Probiotic means pro-bios, or for life. This is the opposite of antibiotic which means against life.
Our immune system, when healthy, is enormously helped by the presence of an army of trillions of friendly bacteria which line the mucus layer of a healthy intestine. It is said that 80% of our immune system is in the intestine. In a sense, these bacteria provide immunity we don't have to work for - they work for us. We just need to provide them with the right environment to keep them nourished.
Promoting probiotic bacterial health includes not eating to much food which promotes their yeast adversaries like Candida. Candida, and other adversarial fungi are promoted by certain 
foods including excess sweets, fungus foods like mushrooms, yeasted foods like beer and wine. We also hinder probiotic bacteria when we take non steroidal anti-inflammatories like acetaminophen, ibuprofen and ASA. These drugs thin the mucus layer and make it more difficult for the probiotics to survive.
foods including excess sweets, fungus foods like mushrooms, yeasted foods like beer and wine. We also hinder probiotic bacteria when we take non steroidal anti-inflammatories like acetaminophen, ibuprofen and ASA. These drugs thin the mucus layer and make it more difficult for the probiotics to survive.
The diagram to the right illustrates the probiotic layer (green) living on the surface of a layer of mucus (turquoise). The arrows indicate their ability to repel yeasts, bacteria and fungi.
We can 'poison' probiotics with chlorine in drinking water which reduces thier numbers. Fast and certain probiotic death comes from a course of antibiotics. Slow death can come from low level antibiotics which may be found insome food products.
Low levels of antibiotics may be present in meats which come from animals, fowl or fish which have been raised using food laced with antibiotics. Poultry and pork raised in commercial units, when the creatures are packed together, are prone to bacterial illnesses. Farmers add antibiotics to promote rapid weight gain and reduce the chance of infection which can kill large numbers of animals when they are packed so closely together. In some cases, antibiotics are added to the ice water in which fish are transported to market in order to "preserve freshness". Food raised organically does not have these risks.
Acidophilus actually looks like this. 
This friendly bacteria has many helpful functions and lives as the dominant species in the small intestine. Here, it creates an acidic microenvironment next to the absorption cells, promoting iron absorption. One of the causes of anemiacan be damage to this acid layer as inceliac disease. Many people are anemic and correcting this lack by taking acidophilus daily can help promote iron absorption. A good acidophilus can be obtained directly from a reputable company. Click here for more information.
This friendly bacteria has many helpful functions and lives as the dominant species in the small intestine. Here, it creates an acidic microenvironment next to the absorption cells, promoting iron absorption. One of the causes of anemiacan be damage to this acid layer as inceliac disease. Many people are anemic and correcting this lack by taking acidophilus daily can help promote iron absorption. A good acidophilus can be obtained directly from a reputable company. Click here for more information.
When acidophilus is in a healthy condition, one may observe projections from the tips of the bacteria - acidophilus buds. These are the beginning of new acidophilus cells which signifies the health of the bacteria.
The following drawing shows an illustration of the healthy intestinal villi. These finger-like projections are how we absorb our food. Probiotic bacteria stand on guard to protect us from potential bacterial, viral and yeast invaders. The probiotics are illustrated in green.
The healthy large intestine has another dominant species, Bifido bacterium. This family of bacteria thrive on the soluble fibre in your diet - the type of fibre which comes from most fruits and grains.Bifido bacteria take this fibre and break it down, creating food (butyrate) for the large intestine. Butyrates are fatty acids which help promote healthy peristalsis in the colon and facilitate healthy easy bowel movements. Please click here for more information on a good Bifidus
Probiotics as Immune Enhancers
It has been widely accepted in the medical community that probiotics have a beneficial effect on immunity. It was thought that this benefit was due to the effect of the live bacteria. A rather interesting recent study showed enhancement of immune function when lab animals were fed killed probiotics. It seems that there is something about probiotics that are protective even if they are not active. This does not mean however that it is not preferable to have fresh live bacteria as supplements. Many strains of probiotics are very sensitive to heat and begin to die when kept out of refrigeration.
Probiotics and Anemia
If you are one of the people who have been told they are anemicand who take iron without much benefit, the following explanation may make sense.
