Phytohaemagglutinin (Red Kidney Bean Poisoning)
Phytohaemagglutinin (Kidney Bean Lectin) is a compound that
causes red kidney bean poisoning (kinkoti bean poisoning, and
possibly other names). Red kidney bean poisoning is most often
caused by consuming raw or undercooked kidney beans.
The onset time from consumption of raw or undercooked kidney
beans to symptoms varies from between 1 to 3 hours. Onset is
usually marked by extreme nausea, followed by vomiting, which may
be very severe. Diarrhea develops somewhat later (from one to a few
hours), and some persons report abdominal pain. Some persons have
been hospitalized, but recovery is usually rapid (3 - 4 h after
onset of symptoms) and spontaneous.
Diagnosis is made on the basis of symptoms, food history, and
the exclusion of other rapid onset food poisoning agents (e.g.,
Bacillus cereus, Staphylococcus aureus, arsenic, mercury, lead, and
Yes. Phytohaemagglutinin, the presumed toxic agent, is found in
many species of beans, but it is in highest concentration in red
kidney beans (
). The unit of toxin measure
is the hemagglutinating unit (hau). Raw kidney beans contain from
20,000 to 70,000 hau, while fully cooked beans contain from 200 to
400 hau. White kidney beans, another variety of Phaseolus vulgaris,
contain about one-third the amount of toxin as the red variety;
broad beans (Vicia faba) contain 5 to 10% the amount that red
kidney beans contain. The syndrome is usually caused by the
ingestion of raw, soaked kidney beans, either alone or in salads or
As few as four or five raw beans can trigger
Several outbreaks have been associated with "slow
cookers" or crock pots, or in casseroles which had not reached a
high enough internal temperature to destroy the glycoprotein
lectin. It has been shown that heating to 80 degrees Celsius (175 degrees Fahrenheit) may potentiate the
toxicity five-fold, so that these beans are more toxic than if
eaten raw. In studies of casseroles cooked in slow cookers,
internal temperatures often did not exceed 75 degrees Celsius (170 degrees Fahrenheit).
This syndrome has occurred in the United Kingdom with some
regularity. Reports of this syndrome in the United States are
anecdotal and have not been formally published.
All persons, regardless of age or gender, appear to be equally
susceptible. The severity is related only to the dose ingested.
Food and Drug
Last updated February 2005 by
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