Lectin In Undercooked Red Beans Causes Food Poisoning

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http://www.medicalnewstoday.com/articles/78478.php

 

 

How Lectin In Undercooked Red Beans And Rice Causes Food Poisoning

 

Medical News Today

04 Aug 2007

 

People cry foul when fowl is undercooked, but what about red

beans and rice?

 

Scientists have discovered how lectins, a family of proteins

believed to be a natural insecticide that is abundant in

undercooked legumes and grains, can make you feel temporarily

miserable.

 

" It's known that it can be a toxin, " Dr. Paul L. McNeil,

cell biologist at the Medical College of Georgia, says of

the lectin protein that's commonly found in vegetables.

Lectins, which bind strongly to carbohydrates that decorate

cell surfaces, have a particular affinity for the

heavy-carbohydrate coats of epithelial cells that line the

gastrointestinal tract.

 

Researchers have long known that ingesting too much

undercooked lectin can cause nausea, diarrhea and vomiting.

What they didn't know was how lectin caused food poisoning.

 

Work published in PloS One shows lectins disable GI tract

cells, which are constantly bombarded while digesting food,

from repairing tears in cells walls from all the activity.

Repair normally occurs in seconds: internal membranes move up

to patch the tear, the cell recovers and the one-cell layer

lining of the GI tract remains intact.

 

" If those individual cells cannot repair tears, they die, "

says Dr. McNeil. " That means you have gaps in the integrity of

the surface area of the epithelium and you are exposing the

nasty internal world of your GI tract to your blood supply. "

 

The epithelial lining is a continuous, natural barrier between

digesting food in the GI tract and the blood supply. When

intact, it allows only good stuff like nutrients to pass

through.

 

" Your body senses that lack of barrier function and tells you

to eliminate the entire contents of the GI tract, " says Dr.

McNeil, noting that lectin's apparent role as a natural

insecticide and as a source of food poisoning are related. " If

you get vomiting and diarrhea you are going to eliminate the

entire contents of your gastrointestinal tract, right? And,

you are not going to eat red beans again the next day, right?

That is probably the point if they are natural insecticides.

Alcohol will do the same thing. When you drink too much

alcohol, you can destroy the lining of your stomach. "

 

But the scientist who first identified how injured cells patch

themselves says lectin blocks this repair mechanism better

than anything else he's seen. Interestingly, he and his

colleagues showed in PloS Biology in 2006 how roughage --

which includes beans -- help people stay 'regular' by causing

more cell tears, which enables more mucus to escape from

cells, essentially greasing the GI tract.

 

That same research team, which includes Dr. Katsuya Miyake,

MCG cell biologist, and Dr. Toru Tanaka, pharmacologist at

Josai University in Japan, has now shown lectin is also very

good at blocking mucus expulsion from cells.

 

In fact, they discovered lectin's role in stopping

cell-patching and mucus release while researching roughage.

The multipurpose lectin is a powerful stain the team used to

look at mucus released by cells after tearing. They found if

they used too much lectin there was no patching or mucus, just

cell death.

 

" Biologically it's interesting because it might tell us more

about the mechanism of repair, " says Dr. McNeil, who wants to

learn more about how lectin interferes with repair. " We know

the mechanism involves surface binding because you can add

lectin and the cells can't repair. You take the same culture

of cells, wash the lectin away, injure other cells in the

culture and they repair fine. We also know it's a very rapid,

surface-initiated inhibition. "

 

In addition to the immediate discomfort undercooked beans and

rice can cause, long term concerns ingestion of lectin has

also been linked to colorectal cancer and celiac disease, a

common problem in which individuals are sensitive to gluten, a

mixture of proteins derived from wheat flour that includes

lectins. The small intestine of the celiac sufferer is unable

to properly absorb nutrients after gluten ingestion.

 

Oddly, in a laboratory dish, safe from mechanical stresses

that cause surface tears, lectin can make cells divide, " which

is quite the opposite of making cells sick, " Dr. McNeil says.

A recent Science paper implicated lectin in diabetes as well.

 

" It's possible that this bioactive property of lectin that

binds to our cells could have long-term consequences taken

even in small amounts, " he says, noting that thorough cooking

destroys most but not all lectin. " Maybe the bloating and gas

is telling us something about lectin when it's just a minor

irritation. "

 

He notes lectin is easily among the top-10 causes of food

poisoning but is unlikely to be lethal because the body is so

good at sensing the break in the GI barrier and eliminating

the problem.

 

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Article adapted by Medical News Today from original press release.

 

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The research was funded by NASA. For more information visit

www.plosone.org/doi/pone.000687

 

 

Source: Toni Baker

 

Medical College of Georgia (http://www.mcg.edu/)

 

 

© 2007 MediLexicon International Ltd

 

 

 

 

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