Making Sense of Probiotics
Consider for a moment that the human gut contains 10 times more bacteria than all the human cells in the entire body.
1. The intestinal tract is home to approximately 100,000,000,000,000 (100 trillion)
2. This enormous biomass consists of over 400 known diverse bacterial species that generate intense metabolic activity and are of key importance for human health.1 In addition to promoting normal gastrointestinal functions and providing protection from infection, the intestinal microflora also exerts important effects on systemic metabolism and immune function. While the exact roles of many of these organisms are not yet clearly understood, basic scientific and clinical research is beginning to characterize the diverse functions
of normal intestinal micro-biota.
Pro-biotic are either member species of the essential intestinal micro-flora or they are transient species affecting benefit as they pass through the gastrointestinal tract.
PRO-BIOTIC - Definition and Species
In the early 1900s, the Nobel laureate Metchnikoff reported favorable health effects and improved longevity from consuming fermented milk products.
3. He suggested that ingestion of live lactic acid bacteria may improve the balance of the gastrointestinal micro-flora. In 1965,Lilly and Stillwell introduced the term “pro-biotic” for growth promoting factors produced by microorganisms.
4. Fuller popularized the word “pro-biotic” in 1989, describing pro-biotics as live microbial feed supplements, which benefit the host by improving intestinal microbial balance.
5. In 2001, an International Life Sciences Institute Europe consensus document proposed a simple and now widely accepted definition of pro-biotic as “viable microbial food supplements which beneficially influence
the health of humans.”
6. Probiotics consist of lactic acid producing bacteria (LAB), non-lacticacid producing bacterial species,
and non-pathogenic yeast.
LACTIC ACID PRODUCING PRO-BIOTIC
Lactobacillus
The genus Lactobacillus normally predominates in the small intestine.Lactobacillus species are facultative anaerobes although some species,such as Lactobacillus plantarum, can respire oxygen turning it into
hydrogen peroxide. Of the more than 100 Lactobacillus species, the following are commonly used probiotics:
L. acidophilus L. fermentum L. paracasei
L. brevis L. gasseri L. plantarum
L. bulgaricus L. helveticus L. reuteri
L. casei L. jensenii L. rhamnosus
L. crispatus L. johnsonii L. salivarius
Bifidobacterium
Bifidobacterium is another well-documented genus of lactic acid producing bacteria. Bifidobacteria are strictly anaerobic and normally vie for predominance in the large intestine. The following 8 of the more than 30 Bifidobacterium species are frequently used as probiotics:
B. adolescentis B. breve B. longum
B. animalis B. infantis B. thermophilum
B. bifidum B. lactis
Streptococcus
Streptococcus species are not typically associated with health benefits and often highly pathogenic. However, one facultative anaerobic species, Streptococcus thermophilus, is known to promote health.
It is one of the two primary species found in yogurt cultures, the other being L. bulgaricus.
Enterococcus
Found in a number of probiotic products, the facultative anaerobe Enterococcus faecium has a variety of beneficial characteristics. However, E. faecium has evolved from a relatively nonpathogenic commensal bacteria to the third most common cause of hospital acquired infections and now accounts for over 10% of enterococcal clinical isolates.7,8 It has developed extensive resistance to antibiotics.
NON-LACTIC ACID-PRODUCING PROBIOTICS
Bacillus
Bacillus species are ubiquitous facultative or obligate aerobic,
spore-producing organisms found in the soil and water.9 Spores of a
number of Bacillus species are used as probiotics and are often referred
to as soil-based probiotics. A number of species including Bacillus
subtilis, B. coagulans, B. licheniformis, and B. cereus have shown benefit.
However, Bacillus species have well documented toxicities that include
the potential production of enterotoxins. Bacillus probiotic products
have been plagued by problems with mislabeling and associated with
gastroenteritis and diarrhea.9
Proprionibacterium
Proprionibacterium species are Gram-positive, nonsporing,
pleomorphic rods first described in 1906.10 Usually anaerobic, some
strains tolerate very small amounts of air (microaerophilic). Their
primary fermentation products are proprionic acid, acetic acid, and
carbon dioxide. Proprionibacterium species are commonly found on
the skin. Proprionobacteria stimulate the growth of bifidobacteria,
reduce pathogenic fecal Staphylococcus and Enterobacteriaceae
populations, decrease the fecal concentration of carcinogenic enzymes,
and favorably modulate the immune system. Select Proprionibacterium
species may have good potential as probiotics.
YEAST PROBIOTICS
Saccharomyces
The yeast genus Saccharomyces contains 7 or 10 species of which only
S. boulardii is used as a probiotic.11 Unaffected by gastric acid and bile,
S. boulardii proliferates along the entire gastrointestinal tract. It has
been used alone and in combination with other probiotics to
successfully manage a variety of gastrointestinal disorders especially
diarrhea and Clostridium difficile-associated disease.
PROBIOTICS - Major Species and Characteristics
Lactobacillus
Lactobacillus species are facultative anaerobic, Gram-positive,
non-spore forming rods or elongated ovals (coccobacilli). They are
characterized as homofermentative, meaning they primarily produce
lactic acid as a fermentation end-product, or heterofermentative,
meaning lactic acid, carbon dioxide, ethanol, and acetic acid are the
principal fermentation end-products.13 Since the advent of gene
typing and hybridization technologies, Lactobacillus classification has
evolved rapidly and there are presently over 100 accepted species.14
Lactobacilli possess many important features that make them valuable
probiotics. These include production of enzymes to digest and
metabolize proteins and carbohydrates, synthesis of B vitamins and
vitamin K, breakdown of bile salts, enhancement of innate and
acquired immunity, and inhibition of proinflammatory mediators.
