Aflatoxin in Brazil Nuts (and How to Reduce Your Exposure)
All nuts, including Brazil nuts, are susceptible to contamination by molds that produce a mycotoxin called aflatoxin. Not only has this toxic substance been on the World Health Organization's list of human carcinogens for a long time, it has also been linked to liver damage, digestive problems, growth and development impairment, reproductive problems, and food allergies.
The good news is that in developed countries such as the United States and the members of the European Union, the risk of you ingesting high amounts of aflatoxins from one serving of Brazil nuts is very low because authorities in these countries have set standards for acceptable levels of aflatoxin in nuts such as Brazil nuts. If the aflatoxin content of a sample of Brazil nuts exceeds is 20 parts per billion (ppb), the lot won't be allowed for sale for human consumption in the United States.
The regulations in Europe are even stricter: if a sample of ready-to-eat Brazil nuts contains more than 10 micrograms of aflatoxins per kilogram (or 10 ppb), the lot won't be allowed for sale. The European Commission has also set a separate maximum limit for aflatoxin B1 allowed in Brazil nuts because this type of aflatoxin has been found to be particularly dangerous. If a sample of Brazil nuts contains more than 5 micrograms of aflatoxins per kilogram, the lot cannot be sold for direct human consumption.
Now, while the measures taken by the U.S. Food and Drug Administration and the European Commission are comforting, it is important to be aware that Brazil nuts can also become contaminated with aflatoxin during storage. Aflatoxin is produced by two types of mold, Aspergillus flavus and Aspergillus parasiticus, and these molds thrive in warm and humid conditions. Therefore, you should always store your Brazil nuts in a dark and cool place, and consume them fast. You may also want to consider freezing your Brazil nuts if you don't plan on using them within a couple of months. Freezing nuts is a great way to extend their shelf life!
When selecting Brazil nuts, avoid nuts that look damaged, moldy or discolored. Your taste buds are also a great indicator: if you think the nuts taste moldy, they probably contain mycotoxins such as aflatoxin.
It may also be worth looking out for in-shell Brazil nuts. A Canadian study using Brazil nuts imported from Peru found that shelled Brazil nuts nuts were more likely to become contaminated with aflatoxins than in-shell Brazil nuts. Published in the Journal of Stored Products Research, this study also found that shelled half-nuts – simulating damaged or trimmed nuts – were more likely to develop aflatoxins than shelled whole nuts.
Finally, laboratory and animal studies suggest that vitamin C may help counteract some of the harmful effects of aflatoxins, so make sure your diet contains enough foods rich in vitamin C. Oranges may be the most famous natural source of vitamin C, but in fact, many other common foods contain much more vitamin C than oranges (the vitamin C content of kiwi fruit, for example, is twice as high as that of fresh oranges).
Sources:
1. 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.
2. Guidance for Industry: Action Levels for Poisonous or Deleterious Substances in Human Food and Animal Feed, accessed on December 28, 2017. U.S. Food and Drug Administration.
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. K. Arrus et al (2005). Aflatoxin production by Aspergillus flavus in Brazil nuts. Journal of Stored Products Research, 41(5), 513-527.
5. L. Alpsoy et al (2009). The antioxidant effects of vitamin A, C, and E on aflatoxin B1-induced oxidative stress in human lymphocytes. Toxicology & Industrial Health, 25(2):121-7.
6. P. Sahoo and S. Mukherjee (2003). Immunomodulation by dietary vitamin C in healthy and aflatoxin B1-induced immunocompromised rohu (Labeo rohita). Comparative Immunology, Microbiology and Infectious Diseases, 26(1), 65-76.
