Many “natural-know-it-alls” and wellness gurus blame nightshade vegetables for just about every health problem you can imagine. Especially arthritis and joint problems.
But those breathless warnings are more about peddling superstition (which is certainly appropriate for the season) than they are about science.
So, today, I’ll discuss the basis of the concerns about nightshades. Then, I’ll give you some tips for figuring out if you really should cut them out of your healthy diet—or not!
Why do people fear nightshade vegetables?
After all, those plants (along with eggplant, goji berries, and tobacco) belong to the same family—called Solanaceae—as another plant that they knew and feared…
The deadly nightshade (Atropa belladonna).
This specific perennial plant—also known as belladonna (which means “beautiful lady” in Italian)—sounds like something Uncle Fester might grow at the fictional Addams’ family house. (The Addams’ family house was modeled on an old building on the campus of my alma mater, University of Pennsylvania.)
But it’s actually a very REAL plant that was already well-known in Europe by the 1400s. In fact, women often used drops from the deadly nightshade to dilate their pupils and make them look more seductive.
The plant contains a high concentration of compounds—called glycoalkaloids—that are so toxic, even a small amount slipped into a drink can cause paralysis, severe hallucinations, delirium, confusion, convulsions, and death.
But there’s an important distinction here…
Modern studies show high doses of glycoalkaloids can cause the membranes of red blood cells and mitochondria (your cells’ energy factories) to break. This mechanism has led some scientists to wonder whether glycoalkaloids may contribute to irritable bowel problems, such as acute diarrhea and gas, as well as chronic problems, such as “leaky gut” syndrome.
High doses of glycoalkaloids may also act as neurotoxins—causing muscle spasms (which may lead to convulsions), cardiorespiratory arrest, paralysis, hallucinations, dizziness, confusion, and even death. (For some perspective, military nerve gas weapons and the common pharmaceutical agent atropine both work in this same way.)
In other words, the deadly nightshade plant that Europeans feared was so toxic because it contains very high amounts of these compounds. But NOT all nightshade vegetables in the Solanaceae family contain this high amount.
When it comes to glycoalkaloids, dosing matters!
All nightshades, like most other plants—including apples, beets, and cherries—produce some glycoalkaloids. They act as natural pesticides to protect against predators, such as insects, and other dangers, such as bacteria, fungi, and viruses.
But nightshade plants such as peppers, potatoes, and tomatoes contain much lower amounts of them, compared to the deadly nightshade.
Plus, it’s important to know that the toxins are concentrated in the plant’s flowers and leaves…as well as in the plant’s unripe “fruit.” That’s why you should avoid eating raw nightshade vegetables…and especially green or “sprouted” potatoes. (Remember, the “fruit” is the part of the nightshade plant that you consume. There are two exceptions: With potatoes, one eats the tuber. And with tobacco, one inhales smoke of the burning leaf.)
I should also mention that modern science shows that ingesting lower amounts of glycoalkaloids can actually confer some impressive health benefits. In fact, in lab studies, they appear to manifest a steroidal-like effect, reducing inflammation.
They also have natural, anti-bacterial, anti-viral, and even anti-cancer properties. (This anti-cancer mechanism, which causes cancer cells to self-destruct, is called “apoptosis.” Big pharma tries to simulate this mechanism in some of their experimental cancer treatments.)
Nightshades also contain lots of vitamin C and other important nutrients. For example, tomatoes are an excellent source of lycopene (which I helped discover in the mid-1980s). It’s a carotenoid with potent health benefits—especially for the prostate.
For me, here’s the bottom line…
People around the world have been enjoying nightshade vegetables without incident for thousands of years.
So, if you enjoy eating potatoes, eggplant, tomatoes, and peppers without ill effects, you can continue eating them in moderation. However, if you’ve noticed gastrointestinal (GI) upset, headaches, joint pain, heartburn, or sleeplessness after eating these foods, you may have some sensitivity to them.
The only real way to know if nightshades are a problem for you is to cut them completely from your diet for a few weeks and see how you feel. Then, you can reintroduce them one at a time. If the symptoms return, you’ve got an answer.
It’s also important to keep in mind that cooking nightshade vegetables lowers their glycoalkaloid concentration. So, you may find you have better luck tolerating them when you throw them on your stovetop or into your chilis and soups. (And, of course, potatoes always take a lot of cooking.)
Well…now that you’ve got the latest science about nightshade vegetables, you can leave the superstition to the witches, occult herbalists, and internet trolls. And for more insight into some other common food myths, check out the July 2021 issue of my monthly newsletter, Insiders’ Cures (“The science-backed strategy to conquering arthritis in your own kitchen”). If you’re not yet a newsletter subscriber, now is the perfect time to get started!
“How Deadly are Nightshades?” Diagnosis Diet, 5/1/19 (diagnosisdiet.com/nightshades/)