Everyday Food That Can be Poisonous

All plants have some form of chemical or physical protection for themselves in their daily fight for survival. In food plants, some of those protections we may biologically experience as toxins. We cooks are often the last line of defense to mitigate the toxins our food pants may contain. This post is about the most common plant toxins, and how to remove or lower them in the food we eat.

But this is not a complete list, just the food I tend to use a lot. Remember, I am not a scientist, nor medical professional, I am just a cook. So if this matters to you, please talk with a nutritionist for further information, or do your own research.

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Food Plants Protect Themselves with Toxins

Let us have an honest conversation about eating plant-based food. Plants have spent thousands of years fighting predators, whether human, animal, insect, mold, or microorganisms. Over time, each plant has found a way to fight off their predominant attacker, so trees may grow long thorns when the major predator is giraffes. Coffee trees and their berries use a tobacco chemical that, at certain doses, is poison to their predators, and on down the list of plants.

The UN was my initial source for the details in this post. For human health and welfare, and animals too, we should be is lowering the toxins we consume as much as possible. Unfortunately, nearly everything can be toxic, but luckily it is all a matter of how much we consume at one sitting, and if it is passed or accumulates in our bodies.

Meanwhile, despite governmental assistance in this area, the bottom line responsibility for assuring we are not making ourselves or family sick, rests with us the cooks, foragers, and farmers.

Toxins

Let’s start with what are toxins:

• Toxins are substances that plants create to harm their predators, while being harmless to the plant itself.
• Toxic plant substances can be poisonous to humans, depending upon dose or preparation.
• Adverse health effects to consuming toxins may include acute poisoning ranging from allergic reactions, to severe stomachache and diarrhea, to even death.
• This is different than a plant that grows thorns, like Meyer Lemon or Lime bushes.

Here are a small list of toxins typical in food plants, but this is not a thorough review of these toxins, but enough to give you an idea about them.

Cyanogenic glycosides are phytotoxins (toxic chemicals produced by plants) and can be found in at least 2k plant species, including food plants. Think cassava, sorghum, stone fruits, apples, pears, bamboo shoots, and almonds, among others (1).

• While there is some confusion, I am including apples and pears (technically pome fruits) as they have similar toxins in their seeds.
• Stone fruits including peaches, nectarines, plums, apricots, cherries and almonds are in the genus Prunus, belonging to the Rose family – Rosaceae (2).

Fyriciynarubs are phytotoxic (can cause severe skin reactions in sunlight), and are toxins that are released when the plant is stressed primarily through being damaged) Examples of these plants are parsnips (closely related to carrots and parsley), celery roots, citrus plants (lemon, lime, grapefruit, bergamot) and some medicinal plants. If sensative to these toxins, humans get gastrointestinal problems.

Lectins are proteins that are naturally formed in legumes such as beans, peanuts, peas, lentils, chickpeas, nightshade vegetables (tomatoes, potatoes, bell peppers, eggplants), and grains such as wheat germ, chia, and quinoa (3).  Lectins have often been referred to as “anti-nutrients” because while they are not easily digested and travel through the GI tract unchanged, can unfortunately also reduce our ability to absorb certain nutrients.  When lectins are consumed in large amounts, they may cause GI irritation, resulting in severe diarrhea and vomiting. But also, specifically, castor beans contain a potent lectin poison called ricin. Many legumes that contain lectins can be reduced or removed through proper processing like soaking, and wet cooking at high heat for a set period time.

Mushrooms are also known for being toxic, if the wrong ones are picked and eaten. Which is why I would never forage for mushrooms. I have read too many stories of the death and severe medical complications coming from someone who picked and cooked wild foraged mushrooms.

Mycotoxins are toxic compounds produced by certain molds that grow on food like cereals, dried fruits, nuts and spices. It can happen before or after harvest, during storage or transportation, whenever the environmental conditions are right. Unfortunately, processing the food will not mitigate the toxins and can result in cancer or immune deficiency.

Overconsumption is another poisonous aspect of food. Drinking too much water can have acute toxic effects leading to hepatotoxicity. Eat too much licorice, and an intoxication caused by glycyrrhizic acid (licorice’s active component), may suppresses the renin-angiotensin-aldosterone axis, resulting in the loss of potassium, and can lead to death.

Pyrrolizidine Alkaloids are toxins produced by ~600 plant species. These toxins are detected in herbal teas, honey, herbs, spices, cereals and cereal products. Current estimates are that our exposure is low, but it is being researched (4, graphic above).

All solanacea plants, which include tomatoes, potatoes, peppers and eggplants, contain solanines and chaconine, which are glycoalkaloids. Glycoalkaloids are described as a group of nitrogen-containing compounds that are naturally produced in various cultivated and ornamental plant species of the Solanaceae family.