Lactobacillus species exhibit antimicrobial activities against an array of
pathogens including Pseudomonas, Escherichia coli, Staphylococcus
aureus, Salmonella, Shigella, Candida, and Helicobacter pylori.
L. acidophilus is undoubtedly the best known probiotic. For decades a
variety of lactobacilli were misclassified as L. acidophilus. Only in
recent years have these organisms been recognized as distinct species
with distinguishing features and unique potential health benefits. One
confusing result of new, refined methods of microbial classification is
that many of the healthful effects long attributed to “L. acidophilus”are
now recognized to belong to other Lactobacillus species. One such
species, L. rhamnosus, is now appreciated as highly beneficial. It was
not until 1989 that L. rhamnosus was recognized as a separate species
and it was not viewed as beneficial for many years. Evolving
reclassification of “L. acidophilus” species was largely responsible for
the results of Hughes’ 1990 study of probiotics that found almost none
of the “L. acidophilus” probiotics tested contained L. acidophilus. The
most commonly identified species was L. rhamnosus.
L. rhamnosus strains are probably the most extensively studied
probiotics.Many studies have repeatedly found that L. rhamnosus GG
can treat and prevent rotavirus diarrhea, prevent antibiotic-associated
diarrhea, and treat diarrhea caused by Clostridium difficile.6,12,17
L. rhamnosus has significant immunomodulatory properties. The
effects of L. rhamnosus GG were examined in infants with allergies to
cow’s milk and atopic dermatitis and associated with significant
improvements compared to placebo.18 The probiotic reduced several
markers of intestinal inflammation in the infants possibly due to
improved intestinal barrier function leading to decreases in antigen
translocation. Two more recent studies have also demonstrated the
benefits of L. rhamnosus GG in preventing and treating atopic
dermatitis and eczema in infants.19,20
L. acidophilus was once thought to be indigenous to the human
gastrointestinal tract and that consuming L. acidophilus restocked the
intestines with normal microflora. L. acidophilus is now known not to
be indigenous to the bowel, but species previously classified as
L. acidophilus, such as L. gasseri, L. crispatus, and L. johnsonii, are
indigenous.21-23 Most Lactobacillus probiotics are not indigenous to
the human gastrointestinal tract, but colonize the intestines when
regularly consumed. Vegetarians and people ingesting traditional
plant-based diets have high colonization rates of certain lactobacilli
such as L. plantarum, L. rhamnosus, and L. acidophilus. Colonization
rates with these important microorganisms are low in individuals
consuming a standard highly processed Western. It is now clear that
probiotics must be regularly consumed to restore and maintain the
normal intestinal balance of essential microorganisms.
Bifidobacterium
Bifidobacteria were identified at the end of the 19th century as
irregular Y-shaped bacteria and termed Bacillus bifidus.24 For most of
the 20th century they were classified as members of the genus
Lactobacillus because they produced lactic acid. Numerous studies
detailing a unique physiology and nutritive requirements led to the
creation of distinct genus called Bifidobacterium presently composed
of over 30 species. Bifidobacteria are strictly anaerobic, non-spore
forming rods. They are among the more common LAB in the human
intestinal tract competing with Bacteroides species for predominance
in the colon. They constitute 95% of the gut bacterial population in
healthy, breast-fed infants.25 Bifidobacterium populations tend to
remain stable in the adult human intestine, but may decline with age;
the decline may even contribute to aging.26 Their numbers are
devastated by antibiotics and other environmental toxins. The
presence of Bifidobacterium within the intestinal tract is associated
with numerous health benefits.
The list of health benefits for probiotic Bifidobacterium is extensive.
Nutritionally, they all metabolize lactose, generate the L(+) form of
lactic acid, synthesize certain vitamins, ferment indigestible
carbohydrates, and produce beneficial short-chain fatty acids.
B. bifidum, B. breve, and B. lactis all exhibit protective effects against
acute diarrhea. B. longum and B. bifidum have been shown to reduce
the incidence and duration of antibiotic-associated diarrhea as well as
traveler’s diarrhea. They inhibit pathogens principally by the
production of organic acids and hydrogen peroxide and through
stimulation of the host immune system. Bifidobacterium species have
been found to relieve constipation, alleviate inflammatory bowel
disease, and reduce serum cholesterol levels. In animal models,
B. longum and B. breve have been shown to prevent DNA damage
which suggests probiotics may prevent or delay the onset of
certain cancers.25
Saccharomyces boulardii
S. boulardii, formally known as S. cervesiae variant boulardii Hansen
CBS 5926, is a non-colonizing, lactic acid producing yeast.11 It has
been widely used worldwide as a beneficial probiotic. Clinical trials
have shown that S. boulardii prevents or treats many intestinal
maladies including antibiotic-associated diarrhea, recurrent
Clostridium difficile-associated disorders, acute diarrhea, traveler’s
diarrhea, and diarrhea in tube-fed patients. In adults, S. boulardii has
been successfully used to treat AIDS-related diarrhea and to prevent
relapses of Crohn’s disease and ulcerative colitis. S. boulardii exerts
direct protective effects against the enteric pathogens Vibrio cholerae
and E. coli. It is known to exert several beneficial effects on the host
gastrointestinal tract through diverse mechanisms of action. In vivo,
S. boulardii secretes proteases and other substances that break down
bacterial enterotoxins and inhibit their binding to intestinal receptors.
