Recent progress in intestinal microbiota research has revealed that microbiota not only form stools but also act as a barrier from external disturbance factors such as pathogenic microorganisms. They also utilize food-derived components that humans cannot digest and absorb. In addition, they sometimes supply the host with beneficial metabolites, such as short-chain fatty acids and vitamins, as well as harmful metabolites, such as enteric rot products and secondary bile acids. Moreover, they have profound effects on human health: they stimulate the immune system and are associated with obesity; they are also intimately linked to various parts of the body such as the brain and kidney. Prebiotics are commonly described as food for the intestinal microbiota in the gut, especially those that contribute to the health of the host. In this article, I present prebiotics in general, including a prologue to prebiotics, the history of their definition, the main prebiotic materials, and their benefits to human health. I will also briefly touch on their expected development.

Probiotics have been widely utilized in foods for a long time, especially fermented foods, as live microorganisms conferring a health benefit on the host. Recent advances in the techniques of microbiota analysis have revealed that there are relations between gut microbiota and the pathogenesis of several diseases. Therefore, the use of probiotics is expanding from healthy individuals to the treatment of diseases. In this article, we review randomized controlled clinical trials which have evaluated the efficacy of probiotics on the health status of healthy subjects and patients suffering from immune-related, metabolic and neuropsychological diseases. There is not enough data showing the efficacy of probiotics on health through modification of gut microbiota. Introducing alternative ways to evaluate microbiota functions such as metagenome and metatranscriptome methods will be essential for the accumulation of evidence of relationships between the beneficial effects of probiotics and gut microbiota.