How many Brazil nuts a day is too much?
About 4 Brazil nuts a day reach the adult upper limit for selenium from NIH, 400 mcg a day from food and supplements together, going by the USDA record of 96 mcg in one 5 g nut. Batches differ a lot: another USDA record finds about a seventh of that, while in one trial 8 g of Brazil nuts, less than two nuts, supplied 347.2 mcg. One nut a day, the amount one trial used, stays under the adult limit with every figure on this page.
Where the limits are
| What sets the limit | Per Brazil nut | Daily limit for adults | Brazil nuts to reach it (rounded down) |
|---|---|---|---|
| Selenium | 96 mcg | 400 mcg (Upper limit (NIH)) | 4 |
| Saturated fat | 0.8 g | about 20 g (10% of 2,000 calories) (Dietary Guidelines limit) | 24 |
| Calories | 33 | 2,000 (reference day, not a limit) | 60 |
One Brazil nut = 1 kernel (5 g). USDA FoodData Central, Nuts, brazilnuts, dried, unblanched. Limits count everything you eat and drink that day, so other foods and supplements use up part of each one.
What 1 to 6 Brazil nuts a day add up to
| Amount | Calories | Selenium (% of limit) | Saturated fat (% of limit) |
|---|---|---|---|
| 1 Brazil nut | 33 | 96 mcg (24%) | 0.8 g (4%) |
| 2 Brazil nuts | 66 | 192 mcg (48%) | 1.6 g (8%) |
| 3 Brazil nuts | 99 | 288 mcg (72%) | 2.4 g (12%) |
| 4 Brazil nuts | 132 | 383 mcg (96%) | 3.2 g (16%) |
| 6 Brazil nuts | 198 | 575 mcg (144%) | 4.8 g (24%) |
How much selenium differs between USDA records
| USDA record | Per 100 g | Per Brazil nut | Brazil nuts to the limit |
|---|---|---|---|
| Nuts, brazilnuts, dried, unblanched (FDC 170569) | 1,917 mcg | 96 mcg | 4 |
| Nuts, brazilnuts, raw (FDC 2515373) | 280 mcg | 14 mcg | 28 |
Each row is a separate USDA analysis of the same food. The spread comes from variety, growing conditions and sampling, and it changes the answer.
What eating it daily did in studies
- Level B In an RCT of 55 women with obesity and adequate selenium, one Brazil nut a day for 2 months raised selenium markers and inflammatory gene expression. Nutrition, 2019
- Level C In an 8-week controlled trial in 56 women with overweight, just 8 g of Brazil nuts a day supplied 347.2 mcg of selenium. J Nutr, 2024
Only studies that give the amount eaten. Levels: A is a meta-analysis of trials, B a randomized trial, C an observational study. How we grade evidence.
Reasons to keep it moderate, and who should eat less
- Level E NIH ODS says the most common signs of chronically high selenium intake are hair loss and brittle or lost nails, and sets the adult upper limit at 400 mcg a day. NIH Office of Dietary Supplements, Selenium Fact Sheet for Health Professionals
- Level E One Brazil nut holds 68 to 91 micrograms of selenium, and eating Brazil nuts regularly could cause selenium toxicity. NIH Office of Dietary Supplements, Selenium fact sheet for health professionals, snapshot 2026-09-21
If you have kidney disease, take blood thinners or other medicines, or are pregnant, the right amount for you is a question for your clinician.
What this means for a normal day
NIH puts one Brazil nut at 68 to 91 mcg of selenium, close to the USDA record of 96 mcg used here. That is why the count is so small: four nuts already sit near the 400 mcg adult upper limit, before any selenium from bread, eggs, fish or a multivitamin. For children and teens NIH sets lower limits, from 45 mcg upward by age, so the four-nut count is for adults only.
The most common signs of too much selenium over time are hair loss and brittle or lost nails, according to NIH (Level E). A trial that gave women one Brazil nut a day for two months raised their selenium markers (Level B).
The newer USDA analysis found far less selenium, 280 mcg per 3.5 oz (100 g). Other batches carry far more: in one trial, 8 g of Brazil nuts a day, less than two nuts at 5 g each, supplied 347.2 mcg, about 43 mcg per gram (Level C). You cannot see the difference on the shelf, and two nuts from a batch like that one would pass the 400 mcg limit.
Evidence behind this note
- Level E One Brazil nut holds 68 to 91 micrograms of selenium, and eating Brazil nuts regularly could cause selenium toxicity. NIH Office of Dietary Supplements, Selenium fact sheet for health professionals, snapshot 2026-09-21
- Level E NIH ODS says the most common signs of chronically high selenium intake are hair loss and brittle or lost nails, and sets the adult upper limit at 400 mcg a day. NIH Office of Dietary Supplements, Selenium Fact Sheet for Health Professionals
- Level E Chronically high selenium intake causes hair loss and brittle or lost nails, according to NIH, which sets the adult upper limit at 400 mcg a day. NIH Office of Dietary Supplements, Selenium Fact Sheet for Health Professionals
- Level B In an RCT of 55 women with obesity and adequate selenium, one Brazil nut a day for 2 months raised selenium markers and inflammatory gene expression. Nutrition, 2019
- Level C In an 8-week controlled trial in 56 women with overweight, just 8 g of Brazil nuts a day supplied 347.2 mcg of selenium. J Nutr, 2024
Written from the data and studies on this page, reviewed by the Bioma editorial system. How we verify.
Keep exploring
Sources
- USDA FoodData Central, SR Legacy (2018): Nuts, brazilnuts, dried, unblanched, FDC ID 170569 (accessed 2026-10-13)
- USDA FoodData Central, Foundation Foods (release 2025-12-18): Nuts, brazilnuts, raw, FDC ID 2515373 (accessed 2026-10-13)
- NIH Office of Dietary Supplements, Health Professional Fact Sheet: Selenium, https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/ (accessed 2026-10-13)
- Dietary Guidelines for Americans, 2025-2030, https://cdn.realfood.gov/DGA.pdf (accessed 2026-10-13)
- Evidence cards: each study above links to its source. Card review dates are listed in our methodology.
Numbers checked 2026-10-13. Bioma Learn provides information, not medical advice.