Iron is absorbed in the upper small intestine, the jejunum. The cells which take in iron can be partially blocked by a number of substances. Phytates from wheat and other grains as well as calcium are two important ones. Oxalates from rhubarb or spinach and phosphates from soft drinks can also have a negative impact on iron absorption.
In order to take iron into the cells, it must be in solution. It goes into solution in an acidic environment - rather like iron being rusted by acid rain. In the intestine, the pancreas pours a very alkaline fluid into the upper small intestine making the whole contents alkaline because the digestive enzymes work best in an alkaline state. This creates a problem for mineral absorption. That's where probiotics come in.
Acidophilus is the dominant probiotic in the small intestine. In health, it thrives on the mucus layer where it creates an acidic microenvironment which makes iron and other minerals more absorbable. I have seen many examples if people who, when they add probiotics to their daily regimen and eliminate wheat, have an improvement in their iron levels.
Which Probiotic Works Best?
No one is absolutely sure of the answer. For years I have been advising the use of L. Acidophilus DDS strain and have been very pleased with the results. Recent medical trials have been done withL. acidophilus GG with marked benefits being shown. It may be that this strain is better. Certainly, both are heat sensitive and should be purchased either from the refrigerated section of a store orpurchased from a company which has them fresh and ships them quickly to you.
Bifidobacterium bifidus, is the dominant strain in the lower intestine where it plays an important role. It feed primarily on dietary fibres which are soluble - those found in the husks of grains, fruit and vegetables. Bifidus takes this fibre, digests it and produces butyrates. These compounds, in turn, are absorbed by the cells of the colon which uses the butyrate to help with peristalsis - the natural rhythmic contraction of the bowel which when we are healthy makes for smooth, easy bowel movements.
Saccharomyces boulardii
This highly effective supplement is actually a live yeast. It differs from harmful yeasts in that it takes an active role in protecting the intestine without taking up permanent residence. In this role it is perfect for use when you take an antibiotic. Antibiotics kill bacteria but, because they are created from yeast like substances, they cannot kill Saccharomyces. So when you take Saccharomyces during the course of the antibiotic (and you can take them at the same time), you help to prevent the growth of harmful yeasts like Candidaand harmful bacteria like C. dificile.
After you finish the antibiotic you should take probiotic bacteria like acidophilus and bifidus for a time to re-establish healthy bowel bacteria. This advice applies to people of all ages except those with severe inflammatory bowel disease or suppressed immune function when consultation with your physician is important. Saccharomycesis available in most health food stores, made by different companies, and in almost all pharmacies as Florastor™
Probiotics and Infants
I think that it is important to help the digestion and immune system of newborns with a strain of probiotic adapted for their intestine.Bifidobacterium infantis is the strain which is easily and safely taken by infants whether breast or bottle fed.
I generally advise mothers of newborns to keep a small amount ofBifidus powder in a saucer in the area where they generally feed the infant and at every feeding moisten their finger with a little milk or their own saliva and dip their finger in the powder and put it in the infant's mouth.
Infants who receive this blessing generally have fewer episodes of colic and fewer diaper rashes, usually related to Candidaovergrowth.
Moms who give their infants Bifidobacteria infantis have, in my experience, the benefit of happier children and less of a chance of getting mastitis. This painful and dangerous condition is, in my experience, usually caused by infants getting Candida growing in their mouth and transmitting it to the nipple which then cracks, becomes inflamed, and allows bacteria to enter.
Generally it is best to transition infants from Bifidus to the adult strains of acidophilus and bifidus when they begin to eat adult foods - at about six months.
There have been recent reports of newborn infants who are either very premature or immunocompromised and who received probiotics and became ill. I believe these are special circumstances and that it is generally a good idea and quite safe to give newbornsBifidobacterium infantis however if you have concerns about this approach, please check with your physician.
When to Take Probiotics?
Anytime - all the time! Clinicians have differing opinions about when to take probiotics. I don't think it makes much difference. In general, probiotics can withstand the acid environment of the stomach so with meals is OK. Between meals the acid level is lower so perhaps there is an argument in favor of this timing. But it is better to take them than to forget.
Antibiotics and Probiotics
Antibiotics (in greek = against life) generally kill all, or most of, the beneficial bacteria in the intestine.
