Probiotics and the ageing gut

Abstract

Probiotic food and supplements are very popular particularly in an ageing population. There usage has principally been confined to gastrointestinal (GI) related conditions. However, "live probiotics" are now being used to alleviate infection and diseases in many areas of the human body. It is well acknowledged that there is a growing body of evidence to support the fact that the complex and vast microflora inside our gastrointestinal tract (GIT) contributes to health and disease.1 For this micoflora to function optimally in the adult gut, the "balance" of the microflora must be maintained and this appears to be increasingly difficult because of lifestyle changes and the problems associated with human ageing. Various factors (e.g. diet, antibiotic treatment, stress, age) may "shift" the balance of the gut microflora away from potentially beneficial or health-promoting bacteria (e.g. Lactobacilli and Bifidobacteria) towards a predominance of potentially harmful or pathogenic bacteria such as Clostridia, sulfate-reducers, and certain Bacteroides species.2 Predominance of these latter populations are known to predispose an individual to a number of clinical conditions such as cancer and inflammatory disorders while making the host more susceptible to infections by transient enteropathogens such as Salmonella, Escherichia coli, and Listeria.3 Consequently, people are seeking healthier lifestyles, and evidence is mounting that supports the idea that our health can be affected by the daily consumption of specific bacteria such as "probiotics." Probiotic is derived from Greek and means "for life." Fuller defined probiotics as "live microbial feed supplements which beneficially affect the host by improving the intestinal microbial balance."4 However, a later definition by the Food and Agricultural Organization of the United Nations and the World Health Organization to provide health benefits 5 proposed probiotics as "live microorganisms which when administered in adequate amounts confer a health benefit on the host."6 A probiotic is considered as a food or supplement containing viable microorganisms that on ingestion affect the host in a beneficial manner by modulating mucosal and systemic immunity as well as improving nutritional and microbial balance in the intestinal tract.7 Health benefits associated with the consumption of probiotic bacteria include modulation of immune function, protection against enteric infections and immunoinflammatory disorders, anti-tumorigenic effects, alleviation of lactose intolerance, and blood cholesterol reduction.8,9. © Springer Science+Business Media, LLC 2009. All rights reserved.