The way to avoid these toxins is to not eat certain parts of the food plant. At the same time, we need selenium for our health, but too much over a long time can cause harm; actual toxicity in humans however is rare (5).

Comment on Allergies

Allergies, in general, need to be considered when making food for people, and taken very seriously. So when someone has an allergy I will separate off a little space in my kitchen that I really clean and disinfect, and then use that area to prepare their food. Additionally I use different pots, pans and utensils. Meanwhile, the food I will be making will not contain a hint of that item, for in some cases even a whiff of the food can cause a reaction. This means peanut butter, shellfish, soy, tree nuts, etc.

But while allergies can cause biologic harms, the point is to avoid them, as no processing can make the person un-allergic to the food items. Toxins in plant food need avoidance or can undergo special processing to make them relatively harmless.

Specific Foods

Bitter Almonds

Bitter almonds, while in their wild raw form, are full of cynaide. They need to go through a specialized heat treatment in order to remove the toxins. I have read to remove the toxins are beyond a home cook’s ability; although I did read Tunisia makes an orgeat syrup from bitter almonds. Luckily, a sweet almond variation was found and that is what we have available to us in the USA.

I read a report that in response to two outbreaks of Salmonella in 2001 and 2004 traced to raw almonds grown in California, the Almond Board of California and the USDA have quietly developed a new regulation mandating that all almonds undergo a sterilization process that includes chemical and/or high-temperature treatments.

Asparagus Berries

Asparagus, whether green, purple or white, is a wonderful vegetable that millions of people eat the world over. However, the bright red fruit of this plant is toxic and causes gastro distress in humans. We would only see the berry if we planted the vegetable in our home garden for it is never in a grocery store.

Bean Sprouts

Food borne illnesses (like e.coli, listeria, and salmonella) are not known for being cooked out of food. There have been outbreaks from raw food, like sprouts, containing these critters because bacteria thrive in a warm, humid environment that sprouts happen to grow best in. So in general, I do not consume sprouts, and am now also leery of open salad bars.

Here are some tips from EatRight to mitigate these bacteria:

• Buy only fresh sprouts that have been properly refrigerated.
• Do not buy sprouts that have a musty smell or slimy appearance.
• At home, refrigerate sprouts right away in a clean refrigerator at 40° F or below.
• Wash your hands properly before and after handling raw sprouts.
• Rinse sprouts thoroughly under running water before use.
• If you decide to cook sprouts, it can help reduce the risk of food poisoning. Toss them into soups, stews or stir fries near the end of the cooking process — or oven roast until crisp and browned.

Cashews

When truly raw, cashews contain urushiol, a resin that can create significant skin rashes, and can be toxic when ingested (6). Most of the cashews we get, even if they are labeled in the store as raw, have been steamed (7) to remove the toxin.

Cassava

I saw sweet cassava root is a favorite vegetable for many, and are sold in food market that cater to many world cuisines. And certainly cassava flour has become a popular gluten-free alternative. But the cassava’’s leaves and roots are rich in cyanide where just 2 roots can carry a fatal dose.

To mitigate the poison MedicalNewsToday indicates the root must be peeled, cut into small pieces, and left in water to soak for 4-6 days. That water is disposed, then fresh water is added and heated to a boil until tender, then that water too is discarded. Then they say: Bitter varieties of cassava require more extensive processing, such as grating or pounding and soaking in water, before boiling. However, bitter cassava is not common in the U.S.A.

Personally I will bypass working with this root raw, but will still consume it as part of a dish someone more knowledgable than me has prepared.

Mushrooms

A number of mushroom or toadstools are poisonous, whether eaten raw or cooked. For non-trained individuals, foraging for mushrooms is extremely dangerous given how hard it is to tell between safe and dangerous species. There have been too many stories of someone picking a mushroom they think they know, going home, cooking and serving them to their family, only to have everyone sick the next day. I have read of some of those family members needing liver transplants, some with permanent neurological damage, and some have died.

The toxins in mushrooms are produced naturally, by the fungi themselves. And most of these poisonous mushrooms cannot be converted to a nontoxic status by cooking, canning, freezing, or any other means. Thus I do not forage for mushrooms, and only buy mushrooms from grocery stores, or from a farm growing only safe species.

Red Kidney Beans + Kintoki Beans

Buying and cooking your own beans is a great way to save money, as dried beans are often very cheap when compared to canned or jarred beans. However, dried red kidney beans and Kintoki beans come with a very big concern. According to the Food and Drug Administration (FDA, page 254), these beans contain toxic levels of lectin, which are proteins that bind to carbohydrates. Now all beans contain some of this, but these specific beans have a higher concentration. Consuming even just a few beans, when not properly prepared, can cause vomiting, diarrhea and gastrointestinal illness for several hours.

