8 Fruits and Veggies That Could Be Considered Poisonous

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What do ackee, cassava, cycad, lychee, potatoes, red kidney beans, starfruit and sugar cane have in common? While that question may sound like the opening line of an offbeat joke, the health-related similarity these fruits and vegetables share is no laughing matter.

Plants, like animals, employ various strategies to ensure their survival, and naturally occurring toxins help some plants resist disease and insects.

While you may think everything in nature is suitable for human consumption, each one of the fruits and vegetables mentioned above contains small amounts of toxins that may harm your health when ingested at certain times or in large amounts.

As reported by CNN,1 there are important considerations you must keep in mind should any of these “natural-born killers” appear on your grocery list.

Ackee: Jamaica’s National Fruit Must Be Cooked Before Eaten

In Jamaica and West Africa, where the ackee fruit is grown, the toxic risks of the plant are well understood. Similar to starfruit, unripe and unopened ackee contains a poison known as hypoglycin, which, according to Medscape,2 can lead to a potentially fatal toxicity known as “Jamaican vomiting sickness.”

Nonetheless, ackee endures as the national fruit of Jamaica, even taking its place alongside saltfish as part of the country’s national meal.

Given its mild flavor and buttery, creamy texture, ackee is usually treated as a vegetable in cooking, as opposed to a fruit. It is used in many savory dishes because it pairs well with other vegetables, meat and fish.

To ensure the elimination of potentially harmful toxins, ackee is most often boiled, and always must be cooked before it can be eaten. Most natives know what to do in cases where unripe ackee is ingested, says Peter Spencer, Ph.D., professor of neurology at Oregon Health and Science University School of Medicine:

“It’s well-known in Jamaica if your child eats an unopened or unripe ackee fruit, you better get ready to take them to the hospital or give a spoon of sugar to increase glucose.”

An outbreak of epidemic fatal encephalopathy that killed 29 school-aged children in Burkina Faso, West Africa, was linked to ackee poisoning.3 Due to its potentially lethal nature, authors of a 2004 study4 published in Food and Chemical Toxicology, validate Spencer’s suggestion to administer sugar quickly. They said:

“[C]onsidering the high lethality of ackee intoxication, the total absence of any existing treatment and the safety of glucose administration, we recommend at this stage to use early sugar or glucose administration in the field, in addition to a specific population-based prevention program.”

Cassava Root Naturally Contains Cyanide

According to CNN,5 cassava, also known as yucca, follows closely behind corn and rice as the most important calorie source in Africa, South America and parts of Asia. Some 600 to 800 million people worldwide are believed to consume cassava daily.

Cassava is most commonly baked, boiled or fried, releasing a gummy, starchy texture. It can also be ground into flour.

Organic cassava is a primary ingredient in my cocoa-cassava gourmet snack bars, one of my favorite occasional treats. Processed under rigorous health and safety standards, the organic cassava used in my snack bars adds a hint of sweetness and moisture, as well as calcium.

Regardless of its preparation method, cassava must be processed properly; otherwise it is poisonous. “It feeds millions across the world,” Spencer notes. “But if you’re very poor and don’t have time to process it, then you come down with disease.”6

Of the two main types of cassava — sweet and bitter — bitter contains the most concentration of a cyanide-inducing compound called cyanogenic glycosides, more than 50 milligrams per kilogram. Hydrogen cyanide is released from the cyanogenic glycosides through chewing when it is mixed with enzymes, resulting in the release of hydrogen cyanide.

Whereas the sweet variety only requires boiling to reduce its potential cyanide content to non-toxic levels, the bitter root contains more toxins and therefore requires both soaking and cooking prior to consumption.

Signs of cyanide poisoning include convulsions, diarrhea, mental confusion, stomach pain, twitching and vomiting. According to the U.S. National Institutes of Health,7 cassava’s toxins can also cause sudden, irreversible paralysis, commonly known as “konzo.”

Konzo most often affects people living in developing regions affected by armed conflict, drought or famine, who may be at risk of eating cassava unprocessed. According to the authors of a 2011 study published in PLOS — Neglected Tropical Diseases:8

“Increasing cassava production, declining production of other foods, global warming, more frequent droughts, wars and population displacement have set the scene for konzo to persist …

Immediate interventions to prevent konzo in affected areas, such as … the wetting method to detoxify cassava flour in some affected areas, are essential.”

