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Probiotics: Evidence-based guidelines



The term “probiotics” was first introduced in 1965 by Lilly and Stillwell; in contrast to antibiotics, probiotics were defined as microbially-derived factors that stimulate the growth of other organisms. In 1989, Roy Fuller emphasised the requirement of viability for probiotics and introduced the idea that they have a beneficial effect on the host.




Probiotics are live microbes that can be formulated into many different types of products, including foods, drugs, and dietary supplements. Species of  Lactobacillus and  Bifidobacterium are most commonly used as probiotics, but the yeast Saccharomyces cerevisiae and some  E. coli and Bacillus species are also used as probiotics. Lactic acid bacteria (LAB), including  Lactobacillus species, which have been used for preservation of food by fermentation for thousands of years, can serve a dual function by acting as agents for food fermentation and, in addition, potentially imparting health benefits. Strictly speaking, however, the term “probiotic” is reserved for live microbes that have been shown in controlled human studies to impart a health benefit.

Probiotic research suggests a range of potential health benefits. However, the effects described can only be attributed to the strain or strains tested, and not to the species or the whole group of LABs or other probiotics.

Probiotics are intended to assist the body’s naturally occurring gut microbiota. Some probiotic preparations have been used to prevent diarrhoea caused by antibiotics, or as part of the treatment for antibiotic-related dysbiosis. Studies have documented probiotic effects on a variety of gastrointestinal and extraintestinal disorders, including irritable bowel syndrome (IBS), vaginal infections, and immune enhancement. Some probiotics have also been investigated in relation to atopic eczema, rheumatoid arthritis, and liver cirrhosis.

In general, the strongest clinical evidence for probiotics is related to their use in improving gut health and stimulating immune function.

Probiotics affect the intestinal ecosystem by stimulating mucosal immune mechanisms and by stimulating nonimmune mechanisms through antagonism/competition with potential pathogens. These phenomena are thought to mediate most beneficial effects, including reduction of the incidence and severity of diarrhoea, which is one of the most widely recognised uses for probiotics. Probiotics reduce the risk of colon cancer in animal models, probably due to their role in suppressing the activity of certain bacterial enzymes that may increase the levels of procarcinogens, but this has not been proven in humans.

Well-designed, randomised clinical studies are still required in order to define the role of probiotics as therapeutic agents in inflammatory bowel disease.

The World Gastroenteroloy Organisation (WGO) Practice Guideline on the use of probiotics summarises the evidence for their use and outlines recommendations for clinical practice.


Cardiovascular disease

• The use of probiotics/prebiotics for preventative medicine and decreasing risk of cardiovascular disease is still unproven.

Colon cancer

• The SYNCAN study tested the effect of oligofructose plus two probiotic strains in patients at risk of developing colonic cancer. The results of the study suggest that a synbiotic preparation can decrease the expression of biomarkers for colorectal cancer.


• It has been confirmed that different probiotic strains, including L. casei DN-114 001, L. reuteri ATCC 55730, and L. rhamnosus GG are useful in reducing the severity and duration of acute infectious diarrhoea in children. The oral administration of probiotics shortens the duration of acute diarrhoeal illness in children by approximately one day.

• Several meta-analyses of controlled clinical trials have been published that show consistent results in systematic reviews, suggesting that probiotics are safe and effective. The evidence from studies on  viral gastroenteritis is more convincing than the evidence on bacterial or parasitic infections. Mechanisms of action are strain-specific: There is evidence for efficacy of some strains of lactobacilli (e.g., Lactobacillus casei GG and  Lactobacillus reuteri ATCC 55730) and for Saccharomyces boulardii. The timing of administration is also of importance.

Prevention of acute diarrhoea

• In the prevention of adult and childhood diarrhoea, there is evidence that  Lactobacillus GG, L. casei  DN-114 001, and  S. boulardii are effective in some specific settings

Antibiotic-associated diarrhoea

• Recent research has indicated that  L. casei DN-114 001 is effective in hospitalised adult patients for preventing antibiotic-associated diarrhoea and C. difficile diarrhoea.

H.Pylori infection

One study determined the efficacy of triple therapy supplemented with a specially designed fermented milk product containing the Lactobacillus casei DN-114 001 strain on Helicobacter pylori eradication in children. It discovered that milk containing L. casei DN-114 001 confers an enhanced therapeutic benefit on H. pylori eradication in children with gastritis on triple therapy.


• According to the WGO, a few well-designed studies have provided evidence that specific probiotic strains can be effective in the treatment of a subset of patients with atopic eczema; however, little is known about the efficacy of probiotics in preventing food allergy.



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