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Georgia Ede MD
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How Deadly Are Nightshades?
Nightshades have a reputation as bad
actors 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?
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Meet the Nightshade (Solanaceae) Family:
Tomatoes
Eggplant
Potatoes
e-mail
Goji Berries
Tobacco
First name
Peppers (bell peppers, chili peppers, paprika, tamales, tomatillos, pimentos,
cayenne, etc)
Last name
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. Of the foods above, 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.
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.
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What are glycoalkaloids?
Glycoalkaloids are natural pesticides produced by nightshade plants. [They are also
present in small amounts in a few non-nightshades: 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?
Crucifers Dairy
diabetes Dopamine
Epilepsy Ferritin
Food Sensitivity
Fructose Fruits Gluten Heart
Disease Hypertension IGF-I
insulin iron
diet
ketogenic
Legumes low-carbohydrate diet
Meat nitrites Nuts obesity Omega-3
Omega-6 PAH red meat
Refined
Carbohydrates Restless Legs RLS
Glycoalkaloids bind strongly to the cholesterol in the cell membranes of predators,
saturated fat Seizures Vegan Vegetables
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? Hmmm…
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 noncancerous cells to do the same thing. Cancer studies in live animals and humans (in
vivo) have not yet been conducted.
“…the undifferentiating destruction of both cancer and noncancerous cell lines…
leads to questions of therapeutic uses of glycoalkaloids due to safety
considerations. However, it is difficult to translate the results of an in vivo trial in
vitro. Therefore, both animal and human experiments are essential to confirm or
disprove the in vivo data observed in these studies.” [Milner 2011].
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, normally available while eating potatoes, embed themselves
and disrupt epithelial barrier integrity in a dose-dependent fashion in both cell
culture models and in sheets of mammalian intestine…animals with the genetic
predisposition to develop IBD, demonstrated a greater degree of small intestinal
epithelial barrier disruption and inflammation when their epithelium was
exposed to the potato glycoalkaloids chaconine and solanine.”
Glycoalkaloids are also known to cause birth defects in laboratory animals.
Fruits vs vegetables: here we go again!
Those of you who are familiar with my philosophy about plant foods know that I
believe vegetables are far less trustworthy when it comes to health effects than
edible fruits, and nightshades make this point nicely. The only nightshade vegetable
Weight Loss whey
humans eat is the potato; the rest of the nightshades (other than tobacco, which is
smoked, not eaten) are fruits, because they contain seeds—eggplant, tomatoes, goji
and peppers. As you will see below, even though fruits contain glycoalkaloids, they
are far less likely to harm us. [To watch my Ancestral Health Symposium video
about vegetables vs. fruits, click HERE
HERE.]
.]
Potato glycoalkaloids
Nightshade potatoes include all potatoes except for sweet potatoes and yams.
Potatoes make two glycoalkaloids: alpha-chaconine and alpha-solanine. These are
the most toxic glycoalkaloids found in the edible nightshade family. Alpha-chaconine
is actually more potent than alpha-solanine, but solanine has been studied much
more thoroughly, and is therefore more familiar.
Most of us do not associate potatoes with illness, probably because the amount of
glycoalkaloid most of us eat every day is not very high. There are numerous cases of
livestock deaths from eating raw potatoes, potato berries, and potato leaves, but
people do not eat these things. However, there are well-documented reports of
people getting glycoalkaloid poisoning from potatoes, typically from eating
improperly stored, green, or sprouting potatoes. At low doses, humans can
experience gastrointestinal symptoms, such as vomiting and diarrhea. At higher
doses, much more serious symptoms can occur, including fever, low blood pressure,
confusion, and other neurological problems. At very high doses, glycoalkaloids are
fatal.
Another reason why many people may not be bothered by potatoes is that
glycoalkaloids are very poorly absorbed by the gastrointestinal tract, so, if you have a
healthy digestive tract, most of the glycoalkaloid won’t make it into your
bloodstream. However, if you eat potatoes every day, levels can build up over time
and accumulate in the body’s tissues and organs, because it takes many days for
them to be cleared. Also, since glycoalkaloids have the ability to burst cells open,
they can theoretically cause damage to the cells that line your digestive system as
they are passing through (this has been proven in animal studies but there are no
human studies, to my knowledge).
Due to known toxicity, the FDA limits the glycoalkaloid content in potatoes to a
maximum of 200 mg/kg potatoes (91 mg per pound). Human studies show that
doses as low as 1 mg glycoalkaloid per kg body weight can be toxic, and that doses as
low as 3 mg/kg can be fatal. This means that, if you weigh 150 lbs, then doses as low
as 68 mg could be toxic, and doses as low as 202 mg could be fatal.
