Probiotics: Good Bacteria, Good for Gut, and Good Evidence

1. Volume 2, Issue 8, Nov/Dec 2009
Probiotics: Good Bacteria, Good for Gut, and Good Evidence
By: Charles Spielholz, Ph.D.
P
robiotics are live microorganisms that are fed to a host in order to bring about a health
benefit. In our case, the host is a person. Probiotics usually consist of yeast and/or
bacteria. The bacteria Lactobacillus (lactic acid bacteria) and Bacillus
(Bifidobacteria) are the most common genera of probiotics used in functional foods designed for
human consumption. Each of these genera comprises many different strains and not all strains
are effective in all situations. Therefore manufacturers of probiotic products must use strains that
are known to provide the benefits which are claimed.
Probiotics are generally active in the
digestive system and are administered orally
as a constituent of a functional food, such as
fermented milk or yogurt, or in capsule or
powder forms. Some companies are
working on adding probiotics to fruits such
as apples (which would offer users a non-
dairy functional food source) as well as to fun-to-eat foods like pizza and pasta. In cases where
probiotics are used to help alleviate skin conditions, the probiotics are administered topically.
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2. Volume 2, Issue 8, Nov/Dec 2009
Regardless of how probiotics are delivered to the host’s digestive tract, it is critical that
the probiotic species be stable and remains alive while it is in storage in the functional food,
capsule or powder or whatever method is used as a delivery vehicle. It is equally critical that the
probiotic species be able to survive long enough in the host’s digestive tract to have the intended
beneficial effect. It is equally critical that the specific strain used have the beneficial effect
desired and to not cause infections or any kind of pathogenicity.
At this point, it is useful to define the term prebiotic. Prebiotics are best described as
roughage or fiber. Fiber is food material that is not digestible by the host. Usually derived from
plants, prebiotics are generally oligosaccharides or carbohydrates that can serve to support and
stimulate the growth and/or activity of probiotics in the human digestive tract. Prebiotics will
not be discussed in this mini-review.
The digestive tract is the major beneficiary of probiotics. Probiotics appear to help
control the population of pathogenic microorganisms in the digestive tract by outgrowing, out
adhering or otherwise inhibiting the growth of pathogenic microorganisms. Benefits to the
digestive tract include control of stomach upset, diarrhea and constipation. Probiotics may also
be a good way to replace microorganisms to the digestive during or after treatment with
antibiotics. Evidence also indicates that probiotics may help control candidiasis and urinary tract
infections, again by out populating problematic or pathogenic microorganisms. Finally, there are
also claims that probiotics may lower cholesterol, alleviate rheumatoid arthritis, atopic dermatitis
and Crohn’s disease, exert anti-cancer activity and modulate the immune system. Each of these
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3. Volume 2, Issue 8, Nov/Dec 2009
proposals and claims will be briefly examined in this mini-review. In addition, the safety and
adverse effects profile will be briefly evaluated. Finally, recent concerns regarding probiotic
claims will be reviewed using an example involving yogurt.
Probiotics have shown benefit with the control of diarrhea caused by antibiotics and some
infections. A small number of basic, randomized clinical trials have shown that the
administration of probiotics with standard rehydration therapy decreases the duration of acute
diarrhea (1-6). However, not all cases of infectious diarrhea can be alleviated by the use
probiotics. For example there is no significant evidence that diarrhea resulting from infection by
Clostridium difficile is alleviated by probiotics (7-8).
Clinical trials with traveler’s diarrhea have been mixed (9-11) probably reflecting the
large variety of microorganisms that cause traveler’s diarrhea as well as the variety of probiotic
strains used to treat it.
Antibiotic treatment of infectious diseases is known to cause diarrhea in many patients.
Several studies have shown that taking probiotics with antibiotics decreases the chances of
antibiotic associated diarrhea by about 10 to 50% (6, 12-14). Again the range of efficacy is
probably due to different strains of probiotics used in different clinical trials as well as
differences in the microorganism types found in the digestive tracts of different groups of people.
