health benefits and results of studies.
We know not
everyone will want to read the more complex study data backing up
probiotic health benefits, so we have a simpler "What brand for
each condition or health problem" page HERE
all animals, have large numbers of, and many types of, microbes on
our skin, in our mouths, in womens vaginal tracts, and in the
whole length of our gastrointestinal tract. It has been estimated
that there are more microbes associated with the human body (about
100,000 Billion bacterial cells) than there are human cells in it.
As well as huge numbers, there is a huge variety of types of bacteria.
(more than 1000 different species, or types, of bacteria make their
homes on humans). Importantly, from a probiotic point of view, is
than the numbers and types of microbes that colonize our bodies interact
with each other and with our human cells. These colonizing microbes
have been shown to have important roles in digestion, metabolism,
vitamin synthesis, host cell development, immune system function,
intestinal barrier function, defense against pathogens, and other
activities that are critical to human health. Probiotics – by directly
and indirectly influencing the populations and activities of microbes
inside us – can improve human health.
describes some of the researched health benefits of consumption of
This info below comes from CDRF.org. We have put links to scientific
referrence material and different studies backing up the claims made
on a separate page HERE,
simply because there is so much of it.
Allergy is on the rise in industrialized nations. It is estimated
that the incidence of asthma in the United States doubled between
1980 and 2000. Scientists have proposed a hypothesis known as the
hygiene hypothesis to explain the rise in allergic conditions
such as asthma and eczema. This hypothesis is based on observations
that lower allergy incidence is associated with environments that
have greater numbers of microbes, such as day care centers, farms,
or in homes with siblings or pets. Sanitary living environments and
the consumption of processed foods have limited the number of microbes
in the diet. The hypothesis suggests that the exposure of infants
to microbes before the age of six months helps the immune system mature
to be more tolerant of exposure to allergens later in life. Certainly,
microbial colonization of the gut in early life is important to the
development of a properly functioning immune system.
Of course, increasing exposure
to microbes must be done safely. This hypothesis led researchers in
Finland to conduct a study evaluating the effects of a Lactobacillus
strain on incidence of atopic eczema in 132 infants at high risk of
developing eczema. The study was double-blinded and placebo-controlled.
Pregnant mothers two-to-four weeks before delivery and newborn babies
through six months of age were given Lactobacillus rhamnosus GG. Infants
were followed through two years of age and incidence of recurring
atopic eczema was recorded. The study reported a 50% drop in incidence
of recurring atopic eczema in the group receiving the probiotic supplement.
A follow up study of these same children indicated that these same
trends were still present at 4 years of age. However, no impact on
other allergic conditions was observed through seven years of age.
These results suggest that exposure to the right types of microbes
early in life may decrease the risk of atopic dermatitis. However,
a German research group using a very similar protocol and the same
probiotic microbe as the Finnish group recently reported that no impact
on incidence of atopic eczema was observed with supplementation with
L. rhamnosus GG. In addition, the German study noted a statistically
significant increase in wheezing in the probiotic group. This study
calls into question the validity of the initial observation. An ongoing
NIH-funded study in this same area will hopefully clarify a role of
prevention of allergy in newborns by L. rhamnosus GG. The effects
of probiotics on allergy have been reviewed.
It may seem hard to believe, but evidence is emerging that the gut
microbes can impact brain function. If we consider that the gut is
known as our second brain, then perhaps this concept does
not seem so far-fetched. The communication between the gut and the
brain is bi-directional: the brain controls GI tract function (stress
and emotions), but less obvious is that the gut can control pain and
emotion. Of particular interest in the discussion of probiotics, is
that gut microbes, and probiotics, have been shown to mediate some
of this bottom-up communication.
For example, one study administered
Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 for
30 days to healthy volunteers, who were assessed using validated questionnaires
measuring different psychological scales in a randomized, double-blind,
placebo-controlled design. The study found that the probiotic reduced
somatisation, depression, angerhostility, their self-blame and
were more focused on the problem solving. Other studies showed probiotic
impact on improved sleep in elderly volunteers, improved mood scores,
and decreased anxiety in patients with chronic fatigue syndrome.