This illustration demonstrates the situation in which antibiotics have largely killed off the probiotic bacteria (in green). The tips of the villi are exposed - a situation created by using NSAIDS which decrease mucus production. This leaves the intestine susceptible to invasion by yeasts and can lead to a condition called leaky gut.
During a course of antibiotics and for an extended period afterward it is important to protect the intestine by taking probiotics . Don't take the probiotics with the antibiotic - they just get killed. Take them in between.
An alternate approach which makes sense particularly if you have had a bad Candida overgrowth after having previously taken an antibiotic, is to take a protective supplement in the form of yeast -Saccharomyces boulardii. Because it is a yeast, it is not killed by the antibiotic. In the intestine, it displaces Candida and other harmful bacteria. Saccharomyces has the benefit of not taking permanent root in the intestine. By contrast, we want probiotics like acidophilus and bifidus to be permanent residents.
Clostridium dificile is a bacterium which can be deadly in debilitated people and can otherwise be quite harmful. It can cause a fever, severe diarrhea, cramping and abdominal pain. It frequently occurs in hospitalized patients who receive antibiotics, Recent studies have demonstrated that pre treating patients with Saccharomycesreduces the likelihood of them getting C. Dificile. If they do contractC. dificile, taking Saccharomyces speeds the healing which is usually treated with oral metronidazol (a form of antibiotic). After several days, or up to one or two weeks, of taking Saccharomyces, you should return to taking acidophilus and bifidus, which need to be continued for weeks and perhaps longer.
Prebiotics
These supplements are taken from food sources and are often found in products which include them with the claim that they will improve survival of the probiotic in the gut. These products are mostly taken from vegetable sources and are soluble fibre. Jerusalem artichoke fibre is often included as it is thought to promote survival of Bifidusin the colon. Certain harmful bacteria, Klebsiella sp. can also use these compounds for their own growth so some experts advise caution with their overuse.
One company has taken the step of micro blending high quality probiotics with blue green algae as a form of pre biotic- products which I endorse because I have found them to be particularly effective.
Maintaining our intestinal probiotics may take a conscious effort. Cutting down in the refined sugars, alcohol and refined grains helps. Drinking non-chlorinated water is also of benefit. If you are in intestinal trouble, please turn to the Candida diet. Please also read the section on digestive immunity.
http://greaterimmunity.com/Files/probiotics.html
From wiki
According to one definition offered by an expert committee convened by the Food and Agriculture Organization of the United Nations and the World Health Organization, probiotics are live microorganisms that may confer a health benefit on the host.[1] Alternative expert review indicates there is insufficient scientific evidence for supplemental probiotics having a benefit.[2]
Lactic acid bacteria (LAB) and bifidobacteria are the most common types of microbes used as probiotics, but certain yeasts and bacilli may also be used. Probiotics are commonly consumed as part of fermented foods with specially added active live cultures, such as in yogurt, soy yogurt, or as dietary supplements. Probiotics are also delivered in fecal transplants, in which stool from a healthy donor is delivered like a suppository to an infected patient.[3]
Etymologically, the term appears to be a composite of the Latin preposition pro ("for") and the Greek adjective βιωτικός (biotic), the latter deriving from the noun βίος (bios, "life").[4]
Probiotics may beneficially affect the host by augmenting its intestinal microbial population beyond the amount already existing, thus possibly inhibiting pathogens.[citation needed][5] Studies are examining whether probiotics affect mechanisms of intestinal inflammation,[6] diarrhea,[7] urogenital infections[8] or allergies.[9] Through 2012, however, in all cases proposed as health claims to the European Food Safety Authority, the scientific evidence remains insufficient to prove a cause and effect relationship between consumption of probiotic products and any health benefit.[2]
When a person takes antibiotics, both the harmful bacteria and the beneficial bacteria are killed. A reduction of beneficial bacteria can lead to digestive problems, such as diarrhea, yeast infections and urinary tract infections. The possibility that supplemental probiotics affect such digestive issues is unknown, and remains under study.[10]
History
The original observation of the positive role played by certain bacteria was first introduced by Russian scientist and Nobel laureate Élie Metchnikoff, who in the beginning of the 20th century suggested that it would be possible to modify the gut flora and to replace harmful microbes with useful microbes.[5] Metchnikoff, at that time a professor at the Pasteur Institute in Paris, proposed the hypothesis that the aging process results from the activity of putrefactive (proteolytic) microbes producing toxic substances in the large bowel. Proteolytic bacteria such as clostridia, which are part of the normal gut flora, produce toxic substances including phenols, indols and ammonia from the digestion of proteins. According to Metchnikoff these compounds were responsible for what he called "intestinal auto-intoxication", which caused the physical changes associated with old age.[citation needed]