S. boulardii stimulates host immune defenses, reduces intestinal
secretions, inhibits enterotoxin-induced inflammatory responses and
enhances production of intestinal trophic factors such as brush border
membrane enzymes and nutrient transporters.
Streptococcus thermophilus and Lactobacillus bulgaricus
These two species of LAB are the primary cultures used in yogurt
production.27While both species are transient and do not colonize the
intestinal tract, they have significant health benefits. They metabolize
lactose, improving lactose intolerance. In vitro studies have shown that
these two species have potent antimicrobial activities against
Pseudomonas, E. coli, Staph. aureus, Salmonella, and Shigella. In some
cases, this antimicrobial activity was compared to that of L. acidophilus
and found to be stronger. L. bulgaricus has also shown in vitro activity
against H. pylori. These two yogurt culture bacteria have been used for
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millennia to promote health and longevity and will, without doubt,
have a continuing vital role as probiotic supplements.
Enterococcus faecium
E. faecium, formerly called Streptococcus faecium, is a ubiquitous
organism found in a variety of foods as well as in soil and on plants.
It colonizes the skin, intestinal tract, and genitals in humans. E. faecium
is a hearty species capable of surviving higher temperatures and lower
pHs than other probiotics. Several studies have suggested E. faecium
effectively prevents and resolves antibiotic-associated diarrhea and it
has been used to treat acute gastroenteritis. In vivo and in vitro studies
have demonstrated an inhibiting effect against several pathogenic
organisms including Staph. aureus, E. coli, Salmonella, Clostridium, and
Listeria.28 No longer a nonpathogenic commensal bacterium,
E. faecium has increasingly become capable of causing severe, often
life-threatening infections.7 The acquisition of antibiotic resistance by
enterococcal species is a growing clinical problem. At present about
one-half of E. faecium clinical isolates are resistant to the critically
important antibiotic vancomycin.29 The risks of E. faecium use as a
probiotic are rapidly becoming greater than the potential benefits.
PROBIOTICS - Health Benefits
Probiotic organisms have been shown to be effective in a variety of
both gastrointestinal and extra-intestinal conditions beyond modulating
intestinal microflora and replenishing and maintaining normal gut
commensal bacterial equipoise.
Diarrhea
The benefits of probiotics have been clearly documented in four types
of diarrhea: antibiotic-associated diarrhea, Clostridium difficileassociated
diarrhea (CDAD), rotavirus diarrhea, and infectious
diarrhea.1,30-32 Antibiotic-associated diarrhea and CDAD are the best
documented conditions that may be prevented or treated with
probiotics.12,33 A meta-analysis of 25 randomized, controlled trials
involving 2,810 patients concluded that probiotics significantly
reduced the relative risk of antibiotic-associated diarrhea by 57%.12
Three types of probiotics were found to be most beneficial: S. boulardii,
L. rhamnosus GG, and multispecies probiotic combinations. A
meta-analysis of 23 randomized, controlled trials conducted by the
United Kingdom West Midlands Health Technology Assessment
Group found that probiotics significantly reduced the relative risk of
CDAD by 46%.34 S. boulardii has been consistently found to reduce the
risk of new and recurrent cases of CDAD. S. boulardii has been found
to be particularly beneficial for adults who have suffered more than
one bout of recurrent CDAD.35,36 Rotavirus-induced diarrhea, a
common problem in hospitalized children, has been shown to be
prevented by L. rhamnosus, L. casei, S. thermophilus, and B. bifidum.6
L. rhamnosus, L. reuteri, L. casei, and S. boulardii have been found to
either effectively prevent or treat community-acquired infectious
diarrhea in infants and children.1
Vaginal dysbiosis
Dysbiosis refers to the disruption of the normal microbial ecosystems
in body tissues that may lead to clinical symptoms and disease. As in
the intestinal tract, the normal vaginal microflora can be disrupted and
undesirable microorganisms can proliferate especially during and
following courses of antibiotics. Historically, preparations of LAB,
introduced either as yogurt soaked tampons or douches or
encapsulated probiotic suppositories, have been used to check the
growth of pathogens with favorable clinical results. Unfortunately,
studies on the efficacy of probiotics for vaginal infections often have
mixed results, probably due to differences in study design, selection of
proper probiotic strains, probiotic viability, and other factors.
However, clinicians and patients alike have typically found that vaginal
infections commonly recur when drugs alone are prescribed, while
better outcomes are achieved when probiotics are applied vaginally
concomitantly with medications.32,37 Direct vaginal application may
not be necessary as studies show that orally administered probiotics
can reduce the incidence of recurrent yeast vaginitis, bacterial
vaginosis, and urinary tract infections.38
Antagonism to pathogens
The use of probiotics for both intestinal and vaginal disorders hinges
on the ability of specific strains to antagonize the growth of diseasecausing
organisms. In the intestinal tract, a delicate balance constantly
needs to be maintained between beneficial and pathogenic organisms.
