Probiotic bacteria such as lactic acid bacteria and bifidobacteria
are now being introduced into many fermented food products and supplements.
The consumption of fermented dairy products containing probiotics has increased
in the past decades. There are several trillion friendly bacteria (comprising
over 400 species) in the human gastrointestinal tract.
L. Acidophilus is probably the most well known of these.
When the intestines are healthy, there are more friendly bacteria than "unfriendly"
or pathogenic (disease-causing) ones. But given the modern lifestyle of chronic
stress, poor diet, illness, use of prescription drugs and antibiotics, for many
people this balance has shifted unfavourably, creating an unhealthy condition
called "intestinal dysbiosis" which in turn can become the seedbed for many
Babies are born axenic (sterile), and the colonisation
of the digestive tract by population of microorganisms specific to each person
is done in the first few days of life. The most significant changes in the intestinal
flora take place from birth until weaning and again in the later stages of life.
In between, the microbial population of the dominant flora remains relatively
stable and prevent potentially pathogenic bacteria from adhering to the intestinal
wall. This has been termed 'the barrier effect'. However, the balance of bacteria
in the digestive tract remains fragile and susceptible to lifestyle changes.
Factors such as stress, change in diet and drug intake
(antibiotics), can disturb this balance. Any imbalance can result in various
disorders including bloating, intestinal pains, nutritional deficiencies and
constipation. Also, a disruption of the barrier effect will lead to a colonisation
of the digestive system by pathogenic bacteria which may result in intestinal
These disorders can be very severe, such as in the case
of pseudomembraneous colitis (a serious type of diarrhoea) induced by the pathogenic
bacteria Clostridium difficile due to the elimination of the barrier effect
following a course of antibiotics. One of the most important characteristics
for a probiotic bacterium is the ability to inhibit the growth of pathogens.
One such method is the production of organic compounds
such as lactic acid, hydrogen peroxide and acetic acid. The synthesis and secretion
of such acidic compounds helps to reduce the pH of the intestinal environment
and produce conditions in which pathogenic bacteria cannot thrive. Probiotics
can also produce natural antibiotics called bacteriocins, which directly help
to kill unwanted bacteria. Another method, as mentioned above, is called 'the
This is simply the production of a wall of friendly bacteria
that prevents any bad bacteria from reaching the intestinal wall. (For bad bacteria
to exert their unwanted effects, they must adhere to the intestinal wall).
Numerous scientific studies have investigated the use
of probiotic organisms as live supplements, with particular emphasis on Lactobacillus
acidophilus. Lactobacillus acidophilus has been reported to be a beneficial
probiotic organism that provides excellent therapeutic benefits. The biological
activity of probiotic bacteria is due in part to their ability to attach to
cells of the intestinal wall and therefore inhibit the attachment of pathogenic
L.acidophilus also has the ability of producing lactic
acid causing an uninhabitable environment for bad bacteria. Production of butyric
acid by some probiotic bacteria affects the turnover of intestinal cells and
neutralizes the activity of dietary carcinogens. By selecting better functional
probiotic strains and adopting improved methods to enhance survival, including
the use of appropriate prebiotics and the optimal combination of probiotics
and prebiotics (synbiotics), an increased delivery of viable bacteria in fermented
products to the consumers can be achieved.
Lactobacillus acidophilus and Lactobacillus rhamnosus
were investigated to assess their ability to adhere to the cells of the intestines
and prevent the build up of pathogenic bacteria. The results showed that these
strains could adhere to the surface of the intestines and both L.acidophilus
and L.rhamnosus inhibited the binding of enteropathogenic (causing disease in
the intestines) E.coli and enterohemorrhagic (causing bleeding in the intestines)
E.coli to host intestinal cells. Therefore probiotic supplements containing
these species of bacteria may be useful for the prevention of E.coli colonisation
in the digestive tract. (1) L.acidophilus has been shown to activate immune
cells in in vitro models. Significant dose dependent responses to L.acidophilus
murine splenocyte coincubations can be seen using the MTT colorimetric assay
- a technique used to measure cellular proliferation. Increased rates of proliferation,
indicated by higher optical densities are a clear indication of L.acidophilus
immune cell stimulation resulting in increased proliferation of the immune cells
with increasing numbers of stimulating L.acidophilus. (2).
This study discovered that the addition of L. acidophilus
to oral rehydration therapy was effective in the treatment of children with
acute diarrhea. It concluded that L.acidophilus could alleviate the symptoms
by decreasing the duration of diarrhea. (4) One study was designed to investigate
whether L.acidophilus administration could be an effective treatment for suffers
of diarrhea, by preventing the growth of certain causative bacteria. The results
of this study showed that L.acidophilus was effective in eradicating Klebsiella,
Proteus and Staphylococcus, all responsible for diarrhoea (5).
This study investigated the effects of L.acidophilus
of the digestion of lactose in milk drinks fed to children. The results showed
that for lactose-maldigesting children, milks inoculated with L. acidophilus
or with a yogurt culture were associated with decreased symptoms compared with
those with uninoculated milk. (6) The effect of Lactobacillus acidophilus on
lactose utilization of humans was tested in this study. The results showed that
the beneficial effect of Lactobacillus acidophilus was immediate for alleviation
of symptoms associated with lactose intolerance. The lactose digesting effects
of this bacteria occurred in the intestinal tract and not in the milk product
used during the study. (7)
Lactobacillus acidophilus belongs to the G.R.A.S. list
(Generally Recognized As Safe) established by the Food and Drug Administration
(F.D.A.) in 1987, as this species has been used for centuries in fermented food.
Moreover, L.acidophilus has been widely consumed in dietary supplements or drugs
for more than 50 years, has not been identified in infections, and there are
no records of L.acidophilus related side effects.
Contra-Indication and Interactions
Levels of Lactobacillus Acidophilus decrease during administration
of antibiotics. Therefore supplementation should be considered during antibiotic
use, but antibiotics and probiotics should be taken at least two hours apart
1. 1. K. Johnson-Henry
and P.M. Sherman, Research Institute, Hospital for Sick Children, 2000 2. J.M.
Green-Johnson, Dept of biology, Acadia University, Wolfville. Canada (unpublished
results) 3. Gastroenterology 1984 Jan;86(1):174-93 4. J Pediatr Gastroenterol
Nutr. 2000 Jan;30(1):68-72 5. Smirnov et al, (1994). Results of L.acidophilus
clinical trial. Institut Rosell internal report. 6. J Dairy Sci. 1995 Aug;78(8):1657-64.
7. J Dairy Sci. 1983 May;66(5):959-66.
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