Probiotics as functional food: microbiological and medical aspects

Probiotic bacteria are sold mainly in fermented foods, and dairy products play a predominant role as carriers of probiotics. Functional dairy foods are well suited to promoting the positive health image of probiotics for several reasons: (i) fermented foods and dairy products in particular, already have a positive health image by their traditional use for centuries; (ii) people are familiar with the fact that fermented food contain living microorganisms; (iii) probiotics are used as starter to join together the positive images of fermentation and probiotic cultures. Probiotics are defi ned as live bacterial preparations (food or medicine) with clinically documented health eff ects in humans. Most probiotics exert benefi cial eff ects by modulating the mucosal barrier function and immune activity. Probiotics have specifi c properties and targets in the human intestinal tract and intestinal microbiota. Understanding the mechanisms by which probiotics infl uence the normal intestinal microfl ora and counteract aberrancies in microfl ora can facilitate the use of probiotics for dietary management and reduction in risk of specifi c diseases. In reference of the immune system, many studies have pointed out that not only proand prebiotics, but also single micronutrients incorporated into functional foods contribute to an enhancement of immunocompetence. In this article, the eff ect of some functional foods and ingredients such as probiotics and selenium on health and especially immune function are reviewed.