RED kidney beans are found everywhere, from ais kacang and cendol to savoury salads, stews and soups.
As such, it is easy to assume they are harmless and dismiss an often-quoted claim that under certain conditions, a small handful of red kidney beans are enough to make someone sick.
With that said, is there any truth to this claim?
Is it true that red kidney beans can be toxic?
VERDICT:
TRUE
This is actually very true, as red kidney beans contain a chemical called phytohaemagglutinin, which can cause red blood cells to literally clump together with rather unpleasant results.
While this chemical is found in many legumes, raw red kidney beans contain from 20,000 to 70,000 hemagglutinating units or hau, which is the unit used to measure the level of the toxic chemical.
By contrast, fully cooked beans contain from 200 to 400 hau and white kidney beans contain about one-third the amount of toxin as the red variety.
Indeed, official bodies like the Hong Kong government’s Centre for Food Safety have cautioned that “few as four or five raw beans” can trigger symptoms.
“(Symptoms) usually begin with extreme nausea and vomiting within one to three hours after ingestion, with diarrhoea developing later within that time frame,” says the Centre.
It then adds that the vomiting that accompanies the diarrhoea may become severe and that both of these may in turn be joined by abdominal pain.
However, this poisoning is generally not fatal as people usually recover without requiring hospitalisation.
“Recovery usually is rapid, within 3 to 4 hours after the onset of symptoms and is spontaneous,” said the Centre.
And with that, how can red kidney beans be prepared safely?
“To destroy the toxin, beans should be soaked and boiled thoroughly in fresh water; for example soaked for at least 12 hours and then boiled vigorously for at least 10 minutes,” it said.
The Centre added that studies showed that the toxic chemical – phytohaemagglutinin – remained active after the beans had been cooked even at 85°C for an hour.
“Therefore, beans should not be cooked at a low temperature, for example in a crock pot or slow cooker, since it may not destroy the toxin.
On the other hand, commercially tinned/canned beans are safe to eat without further cooking as they have been subjected to thorough heat treatment,” it said.
Ultimately, it can be said that while it is true that red kidney beans can be toxic – they are only toxic if eaten raw or prepared improperly, and in this case it might be one of the few cases where canned food is safer than fresh.
SOURCES:
https://www.cfs.gov.hk/
https://www.foodsafetynews.
https://pmc.ncbi.nlm.nih.gov/
https://www.fda.gov/media/
https://www.foodsafety.asn.au/