The role of probiotics on
different aspects of brain function is an emerging area of research,
and care should be taken not to over interpret early animal and pilot
human studies, even though a plausible mechanism of action has been
In general, cancer is caused by mutation or activation of abnormal
genes that control cell growth and division. (A substance that causes
a mistake in genes is known as a mutagen). Most of these abnormal
cells do not result in cancer since normal cells usually out-compete
abnormal ones. Also, the immune system recognizes and destroys most
Many processes or exposures
can increase the occurrence of abnormal cells. Precautions that minimize
these exposures decrease the risk of cancer. Among the many potentially
risky exposures are chemical exposures. Cancer-causing chemicals (carcinogens)
can be ingested or generated by metabolic activity of microbes that
live in the gastrointestinal tract. It has been hypothesized that
probiotic cultures might decrease the exposure to chemical carcinogens
by (1) detoxifying ingested carcinogens, (2) altering the environment
of the intestine and thereby decreasing populations or metabolic activities
of bacteria that may generate carcinogenic compounds, (3) producing
metabolic products (e.g., butyrate) which improve a cells ability
to die when it should die (a process known as apoptosis or programmed
cell death), (4) producing compounds that inhibit the growth of tumor
cells, or (5) stimulating the immune system to better defend against
cancer cell proliferation.
Research suggests that the
consumption of probiotic cultures may decrease cancer risk. Researchers
testing the effect of the consumption of fermented milks, probiotic
bacteria, components of bacteria or extracts of bacteria have found:
A reduction in the incidence
of chemically induced tumors in rats.
A reduction of the activity of fecal enzymes (ß-glucuronidase,
azoreductase, nitroreductase, and 7-a-dehydrogenase) postulated to
play a role in colon cancer in human and animal subjects.
Degradation of nitrosamines.
A weakening of mutagenic activity of substances tested in the laboratory.
Prevention of damage to DNA in certain colonic cells.
In vitro binding of mutagens by cell wall components of probiotic
Enhancement of immune system functioning.
Taken together, these results suggest that probiotic cultures may
positively influence the gastrointestinal environment to decrease
the risk of cancer. However, cancer reduction must be demonstrated
in humans to confirm the significance of these observations. The impact
of consumption of milk fermented by Lactobacillus caseiShirota on
recurrence of superficial bladder cancer was tested. The recurrence-free
period for the Lactobacillus-consuming group was found to be almost
twice as long as the control group. In another study, this same strain
was found to decrease atypical recurrent polyps in subjects with previous
history of colonic polyp (Ishikawa et al. 2005). The European Union
(EU)-sponsored Synbiotics and Cancer Prevention in Humans project
tested a synbiotic (oligofructose plus L. rhamnosus GG and Bifidobacterium
lactis Bb12) in patients at risk for colonic polyps and looked at
intermediate end points that can be used as biomarkers of colon cancer
risk. This study found that the synbiotic decreased uncontrolled growth
of intestinal cells. These results must still be considered preliminary,
but are encouraging that impacting the colonic environment may improve
Common infectious disease
Often people wonder if probiotics have any benefit for healthy people.
Perhaps the most compelling line of research suggesting such benefit
is with studies conducted on healthy subjects, such as children in
school or day care, and tracking how often they experience symptoms
associated with colds and mild flu. Numerous such studies have been
conducted on a variety of different probiotic preparations. A meta-analysis
was published on probiotics and preventing acute upper respiratory
tract infections. After reviewing 14 human trials, it concluded that
probiotics reduced episodes of acute upper respiratory tract infections
and reduced antibiotic use.
Probiotics have also been
evaluated in at-risk populations. For example, Saran et al. showed
that a probiotic-containing food could improve growth parameters for
undernourished children. Sur et al. showed that probiotics can help
prevent acute diarrhoea in children in an urban slum in India.
Taken together, these controlled
human studies provide support that certain probiotic strains can help
avoid acute common infectious illnesses. This effect is likely mediated
by immune enhancement functions or direct inhibition of pathogens,
but mechanistic studies have not always accompanied positive clinical
Many types of diarrhoeal illnesses, with many different causes, disrupt
intestinal function. The ability of probiotics to decrease the incidence
or duration of certain diarrhoeal illnesses is perhaps the most substantiated
of the health effects of probiotics. A paper published in 2002 reviewed
nine studies on the effect of Lactobacillus as therapy for diarrhoea
in children. This paper concluded that Lactobacillus is safe
and effective as a treatment for children with acute infectious diarrhoea.
