Dietary aflatoxins and liver cancer – a population based study in Kenya

THE possibility that contamination of dietary staples by aflatoxins could be an aetiological factor in liver cancer was originally suggested by le Breton, Frayss-inet and Boy (1962), soon after the outbreak of Turkey " X " dlisease in Britain and the realization that a fungal metabolite was involved. Further experimental and epidemiological research supported this suggestion and Oettle (1965), reviewing the situation, concluded that a mycotoxin hypothesis fitted the known liver cancer data better than any other suspected aetiological factor. Little has been added over the last decade to our knowledge of aflatoxin toxicity or carci-nogenicity in man and Newberne and Butler (1969) have warned that factual evidence must be awaited and caution exercised in assigning the aflatoxins a role in worldwide liver cancer. This is particularly so in Africa where the dietary staples which may be contaminated are major sources of food and often represent export crops vital to the economies of such countries. It was decided, therefore, to ascertain whether the afla-toxins were ingested by man; whether an association existed with the incidence of liver cancer and, finally, whether a dose-response relationship could be established. It was considered that such a study must be population based and designed for comparison with areas of varying cancer incidence or widely differing afla-toxin ingestion levels. Although the afla-toxins are relatively heat stable and possibly survive most cooking methods, preliminary studies indicated that housewife selection of foodstuffs could lower the food aflatoxin levels inferred from examination of market samples or even home stores. The analysis for the afla-toxins was made, therefore, on prepared food ready for ingestion. New fungal metabolites with hepatoxic and hepato-carcinogenic properties were, and are, being reported as work is intensified in this field but sufficiently sensitive analytical methods were not available for known carcinogenic mycotoxins other than afla-toxin at the time the survey was started and the present investigation was limited to the aflatoxins. The Murang'a district of the central province of Kenya was chosen primarily to check the feasilibity, methodology and general study design. There was no evidence to suggest that the frequency of liver cancer was higher here than elsewhere in East Africa. The area has a high density rural population living traditionally on food mostly produced within the district. No groundnuts are grown or used in this area but Aspergillus flavts has been reported to grow on the cereals which form a major part of …