Many people eat this toxic food on a daily basis and have no ill effects. Other people get severely sick with only half an ounce ingestion. The toxic food we discuss today? Beans.
Yes Beans Are Toxic!
You may have heard that red kidney beans have a toxin in them, but they are not the only legume containing this toxin. All members of the bean family contain a number of different toxic compounds, all in varying amounts.
All legume bean seeds contain compounds commonly called lectins. Lectins are glycoproteins that are present in a wide variety of commonly eaten plant foods, not just beans. Some are not harmful, but the lectins found in undercooked and raw beans are toxic.
From a plant’s point of view, this high concentration of lectins in seeds keeps critters from eating them. As the seed begins to grow, the levels of lectin drop, which is why we can eat raw bean sprouts.
Ever find a stash of palo verde beans in a packrat nest? Stored for several years the lectin levels drop low enough that the rodents can eat them. Packrats are just packing their nests for that someday.
Speaking of palo verde – palo verde flowers do not contain these compounds. They are found in the seeds. Here’s one way to safely use palo verde – use the palo verde flower buds!
One Specifically Toxic Lectin
The name of this lectin is phytohaemagglutinin (PHA) and it occurs naturally in all legumes. It comes in two forms and causes either white blood cells or red blood cells to clump together. The body can quickly recognize this danger in the digestive tract and does it’s very best to eliminate the danger from the body. Yes, your food has poisoned you! The reaction is termed “gastroenteritis,” a medical term that covers abdominal cramps, nausea, vomiting, and diarrhea. Unpleasant – yes. Deadly – yes, but generally only if there are other medical conditions. [Science Nerd dissects PHA at the bottom of this post.]
The CDC estimates that up to 20 percent of annual food poisoning cases are attributed to consumption of under cooked beans. Furthermore, according to the CDC, an estimated 48 million Americans will become sick from a food borne illness this year. Of that number over a million will end up in the hospital and 3,000 will die.
Highest levels of phytohaemagglutinin (PHA) occur in broad beans, white kidney beans (cannellini), and red kidney beans. Black beans, soy beans, and edamame can also cause issues if not properly cooked.
Arsenic in Lima Beans
Raw lima beans contain linamarin. When eaten, linamarin is converted into the toxic chemical hydrogen cyanide. Fortunately for lima bean-lovers, boiling lima beans for at least 10 minutes renders them safe. Lima beans sold in the U.S. are required to have relatively low cyanide levels.
Chickpeas and Green Beans
Inhibitor compounds found in chickpeas (garbanzo beans), green beans, soy beans, and edamame can cause potassium levels to increase in the blood. Most people will not have a problem but heart patients and kidney patients need to be careful. Potassium helps manage blood pressure, but too much can be harmful for heart or kidneys. People who use beta-blockers should be careful about consuming these bean family members.
And If That Wasn’t Enough
Phytic acid, or phytate, is an antioxidant found in all edible plant seeds, including beans. While not toxic, phytate blocks the absorption of iron, zinc, and calcium from the same meal. Over time this has been shown to increase the risk of mineral deficiencies in people who rely on legumes as a dietary staple.
Why Are We Telling You This?
When someone tells you they can’t eat beans, or soy, or humus, or even alfalfa sprouts (yes, alfalfa is a legume) they are not making it up. Their body can not tolerate the bean toxins. We always advocate that you safely savor your foods.
Science Nerd Note phytohaemagglutinin dissected: phyto = plant haema = hemaglobin in human blood, glutinin = coagulation or clumping together
Food Poisoning from beans on Thought Co.
State Food Safety on toxic beans.
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