Potato processing 101
The vast majority of glycoalkaloid is in the potato skin, so peeling will remove virtually
all of it. Glycoalkaloid levels can be dangerously high in unripe and sprouting
potatoes; any greenish areas or “eyes” should be removed or avoided.
Glycoalkaloids survive most types of cooking and processing. In fact, deep frying will
increase levels if the oil isn’t changed frequently, so fried products such as potato
skins and french fries can contain relatively high amounts:
“Mechanical damage to potato tissue increases the concentration of
glycoalkaloids available for consumption. In addition, frying potatoes at high
temperatures does not inactivate but instead serves to preserve and concentrate
glycoalkaloids within the potato, leaving them available for ingestion and delivery
to the intestine…” [Patel 2002]
Boiling—reduces glycoalkaloids by a few percentage points
Microwaving—reduces glycoalkaloids by 15%
Deep frying at 150C (300F)—no effect (McDonald’s uses 340F degree oil)
Deep frying at 210C (410F)—reduces glycoalkaloid content by 40%
Glycoalkaloid levels of a few prepared potato products are available [Milner 2006]:
Potato chips, 1 oz bag: 0.36 to 0.88 mg chaconine and 0.29 to 1.4 mg solanine.
Total glycoalkaloid concentration ranges from 2.7 to 12.4 mg per bag.
Fried potato skins, 4 oz: 4.4 to 13.6 mg chaconine and 2.0 to 9.5 mg solanine.
Total glycoalkaloid concentration ranges from 6.4 to 23.1 mg per 4 oz serving.
Tomato glycoalkaloids
Tomato nightshades include all types of tomatoes: cherry tomatoes, green
tomatoes, yellow tomatoes and ripe red tomatoes.
Tomatoes produce two glycoalkaloids: alpha-tomatine and dehydrotomatine. The
majority is in the form of alpha-tomatine, so we’ll focus on that one here.
As tomatoes ripen, alpha-tomatine levels drop dramatically, from about 500 mg/kg in
green tomatoes to about 5 mg/kg in ripe red tomatoes, or 2.3 mg/lb. [For those of
you keeping score at home—that’s Fruits: 1, Veggies: 0.] Artificially ripened fruits may
contain higher amounts than sun-ripened fruits.
Tomato glycoalkaloids are about 20 times less toxic than potato glycoalkaloids.
(Fruits: 2, Veggies: 0). There are no dosage studies of tomatine in humans, but
studies in mice tell us that 500 mg tomatine per 1 kg body weight (or 227 mg per
pound) is the median lethal dose (“LD50”). This doesn’t tell us how much it would
take to kill a 150 lb person; all we know is that it would take 34 grams of tomatine to
kill a 150 pound mouse. Since ripe tomatoes contain 5 mg/kg or 2.3 mg/lb of
tomatine, it would take nearly 15,000 pounds of tomatoes to kill this Mighty Mouse
(probably many fewer pounds if you were to simply hurl them in his general direction
from across the room). Since green tomatoes contain 100 times more tomatine, it
would only take 150 pounds of green tomatoes to kill the overgrown rodent. We do
not understand the effect of low doses of tomatine on any type of animal, including
humans, over time.
Eggplant
Centuries ago, the common eggplant was referred to as “mad apple” due to belief
that eating it regularly would cause mental illness. Eggplants produce two
glycoalkaloids: alpha-solamargine and alpha-solasonine. Solamargine is more
potent than solasonine.
Whereas potato glycoalkaloids are located mainly in the skin, in eggplants,
glycoalkaloids are found primarily within the seeds and flesh; the peel contains
negligible amounts.
The common eggplant (solanum melongena) contains 10-20 mg of glycoalkaloid per
kg (or 4.5 to 9 mg per pound of eggplant). Eggplant glycoalkaloids are considered
relatively nontoxic compared to potato glycoalkaloids (Fruits: 3, Veggies: 0).
The median lethal dose (LD50) in rodents is 1.75 mg/kg. This means that it would
take at least 13 pounds of eggplant to kill a 150 lb monster mouse. [Note to self—
when facing a giant rodent in a dark alley, go for the eggplants, not the tomatoes].
What about peppers and goji berries?
