[presented for your perusal without necessarily agreeing or disagreeing, simply
because it seems to be the only article on Nightshades not based on hearsay]

Any Way You Slice Them, Nightshade Allergies Unlikely

Nov 14 2000 14:01:50
Holly VanScoy, Ph.D.
drkoop.com Health Correspondent

In health folklore, edible vegetables in the nightshade family -- which
includes potatoes, tomatoes, eggplant and most peppers -- are often linked to
numerous allergic disorders.
Although there is no scientific evidence to substantiate their role as common
allergy-provoking agents, it's easy to discover the origin of their shady
reputations.

Something About Nightshade
According to William R. Belknap, Ph.D., of the United States Department of
Agriculture Western Regional Research Center in Albany, Calif., who is
currently conducting in-depth studies to improve potatoes, all nightshade
plants are members of the botanical family Solanaceae. Furthermore, he adds,
all of them produce glycoalkaloids -- chemicals that in large quantities can be
toxic.

Materials from the USDA report that the specific glycoalkaloid in potatoes,
peppers and eggplant is solanine; the glycoalkaloid in tomatoes is tomatine.

As Dan Brown, Ph.D., associate professor of nutritional toxicology at the
Animal Science Department at Cornell University in New York, notes, such
chemicals are apparently useful to the plants, probably helping the growing
vegetables resist insects such as the potato beetle, leafhopper and wireworm.

That's great news for the tomato and potato, but not so good for baked potato
lovers.

As Brown and his nutritional toxicology students have discovered in their
studies of nightshade vegetables, humans and all classes of livestock are
susceptible to being affected by the glycoalkaloids they contain.

"Some individuals may be more susceptible than others," Brown explained. That's
the bad news.

The good news, according to Brown, is the risk of becoming seriously ill from
eating potatoes, tomatoes, eggplant or peppers is relatively small, because of
the following:

Standards are now in place in the United States and many other parts of the
world to test all commercially grown potato varieties for solanine. To be
approved by the USDA, for example, potatoes must contain less than 20
milligrams of solanine for each 100 grams of weight. Most commercial potatoes
now on the market in the United States have between 2 milligrams and 13
milligrams per 100 grams of weight. None have more than 19 milligrams.

The solanine in potatoes is found almost exclusively in their skin and sprouts
(or "eyes"); tomatine is found only in the tomato plant's stem and, early in
their development, in unripe, green tomatoes. Green color in both tomatoes and
potatoes is a clue that their toxin levels may be dangerously high, although
the color comes from an entirely different and harmless process of making
chlorophyll. Avoiding green parts effectively reduces the threat of toxicity.

Fortunately all glycoalkaloids are poorly absorbed in the stomach and
intestines of mammals -- including humans -- so, even if significant amounts
are eaten, the body can usually process the toxins without severe adverse
effects.

During digestion, human beings convert much of the poison in glycoalkaloids to
less toxic chemicals, which also reduces the severity of any symptoms that
might occur.

The body rapidly excretes the substances through urine and feces, so any
intestinal discomfort these toxins cause is usually fleeting.

Brown acknowledges that even minor intestinal symptoms -- such as cramping and
diarrhea -- can be very unpleasant, but, he added, "The main point with
sub-lethal toxins like these is that humans can tolerate a certain amount of
them and have many body mechanisms to protect ourselves from them."

"Eating less toxic animal products, developing cooking and processing food were
developed by our ancestors to get around these problems," Brown said. "We
depend on cooking to destroy some toxins and eating a variety of foods to
reduce our dosage of any one harmful compound."

If I Have a Reaction, Aren't I Allergic?
In most cases, the short answer is: No.

"Most human reactions to nightshade vegetables are not allergic reactions,"
Belknap said. "They are typically toxic reactions, which are entirely
different."

On the Cornell University Food Science Web site, results of nutritional
toxicology research efforts Brown supervised show that when large amounts of
nightshade vegetables with significant levels of toxins are eaten, the
resulting illness is usually solanine or tomatine poisoning, which more often
affects groups of people rather than individuals.

Early last century, before potato solanine levels were routinely regulated,
there were at least two documented outbreaks of potato poisoning in Europe.
Since solanine levels are routinely tested and severely limited by law now,
these outbreaks are extremely rare, as an article by medical staff at the
Posiondex System, a poison control center in Lakewood, Colo., in the August
1994 issue of Veterinary and Human Toxicology confirmed. The article's writers
note that the potato is now one of the world's most important food sources,
with newer varieties now being safer for human consumption than earlier ones.

What about an individual who feels sick after eating a typical serving of a
nightshade vegetable? Allergic, right?

Not usually.

Most such adverse reactions are best described as a "food intolerance" or "food
idiosyncrasy" -- not food allergy, according to the International Food
Information Council Foundation (IFICF) in Washington, D.C., which provides a
useful definition of these terms on its Web site:

Food intolerance is an adverse reaction to a food substance that involves
digestion or metabolism, but does not involve the immune system.

Food idiosyncrasy is an abnormal response to a food or food substance. The
reaction can resemble or differ from symptoms of a true food allergy, but it
does not involve the immune system.

According to Anne Munoz-Furlong at the national Food Allergy Network (FAN),
although it is not impossible to have a true allergic reaction to any food --
including nightshade vegetables, only a specially trained physician can
determine whether the immune system is involved and correctly diagnosis a
nightshade vegetable allergy.
Intolerance, Idiosyncrasy, Allergy ... Is It Goodbye to Fries? The experts at
ICICF recommend that people who have an adverse reaction to any food consult a
board-certified allergist to get an accurate diagnosis and develop an
appropriate food plan. The consensus of all sources is that making independent
decisions about what foods to avoid is usually not wise. So-called elimination
diets conducted without medical supervision are rarely recommended and have
never been scientifically proven to help.

Allergists and dietitians can assist individuals who have food-related health
issues meet their dietary needs, usually with little sacrifice to their
nutritional status or reduction in the pleasure they derive from eating the
foods they love.

On the other hand, FAN notes, if an allergist diagnoses an individual as having
a true allergic response to any food -- nightshade vegetables included -- this
food must be completely avoided.

Holly VanScoy, Ph.D., is an experienced medical writer, researcher and
statistician with experience in academia, as well as the public and private
sectors. She presently writes on such diverse topics as child development,
mental health, arthritis and other immune system disorders from her office in
Austin, Texas.

--
Cheers,

Ken
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