It was at that time known that milk fermented with lactic-acid bacteria inhibits the growth of proteolytic bacteria because of the low pH produced by the fermentation of lactose. Metchnikoff had also observed that certain rural populations in Europe, for example in Bulgaria and the Russian steppes who lived largely on milk fermented by lactic-acid bacteria were exceptionally long lived. Based on these facts, Metchnikoff proposed that consumption of fermented milk would "seed" the intestine with harmless lactic-acid bacteria and decrease the intestinal pH and that this would suppress the growth of proteolytic bacteria. Metchnikoff himself introduced in his diet sour milk fermented with the bacteria he called "Bulgarian Bacillus" and found his health benefited. Friends in Paris soon followed his example and physicians began prescribing the sour milk diet for their patients.[11]
Bifidobacteria were first isolated from a breast-fed infant by Henry Tissier who also worked at the Pasteur Institute. The isolated bacterium named Bacillus bifidus communis[12] was later renamed to the genus Bifidobacterium. Tissier found that bifidobacteria are dominant in the gut flora of breast-fed babies and he observed clinical benefits from treating diarrhea in infants with bifidobacteria. The claimed effect was bifidobacterial displacement of proteolytic bacteria causing the disease.[citation needed]
During an outbreak of shigellosis in 1917, German professor Alfred Nissle isolated a strain of Escherichia coli from the feces of a soldier who was not affected by the disease.[13] Methods of treating infectious diseases were needed at that time when antibioticswere not yet available, and Nissle used the Escherichia coli Nissle 1917 strain in acute gastrointestinal infectious salmonellosis and shigellosis.[citation needed]
In 1920, Rettger demonstrated that Metchnikoff's "Bulgarian Bacillus", later called Lactobacillus delbrueckii subsp. bulgaricus, could not live in the human intestine,[14] and the fermented food phenomenon petered out. Metchnikoff's theory was disputable (at this stage), and people doubted his theory of longevity.[citation needed]
After Metchnikoff's death in 1916, the centre of activity moved to the United States. It was reasoned that bacteria originating from the gut were more likely to produce the desired effect in the gut, and in 1935 certain strains of Lactobacillus acidophilus were found to be very active when implanted in the human digestive tract.[15] Trials were carried out using this organism, and encouraging results were obtained especially in the relief of chronic constipation.[citation needed]
The term "probiotics" was first introduced in 1953 by Werner Kollath (see Hamilton-Miller et al. 2003). Contrasting antibiotics, probiotics were defined as microbially derived factors that stimulate the growth of other microorganisms. In 1989, Roy Fuller suggested a definition of probiotics that has been widely used: "A live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance".[16] Fuller's definition emphasizes the requirement of viability for probiotics and introduces the aspect of a beneficial effect on the host.[citation needed]
In the following decades, intestinal lactic acid bacterial species with alleged health beneficial properties have been introduced as probiotics, including Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus johnsonii.[17]
[edit]Preliminary research and potential effects
Experiments into the potential health effects of supplemental probiotics include the molecular biology and genomics of Lactobacillus in immune function, cancer, and antibiotic-associated diarrhea, travellers' diarrhea, pediatric diarrhea, inflammatory bowel disease and irritable bowel syndrome.[18] Testing of a probiotic usually applies to a specific strain under study.[19]
In the overview below, only preliminary evidence exists for the health claims stated. Few of the strains have been sufficiently developed in basic and clinical research to warrant application for health claim status to a regulatory agency such as the Food and Drug Administration or European Food Safety Authority, but so far no single health effect has been proven to warrant a health claim[20]
[edit]Diarrhea
Some probiotics have been shown in preliminary research to possibly treat various forms of gastroenteritis.[21] They might reduce both the duration of illness and the frequency of stools.[22]
- Antibiotic-associated
Antibiotic-associated diarrhea (AAD) results from an imbalance in the colonic microbiota caused by antibiotic therapy. Microbiota alteration changes carbohydrate metabolism with decreased short-chain fatty acid absorption and an osmotic diarrhea as a result. Another consequence of antibiotic therapy leading to diarrhea is overgrowth of potentially pathogenic organisms such as Clostridium difficile.[citation needed] Probiotic treatment might reduce the incidence and severity of AAD as indicated in several meta-analyses.[23][24][25][26][27][28] For example, treatment with probiotic formulations including Lactobacillus rhamnosus may reduce the risk of antibiotic-associated diarrhea, improve stool consistency during antibiotic therapy, and enhance the immune response after vaccination.[29] However, further documentation of these findings through randomized,double blind, placebo-controlled trials are required to confirm specific effects and attain regulatory approval, which currently does not exist.
