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The pluses of
probiotics
Many doctors and nutritionists
advise patients to take probiotics to help restore
the gut's natural flora. New guidelines out of
Yale Medical School recommend them for diarrhea
in adults and kids, antibiotic-associated diarrhea
and pouchitis. Though more research is needed,
some studies also suggest probiotics can:
- manage lactose intolerance
- lower cholesterol
- lower blood pressure
- improve immune function and
prevent infections
- reduce inflammation
- prevent colon cancer
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It's widely known that probiotics
— popular dietary supplements containing gut-friendly
bacteria — help restore the natural intestinal
flora. Now it seems that they may also be protective
against intestinal diseases associated with stress,
such as irritable bowel syndrome, according to Canadian
research in the current issue of Gut.
"One thing that isn't appreciated
generally is that we have more bacterial cells in our
bodies than we do cells of human nature," said author
Dr Mary Perdue, of the Intestinal Diseases Research
Program at McMaster University. "Our entire health depends
on the positive association of our body with these bacteria."
It's already been established that
mental stress can bring physiologic changes in the intestinal
epithelium that leave it more permeable and vulnerable
to attack by pathogenic bacteria. But this latest research
has shown that ingesting a solution containing friendly
lactobacilli could confer a remarkable degree of protection.
Stressed rats that received this treatment were almost
as resistant to intestinal pathogens as rats that hadn't
been stressed at all.
STRESS
CASE
Dr Perdue's team compared four groups of rats: an unstressed
control group, an unstressed group given a commercially
available probiotic solution, an untreated stressed
group and a stressed group pre-treated with probiotics.
The unstressed rats showed little evidence of bacterial
adhesion or penetration. But the differences between
the two stressed groups are immediately visible on the
slides. In the untreated rats, pathogens can be seen
adhering to cells and forcing themselves into cells
and between them. The epithelial cells are normally
joined together to form an impermeable barrier, but
the continuity of the intestinal wall is clearly broken
in the stressed rats untreated with probiotics, and
pathogens are migrating deep into the epithelium.
The protective effect of probiotics
was measured by the number of adhering pathogens per
square millimetre of tissue: 28.3 in the stressed, untreated
rats vs 4.4 in the stressed rats given probiotics. The
difference in permeability could be seen in the number
of colony forming units cultured from mesenteric lymph
nodes: an average of 1,381 in stressed, untreated rats
compared with zero in the rats treated with probiotics.
The model used in this research
is called water avoidance stress: the rat is placed
on a platform surrounded by water for one hour a day
over a ten-day period. This technique has already been
shown to produce quite dramatic changes in the intestine:
pathogenic bacteria are far more likely to adhere to
the epithelium in such rats. They're also more likely
to penetrate it, leading to more inflammation.
Dr Perdue explained that while
it's difficult to extrapolate from that model to humans,
"it's clear that humans exposed to stressful situations
over time can develop intestinal dysfunction, and individuals
with certain GI conditions have their symptoms exacerbated
by stress. I wouldn't want to make a definite leap but
we believe that there's a connection."
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