Probiotics:- The name probiotics means "for life" and is currently used to name bacteria associated with beneficial effects for humans and animals.

History:- In 1907, Metchnikoff - a Russian Scientist suggested that - The dependance of the intestinal microbes on the food makes it possible to adopt measures to modify the flora in our bodies and to replace the harmful microbes by useful microbes.At the same time Tissier (1906) a French pediatrician observed that children with diarrhea had in their stools a low number of bacteria characterized by a peculiar, Y shaped morphology which were abundant in healthy children and could be administered to patients with diarrhea to help restore a healthy gut flora.

The word probiotic was coined in 1960 to name substances which promoted the growth of other organisms. In the last 20 years, research in probiotic area has progressed considerably and significant advances have been made in the selection and characterization of specific probiotics.

Intestinal Flora:- In the GI tract more than 400 bacterial species are found and half of the wet weight of colonic material is due to bacterial cells whose numbers exceed by 10 fold the number of human tissue cells. Stomach contains least amount of bacteria. Gut colonization by bacteria starts from birth and continues through life. These bacteria prevent colonization by freshly ingested microorganisms including pathogens thus are beneficial bacteria. This has led to the assumption that increasing the relative number of beneficial bacteria could contribute to well being of host.

Action of probiotics in humans:- Probiotics should be able to remain viable at the target site and be effective in terms of their activity and growth that is beneficial to human body. The currently available tests are not adequate to predict the functionality of probiotic microorganism in the intestine.

Effect of probiotics in diarrhea:- The strongest evidence of a beneficial effect has been for the following probiotics - Lactobacillus rhamnosus GG and Bifidobacterium lactis BB-12 for both treatment and prevention of acute diarrhea caused mainly by rotavirus in children. There is also good invitro evidence that certain probiotic strains can inhibit the growth and adhesion of a range of enteropathogens.

Antibiotic associated diarrhea has also been found to respond when probiotics have been used as prophylaxis and also for therapy.

Other benefits of probiotics:- Though invitro and animal studies have demonstrated benefit of probiotics in bacterial diarrhea, H.pylori infection, enhancing immunity and decrease in allergies, more clinical studies in human adults and children are required before recommending use of probiotics in these conditions.

Adverse Effects:- Long term use of lactobacilli has not been associated with risk, increase virulence or bacteremia. However enterococci may possess virulence properties and thus not used as a probiotic in humans as they can display and confer cross resistance to vancomycin.

Difference from Prebiotics:- Prebiotics are non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or actiity of one or a limited number of bacterial species already established in the colon, and thus in effect improve host health.

Synbiotics are mixtures of probiotics and prebiotics that beneficially affect the host by improving the survival and implantation of live microbial dietary supplements in the GI tract of the host.

References:

	1.		Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties in Food including lower milk with Liver Lactic Acid Bacteria. Oct 2001
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