Aflatoxin in Cashews
All nuts, including cashews, can become contaminated by aflatoxins, toxic compounds that have been linked to everything from liver cancer to impaired growth in children. The good news is that the levels of aflatoxins in cashews are generally much lower than the levels of aflatoxins in peanuts which are known to be highly susceptible to contamination by these naturally occurring toxins produced by certain fungi. What's more, if you live in a developed country, your risk of ingesting high levels of aflatoxins from cashews is generally very low because most developed countries have set standards for acceptable levels of aflatoxin in cashews.
Governments Control the Level of Aflatoxin in Cashews
The U.S. Food and Drug Administration has set the maximum allowable level of aflatoxins at 20 ppb for all foods, including cashews (1). If a lot of cashews contains higher levels, it won't be allowed for sale for human consumption. Up north, the Canadian Food and Drug Regulations specify a tolerance of 15 mcg/kg (15 ppb) total aflatoxins in nut and nut products such as whole cashews and cashew butter (2).
In the member states of the European Union, the regulations with regard to how much aflatoxin cashews can contain in are even stricter: if cashews contain more than 4 mcg/kg (4 ppb) of aflatoxins in total, they cannot be sold for direct human consumption. What's more, the European Commission has set a separate maximum limit of 2 mcg/kg (2 ppb) for aflatoxin B1 in cashews because this type of aflatoxin is considered to be particularly toxic. (3)
Cashews Are Not Particularly Prone to Aflatoxin Contamination
Several studies that have compared the levels of aflatoxin in different nuts suggest that cashews are not particularly susceptible to contamination by aflatoxins. The Canadian 2010-2011 Aflatoxin Survey, which analyzed 250 samples of nuts and nut butters, found no detectable levels of aflatoxin in any of the cashew samples. Many other nut samples, however, did contain detectable levels of aflatoxins (4).
Also another large-scale study, conducted in Cyprus in the 1990s, found no aflatoxins in cashews. This was not the case for most of the other nuts that were tested: several samples of Brazil nuts, pistachios, walnuts, peanuts, and chestnuts contained detectable levels of aflatoxins, with the highest levels of aflatoxin B1 found in peanuts (5)
In yet another study, researchers collected 90 nut samples from a local market in Tripoli, Libya, and determined their aflatoxin content using the high-performance liquid chromatography technique. Among the tested nuts, cashews had the lowest incidence of aflatoxin contamination: only 13 percent of the cashew samples contained detectable levels of aflatoxins. (6)
Tips for Keeping Your Cashews and Cashew Butter Aflatoxin-Free
Now, even though cashews don't appear to be particularly prone to contamination by aflatoxin, it is still a good idea to store your nuts in a dry and cool place, and eat them fast. The fungi that produce aflatoxins love warmth and humidity, and by storing your cashews properly, you can greatly reduce the risk of your nuts developing aflatoxins in the cupboard.
What's more, if you don't plan on eating your cashews right away, you may want to consider freezing them. Freezing cashews couldn't be easier: simply put them freezer-safe containers, and place the containers in the freezer.
Finally, if you like freshly-made cashew butter, it may be better to make your own cashew butter in a blender designed to make nut butters than to use one of those do-it-yourself nut butter machines you see in health food stores. The DIY nut butter machines in the stores can easily get contaminated with aflatoxins if they are not cleaned regularly, plus the nuts may have been sitting in the container for a long period of time.
Sources:
1. 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.
2. List of Contaminants and other Adulterating Substances in Foods. Government of Canada. Last accessed: January 2018.
3. 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.
4. 2010-2011 Aflatoxins in Dried Fruits, Nuts and Nut Products, and Corn Products. Canadian Food Inspection Agency. Last accessed: January 2018.
5. 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.
6. N. Essawet et al (2017). Natural Incidence of Aflatoxins and Ochratoxin A Nuts Collected from Local Market in Tripoli. International Journal of Current Microbiology and Applied Sciences, 6(3), 1479-1486.
