Aflatoxin detection seen as key to reduce preventable liver cancer

myco_corn_blogFor several years, scientist Felicia Wu, Ph.D. and her team have been studying cost-effective and feasible aflatoxin prevention methods that have the possibility to prevent future cases of aflatoxin-induced liver cancer around the world.

According to a recently publish article in Nature, aflatoxin is generated by the fungi Aspergillus flavus and Aspergillus parasiticus and is a type of carcinogenic toxin that can grow on corn, pistachios and peanuts. Currently responsible for up to 28% of liver cancer cases worldwide, it is the biggest risk factor for the disease and has been associated with acute poisoning, immune-system dysfunction and stunted growth in children.

Since many people are unaware of the link between naturally occurring food contaminants and cancer, Dr. Wu’s studies focus on increasing education, stricter food-quality controls and the importance of cultivating alternative crops, in an effort to decrease worldwide rates of liver cancer.

“Our studies to this point suggest that up to 155,000 cases of liver cancer per year come from aflatoxin exposure in the diet,” Dr. Wu said in the article. “The majority of cases occur in sub-Saharan Africa, southeast Asia and China and parts of Central America.”

According to the article, approximately  100 nations have set standards for the maximum amount of aflatoxin allowable in foodstuffs, but setting a standard does not always ensure a safe food supply — particularly among subsistence farmers and rural communities in low-income countries, where food rarely undergoes formal safety inspection. Adding to the complexity is the fact that different nations consume different amounts of the riskiest crops. The United States and Kenya, for example, both have maximum allowable aflatoxin levels of 20 micrograms per kilogram of maize, but the average Kenyan consumes six times more maize per day than the average American, and usually in a less-processed form.

People whose livers are already compromised by infection with hepatitis B virus (HBV) are particularly susceptible to aflatoxin-induced liver cancer. Of the 172,000 cases per year of hepatocellular carcinoma (the most common form of liver cancer) most of these individuals are also infected with HBV. That being said, one component of Dr. Wu’s research is widespread vaccination against HBV.

Decreasing contamination is also another solution Dr. Wu’s research suggests as stressed plants are more vulnerable to fungal infection. As stated in the article, careful selection of crop varieties that are matched to the soil and water conditions, improved irrigation practices to reduce drought stress, and by breeding crops for both high yield and the ability to withstand environmental stressors, such as heat, drought and insect damage, can all help.

Aflatoxin, however, also accumulates in crops after they have been harvested as the fungi that produces the toxin thrives in damp conditions. This means storage facilities must be kept cool and dry and pests such as rodents and insects must be controlled because they can transport the fungus to other stored foods.

Another solution that Dr. Wu discusses in her research is to reduce consumption of foods that are contaminated with aflatoxin in the first place. As an example, the article references dietary changes in Qidong, China where market reforms introduced in the 1980s meant that citizens in the area began eating more rice and less maize. Decreased maize consumption resulted in lower exposure to aflatoxin in the diet and a 45% decrease in liver-cancer mortality.

In conclusion, Dr. Wu writes,

“Now, it is crucial to disseminate these interventions and encourage those populations at the highest risk to adopt them. Locally, educators must encourage communities to grow and consume foods that are less likely to be infected with Aspergillus. But because dietary change occurs slowly, they should also help communities to choose geographically suitable maize and peanut varieties and teach them practices that minimize post-harvest aflatoxin accumulation.”

“Globally, the HBV vaccine must be disseminated to high-risk populations at increased risk of aflatoxin exposure. And as the prevalence of hepatitis C virus (HCV) increases worldwide, researchers must investigate the potential synergism of HCV and aflatoxin exposure. Only then will rates of these preventable cases of liver cancer begin to decline.”

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