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Probiotics are dietary supplements containing potentially beneficial bacteria or yeast, with lactic acid bacteria (LAB) as the most common microbes used. LAB have been used in the food industry for many years, because they are able to convert sugars (including lactose) and other carbohydrates into lactic acid. This not only provides the characteristic sour taste of fermented dairy foods such as yogurt, but acts as a preservative, by lowering the pH and creating fewer opportunities for spoilage organisms to grow.

Probiotic bacterial cultures are intended to assist the body's naturally occurring gut flora to reestablish themselves. They are sometimes recommended by doctors, and, more frequently, by nutritionists, after a course of antibiotics, or as part of the treatment for gut related candidiasis. Claims are made that probiotics strengthen the immune system. [1]

The rationale for probiotics is that the body contains a miniature ecology of microbes, collectively known as the gut flora. A number of bacterial types are thought to be thrown out of balance by a wide range of circumstances including the use of antibiotics or other drugs, excess alcohol, stress, disease, or exposure to toxic substances. In cases like these, the bacteria that work well with our bodies (see symbiosis) may decrease in number, an event which allows harmful competitors to thrive, to the detriment of our health.

Maintenance of a healthy gut flora is, however, dependent on many factors, especially the quality of food intake. Including a significant proportion of prebiotic foods in the diet has been demonstrated to support a healthy gut flora and may be another means of achieving the desirable health benefits promised by probiotics.
Contents
[hide]

* 1 Effects
o 1.1 Side effects
* 2 Potential benefits
o 2.1 Managing Lactose Intolerance
o 2.2 Prevention of Colon Cancer
o 2.3 Cholesterol Lowering
o 2.4 Lowering Blood Pressure
o 2.5 Improving Immune Function and Preventing Infections
+ 2.5.1 Helicobacter pylori
+ 2.5.2 Antibiotic-associated diarrhea
o 2.6 Reducing Inflammation
o 2.7 Improving Mineral Absorption
o 2.8 Prevents Harmful Bacterial Growth Under Stress
o 2.9 Irritable Bowel Syndrome and Colitis
* 3 Synbiotics
* 4 Types
* 5 Research
o 5.1 Criticism
* 6 References
* 7 See also
* 8 External links

[edit] Effects

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[2]. It is hoped, however, that probiotics do form beneficial temporary colonies which may assist the body in the same functions as the natural flora, while allowing the natural flora time to recover from depletion. The probiotic strains are then thought to be progressively replaced by a naturally developed gut flora. Hence, probiotics have been defined as correctives of the ecoorgan. If the conditions which originally caused damage to the natural gut flora persist, the benefits obtained from probiotic supplements will be short lived.

[edit] Side effects

Treatment with probiotics, like any medicine, may include a condition called excessive drainage syndrome, which includes headache, diarrhea, bloating, or constipation[citation needed]. Another commonly reported side effect is intestinal gas. To reduce the side effects it is recommended to lower the supplement dosage, or pretreat with colon hydrotherapy, or stool softeners and fiber as tolerated or advised by a healthcare professional..[citation needed] [verification needed]

[edit] Potential benefits

Experiments into the benefits of probiotic therapies suggest a range of potentially beneficial medicinal uses for probiotics. For many of the potential benefits, research is limited and only preliminary results are available.

[edit] Managing Lactose Intolerance

Because LAB convert lactose into lactic acid, their ingestion may help lactose intolerant individuals tolerate more lactose than what they would have otherwise.[1]

[edit] Prevention of Colon Cancer

In laboratory investigations, LAB have demonstrated anti-mutagenic effects thought to be due to their ability to bind with heterocyclic amines; carcinogenic substances formed in cooked meat.[3] Animal studies have demonstrated that LAB can protect against colon cancer in rodents, though human data is limited and conflicting.[4] Most human trials have found that LAB may exert anti-carcinogenic effects by decreasing the activity of an enzyme called ß-glucuronidase[4] (which can generate carcinogens in the digestive system). Lower rates of colon cancer among higher consumers of fermented dairy products have been observed in some population studies.[1]

[edit] Cholesterol Lowering

Animal studies have demonstrated the efficacy of a range of LAB to be able to lower serum cholesterol levels, presumably by breaking down bile in the gut, thus inhibiting its reabsorption (which enters the blood as cholesterol).Some, but not all human trials have shown that dairy foods fermented with LAB can produce modest reductions in total and LDL cholesterol levels in those with normal levels to begin with, however trials in hyperlipidemic subjects are needed.[1]

[edit] Lowering Blood Pressure

Several small clinical trials have shown that consumption of milk fermented with various strains of LAB can result in modest reductions in blood pressure. It is thought that this is due to the ACE inhibitor-like peptides produced during fermentation.[1]

