8 Fruits and Vegetables With a Poisonous Side

We know to avoid mysterious mushrooms, but some unassuming crops also pack a wallop of harmful toxins when eaten under certain conditions.

Plants are wonderfully wise and have devised all sorts of schemes to ensure their survival. Among other strategies, some entice pollinators to provide an assist in the romance department, some employ the elements to disperse their seeds, and some have developed small arsenals of chemical weapons to avoid being eaten by predators. It’s the last one that should concern us plant-eaters the most.

"The idea that all natural things are good for you is rubbish. We are eating [fruits and] vegetables that potentially contain bad things," Peter Spencer, professor of neurology and occupational health sciences at Oregon Health and Science University, tells CNN. Many plants "were not put here for our benefit but to protect themselves from predators,” he adds.

While not all of the following fruits and vegetables may be on everyone’s grocery list, they each have particular considerations to keep in mind.

1. Lychee

Sweet, floral beautiful lychee fruit seems as innocent as can be, but no. When eaten before they are ripe, toxins in the fruit can lead to extremely low blood sugar; for those with already low blood sugar or suffering from malnourishment, the toxins can lead to a host of problems from fever to encephalopathy to death. If you remember hearing about a mystery disease striking down Indian children every year, researchers finally tracked down the cause to, yes, unripe lychees. The area affected was near the country's largest lychee-farming region and the children were eating unripe fruit all day.

2. Raw Cashews

Raw cashews come complete with a resin called urushiol, which is the same compound that makes poison ivy so awful. It can cause pretty serious skin rashes and can be toxic when ingested or even fatal for anyone with higher sensitivity to urushiol. Now if you’re wondering why you’ve been eating cashews labeled “raw” and not had any problems, it’s because all commercial cashews are actually cooked to remove the shell. They’re sold as raw because they have not been roasted or further processed, but they have been cooked, and that’s a good thing.

3. Ackee

The national fruit and symbol of Jamaica, the ackee contains hypoglycin, the same toxin found in lychee. The threats from this native West African fruit are well-known amongst those who eat it and it’s rarely eaten uncooked or before it’s ripe. Unfortunately, not all children are aware of the danger and risk poisoning when they consume unripe ackee.

4. Cassava

One of the most important sources of calories in Africa, South America and parts of Asia, cassava fuels almost half a billion people around the world each day. But if not processed properly, cassava can release hydrogen cyanide, which can wreak havoc on thyroid hormones as well as affecting parts of the the brain relating to movement. Not to mention irreversible paralysis. That such an important source of nutrition is also so potentially toxic is vexing.

5. Starfruit

For some people, starfruit is decidedly not a lucky star, as it contains a potentially deadly neurotoxin for those with kidney disease. For people with properly functioning kidneys, the toxin caramboxin is handled without a problem. But for people with kidney problems, the toxic accumulates and can lead to everything from hiccups, vomiting, weakness, mental confusion, and psychomotor agitation, to unusually long-lasting epileptic seizures, coma, and death, according to a study on caramboxin.

6. Stone Fruit Pits

The pits of some stone fruits like cherries, apricots, plums, and peaches have a little secret surprise is hidden inside: Cyanogenic compounds! (In other words, the makings for cyanide.) Swallowed hole the pit will pass on through without a problem, but were you to chew it first or eat it already pulverized, things could get ugly. How much would do the trick? Anywhere between .5 and 3.5 milligrams per kilogram of body weight can be lethal. Experts at the European Food Safety Authority estimate that it is not safe for adults to eat more than three small apricot seeds in one sitting. For a toddler it only takes one small kernel to risk getting poisoned.

7. Potatoes

For all of our talk around here about not wasting food and not fearing a lack of perfection in produce – when it comes to potatoes, a little waste might be ok. If your spuds have taken on a greenish cast or have sprouted, step away, as it’s here that the toxic alkaloid solanine is particularly concentrated. Even so, one would need to eat a lot of green potatoes to get to the point of vomiting, stomach pain, hallucinations or even paralysis, but still.

8. Raw Kidney Beans

Thankfully, raw kidney beans are not that appealing. But I know that people on a raw food diet are often looking for novel ways to eat things without heat. Still, they shouldn’t try to get creative with beans. A lot of beans come with the toxin phytohemagglutinin, which comes in especially high concentrations in raw red kidney beans; and while cooking is enough to render the toxin harmless, just a handful of raw beans can kick symptoms into gear. On the bright side, recovery is pretty quick.

All of that said, this isn't meant to be a miserable message from the Doyenne of Doom, just a reminder to be careful. Please continue eating plants, and lots of them.