Q: You didn’t discuss aflatoxin in your article on nut butters. Should I be concerned about it?
A: No. Peanuts sold in the U.S. are not considered a problem. Still, you should keep them in a cool, dry place and avoid any that are moldy, shriveled, or discolored.
Produced by the mold Aspergillus flavus, aflatoxin can occur in nuts, legumes, seeds, corn, wheat, and other crops and in some spices (such as chili and paprika). Extreme heat and drought before harvest, as well as moist, humid storage conditions, increase susceptibility. This naturally occurring toxin can cause serious liver damage in humans and is a liver carcinogen.
Aspergillus is widespread in nature, found in soil, hay, and decaying vegetation. But farmers and food processors minimize its growth by following good management practices. Moreover, the USDA monitors peanuts for aflatoxin, while the FDA routinely samples peanut products to make sure they don’t exceed maximum allowable levels. Though some experts are concerned about chronic low-level exposure to aflatoxin, the small amounts commonly consumed in the U.S. pose little risk, according to the FDA.
Aflatoxin is a bigger threat in developing countries, such as Kenya, where outbreaks of acute poisoning (aflatoxicosis) have occurred and where high intakes of aflatoxin have been linked to liver cancer. There have been no reported cases of aflatoxicosis in the U.S.
Also see Heavy Metals in Juice: What to Know.
Originally published November 2012. Updated June 2019. This updated version also appeared in the June 2019 UC Berkeley Wellness Letter.