Nightshades: How Deadly Are They?

Nightshades have a bad reputation in a variety of chronic conditions, such as arthritis, fibromyalgia, and IBS. But what do we really know about how these foods affect our health?

At first glance, the nightshades may look like a random collection of foods that couldn’t possibly be related.

However, every nightshade plant produces fruits that all sport that same adorable little green elfish hat.

Nightshades of all types were considered inedible prior to the 1800’s, because some varieties, such as “deadly nightshade” (atropa belladonna) were known to be so toxic.

However, today most Americans eat “edible” nightshades every day in the form of French fries, mashed potatoes, salsa, spaghetti sauce, ketchup, and many other popular foods.

Of the foods below, only tomatoes, eggplants, goji berries and peppers are “fruits” (the potato is a tuber and tobacco is a leaf).

The fruits of potato and tobacco plants wear the same telltale hat, but we don’t eat the fruits of those plants. 

Meet the Nightshade (Solanaceae) Family

  • Tomatoes (raw)
  • Tomatillos
  • Tamarillos
  • Potatoes and starch from potatoes including “potato starch,” “starch,” and “vegetable starch” (sweet potatoes are not nightshades)
  • Eggplants
  • Bell peppers including green, red, orange, yellow, white, and purple
  • Banana peppers
  • Chili peppers (table pepper and peppercorns – black, white, green and szechuan are not nightshades)
  • Paprika
  • Cayenne
  • Red pepper seasonings and “spices,” “natural flavors” and some curry blends that contain paprika, chili powder and cayenne
  • Naranjillas
  • Pimentos
  • Pepinos
  • Goji berries
  • Ground cherries, also called cape gooseberries (fruit cherries are not nightshades.)
  • Garden Huckleberries (huckleberries are not nightshades)
  • Ashwagandha, an ayurvedic herb
What are Glycoalkaloids?

Glycoalkaloids are natural pesticides produced by nightshade plants. They are also present in small amounts in a few non-nightshades such as cherries, apples, and sugar beets.

Glycoalkaloids are bitter compounds which are found throughout the plant, but especially in leaves, flowers, and unripe fruits. They defend the plants against bacteria, fungi, viruses, and insects.

How do these chemicals kill pests?

Glycoalkaloids bind strongly to the cholesterol in the cell membranes of predators, disrupting the structure of their membranes, and causing their cells to leak or burst open upon contact—acting like invisible hand grenades.
Glycoalkaloids have another powerful trick up their sleeves—they also act as neurotoxins, by blocking the enzyme cholinesterase.

This enzyme is responsible for breaking down acetylcholine, a vital neurotransmitter that carries signals between nerve cells and muscle cells.

 When the enzyme is blocked, acetylcholine can accumulate and electrically overstimulate the predator’s muscle cells.

This can lead to paralysis, convulsions, respiratory arrest, and death. Military “nerve gases” work exactly the same way.

Ok, so glycoalkaloids are clearly nightmarish compounds for tiny creatures daring to storm the nightshade’s citadel, but how much do we know about their effects on human health?

Proposed glycoalkaloid health benefits

Health benefits? From a pesticide?

Glycoalkaloids are structurally similar to glucocorticoids, such as our body’s stress hormone, cortisol.

Cortisol has many roles in the body, one of which is to reduce inflammation. 

Therefore, perhaps it is not so surprising that glycoalkaloids have been shown to have anti-inflammatory properties in laboratory studies of animals.

It should also not be surprising that glycoalkaloids have been shown in laboratory studies to possess antibiotic and antiviral properties, since this is what nature designed them for.

In laboratory (in vitro) studies, glycoalkaloids can trigger cancer cells to self-destruct.

This process is called “apoptosis.” Unfortunately, they can also cause healthy non-cancerous cells to do the same thing.

Cancer studies in live animals and humans (in vivo) have not yet been conducted.

The other side of the sword:

Research has shown that glycoalkaloids can burst open the membranes of red blood cells and mitochondria (our cells’ energy generators).

Some scientists have wondered whether glycoalkaloids could be one potential cause for “leaky gut” syndromes due to their ability to poke holes in cells:

Glycoalkaloids are also known to cause birth defects in laboratory animals.

Nightshades and Nicotine

Nightshade foods also contain small amounts of nicotine, especially when unripe. Nicotine is much higher in tobacco leaves, of course.

Scientists think that nicotine is a natural plant pesticide, although it is unclear exactly how it works to protect plants from invaders.

The amount of nicotine in ripe nightshade foods ranges from 2 to 7 micrograms per kg of food.

Nicotine is heat-stable, therefore, it is found in prepared foods such as ketchup and French fries.

The health effects of these small doses is not known, but some scientists wonder whether the nicotine content of these foods is why some people describe feeling addicted to them.

Do you have nightshade sensitivity? 

As with any food sensitivity, the only way to find out is to remove nightshades from your diet for a couple of weeks or so to see if you feel better.

There are ZERO scientific articles about nightshade sensitivity, chronic pain, or arthritis in the literature, however, the internet is full of anecdotal reports of people who have found that nightshades aggravate arthritis, fibromyalgia, or other chronic pain syndromes.

Usually there's a variety of symptoms, most notably:
  • heartburn
  • difficulty concentrating
  • pounding heart
  • muscle/nerve/joint pain 
  • insomnia. 
Everyone is different, so as always, you’ll need to discover for yourself whether these foods may pose problems for your individual chemistry. 

However, given what we know about nightshade chemicals, common sense tells us that these foods are well worth exploring as potential culprits in pain syndromes, gastrointestinal syndromes, and neurologic /psychiatric symptoms. 

  • Hansen AA. Two fatal cases of potato poisoning. Science 1925; 61(1578): 340-341. 
  • Korpan YI et al. Potato glycoalkaloids: true safety or false sense of security? Trends in Biotechnology 2004; 22(3): 147-151. 
  • McMillan M and Thompson JC. An outbreak of suspected solanine poisoning in schoolboys: examinations of criteria of solanine poisoning. Q J Med 1979; 48(190): 227-243.

If you found this article helpful, share it with your family and friends.