Potential efficacy of probiotic AAD prevention is dependent on the probiotic strain(s) used and on the dosage.[30][31] Up to a 50% reduction of AAD occurrence has been found in preliminary studies.[28] No side-effects have been reported in any of these studies. Caution should, however, be exercised when administering probiotic supplements to immunocompromised individuals or patients who have a compromised intestinal barrier.[citation needed]
[edit]Lactose intolerance
Ingestion of certain active strains may help lactose intolerant individuals tolerate more lactose than they would otherwise have tolerated.[32]
[edit]Colon cancer
In laboratory investigations, some strains of LAB (Lactobacillus delbrueckii subsp. bulgaricus) have demonstrated anti-mutagenic effects thought to be due to their ability to bind with heterocyclic amines, which are carcinogenic substances formed in cooked meat.[33] Animal studies have demonstrated that some LAB have evidence for acting against colon cancer in rodents, though human data are inconclusive.[34] Some human trials hypothesize that the strains tested may exert anti-carcinogenic effects by decreasing the activity of an enzyme called β-glucuronidase[34](which can generate carcinogens in the digestive system). Lower rates of colon cancer among higher consumers of fermented dairy products have been observed in one population study, but confirmation of such an effect does not exist.[32]
[edit]Cholesterol
Animal studies have demonstrated the efficacy of some strains of LAB at being able to lower serum cholesterol levels, presumably by breaking down bile in the gut, thus inhibiting its reabsorption (which enters the blood as cholesterol).[32]
A meta-analysis that included five double blind trials examining the short term (2-8weeks) effects of a yogurt with probiotic strains on serum cholesterol levels found a minor change of 8.5 mg/dL (0.22 mmol/L) (~4% decrease) in total cholesterol concentration, and a decrease of 7.7 mg/dL (0.2 mmol/L) (~5% decrease) in serum LDL concentration.[35]
A slightly longer study evaluating the effect of a yogurt with probiotic strains on twenty-nine subjects over six months found no statistically significant differences in total serum cholesterol or LDL values. However, the study did note a significant increase in serum HDL from, 50 mg/dL (1.28 mmol/L) to 62 mg/dL (1.6 mmol/L) following treatment. This corresponds to a possible improvement of LDL/HDL ratio.[36]
Studies specifically on hyper-lipidemic subjects are still needed.
[edit]Blood pressure
Although not a confirmed effect, some studies have indicated that consumption of milk fermented with various strains of LAB may result in modest reductions in blood pressure, an effect possibly related to the ACE inhibitor-like peptides produced during fermentation.[32]
[edit]Immune function and infections
Some strains of LAB may affect pathogens by means of competitive inhibition (i.e., by competing for growth) and there is evidence to suggest that they may improve immune function by increasing the number of IgA-producing plasma cells, increasing or improving phagocytosis as well as increasing the proportion of T lymphocytes and Natural Killer cells.[37][38] Clinical trials have demonstrated that probiotics may decrease the incidence of respiratory tract infections[39] and dental caries in children.[40] LAB products might aid in the treatment of acute diarrhea, and possibly affect rotavirus infections in children and travelers' diarrhea in adults,[37][38] but no products are approved for such indications.