A variety of factors can shift the intestinal microflora balance in favor
of pathogens. These factors include antibiotics, immunosuppressants,
stress, aging, poor diet, excessive alcohol intake, environmental
pollutants, and infections. Many studies have confirmed that
probiotics promote a more favorable balance of intestinal microflora
by reducing populations of harmful microorganisms. Probiotics
accomplish this task primarily by producing substances toxic to
pathogenic organisms such as lactic acid, acetic acid, formic acid,
hydrogen peroxide, and bacteriocins.15 Probiotic bacteria also compete
with pathogens for nutrients and living space in the gut. Bifidobacteria
are capable of absorbing large quantities of ferrous iron, depriving
pathogens of iron and inhibiting their growth. Clinically, the
re-establishment of a favorable bowel microflora balance in the gut
may manifest short-term as a resolution of diarrhea or other
gastrointestinal symptoms. Long-term, a re-established healthy
balance may reduce the risk of a variety of chronic degenerative or
immunologically-mediated diseases.17,39
Immune function enhancement
The intestines are the primary immune organ in the body. The
bowel-associated immune system contains the largest mass of
lymphoid tissue in the human body, a vitally important component of
total host immunologic capacity.40 Bowel mucosa and lymphoid tissue
are closely linked immunologically with gastrointestinal microflora.
Substantial evidence associates probiotic bacteria with modulation of
host-mediated immune responses. Probiotic bacteria boost both
innate and acquired immune responses. These include increases in
circulating lymphocytes, stimulation of phagocytosis and antigenspecific
antibody secretion, and increased production of interferon-g
and other cytokines. Immunologic enhancement properties are best
documented for L. casei, L. rhamnosus, L. plantarum, L. bulgaricus,
L. acidophilus, B. bifidum, and B. breve.While these species are almost
certainly not the only probiotics that modulate immune function, they
should definitely be part of any therapeutic probiotic regimen to
support the immune system.40-42
Digestive support
Most lactic acid probiotic bacteria are capable of metabolizing a variety
of carbohydrates, including lactose. LAB metabolism of lactose is what
enables many lactose-intolerant people to consume yogurt, but not
other dairy products. LAB ferment carbohydrates into other shortand
medium-chain organic acids in addition to lactic acid. Some LAB
species also secrete proteolytic and lipolytic enzymes that facilitate
digestion of proteins and fats. People who produce inadequate
amounts of stomach acid and cannot activate the proteolytic enzyme
pepsin and individuals with pancreatic insufficiency deficient in
pancreatic proteases and lipases all benefit from dietary
supplementation with probiotics. Enhanced protein digestion often
benefits people with allergies due to increased gut permeability defects
by reducing the ability of large proteins to cross the intestinal barrier,
enter the bloodstream, and trigger immune responses.42,43
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Short-chain fatty acid production
Probiotics especially the bifidobacteria, are able to break down and
metabolize non-digestible carbohydrates such as fiber. The major
by-products of this process are short-chain fatty acids (SCFA) such as
lactate, acetate, propionate, and butyrate. SCFA lower intestinal pH
and create an environment inhospitable to pathogenic bacteria such as
E. coli and Salmonella species. SCFA nourish colonic mucosal cells
supplying 60-70% of colonocyte energy needs. Butyrate is the
preferred energy source for colonocytes. Studies in animals and
humans have found SCFA directly stimulate colonic calcium,
magnesium, and potassium absorption, increase colonic blood flow,
enhance tissue oxygenation and transport of nutrients, and may be of
therapeutic value for various intestinal disorders.45,46
Enhancement of mineral bioavailability
Mineral absorption requires an acidic medium, especially when the
minerals are in the form of inorganic salts. Stomach acid is usually
sufficient to dissolve mineral salts, but when stomach acid is inadequate
mineral salts may not fully dissociate. LAB aid mineral absorption via the
production of acidic microenvironments adjacent to the intestinal lining
and by generating SCFA that donate protons necessary for mineral
absorption.Animal studies have demonstrated that LAB, especially in the
presence of a probiotic growth factor like inulin, increase intestinal
absorption of calcium, magnesium, potassium and zinc.46,47
Vitamin production
LAB produce small amounts of certain B vitamins, including folates and
vitamin B12.48Microbial synthesis of vitamin K in the intestine appears to
have nutritional significance in most animal species. Bifidobacteria,
streptococci, and enterococci have been shown to produce vitamin K.49
Reduction of cholesterol
Studies have shown that some probiotics can lower total serum
cholesterol and low density lipoprotein cholesterol.50-52
In vitro studies have shown L. casei and L. acidophilus effectively
remove cholesterol from culture media. Researchers postulate that
LAB assimilate cholesterol in the gut or deconjugate bile acids
disrupting the intestines-to-liver circulation of cholesterol.
Management of inflammatory bowel disease
Inflammatory bowel disease refers to two chronic or relapsing diseases
of unknown cause: ulcerative colitis and Crohn's disease. Although
these two diseases have some features in common, there are important
differences. Ulcerative colitis is an inflammatory disease of the colon.