Phytohaemagglutinin, the name of the actual toxic agent, is found in many species of beans, but is highest in red kidney beans (Phaseolus vulgaris). Raw kidney beans contain from 20,000 to 70,000 hau (hemagglutinating unit), while fully cooked beans may contain ~200 to 400 hau.

To cook properly, the following needs to occur (8):

• Soak raw red kidney beans for at least 5 hours, and discard the water.
• Boil red kidney beans in clean, fresh water for at least 30 minutes, but an hour or two is better.
• Cook these beans by boiling on stovetops and not in a slow cooker or in a casserole in the oven, for neither get hot enough to kill off the toxins.
• I personally only use canned kidney beans since they are thoroughly boiled during the canning process and their processes safely remove the toxins.

Green Potatoes + Plants

We have all heard the warning to not eat green potatoes. When exposed to sunlight potatoes can turn green and sprout, and in that process produce a number of alkaloid glycosides containing the cholesterol derivative solanidine. Two of these glycosides, solanine and chaconine, are found in high concentration in the peels and sprouts, but are also found in potato leaves, stems, and shoots (9).

Clinical manifestations of solanine and chaconine poisoning intoxication occur within 7-19 hr after ingestion. The most common symptoms are vomiting, abdominal pain, and diarrhea; in more severe instances of poisoning, neurologic symptoms, including drowsiness, apathy, confusion, weakness, and vision disturbances, are rarely followed by coma or death. However, studies suggest doses of 200–400 mg for adult humans can cause toxic symptoms (20–40 mg for children). Most commercial potatoes have a solanine content of less than 0.2 mg g⁻¹.

• Some solanine can be removed by boiling but not by baking (10).
• But you have to remove the skin, eyes, and flesh of any green parts of the potato.

If I can peel away the green of a newly greened potato and see healthy flesh I will use the potato, but not if there is a whole sack of them. If the potato is green, sprouting, and a bit wrinkly, I will cut it up and plant them. Usually, potatoes do not last long enough in my house to go to waste.

Peanut Allergy

Most of us who have had children are aware of the peanut allergy that can cause severe reactions in some, leading to hospitalization and even death. Many schools have prohibited peanut butter as a result. Anyone coming to my house to eat who has such an allergy knows to inform me so I can make sure to take special care.

Rhubarb Plant

I have always been fascinated by this plant, it has a reddish stalk that looks like celery but has a very sour taste. With enough sweetener, that favorite sweet-n-sour flavor comes forth to flavor many a jam and pie.

Rhubarb leaves are very high in oxalic acid, which can quickly causes kidney failure in humans if consumed at high enough doses. About 25 grams of pure oxalic acid is the average amount needed to kill a human, but this is hard to do as you would have to eat ~11# of leaves (11).

Stone Fruits

This category of fruit includes (12): cherries, peaches, apricots, plums, nectarines, mangos, and all those fruit with a stone or pit inside of it. We can comfortably eat the flesh, it is the pit that we need to be careful of due to it containing cyanogenic glycosides, which converts into cyanide. Actually the process is this, the seed contains a substance called amygdalin, which turns into cyanide when it comes into contact with acids in the human digestive system. This cyanide prevents the cells from getting oxygen, and we can die.

The mitigation of these foods is to not let anyone suck on or crush and consume those pits, including your pets. GoodHousekeeping writes hydrogen cyanide is not a heat-stable substance and does not survive cooking, which is why you may see some recipes that call for roasting stone fruit pits. They further say you would have to eat a lot of the seeds to have a reaction.

Personally, I just compost the pits immediately and do not bother with them.

Tomato Plant

Early Europeans called the tomato the “poison apple” because many people who ate the plant fell ill afterwards and died. Of course this was a time of pewter tableware and they did not know the acidic tomato interacted with pewter to release lead and it was the lead that killed (13).

Since then we have learned that while the ripe fruit is wonderfully edible, there are parts of the plant to avoid. What we need to avoid are the leaves, roots, and stem. These parts are rich in tomatine and solanine, alkaloids that are toxic to humans. While it may not kill anyone, it does cause severe gastro issues, if you eat a fair amount of the green leafy parts.

I buy fresh tomatoes, heirlooms are my preference, or I buy Pomi seedless and skinned tomatoes in a box, or glass containers. I do not buy canned tomatoes for historically the acidity has leached BPA from the cans into the food so I am shy of those.

Many of the mitigation activities I was already doing, but did not know why. They were just handed down to me as the proper way to prepare the food. We cannot lose the tips and tricks our foremothers knew. because they held the key to keeping our food safe.

For instance, regarding leftovers: if you let cooked food sit unrefrigerated for 4 hours, between 40F and 140F (or 4.4C to 37.8C) temperature, then you should compost it or throw it out. Or take a chance of illness, or even death.

—Patty

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