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Aflatoxin in Peanuts and Peanut Butter

Aflatoxins are toxic substances that are primarily produced by two types of mold: Aspergillus flavus and Aspergillus parasiticus. Virtually any plant-based food can become contaminated with aflatoxins if stored improperly, but peanuts seem to be particularly susceptible to contamination by these mycotoxins. The ability of aflatoxins to cause cancer is well-documented, but these toxic compounds have also been linked to a wide range of other diseases and health problems including impaired immune function, cardiovascular problems, nutrient deficiencies, gastrointestinal problems, and growth impairment in children. Many different types of aflatoxins can contaminate in peanuts, with aflatoxin B1 being the most dangerous type.

To protect us from the harmful effects of aflatoxins, governments in developed countries have established strict food safety guidelines and regulations to keep the aflatoxin levels in peanuts and other susceptible foods as low as possible. In addition, by choosing peanut products carefully and storing them properly consumers can greatly reduce their risk of exposure to aflatoxin-contaminated peanuts.


Aflatoxin Levels in Peanuts and Peanut Butter

When it comes to foods that may contain high levels of aflatoxins, peanuts are right there on top of the list (1-3). As peanuts are also one of the most popular nuts consumed in the United States and Europe, governments have put great effort into controlling aflatoxin levels in peanuts. The U.S Food and Drug Administration has established a set of guidelines and regulations designed to reduce exposure to aflatoxins from peanuts. It has also set a maximum permissible level for aflatoxin at 20 parts per billion (ppb), but this limit applies to all foods, not just peanuts and peanut butters. (4).

In most European countries, including the UK, the maximum permissible level of aflatoxins for peanuts and peanut butter is even lower: if peanuts or peanut butter contain more than 4 micrograms of aflatoxins per kilogram (4 ppb), they cannot be sold for direct human consumption. What's more, as aflatoxin B1 has been found to be particularly toxic, the European Commission has set a separate maximum limit of 2 mg/kg for aflatoxin B1 allowed in peanut and peanut butter. (5)

The Link Between Aflatoxins and Liver Cancer

The health effects of aflatoxins have been extensively researched since the 1960s. One of the best-documented health effects associated with consumption of aflatoxin-contaminated foods is the increased risk of liver cancer, and the International Agency for Research on Cancer has classified aflatoxin as a Group I Carcinogen (6).

Most studies on aflatoxins and cancer have focused on hepatocellular carcinoma (HCC), which is the most common type of primary liver cancer in adults, the fifth most common cancer overall, and the third most common cause for cancer death in the world. It is also a major cause of death in people with chronic hepatitis C virus infection (7).

Other Health Effects

In addition to being capable of causing cancer, aflatoxins may cause cardiovascular problems, immune suppression, nutrient deficiencies, gastrointestinal problems, stunted growth in children, and a wide range of other health problems. In poor, tropical countries where the climate is suitable for rapid mold growth on crops and where there are no strict regulations to govern aflatoxin levels in peanuts and other foods, acute aflatoxin poisoning also poses a public health risk. Signs and symptoms of acute aflatoxin poisoning include abdominal pain, vomiting, excess fluid in the lungs, fatty liver, and necrosis of the liver (8).

How to Minimize Your Exposure to Peanut Aflatoxins

Despite the FDA's best efforts to keep the amount of aflatoxins in peanuts below dangerous levels, contaminated peanuts sometimes make their way into the food supply, and products have to be recalled. From 2001 to 2017, there were several recalls resulting from peanut butter products containing aflatoxin above the allowable limits (9).

Peanuts and peanut butter can also get contaminated with aflatoxins during storage.

Luckily, there are a number of things you can do to reduce your risk of ingesting contaminated peanuts. Here are some suggestions:

  • Buy peanuts and peanut butter from companies who take aflatoxin contamination seriously. The nut butter producer MaraNatha, for example, states on its website that their peanut butters are virtually aflatoxin-free because in addition to FDA-mandated tests, they perform random tests on their products. (You can buy MaraNatha peanut butter here.)
  • Always store your peanuts in a dry, cool place. The fungi that produce aflatoxins thrive in warm, humid environments.
  • Consider freezing your peanuts if you don't plan on using them right away.
  • Make sure your diet contains plenty of vitamin C rich foods. Laboratory and animal studies suggest that vitamin C may provide some protection against the harmful effects of aflatoxins.
  • The do-it-yourself peanut butter machines you see in health food stores are susceptible to aflatoxin contamination if the machines are not thoroughly cleaned regularly and the peanuts are allowed to sit in them for longer periods of time. If you like the flavor of freshly-ground peanut butter, get a food processor or blender that makes peanut butter, and grind your own peanut butter at home.

1. Government of Canada. 2010-2011 Aflatoxins in Dried Fruits, Nuts and Nut Products, and Corn Products. Canadian Food Inspection Agency.
2. E. Ioannou-Kakouri et al (1999). Surveillance and control of aflatoxins B1, B2, G1, G2, and M1 in foodstuffs in the Republic of Cyprus: 1992-1996. Journal of AOAC International, 82(4):883-92.
3. Aflatoxins: Occurrence and Health Risks. Cornell University, College of Agriculture and Life Sciences. Last accessed: January 2018.
4. Guidance for Industry: Action Levels for Poisonous or Deleterious Substances in Human Food and Animal Feed. U.S. Food and Drug Administration Last accessed: January 2018.
5. EU Commission Regulation (EC) No 1881/2006 of 19 December 2006 setting maximum levels for certain contaminants in foodstuffs, amended by Commission Regulation (EU) No 165/2010 published on February 27, 2010.
6. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. List of Classifications, Volumes 1-120; accessed on December 28, 2017 International Agency for Research on Cancer, World Health Organization.
7. L. de Oliveria Andrade et al (2009). Association Between Hepatitis C and Hepatocellular Carcinoma. Journal of Global Infectious Diseases, 1(1): 33-37.
8. C. Wild, J. Miller and J. Groopman (2015). Effects of aflatoxins on aflatoxicosis and liver cancer. IARC Working Group Reports, No. 9.
9. M. Palumbo et al (2017). Recalls of tree nuts and peanuts in the U.S., 2001 to present [Table and references]. UC Davis.