Carcinogenic higher plant metabolites in the human diet in temperate countries: a review.

Interest has increased recently in the possible human carcinogenic effects of plant metabolites in the diet. Some psoralens, some pyrrolizidine alkaloids and 'bracken carcinogen' may be dietary carcinogens, the latter two via contamination of food products from animals ingesting toxic plants. With the exception of 'bracken carcinogen', the structures of these compounds have been established. Further research to quantify the levels of these compounds in foodstuffs and to correlate these with the amounts of the compounds having toxic effects in laboratory animals would be valuable. Epidemiological studies on critical-intake consumer groups would also be of value in defining the hazard, if any, the presence of these compounds in the diet poses to the consumer.