According to the US FDA definition, probiotics are classified as Live Biotherapeutic Products (LBP) i.e. products that contain live organisms such as bacteria or yeast, found naturally in humans. The most common bacteria belong to the groups Lactobacillus and Bifidobacterium. Probiotics have a long global history of traditional use. Normally consumed through fermented foods and sold mostly as ingredients in foods or nutritional supplements. There is a thin line between nutritional supplements and drugs.