Prebiotics are food ingredients that trigger the production of useful bacteria. A common type of prebiotic are the nondigestible food parts that help stimulate the growth of beneficial bacteria in the intestines. Prebiotics have many functions. They improve digestion and facilitate the intake and absorption of essential minerals. Also, prebiotics strengthen the immune system. Perhaps the most important benefit of prebiotics is that they block and limit the growth of harmful, disease-causing bacteria. Most prebiotics can be obtained from plant-based carbohydrates and fiber-rich foods. Consult with a doctor to figure out the best way to incorporate prebiotics into the diet.