Your guess is as good as mine…I could not locate any scientific information about
glycoalkaloids in these foods. Peppers, because they are fruits and because they are
in a different subfamily than the rest of the nightshade foods, may contain much less
glycoalkaloid? Or none at all? Peppers are famous for containing hot and spicy
“capsaicinoids”, not glycoalkaloids (I’ll write about peppers and capsaicinoids in a
future article).
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. I personally am very sensitive to nightshades; they cause me a variety of
symptoms, most notably heartburn, difficulty concentrating, pounding heart,
muscle/nerve/joint pain, and profound 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.
18
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Tagged with: Arthritis • Eggplant • Fibromyalgia • Glycoalkaloid • Goji berries • Nicotine •
Nightshades • Peppers • Potatoes • Tomatoes
Coming soon to the Food and Health Blog:
Ketogenic Diets for Weight Loss and Health
Health—a review of The Art and Science of
Low Carbohydrate Living by Dr.s Phinney and Volek.
The role of diet in eating disorders
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REFERENCES
http://www.accessdata.fda.gov/scripts/Plantox/Detail.CFM?ID=6537
Friedman M. Tomato glycoalkaloids: role in the plant and in the diet. J Agric Food
Chem2002; 50:5751-5780. UDSA, Albany California.
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.
Mensinga TT et al. Potato glycoalkaloids and adverse effects in humans: an
ascending dose study. Regulatory Toxicology and Pharmacology 2005;41: 66-72.
University of Utrecht, The Netherlands.
Milner SE et al. Bioactivities of glycoalkaloids and their aglycones from Solanum
species. J Agric Food Chem 2011; 59: 3454–3484. University College, Cork Ireland.
Patel B et al. Potato glycoalkaloids adversely affect intestinal permeability and
aggravate inflammatory bowel disease. Inflammatory Bowel Diseases 2002; 8 (5):
340-346.
Sanchez-Mata MC et al. r-Solasonine and r-Solamargine Contents of Gboma
(Solanum macrocarpon L.) and Scarlet (Solanum aethiopicum L.) Eggplants J Agric
Food Chem 2010; 58: 5502–5508.
Siegmund B et al. Determination of the nicotine content of various edible
nightshades (Solanaceae) and their products and estimation of the associated dietary
nicotine intake. J Agric Food Chem 1999;47: 3113−3120.
18 Comments
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bob
•
5 months ago
is mairajana a nightshade like tobacco
2
• Reply • Share ›
Dr. Ede
Mod
bob • 5 months ago
Hi bob
No, marijuana does not belong to the nightshade family.
1
Vanessa
• Reply • Share ›
•
6 months ago
Interesting read. Through a very long and frustrating process we realised nightshade
is the cause of my daughters severe eczema. We have removed it from her diet and
within 2 weeks she just had dry skin and within a month it was completely gone. I also
realised it was the cause of many years of stomach cramps.
2
• Reply • Share ›
Caroline
Vanessa • 5 months ago
I too ended 23 years of living with often severe psoriasis by cutting out night
shades and following additional nutritional advice tested and published by Dr
John Pagano in his book Healing Psoriasis: The Natural Alternative.
2
Dr. Ede
• Reply • Share ›
Mod
Vanessa • 5 months ago
Hi Vanessa
That's wonderful--congratulations for figuring it out and telling us about it!
• Reply • Share ›
Eileen @ Phoenix Helix
•
a year ago
It's interesting that you make the statement that the vegetable nightshade is more
likely to harm us than the fruit ones, when most people I know tolerate potatoes far
better than any other nightshade. Some react strongest to tomatoes, others to
eggplant and I react really strongly to pepper spices, which you say don't have
glycoalkaloids. Whatever capsacain is, it does a number of me! (Rheumatoid Arthritis)
2
• Reply • Share ›
Dr. Ede
Eileen @ Phoenix Helix • a year ago
Mod
Right you are, Eileen--just because the research tells us that potato (skins)
contain the highest amounts of the most potent glycoalkaloids does not mean
that we can't as individuals have our own unique reactions to nightshades. I
personally am unable to tolerate all nightshades, with the peppers and
eggplant being the worst for me and potato being the least bothersome. I
never tried eating a pile of potato skins, though (the flesh of the potato doesn't
have any glycoalkaloids in it, which may be why most tolerate them so well).
There are also likely numerous other naturally occurring chemicals in these
plants that bother some of us and are simply not investigated by scientists. As
you have already discovered, the best way to know whether or not a food
bothers you is to listen to your body and believe what it is telling you:) I will
write about the capsaicinoids in peppers in a future blog post.
• Reply • Share ›
Steve Parker, M.D.
