] EFSA (2023) sets 255 mcg for adults. [2] EFSA also advises caution with selenium supplements for children. [2]
• Recommended intake: 55 mcg a day for adults, 60 in pregnancy and 70 while breastfeeding (MedlinePlus, 2025). [5] The pilot trial's one nut a day was estimated at 288.75 mcg, above the EFSA limit, so do not treat that trial as advice. [7]
• Allergy: tree nut and seed allergies are often severe and may persist through life; prevalence is rising. Overlap between tree nuts exists, with cashew-pistachio and walnut-pecan the best known. [10] Peanut is a legume, not a tree nut, and is a separate allergy. See nut and seed allergy basics. Avoiding the food is the only prevention. Epinephrine treats anaphylaxis, and 911 should be called. [11]
• Medicines and health conditions: we did not find a source we could read describing a direct interaction between Brazil nuts as food and a specific medicine. The sibling selenium page notes the chemotherapy medicine cisplatin can lower selenium levels; ask the care team about all supplements. See selenium toxicity page and supplements and thyroid medicines. People with kidney disease should ask a clinician about nuts, as the available trials are small. [15]
• Choking: the CDC lists whole or chopped nuts, and spoonfuls of nut butter, as choking hazards for young children. [12]
• Mold and aflatoxin: WHO names Brazil nuts among foods frequently affected by aflatoxins, which can cause liver damage and are linked to liver cancer. [13] A 2025 study of Brazil nuts harvested in a severe drought found aflatoxin in every sample and levels above the 10 mcg per kg legal threshold in 10% of them. [14]

Choosing, storing and food safety

• WHO advises inspecting nuts and throwing away any that look moldy, discolored or shriveled. [13]
• Buy nuts as fresh as possible and store them dry, cool and not for long periods. [13]
• We did not read a source with specific advice on Brazil nut rancidity or freezing. See storing nuts and seeds.

Related pages

• Selenium toxicity, Brazil nuts and upper limits
• Other tree nuts: pecans, cashews, Brazil nuts and macadamias
• Nuts and seeds for heart health: what trials found
• Food allergy basics and emergency signs
• Foods for babies and toddlers: choking, honey and allergens
• Nut and seed allergy basics