I have been asked many times over the years about the safety of peanut butter due to aflatoxin, a carcinogen that is produced by a mold that can grow on peanuts. After a bit of digging I came up with some information that may be helpful.
First, aflatoxin is a naturally-occurring toxin that can contaminate a variety of common crops including cereals (such as corn and wheat), oil seeds (including peanuts), spices and tree nuts. It is also found in the milk of animals given contaminated feed. This toxic substance can contaminate crops before harvest and during storage. Crops with prolonged exposure to a hot, humid environment or that are damaged due to stressful growing conditions such as drought are more susceptible to aflatoxin contamination.
Aflatoxin can cause a number of liver problems including liver cancer and aflatoxicosis is influenced by age, sex, nutritional status, and health as well as both the level and duration of exposure to the toxin. The FDA has established safe levels of aflatoxin for both human food (20 parts per billion) and animal feed (up to 300 ppb) and both peanuts and products made from them are tested regularly. According to the USDA website no cases of aflatoxicosis have been reported in the U.S. – only in third world countries.
Interestingly, some research shows that eating are regular diet that includes apiaceous vegetables such as carrots, celery, parsnips, parsley (and a number of herbs and spices) can decrease the carcinogenic effects of aflatoxin. Good news for the “ants in a log” fans (celery stuffed with peanut butter and raisins)! There is also research that demonstrates chlorophyll (a green pigment that occurs in plants and algae) can reduce the absorption of aflatoxin in humans. http://www.news-medical.net/news/20091230/Chlorophyll-and-chlorophyllin-effective-in-limiting-aflatoxin-absorption-in-humans.aspx?page=2
According the Dr. Andrew Weil’s website the Consumers Union investigated aflatoxin levels in several brands of peanut butter sold in the U.S. (early 2000’s?) and found the major brands such as Peter Pan, Jif and Skippy had less than the fresh peanut butter sold in health food stores. I have also seen recommendations not to purchase bulk grains, nuts and seeds to avoid the possibility of contamination though there is no proof the bulk varieties pose a problem.
In general, keeping nuts, nut butters, seeds, and grains that you don’t use quickly in the refrigerator or freezer may be a good practice to prevent the hot, moist environments that favor aflatoxin growth. Other advice includes: avoid eating nuts that look moldy, discolored or shriveled – perhaps an obvious choice for most of us. The recommendation to choose only major brands of peanut butter is conservative but may put anxious parents at ease…though there are added sugars and trans fats to consider in some of these choices.
All things considered, I love peanut butter – and many of the other whole, nutritious foods that are susceptible to aflatoxin, and this new information is not enough to make me forego these foods. Given the amount of peanut butter the average American eats (especially kids) if this were truly a major public health issue I think we’d know about it beyond the random articles published in cyberspace. I do keep all of my nuts, seeds and nut butters in the fridge or freezer (they stay fresher that way – aflatoxin or not) along with grains such as corn meal and whole wheat flour that I use in baking (mainly because I don’t bake often). I also eat a variety of vegetables and herbs and spices regularly – with carrots and all kinds of green stuff as staples in my diet, so I guess I’m covered if these plants actually do end up being protective. As always, I believe in balance.