A 2010 study suggested that probiotics, by introducing "good" bacteria into the gut, may help maintain immune system activity, which in turn helps the body react more quickly to new infections. Antibiotics seem to reduce immune system activity as a result of killing off the normal gut bacteria.[41]
[edit]Helicobacter pylori
Some strains of LAB may affect Helicobacter pylori infections (which may cause peptic ulcers) in adults when used in combination with standard medical treatments, but there is no standard in medical practice or regulatory approval for such treatment.[42]
[edit]Inflammation
Some strains of LAB may modulate inflammatory and hypersensitivity responses, an observation thought to be at least in part due to the regulation of cytokine function.[37] Clinical studies suggest that they can prevent reoccurrences of inflammatory bowel disease in adults,[37] as well as improve milk allergies.[43] They are not effective for treating eczema, a persistent skin inflammation.[44] How probiotics may influence the immune system remains unclear, but a potential mechanism under research concerns the response of T lymphocytes to pro-inflammatory stimuli.[45]
[edit]Bacterial growth under stress
In a study done to see the effects of stress on intestinal flora, rats that were fed probiotics had little occurrence of harmful bacteria latched onto their intestines compared to rats that were fed sterile water.[46]
[edit]Irritable bowel syndrome and colitis
In one study, a commercial strain of Bifidobacterium infantis improved some symptoms of irritable bowel syndrome in women.[47] A separate small study showed that a strain of Lactobacillus plantarum may also be effective in reducing IBS symptoms.[48] A study focused on Bifidobacterium animalis showed a reduction in discomfort and bloating in individuals with constipation-predominant IBS, as well as helping to normalize stool frequency in said individuals.[49] For maintenance of remission of ulcerative colitis, Mutaflor (E.coli Nissle 1917) randomized clinical studies showed equivalence of Mutaflor and mesalazine (5-ASAs).[50]
[edit]Other
A study in 2004 testing the immune system of students given either milk or Actimel over a 6-week exam period (3 weeks of studying, 3 weeks of exams) tested 19 different biomarkers. Of these 19 biomarkers, only 2 were shown to be different between the two groups, increased production oflymphocytes, and increased production of CD56 cells. The tests were not blind and show that certain probiotic strains may have no overall effect on the immune system or on its ability.[51]
A 2007 study at University College Cork in Ireland showed that a diet including milk fermented with Lactobacillus bacteria prevented Salmonella infection in pigs.[52]
A 2007 preliminary study at Imperial College London showed that a commercially available probiotic drink containing Lactobacillus casei DN-114001 and yoghurt bacteria might reduce the incidence of antibiotic-associated diarrhea and C difficile-associated diarrhea.[53]
The efficacy and safety of a daily dose of Lactobacillus acidophilus CL1285 in affecting AAD was demonstrated in one preliminary study of hospitalized patients.[54]
A 2011 study found that mice given Lactobacillus rhamnosus JB-1 showed lower levels of stress and anxiety than controls.[55]
Current research is focusing on the molecular biology and genomics of Lactobacillus strains and bifidobacteria. The application of modern whole genome approaches is providing insights into bifidobacterial evolution, while also revealing genetic functions that may explain their presence in the particular ecological environment of the gastrointestinal tract.[56][57]
[edit]Factors affecting viability in foods
 | This section does not cite any references or sources. (June 2011) |
Some factors, both intrinsic and extrinsic, may influence the survival of probiotics in food, and so have to be considered in all stages of probiotic food manufacturing.
- physiological state of the added probiotic in the food
- physicochemical conditions of food processing
- physical conditions of product storage, like temperature
- chemical composition of the product, such as content of nutrients, oxygen or pH
- interactions with other product components, that can be inhibitory or protective
[edit]Physiological state
The physiological state of bacteria when prepared and remaining in a product itself are important factors for survival of the probiotics.[citation needed] Dryness in a food product keeps the bacteria in a relatively quiescent state during storage, while a wet product establishes potentially active metabolism. Temperature affects shelf life of the bacteria, with low temperature providing conditions for possible long term survival.
Bacteria can respond to stressful environments by the induction of various stress tolerance mechanisms. One of them is the induction of stress proteins by exposure of the cells to sublethal stresses so they can condition probiotics to better tolerate environmental stresses in food production, storage, and gastrointestinal transit.[citation needed] Different probiotic strains have their own intrinsic tolerances to environmental conditions,[citation needed] including how the culture is prepared, and some cross-protection can be observed, providing protection against other stresses by the exposure to only one stress.[citation needed] Stress responses can be explored to make probiotic strains more resilient and likely to survive in food matrices, with significant industrial importance.
