The word "probiotic" is a compound of two Greek words: "pro," to signify promotion of and "biotic," which means life. The World Health Organization defines a probiotic as any living microorganism that has a health benefit when ingested. Similarly, the USDA defines a probiotic as "any viable microbial dietary supplement that beneficially affects the host."
One of the main functions of Probiotics is to stimulate immune response, 80 percent of your immune system is located in your digestive system. Remember, a robust immune system is your number one defense system against all disease. Probiotic strength and potency is measured in CFUs or colony-forming units, a microbiological term that describes the density of viable bacteria in a product. In other words, the CFU tells you how rich in probiotics a supplement is and how much will be available to your body.