Reporter 407, 6 October 1997

Staple diet proves key to West African cancer threat

A ground-breaking project has been given more than a quarter of a million pounds to help reduce the alarmingly high number of liver cancer deaths in developing countries. The University’s Molecular Epidemiology Unit, created last year under the professorship of Chris Wild, is to work with overseas scientists to find ways of preventing crops in storage being contaminated by dangerous toxins.

Liver cancer is the most common malignancy among men in West Africa, where it is responsible for up to ten percent of adult male mortality. As there is an even greater incidence among men aged between 30 and 40 years, it is a particularly devastating disease for the communities affected.

A major cause of liver cancer, in addition to the hepatitis B virus, is contamination of staple foods with aflatoxins. These toxins are produced by fungi which grow on crops such as peanuts and corn, particularly after harvest when the foods are stored in hot and humid conditions. The toxins are the most potent naturally occurring liver carcinogens identified in animal experiments, and have been classified as human carcinogens by the International Agency for Research on Cancer (IARC).

While working for the IARC in France, Professor Wild developed a blood-based test to measure these toxins in exposed populations. This work revealed the startling magnitude of exposure in sub-Saharan Africa and South-east Asia, and found that exposure occurs throughout life, starting in the womb.

Exposure in these developing countries occurs at levels which are not permitted for either humans or cattle in the European Union and North America. Paradoxically, in West Africa crops for export are surveyed for aflatoxins, while food for local consumption is subject to no controls. The result is widespread exposure to this potent human carcinogen. Alongside the hepatitis B virus, which is also endemic, this explains the extremely high incidence of liver cancer.

Professor Wild’s research was supported by the USA-based National Institute of Environmental Health Sciences (NIEHS). The NIEHS has now renewed this funding to the Molecular Epidemiology Unit at the University of Leeds for a period of five years, at a total level exceeding £250,000. This money will allow the Leeds unit to work in collaboration with scientists in Guinea-Conakry and from the Division of Environmental Health Sciences at Johns Hopkins University to explore low technology methods of reducing aflatoxin exposure by modifying the way crops are handled and stored.

Dr Philippe Nikiema of the University of Ouagadougou, Burkina Faso, is spending a year in the unit to learn the test for aflatoxin measurements in blood and to develop further collaborative projects on liver cancer in his home country. Similarly, Dr Fatma Meky, supported by an Egyptian Government fellowship, is conducting a PhD on developing tests to measure other fungal-produced toxins to which human populations are exposed and for which even less information about the health consequences is available.

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