Often the rectum is most severely involved. The colonic mucosa
becomes inflamed and develops ulcers. Patients experience diarrhea
frequently with blood and mucous in the stool. Crohn's disease most
commonly affects the last part of the small intestine (terminal ileum)
and parts of the large intestine. However, Crohn's disease can attack
any part of the digestive tract. The inflammation of Crohn's disease
can extend deeply into the intestinal wall and generally tends to involve
the entire bowel wall, whereas ulcerative colitis affects only the bowel
lining. Pouchitis is a complication of surgical therapy for ulcerative
colitis in which the entire colon has been removed and a pouch made
from the ileum has been connected to the anus. Pouchitis refers to
inflammation of this pouch. Evidence suggests that inflammatory
bowel disease may result from abnormal activation of the mucosal
immune system against enteric flora triggering inflammatory
mediators.1 L. casei and L. lactis have been shown to successfully treat
IBD by increasing the gut IgA immune response.53 A mixture of
B. longum, inulin, and oligofructose reduced inflammatory cytokines
and colon inflammation in patients with ulcerative colitis.54 Daily
intake of L. rhamnosus alone or intake of a proprietary combination of
L. casei, L. plantarum, L. acidophilus, L. bulgaricus,
B. longum, B. breve, B. infantis and S. thermophilus (VSL) in patients
with pouchitis can provide significant clinical benefit and delay the
first onset of pouchitis in patients without symptoms.55 S. boulardii
has been shown to prolong remission and reduce relapses in patients
with Crohn’s disease.56 There is considerable interest in the use of
probiotics for inflammatory bowel disease among gastroenterologists.
Amelioration of food allergy
The ability of probiotics to reduce the symptoms of food allergy was
noted over 20 years ago.57,58 Since then, several well-designed studies
have indicated that supplementation with specific probiotic strains are
effective for atopic disorders. In infants with atopic eczema and cow’s
milk allergy, a whey formula supplemented with L. rhamnosus GG was
shown to significantly improve clinical symptoms and markers of
intestinal inflammation.18 In children with atopic dermatitis, a
combination of L. rhamnosus and L. reuteri proved beneficial.59
Consumption of these select Lactobacillus probiotics downregulates
over-expressed immune responses.
Alleviation of irritable bowel syndrome
Irritable bowel syndrome is a common multifactorial gastrointestinal
disorder characterized by flatulence, diarrhea, constipation, and
abdominal discomfort and pain. Although challenging to study
because of the heterogeneous patient populations, clinical trials with
the individual strains B. infantis60 and L. plantarum61 found that these
probiotics effectively reduced irritable bowel syndrome symptoms
such as abdominal pain and discomfort, bloating and distention,
bowel movement difficulty, and flatulence. In a small pilot study of
patients with irritable bowel syndrome, a food elimination diet
followed by treatment with a multispecies probiotic preparation
(Vital-10® powder) containing B. bifidum, B. infantis, L. acidophilus,
L. rhamnosus, L. plantarum, L. salvarius, L. bulgaricus, L. casei, L. brevis,
and S. thermophilus improved pain, stool frequency, and quality of life
scores.62 The efficacy of multispecies preparations for irritable bowel
syndrome was confirmed by a double-blind, placebo-controlled trial
that found a combination of two strains of L. rhamnosus, B. breve, and
Propionibacterium freudenreichii spp. shermanii reduced symptoms of
pain, distension, flatulence, and abdominal gurgling sounds
(borborygmi) by over 40%.63
Anti-carcinogenic activity
There is increasing evidence that probiotics have anti-mutagenic and
anti-carcinogenic activities in the colon.64 Probiotics have been shown
to inhibit aberrant crypt (precancerous lesions) formation and tumors
in animal models.65 Probiotic bacteria may exert anti-carcinogenic
effects through a variety of mechanisms. LAB produce organic acids
lowering intestinal pH which is strongly associated with a lower
incidence of colon cancer.66 LAB are able to bind and breakdown
dietary mutagenic compounds thereby reducing host exposure.
Probiotics may mediate tumor suppression through stimulation of the
host immunoprotective response. Probiotic bacteria enhance cytokine
production (interferon-g, interleukin-1b, tumor necrosis factor-a),
macrophage and lymphocyte activation, T- and B-cell proliferation,
and antibody production.66 Evidence for anti-tumor activity of LAB
has been reported in studies using pre-implanted tumor cells in animal
models. Feeding cultures of LAB to mice has also been shown to
inhibit the growth of injected tumor cells.66
PROBIOTICS - Frequently Asked Questions
How do I know I need probiotics?
Probiotics may be used to maintain a healthy, balanced intestinal
microflora. Modern diets consisting of highly processed, sterilized
foods are deficient in essential microorganisms such as L. plantarum,
L. rhamnosus, L. casei, and L. acidophilus.67 These organisms must be
consumed to maintain their needed presence in the gastrointestinal
Page 5
tract. Infants born by cesarean section and formula-fed infants have
disordered intestinal microflora that may have short- and long-term
adverse health consequences and may benefit from probiotics.68,69
Aging is associated with microflora alterations especially a decrease in
the numbers of bifidobacteria.26 Probiotics may reverse age-associated
changes in intestinal microbial balance. Probiotics may be taken along
with antibiotics, immunosuppressants or other drugs that disrupt the
microflora equilibrium. Symptoms that have been extensively studied
and shown to be improved by probiotics include antibiotic-associated
diarrhea and other types of diarrhea, vaginitis, lactose intolerance,
intestinal and vaginal dysbiosis, abdominal distention, flatulence, and
constipation. Some probiotics have also been shown to alleviate food
allergies and modulate the immune system. When symptoms are
present, the need for probiotics is best determined in consultation with
a health practitioner experienced in their use.
