Beneficial Effects of Inactive and Non-Viable Probiotics on Health

 According to the World Health Organization, viable probiotics could have health effects. However, in recent years, many benefits have been observed through application of inactive and non-viable cells of microbes or their metabolites. Therefore, probiotics could be defined as viable, inactive, or non-viable microbial cells or cell extracts that have beneficial health effects on the host. Based on the proposed terminology, probiotics are divided into three categories: real probiotics, pseudo-probiotics, and ghost probiotics. This article reviewed the beneficial effects and underlying mechanisms of inactive and non-viable microbial cells on the host. Also in this article, new proposed terms are described based on the nature of the cell or active ingredient so that it could cover all aspects of the microbial cell (viable, non-viable, inactive, and cell extract).