**4. Synbiotics**

Synbiotics are preparations containing a mixture of a probiotic and a prebiotic, or a combination of probiotics and prebiotics (Davis & Milner, 2009; Holzapfel & Schillinger, 2002; Touhy et al., 2003). These preparations aim to improve the viability of the proven probiotic *in vivo* as well as stimulate the indigenous gut microflora. They provide both the beneficial microbial culture and a specific substrate that can be readily available for fermentation by this culture (Gallaher & Khil, 1999). The presence of the readily fermentable substrate could enhance the survival of the probiotic. The prebiotic ingredient could also offer protection of probiotic against gastric acidity and proteolysis, probably through steric hindrance and coating of the probiotic.

Synbiotic supplements available include combinations of bifidobacteria and FOS, *Lactobacillus* GG and inulin and a combination of bifidobacteria lactobacilli with either FOS or inulin. Fermented milks contain both live beneficial bacteria and fermentation products that may positively stimulate the intestinal microflora also fall within this category. Crittenden et al. (2006) encapsulated a *B*. *infantis*-FOS synbiotic within a film-forming protein-carbohydrate-oil emulsion to improve its survival and viability during nonrefrigerated storage and GIT transit. Gallaher et al. (1996) observed a comparable synbiotic effect with oligofructose and bifidobacteria. Lactobacilli/lacitol, and bifidobacteria/GOS combinations have also been tried as synbiotics in addition to bifidobacteria/FOS (Mountzouris et al., 2002). A well-known benefit of synbiotics is that they increase the persistence of the probiotic in the GIT (Tuohy et al., 2003). The use of synbiotics has not been extensively explored, though studies indicated positive results with regard to maintenance of gut microflora (Shimizu et al., 2009). Their possible use for prevention of allergic diseases is just an example of the studies that still needs to be covered (Johannsen & Prescott, 2009).