What probiotics do I take?
Consulting a knowledgeable health practitioner experienced in the use
of probiotics is the optimal approach to determine which probiotics
may be of most benefit. The appropriate choice of probiotic may be
guided by clinical reports and research published in the medical
literature. For example, L. acidophilus, L. bulgaricus, B. longum, and
S. thermophilus have been shown to reduce the risk of diarrhea
induced by the antibiotics.12 At least six rigorous clinical trials have
shown that S. boulardii substantially decreases the risk of antibioticinduced
diarrhea and protects against C. difficile.12 Rotavirus
gastroenteritis in children can be prevented by L. rhamnosus, L. casei,
S. thermophilus and B. bifidum.6 L. rhamnosus has been shown to
effectively reduce the symptoms of food allergies.18,59 H. pylori, an
organism associated with peptic ulcer disease, is antagonized by a
number of lactobacilli including L. casei, L. delbrueckii, L. helveticus,
and L. acidophilus, as well as by Bifidobacterium.70,71 For people with
irritable bowel syndrome or inflammatory bowel disease a
combination of lactobacilli and bifidobacteria appears to offer the
most benefit.1,31 People desiring to favorably alter their intestinal
microflora are best served by a broad combination of Lactobacillus and
Bifidobacterium species.
How will I know if probiotics have helped me?
If symptoms are present, a reduction or resolution of symptoms is the
best indication probiotics have helped. Symptoms may take days or
even weeks to improve depending on the individual’s response to the
probiotics and the severity of the underlying condition. If probiotics
are used in the absence of symptoms as a general health measure to
restore a balanced intestinal microflora, then it may not be apparent
that probiotics are helping.
Are there any side-effects from probiotics?
Uncommonly people may experience a worsening of their clinical
symptoms following the initiation of probiotics. This is attributed by
some practitioners to a “die-off” effect as pathogenic bacteria die
releasing toxic cell products. The exact mechanism for a transient
worsening in symptoms is unknown, but it does occur. Persistence in
taking the probiotics is usually rewarded by an improvement in
symptoms. Some individuals may experience gas, abdominal
discomfort, and even diarrhea that usually resolve with time. Rarely,
probiotics have been associated with opportunistic infections.
Are there tests that can assess my response to probiotics?
With certain exceptions, such as the presence of C. difficile toxin or
pathogenic microorganisms in the stool, there are no readily available,
reliable clinical laboratory tests that can assess a response to probiotics.
Many practitioners order stool cultures on the premise that probiotic
content in the intestinal tract is reflected in stool count.However, most
probiotics are fastidious and not easily cultured from routine stool
samples. Intestinal biopsy and DNA amplification techniques are used
currently to demonstrate probiotic colonization of the intestines. A
negative stool culture for probiotic species does not indicate lack of
colonization, presence, or benefit.
Should I buy a probiotic containing prebiotics?
Prebiotics are carbohydrates that are indigestible by the human
intestine and selectively stimulate the activity and growth of certain
bacteria in the colon.Most prebiotics are non-digestible chains of 2 to
9 sugar molecules (oligosaccharides). They are commonly found in
chicory, asparagus, artichokes, onions, garlic, leeks, and soybeans as
well as in human breast milk and cow’s milk. Prebiotics have attracted
great attention as a way of increasing the number of healthy beneficial
commensal bacteria in the intestine. The most extensively used
prebiotics include lactulose, oligofructose, galactooligosaccharides,
soybean oligosaccharides, and chicory-derived inulin. Some prebiotics,
such as lactulose, are synthetic, whereas most other oligosaccharides
are natural food components.
After ingestion, prebiotics pass through the small intestine into the
colon where they are selectively utilized by the beneficial LAB
microorganisms.Numerous studies suggest bifidobacteria prefer short
chain oligosaccharides and recent studies suggest oligofructose,
soybean oligosaccharides and galactooligosaccharides are the most
bifidogenic.72,73 Prebiotics can significantly increase the numbers of
bifidobacteria in the colon and decrease the populations of pathogenic
bacteria such as clostridia, fusobacteria, and Gram-positive cocci.
Inulin is a commonly used prebiotic that is not usually associated with
the gas and bloating sometimes associated with other prebiotics. Inulin
is also more difficult for pathogens to metabolize and unlike some
highly processed, long chain fructooligosaccharides less likely to be
used as a food source by pathogenic bacteria. Probiotics combined
with prebiotics, termed synbiotics, are generally a good choice.
When and how should I take a probiotic?
People often receive contradictory answers to this question. Probiotic
labels from different manufacturers may directly contradict each other.
Some suggest that the probiotics be taken with meals whereas others
recommend between meals. Health professionals are also divided on
this topic. Advocates of ingesting probiotics with meals reason that
food buffers stomach acid thereby providing protection for the
microorganisms. Those who recommend taking probiotics without
food usually suggest consuming them with lots of water. The water
dilutes the stomach acid and may help move the organisms quickly
into the intestines minimizing exposure to acid and bile. Few studies
provide direct support for either approach. However, numerous
studies have administered probiotics with meals and documented
significant benefits. The most prudent approach is to consume
probiotics with moderate amounts of food no warmer than room
temperature.