[edit]Temperature
The temperature at which probiotic organisms grow is an important factor in food applications where fermentation is required, is also a critical factor influencing probiotic survival during manufacture and storage. As it is told above, the lower the temperature the more stable probiotic viability in the food product will be. During processing, temperatures over 45–50°C (113-131°F) will be detrimental to probiotic survival, this means that the higher the temperature, the shorter the time period of exposure required to severely decrease the numbers of viable bacteria, ranging from hours or minutes at 45–55°C (113-131°F) to seconds at higher temperatures. Therefore it is obvious that probiotics should be added downstream of heating/cooking/pasteurization processes in food manufacture to avoid the high temperatures. Elevated temperature also has a detrimental effect on stability during the product process of shipping and storage. Again, the cooler a product can be maintained, the better probiotic survival will be, like in vegetative probiotic cells in liquid products, where refrigerated storage is usually essential. If the product is dried, the bacteria will be in a quiescent state, so acceptable probiotic viability can be maintained in dry products stored at ambient temperatures for 12 months or more. Producing and maintaining low water activities in the foods is the key to maintaining probiotic viability during nonrefrigerated storage because there is a remarkable interaction between temperature and water activity.
[edit]pH
Some bacteria like Lactobacilli and bifidobacteria can tolerate lower pH levels because they produce organic acid and products from carbohydrate metabolism. Indeed, numerous in vitro and in vivo studies have demonstrated that in gastric transit where the cells are exposed to low pH values and with a time of exposure relatively short, some probiotic organisms can survive. In fermented milks and yogurts with pH values between 3.7 and 4.3. lactobacilli are able to grow and survive, while Bifidobacteria tend to be less acid tolerant, with most species surviving poorly in fermented products at pH levels below 4.6. B. animales subsp. lactis is most commonly used in acidic foods because is more acid tolerant than human intestinal species, and B. thermoacidophilum, is even more tolerant to low pH (and heat), but has not yet been characterized thoroughly for probiotic traits and is not used commercially.
Regarding to fruit juices (pH 3.5–4.5) commercially successful products have been produced, such as Gefilus (Valio Ltd, Finland), which contains Lactobacillus rhamnosus GG. The viability at low pH can be improved with carriers such as dietary fibers. Survival of lactobacilli in low pHs has also been enhanced in the presence of metabolizable sugars, that allow cell membrane proton pumps to operate and prevent lowering of intracellular pH. This can improve survival during gastric transit, but may not be applicable to improving probiotic survival over the time stages of shelf-storage.
[edit]Water activity
For quiescent probiotic bacteria, water activity is a crucial determinant of survival in food products during storage. The higher moisture levels and water activity, the lower survival of probiotics. There is a substantial interaction between water activity and temperature with respect to their impact on the survival of quiescent probiotics. As the storage temperature is increased, the detrimental impact of moisture is magnified. Here, the osmotic stresses appear to play a role, with the presence of smaller molecules resulting in poorer bacterial survival, although the exact cell death mechanisms have not been elucidated yet.
There may be technological limitations to reducing water activity to low levels for improving survival. These include the energy costs of drying, adverse impacts on the taste of foods and difficulties in wetting and dispersing powders. Moisture barrier packaging may be applied to prevent the development of moisture from the environment during storage. Maintaining probiotic viability in moderate water activity foods (0.4–0.7) is a great challenge and solutions such as microencapsulation or incorporation of probiotics into fat phases of products can provide improved survival.
[edit]Oxygen
Both bifidobacteria and lactobacilli are considered strict anaerobes and oxygen can be detrimental to its growth and survival. However, the degree of oxygen sensitivity varies considerably between different species and strains, for example, lactobacilli, which are mostly microaerophilic, are more tolerant of oxygen than bifidobacteria, to the point where oxygen levels are not an important consideration in maintaining the survival of lactobacilli. Most probiotic bifidobacteria do not grow well in the presence of oxygen, although, many bifidobacteria have enzymatic mechanisms to limit the oxygen toxicity.
