204 ◾ Fundamental Food Microbiology
In addition, differences in response by humans and animals in feeding trials can produce data of
little value. Such studies are not expected to produce reproducible results.
Research conducted by considering these factors will help reduce bacterial variability. This, in
turn, will help compare results of different studies and determine whether the health benefits of
these bacteria are real or imaginary.
Current Developments
Diverse types of probiotic products are now available on the market, and their consumption has
gained popularity, especially in some European and Southeast Asian countries. Although a long
list of health benefits are claimed by manufacturers, most have not been authenticated by welldesigned scientific studies. In addition, as mentioned before, many products do not use species and
strains that have been studied for the possible beneficial effects, and many products do not have
the high viable cell numbers required to produce a benefit (Table 16.2). As a result, doubts about
the beneficial effect of these products remain.
Standard of Identity
There has been a concerted effort to develop a scientific basis for probiotic bacteria. Through a
joint effort by scientists in this area, a standard of identity has been established for the beneficial probiotic bacteria, especially those from the genus Lactobacillus. This includes the ability to
(1) adhere to GI epithelial cells, (2) interfere with adherence of enteric pathogens to GI epithelial
cells, (3) persist and multiply in the GI tract without disturbing the normal microbial balance,
(4) produce antibacterial metabolites, (5) coaggregate, (6) form a normal flora of the GI tract,
and (7) be safe to the hosts. Following a critical evaluation of the data of scientific studies, five
strains of lactobacilli are considered effective for use as probiotics: (1) Lactobacillus acidophilus
NCFM, (2) Lactobacillus casei Shirota, (3) Lactobacillus casei CRL431, (4) Lactobacillus rhamonosus
GG, and (5) Lactobacillus reuteri MM53. In the last few years, several other species or strains of
Lactobacillus and Bifidobacterium have been included in the list (Table 16.3).
Microorganisms Used as Probiotics 14
Several microorganisms have been studied for their beneficial attributes, and the list continues
to grow. However, claims are not supported by valid scientific studies and have created disbelief
among consumers. It was suggested that, to overcome the current controversy, future research
should be directed toward (1) identifying the phylogeny of a strain, (2) conducting health benefit
studies with humans, (3) explaining the exact mechanisms by which a strain produces a benefit,
(4) finding the dose level of viable cells and duration required for a benefit, (5) determining the
ability of a strain to adhere to GI epithelial cells, (6) studying the influence of a probiotic strain
on normal GI tract microflora, and (7) determining the proper and effective delivery systems of a
probiotic strain. A list of commonly used probiotics is provided (Table 16.3).
There is no doubt that some bacterial species and strains do have beneficial influence on the
health of the GI tract and probably the overall health of humans. But they have to be identified
through valid scientific studies. The indiscriminate use, imaginative claims, and unscrupulous
methods of a few have created the disbelief. A move for current collaborative scientific studies to
define the standards of identity of probiotic strains as well as the suggestions outlined in the status
In addition, differences in response by humans and animals in feeding trials can produce data of
little value. Such studies are not expected to produce reproducible results.
Research conducted by considering these factors will help reduce bacterial variability. This, in
turn, will help compare results of different studies and determine whether the health benefits of
these bacteria are real or imaginary.
Current Developments
Diverse types of probiotic products are now available on the market, and their consumption has
gained popularity, especially in some European and Southeast Asian countries. Although a long
list of health benefits are claimed by manufacturers, most have not been authenticated by welldesigned scientific studies. In addition, as mentioned before, many products do not use species and
strains that have been studied for the possible beneficial effects, and many products do not have
the high viable cell numbers required to produce a benefit (Table 16.2). As a result, doubts about
the beneficial effect of these products remain.
Standard of Identity
There has been a concerted effort to develop a scientific basis for probiotic bacteria. Through a
joint effort by scientists in this area, a standard of identity has been established for the beneficial probiotic bacteria, especially those from the genus Lactobacillus. This includes the ability to
(1) adhere to GI epithelial cells, (2) interfere with adherence of enteric pathogens to GI epithelial
cells, (3) persist and multiply in the GI tract without disturbing the normal microbial balance,
(4) produce antibacterial metabolites, (5) coaggregate, (6) form a normal flora of the GI tract,
and (7) be safe to the hosts. Following a critical evaluation of the data of scientific studies, five
strains of lactobacilli are considered effective for use as probiotics: (1) Lactobacillus acidophilus
NCFM, (2) Lactobacillus casei Shirota, (3) Lactobacillus casei CRL431, (4) Lactobacillus rhamonosus
GG, and (5) Lactobacillus reuteri MM53. In the last few years, several other species or strains of
Lactobacillus and Bifidobacterium have been included in the list (Table 16.3).
Microorganisms Used as Probiotics 14
Several microorganisms have been studied for their beneficial attributes, and the list continues
to grow. However, claims are not supported by valid scientific studies and have created disbelief
among consumers. It was suggested that, to overcome the current controversy, future research
should be directed toward (1) identifying the phylogeny of a strain, (2) conducting health benefit
studies with humans, (3) explaining the exact mechanisms by which a strain produces a benefit,
(4) finding the dose level of viable cells and duration required for a benefit, (5) determining the
ability of a strain to adhere to GI epithelial cells, (6) studying the influence of a probiotic strain
on normal GI tract microflora, and (7) determining the proper and effective delivery systems of a
probiotic strain. A list of commonly used probiotics is provided (Table 16.3).
There is no doubt that some bacterial species and strains do have beneficial influence on the
health of the GI tract and probably the overall health of humans. But they have to be identified
through valid scientific studies. The indiscriminate use, imaginative claims, and unscrupulous
methods of a few have created the disbelief. A move for current collaborative scientific studies to
define the standards of identity of probiotic strains as well as the suggestions outlined in the status