“Natural is better.”
“Natural is safer.”
These words are easy to say and they sound good, but they can be very wrong. You can’t assume that just because something is natural means it is safe.
Natural pesticides can be just as deadly as chemical concoctions. Mushrooms may be natural and organic, but some of them can kill you. Even the seeds and skins of some of our common foods can cause illness or death when eaten to excess.
Chemical warfare may be banned in the human world (and with good reason), but plants regularly employ chemicals to defend against insect and herbivore feeding and in response the injury and environmental stresses. Some of the chemicals they use can hurt us, too.
Today we are looking at some of the natural toxins growing in our gardens and lurking in our crisper drawers.
Apples, barley, and stone fruits
The seeds of apples and the pits of stone fruits contain cyanogenic glycoside. When plants feel they are being attacked, they remove the sugar molecule from these compounds, converting them into hydrogen cyanide. Barley, flax, and sorghum do the same thing. Raw cassava (tapioca) and bamboo shoots also contain hydrogen cyanide. Hydrogen cyanide is a blood agent that halts cellular respiration. It will kill you if you eat too much.
Cereals, dried fruits, nuts, and spices
Have you ever nibbled raw cookie dough? I have. And I’ve heard that I shouldn’t. I always thought that was because of the raw eggs, but it ends up that bird poop residue is the real reason. Another problem with this food group is more serious than a short-term belly ache. Cereals, dried fruits, nuts, and spices can harbor certain molds, called mycotoxins, that can cause severe illness. Long-term exposure, while rare, can cause immune deficiency and some cancers.
Herbs, honey, and sunflowers
Herbs, honey, and members of the sunflower family all contain something called pyrrolizidine alkaloids. Milk, eggs, and cereal grains also contain these chemicals, which are known to cause liver damage. Borage leaf, coltsfoot, and comfrey contain particularly high levels of this natural toxin. Remember, the damage is in the dose.
Raw kidney beans are dangerous. There, I’ve said it. I didn’t even know it until I wrote this post. It ends up that all raw beans contain chemicals called lectins. Lectins can cause severe digestive upset. Raw kidney beans contain more lectins than other beans. Low and slow cooking may be great for that pot roast, but those temperatures may not be high enough to destroy lectins, so be sure to crank up the heat for at least part of your bean cooking regime.
Some people can forage safely for mushrooms and others cannot. I’m in the latter group. Because some mushroom species can kill you, I opt for the grocery store. Unlike some other toxins, those found in mushrooms are not destroyed by cooking.
Parsnips have a chemical arsenal of their own. When they feel threatened, they produce chemicals known as furocoumarins. These chemicals can cause stomachache and skin rashes. To avoid these problems, peel your parsnips and discard any damaged bits. And pour the cooking water down the drain, rather than adding it to your soup stock. By the way, carrots, parsley, celery root, and citrus contain furocoumarins, too.
We’ve all seen it. Just under the brown skin of a potato, you see green. These green areas occur when a potato is sprouting and when the plant feels stressed. Along with that green tinge are chemicals known as glycoalkaloids. All members of the nightshade family contain these chemicals. Mostly found in the leaves, glycoalkaloids can give you a bad belly ache. They can also kill you. Be sure to remove any green or damaged bits before cooking your potatoes. If they taste bitter, toss them in the trash.
I’m only including rhubarb because everyone seems to have heard how toxic their leaves are. They do contain oxalic acid. It’s also true that oxalic acid can cause cramps and interfere with breathing and heartbeats. It can also cause coma and death, but you’d have to eat a profound amount of rhubarb leaves to have a problem.
Sweet potatoes can produce toxins used in defense against injury, insect feeding, and other stresses. One of these toxins, ipomeamarone, makes your sweet potatoes taste bitter. It can also kill you, so don’t eat bitter-tasting sweet potatoes and always cut out and discard damaged areas.
Bitter-tasting zucchinis may contain chemicals known as cucurbitacins. Cucurbitacins cause something called “toxic squash syndrome”. Symptoms of this condition include severe digestive upset followed by hair loss, weeks after the fact. How weird is that?
With all these potential toxins in our food, what’s a gardener to do?
First of all, recognize that you would have to eat an awful lot of most of these plants to cause any real harm. Second, keeping your plants healthy with proper fertilizing, irrigation, and pest and disease control reduces their need for self-defense.
You can protect yourself and your family by discarding any produce that is badly damaged or moldy and cooking your food properly.
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Kate Russell, writer, gardener, and so much more.