For oxygen sensitive strains, some strategies can be used to prevent oxygen toxicity in food products. Antioxidant ingredients have been shown to improve probiotic survival, as well as the use of oxygen barrier or modified-atmosphere packaging. Therefor, it is advisable to minimize processes that are highly aerating, particularly when using bifidobacteria.
[edit]Toxicity of ingredients
Interactions between probiotics and other ingredients could happen and those interactions can be protective, neutral, or detrimental to probiotic stability. Obviously, the inclusion of antimicrobial preservatives can inhibit probiotic survival and elevated levels of ingredients such as salt, organic acids, and nitrates can inhibit probiotics during storage, while starter cultures can sometimes inhibit the growth of probiotics during fermentation through the production of specific bacteriocins.
[edit]Growth factors, protective, and synergistic ingredients
Probiotic lactobacilli and, in particular, bifidobacteria are only weakly proteolytic and grow relatively slowly or poorly in milk. The growth of bifidobacteria can be improved by the presence of suitable companion cultures, which can aid in protein hydrolysis and through the production of growth factors. Some growth substrates such as carbon sources, nitrogen sources, and growth factors or antioxidants, minerals, and vitamins can be added to improve growth. Finally, the food matrix itself can be protective like in the cheese, where the anaerobic environment, high fat content and buffering capacity of the matrix helps to protect the probiotic cells both in the product and during intestinal transit.
[edit]Freeze–thawing
The damages made to cell membranes by freezing probiotics is detrimental to survival, and also can make the cells more vulnerable to environmental stresses. To prevent or at least mitigate cell injury, protectants are usually added to cultures to be frozen or dried. Once frozen, probiotics can survive well over long shelf lives in products such as frozen yogurts and ice-cream. Using alternative methods of freezing, such as slow-cooling rates or pre-freezing stress, can significantly improve cell survival. Repeated freeze–thawing cycles are highly detrimental to cell survival and should be avoided.
[edit]Shear forces
Probiotic lactobacilli and bifidobacteria are Gram-positive bacteria with thick cell walls that are able to tolerate the shear forces generated in most standard food production processes such as high-speed blending or homogenization, that may result in cell disruption and losses in viability.[58]
[edit]Side effects
In some situations, such as where the person consuming probiotics is critically ill, probiotics could be harmful. In a therapeutic clinical trial conducted by the Dutch Pancreatitis Study Group, the consumption of a mixture of six probiotic bacteria increased the death rate of patients with predicted severe acute pancreatitis.[59]
In a clinical trial conducted at the University of Western Australia, aimed at showing the effectiveness of probiotics in reducing childhood allergies, researchers gave 178 children either a probiotic or a placebo for the first six months of their life. Those given the probiotic were more likely to develop a sensitivity to allergens.[60]
Some hospitals have reported treating lactobacillus septicaemia, which is a potentially fatal disease caused by the consumption of probiotics by people with lowered immune systems or who are already very ill.[60][61][unreliable medical source?]
There is no published evidence that probiotic supplements are able to replace the body's natural flora when these have been killed off; indeed bacterial levels in feces disappear within days when supplementation ceases.[62]
Probiotics taken orally can be destroyed by the acidic conditions of the stomach. A number of micro-encapsulation techniques are being developed to address this problem.[63]
Recent studies indicate that probiotic products such as yogurts could be a cause for obesity trends.[64] However, this is contested as the link to obesity, and other health related issues with yogurt may link to its dairy and calorie attributes.[65][66]
Some experts are skeptical on the efficacy of many strains and believe not all subjects will benefit from the use of probiotics.[67]
Strains
Live probiotic cultures are available in fermented dairy products and probiotic fortified foods. However, tablets, capsules, powders and sachets containing the bacteria in freeze dried form are also available.
In the table below, only preliminary evidence exists for the health claims stated. Few of the strains presented have been sufficiently developed in basic and clinical research to warrant application for health claim status to a regulatory agency such as the Food and Drug Administration orEuropean Food Safety Authority, but so far no claims have been approved.
Multi-probiotic
Preliminary research is evaluating the potential physiological effects of multiple probiotic strains, as opposed to a single strain.[100][101] As the human gut may contain several hundred microbe species, one theory indicates that this diverse environment may benefit from consuming multiple probiotic strains, an effect that remains scientifically unconfirmed.