[edit] Improving Immune Function and Preventing Infections

LAB are thought to have several presumably beneficial effects on immune function. They may protect against 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.[5][6] Clinical trials have demonstrated that probiotics may decrease the incidence of respiratory tract infections[7] and dental caries in children[8] LAB foods and supplements have been shown to be effective in the treatment and prevention of acute diarrhea; decreasing the severity and duration of rotavirus infections in children as well as travelers diarrhea in adults.[5][6]

[edit] Helicobacter pylori

as well as aid in the treatment of Helicobacter pylori infections (which cause peptic ulcers) in adults when used in combination with standard medical treatments.[9]

[edit] Antibiotic-associated diarrhea

A meta-analysis suggested probiotics may reduce antibiotic-associated diarrhea. [10] A subsequent randomized controlled trail also found benefit in elderly patients. [11]

[edit] Reducing Inflammation

LAB foods and supplements have been found to modulate inflammatory and hypersensitivity responses, an observation thought to be at least in part due to the regulation of cytokine function.[5] Clinical studies suggest that they can prevent reoccurrences of inflammatory bowel disease in adults,[5] as well as improve milk allergies[12] and decrease the risk of atopic eczema in children.[13]

[edit] Improving Mineral Absorption

It is hypothesized that probiotic lactobacilli may help correct malabsorption of trace minerals, found particularly in those with diets high in phytate content from whole grains, nuts, and legumes.[14]

[edit] Prevents Harmful 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.[15]

[edit] Irritable Bowel Syndrome and Colitis

B. infantis 35624, sold as Align, was found to improve some symptoms of irritable bowel syndrome in women in a recent study.[16] Another probiotic bacterium, Lactobacillus plantarum 299V, was also found to be effective in reducing IBS symptoms. [17] Additionally, a probiotic formulation, VSL3, was found to be effective in treating ulcerative colitis [18] Bifidobacterium animalis DN-173 010 may help. [19]


[edit] Synbiotics

It is also possible to increase and maintain a healthy bacterial gut flora by increasing the amounts of prebiotics in the diet such as inulin, raw oats, and unrefined wheat .[citation needed]

As probiotics are mainly active in the small intestine and prebiotics are only effective in the large intestine [20], the combination of the two may give a synergistic effect. Appropriate combinations of pre- and probiotics are synbiotics.

Synbiotics have also been defined as metabolites produced by ecoorgan or by synergistic action of prebiotics and probiotics e.g. short chain fatty acids, other fatty acids, amino acids, peptides, polyamines, carbohydrates, vitamins, numerous antioxidants and phytosterols, growth factors, coagulation factors, various signal molecules such as cytokine-like bacteriokines.

[edit] Types

The most common form for probiotics are dairy products and probiotic fortified foods. However, tablets and capsules containing the bacteria in freeze dried form are also available.

Some common probiotics include various species of the genera Bifidobacterium and Lactobacillus such as:

* Bifidobacterium
o Bifidobacterium animalis
+ Bifidobacterium animalis subsp animalis (B. animalis)
+ Bifidobacterium animalis subsp lactis (B. lactis)
o Bifidobacterium bifidum
o Bifidobacterium breve
o Bifidobacterium infantis
o Bifidobacterium longum
* Lactobacillus
o Lactobacillus acidophilus
o Lactobacillus casei
o Lactobacillus plantarum
o Lactobacillus reuteri
o Lactobacillus rhamnosus (including Lactobacillus GG)

There is currently only one species of yeast used as a probiotic:

* Saccharomyces boulardii

Some commonly used bacteria in products, but without probiotic effect (yogurt bacteria):

* Lactobacillus bulgaricus
* Streptococcus thermophilus

Some other bacteria mentioned in probiotic products:

* Bacillus coagulans
* Lactobacillus bifidus - became new genus Bifidobacterium
* Lactobacillus caucasicus, a fantasy name, as no species with this name exists.

Some fermented products containing similar (often not proven to have a probiotic or health effect) lactic acid bacteria include:

* Kefir
* Yogurt
* Sauerkraut
* Kimchi
* Kombucha

[edit] Research

A 2007 study at University College Cork in Ireland showed that a diet including milk fermented with Lactobacillus bacteria prevented Salmonella infection in pigs.[21]

A 2007 clinical study at Imperial College London showed that consumption of a probiotic drink containing L casei, L bulgaricus, and S thermophilus can reduce the incidence of antibiotic associated diarrhoea and C difficile associated diarrhoea.[11]

[edit] Criticism

Some mainstream researchers in Europe as well as in the United States are skeptical of some of the claims made for probiotics. Their reasons include the following considerations[22]:

* The studies done in support of probiotics are mostly anecdotal or heavily reliant on test-tube experimentation rather than on clinical trials in human subjects
* The basic concept of probiotics is based on a misunderstanding of the role of microflora in the human digestive tract.
* It is difficult to see how bacteria taken by mouth can survive the process of human digestion (though research shows that they do, in fact, survive [23])