Probiotics ?pro life? are defined as dietary supplements of live bacteria or yeasts thought to be healthy for the host organism. According to the definition currently adopted by Food and Agriculture Organization of the United Nations &World Health Organization (FAO/WHO), probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host (FAO/WHO Expert Consultation, 2001). Prebiotics are a category of functional foods, defined as non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon and thus improve host health. Synbiotics refer to nutritional supplements combining probiotics and prebiotics to form a synbiotic relationship. Probiotics can be formulated into many different types of products, including foods, drugs, and dietary supplements. Most commonly used as probiotics are species of Lactobacillus and Bifidobacterium but there are a number of other probiotic genera such as Saccharomyces, Streptococcus, Enterococcus, and Bacillus. Lactic acid bacteria have been used for preservation of food by fermentation for thousands of years (World Gastroenterology Organisation (2008). There is a growing awareness of potential safety concerns such as gene transfer and isolation of probiotic bacteria from infection sites, and the pathogenicity, infectivity, toxicity and intrinsic properties of the bacteria may have to be studied more closely (Ishibashi &Yamazaki, 2007). However, to date there is no systematic review synthesizing the available evidence of symptomatic health outcomes in patients.