Says Dr. Desire Tshala-Katumbay, staff scientist at the Oregon Institute of Occupational Health Sciences:9

“There is more attention [being given] to the problem and more research is being done. I hope in time we will get enough expertise to … think about interventions to protect children from brain damage related to malnutrition and cassava toxicity.”

The video below, produced by a Kenyan news station, highlights the negative effects of ingesting unprocessed cassava.


Cycad Toxins Must Be Removed Before Any Part May Be Eaten Safely

Cycad sago is a starch extracted from the stems of ancient, highly toxic palm-like plants that grow in tropical regions around the world. Sago is used for both food and medicine but, like cassava, requires extensive processing to be safe for human consumption.

Sago can be rolled into balls, mixed with boiling water to create a glue-like porridge called papeda, formed into pancakes or produced commercially in the form of “pearls.”

Sago pearls, which are similar in appearance to pearled starches such as potato or tapioca, can be boiled with sugar and water or milk to make a sweet pudding. “This is an ancient plant, but is one of the most toxic plants on the planet,” Spencer noted.

“It’s strongly implicated in the induction of neurodegenerative disease.”10 For example, consumption of cycad seeds may play a role in Guam disease, a neurological disease similar to Alzheimer’s and Parkinson’s common to the island of Guam, where the plant originates.

The process of detoxifying cycads varies by region, but generally involves aging, cooking, fermentation and washing. Regardless of the method, two known neurotoxins, BMAA (B-methylamino-L-alanine) and cycasin, must be removed before any part of the cycad plant can be safely eaten.

Sago is nearly pure carbohydrate and has very little nutritional value. Sago cycad trees are commonly found in areas unsuited for other forms of agriculture. Because they thrive in drought conditions, sago cycads are commonly known as a famine food. A 2014 study, published in Neurología, underscored the importance of taking a cautionary approach to cycads. Researchers noted:11 

“Cycads contain neurotoxic compounds that may contribute to the development of neurological diseases when ingested improperly. We must be mindful of the fact that while some plants … may fill the food gap for vulnerable populations, they can also be toxic and have a negative impact on health.”

Lychee Toxins Can Lead to Fever, Convulsions and Seizures

Despite its spiky exterior, when enjoyed at its peak, lychee fruit can be smooth, juicy and beautifully sweet. Unfortunately, this tasty exotic fruit, also known as litchi, can be toxic and sometimes fatal when eaten before it is ripe. Malnourished children are at particularly high risk for serious illness and death from lychee poisoning.

Lychee toxicity is thought to be the cause of a mysterious illness that has affected the town of Muzaffarpur in Bihar, India, the country’s largest lychee-producing region, annually since 1995. Every year around May and June, hundreds of children have been hospitalized due to convulsions, fevers and seizures, attributed to what locals call “chamki ki bimari,” or “tinsel disease.”12

A report13 published in The Lancet Global Health medical journal claims the devastating disease is very likely caused by lychee. One of the study authors, Dr. Padmini Srikantiah, neurologist and lead investigator in Muzaffarpur on behalf of the U.S. Centers for Disease Control and Prevention office in New Delhi, suggests toxins from unripe lychee can cause extremely low blood sugar.

Dangerously low blood-sugar levels set the stage for encephalopathy, a disease that affects the function or structure of your brain. In the Lancet report, Srikantiah and her team shared the following comments related to lychee consumption and the mysterious illness plaguing Muzaffarpur’s children:

“[T]o the best of our knowledge, this is the first comprehensive confirmation that this recurring outbreak of acute encephalopathy is associated with both hypoglycin A and MCPG (methylene cyclopropyl glycine) toxicity from [lychee] consumption. This illness is also associated with absence of an evening meal.

To prevent illness and save lives in Muzaffarpur, we recommended minimizing [lychee] consumption among young children, ensuring children in the area receive an evening meal throughout the outbreak season, and implementing rapid glucose correction for children with suspected illness.”

Potatoes Can Be Poisonous When Sprouted or Green in Color

While potatoes originated in South America, they are cultivated worldwide today, taking their place as the world’s fourth largest crop. Despite boasting more than 100 varieties, the majority of potatoes sold and consumed are in the form of greasy French fries or potato chips. Processed potato products contain trans fat and very often chemical additives and other processed ingredients that contribute to chronic health conditions such as cancer, heart disease and obesity.