Although this meta-analysis can be criticized for combining data from
different species and strains of Lactobacillus into one analysis,
the positive nature of the conclusion suggests that at least for this
indication and for these strains, positive results have been obtained.
One common form of diarrhoea
is that associated with the consumption of antibiotics. The purpose
of antibiotics is to kill harmful bacteria. Unfortunately, they can
kill normal bacteria as well, and consequently disturb normal intestinal
function. (Note that it is certainly NOT true that antibiotics wipe
out all your normal flora, but they can act broadly and exact
a toll on your normal, non-pathogenic bacteria.) It is important to
realize that the microbiota of the healthy person is quite resilient
and will return to a pre-antibiotic status with no intervention. But
it is hypothesized that supplementing the intestine with probiotics
might help stabilize the antibiotic-induced dysbiosis and minimize
disruptive effects. One recent study documented that a probiotic containing
four Lactobacillus and Bifidobacterium strains did lead to a quicker
return to normal microbiota in antibiotic-consuming adults. A paper
published in 2002 reviewed seven studies (881 total patients) on the
impact of probiotics (Lactobacillus rhamnosus GG or Saccharomyces
boulardii) on antibiotic-associated diarrhoea. The paper concluded
that probiotics can be used to prevent antibiotic-associated diarrhoea,
but that no strong effect on the ability of probiotics to treat such
diarrhoea exists. How these probiotics accomplish this task is not
known. Not all studies have shown positive results in the prevention
of antibiotic associated diarrhoea or other symptoms associated with
A serious complication of
antibiotic therapy can be the onset of colitis due to Clostridium
difficile. This condition can be ractory to subsequent antibiotic
treatment, resulting in ongoing recurrences. A few small studies have
suggested that certain probiotics can prevent relapses of C. difficile
colitis. A recent metaanalysis concluded that the probiotic yeast,
Saccharomyces boulardii was the most effective probiotic treatment.
Another common form of diarrhoea
is experienced by travellers. Studies evaluating the effect of probiotics
on travellers diarrhoea are equivocal. There is a need for further
research in this area for more convincing findings. One metaanalysis
of 12 studies on travellers diarrhoea concluded that certain
probiotic products may offer a safe and effective method to prevent
travellers diarrhoea with no indication of serious adverse events.
Elevated Blood Cholesterol
Cholesterol is essential for many functions in the human body. It
acts as a precursor to certain hormones and vitamins and it is a component
of cell membranes and nerve cells. However, elevated levels of total
blood cholesterol or other blood lipids are considered risk factors
for developing coronary heart disease. Although humans synthesize
cholesterol to maintain minimum levels for biological functioning,
diet also is known to play a role in serum cholesterol levels. The
extent of influence varies significantly from person to person. Probiotic
cultures have been evaluated for their effect on serum cholesterol
levels. Clinical studies on the effect of lowering cholesterol or
low-density lipid levels in humans have not been conclusive. There
have been some human studies that suggest that blood cholesterol levels
can be reduced by consumption of probiotic-containing dairy foods
by people with elevated blood cholesterol, but in general the evidence
is not overwhelming. It is likely that some strains may demonstrate
this property while others do not, or that only subsets of people
with elevated cholesterol respond.
Helicobacter pylori is a bacterium which colonizes the stomach and
can cause gastric ulcers and gastric cancer. The effect of probiotics
on H. pylori has been studied. Mechanistic studies in laboratory assays
or in animal models have shown that antibacterial substances including
(but not limited to) organic acids produced by some lactobacilli inhibit
the growth and survival of this pathogen. When tested in humans, results
are mixed. Results in humans suggest that some probiotic strains or
milk fermented with a probiotic strain can reduce metabolic activity
or colonization by H. pylori but eradication has not been achieved.
Probiotics have also been used to manage side effects of triple antibiotic
therapy used to treat H. pylori infections. In these studies, the
use of probiotics decreases the side effects of antibiotics, improves
patient compliance with taking the prescribed therapy, and increases
the rate at which H. pylori is eradicated..
