Are Brazil Nuts Really Healthy?—Behind the "Selenium Powerhouse," How Much Barium and Radium Enter the Body (Latest Research)

2026年01月06日
Are Brazil Nuts Really Healthy?—Behind the "Selenium Powerhouse," How Much Barium and Radium Enter the Body (Latest Research)

1. The reason Brazil nuts are said to be "good for health" is primarily due to selenium

Brazil nuts (Bertholletia excelsa), primarily sourced from the Amazon region, are known as "nutrient-dense seeds" rich in lipids (including unsaturated fatty acids), proteins, and minerals. They are particularly famous for their exceptionally high content of the essential trace element **selenium (Se)**.Phys.org+2MDPI+2


Selenium serves as a component of several "selenoproteins" in the body, playing roles in regulating oxidative stress, thyroid hormone metabolism, and immunity.Office of Dietary Supplements+1

An article on Phys.org also mentions that "one nut can cover the recommended amount (55-70 µg/day)."Phys.org



2. But there are "concerns": Barium and radioactive radium

On the other hand, it has long been known that Brazil nuts may contain not only nutrients but also "undesirable elements" such as **barium (Ba) and radioactive radium (Ra)**.Phys.org+1

Why do such elements get included? The research team explains that in tropical soils of the production area, which may be deficient in calcium, chemically similar elements (such as barium and radium) could partially replace calcium in plants.Phys.org+1

The issue is not just "whether they are present," but how much they dissolve during digestion and the potential for them to enter the body.



3. Key point of the new research: Measured the "percentage dissolved during digestion" which is more important than concentration

The current study (by teams from HZDR and VKTA in Germany) evaluated the **in vitro (test tube) digestion and bioaccessibility (the percentage released and potentially absorbed during digestion)** of multiple elements contained in Brazil nuts.Phys.org+1


Specifically, they used artificial saliva, gastric juice, digestive enzymes, etc., to process the nuts step by step under body temperature conditions to measure "how much dissolves." Element concentrations were analyzed using mass spectrometry (such as ICP-MS), radioactive isotopes with gamma and alpha spectroscopy, and chemical speciation with NMR and laser fluorescence methods.Phys.org+1



4. Result ①: Selenium "dissolves quite a lot" — about 85% is released during digestion

This is the main conclusion.

  • About 85% of selenium is released during digestion (= potentially absorbed by the body)Phys.org+1

  • The main form of selenium is the easily absorbable amino acid type selenomethionine (SeMet)Phys.org+1


The idea that "Brazil nuts are high in selenium" has been said for a long time, but this study supports it by showing "how much is actually available for use."



5. Result ②: Barium and radium "barely dissolve" — about 2%

Next, the concerns about barium and radium. The study found that,


In other words, "even if they are not zero, the amount that dissolves and can be absorbed during digestion is very small."

Phys.org's explanation suggests that components like **phytic acid** may strongly bind minerals and metals, inhibiting their absorption.Phys.org



6. How much "radiation dose"? Estimated at 2.4 µSv per year for one nut a day

According to the Phys.org article,the estimated additional exposure from "one nut a day" is about 2.4 µSv per year, which is about 1/1000th of the average natural radiation in Germany (2.1 mSv per year).Phys.org+1


To clarify the units,

  • 1 mSv = 1000 µSv


Therefore, 2.1 mSv per year is equivalent to 2100 µSv per year, and 2.4 µSv is indeed a very small value.

Furthermore, the BfS (Federal Office for Radiation Protection in Germany) indicates that natural radiation is about 2.1 mSv per year on average.bfs.de
They also have a page explaining natural radioactive nuclides in Brazil nuts.bfs.de



7. Result ③: What about other trace elements (strontium, lanthanum, europium)?

The study also evaluated strontium (Sr), which has properties similar to calcium, and the rare earth elements lanthanum (La) and **europium (Eu)**.


  • Strontium: Bioaccessibility is about 50%, but the content is small and not toxicologically significantPhys.org+1

  • Lanthanum/Europium: Detected in trace amounts, bioaccessibility is about 25%, but intake is well below standard valuesPhys.org+1

In summary, "aside from selenium, even if the dissolution rate is somewhat high, the actual amount is small."



8. "Interesting side path" of the research: Also examined the impact on chelating agents for radioactive substances

What makes this research unique is that it not only looks at food safety but also examines whether components derived from Brazil nuts affect the efficacy of decorporation agents.


Using chelating agents like EDTA, DTPA, and newer candidate compounds (3,4,3-LI(1,2-HOPO)), they investigated the influence of food matrices (Brazil nut powder) and reported that the impact is small.MDPI+1

Although this is somewhat removed from general dietary habits, the strength of this research lies in its chemical perspective on "how elements bind and move within the body."



9. Important point: More selenium is not "better" (guidelines for consumption)

While this study suggests that "the risk of harmful elements may be smaller than expected," it also seems to remind us not to forget the risk of selenium overdose.


Selenium has a narrow margin between the necessary amount and the upper limit, and chronic overconsumption can lead to selenosis (hair loss, nail abnormalities, gastrointestinal symptoms, changes in breath odor, etc.).Office of Dietary Supplements+2Office of Dietary Supplements+2

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