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Peanut butter is a staple in American households. It is used in cookies and pies, between crackers and in the ubiquitous peanut butter and jelly sandwich. Highly portable, delicious and containing numerous health benefits, peanut butter has been a popular choice for many years. Like any food, though, it is important to pay attention to the expiration date on the jar. Eating peanut butter in general can be dangerous because of the potential for salmonella, but the dangers increase after the expiration date mainly due to aflatoxin, resveratrol breakdown and general rancidness.


Aflatoxin, a potential carcinogen produced from the mold Aspergillus flavus, is present in peanuts and peanut butter and can be present during nut storage or even before the peanut is harvested. The FDA strictly measures the amount of aflatoxin in peanut butter. The lowest amounts are found in name brands peanut butters. Aflatoxin can be present in greater quantities after the peanut butter has expired, so it is important to consume it or dispose of it by the expiration date. Aflatoxins can cause liver cancer or liver disease in humans.


Salmonella can be a problem whether the peanut butter is outdated or not. Usually linked with eggs, salmonella prospers in fatty foods such as peanut butter. Once there, it can survive for months. The good news is roasting the peanuts will kill salmonella, and most major peanut butter brands use roasted peanuts in their recipes. However, once salmonella gets into the peanut butter, there is no way to remove it without compromising the product. Though salmonella can be harmful in peanut butter regardless of the expiration date, it is common sense to use peanut butter in a timely fashion to decrease any potential risks.


Resveratrol is an active nutrient found in peanuts that is harmless to humans. It’s anti-fungal and anti-microbial properties help combat pathogens in our system. Resveratrol has proven to be very beneficial to mice and is believed to be so for humans as well, though human tests have not been performed. Like most supplements, potency dwindles after a certain time period, thus it is better to eat the peanut butter before it gets rancid.


Peanut butter has a high fat content, which means it will go rancid after a certain amount of time. Eating rancid peanut butter may result in stomachache, diarrhea or vomiting. To prevent this, peanut butter should be stored in the refrigerator, away from heat and humidity and eaten before the expiration date.