Naturally occurring toxicants in foods and their significance in the human diet.

Among the many biologically active and potentially toxic factors known to be present in plant foodstuffs normally consumed by man, those that are present in legumes have received the most attention. Two categories of legume toxins will be considered - those whose effects have been extensively studied in experimental animals but whose significance in man must remain open to conjecture, and those which are known to produce toxic effects in man but whose identity remains uncertain because similar effects are not readily reproduced in animal models. The protease inhibitors have, over the years, been the object of much study in experimental animals where they have been observed to have an adverse effect on growth and to cause pancreatic enlargement. The relevance of these observations to human nutrition remains obscure, however, because of our lack of knowledge concerning the effect of soybean trypsin inhibitors on the human pancreas. Lectins from certain legumes such as the common bean (Phaseolus vulgaris) have been shown to be toxic to animals upon oral ingestion presumably because of the damage which they inflict upon binding to the cells lining the intestinal mucosa. Lectins may therefore be responsible for reported cases of human intoxication associated with the consumption of inadequately cooked beans. Lathyrism and favism are diseases in man which are associated with the consumption of Lathyrus sativus and Vicia faba respectively. Evidence leading to the probable identification of the causative factors of these diseases and the steps necessary for their elimination will be discussed.