Miguel Angel Sabadell

Some of the world’s most important food crops contain toxic compounds that require cooking or combining with other foods to be safe. It is not bad that we take note.


The scientific name of this plant is Lathyrus sativus and its common name depends on the place: almorta, alverjón, bichas, cantuda, cicércula, pea, tooth of the dead, fréjol de yerba, garbanzo de yerba, guija, muela…

This pea has been a staple food in the Mediterranean, Africa, India and parts of Asia for centuries. Like most legumes, it is an excellent source of protein, but it has one serious drawback: it contains a neurotoxin called beta-N-oxalyl-diaminopropionic acid or beta-ODAP. The first symptom of beta-ODAP poisoning, or lathyrism, is the weakening of the legs. Over time, the toxin kills nerve cells and victims are left paralyzed from the waist down.

How is it that this legume remains such a popular ingredient in flours, porridges and stews? If they are soaked for a long time in water or fermented into breads or pancakes, they do not pose a risk. On the other hand, its popularity lies in the fact that the pea is one of the few food crops that survives a severe drought. In these cases, with people without much else to eat and without enough water to soak them… We can already imagine the result.

Peas contain a neorotoxin. Photo: Istock

This problem has been known since Greek times: Hippocrates warned that people who “eat peas continuously become impotent in their legs.” Poisoning from excessive consumption of peas is called lathyrism (from lathyrus, the Latin name for the pea). Francisco de Goya described the ravages of lathyrism in his 1810 engraving entitled Thanks to Almorta. In it he portrayed the havoc caused by the consumption of this plant during the Spanish War of Independence.


Native Americans knew how to prepare this crop safely. Traditional recipes required add slaked lime (calcium hydroxide), a natural mineral, to corn. Without it, the niacin (or vitamin B3) contained in corn is not absorbed by the body, which is not a problem unless corn is our only food source or makes up the majority of a person’s diet. When that happens, as it did with early settlers who were unaware of the risk they faced, the result is a severe niacin deficiency called pellagra. As early as 1735, when corn was imported from the New World, poor people in Spain and other European countries were showing symptoms of pellagra, which became known in the Anglo-Saxon world as the four D’s: dermatitis, dementia, diarrhea and death (death).

What’s more, researchers have suggested that the symptoms of pellagra may have inspired by the European myth of vampirism: pale skin that broke out in blisters when exposed to the sun, sleepless nights caused by dementia, inability to eat normal foods due to digestive problems, and a morbid appearance just before death.

Corn poisoning could have given rise to the myth of the vampire. Photo: Istock


Present in much of Anglo-Saxon pastry, the leaves of this plant of Asian origin that arrived in Europe through Silk Road contain high levels of oxalic acid. In fact, rhubarb is the edible plant with the highest concentrations of this acid, more than spinach (which is why they should be eaten in moderation). Rhubarb poisoning causes weakness, difficulty breathing, gastrointestinal problems, kidney stone formation, and can even lead to coma and death. Thus, in 1917, the Times of London reported on the death of a minister who died after eating a dish made from rhubarb leaves. The unfortunate cook admitted that she had used a recipe she found in the newspaper titled “Advice from National Cooking Schools in Wartime.”

Rhubarb contains the highest concentration of oxalic acid. Photo: Istock


There’s a reason grocery stores don’t sell raw cashews. Cashew nuts are part of the same botanical family as poison ivy, poison oak and poison sumac. The cashew tree produces the same irritating oil, urushiol, with the symptoms edema, inflammation, suppuration, and in extreme cases a burning sensation. According to American Academy of Dermatology 50 million cases of this dermatitis occur annually in the United States alone.

The nut is perfectly safe to consume, but if we touch any part of the shell it can cause itching and a very unpleasant rash. For this reason, cashews are not sold in their shell and the nut is usually sold steamed. Now, the shell should not be thrown away: the cardanol it contains is being investigated for its possible applications in nanomaterials and biotechnology.

The cashew shell causes dermatitis. Photo: Istock

red bean or kidney bean

A valuable source of plant protein, beans are a staple in many vegetarian and vegan diets. However, they contain lectins such as phytohemagglutinin, proteins that can cause nausea, vomiting and diarrhea intense if consumed raw. That’s why cooking beans thoroughly is crucial to ‘deactivate’ these substances and make them safe for consumption. But attention! It only takes four or five raw beans to cause these symptoms. What’s more, one of the most common sources of kidney bean poisoning is cooking them in a slow cooker.

Eating undercooked beans causes diarrhea. Photo: Istock


This member of the dreaded nightshade family -source of poisonous alkaloids- contains solanine, a toxic glycoalkaloid that can cause burning and gastrointestinal problems and, in extreme cases, coma and death. Cooking a potato will kill most of the solanine it contains, but if has been exposed to light long enough for your skin to turn green, that’s a sign of elevated solanine levels.

Potatoes contain a toxin called solanine. Photo: Istock


Of this important food crop in Latin America, Asia and various parts of Africa, the root is cooked in much the same way as potatoes. There’s only one problem: cassava contains a substance called linamarina -which is also found in beans and flax- which turns into cyanide in the body. It can be removed by careful preparation involving soaking, drying, or baking the root, but this process is imperfect and can take several days.

Excess consumption of cassava causes a disease called konzo. Photo: Istock

In times of drought, cassava roots can produce higher levels of this toxin, and people in areas affected by famine due to drought may eat more of this root and take less care with preparation. Cassava poisoning can be deadly; even at lower levels it causes a chronic disease known in Africa as konzowhose symptoms are tremors, lack of coordination, vision problems and paralysis.