The next gluten?

In 1988, a British hospital served its staff a special lunch for “healthy eating day.” One dish contained red kidney beans. A medical journal recounts the aftermath. At 3:00 p.m. a surgical assistant vomited in the operating room. Over the next four hours, the hospital staff was rocked by vomiting and diarrhea. 

I can end the description there.

Everyone recovered by the next day, and tests of the food didn’t reveal any of the common causes of food poisoning. Eventually the incident was traced to the red kidney beans, which have an especially high concentration of the lectin phytohaemagglutinin.
This is a lectin that’s known to be dangerous, and it’s why people read that kidney beans are harmful when eaten raw. 

For example, a reader of Penn State University’s Home Food Preservation advice site writes: “I read that kidney beans are harmful when eaten raw. Several day care and nursery schools have dry beans (different varieties) out for kids to play with. What danger would there be if a child ate a few of these raw beans?”


Possibly some danger. The site goes on to advise the parent—presumably a parent—that Kidney Bean Poisoning is caused by phytohaemagglutinin, and that different types of lectins are found in many species of beans. As few as four undercooked kidney beans can bring on symptoms, but lectins are inactivated with cooking, “so fully cooked or canned kidney beans are safe to eat.” (Though undercooking may actually increase lectin activity, making the beans more dangerous than were they eaten raw.)

Lectins are a group of proteins that bind to carbohydrates. They are sometimes referred to as a type of “anti-nutrient,” a category that also includes fiber. This term refers to compounds in foods that aren’t nutrients, and whose role in human health is unclear, but may have evolved in plants to dissuade predators.


David Jenkins, a professor of nutritional sciences and medicine at the University of Toronto, explained to me, “Lectins help protect plants from being digested, so they’ve been called anti-nutrients for a long time.” Lectins levels are especially high in legumes (e.g., black beans, soybeans, lima beans, kidney beans, and lentils) and grain products. When eaten in those foods, the lectins typically bind to carbohydrates and pass through the human digestive tract. But when the starches in the above plants haven’t begun to be hydrolyzed by cooking, unbound lectins are free to interact with cells in our intestines. That interaction can, in some cases, cause symptoms of food poisoning.


“Presumably if you take a load of cooked food—with lectins, which may or may not be destroyed by the heat—you’ve also got some floating carbohydrates, so a lot of the lectins are effectively deactivated,” said Jenkins. “But if you eat raw food of certain types––the nightshade family especially and some of the legumes—then you may get a lot of lectins and not much of the carbohydrate that lectins can attack. But they can attack the carbohydrate on your cells. So maybe it’s not a good idea.”

Stories of lectin poisoning are not especially rare. In The Independent the food writer Vicky Jones describes a dinner party in which she used Greek butter beans in a dish without boiling them first. Soon everyone was violently ill. It came on so quickly that before they could consider going to the emergency room, “death seemed preferable to [trekking to the] hospital.”


Jones recovered fully, as most lectin-poisoned people do. Most. There are cases like that of the most famous person to be killed by an umbrella, the dissident journalist Georgi Markov. This was in 1978. He was standing at a bus top when something pierced the back of his thigh. It was an injection delivered through the tip of an umbrella carried by a man who ran off.


Markov grew febrile and died four days later. Pathology reports said the cause of death was a microscopic dose of the poison ricin. Ricin is found in the seeds of the castorbean plant, a shrub-like entity with large, long-stemmed leaves. In a world that fetishizes natural products and remedies, ricin is as natural as natural gets. And it is, you guessed it, a type of lectin.


Which then makes you think, maybe the bookseller’s reference to lectins inciting chemical warfare in our bodies isn’t far off?

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