About 50-60 million people in United States are estimated to have
hypertension, or elevated blood pressure. Antihypertensive effects
have been documented in animal models and in mildly hypertensive adults
for three compounds derived from the growth of certain lactobacilli
: 1) fermented milk containing two tripeptides derived from the proteolytic
action of L. helveticus on casein in milk ; 2) bacterial cell wall
components from cell extracts of lactobacilli; and 3) fermented milk
containing fermentation-derived gamma-amino butyric acid. Systolic
blood pressure was decreased on the order of 10-20 mm Hg. These results
suggest that consumption of certain lactobacilli, or products made
from them, may reduce blood pressure in mildly hypertensive people.
Viability of the Lactobacillus is not required for the effect.
Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is a functional bowel disorder that
can be characterized by symptoms of abdominal pain, cramps, gas, bloating,
diarrhoea and constipation. Surveys estimate the prevalence rate ranging
from 10-20% of the adult population and the condition is diagnosed
3 times more often in women than men. Only a few controlled studies
have been conducted evaluating probiotics and IBS. Some symptom relief
(primarily from diarrhoea or abdominal pain or bloating) has been
reported in studies published to date.
Inflammatory Bowel Disease
Inflammatory bowel diseases such as ulcerative colitis and Crohn's
disease, are serious intestinal diseases that can lead to the surgical
removal of the colon. The cause of these diseases is not known but
it has been hypothesized that an intolerance to the normal microbiota
in the gut leads to inflammation and resulting pathology. Efforts
to identify a single microbe associated with the disease has failed,
leading some to suggest that it is a pathogenic microbial community,
not a single microbe, that is responsible for IBD. The role of gut
flora in the progression of these diseases has led some researchers
to study the impact certain probiotic bacteria might have on maintaining
the state of reduced inflammation that occurs during remission stages
of the diseases. Several controlled, clinical trials have shown that
high levels of certain probiotic strains can extend the disease-free
remission period. Studies also have documented this effect on remission
of pouchitis. But not all studies have shown benefits.
Immune System Modulation
The immune system defends against microbial pathogens that have entered
our bodies. The immune system is extremely complex, involving both
cell-based and antibody-based responses to potential infectious agents.
Immunodeficiency can result from certain diseases (e.g., cancer, AIDS,
leukemia) or, to a lesser extent, from more normal conditions such
as old age, pregnancy, or stress. Autoimmune diseases (e.g., allergies,
rheumatoid arthritis, inflammatory bowel diseases) also can occur
due to misdirected immune system activity.
Probiotic cultures have been
shown in a variety of test systems to stimulate certain cellular,
biochemical and antibody functions of the immune system . Animal and
some human studies have shown an effect of yogurt or lactic acid bacteria
on enhancing levels of certain immunoreactive cells (e.g. macrophages,
lymphocytes) or on regulation of immune factors (cytokines, immunoglobulins,
interferon). In addition, some studies have shown improved survival
of pathogen-infected laboratory animals consuming probiotic cultures
as compared to animals consuming a control diet. Results accumulated
so far suggest that probiotics may provide an additional tool to help
your body protect itself.
An exciting area of research
has been documenting the ability of certain probiotic bacteria to
modulate immune dysregulation. Studies have shown that probiotics
are effective in decreasing the development of allergy and relapse
of inflammatory bowel disease.
High levels of oxalate in the urine is a risk factor for the development
of kidney stones. Utilization of oxalate by intestinal microbes limits
its absorption. A probiotic preparation that contained bacteria that
were able to degrade oxalate in vitro was shown to reduce oxalate
fecal excretion in six patients. These results suggest that manipulation
of the gut flora with the right probiotic bacteria may have a positive
impact on gastrointestinal tract oxalate levels and may decrease oxalate
absorption . These results are intriguing, but preliminary.
The inability of adults to digest lactose, or milk sugar, is prevalent
worldwide. People of northern European descent are unique in retaining
the ability to produce the lactose-digesting enzyme, lactase, into
adulthood. Consumption of lactose by those lacking adequate levels
of lactase produced in the small intestine can result in symptoms
of diarrhoea, bloating, abdominal pain and flatulence. These symptoms
are due to undigested lactose reaching the large intestine and being
fermented by the colonic microbes. These microbes can produce gases
and products that lead to watery stool.
