Brazil Nuts: The Selenium Poisoning Trap
One of the most dangerous nuts in your kitchen might be the innocent-looking Brazil nut. These large, tropical nuts contain highly concentrated amounts of selenium, with just one ounce (approximately 8 medium nuts) providing 544 micrograms of selenium, which is 777 percent of the recommended daily allowance. Eating too many Brazil nuts can lead to toxic levels of selenium in the body (selenosis) and cause symptoms such as bad breath, diarrhea, nausea, skin rashes/lesions, nerve pain and fatigue. In rare cases, very high levels can cause kidney failure, cardiac arrest and even death.
The shocking reality is that a 1-ounce serving (six to eight nuts) contains nearly 10 times the recommended daily amount of selenium (55 micrograms). Selenium poisoning can make your nails brittle, cause your breath to smell, and even trigger aching muscles and joints. She recommends eating only up to four Brazil nuts a day, and possibly dropping that to four every other day to err on the side of caution. What makes this particularly concerning is that most people don’t realize they’re putting themselves at risk with what they consider a healthy snack.
Pistachios: The Aflatoxin Champions
Pistachios had the highest levels of aflatoxin B1 among the tested products in a large Japanese study. No detectable levels are observed in 70–90% of samples of almonds, hazelnuts, peanuts, cashews, and “other nuts” analyzed in the EU, while the corresponding proportion of non-detectable levels for both pistachios and Brazil nuts is only 56%. The highest concentrations of aflatoxin B1 are also detected in these two nut types.
After peanuts, pistachios are at high risk of contamination by aflatoxin B1. The acceptable level of aflatoxins in pistachios is 10 ppb of total aflatoxins and 8 ppb of aflatoxin B1. It is the most dangerous type of aflatoxin. Even more alarming is that any discoloration on pistachio nuts or pistachio kernels may show aflatoxin infection. It is impossible to detect aflatoxin by tasting pistachios as it doesn’t affect the taste. This means you could be consuming dangerous levels of carcinogens without ever knowing it.
The European Commission and FDA have placed separate limitations on aflatoxin B1 because of its extreme toxicity, yet pistachios consistently fail to meet safety standards in various global studies.
Peanuts: The Aflatoxin-Riddled Pseudo-Nut
While technically legumes, peanuts are consumed like nuts and pose significant health risks. Despite the FDA’s best efforts to keep the amount of aflatoxins in peanuts and peanut butter below dangerous levels, there have been several recalls resulting from peanut butter products containing aflatoxin above the allowable limits in the US. To reduce your exposure to aflatoxins from peanuts, only buy high-quality peanuts and peanut butter that look and taste good, and store your peanuts in a dry, cool place.
The mean concentration of aflatoxin total (AFT) and AFB1 in peanuts were as follows: peanut (37.85, 32.82 μg/kg). In another study in Saudi Arabia, the concentration of AF in peanuts was 28 μg/kg. What makes peanuts particularly dangerous is their widespread consumption. Aflatoxin in peanuts are another major concern for the same reasons. Peanuts are consumed in high amounts in countries across Asia and also in the U.S.
Recent food safety alerts have shown that even major commercial brands can’t guarantee aflatoxin-free peanut products, with recalls due to the presence of biotoxin (aflatoxin) contamination occurring as recently as 2025.
Walnuts: The Moldy Contradiction
Walnut (90%) were the most contaminated samples with aflatoxins. 47.6% of walnut samples had aflatoxin contamination, which were more than the maximum tolerated level of Iran (MTL, 15 ppb). This finding is particularly disturbing given walnuts’ reputation as a superfood packed with omega-3 fatty acids.
The contamination issue with walnuts extends beyond just aflatoxins. The Canadian 2010-2011 Aflatoxin Survey, which analyzed 250 samples of nuts and nut butters, found aflatoxins in several types of nuts, including Brazil nuts, walnuts and peanuts. What’s most concerning is that walnuts are often consumed in larger quantities than other nuts due to their perceived health benefits, potentially increasing exposure to harmful toxins.
Storage conditions significantly impact walnut safety, and many consumers unknowingly purchase or store walnuts in ways that promote fungal growth and aflatoxin production.
Pecans: The Toxic Element Accumulator
We have observed that pecans were generally characterized by a high content of each of the toxic elements studied. All pecan samples were imported from the USA; however, there was no detailed information about the specific area of origin. This makes pecans uniquely dangerous among tree nuts.
The As levels in the studied material ranged from 13.48 µg/kg in one sample of the cashews to 314.52 µg/kg in the sample of pecans. Those pecans were imported from the USA. Additionally, like many other nuts, pecans contain a high percentage of fat and can lead to diarrhea if too many are eaten in a short amount of time. Over-consumption may also lead to digestive issues like gas and bloating.
In the group of nuts which was characterized by increased contents of studied elements were: macadamia nuts, peanuts, pecans, pine nuts and pistachios. The combination of toxic elements like arsenic, cadmium, lead, and mercury makes pecans a particularly risky choice for regular consumption.
Cashews: The Toxic Transformation
What most people don’t realize is that truly raw cashews are not safe to eat, as they contain a substance known as urushiol, found in poison ivy. Urushiol is toxic, and contact with it can trigger a skin reaction in some people. This means all “raw” cashews have been processed with heat or chemicals to remove this dangerous compound.
Side effects from eating cashews are very rare; however, regularly eating far more than the recommended amount may lead to digestive symptoms such as bloating or constipation/diarrhea, headache and joint swelling. Regularly eating far more than the recommended amount may lead to digestive symptoms such as bloating or constipation/diarrhea, headache and joint swelling. Keep in mind that about 20 percent of the fat content in cashews is saturated fat, which is much higher than most other nuts, so portion size is especially important.
While cashews appear to have lower aflatoxin contamination than other nuts, the processing required to make them safe for consumption involves potentially harmful chemical treatments that aren’t disclosed to consumers.