If I am taking antibiotics, when should I take a probiotic?
In the past, people were often told not to take probiotics while on
antibiotics. The thinking was that the antibiotics would kill ingested
probiotics. The trouble with this approach is that it allowed pathogenic
microorganisms to proliferate unopposed by beneficial bacteria often
resulting in antibiotic-associated diarrhea and other problems.
Probiotics should be taken while on antibiotics. The probiotics should
be taken at least 1 hour before or 2 hours after ingestion of antibiotics.
How much probiotic do I take?
The answer depends on whether the probiotics are being used for
therapeutic reasons or simply to maintain a healthy intestinal
microflora balance. In general, a dose of 1 billion colony forming units
(CFUs) is required to deliver significant numbers of viable probiotics
to the intestines. There is a trend toward using higher doses. The
proprietary probiotic blend VSL#3 comes in packets each containing
450 billion organisms and has been used safely in patients with
inflammatory bowel disease.Doses as high as 200 billion CFUs per day
have been safe and well-tolerated in patients following liver
transplantation. A clinical research study involving the administration
of 200 billion organisms daily of a Klaire Labs proprietary blend of 6
probiotic species to kidney transplant patients has been approved by
the Western Institutional Review Board and is ongoing.
Do probiotic organisms survive exposure to stomach acid
and bile?
Different probiotic organisms have differing sensitivities to stomach
acid and bile. S. boulardii is not affected by gastric acid. LAB are more
sensitive and do not thrive in an excessively acidic or alkaline medium.
Some LAB, such as L. rhamnosus, are more sensitive than others.
Probiotic manufacturers have devised a number of methods to
enhance probiotic survival after oral administration. Some
manufacturers offer enteric coatings for the probiotics composed of
cellulose or, in many cases, synthetic plasticized polymers. Many
individuals with environmental sensitivities cannot tolerate the
plasticized polymers. One manufacturer has developed an innovative
process that coats probiotic microorganisms with vegetable-derived
fatty acids. This micro-encapsulation not only shields the probiotics
from stomach acid, it protects them from air and moisture and keeps
them viable at room temperature. Klaire Labs makes use of a highly
purified marine plant extract in an acid-stable technology. The extract
is mixed with the probiotics.When exposed to stomach acid it forms a
gel-like matrix surrounding the microorganisms protecting them from
gastric acid. When delivery of probiotics to the oropharynx,
esophagus, and stomach is desirable, probiotics without a gastric acid
protective delivery system should be selected.
Do probiotics have to adhere to the intestinal tract to provide
a benefit?
Adherence to the intestinal mucosal lining is just one characteristic
among many that may, or may not, make an organism useful as a
probiotic. Adherence is a property observed under laboratory
conditions. There is evidence that normal intestinal microflora do not
adhere to intestinal epithelial cells, but live suspended in the intestinal
contents.74 Adherence is certainly not necessary for a probiotic to
provide benefit. There are numerous scientific and anecdotal reports
about the therapeutic benefits of yogurt, yet the primary bacteria
found in yogurt cultures, S. thermophilus and L. bulgaricus, are
transient microorganisms and do not adhere to the mucosa.
Modulation of immune function is a probiotic benefit that clearly does
not require mucosal adherence or intestinal colonization. Probiotics
are readily taken up by the specialized lymphoid nodules in the walls
of the small intestines called Peyer’s patches stimulating the
production of IgA, cytokines, and other mediators of immune
function. Even the administration of dead probiotics has been shown
to enhance immune function.75
Intestinal mucosal colonization has only been demonstrated in vivo for
a few probiotic strains. L. rhamnosus GG persisted in cultures from
rectal biopsies for up to 12 days after oral administration.76 Stool
culture sensitivity was quite poor even though samples were
immediately processed. In one subgroup, L. rhamnosus was found in
only 20% of final stool cultures compared to 88% of rectal biopsy
cultures. In a second study, probiotics were shown to be recoverable
from rectal biopsies when dispensed orally to critically ill patients
receiving powerful antibiotics.77 L. plantarum supplementation
reduced the populations of pathogenic Enterobacteriaceae and sulfite
reducing clostridia. In vivo studies of probiotic intestinal colonization
make two very important points. The first is that routine stool cultures
have a very limited use, if any, in assessing probiotic therapy. The
second is that sustained consumption of probiotics is required to
maintain colonization and benefit.
Is freeze-drying of probiotics harmful?
Freeze-drying, or lyopholization, is not harmful to probiotics when
done according to strict guidelines. It is an accepted practice that helps
ensure long-term probiotic microbial viability. Routine survival
studies ensure the probiotics remain viable following freeze-drying.
Probiotics that are not freeze-dried, such as liquid probiotics, have a
much shorter shelf life even when refrigerated. The short shelf life is
due to eventual toxicity of fermentation end-products to the
microorganisms. A well-known example is the die-off of yeast that
occurs over time during the fermentation of beer and wine. Freezedrying
halts fermentation thereby enhancing microbial viability.
Do all probiotics need to be refrigerated?
In general, it is highly recommended that probiotics be refrigerated to
maximally preserve their viability over time. Probiotics that have been
microencapsulated with fatty acids are the only exception and do not
need to be refrigerated. Probiotics sold in retail stores are often not
refrigerated. Consequently, industry and consumer studies have found
that 30 to 50% of probiotic products available in retail stores contain
significantly less viable microorganisms than claimed on their labels.
