Kidney Beans can Poison You and Make you Sick

kidney beans

Now that headline is slightly misleading in that it should say raw kidney beans can make you sick.  Kidney beans contain the toxic compound phytohaemagglutinin, a lectin.  This compound is actually present in many varieties of common bean but is especially concentrated in red kidney beans. The good news is that it won’t kill you but phytohaemagglutinin poisoning will cause nausea, vomiting, and diarrhea.

The onset is from one to three hours after consumption of improperly prepared beans, and the symptoms will last for a few hours.  Eating as few as four or five raw kidney beans may be sufficient to trigger symptoms in some people.  Phytohaemagglutinin is deactivated by cooking beans at 212 °F for ten minutes.  However, for dry beans the U.S. Food and Drug Administration (FDA) also recommends an initial soak of at least 5 hours in water; the soaking water should be discarded.

The ten minutes at 212 °F that is required to destroy the toxin is much shorter than the time required to fully cook the beans.   However, lower cooking temperatures may have opposite effects of concentrating the toxic effect of haemagglutinin.  Beans cooked at lower temperatures without being boiled for 10 minutes are reported to be up to five times as toxic as raw beans.  Outbreaks of poisoning have been associated with the use of slow cookers, the low cooking temperatures of which may be unable to degrade the toxin.

Now I know this is not a common problem today, most kidney beans come from a can.  Even if you got sick, you may not tie it to the beans.  However, in bad times, you can’t afford to be sick, and worst if you thought the beans were making you sick and didn’t know why, you might throw them away.

The following is what US food and drug administration has to say on this problem.

1. Name of the Organism:

Phytohaemagglutinin (Kidney Bean Lectin)

This compound, a lectin or hemagglutinin, has been used by immunologists for years to trigger DNA synthesis in T  lymphocytes, and more recently, to activate latent human immunodeficiency virus type 1 (HIV-1, AIDS virus) from human peripheral lymphocytes. Besides inducing mitosis, lectins are known for their ability to agglutinate many mammalian red blood cell types, alter cell membrane transport systems, alter cell permeability to proteins, and generally interfere with cellular metabolism.

2. Nature of Acute Disease:

Red Kidney Bean (Phaseolus vulgaris) Poisoning, Kinkoti Bean Poisoning, and possibly other names.

3. Nature of Disease:

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.

4. Diagnosis of Human Illness:

Diagnosis is made on the basis of symptoms, food history, and the exclusion of other rapid onset food poisoning agents (e.g., Bacillus cereusStaphylococcus aureus, arsenic, mercury, lead, and cyanide).

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5. Associated Foods:

Phytohaemagglutinin, the presumed toxic agent, is found in many species of beans, but it is in highest concentration in red kidney beans (Phaseolus vulgaris). 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 casseroles. As few as four or five raw beans can trigger symptoms. 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°C 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°C.

6. Relative Frequency of Disease:

This syndrome has occurred in the United Kingdom with some regularity. Seven outbreaks occurred in the U.K. between 1976 and 1979 and were reviewed (Noah et al. 1980. Br. Med. J. 19 July, 236-7). Two more incidents were reported by Public Health Laboratory Services (PHLS), Colindale, U.K. in the summer of 1988. Reports of this syndrome in the United States are anecdotal and have not been formally published.

7. Course of Disease and Complications:

The disease course is rapid. All symptoms usually resolve within several hours of onset. Vomiting is usually described as profuse, and the severity of symptoms is directly related to the dose of toxin (number of raw beans ingested). Hospitalization has occasionally resulted, and intravenous fluids may have to be administered. Although of short duration, the symptoms are extremely debilitating.

8. Target Populations:

All persons, regardless of age or gender, appear to be equally susceptible; the severity is related only to the dose ingested. In the seven outbreaks mentioned above, the attack rate was 100%.

9. Food Analysis:

The difficulty in food analysis is that this syndrome is not well known in the medical community. Other possible causes must be eliminated, such as Bacillus cereusstaphylococcal food poisoning, or chemical toxicity. If beans are a component of the suspected meal, analysis is quite simple, and based on hemagglutination of red blood cells (hau).

This is something that I have not known and this information may keep me from throwing good food out.


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1 thought on “Kidney Beans can Poison You and Make you Sick”

  1. I have no problem with soy products and never eat the beans. Baked beans, refried beans,black eyed peas don’t bother me but red kidney beans are lethal! Canned,baked, boiled is no different. Even a couple of beans will have me with lower gut problems for a week!! I usually have no problem with any foods I eat. I’m a male over 70 and am in very good health so says my blood test!

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