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The Health Effects of Lactobacillus acidophilus


In a study of Bolivian children, ... Probiotics and Colon Cancer (moved to here) - need ref by title so that citations in table can be found Very nice job. – PowerPoint PPT presentation

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Title: The Health Effects of Lactobacillus acidophilus

The Health Effects of Lactobacillus
acidophilus Oliver Wyckoff , Beloit College
ABSTRACT Lactobacillus acidophilus is a species
of bacteria commonly found in the human body. My
hypothesis is that L. acidophilus is beneficial
to humans immunologically, may help to lower
cholesterol, and reduce the risk for cancer.
This poster provides peer reviewed journal
articles with studies validating the health
effects of L. acidophilus, including the
immunological benefits, effects on
carcinogenesis, and cholesterol. L. acidophilus
has many health benefits and should be integrated
into a balanced, healthy diet. Based on
peer-reviewed studies, a daily dosage of 109
colony forming units, or approximately 1 cup of
yogurt, is most beneficial.
DISCUSION The research regarding L. acidophilus
is confronted by two major challenges the
presence of multiple strains of L. acidophilus
and the difference between in vitro and in vivo
studies. There are many different strains of L.
acidophilus and each strain can produce different
results. Some studies have used strains found in
other mammals, and others have used separate
strains found in humans (13). This could be a
factor in the conflicting results found between
studies. The other major challenge regarding
research are studies that test L. acidophilus in
vitro versus those that test the bacteria in
vivo. Because L. acidophilus is part of a
dynamic digestive tract with hundreds of other
microorganisms, and because there are many
different interactions going on in the human
body, in vivo studies are greatly preferred.
However, many researchers have used in vitro
studies to support grand hypotheses without in
vivo experiments. In vitro studies should be
viewed with a more critical eye because they
cannot replicate the complexity of the human
METHOD The author reviewed relevant peer-reviewed
journal articles and peer-reviewed websites to
gather information related to L. acidophilus.
INTRODUCTION Lactobacillus acidophilus is one of
the most important probiotic species. L.
acidophilus is a symbiotic lactic acid producing
bacterium found in the mouth, gastrointestinal
tract, and vagina. L. acidophilus, along with
other probiotic microorganisms, enters the human
body through the consumption of foods containing
high concentrations of the organism (1). L.
acidophilus is commonly found in yogurt and other
fermented dairy products. L. acidophilus
naturally produces several compounds that are
beneficial to the human body, including vitamin
K, the enzyme lactase, and the antibiotics
acidolin, acidolphilin, lactocidin, and
bacteriocin (2). L. acidophilus has been shown
to aid in the synthesis of B-vitamins during the
production of dairy products. Shahani et al found
that L. acidophilus increased the concentrations
of niacin, pantothenic acid, pyridoxine, biotin,
and folic acid in diary products when they are
fermented. Many different doses of L. acidophilus
have been used in clinical studies, but a daily
dose of 109 colony forming units has been found
to be the most beneficial (1). Translated into
yogurt, the suggested daily dosage varies greatly
because different brands have varied
concentrations, and concentrations can also vary
between containers. However, one serving of
approximately one cup of live-culture yogurt per
day should provide an adequate amount of live L.
acidophilus cells.
Figure 1. Probiotics and Colon Cancer
Figure 2. Human Colonic Microflora
RESULTS L. acidophilus has been shown to be
beneficial immunologically, especially with
diarrhea and intestinal disorders. In a study of
Bolivian children, Grandy et al (3) found that L.
acidophilus combined with other probiotics and a
rehydration solution decreased the duration of
diarrhea. Several other studies have found that
L. acidophilus can both prevent and treat
diarrhea. In a meta-analysis McFarland (4) found
that probiotics, particularly a mix of L.
acidophilus, Saccharomyces boulardii, and
Bifidobacterium bifidum, significantly prevented
travelers diarrhea. In a Korean Study of
irritable bowel syndrome (5), Hong et al found
that L. acidophilus reduced pain and discomfort
in patients with irritable bowel syndrome and
could be considered safe and effective in
patients who excrete normal or loose stools. L.
acidophilus has also been shown to have a
significant effect on necrotising enterocolitis,
the rapid tissue death of portions of the bowels,
in infants. Guthmann et al (6) found that L.
acidophilus, especially when used with
Bifidusbacterium spp., was a safe and beneficial
treatment for necrotising enterocolitis. Out of
1,117 infants randomly selected to receive
probiotics, none experienced unwanted side
effects. L. acidophilus has been shown to have
many general immune enhancing functions,
including increasing the normal immune system
response towards bacteria in the gastrointestinal
tract and upper-respiratory tract, a higher white
blood cell count, and increased vaccine response.
Paturi et al found that L. acidophilus enhanced
specific gut and immune responses in mice
particularly L. acidophilus increased the number
of IgA producing cells, and enhanced the
secretion of anti-inflammatory and
pro-inflammatory cytokine. In a similar study
(7), researchers found that L. acidophilus
triggered the expression of viral defense genes.
L. acidophilus was also found to double the
number of white blood cells with phagocytic
activity after three weeks of consumption. Glück
and Gebbers (8) found that the consumption of L.
acidophilus, through a probiotic drink, reduced
potentially pathogenic bacteria in the upper
respiratory tract by 19 percent, significant to
the 99th percentile. In a separate study,
Link-Amster et al (7) found the consumption of L.
acidophilus mixed with B. bifidum after
vaccination increased total IgA antibodies by 60
over the control. L. acidophilus has been
studied to determine if it fights and prevents
cancer. Early studies by Bailey and Shahani (1)
found that milk fermented with L. acidophilus
reduced tumors in mice by 16-41. However,
further studies that have tried to elaborate on
these properties have had only moderate success.
Yazdi et al (9) found that L. acidophilus
decreased the tumor growth rate in mice through
the production of immunomodulatory cytokine
IL-12. Urbanska et al (10) found that the daily
consumption of microencapsulated L. acidophilus
by mice resulted in significant suppression of
colon tumor incidence, tumor multiplicity, and
reduced tumor size as well as the stabilization
of animal body weight and a decrease of bile
acids. In reviewing the relevant literature,
Wollowski et al (11) found that L. acidophilus
fights colon cancer by binding mutagens,
decreasing the excretion of mutagens, stimulating
the immune system, manipulating enzymes, and
decreasing the DNA damage in colon cells. The
effect of L. acidophilus on serum cholesterol is
mixed with studies showing a reduction from 0
20 percent (1). L. acidophilus has been shown
to reduce cholesterol in vitro, but studies that
have tried to replicate these results in vivo
have not been able to produce consistent results.
A recent double-blind, placebo-controlled,
cross-over study, however, has shown promising
results. Anderson and Gilliland in the Journal
of American College of Nutrition found that L.
acidophilus reduced the level of serum
cholesterol concentration in subjects (12). The
combined analysis of two treatment studies showed
that the bacteria reduced serum cholesterol by
2.9. The researchers concluded that, since a 1
reduction in serum cholesterol is associated with
approx. a 2 3 reduction in the risk for
coronary heart disease, the regular consumption
of L. acidophilus could reduce the risk of
coronary heart disease by 6 to 10 (12).    
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