Data regarding stomach upset and the resulting symptoms show that probiotics delivered
orally in functional foods (or as capsules or powders) are helpful for alleviating some, but not all,
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4. Volume 2, Issue 8, Nov/Dec 2009
causes of stomach upset. As with any health situation, if the condition does not clear up, then the
individual should see their health care provider. In the case of stomach upset, this means no more
than two days.
A role for probiotics in the treatment of inflammatory bowel diseases and related
conditions has also been proposed and tested in a preliminary manner. Thus far results have
been mixed (15-22). Clinical trials using probiotics to treat Crohn’s disease have been
inconsistent and indicate the need for well controlled clinical trials. Data from clinical trials with
ulcerative colitis is more consistent; it appears that probiotics may prevent relapse and may also
be useful to treat mild to moderate attacks and symptoms of ulcerative colitis. Evidence also
exists showing that probiotics can also help manage pouchitis and diverticulitis. However, as
with Crohn’s disease, more research is needed to define exactly which conditions can be treated
and exactly which strains of bacteria should be used.
Probiotics may also function outside the digestive tract. Preliminary evidence is very
promising; data indicates that probiotics may be useful in preventing urinary tract infections and
bacterial vaginosis in women (23-25). In these cases, the probiotics were applied topically, not
orally. Again, additional clinical trials are needed before a precise role for probiotics in the
treatment or prevention of urinary tract infections can be developed.
Probiotics have also been proposed as a treatment for a large variety of other ailments,
conditions and diseases including colon cancer, lowering cholesterol and blood pressure, aiding
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5. Volume 2, Issue 8, Nov/Dec 2009
relief from lactose intolerance, improving immune function, treating ulcers caused by
Helicobacter pylori, relieving rheumatoid arthritis, allergy, and atopic dermatitis. However,
research into these areas is in the very early stages; rigorous clinical trials are required before any
conclusions can be made regarding a role for probiotics in the treatment of any of these
conditions, ailments or diseases. In many of these situations, probiotics may be altering immune
responses (possibly activating or redirecting the response) or by crowding out pathogenic
species. Additional research will tell.
Probiotics are generally considered to be safe. Reports of adverse reactions with
common probiotics are rare. The species most often used in probiotic formulations,
bactobacillus and Bacillus, are normally found in the digestive tract of humans. In some cases,
when candidate probiotics are isolated from infections, special precautions must be taken to
ensure that such species are safe to use as a probiotic (26). However, for some unique
conditions, well known probiotics that have been considered safe have caused sepsis. For
example, neonates treated for necrotizing enterocolitis with probiotics developed sepsis (27-28).
Observations of this sort define the requirement for well performed clinical studies before certain
treatments with probiotics are attempted. Indeed, probiotics are safe with very few reports of
adverse reactions. However, as with any agent, probiotics should not be used in people with
severe illness or who are immune compromised.
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6. Volume 2, Issue 8, Nov/Dec 2009
Although there is ample volume of evidence that shows probiotics are useful for digestive
health and for the immune system, producers still must be very careful about the wording of
statements regarding health claims. Dannon recently settled a class action lawsuit regarding
claims about its probiotic products, Activia yogurt and DanActive yogurt drinks (29). Dannon
claimed that these products could help regulate
digestion and stimulate an immune response. As
part of the settlement, Dannon agreed to change
wording on its probiotic products to better reflect
that Avtivia yogurt and DanActive yogurt drinks
are not cures or treatments for any medical
disorder and that if a consumer has concerns about
their digestive tract, they should consult with a
health care provider. The reason Dannon settled this class action lawsuit was to avoid further
litigation. However, Dannon continues to stand by its health claims that Activia and DanActive
products are scientifically proven to help regulate the digestive tract when used as part of a
balanced diet and a healthy life style. Dannon, which is a company that produces products of
excellent quality and performs excellent research to support claims regarding its products, plans
to present additional research that will support health claims regarding its probiotic products.
Probiotics are an exciting area of the functional food industry. Probiotics have already
provided important contributions to maintaining health of the digestive tract without adverse
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7. Volume 2, Issue 8, Nov/Dec 2009
effects. Further research is expected to prove that there are additional health benefits to
probiotics. Probiotics are an excellent example of how research, both scientific and clinical, is
able to be used to prove the benefits of a functional food.
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