According to Medline Plus,14 while most potatoes are safe for consumption, you should definitely avoid eating potatoes that are green in color or those that have sprouted, unless you have removed the sprouts. This is due to the likely presence of a toxin called solanine, which develops with exposure to light. For this reason, always store potatoes in a cool, dark place, but never in the refrigerator.

If you eat too many toxic potatoes, you may experience vomiting, stomach and abdominal pain, hallucinations and even paralysis. Signs of solanine toxicity include a bitter taste or burning sensation. If you think you are at risk of poisoning, call your local poison-control center. In the U.S., the national toll-free number for the American Association of Poison Control Centers is 1-800-222-1222.

While not immediately life-threatening, consuming fried potatoes also puts you at risk for a cancer-causing and potentially neurotoxic chemical called acrylamide. Acrylamide is the byproduct of a chemical reaction between sugars and the amino acid asparagine at temperatures above 250 degrees F (120 degrees C).

Carbohydrate-rich foods such as French fries and potato chips, which are heated to very high levels to produce a browned or charred surface, are likely to contain high amounts of acrylamide.

Red Kidney Beans Should Not Be Eaten Raw

The toxin phytohemagglutinin is common in many varieties of beans, but concentrations are especially high in raw, red kidney beans. Fortunately, by cooking red kidney beans you can reduce the toxicity level sufficiently for them to be safely eaten. The U.S. Food and Drug Administration (FDA)15 states eating as few as four or five raw beans may cause symptoms, which generally develop within one to three hours.

Onset of phytohemagglutinin toxicity is often marked by extreme nausea, followed by vomiting (potentially severe) and diarrhea a few hours later. Some sufferers also report abdominal pain. Recovery is generally quick — within three or four hours after symptoms begin.

If you use a slow cooker or Crock Pot to cook red kidney beans, take care to ensure the beans are cooked at a sufficiently high setting to destroy the toxic lectin. The FDA notes several incidents of poisoning have been associated with the use of these kitchen appliances.16

While somewhat less toxic, white kidney beans, also known as cannellini beans, also should be cooked thoroughly before eating. Cannellini beans contain about one-third of the toxicity of red kidney beans when consumed raw.

Starfruit Toxins Dangerous for Those With Compromised Kidney Function

Starfruit, so named for its shape when cut, originated in Asia but is now grown in warm climates around the world. It is used as an herbal remedy for a range of ailments, such as coughs, headaches, parasite infections and vomiting. Starfruit boasts a yellow-greenish skin, and its taste ranges from bitter to sweet. The sweet type is known to have thicker flesh.

While generally safe for most consumers, starfruit contains a neurotoxin your body will not be able to safely process if you suffer from kidney disease, says the U.S. National Kidney Foundation.17 Symptoms of starfruit poisoning include hiccups, mental confusion, seizures and sometimes death.

A 2015 study18 suggests individuals with healthy kidneys should take care to not overconsume starfruit given the possibility of developing kidney problems due to excessive or prolonged consumption. As such, I recommend you eat starfruit only occasionally.

Sugar Cane Dangerous if Moldy Due to Common Fungus

Given my beliefs about the negative effects of sugar on your body, as well as the addictive nature of sugar, I would never recommend eating raw sugar cane. Another reason you should avoid consuming raw sugar cane relates to the presence of a common fungus that develops when the cane is stored for several months.

The fungus, called artbrinium, produces toxins in both adults and children that may result in coma, convulsions, dizziness, headaches, spasms, staring to one side and vomiting. Children, however, are at greater risk. Spencer said, “If a child eats that fungus, it can cause death or lifelong neurological disease.”19

Sugar cane has been noted as one of the top 10 mycotoxic foods, as outlined in the book “Mold: The War Within,” by Kurt and Lee Ann Billings. In simplest terms, mycotoxins are fungal poisons. The Billings present many natural treatments for mold toxicity, which may be of interest if you have a sensitivity to mold.

Awareness Is Your First Line of Defense

The best way to avoid ingesting plant toxins is to be aware of what you are eating and informed about any potential toxins in your food. This article touched on a handful of fruits and vegetables — clearly there are countless other food items that may be of concern to you personally. It’s worth your time and your health to become educated.

In particular, you should take action if you believe something you’ve eaten once, or eat on a regular basis, may be having a negative effect on your body and sense of well-being. This is a good opportunity for me to remind you that it will be impossible to achieve optimal health unless you eat foods that nourish and support your body. If you have not yet had a chance to check out my Nutrition Plan, consider doing so today.