Probiotics are defined as nonpathogenic, living microorganisms that have beneficial effects on disease prevention and/or treatment when administered in appropriate amounts. Multiple studies have reported that probiotics have beneficial effects on gastrointestinal infections, improve lactose metabolism, reduce serum cholesterol, stimulate the immune system, improve symptoms of inflammatory bowel disease, and suppress Helicobacter pylori infection when selected strains are used. Data obtained from several studies indicated that probiotics have anti-mutagenic, anti-carcinogenic and anti-diarrheal properties. This review focuses on recent significant research findings regarding probiotic actions that promote host homeostasis and have an impact on the treatment of different disease processes.