Toxins Some kinds of raw beans contain a harmful, flavourless toxin: the
lectin phytohaemagglutinin, which must be destroyed by cooking. Red
kidney beans are particularly toxic, but other types also pose risks of
food poisoning. Even small quantities (4 or 5 raw beans) may cause severe stomachache, vomiting, and diarrhea. This risk does not apply to
canned beans because they have already been cooked. A recommended method is to boil the beans for at least ten minutes; under-cooked beans may be more toxic than raw beans. Beans need to be cooked thoroughly to destroy toxins;
slow cooking is unsafe as it makes the beans soft without necessarily destroying the toxins. Bean poisoning is not well known in the medical community, and many cases may be misdiagnosed or never reported; figures appear not to be available. In the case of the United Kingdom
National Poisons Information Service, available only to health professionals, the dangers of beans other than red beans were not flagged .
Other hazards It is common to make
beansprouts by letting some types of bean, often
mung beans, germinate in moist and warm conditions; beansprouts may be used as ingredients in cooked dishes, or eaten raw or lightly cooked. There have been many
outbreaks of disease from bacterial contamination, often by
salmonella,
listeria, and
Escherichia coli, of beansprouts not thoroughly cooked, some causing significant mortality. Many types of bean, such as kidney beans, contain significant amounts of
antinutrients that inhibit some enzyme processes in the body.
Phytic acid, present in beans, interferes with bone growth and interrupts
vitamin D metabolism. Many beans, including broad beans, navy beans, kidney beans and soybeans, contain large sugar molecules,
oligosaccharides (particularly
raffinose and
stachyose). A suitable oligosaccharide-cleaving
enzyme is necessary to digest these. As the human digestive tract does not contain such enzymes, consumed oligosaccharides are digested by
bacteria in the large intestine, producing gases such as methane, released as
flatulence. == In human society ==