Although most probiotics should be refrigerated, they do not spoil or
die-off quickly at room temperature. They may be left at room
Page 6
temperature for days and even weeks without a great loss of viable
organisms. They should not be subjected to high temperatures for
prolonged periods of time. The graphs illustrate microbial viability for
selected probiotic strains over time at 4°C (39°F), 23°C (73°F) and
30°C (86°F) and show that survival is better at low temperatures than
high temperatures. At room temperature (23°C), colony counts begin
diminishing after one to two months explaining why so many overthe-
counter retail probiotic products do not contain the labeled
amounts of viable probiotics. The charts also show that certain strains,
such as L. rhamnosus, are more temperature-vulnerable than others.
However, leaving probiotics out at room temperature or even warm
temperatures for a few hours or even a few days will only result in small
losses of organisms. Although probiotics should be shipped with cold
packs, there is no cause for concern or worry if the cold pack has
melted by the time of delivery.
Does it matter if probiotics come in plastic or glass bottles?
Probiotics are usually anaerobic organisms, meaning they live in the
absence of oxygen. Exposure to air is undesirable and even toxic.
Exposure to moisture is potentially more detrimental to freeze-dried
probiotics than air. Some people argue that probiotics should be
packaged in glass bottles to minimize exposure to air and moisture.
However, the difference in permeability between glass and
high-density polyethylene (HDPE), a plastic commonly used for
bottling, is negligible. Furthermore, once the container has been
opened, air and moisture enter the bottle and the relative permeability
of glass and HDPE becomes irrelevant. The placement of desiccants
inside probiotic containers is a good way to minimize moisture inside
the container be it glass or plastic. Bottling probiotics in glass or HDPE
containers is equally acceptable.
Is it beneficial to have the supernatant included in
the probiotic?
Supernatant is culture medium transformed by the bacteria as they
multiply adding a variety of substances to the original medium. Milk is
an example of a culture medium; yogurt is an example of a supernatant.
At least one company claims that including the supernatant with the
bacteria provides additional health properties. Additional benefit to the
supernatant is possible, although the evidence is scant. Maintaining the
supernatant during production could be detrimental to probiotic
survival. The by-products of fermentation may be toxic to the probiotics.
The hypothetical benefits of including supernatant seem to be
outweighed by the negative impact on probiotic viability.
Can probiotics be used for infants?
Probiotics have been used safely and with benefit in infants. A
newborn’s intestinal tract is sterile and does not harbor
microorganisms. Microbial colonization begins at birth. During the
first week of life, Streptococcus, Clostridium, Bifidobacterium, and
Lactobacillus all vie for predominance. By the end of the first week,
bifidobacteria are usually established as the predominant bacteria.
Breast-fed infants typically have much higher numbers of
bifidobacteria in their intestinal tracts than do formula-fed infants
who have higher levels of E. coli and other pathogenic coliform
bacteria. This is due in part to the presence of bifidogenic substances
in breast milk.
Although the newborn intestinal tract is quickly colonized, it is not
fully developed. Infants are unable to metabolize a form (isomer) of
lactic acid known as D(-). Exposure to D(-)-lactic acid could
theoretically lead to D(-)-lactic acidosis, a serious condition.78 Some
have advocated that probiotic formulations intended for infants
should not include D(-)-lactic acid producing organisms such as
L. acidophilus, L. brevis, L. plantarum, or L. bulgaricus. However, there
are no reports of D(-)-lactic acidosis in infants due to probiotics and
D(-)-lactic acid producing probiotics have been used safely in infants.
Clinical trials have demonstrated the benefits and safety of probiotics
in infants. In one controlled trial, infants age 3 to 24 months, received
an average of 41 million or 3.7 million CFU each of B. lactis and
S. thermophilus per kilogram each day in a standard milk-based
formula for an average of seven months. The probiotics were well
tolerated and the infants receiving probiotics had adequate growth, less
colic or irritability, and a lower frequency of antibiotic use.79 In
another study, 190 million CFU B. bifidum and 14 million CFU
S. thermophilus per gram of formula reduced the incidence of acute
diarrhea and rotavirus shedding during hospital stays.80 Two studies
have found probiotic supplementation significantly improves infants
with atopic eczema.18,19 A low dose of 60 million CFU L. rhamnosus
GG did not decrease the incidence of necrotizing enterocolitis in
preterm infants with a gestational age less than 33 weeks.81 However, a
proprietary probiotic formulation containing 10 billion CFU of
L. acidophilus and B. infantis per capsule administered with breast milk
significantly reduced the incidence and severity of necrotizing
enterocolitis in very low birth weight infants.82
CONCLUSION
Probiotics have been used by people for millennia since the time
humans first consumed fermented milk products. Probiotics can be
essential for the normal digestive, endocrine and immunological
functions of the bowel. They inhibit pathogenic microorganisms and
have been used therapeutically to treat a variety of gastrointestinal and
even systemic disorders. Probiotics transiently colonize the bowel and,
except when used to treat an acute disorder, must be regularly
consumed to maintain benefit. Selection of appropriate probiotics,
alone and in combination, is best done in consultation with an
experienced, knowledgeable health practitioner.
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