Probiotics have established their efficacy as dietary factors which can regulate gastrointestinal functions thereby imparting health benefits to consumers. Alleviation of lactose intolerance, prevention of different forms of diarrhea, cholesterol reduction, modulation of immune functions are some of the functions attributed to probiotics. Other benefits include prevention of cancer particularly colon carcinoma and food allergy. The competitive exclusion of pathogens and reduction in number and metabolic activities of harmful organisms on one side and increasing the number and activities of beneficial organisms on other in gastrointestinal tract are considered scientific basis of probiotic functions. Among different organisms considered as probiotics Lactobacillus (L. acidophilus, L. casei, L. rhamnosus, L. helveticus etc.), Bifidobacteria (B. longum, B. bifidum) are the most successful due to their long history of use in fermented foods. The efficiency of probiotic organisms could further be enhanced by modulation of diet in such a way by incorporating components which enhance the activity of probiotics in gastrointestinal tract. These components are known as prebiotics. Due to their structure, remain undigested in upper GI tract but are acted upon selectively by probiotic organisms in lower GI tract thereby providing favorable conditions for their growth. The foods containing probiotics and prebiotics are termed as synbiotic foods and are important part of functional foods. Such foods have been applied to various categories of persons such

as pregnant women and early infancy (Allen et al, 2010), Children (Guandalini et al 2010) and healthy adults (Sierra et al, 2010). Few applications of functional foods containing probiotics have been reported in elderly persons. As population ageing is considered a significant social issue particularly in developing countries like India where the number of people over 60 years of age is increasing. WHO estimates indicate that by 2020 over 1 billion persons will be in this group. With increasing health costs and changing pattern of society in India, maintaining a healthy elderly population in country will be a future challenge. Studies indicate that nutritional factors play important role not only in delaying normal ageing but also reducing the onset of age related diseases. Old age is associated with change in function of different organs and tissues including the gastrointestinal tract. Such changes lead to loss of bone mass, poor digestion and diminished immune function. The dietary intervention containing probiotics and prebiotics may provide ideal way to improve the age related complications but this aspect has not been adequately studied. Data available to date is mostly from experimental  animals or other age groups. Few studies related to role of dietary components like oligosaccharides (Schiffrin et al, 2007 and Vulevic et al, 2008) have been conducted and reported to improve immune functions and gastrointestinal health. Considering the importance of functional foods it is imperative to study their role in age related disorders. The investigation of immune functions such as NK cell activity, cytokine production and phagocytic activity coupled with monitoring overall health through placebo controlled randomized cross over feeding trial in selected subjects will provide insights into overall role of functional foods. The molecular analysis of microbial gut diversity and metagenomic study of the gastrointestinal microbiota and its activity as well as host genome will provide reliable data to draw a conclusion.