Hi all! We've had some recent discussions on legumes (beans) and some of which have involved safety concerns. Legumes contain toxins known as lectins which are okay to eat if prepared properly.
Lectins are a type of protein found in many plant foods. They exist in significant amounts in about 30 percent of foods and are especially concentrated in grains and legumes. Some lectins are beneficial, such as CLEC11A which promotes bone growth; others may be powerful toxins such as ricin. Toxic lectins can cause damage to the lining of the gastrointestinal tract or organs, and can interfere with metabolism when consumed in large amounts.
Toxic lectins and other enzyme inhibitors are a health concern because they interfere with normal digestion and metabolism, resulting in food poisoning-like symptoms. Long term consumption can lead to protein deficiencies, weight loss and general poor health. This is why claims of people feeding them without issue is a poor argument for their safety.
Bottom line: Lectin poisoning has the potential to be fatal.
The unripe, young fruit and protective pods of various cultivars of the common bean (Phaseolus vulgaris) aka snap beans, string beans, green beans, haricot beans are safe to eat raw or cooked.
Kidney, navy, pinto, lima, fava, wax, jack, string and field beans all contain lectins. Cooking and digestion destroy some, but not all, lectins. Fully cook these beans before eating them.
Soy beans have some especially nasty enzyme inhibitors and should never be eaten uncooked or fed to any animal in a raw form, even if they are green they should be thoroughly cooked or fermented.
NEVER eat or feed Castor beans in any form; they are poisonous. If castor beans are chewed and swallowed, they can release ricin, one of the most toxic poisons known to man. Eating just one or two castor beans can easily cause the demise of the eater.
There are a few varieties of beans that are okay to sprout: Adzuki, Garbanzo (Chickpea), Peas (sweet or green), Lentils, or Mung bean. Make sure you sprout SAFELY and follow instructions to prevent bacteria growth on your sprouts.
From the Food & Drug Administration (FDA):
"Protein / Toxin - Lectins are widely occurring, sugar-binding proteins that perform a variety of biological functions in plants and animals, including humans, but some of them may become toxic at high levels. 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.
“Among the lectins known to have toxic effects is phytohaemagglutinin, which occurs at relatively high levels in the seeds of legumes (e.g., beans). The role of this compound in defense against plant pests and pathogens has been established.” The amount of phytohemagglutinin, the presumed toxic lectin in beans, can vary significantly among bean varieties.
“Red kidney bean (Phaseolus vulgaris) poisoning and kinkoti bean poisoning are examples of names for the illness caused by phytohaemagglutinin.”
Toxic dose: As few as four or five raw beans can trigger symptoms (for a human); Oral (consumption of uncooked or undercooked kidney beans).
Lectins in pinto beans are “toxic types.” According to the NIH study, “Significant (p<0.05) differences in lectin content were observed between anasazi and pinto bean. The lectins of anasazi beans were classified as non toxic and those of the pinto beans as toxic types.”
The mechanism and pathway of toxicity is not known, but oral ingestion of toxic lectins is known to reduce intestinal absorption and cause weight loss, growth retardation, and diarrhea in several animal species. Several issues have been associated with legumes cooked in slow cookers because the heat and/or duration is insufficient to reduce these toxins.
References: https://www.ncbi.nlm.nih.gov/pubmed