Red kidney beans--to eat or not to eat?

The importation of dry red kidney beans (a variety of the species Phaseolus vulgaris) for cultivation or consumption in South Africa is prohibited because of their potential toxicity to humans. It has been established that the haemagglutinating lectins (e.g. phytohaemagglutinin (PHA)) in kidney beans are responsible for this toxicity. Dry bean varieties available on the South African market for human consumption as well as locally produced (for this study) and imported dry red kidney beans and imported canned red kidney beans were compared. The PHA activity and the effect of heat thereon were measured, before and after overnight soaking. The PHA activity in extracts of uncooked and incompletely cooked red kidney beans was not higher than the levels measured in 50% of the other bean varieties included in the study. These findings indicate that the toxic potentials and health risks associated with red kidney beans are similar to those of other dry beans already commercially available to South Africans.