The inability to comfortably
consume dairy products not only limits people's freedom to choose
preferred foods, but also potentially compromises calcium intake,
threatening bone health. It has been documented scientifically that
many lactose intolerant individuals are better able to consume fermented
dairy products, such as yogurt, with fewer symptoms than the same
amount of unfermented milk, even though yogurt contains about the
same amount of lactose as milk . Yogurt was found to aid digestion
of lactose because the lactic acid bacteria used to make yogurt deliver
lactase to the small intestine, where it breaks down the lactose before
it reaches the colon. In addition to yogurt starter bacteria, L. acidophilus
and bifidobacteria have been shown by several studies to improve digestion
of lactose, although generally to a lesser extent than the yogurt
starter cultures, Lactobacillus bulgaricus and Streptococcus thermophilus.
Obesity and metabolic syndrome
Perhaps one of the most fascinating areas of research on the gut microbiota
and health is how colonizing microbes might impact the onset of obesity
and metabolic syndrome. Disrupted patterns of colonization are associated,
for example, with obesity and diabetes, but what is not clear is if
strategies to alter the disrupted microbiota can impact the course
of these conditions. Microbes may directly impact energy harvest from
foods due to bacterial metabolism in the gut. But microbes or their
products may also act as metabolic regulators through interacting
with host cellular targets. Some experimental animal model studies
have looked at the effect of probiotics on obesity. In humans, a strain
of Lactobacillus gasseri was shown to decrease fat mass (visceral
and subcutaneous) and BMI in diabetic patients . In another human
study, a probiotic preserved insulin sensitivity. This is a field
of research with promise, but still in its infancy.
Necrotizing enterocolitis (NEC) is a gastrointestinal disease that
mostly affects premature infants. It is characterized by infection
and inflammation leading to death of tissue of the large intestine.
Probiotic supplementation may reduce the risk of NEC in preterm infants.
A recent review of studies targeting efficacy and safety of probiotics
for infants at risk for developing NEC was conducted . Taken together,
studies suggest that probiotics lower the risk of mortality in preterm
infants, but additional studies on best strains for this application,
short- and long-term safety and required dose must be conducted.
One study conducted with children aged 3-6 years in day care centers
evaluated the ability of milk containing L. rhamnosus GG to reduce
the incidence of dental caries . Only a subset of the study group,
children aged 3-4 years, showed any statistically significant reduction
in dental caries incidence. Other studies have documented that other
probiotics, e.g., L. reuteri or Bifidobacterium animalis DN173 010,
can reduce salivary levels of cariogenic Streptococcus mutans in young
Small Bowel Bacterial Overgrowth
Under certain conditions (production of low stomach acid, kidney dialysis
and others), microbial populations in the small intestine can increase
beyond normal levels. This is termed small bowel bacterial overgrowth.
The misplaced microbes can produce byproducts from their growth that
can be toxic. Researchers have found that feeding high levels of certain
probiotic strains can control the toxic effects of these microbes
. This is another example of the ability of probiotic strains fed
in high numbers to modulate the activity of other intestinal bacteria.
The vagina and its microbiota form a finely balanced ecosystem. Disruption
of this ecosystem can lead to a microbiological imbalance and symptoms
of vaginosis. Vaginosis used to be considered a mere annoyance, but
now is being examined for a role in serious conditions including pelvic
inflammatory disease, pregnancy-related complications (such as low
birth weight babies), and increased susceptibility to AIDS infection.
Vaginosis can be caused by several different organisms, and in many
cases, the causative agent may not be identified. What is known is
that lactobacilli predominate in the healthy vagina, and a lack of
lactobacilli is a risk factor for vaginosis. The lactobacilli are
thought to maintain a favorable vaginal pH in the acidic range and
to inhibit pathogens, possibly through the production of hydrogen
peroxide and other antimicrobial factors. The most conclusive human
studies to date on the impact of lactobacilli on bacterial vaginosis
showed that Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri
RC-14 administered in milk could pass through the intestine, ascend
to the vagina and restore a normal lactobacilli microbiota in women
prone to infections . These strains were delivered in yogurt to African
women with bacterial vaginosis and shown to improve therapeutic outcome
. These studies have provided the best evidence to date for successful
probiotic intervention to improve vaginal health. Some other recent
studies have not shown positive results , highlighting the importance
of use of effective strains and delivery systems.
scientific probiotic study referrence page is HERE