My question is about lectins, and lectins from legumes and beans in particular. I have not seen any study which really discusses the potentially toxic impacts from lectins, including what types of lectins may be ok, or what levels are safe/not safe; can you help?

In raw form, kidney beans can contain high amounts of a potentially toxic substance called phytohemagglutinin. This substance is classified as a lectin glycoprotein, and in preliminary research studies has been reported to disrupt cellular metabolism with sufficiently high intakes. The amount of this toxin in beans is usually measured in terms of hemagglutinating units, or hau. In their raw form, red kidney beans can contain 20,000 to 70,000 hau. This number drops down to 200 to 400 hau with fully cooked red beans.

The reduction in lectin content will vary depending on the cooking time. However, other than the recommended cooking time specific to legume, we don't encourage any additional cooking to further reduce the lectin content. This reduction seems natural and is a part of healthy eating.

Various sources tend to only report the potential negative effects associated with lectins and do not emphasize the research showing that very high amounts are necessary for the potential damaging effects. The likelihood of ingesting these high amounts from eating cooked legumes several times a week is not likely. In addition, some researchers are studying the potential benefit of lectins to human health.

To shorten cooking time and make beans easier to digest, they should be presoaked (presoaking has been found to reduce the raffinose-type oligosaccharides, sugars associated with causing flatulence.) There are two basic methods for presoaking. For each, start by placing the beans in a saucepan with two to three cups of water per cup of beans.

The first method is to boil the beans for two minutes, take the pan off the heat, cover and allow to stand for two hours. The second method is to simply soak the beans in water for eight hours or overnight, placing the pan in the refrigerator so beans will not ferment. Before cooking, regardless of method, drain the soaking liquid and rinse the beans with clean water.

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