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Aflatoxin in Pistachios: What You Should Know


Tree nuts, particularly pistachio nuts, are highly susceptible to contamination by aflatoxins, harmful substances that are produced by certain molds such as Aspergillus flavus and Aspergillus parasiticus. Not only are aflatoxins known to cause cancer, they have also been linked to a wide variety of other diseases. However, given the wide-ranging health benefits of pistachios, these small nuts remain a popular snack food among health-conscious people.

In this article, we provide information about the levels aflatoxins found in pistachios, assess the health risks associated with exposure to aflatoxins from pistachios, and provide some tips on how you can reduce your exposure to these toxic substances.

Pistachios Are Particularly Susceptible to Aflatoxin Contamination

Among tree nuts, pistachios appear to be particularly susceptible to contamination by aflatoxins (1, 2). A large Japanese study that looked at the aflatoxin levels in over 3,000 samples of foods or foodstuffs, including cereals, nuts, beans, spices, dairy products and dried fruits, found that pistachios had the highest levels of aflatoxin B1 among the tested foods and foodstuffs (2). Aflatoxin B1 is considered the most dangerous and the most abundant type of aflatoxin found in foods.

In another study, published in the April 2000 issue of the journal Food Group, a group of researchers from Qatar analyzed the aflatoxin levels in pistachios and a number of other nuts including peanuts, cashews, walnuts and hazelnuts. They analyzed 81 nut samples in total, but aflatoxins were only detected in pistachios and peanuts, with aflatoxin levels of the samples ranging from about 0.53 to 289 mcg/kg. (3)

In a follow-up test designed to further analyze the aflatoxin content of pistachios, the Qatari researchers collected 101 samples of pistachios, and found aflatoxin contamination in 48 of them, with total aflatoxin levels ranging from 1.2 to 275 mcg/kg. Aflatoxin B1 and B2 were detected in all the contaminated samples of pistachios, whereas aflatoxin G1 and G2 were detected only in three of the samples. (3)

Aflatoxin Content of Shelled vs Unshelled Pistachios

Studies have shown that in general, shelled and damaged nuts tend to contain more aflatoxins than unshelled nuts (4). This also appears to be the case for pistachios. The above-discussed Qatari study that analyzed the aflatoxin levels is pistachios found that pistachios without shell contained very high levels of aflatoxins, with total aflatoxin levels ranging from 8.3 to 275 mcg/kg in the contaminated samples. By contrast, the total aflatoxin levels in the contaminated unshelled samples ranged from 1.2 to 75 mcg/kg. (3)

Health Effects of Eating Contaminated Pistachios

One of the most serious health effects associated with eating aflatoxin-contaminated foods is the ability of aflatoxin to increase the risk of liver cancer. The International Agency for Research on Cancer, which is an intergovernmental agency forming part of the World Health Organization, has classified aflatoxin as a Group I Carcinogen, meaning that there is significant scientific evidence suggesting that aflatoxin can cause cancer in humans (5).

Its carcinogenic properties aside, aflatoxin has also been linked to cardiovascular problems, impaired immune function, nutrient deficiencies, gastrointestinal problems, stunted growth in children, and a wide range of other health problems.

The good news is that governments in developed countries as well as many less developed countries have established food safety guidelines and regulations to control the amounts of aflatoxins in national food supplies. The U.S. Food and Drug Administration (FDA), for example, enforces a ruling that 20 parts per billion is the maximum level of aflatoxin permitted in all foods, including tree nuts such as pistachios (6). Therefore, if you live in a country like the US, your risk of ingesting significant amounts of aflatoxins from a bag of pistachios is not very high.

How to Minimize Your Exposure to Pistachio Aflatoxins

Despite the efforts of the FDA to keep aflatoxin-contaminated foods out of the food supply, recalls caused by unacceptable levels of aflatoxins do occasionally happen. What's more, nuts like pistachios can also get contaminated with aflatoxins after they have passed muster. Luckily, there are a number of things you can do to reduce your exposure to aflatoxins from pistachios and other nuts. Here are some suggestions:

  • Buy pistachios from a grocery where the nuts have been stored in a dry, cool environment. The fungi that produce aflatoxins love humidity and warm temperatures.
  • If your pistachios look damaged, moldy or discolored, get rid of them. Also pistachios that taste moldy should be discarded.
  • Store your pistachios in a dark, cool place and eat them relatively fast. To extend their shelf-life, you may also want to consider freezing your pistachios.
  • Yet another way to reduce your risk of aflatoxin ingestion is to buy unshelled pistachios. As mentioned earlier, shelled pistachios have been shown to contain higher levels of aflatoxins than their unshelled counterparts.
  • Up your vitamin C intake, for example by including some vitamin C rich superfoods in your diet. Laboratory and animal studies suggest that vitamin C may help counteract some of the harmful effects of aflatoxins.