•
2 years ago
I appreciate this summary, Dr. Ede. I reviewed potential potato toxicity recently when I
was deciding whether to include them in my personal version of the paleo diet (they're
included). I attempt to keep up with the internal medicine and medical nutrition
literature, and, like you, I don't see a lot on nightshade toxicity.
2
• Reply • Share ›
Dr. Ede
Mod
Steve Parker, M.D. • 2 years ago
Hi Dr. Parker, and thanks so much for reading and commenting on this article-for those of you who haven't visited Dr. Parker's blog, it is at
http://paleodiabetic.com/ and contains lots of excellent information about
Paleo diets. He pays special attention to the application of Paleo diets to the
treatment of diabetes.
ge
• Reply • Share ›
Paleobird
•
2 years ago
Very interesting article, Dr. Ede.
You mentioned the association between nightshades and neurological issues in
general. I was wondering if you knew of any research specific to epilepsy, (something
I am very interested in because I have it).
1
• Reply • Share ›
JaylyandJennifer Jackson
Paleobird • 6 months ago
Hello,
Very interesting comment. I ate eggplant for the first time a week ago, and
suffered from a seizure overnight/early the next morning (awakened from
sleep). I believe it was the eggplant that caused the seizure.
Jennifer
2
Dr. Ede
• Reply • Share ›
Mod
Paleobird • 2 years ago
Hi Paleobird,
Interesting question...as is the case with so many food-health questions, I am
not aware of any scientific information available about the possible connection
between epilepsy and nightshades. However, given the fact that glycoalkaloids
are toxic to cells in general, and nerve cells in particular, it would make sense
that nightshades could be a culprit. The only way to know if nightshades are a
factor in your seizures is to remove them from your diet for a while to see if
you feel any better. With seizures it may be more challenging to notice,
particularly if you are taking an anticonvulsant medication. If you are taking
medication, and you decide you want to do a nightshade-free trial, you would
want to have your neurologist monitor your progress with you.
It can be challenging to remove nightshades, since potato starch is in many
processed foods, and peppers/pepper extracts are in almost all savory
prepared foods these days, in the form of chili flakes, cayenne, or paprika, and
are often not even listed as an ingredient other than "spices."
The only dietary intervention I'm aware of for epilepsy that has scientific
research behind it is the ketogenic diet (see bipolar/low-carb post).
ge
• Reply • Share ›
Al
a month ago
•
Thanks for this article. I have been suffering from neuralgia for a number of years and
spent a good few months without nightshades. I have just reintroduced them for one
week and have seen certain aspects of the pain shoot up again. If I do suffer from
nightshade intolerance, how long does the system need to eliminate them? Is there
anything one can do to speed up the process?
Have you ever heard of a link between nerve pain and the nightshade family? My pain
doc wants me to see a micronutritionist, but I'm sure myself.
Thanks again,
Al
• Reply • Share ›
BM
•
a month ago
I was diagnosed with osteoarthritis in my spine 5-6 years ago. Especially painful in the
morning. I was so depressed trying to cope with this disease. On May 17 I read an
article about nightshades and decided I would omit them from my diet for 3 months
to see if it would help me. In 3 weeks 85-90% of the pain was gone! It's been only 2
months and I'm still afraid that I will wake up and find it was only a dream.
• Reply • Share ›
Bobby Stranger
•
3 months ago
I find tomatoes give me a nasty headache afterwards, Also, potatoes (esp. mashed),
causes major issues with excess stomach acid/heartburn! Rum old stuff, eh?!
• Reply • Share ›
Christy
•
4 months ago
Very interesting! This is a great article--thank you! Have you happened to look up any
more on the peppers? I am doing an elimination diet and closing in on the culprit of
some restless leg and fidgety symptoms. Nightshades for sure (or pesticides found on
them--I will know more if I can isolate it down to organics only)--and I think perhaps
peppers specifically--which makes me sad because I love spicy food.
• Reply • Share ›
pone
•
7 months ago
How are the toxins being removed from potato starch? Are you aware that there is
now a health craze going on in the Paleo diet community to mix up to four
tablespoons of raw potato starch in water each night and swallow it raw with no
cooking? I wonder what kind of toxin levels that would expose people to, and is there
any preparation that would remove the toxin?
• Reply • Share ›
Dr. Ede
Mod
pone • 5 months ago
Hi pone
Interesting...I was not aware of this interesting trend, but luckily the vast
majority of potential toxins are in the skin of the potato rather than in the flesh,
from which the starch is made.
• Reply • Share ›
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Copyright Georgia Ede MD 2012. A Shelton Interactive site.