Brazilian Nuts: Why Aflatoxins Could Cause Liver Cancer

Brazilian nuts are regulated by the European Commission because some have entered the European Union containing unacceptable levels of a food toxin which has been shown to damage DNA and cause cancer–particularly liver cancer. Should consumers in the United States be worried about consuming Brazilian or other types of nuts?

The Brazil nut is the edible seed from a South American tree that is native to Venezuela, Brazil, eastern Colombia, Peru and Bolivia. Brazil nuts contain a significant amount of fat and due to their omega-6 content, shelled nuts can soon become rancid and produce alflatoxin, a fungus from the Aspergillus species.

About Aspergillus, Aflatoxins, and Cancer

Aspergillus is found in soil, decaying vegetation, hay and in grains that are deteriorating. The most favorable conditions are high temperature, such as that along the equator where Brazil nuts are grown, and environments with high-moisture content. They can also colonize and contaminate grains that are damaged by drought, which lowers the barrier to entry into the plant. Tree nuts are among the crops most frequently affected.

Aflatoxins are metabolized by the liver to a reactive epoxide called aflatoxin M1, which damages DNA, particularly the gene that causes liver tumors.  A high level of aflatoxin exposure, called aflatoxicosis, can produce necrosis of the liver, which can result in damage leading to cirrhosis or liver cancer.  Another strain of aflatoxin, B1, is considered by the International Agency for Research on Cancer (IARC) as a carcinogenic (cancer-causing) agent.

Humans are thought to have a high tolerance for aflatoxin exposure and rarely succumb to acute aflatoxicosis. Those who may be particularly sensitive to the toxin are children, people with poor nutritional status, and those who are infected with the Hepatitis B (HBV) virus. Symptoms of aflatoxicosis include vomiting, abdominal pain, pulmonary and cerebral edema, and convulsions.

Brazilian Nut Nutrition

Nutritionally, Brazil nuts are a good source of selenium, magnesium, and thiamin. In particular, the high selenium content has antioxidant properties that have been correlated with a lowered risk of breast and prostate cancer.

Reducing Exposure to Aflatoxin

Despite the link to cancer, the FDA allows aflatoxins to occur at low levels in some foods, such as nuts, seeds and legumes, because they are considered an unavoidable contaminant. The agency believes that eating small amounts of aflatoxin poses little risk to humans over a lifetime.

To help minimize your exposure to aflatoxin, the FDA recommends purchasing only major brands of nuts and nut butters and to discard any shelled nuts that look discolored or moldy. Some medical research has indicated that a diet including apiaceous vegetables, such as carrots, parsnips, celery and parsley, may reduce the carcinogenic effects of aflatoxin. A study by the Johns Hopkins University also tested an over-the-counter dietary supplement containing chlorophyllin, a derivative of chlorophyll.  The study, conducted in China, found that consumption of chlorphyllin reduced the urinary levels of the aflatoxin-related adducts that damage DNA.


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