Aflatoxin is the generic name for a family of natural poisons produced by the mold Aspergillus flavus, which grows on nuts and grains. Its toxicity became evident in 1960, when several flocks of commercially raised turkeys died from eating moldy peanut meal. Aflatoxin was found to be a potent liver carcinogen in lab animals.
In 1969, the U.S. Food and Drug Administration set an upper limit of 20 parts per billion (ppb) for aflatoxin in peanuts and peanut products. But that was based on economic considerations; it does not represent a negligible risk.
In Consumer Reports’ latest tests, every peanut butter brand had at least one sample with detectable aflatoxin. The average level in the 86 samples was 5.7 ppb. Seventeen samples had levels above 10 ppb, and one contained 20 ppb.
This time, there were striking brand-to-brand differences. None of the 14 samples of the “big three” national brands (Jif, Skippy and Peter Pan) contained more than 1 ppb of aflatoxin. Neither did any samples of Smucker’s. By contrast, more than half of the store-brand and regional samples tested contained 5 ppb or more. Worst by far were fresh-ground peanut butters bought in one supermarket and two health-food stores. They all averaged more than 10 ppb.
How risky is it to eat peanut butter? Assuming an average aflatoxin level of 2 ppb and an intake of one peanut butter sandwich every 10 days, the lifetime risk might be seven cases of cancer per million consumers. If, over your lifetime, you eat more peanut butter than that, or if the peanut butter you eat contains more aflatoxin, your risk would be higher.
These risks are larger than consumers usually are willing to accept from toxic residues in food. The aflatoxin risk is about as big as was the risk from daminozide (Alar) in apple products. And it’s much bigger than the risks for most pesticide residues.
